Machines

15 pages, 5715 KiB

Open AccessArticle

Investigation on Temperature Rise Characteristic and Load Capacity of Amorphous Alloy Vegetable Oil Distribution Transformers with 3D Coupled-Field Method

by Jing Guo, Kaiyuan Fan, Bowen Yang, Hang Yang, Qingjun Peng and Hanbo Zheng

Machines 2022, 10(1), 67; https://doi.org/10.3390/machines10010067 - 17 Jan 2022

Cited by 3 | Viewed by 3050

Abstract

The large differences in the load peak and valley of rural distribution networks always bring severe problems to system planners and operators. Given this issue, this paper deals with the hot-spot temperature (HST) of the transformer and its overload capability, and proposes a [...] Read more.

The large differences in the load peak and valley of rural distribution networks always bring severe problems to system planners and operators. Given this issue, this paper deals with the hot-spot temperature (HST) of the transformer and its overload capability, and proposes a modeling method-based online monitoring of practical parameters. In the current work, a temperature-fluid coupling field of the 315 kVA vegetable oil distribution transformer is developed in both the two-dimensional and three-dimensional geometry, by which the convection and heat dissipation process can be studied. The grid of the model is divided into regions to increase the calculation speed and ensure the accuracy of the calculation. Secondly, tests related to the temperature rise of the transformer are carried out. The accuracy of the three-dimensional model is later discussed in terms of temperature and fluid velocity distribution. Finally, the temperature distribution laws of the amorphous alloy vegetable oil distribution transformers (AVDT) are compared and analyzed under different load conditions. Findings reveal that the AVDT has low no-load loss and strong overload capacity, which is capable of reducing the internal overheating accidents of the transformer. Full article

(This article belongs to the Special Issue Advanced Control Theory with Applications in Intelligent Machines)

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18 pages, 7070 KiB

Open AccessArticle

Nonlinear Adaptive Control with Asymmetric Pressure Difference Compensation of a Hydraulic Pressure Servo System Using Two High Speed On/Off Valves

by Qiang Gao

Machines 2022, 10(1), 66; https://doi.org/10.3390/machines10010066 - 17 Jan 2022

Cited by 14 | Viewed by 2973

Abstract

A hydraulic pressure servo system based on two high-speed on/off valves (HSV) is a discontinuous system due to the discrete flow of HSV when driven by pulse width modulation (PWM) signal. Pressure variation in the testing chamber is determined by the flow rate [...] Read more.

A hydraulic pressure servo system based on two high-speed on/off valves (HSV) is a discontinuous system due to the discrete flow of HSV when driven by pulse width modulation (PWM) signal. Pressure variation in the testing chamber is determined by the flow rate difference between the charging and discharging HSV. In this paper, a pressure controller consisting of a differential PWM (DPWM) scheme, asymmetric pressure difference compensation (APDC) and nonlinear adaptive control (NAC) is proposed to precisely control the pressure. The DPWM scheme is designed to improve the resolution of the net flow rate into the testing chamber. Furthermore, due to the strong asymmetry between the charging and the discharging process, the APDC method is proposed to design the two initial duty cycles of the DPWM signal which help to balance its charging and discharging ability under different working pressure points. Since the pressure system is a nonlinear, uncertain system due to oil compression and leakage, the NAC is designed to calculate the control duty cycle of the DPWM signal, which is used to overcome the unmodeled dynamic and parameter uncertainties. Comparative experiments indicate that the proposed controller can ensure good pressure tracking performance and enhance system robustness under different working pressure points and tracking frequencies. Full article

(This article belongs to the Special Issue Advanced Control of Industrial Electro-Hydraulic Systems)

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19 pages, 7580 KiB

Open AccessArticle

The Effect of Inflow Distortion on the Rotordynamic Characteristics of a 1400-MW Reactor Coolant Pump Annular Seal

by Lusheng Zhou, Xiaofang Wang, Haitao Liu and Jianchi Xin

Machines 2022, 10(1), 65; https://doi.org/10.3390/machines10010065 - 17 Jan 2022

Cited by 1 | Viewed by 2096

Abstract

The annular seal between stator and rotor substantively acts as a bearing that affects the rotordynamic characteristic of the turbomachinery rotor system. The rotor wake turbulence in a canned motor Reactor Coolant Pump (RCP) will lead to inflow pressure distortion at the annular [...] Read more.

The annular seal between stator and rotor substantively acts as a bearing that affects the rotordynamic characteristic of the turbomachinery rotor system. The rotor wake turbulence in a canned motor Reactor Coolant Pump (RCP) will lead to inflow pressure distortion at the annular seal entrance, thus further affecting the seal rotordynamic characteristics and threatening the stable operation of RCP. In order to obtain the seal rotordynamic coefficients, a transient numerical method applies the mesh deformation technique to simulate the multiple-frequency elliptical rotor whirling orbit model. The transient solutions were proposed to solve the unsteady reaction forces of annular seals at five excitation frequencies for each case. The inflow pressure distortion patterns were simplified as harmonic functions, including two important influence parameters that are impeller blades number m and pressure fluctuation ratio

λ

. The numerical results showed that with nonuniform time-averaged pressure distribution at the entrance of the annular seal in Case 2, the inflow distortion significantly affects the seal rotordynamic coefficients, while the rotational spinning speed in Case 3 can weaken the time-averaged nonuniformity and accordingly make a dent in the influence. Increasing impeller blades number m and pressure fluctuation

λ

both result in a sharp diminution of the negative stiffness

K_{e f f}

, as well as an obvious increase in the effective damping

C_{e f f}

, which will strengthen rotor misalignment and system stability. In addition, the larger impeller blades number m and higher pressure fluctuation

λ

will make the effective damping

C_{e f f}

more independent of the whirling frequency. These results provide theoretical guidance for the operation safety of RCP. Full article

(This article belongs to the Section Turbomachinery)

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19 pages, 2782 KiB

Open AccessArticle

Modified Whale Optimization Algorithm for Multi-Type Combine Harvesters Scheduling

by Wenqiang Yang, Zhile Yang, Yonggang Chen and Zhanlei Peng

Machines 2022, 10(1), 64; https://doi.org/10.3390/machines10010064 - 17 Jan 2022

Cited by 6 | Viewed by 2268

Abstract

The optimal scheduling of multi-type combine harvesters is a crucial topic in improving the operating efficiency of combine harvesters. Due to the NP-hard property of this problem, developing appropriate optimization approaches is an intractable task. The multi-type combine harvesters scheduling problem considered in [...] Read more.

The optimal scheduling of multi-type combine harvesters is a crucial topic in improving the operating efficiency of combine harvesters. Due to the NP-hard property of this problem, developing appropriate optimization approaches is an intractable task. The multi-type combine harvesters scheduling problem considered in this paper deals with the question of how a given set of harvesting tasks should be assigned to each combine harvester, such that the total cost is comprehensively minimized. In this paper, a novel multi-type combine harvesters scheduling problem is first formulated as a constrained optimization problem. Then, a whale optimization algorithm (WOA) including an opposition-based learning search operator, adaptive convergence factor and heuristic mutation, namely, MWOA, is proposed and evaluated based on benchmark functions and comprehensive computational studies. Finally, the proposed intelligent approach is used to solve the multi-type combine harvesters scheduling problem. The experimental results prove the superiority of the MWOA in terms of solution quality and convergence speed both in the benchmark test and for solving the complex multi-type combine harvester scheduling problem. Full article

(This article belongs to the Topic Motion Planning and Control for Robotics)

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15 pages, 7291 KiB

Open AccessArticle

Bayesian Regularization Algorithm Based Recurrent Neural Network Method and NSGA-II for the Optimal Design of the Reflector

by Xinyong Zhang, Liwei Sun and Lingtong Qi

Machines 2022, 10(1), 63; https://doi.org/10.3390/machines10010063 - 15 Jan 2022

Cited by 4 | Viewed by 2379

Abstract

The optical-mechanical system of a space camera is composed of several complex components, and the effects of several factors (weight, gravity, modal frequency, temperature, etc.) on its system performance need to be considered during ground tests, launch, and in-orbit operation. In order to [...] Read more.

The optical-mechanical system of a space camera is composed of several complex components, and the effects of several factors (weight, gravity, modal frequency, temperature, etc.) on its system performance need to be considered during ground tests, launch, and in-orbit operation. In order to meet the system specifications of the optical camera system, the dimensional parameters of the optical camera structure need to be optimized. There is a highly nonlinear functional relationship between the dimensional parameters of the optical machine structure and the design indexes. The traditional method takes a significant amount of time for finite element calculation and is less efficient. In order to improve the optimization efficiency, a recurrent neural network prediction model based on the Bayesian regularization algorithm is proposed in this paper, and the NSGA-II is used to globally optimize multiple prediction objectives of the prediction model. The reflector of the space camera is used as an example to predict the weight, first-order modal frequency, and gravitational mirror deformation root mean square of the reflector, and to complete the lightweight design. The results show that the prediction model established by BR-RNN-NSGA-II offers high prediction accuracy for the design indexes of the reflector, which all reach over 99.6%, and BR-RNN-NSGA-II can complete the multi-objective optimization search efficiently and accurately. This paper provides a new idea of optimization of optical machine structure, which enriches the theory of complex structure design. Full article

(This article belongs to the Special Issue Precision Measurement and Machines)

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22 pages, 2268 KiB

Open AccessReview

A Review of Recent Research and Application Progress in Screw Machines

by Chuang Wang, Bingqi Wang, Mingkun Liu and Ziwen Xing

Machines 2022, 10(1), 62; https://doi.org/10.3390/machines10010062 - 14 Jan 2022

Cited by 7 | Viewed by 4185

Abstract

Screw machines, mainly including single-screw type and twin-screw type, have gone through significant development and improvement during the past decade. This paper reviews the relevant studies available in the open literature for acquiring insight into and to establish the state of the art [...] Read more.

Screw machines, mainly including single-screw type and twin-screw type, have gone through significant development and improvement during the past decade. This paper reviews the relevant studies available in the open literature for acquiring insight into and to establish the state of the art of the research and application status of screw machines. The related research on different aspects, which would affect the performance and reliability of screw machines includes rotor profile and geometric characteristics, thermodynamic modelling, vibration and noise, lubrication and wear, control of capacity and built-in volume ratio, and liquid injection technology. In the aspect of thermodynamic modelling, the available methods, i.e., empirical or semi-empirical model, lump model, and 3D CFD model, adopted for the performance prediction and optimal design of screw machines are summarized. Then, the review covers the application status of screw machines in the fields of air compression and expansion, refrigeration and heat pump, organic Rankine cycle (ORC), and other popular applications, with an emphasis on the reported performance and progress in technologies of screw machines. Finally, conclusions and perspectives for future research in the area of screw machines are presented. The review provides readers with a good understanding of the research focus and progress in the field of screw machines. Full article

(This article belongs to the Special Issue Advances in Positive Displacement Compressors)

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16 pages, 10776 KiB

Open AccessArticle

Effect of Blade Thickness on Internal Flow and Performance of a Plastic Centrifugal Pump

by Zhenfa Xu, Fanyu Kong, Lingfeng Tang, Mingwei Liu, Jiaqiong Wang and Ning Qiu

Machines 2022, 10(1), 61; https://doi.org/10.3390/machines10010061 - 14 Jan 2022

Cited by 8 | Viewed by 6659

Abstract

Blade thickness is an essential parameter of the impeller, which has significant effects on the pump performance. The plastic pump generally adopts thick blade due to low strength of plastic. The effects of blade thickness on the internal flow and performance of a [...] Read more.

Blade thickness is an essential parameter of the impeller, which has significant effects on the pump performance. The plastic pump generally adopts thick blade due to low strength of plastic. The effects of blade thickness on the internal flow and performance of a plastic centrifugal pump were discussed based on the numerical methods. Two kinds of blade profile, the constant thickness blade (CTB) and the variable thickness blade (VTB), were investigated. The results indicated that, for the CTB, when the blade thickness was less than 6 mm, the pump performance did not change significantly. When the blade thickness exceeded 6 mm, the pump head and efficiency decreased rapidly. The pump head and efficiency of CTB 10 decreased by 42.2% and 30% compared with CTB 4, respectively. For the VTB, with blade thickness in a certain range (6 mm–14 mm), the pump performance changed slightly with the increased of trailing edge thickness. The minimum blade thickness of the plastic centrifugal pump should be 4 mm based on the finite element analysis. A variable thickness blade (VTB 4-8-4) with the maximum thickness located at 60% chord length was proposed to improve the pump performance, and its efficiency was 1.67% higher than that of the CTB 4 impeller. Full article

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21 pages, 17832 KiB

Open AccessArticle

Design and Optimization of High-Pressure Water Jet for Coal Breaking and Punching Nozzle Considering Structural Parameter Interaction

by Lihuan Chen, Muzheng Cheng, Yi Cai, Liwen Guo and Dianrong Gao

Machines 2022, 10(1), 60; https://doi.org/10.3390/machines10010060 - 14 Jan 2022

Cited by 8 | Viewed by 2599

Abstract

The technology of increasing coal seam permeability by high-pressure water jet has significant advantages in preventing and controlling gas disasters in low-permeability coal seam. The structural parameters of a nozzle are the key to its jet performance. The majority of the current studies [...] Read more.

The technology of increasing coal seam permeability by high-pressure water jet has significant advantages in preventing and controlling gas disasters in low-permeability coal seam. The structural parameters of a nozzle are the key to its jet performance. The majority of the current studies take strike velocity as the evaluation index, and the influence of the interaction between the nozzle’s structural parameters on its jet performance is not fully considered. In practice, strike velocity and strike area will affect gas release in the process of coal breaking and punching. To further optimize the structural parameters of coal breaking and punching nozzle, and improve water jet performance, some crucial parameters such as the contraction angle, outlet divergence angle, and length-to-diameter ratio are selected. Meanwhile, the maximum X-axis velocity and effective Y-axis extension distance are used as evaluation indexes. The effect of each key factor on the water jet performance is analyzed by numerical simulation using the single factor method. The significance and importance effect of each factor and their interaction on the water jet performance are quantitatively analyzed using the orthogonal experiment method. Moreover, three optimal combinations are selected for experimental verification. Results show that with an increase in contraction angle, outlet divergence angle, and length-to-diameter ratio, the maximum X-axis velocity increases initially and decreases thereafter. The Y-direction expansion distance of the jet will be improved significantly with an increase in the outlet divergence angle. Through field experiments, the jet performance of the improved nozzle 3 is the best. After optimization, the coal breaking and punching diameter of the nozzle is increased by 118%, and the punching depth is increased by 17.46%. Full article

(This article belongs to the Special Issue Optimization and Flow Characteristics in Advanced Fluid Machinery)

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21 pages, 1057 KiB

Open AccessArticle

Impact of Condensation on the System Performance of a Fuel Cell Turbocharger

by Sebastian Lück, Tim Wittmann, Jan Göing, Christoph Bode and Jens Friedrichs

Machines 2022, 10(1), 59; https://doi.org/10.3390/machines10010059 - 13 Jan 2022

Cited by 3 | Viewed by 2251

Abstract

A mobile fuel cell systems power output can be increased by pressure amplification using an electric turbocharger. These devices are subject to frequent transient manoeuvres due to a multitude of load changes during the mission in automotive applications. In this paper, the authors [...] Read more.

A mobile fuel cell systems power output can be increased by pressure amplification using an electric turbocharger. These devices are subject to frequent transient manoeuvres due to a multitude of load changes during the mission in automotive applications. In this paper, the authors describe a simulation approach for an electric turbocharger, considering the impact of moist air and condensation within the cathode gas supply system. Therefore, two simulation approaches are used: an iterative simulation method and one based on a set of ordinary differential equations. Additional information is included from turbine performance maps taking into account condensation using Euler–Lagrange CFD simulations, which are presented. The iterative calculation approach is well suited to show the impact of condensation and moist air on the steady state thermodynamic cycle and yields a significant shift of the steady state operating line towards the surge line. It is shown that a substantial risk of surge occurs during transient deceleration manoeuvres triggered by a load step. Full article

(This article belongs to the Special Issue High Speed Air Compressor for a Fuel Cell System for Use in a Vehicle)

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16 pages, 7504 KiB

Open AccessArticle

Role of Cyclic Thermal Shocks on the Physical and Mechanical Responses of White Marble

by Yujie Feng, Haijian Su, Yinjiang Nie and Honghui Zhao

Machines 2022, 10(1), 58; https://doi.org/10.3390/machines10010058 - 13 Jan 2022

Cited by 5 | Viewed by 1580

Abstract

Marble is a common rock used in many buildings for structural or ornamental purposes and is widely distributed in underground engineering projects. The rocks are exposed to high temperatures when a tunnel fire occurs, and they will be rapidly cooled during the rescue [...] Read more.

Marble is a common rock used in many buildings for structural or ornamental purposes and is widely distributed in underground engineering projects. The rocks are exposed to high temperatures when a tunnel fire occurs, and they will be rapidly cooled during the rescue process, which has a great impact on the rock performance and the underground engineering stability. Therefore, the role of cyclic thermal shocks on the physical and mechanical properties of marble specimens was systematically investigated. Different cyclic thermal shock treatments (T = 25, 200, 400, 600, 800 °C; N = 1, 3, 5, 7, 9) were applied to marble specimens and the changes in mass, volume, density and P-wave velocity were recorded in turn. Then, the thermal conductivity, optical microscopy and uniaxial compression tests were carried out. The results showed that both the cyclic thermal shock numbers (N) and the temperature level (T) weaken the rock properties. When the temperature of a thermal shock exceeds 600 °C, the mass loss coefficient and porosity of the marble will increase significantly. The most noticeable change in P-wave velocity occurs between 200 and 400 °C, with a 52.98% attenuation. After three thermal shocks, the cyclic thermal shock numbers have little influence on the uniaxial compressive strength and Young’s modulus of marble specimens. Shear failure is the principal failure mode in marble specimens that have experienced severe thermal damage (high N or T). The optical microscopic pictures are beneficial for illustrating the thermal cracking mechanism of marble specimens after cyclic thermal shocks. Full article

(This article belongs to the Special Issue Advances in Fracture Mechanics for Structural Integrity Assessment)

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16 pages, 9947 KiB

Open AccessEditor’s ChoiceArticle

Design of a 3D-Printed Hand Exoskeleton Based on Force-Myography Control for Assistance and Rehabilitation

by Daniele Esposito, Jessica Centracchio, Emilio Andreozzi, Sergio Savino, Gaetano D. Gargiulo, Ganesh R. Naik and Paolo Bifulco

Machines 2022, 10(1), 57; https://doi.org/10.3390/machines10010057 - 13 Jan 2022

Cited by 26 | Viewed by 6857

Abstract

Voluntary hand movements are usually impaired after a cerebral stroke, affecting millions of people per year worldwide. Recently, the use of hand exoskeletons for assistance and motor rehabilitation has become increasingly widespread. This study presents a novel hand exoskeleton, designed to be low [...] Read more.

Voluntary hand movements are usually impaired after a cerebral stroke, affecting millions of people per year worldwide. Recently, the use of hand exoskeletons for assistance and motor rehabilitation has become increasingly widespread. This study presents a novel hand exoskeleton, designed to be low cost, wearable, easily adaptable and suitable for home use. Most of the components of the exoskeleton are 3D printed, allowing for easy replication, customization and maintenance at a low cost. A strongly underactuated mechanical system allows one to synergically move the four fingers by means of a single actuator through a rigid transmission, while the thumb is kept in an adduction or abduction position. The exoskeleton’s ability to extend a typical hypertonic paretic hand of stroke patients was firstly tested using the SimScape Multibody simulation environment; this helped in the choice of a proper electric actuator. Force-myography was used instead of the standard electromyography to voluntarily control the exoskeleton with more simplicity. The user can activate the flexion/extension of the exoskeleton by a weak contraction of two antagonist muscles. A symmetrical master–slave motion strategy (i.e., the paretic hand motion is activated by the healthy hand) is also available for patients with severe muscle atrophy. An inexpensive microcontroller board was used to implement the electronic control of the exoskeleton and provide feedback to the user. The entire exoskeleton including batteries can be worn on the patient’s arm. The ability to provide a fluid and safe grip, like that of a healthy hand, was verified through kinematic analyses obtained by processing high-framerate videos. The trajectories described by the phalanges of the natural and the exoskeleton finger were compared by means of cross-correlation coefficients; a similarity of about 80% was found. The time required for both closing and opening of the hand exoskeleton was about 0.9 s. A rigid cylindric handlebar containing a load cell measured an average power grasp force of 94.61 N, enough to assist the user in performing most of the activities of daily living. The exoskeleton can be used as an aid and to promote motor function recovery during patient’s neurorehabilitation therapy. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate the First Impact Factor of Machines)

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20 pages, 43748 KiB

Open AccessArticle

Research on the Influence of Tip Clearance of Axial-Flow Pump on Energy Characteristics under Pump and Turbine Conditions

by Yanjun Li, Qixu Lin, Fan Meng, Yunhao Zheng and Xiaotian Xu

Machines 2022, 10(1), 56; https://doi.org/10.3390/machines10010056 - 12 Jan 2022

Cited by 13 | Viewed by 3034

Abstract

In order to study the influence of tip clearance on the performance and energy dissipation of the axial-flow pump and the axial-flow pump as a turbine, and find the location of high dissipation rate, this study took an axial-flow pump model as its [...] Read more.

In order to study the influence of tip clearance on the performance and energy dissipation of the axial-flow pump and the axial-flow pump as a turbine, and find the location of high dissipation rate, this study took an axial-flow pump model as its research object and designed four tip radial clearance schemes (0, 0.2, 1 and 2 mm). The unsteady calculation simulation of each tip clearance scheme was carried out based on CFD technology. The calculated results were compared with the experimental results, and the simulation results were analyzed using entropy production analysis theory. The results showed that, under both an axial-flow pump and axial-flow pump as turbine operating conditions, increasing the blade tip clearance led to a decrease in hydraulic performance. Compared with the 0 mm clearance, the maximum decreases in pump efficiency, head and shaft power under 2 mm tip clearance were 15.3%, 25.7% and 12.3% under the pump condition, and 12.7%, 18.5% and 28.8% under the turbine condition, respectively. Under the axial-flow pump operating condition, the change in blade tip clearance had a great influence on the total dissipation of the impeller, guide vane and outlet passage, and the maximum variation under the flow rate of 1.0

Q_{d e s}

was 53.9%, 32.1% and 54.2%, respectively. Under the axial-flow pump as a turbine operating condition, the change in blade tip clearance had a great influence on the total dissipation of the impeller and outlet passage, the maximum variation under the flow rate of 1.0

Q_{d e s}

was 22.7% and 17.4%, respectively. Under the design flow rate condition, with the increase in tip clearance, the dissipation rate of the blade surface showed an increasing trend under both the axial-flow pump and axial-flow pump as turbine operating conditions, and areas of high dissipation rate were generated at the rim and clearance. Full article

(This article belongs to the Special Issue Optimization and Flow Characteristics in Advanced Fluid Machinery)

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16 pages, 19861 KiB

Open AccessArticle

Dynamics Modelling and Control of a Novel Fuel Metering Valve Actuated by Two Binary-Coded Digital Valve Arrays

by Qiang Gao, Yong Zhu and Jinhua Liu

Machines 2022, 10(1), 55; https://doi.org/10.3390/machines10010055 - 12 Jan 2022

Cited by 33 | Viewed by 2670

Abstract

A fuel metering valve actuated by two binary-coded digital valve arrays (BDVAs) is proposed to improve the reliability of conventional fuel metering valves piloted by a servo valve. The design concept of this configuration is obtained from the structural characteristics of the dual [...] Read more.

A fuel metering valve actuated by two binary-coded digital valve arrays (BDVAs) is proposed to improve the reliability of conventional fuel metering valves piloted by a servo valve. The design concept of this configuration is obtained from the structural characteristics of the dual nozzle-flapper and the flow regulation method of the digital hydraulic technology. The structure and working principle of the fuel metering valve are presented. Then, a mathematical model of the entire valve is developed for dynamic analysis. Subsequently, the mechanism of the transient flow uncertainty of the BDVA is revealed through simulation to determine the fluctuation in the velocity of the fuel metering valve. Furthermore, step response indicates that the delay time of the fuel metering valve is within 4.1 ms. Finally, to improve the position tracking accuracy of the fuel metering valve, a velocity feedforward proportional-integral controller with pulse code modulation is proposed. A series of comparative analyses indicate that compared with those of the velocity feedforward controller, the average and standard deviation of the position error for the proposed controller are reduced by 78 and 72.7%, respectively. The results prove the feasibility of the proposed valve and the effectiveness of the proposed control strategy. Full article

(This article belongs to the Special Issue Advanced Control of Industrial Electro-Hydraulic Systems)

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20 pages, 5688 KiB

Open AccessArticle

Design of an Innovative Test Rig for Industrial Bearing Monitoring with Self-Balancing Layout

by Eugenio Brusa, Cristiana Delprete, Lorenzo Giorio, Luigi Gianpio Di Maggio and Vittorio Zanella

Machines 2022, 10(1), 54; https://doi.org/10.3390/machines10010054 - 11 Jan 2022

Cited by 5 | Viewed by 3785

Abstract

The remote prognosis and diagnosis of bearings can prevent industrial system failures, but the availability of realistic experimental data, being as close as possible to those detected in industrial applications, is essential to validate the monitoring algorithms. In this paper, an innovative bearing [...] Read more.

The remote prognosis and diagnosis of bearings can prevent industrial system failures, but the availability of realistic experimental data, being as close as possible to those detected in industrial applications, is essential to validate the monitoring algorithms. In this paper, an innovative bearing test rig architecture is presented, based on the novel concept of “self-contained box”. The monitoring activity is applicable to a set of four middle-sized bearings simultaneously, while undergoing the independent application of radial and axial loads in order to simulate the behavior of the real industrial machinery. The impact of actions on the platform and supports is mitigated by the so-called “self-contained box” layout, leading to self-balancing of actions within the rotor system. Moreover, the high modularity of this innovative layout allows installing various sized bearings, just changing mechanical adapters. This leads to a reduction of cost as well as of system down-time required to change bearings. The test rig is equipped with suitable instrumentation to develop effective procedures and tools for in- and out-monitoring of the system. An initial characterization of the healthy system is presented. Full article

(This article belongs to the Special Issue Design and Manufacture of Advanced Machines)

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23 pages, 68117 KiB

Open AccessArticle

A p−V Diagram Based Fault Identification for Compressor Valve by Means of Linear Discrimination Analysis

by Xueying Li, Peng Ren, Zhe Zhang, Xiaohan Jia and Xueyuan Peng

Machines 2022, 10(1), 53; https://doi.org/10.3390/machines10010053 - 10 Jan 2022

Cited by 9 | Viewed by 2998

Abstract

The pressure-volume diagram (p−V diagram) is an established method for analyzing the thermodynamic process in the cylinder of a reciprocating compressor as well as the fault of its core components including valves. The failure of suction/discharge valves is the most common cause of [...] Read more.

The pressure-volume diagram (p−V diagram) is an established method for analyzing the thermodynamic process in the cylinder of a reciprocating compressor as well as the fault of its core components including valves. The failure of suction/discharge valves is the most common cause of unscheduled shutdowns, and undetected failure may lead to catastrophic accidents. Although researchers have investigated fault classification by various estimation techniques and case studies, few have looked deeper into the barriers and pathways to realize the level determination of faults. The initial stage of valve failure is characterized in the form of mild leakage; if this is identified at this period, more serious accidents can be prevented. This study proposes a fault diagnosis and severity estimation method of the reciprocating compressor valve by virtue of features extracted from the p−V diagram. Four-dimensional characteristic variables consisting of the pressure ratio, process angle coefficient, area coefficient, and process index coefficient are extracted from the p−V diagram. Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were applied to establish the diagnostic model, where PCA realizes feature amplification and projection, then LDA implements feature dimensionality reduction and failure prediction. The method was validated by the diagnosis of various levels of severity of valve leakage in a reciprocating compressor, and further, applied in the diagnosis of two actual faults: Mild leakage caused by the cracked valve plate in a reciprocating compressor, and serious leakage caused by the deformed valve in a hydraulically driven piston compressor for a hydrogen refueling station (HRS). Full article

(This article belongs to the Special Issue Fault Diagnosis and Health Management of Power Machinery)

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9 pages, 1939 KiB

Open AccessCommunication

An Open-Source Low-Cost Imaging System Plug-In for Pheromone Traps Aiding Remote Insect Pest Population Monitoring in Fruit Crops

by Mark Jacob Schrader, Peter Smytheman, Elizabeth H. Beers and Lav R. Khot

Machines 2022, 10(1), 52; https://doi.org/10.3390/machines10010052 - 10 Jan 2022

Cited by 13 | Viewed by 2387

Abstract

This note describes the development of a plug-in imaging system for pheromone delta traps used in pest population monitoring. The plug-in comprises an RGB imaging sensor integrated with a microcontroller unit and associated hardware for optimized power usage and data capture. The plug-in [...] Read more.

This note describes the development of a plug-in imaging system for pheromone delta traps used in pest population monitoring. The plug-in comprises an RGB imaging sensor integrated with a microcontroller unit and associated hardware for optimized power usage and data capture. The plug-in can be attached to the top of a modified delta trap to realize periodic image capture of the trap liner (17.8 cm × 17.8 cm). As configured, the captured images are stored on a microSD card with ~0.01 cm² pixel⁻¹ spatial resolution. The plug-in hardware is configured to conserve power, as it enters in sleep mode during idle operation. Twenty traps with plug-in units were constructed and evaluated in the 2020 field season for codling moth (Cydia pomonella) population monitoring in a research study. The units reliably captured images at daily interval over the course of two weeks with a 350 mAh DC power source. The captured images provided the temporal population dynamics of codling moths, which would otherwise be achieved through daily manual trap monitoring. The system’s build cost is about $33 per unit, and it has potential for scaling to commercial applications through Internet of Things-enabled technologies integration. Full article

(This article belongs to the Special Issue Recent Advances in Computer Vision Technology and Its Agricultural Application)

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15 pages, 5619 KiB

Open AccessArticle

A Robust Operation Method with Advanced Adiabatic Compressed Air Energy Storage for Integrated Energy System under Failure Conditions

by Rong Xie, Weihuang Liu, Muyan Chen and Yanjun Shi

Machines 2022, 10(1), 51; https://doi.org/10.3390/machines10010051 - 09 Jan 2022

Cited by 2 | Viewed by 1547

Abstract

Integrated energy system (IES) is an important direction for the future development of the energy industry, and the stable operation of the IES can ensure heat and power supply. This study established an integrated system composed of an IES and advanced adiabatic compressed [...] Read more.

Integrated energy system (IES) is an important direction for the future development of the energy industry, and the stable operation of the IES can ensure heat and power supply. This study established an integrated system composed of an IES and advanced adiabatic compressed air energy storage (AA-CAES) to guarantee the robust operation of the IES under failure conditions. Firstly, a robust operation method using the AA-CAES is formulated to ensure the stable operation of the IES. The method splits the energy release process of the AA-CAES into two parts: a heat-ensuring part and a power-ensuring part. The heat-ensuring part uses the high-temp tank to maintain the balance of the heat subnet of the IES, and the power-ensuring part uses the air turbine of the first stage to maintain the balance of the power subnet. Moreover, another operation method using a spare gas boiler is formulated to compare the income of the IES with two different methods under failure conditions. The results showed that the AA-CAES could guarantee the balance of heat subnet and power subnet under steady conditions, and the dynamic operation income of the IES with the AA-CAES method was a bit higher than the income of the IES with the spare gas boiler method. Full article

(This article belongs to the Special Issue Emerging Techniques and Their Application in Turbomachinery)

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29 pages, 8913 KiB

Open AccessArticle

An Effective Dynamic Path Planning Approach for Mobile Robots Based on Ant Colony Fusion Dynamic Windows

by Liwei Yang, Lixia Fu, Ping Li, Jianlin Mao and Ning Guo

Machines 2022, 10(1), 50; https://doi.org/10.3390/machines10010050 - 09 Jan 2022

Cited by 30 | Viewed by 3707

Abstract

To further improve the path planning of the mobile robot in complex dynamic environments, this paper proposes an enhanced hybrid algorithm by considering the excellent search capability of the ant colony optimization (ACO) for global paths and the advantages of the dynamic window [...] Read more.

To further improve the path planning of the mobile robot in complex dynamic environments, this paper proposes an enhanced hybrid algorithm by considering the excellent search capability of the ant colony optimization (ACO) for global paths and the advantages of the dynamic window approach (DWA) for local obstacle avoidance. Firstly, we establish a new dynamic environment model based on the motion characteristics of the obstacles. Secondly, we improve the traditional ACO from the pheromone update and heuristic function and then design a strategy to solve the deadlock problem. Considering the actual path requirements of the robot, a new path smoothing method is present. Finally, the robot modeled by DWA obtains navigation information from the global path, and we enhance its trajectory tracking capability and dynamic obstacle avoidance capability by improving the evaluation function. The simulation and experimental results show that our algorithm improves the robot’s navigation capability, search capability, and dynamic obstacle avoidance capability in unknown and complex dynamic environments. Full article

(This article belongs to the Topic Motion Planning and Control for Robotics)

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15 pages, 5787 KiB

Open AccessArticle

The Influence of the Material Type and the Placement in the Print Chamber on the Roughness of MJF-Printed 3D Objects

by Damian Dzienniak

Machines 2022, 10(1), 49; https://doi.org/10.3390/machines10010049 - 09 Jan 2022

Cited by 8 | Viewed by 1771

Abstract

This paper describes a surface-roughness study performed on samples manufactured additively using the Multi Jet Fusion (MJF) technology. The samples were divided into three groups based on the material used in the process: polypropylene (PP), thermoplastic polyurethane (TPU), and polyamide 11 (PA11). Subsequently, [...] Read more.

This paper describes a surface-roughness study performed on samples manufactured additively using the Multi Jet Fusion (MJF) technology. The samples were divided into three groups based on the material used in the process: polypropylene (PP), thermoplastic polyurethane (TPU), and polyamide 11 (PA11). Subsequently, they were tested by means of a roughness-measuring system, which made it possible to determine the typical surface roughness parameters (

R_{a}

,

R_{q}

,

R_{z}

). The tests were designed to examine whether the placement and orientation of 3D objects while printing, in connection with the material used, can significantly influence the surface quality of MJF-printed objects. The results show that the TPU samples have a surface roughness much higher than the PP and PA11 ones, which exhibit roughness levels very similar to each other. It can also be concluded that surfaces printed vertically (along the Z-axis) tend to be less smooth—similarly to the surfaces of objects made of TPU located in the central zones of the print chamber during printing. This information may be of value in cases where low surface roughness is preferred (e.g., manufacturing patient-specific orthoses), although this particular study does not focus on one specific application. Full article

(This article belongs to the Special Issue Advances and Trends in Non-conventional, Abrasive and Precision Machining 2021)

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11 pages, 6220 KiB

Open AccessCommunication

Operating Characteristic Analysis and Verification of Short-Stroke Linear Oscillating Actuators Considering Mechanical Load

by Woo-Hyeon Kim, Chang-Woo Kim, Hyo-Seob Shin, Kyung-Hun Shin and Jang-Young Choi

Machines 2022, 10(1), 48; https://doi.org/10.3390/machines10010048 - 09 Jan 2022

Cited by 1 | Viewed by 1508

Abstract

Linear oscillating machines are electric devices that reciprocate at a specific frequency and at a specific stroke. Because of their linear motion, they are used in special applications, such as refrigerators for home appliances and medical devices. In this paper, the structure and [...] Read more.

Linear oscillating machines are electric devices that reciprocate at a specific frequency and at a specific stroke. Because of their linear motion, they are used in special applications, such as refrigerators for home appliances and medical devices. In this paper, the structure and electromagnetic characteristics of these linear oscillating machines are investigated, and the stroke is calculated according to voltage and motion equations. In addition, static and transient behavior analysis is performed, considering mechanical systems such as springs, damping systems, and mover mass. Furthermore, in this study, the magnetic force is analyzed, experiments are conducted according to the input power, and the current magnitude and stroke characteristics are analyzed according to the input frequency. Finally, the study confirmed that the most efficient operation is possible when the electrical resonance frequency matches the resonance frequency of the linear oscillating machines. Full article

(This article belongs to the Special Issue Design and Manufacture of Advanced Machines)

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23 pages, 4768 KiB

Open AccessArticle

Capacitor Clamped Coupled Inductor Bi-Directional DC-DC Converter with Smooth Starting

by Kalamchety Srinivasa Ravi Kumar, Alagappan Pandian, Vedula Venkata Sastry and Dogga Raveendhra

Machines 2022, 10(1), 47; https://doi.org/10.3390/machines10010047 - 08 Jan 2022

Cited by 3 | Viewed by 2417

Abstract

In this paper, a new type of capacitor clamped coupled inductor bidirectional DC–DC converter is proposed, which offers high voltage gain with smooth starting current transients, as well as reduced stresses on the capacitor. Steady state operation, mathematical modelling, and state space modelling [...] Read more.

In this paper, a new type of capacitor clamped coupled inductor bidirectional DC–DC converter is proposed, which offers high voltage gain with smooth starting current transients, as well as reduced stresses on the capacitor. Steady state operation, mathematical modelling, and state space modelling for the proposed converter are presented in detail. A simplified single voltage clamped circuit is developed to mitigate the voltage spikes caused due to the coupled inductor by recovering the leakage energy effectively. Moreover, the clamping capacitor helps in reducing the ripples in output voltage, which in effect significantly reduces the stress on the switch and offers less ripple content at the load terminals. Simulation of the proposed converter is carried out using Simulink/MATLAB for the conversion of 24V DC to 200V DC. For this conversion, simulation results have proven that there is reduction of 13.64% of capacitor voltage stresses. Further, under line varying conditions, converter responses have proven that there is a 119% and 25.25% reduction in input current and output voltage transients, respectively. Similarly, 25.25% and 76.5% transient reductions of input current are observed for line and control parameter variations. The hardware investigation of the converter was carried out with a 100 W, 24 V/200 V setup. The converter achieved efficiency of 93.8%. The observations supplement the simulation results. Full article

(This article belongs to the Special Issue Advances in Electrical Machines, Drives and Vehicles)

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28 pages, 6057 KiB

Open AccessEditor’s ChoiceArticle

Identification of Vehicle System Dynamics from the Aspect of Interaction between the Steering and the Suspension Systems

by Danijela Miloradović, Jovanka Lukić, Jasna Glišović and Nenad Miloradović

Machines 2022, 10(1), 46; https://doi.org/10.3390/machines10010046 - 08 Jan 2022

Cited by 2 | Viewed by 1636

Abstract

Steering and suspension systems of a motor vehicle have very important mutual connections that have direct influence on a vehicle’s steerability, stability, comfort and life expectancy. These mechanical and functional couplings cause an intensive interaction between the two mentioned vehicle systems on a [...] Read more.

Steering and suspension systems of a motor vehicle have very important mutual connections that have direct influence on a vehicle’s steerability, stability, comfort and life expectancy. These mechanical and functional couplings cause an intensive interaction between the two mentioned vehicle systems on a geometrical, kinematical and dynamical level. This article presents a study on nonparametric identification of dynamic interaction between the steering and the suspension system of a passenger vehicle. A specific methodology for experimental research in on-road conditions was designed that was in line with the research objectives and the applied measuring system. Experimental data were acquired for a curvilinear drive, with different constant driving speeds and on different roads. A multiple input/multiple output model for identification of the vehicle dynamics system from the aspect of interaction between the steering and the suspension system was developed. The analysis of experimental data was realized with the selection of a corresponding identification model, decoupling of model inputs and conditioned spectral analysis. The results of the conditioned spectral analysis of experimentally obtained data records indicate the level of interaction between the observed input and output parameters of the steering and the suspension systems to be in the frequency range below 30 Hz. Full article

(This article belongs to the Section Vehicle Engineering)

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20 pages, 3819 KiB

Open AccessArticle

Advancing Smart Manufacturing in Europe: Experiences from Two Decades of Research and Innovation Projects

by Paul Grefen, Irene Vanderfeesten, Kostas Traganos, Zuzanna Domagala-Schmidt and Julia van der Vleuten

Machines 2022, 10(1), 45; https://doi.org/10.3390/machines10010045 - 07 Jan 2022

Cited by 6 | Viewed by 2844

Abstract

In the past two decades, a large amount of attention has been devoted to the introduction of smart manufacturing concepts and technologies into industrial practice. In Europe, these efforts have been supported by European research and innovation programs, bringing together research and application [...] Read more.

In the past two decades, a large amount of attention has been devoted to the introduction of smart manufacturing concepts and technologies into industrial practice. In Europe, these efforts have been supported by European research and innovation programs, bringing together research and application parties. In this paper, we provide an overview of a series of four content-wise connected projects on the European scale that are aimed at advancing smart manufacturing, with a focus on connecting processes on smart factory shop floors to manufacturing equipment on the one hand and enterprise-level business processes on the other hand. These projects cover several tens of application cases across Europe. We present our experiences in the form of a single, informal longitudinal case study, highlighting both the major advances and the current limitations of developments. To organize these experiences, we place them in the context of the well-known RAMI4.0 reference framework for Industry 4.0 (covering the ISA-95 standard). Then, we analyze the experiences, both the positive ones and those including problems, and draw our learnings from these. In doing so, we do not present novel technological developments in this paper—these are presented in the papers we refer to—but concentrate on the main issues we have observed to guide future developments in research efforts and industrial innovation in the smart industry domain. Full article

(This article belongs to the Special Issue Intelligent Factory 4.0: Advanced Production and Automation Systems)

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16 pages, 3427 KiB

Open AccessFeature PaperArticle

Research on a Measurement Method for Middle-Infrared Radiation Characteristics of Aircraft

by Xuan Deng, Yueming Wang, Guicheng Han and Tianru Xue

Machines 2022, 10(1), 44; https://doi.org/10.3390/machines10010044 - 07 Jan 2022

Cited by 5 | Viewed by 2113

Abstract

Aiming at the problem wherein temperature inversion accuracy is unstable due to the major differences in atmospheric transmittance under various observation paths, a method for measuring radiation characteristics of an aircraft engine’s hot parts and skin using a cooled middle-wave infrared camera is [...] Read more.

Aiming at the problem wherein temperature inversion accuracy is unstable due to the major differences in atmospheric transmittance under various observation paths, a method for measuring radiation characteristics of an aircraft engine’s hot parts and skin using a cooled middle-wave infrared camera is proposed. Based on the analysis of the aircraft’s infrared radiation characteristics, the atmospheric transmission model of any observation path was revised, the absolute radiation correction model was established, and the temperature inversion equation was calculated. Then, we used the quasi-Newton method to calculate the skin temperature and discussed uncertainty sources. After the theoretical study, an outfield test was carried out. A middle-wave infrared camera with a wavelength of 3.7–4.8 μm was applied to the actual experimental observation of the turbofan civil aviation aircraft. The ground observation distance was 15 km, and the flying height was 3 km. When implementing temperature inversion with the method presented in this paper, the surface temperature of the aircraft engine hot parts was 381 K, the correction uncertainty was ±10 K, the surface temperature of the skin was 296 K, and the correction uncertainty was ±6 K. As the experiment showed, the method in this paper can effectively implement infrared target temperature inversion and provide a reference for the quantification of infrared data. Full article

(This article belongs to the Special Issue Precision Measurement and Machines)

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16 pages, 4532 KiB

Open AccessArticle

Recognition of Human Face Regions under Adverse Conditions—Face Masks and Glasses—In Thermographic Sanitary Barriers through Learning Transfer from an Object Detector

by Joabe R. da Silva, Gustavo M. de Almeida, Marco Antonio de S. L. Cuadros, Hércules L. M. Campos, Reginaldo B. Nunes, Josemar Simão and Pablo R. Muniz

Machines 2022, 10(1), 43; https://doi.org/10.3390/machines10010043 - 07 Jan 2022

Cited by 5 | Viewed by 2085

Abstract

The COVID-19 pandemic has detrimentally affected people’s lives and the economies of many countries, causing disruption in the health, education, transport, and other sectors. Several countries have implemented sanitary barriers at airports, bus and train stations, company gates, and other shared spaces to [...] Read more.

The COVID-19 pandemic has detrimentally affected people’s lives and the economies of many countries, causing disruption in the health, education, transport, and other sectors. Several countries have implemented sanitary barriers at airports, bus and train stations, company gates, and other shared spaces to detect patients with viral symptoms in an effort to contain the spread of the disease. As fever is one of the most recurrent disease symptoms, the demand for devices that measure skin (body surface) temperature has increased. The thermal imaging camera, also known as a thermal imager, is one such device used to measure temperature. It employs a technology known as infrared thermography and is a noninvasive, fast, and objective tool. This study employed machine learning transfer using You Only Look Once (YOLO) to detect the hottest temperatures in the regions of interest (ROIs) of the human face in thermographic images, allowing the identification of a febrile state in humans. The algorithms detect areas of interest in the thermographic images, such as the eyes, forehead, and ears, before analyzing the temperatures in these regions. The developed software achieved excellent performance in detecting the established areas of interest, adequately indicating the maximum temperature within each region of interest, and correctly choosing the maximum temperature among them. Full article

(This article belongs to the Special Issue Industrial Applications: New Solutions for the New Era)

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20 pages, 7336 KiB

Open AccessArticle

An Intravascular Catheter Bending Recognition Method for Interventional Surgical Robots

by Wei Wei, Dong Yang, Li Li and Yuxuan Xia

Machines 2022, 10(1), 42; https://doi.org/10.3390/machines10010042 - 06 Jan 2022

Cited by 4 | Viewed by 2447

Abstract

Robot-assisted interventional surgery can greatly reduce the radiation received by surgeons during the operation, but the lack of force detection and force feedback is still a risk in the operation which may harm the patient. In those robotic surgeries, the traditional force detection [...] Read more.

Robot-assisted interventional surgery can greatly reduce the radiation received by surgeons during the operation, but the lack of force detection and force feedback is still a risk in the operation which may harm the patient. In those robotic surgeries, the traditional force detection methods may have measurement losses and errors caused by mechanical transmission and cannot identify the direction of the force. In this paper, an interventional surgery robot system with a force detection device is designed and a new force detection method based on strain gauges is proposed to detect the force and infer the bending direction of the catheter in the vessel by using BP neural network. In addition, genetic algorithm is used to optimize the BP neural network, and the error between the calculated results and the actual results is reduced by 37%, which improves the accuracy of catheter bending recognition. Combining this new method with traditional force sensors not only reduces the error caused by the traditional mechanical transmission, but also can detect the bending direction of the catheter in the blood vessel, which greatly improves the safety of the operation. Full article

(This article belongs to the Topic Recent Advances in Robotics and Networks)

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21 pages, 11629 KiB

Open AccessArticle

Analysis of the Formation Mechanism of Secondary Tip Leakage Vortex (S-TLV) in an Axial Flow Pump

by Hu Zhang, Jianbo Zang, Desheng Zhang, Weidong Shi and Jiean Shen

Machines 2022, 10(1), 41; https://doi.org/10.3390/machines10010041 - 05 Jan 2022

Cited by 7 | Viewed by 1718

Abstract

Studies on the tip leakage vortex (TLV) are extensive, while studies on the secondary tip leakage vortex (S-TLV) are rare. To advance the understanding of the formation mechanism of the S-TLV, turbulent cavitating flows were numerically investigated using the shear stress transport (SST) [...] Read more.

Studies on the tip leakage vortex (TLV) are extensive, while studies on the secondary tip leakage vortex (S-TLV) are rare. To advance the understanding of the formation mechanism of the S-TLV, turbulent cavitating flows were numerically investigated using the shear stress transport (SST) turbulence model and the Zwart–Gerber–Belamri cavitation model. The morphology and physical quantity distribution of the S-TLV under two cavitation conditions were compared, and its formation mechanism was analyzed. The results reveal that in the lower cavitation number case, there is a low-velocity zone of circumferential flow near the tip in the back half of the blade. The shear vortices formed by the leakage jet gradually accumulate and concentrate in the low-velocity area, which is one of the main sources of the S-TLV. Meanwhile, the radial jet pushes the vortices on the suction surface to the tip, which mixes with the S-TLV. The flow path formed by the radial jet and the leakage jet is in accordance with the rotation direction of the S-TLV, which promotes the S-TLV’s further development. Under the conditions of a small cavitation number and low flow rate, the circumferential velocity and radial velocity of the fluid near the gap have altered significantly, which is conducive to the formation of the S-TLV. Full article

(This article belongs to the Special Issue Optimization and Flow Characteristics in Advanced Fluid Machinery)

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15 pages, 4223 KiB

Open AccessArticle

Correlation between the Internal Flow Pattern and the Blade Load Distribution of the Centrifugal Impeller

by Bo Chen, Xiaowu Chen, Zuchao Zhu and Xiaojun Li

Machines 2022, 10(1), 40; https://doi.org/10.3390/machines10010040 - 05 Jan 2022

Cited by 2 | Viewed by 1338

Abstract

The blade load distributions reflect the working characteristics of centrifugal impellers, and the vortexes in the impeller channel affect the blade load distribution, but the mechanism of this phenomenon is still unclear. In this study, particle image velocimetry (PIV) was adopted to clarify [...] Read more.

The blade load distributions reflect the working characteristics of centrifugal impellers, and the vortexes in the impeller channel affect the blade load distribution, but the mechanism of this phenomenon is still unclear. In this study, particle image velocimetry (PIV) was adopted to clarify the correlation between the internal flow pattern and the blade load distribution. The internal flow pattern and the blade load distribution were presented under different working conditions to study the influence of the internal flow pattern on the blade load. Results showed that the vortexes in the flow channel redistributed the blade load. The clockwise vortex made the position of the maximum blade load closer to the outlet, while the counterclockwise vortex had the opposite effect. Meanwhile, the vortexes caused the blade load distribution to be steeper, which reduced energy conversion efficiency. Moreover, the mean absolute flow angle was introduced to explain the mechanism of the effects of vortexes on blade load. The results can be used as a theoretical basis for the design of high-performance impellers. Full article

(This article belongs to the Special Issue Optimization and Flow Characteristics in Advanced Fluid Machinery)

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19 pages, 4425 KiB

Open AccessArticle

Influences of Randomly Uncertain Factors on Dynamic Coefficients of an Interlocking Labyrinth Seal-Rotor System

by Xin Xiong, Yanfei Zhou and Yiqun Wang

Machines 2022, 10(1), 39; https://doi.org/10.3390/machines10010039 - 04 Jan 2022

Cited by 2 | Viewed by 1371

Abstract

Many randomly uncertain factors inevitably arise when gas flows through a labyrinth seal, and the orbit of the rotor center will not rotate along a steady trajectory, as previously studied. Here, random uncertainty is considered in an interlocking labyrinth seal-rotor system to investigate [...] Read more.

Many randomly uncertain factors inevitably arise when gas flows through a labyrinth seal, and the orbit of the rotor center will not rotate along a steady trajectory, as previously studied. Here, random uncertainty is considered in an interlocking labyrinth seal-rotor system to investigate the fluctuations of dynamic coefficients. The bounded noise excitation is introduced into the momentum equation of the gas flow, and as a result, the orbit of the rotor center is expressed as the combination of an elliptic trajectory with the bounded noise perturbation. Simulation results of the coefficients under randomly uncertain perturbations with various strengths are comparatively investigated with the traditional predictions under ideal conditions, from which the influences of random uncertain factors on dynamic coefficients are analyzed in terms of the rotor speed, pressure difference, and inlet whirl velocity. It is shown that the deviation levels of the dynamic coefficients are directly related to the random perturbations and routinely increase with such perturbation strengths, and the coefficients themselves may exhibit distinct variation patterns against the rotor speed, pressure difference, and inlet whirl velocity. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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16 pages, 5882 KiB

Open AccessEditor’s ChoiceArticle

Fatigue Analysis of Dozer Push Arms under Tilt Bulldozing Conditions

by Longye Pan, Xianglong Guan, Xingwei Luan, Yajun Huang, Ruwei Zhang, Jin-Hwan Choi and Xiangqian Zhu

Machines 2022, 10(1), 38; https://doi.org/10.3390/machines10010038 - 04 Jan 2022

Cited by 3 | Viewed by 4945

Abstract

Tilt bulldozing generates unbalanced loads on two push arms, which leads to the service lives of the two push arms being different. Because the push arms rotate in triaxial directions during tilt bulldozing, it is difficult to accurately analyze the fatigue life of [...] Read more.

Tilt bulldozing generates unbalanced loads on two push arms, which leads to the service lives of the two push arms being different. Because the push arms rotate in triaxial directions during tilt bulldozing, it is difficult to accurately analyze the fatigue life of the push arm with one specific boundary condition and loading history. Therefore, a fatigue analysis of the push arms under tilt bulldozing conditions is proposed based on co-simulation of RecurDyn-EDEM-AMESim in this paper. The control of tilt bulldozing conditions is realized automatically according to the tilt angle and blade depth. The dynamic loads of the push arms are accurately calculated in this virtual model. Subsequently, the stress–time histories are obtained to investigate the fatigue lives of push arms. Both the overall damage and the initiation positions of the cracks are predicted herein. It is determined that the fatigue lives of the right and left push arms are 7,317.84 h and 39,381.89 h, respectively. Thus, the life of the push arm on the blade’s tilted side is reduced by 81.42% compared to the other side. Additionally, experimental tests are conducted to verify the accuracy of the virtual model. Analysis results indicate that the strains of the push arms according to the virtual simulation are close to those measured in the experiments. Full article

(This article belongs to the Special Issue Dynamics and Diagnostics of Heavy-Duty Industrial Machines)

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