International Journal of Turbomachinery, Propulsion and Power

8 pages, 3260 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Leading Edge Bumps for Flow Control in Air-Cooled Condensers

by Lorenzo Tieghi, Giovanni Delibra, Johan van der Spuy and Alessandro Corsini

Int. J. Turbomach. Propuls. Power 2023, 8(1), 9; https://doi.org/10.3390/ijtpp8010009 - 09 Mar 2023

Cited by 1 | Viewed by 1842

Air-cooled condensers (ACCs) are commonly found in power plants working with concentrated solar power or in steam power plants operated in regions with limited water availability. In ACCs, the flow of air is driven toward the heat exchangers by axial fans that are [...] Read more.

Air-cooled condensers (ACCs) are commonly found in power plants working with concentrated solar power or in steam power plants operated in regions with limited water availability. In ACCs, the flow of air is driven toward the heat exchangers by axial fans that are characterized by large diameters and operate at very high mass flow rates with a near-zero static pressure rise. Given the overall requirements in steam plants, these fans are subjected to inflow distortions, unstable operations, and are characterized by high noise emissions. Previous studies show that leading edge bumps in the tip region of axial fans can effectively reduce the sound pressure levels without affecting the static efficiency. Nevertheless, the effects of this treatment in terms of flow patterns and heat exchange in the whole ACC system were not investigated. In this work, the effect of leading edge bumps on the flow patterns is analyzed. Two RANS simulations were carried out using OpenFOAM on a simplified model of the air-cooled condenser. The fans are simulated using a frozen rotor approach. Turbulence modeling relies on the RNG k-epsilon model. The fan is characterized by a diameter of 7.3 m and a 333 m³/s volumetric flow rate at the design point. The presence of the heat exchanger is modeled using a porous medium. The comparison between the flow fields clearly exerts that the modified blade is responsible for the redistribution of radial velocities in the rotor region. This drastically reduces the losses related to the installation of the fan in a real configuration. Full article

(This article belongs to the Special Issue Selected Turbomachinery Papers from the 18th Conference on Modelling Fluid Flow CMFF'22)

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15 pages, 8504 KiB

Open AccessEditor’s ChoiceArticle

Transient 3D CFD Simulation of a Pelton Turbine—A State-of-the-Art Approach for Pelton Development and Optimisation

by Lukas Sandmaier, Peter Meusburger and Helmut Benigni

Int. J. Turbomach. Propuls. Power 2023, 8(1), 10; https://doi.org/10.3390/ijtpp8010010 - 09 Mar 2023

Cited by 3 | Viewed by 2636

Abstract

The complex flow conditions in Pelton turbines make it challenging to gain detailed insight into the local flow processes. However, CFD methods offer vast potential for developing and optimising Pelton turbines due to these flow conditions. In a comprehensive examination, a six-nozzle prototype [...] Read more.

The complex flow conditions in Pelton turbines make it challenging to gain detailed insight into the local flow processes. However, CFD methods offer vast potential for developing and optimising Pelton turbines due to these flow conditions. In a comprehensive examination, a six-nozzle prototype Pelton turbine with 19 buckets has been investigated using 3D CFD simulations. First, the steady simulations of the manifold and the unsteady runner simulation have been performed with a mesh-based, commercial CFD code, whereby a two-equation turbulence model and the homogeneous two-phase model were used. Then, to limit the simulation time, symmetry was applied in the runner simulation, and also a strategic definition of the mesh element size in selected blocks of higher interest. Subsequently, the simulation results were analysed. Based on the first simulation results, the geometry of the distributor was modified in an iterative process to reduce losses and improve the jet shape. For the improvement of the latter, a characteristic number was introduced to quantify the secondary flows upstream of the nozzles, which act negatively on the jet shape. Furthermore, the results of the runner simulation were analysed with special regard to the jet-bucket interaction from the start to the end of the impingement cycle of a particular bucket. Finally, a potential efficiency increase could be derived from the summary. Full article

(This article belongs to the Special Issue Selected Turbomachinery Papers from the 18th Conference on Modelling Fluid Flow CMFF'22)

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12 pages, 5011 KiB

Open AccessEditor’s ChoiceArticle

Multi-Point, Multi-Objective Optimisation of Centrifugal Fans by 3D Inverse Design Method

by Jiangnan Zhang and Mehrdad Zangeneh

Int. J. Turbomach. Propuls. Power 2023, 8(1), 8; https://doi.org/10.3390/ijtpp8010008 - 02 Mar 2023

Cited by 1 | Viewed by 1833

Abstract

In this paper, we present the design and optimization of a centrifugal fan with requirements of maximizing the total-to-static pressure rise and total-to-static efficiency at two operating points and the maximum torque provided by the motor power using a 3D inverse design method, [...] Read more.

In this paper, we present the design and optimization of a centrifugal fan with requirements of maximizing the total-to-static pressure rise and total-to-static efficiency at two operating points and the maximum torque provided by the motor power using a 3D inverse design method, a DOE (design of experiment) study, an RSM (response surface model) and a MOGA (multi-objective genetic algorithm). The fan geometry is parametrized using 13 design parameters, and 120 different designs are generated. The fan performances of all the designs at two operating conditions are evaluated through steady-state CFD simulations. The resulting design matrix is used to create an RSM based on the Kriging method and MOGA is used to search the design space using the RSM and find the optimal design. Full article

(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)

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11 pages, 1414 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Axial Impeller-Only Fans with Optimal Hub-to-Tip Ratio and Blades Adapted for Minimum Exit Loss

by Thomas Carolus and Konrad Bamberger

Int. J. Turbomach. Propuls. Power 2023, 8(1), 7; https://doi.org/10.3390/ijtpp8010007 - 01 Mar 2023

Cited by 1 | Viewed by 4011

Abstract

This study targets determining impellers of impeller-only axial fans with an optimal hub-to-tip ratio for the highest achievable total-to-static efficiency. Differently from other studies, a holistic approach is chosen. Firstly, the complete class of these fans is considered. Secondly, the radial distribution of [...] Read more.

This study targets determining impellers of impeller-only axial fans with an optimal hub-to-tip ratio for the highest achievable total-to-static efficiency. Differently from other studies, a holistic approach is chosen. Firstly, the complete class of these fans is considered. Secondly, the radial distribution of blade sweep angle, stagger angle, chord length, and camber are varied to adapt the blades to the complex flow in the hub and tip regions. The tool being used is an optimization scheme with three key components: (i) a database created beforehand by Reynolds-averaged Navier–Stokes (RANS)-predicted performance characteristics of 14,000 designs, (ii) an artificial neural network as a metamodel for the fan performance as a function of 26 geometrical parameters, and (iii) an evolutionary algorithm for optimization, performed on the metamodel. Typically, the hub-to-tip ratios for the impellers proposed by the optimization scheme are smaller than those obtained by applying the classic design rules. A second outcome are the shapes of the blades, which are adapted for a minimum exit loss. These shapes deviate substantially from the classic and even the state-of-the-art “swept-only” or “swept with dihedral” designs. The chord length, stagger, and sweep angle are distributed from hub to tip in a complex manner. The inherent reason is that the scheme tries to minimize not only the dynamic exit loss but also frictional losses due to secondary flows in the hub and tip regions, which eventually results in the maximum achievable total-to-static efficiency. Upon request, the authors will provide the full geometry of the four impellers analysed in some detail in this study to any individual for experimental validation or further analysis of their performance. Full article

(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)

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25 pages, 2750 KiB

Open AccessArticle

Enhancement of Rotor Loading and Suppression of Stator Separation through Reduction of the Blade–Row Gap

by Zhuo Wang, Lin Du and Xiaofeng Sun

Int. J. Turbomach. Propuls. Power 2023, 8(1), 6; https://doi.org/10.3390/ijtpp8010006 - 01 Mar 2023

Viewed by 1562

Abstract

An immersed boundary (IB) method is applied to study the effect of the blade–row gap in a low-speed single-stage compressor. The advantage of using an IB method is that the rotor/stator interface can be eliminated and, thus, the blade–row interaction can be considered [...] Read more.

An immersed boundary (IB) method is applied to study the effect of the blade–row gap in a low-speed single-stage compressor. The advantage of using an IB method is that the rotor/stator interface can be eliminated and, thus, the blade–row interaction can be considered at an extremely small gap. The IB method was modified to internal-flow problems, and the adaptive mesh refinement (AMR) technique, together with a wall model, used to facilitate the simulations for high Reynolds-number flows. The results showed that both the pressure rise and the efficiency were observed to be higher in the smaller-gap cases. Comparisons between the results of two gaps,

35 % c_{a}

and

3.5 % c_{a}

, are highlighted and further analysis at a specific flow coefficient showed that the increase of the stage performance was contributed to by the enhancement of rotor loading and the suppression to the flow separation of the stator. Correspondingly, the increases of the total pressure rise on the rotor and the stator outlets were observed to be

0.5 %

and

4.3 %

, respectively. Although the increase on the rotor outlet is much lower than that on the stator outlet, its significance is that a higher level of static pressure is formed near the hub of the gap, which, thus, reduces the adverse pressure gradient of this region in the stator passage. This improvement suppresses the flow separation near the hub of the stator and, thereby, results in a considerable increase to the pressure rise on the stator outlet as a consequence. The effect of the gap on unsteady pressure fluctuation is also presented. Full article

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26 pages, 9045 KiB

Open AccessEditor’s ChoiceArticle

Numerical Determination of the Equivalent Sand Roughness of a Turbopump’s Surface and Its Roughness Influence on the Pump Characteristics

by Benjamin Torner, Duc Viet Duong and Frank-Hendrik Wurm

Int. J. Turbomach. Propuls. Power 2023, 8(1), 5; https://doi.org/10.3390/ijtpp8010005 - 07 Feb 2023

Cited by 1 | Viewed by 2076

Abstract

The correct computation of flows over rough surfaces in technical systems, such as in turbomachines, is a significant issue for proper simulations of their performance data. Once the flow over rough surfaces is adequately computed in these machines, simulations become more trustworthy and [...] Read more.

The correct computation of flows over rough surfaces in technical systems, such as in turbomachines, is a significant issue for proper simulations of their performance data. Once the flow over rough surfaces is adequately computed in these machines, simulations become more trustworthy and can replace experimental prototyping. Roughness modelling approaches are often implemented in a solver to account for roughness effects in flow simulations. In these approaches, the equivalent sand roughness

k_{s}

must be defined as a characteristic parameter of the rough surface. However, it is difficult to determine the corresponding

k_{s}

-value for a surface roughness. In this context, this paper shows a novel and time-efficient numerical method, the discrete porosity method (DPM), which can be used to determine the

k_{s}

-value of a rough surface. Applying this method, channel flow simulations were performed with an irregularly distributed cast iron surface from a turbopumps volute. After identifying the fully rough regime, the equivalent sand roughness was determined and a match with

k_{s}

-values from literature data was found. Subsequently, the established

k_{s}

-value for cast iron was used in a turbopump simulation with rough walls. The performance data of the pump were validated by experiments and a good agreement between the experimental and simulated performance data was found. Full article

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9 pages, 1308 KiB

Open AccessEditor’s ChoiceArticle

Exergy-Based Efficiency Assessment of Fans vs. Isentropic Efficiency

by Johannes Brötz, Christian Schänzle and Peter F. Pelz

Int. J. Turbomach. Propuls. Power 2023, 8(1), 4; https://doi.org/10.3390/ijtpp8010004 - 06 Feb 2023

Viewed by 2259

Abstract

The efficiency definition allows us to compare two machines with each other. In general, the efficiency is defined as the ratio of usable power to the required power. This raises the question: what is the usable power? Most engineers discuss efficiency on the [...] Read more.

The efficiency definition allows us to compare two machines with each other. In general, the efficiency is defined as the ratio of usable power to the required power. This raises the question: what is the usable power? Most engineers discuss efficiency on the basis of the energy balance, i.e., the first law of thermodynamics. In this paper, we derive the exegetic efficiency taking the second law of thermodynamics into account. Exergy analysis takes into account work and heat and is able to model reality very accurately. On this basis, a comparison between the isentropic and exergetic efficiencies is given. A high-pressure radial fan is used as an example, and the differences are discussed. Therefore, measurements of a non-adiabatic fan are evaluated, and the role of the heat flux in the environment is discussed. The investigations show that a relevant difference between the isentropic and exergetic efficiencies becomes apparent in the partial-load range with high-pressure build-up. The thermal energy contained in the flow belongs proportionally to the exergy, i.e., the working capacity of the gas relative to its environment. For a standard such as ISO 5801 “Fans—Performance testing using standardized airways”, the efficiency must not only be physically correct, it must also be simple and practical. Against this background, the outlook of this paper discusses when and which efficiency definition is appropriate and best suited for a standard. Full article

(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)

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14 pages, 2531 KiB

Open AccessEditor’s ChoiceArticle

Data-Driven Anomaly Detection Framework for Complex Degradation Monitoring of Aero-Engine

by Zichen Yan, Jianzhong Sun, Yang Yi, Caiqiong Yang and Jingbo Sun

Int. J. Turbomach. Propuls. Power 2023, 8(1), 3; https://doi.org/10.3390/ijtpp8010003 - 01 Feb 2023

Cited by 1 | Viewed by 1799

Abstract

Data analysis is an important part of aero engine health management. In order to complete accurate condition monitoring, it is necessary to establish more effective analysis tools. Therefore, an integrated algorithm library dedicated for engine anomaly detection is established, which is PyPEFD (Python [...] Read more.

Data analysis is an important part of aero engine health management. In order to complete accurate condition monitoring, it is necessary to establish more effective analysis tools. Therefore, an integrated algorithm library dedicated for engine anomaly detection is established, which is PyPEFD (Python Package for Engine Fault Detection). Different algorithms for baseline modeling, anomaly detection and trend analysis are presented and compared. In this paper, the simulation data are used to verify the function of the anomaly detection algorithms, successfully completing the detection of multiple faults and comparing the accuracy algorithm under different conditions. Full article

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2 pages, 168 KiB

Open AccessEditorial

Acknowledgment to the Reviewers of IJTPP in 2022

by IJTPP Editorial Office

Int. J. Turbomach. Propuls. Power 2023, 8(1), 2; https://doi.org/10.3390/ijtpp8010002 - 20 Jan 2023

Viewed by 1166

Abstract

High-quality academic publishing is built on rigorous peer review [...] Full article

17 pages, 7595 KiB

Open AccessEditor’s ChoiceArticle

Active Turbulence Grid-Controlled Inflow Turbulence and Replication of Heat Exchanger Flow Fields in Fan Applications

by Felix Czwielong and Stefan Becker

Int. J. Turbomach. Propuls. Power 2023, 8(1), 1; https://doi.org/10.3390/ijtpp8010001 - 04 Jan 2023

Cited by 3 | Viewed by 2102

Abstract

A novel active turbulence grid of the Institute of Fluid Mechanics at FAU Erlangen-Nuremberg is introduced. The focus of this grid is not on basic investigations of fluid mechanics, as is usually the case with active turbulence grids, but the generation of defined [...] Read more.

A novel active turbulence grid of the Institute of Fluid Mechanics at FAU Erlangen-Nuremberg is introduced. The focus of this grid is not on basic investigations of fluid mechanics, as is usually the case with active turbulence grids, but the generation of defined inflow conditions for axial fans. Thus, by means of the active turbulence grid, individual turbulence characteristics in the flow to the fan can be changed; therefore, fundamental interactions between the flow mechanics at the axial fan and the sound radiation can be analyzed. In addition, the replication of the flow fields of heat exchangers by the active turbulence grid is the focus of the investigations. The investigations showed that it is possible to use the active turbulence grid to generate defined inflow conditions for axial fans. It was also possible to reproduce the heat exchanger flow fields both for the mean turbulence values and for the spatial distributions. It was found that the grid induces tonal components due to the drive motors, but also that the inherent noise has no significant influence on the spectrum of the fans under investigation. Based on selected turbulence characteristics, direct correlations were found between the spatial distribution of the turbulence level and sound radiation at the first blade passing frequency of the axial fan. As the variance of the turbulence level increases, the sound radiation of the tonal components becomes more pronounced. The total sound pressure level, however, is mainly determined by the low-frequency broadband sound. A linear relationship between the spatial mean value of the turbulence level and the total sound pressure level was found for the investigated axial fan. Full article

(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)

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Int. J. Turbomach. Propuls. Power, Volume 8, Issue 1 (March 2023) – 10 articles

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