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10th Anniversary of Machines—Feature Papers in Turbomachinery
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10th Anniversary of Machines—Feature Papers in Turbomachinery

A special issue of Machines (ISSN 2075-1702). This special issue belongs to the section "Turbomachinery".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 6032

Special Issue Editor

Dr. Matthias Meinke

E-Mail Website
Guest Editor
Rheinisch-Westfälische Technische Hochschule Aachen, Aachen, Germany
Interests: computing in mathematics; natural science; engineering and medicine; aerospace engineering; fluid dynamics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Since the invention of turbomachinery and its early practical use as steam turbines, we have seen an impressive and intensively ongoing development of turbomachinery components, which nowadays can be found in power plants, aircraft engines, the petrochemical industry, as well as a part of daily life, e.g., in HVAC applications. At present, there is a request for higher energy efficiency, extended operating ranges, as well as improved reliability and longer lifetime, which drives research and development. Due to the complexity of turbo engines, numerous fields of science are involved in research, such as fluid mechanics, thermodynamics, structural mechanics, etc. For this Special MDPI Issue on turbomachinery, we invite specialists in these fields to submit scientific papers with their latest achievements. Papers on the following non-exhaustive list of topics are accepted:

  • Compressors, fans, and pumps;
  • Gas, steam, hydraulic, and wind turbines;
  • Aerodynamics, heat transfer, structural dynamics, combustion, and acoustics;
  • Numerical methods and experimental techniques;
  • Machine learning, design, and optimization;
  • Control, diagnostics, and instrumentation;
  • Manufacturing, predictive maintenance, materials, bearings, and metallurgy.

The article processing charge (APC) for selected excellent publications in this Special Issue of the open access journal of CHF 1800 (Swiss Francs) will be waived and papers will be published as gold open access articles licensed under Creative Commons Licenses (CC).

Dr. Matthias Meinke
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Machines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (4 papers)

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Research

26 pages, 34640 KiB  
Article
Simulation and Validation of Cavitating Flow in a Torque Converter with Scale-Resolving Methods
by Jiahua Zhang, Qingdong Yan, Cheng Liu, Meng Guo and Wei Wei
Machines 2023, 11(4), 489; https://doi.org/10.3390/machines11040489 - 19 Apr 2023
Cited by 1 | Viewed by 1275
Abstract
The purpose of this paper is to study the mechanism and improve the prediction accuracy of transient torque converter cavitation flow by the application of scale-resolving simulation (SRS) methods with particular focus on cavitation vortex flow. Firstly, the numerical analysis of the entire [...] Read more.
The purpose of this paper is to study the mechanism and improve the prediction accuracy of transient torque converter cavitation flow by the application of scale-resolving simulation (SRS) methods with particular focus on cavitation vortex flow. Firstly, the numerical analysis of the entire internal flow field of the torque converter was carried out using different turbulence models, and the prediction accuracy of the hydraulic characteristics of the adopted models was analyzed and validated via test data. Secondly, the cavitation and turbulence behavior in the internal flow field were analyzed, and the blade surface pressure according to different turbulence models was compared and validated through test data. Finally, the transient cavitation characteristics of the flow field were studied based on the stress-blended eddy simulation (SBES) model. The prediction accuracy of the cavitation flow field simulation of the torque converter is significantly improved using the SRS model. The maximum error of capacity constant, torque ratio and efficiency are reduced to 3.1%, 2.3%, and 1.3% at stall, respectively. The stator is more prone to cavitation than pump and turbine. The SBES model has the highest prediction accuracy in multiple measurement points, and the maximum deviation can reach 13.32% under stall. Attached cavitation bubbles and periodic shedding cavitation can be found in the stator, and the evolution period is about 0.0036 s, i.e., 279 Hz. The prediction accuracy of different models was compared and analyzed, which has important guiding significance for the high-precision prediction and analysis of fluid machinery. Full article
(This article belongs to the Special Issue 10th Anniversary of Machines—Feature Papers in Turbomachinery)
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21 pages, 9307 KiB  
Article
Flow Regulation of Low Head Hydraulic Propeller Turbines by Means of Variable Rotational Speed: Aerodynamic Motivations
by Dario Barsi, Robert Fink, Peter Odry, Marina Ubaldi and Pietro Zunino
Machines 2023, 11(2), 202; https://doi.org/10.3390/machines11020202 - 01 Feb 2023
Cited by 1 | Viewed by 1626
Abstract
To date, hydraulic energy is still, among the renewable ones, the most widespread and most exploited to produce electricity. With the current trend to exploit any renewable source available, the limits for the economic convenience of hydroelectric power plants have significantly changed, making [...] Read more.
To date, hydraulic energy is still, among the renewable ones, the most widespread and most exploited to produce electricity. With the current trend to exploit any renewable source available, the limits for the economic convenience of hydroelectric power plants have significantly changed, making it interesting and convenient to use even small heads and low flow rates. In the specific applications of hydraulic turbines operating with low heads, the Kaplan turbine plays the predominant role among the available machines, also given the possibility of carrying out an “on cam” regulation, acting simultaneously on the geometry of the rotor and distributor rows, thus allowing a wide flow rate adjustment range. However, for applications characterized by very low heads and low available powers, it may not be convenient to use complex regulating devices. For this reason, these plants usually use axial machines characterized by a partial regulation (of the distributor or of the rotor), significantly reducing the operating range of the machine compared to the case of double regulation. In the last decade, the development of reliable and less expensive permanent magnet generators and power electronic converters and related new control strategies has paved the way for the concept of regulating hydraulic turbines by means of variable rotational speed. This regulation principle is based on the possibility of acting in the case of using synchronous permanent magnets electric generators and electronic power converters and on the variation of the rotational speed of the machine while keeping the grid frequency constant. The concept can be applied both to pure propellers with fixed a rotor and fixed distributor and to hydraulic axial turbines with regulation based on the modification of the variable guide vane opening angle. Although this new regulation approach, even in the case of the combined guide vane and rotational speed regulation, does not allow to recover most of the energy losses due to the variation of the operating conditions as effectively as the Kaplan double regulation does, the variation of the rotation speed, coupled with the variation of the opening of the distributor row, allows to reduce the tangential kinetic energy losses generated at the turbine exit during the off-design operations of a fixed blade opening angle rotor. At the same time, this type of regulation offers a simple and thus low-cost solution. The present study develops the theory underlying this regulation concept, based on the use of the turbomachinery fundamental equations, and reports the results of the off-design CFD analysis carried out for different combinations of rotation speeds and openings of the distributor, showing the improvement of the hydraulic efficiency over a large range of operating conditions with respect to the single regulation approach. Full article
(This article belongs to the Special Issue 10th Anniversary of Machines—Feature Papers in Turbomachinery)
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12 pages, 930 KiB  
Article
Characterization of the Anomalous Vibration Response of an Intentionally Mistuned LPT Rotor
by Salvador Rodríguez-Blanco and Carlos Martel
Machines 2023, 11(1), 19; https://doi.org/10.3390/machines11010019 - 24 Dec 2022
Cited by 1 | Viewed by 1133
Abstract
The wind tunnel facility at the Centro de Tecnologías Aeronáuticas was used to perform a set of experiments to study the effect of intentional mistuning on the forced response behavior of an aerodynamically unstable low-pressure turbine rotor. The intentional mistuning patterns were implemented [...] Read more.
The wind tunnel facility at the Centro de Tecnologías Aeronáuticas was used to perform a set of experiments to study the effect of intentional mistuning on the forced response behavior of an aerodynamically unstable low-pressure turbine rotor. The intentional mistuning patterns were implemented by adding a small extra mass to some of the blades. The forced response of the rotor was therefore expected to show two resonance peaks with similar amplitudes, corresponding, respectively, to the vibration frequencies of the blades with and without added mass. However, on the post-processing of the measurements, some anomalous behavior was observed. Near resonance, the system response was synchronous with the forcing, and the frequency sweeps exhibited two resonance peaks, but it was found that the two peaks were clearly different, with the peak at lower frequency showing a much higher vibration amplitude than the high-frequency peak, and with some blades responding at both frequencies with a similar amplitude. In order to give a correct interpretation of the experimental results, a reduced-order model is derived that takes into account only the traveling wave modes coupled by the mistuning. This model, although extremely simple, is capable of reproducing the unexpected behavior of the experiments, and gives a clean explanation of the system response. It is shown that the relative size of the mistuning with respect to the frequency difference of the involved traveling-wave modes is the key parameter for the appearance of this phenomenon. Full article
(This article belongs to the Special Issue 10th Anniversary of Machines—Feature Papers in Turbomachinery)
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16 pages, 4977 KiB  
Article
Effects of Laminar, Turbulent, and Slip Conditions in a Fluid Film on a Dry Gas Seal
by Mibbeum Hahn, Youngjun Park, Minsoo Kang, Sanghyun Jun and Gunhee Jang
Machines 2022, 10(10), 954; https://doi.org/10.3390/machines10100954 - 19 Oct 2022
Cited by 2 | Viewed by 1386
Abstract
A dry gas seal is a mechanical seal that prevents leakage of gas from rotating machines utilizing gas as a medium. Fluid film in a dry gas seal can exhibit laminar, turbulent, and slip behavior due to operating conditions and design parameters. A [...] Read more.
A dry gas seal is a mechanical seal that prevents leakage of gas from rotating machines utilizing gas as a medium. Fluid film in a dry gas seal can exhibit laminar, turbulent, and slip behavior due to operating conditions and design parameters. A modified Reynolds equation that considers the effects of laminar, turbulent, and slip behavior of a fluid film was proposed and solved using the finite-element and Newton–Raphson methods to calculate the pressure, opening force, and leakage rate. The accuracy of the developed program was verified by comparing the simulated pressure with that of prior research, and the measured leakage with simulated leakage. The characteristics of a T-groove dry gas seal were investigated according to laminar, turbulent, and slip behavior in the fluid film. The results show that the effects of laminar, turbulent, and slip behavior in a fluid film on a dry gas seal should be considered to accurately predict the characteristics of a dry gas seal. Full article
(This article belongs to the Special Issue 10th Anniversary of Machines—Feature Papers in Turbomachinery)
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