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Advances in Critical Aspects of Turbomachinery Components and Systems

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A special issue of International Journal of Turbomachinery, Propulsion and Power (ISSN 2504-186X).

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 30010

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Prof. Tony Arts

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Guest Editor

Department of Turbomachinery and Propulsion, von Karman Institute for Fluid-Dynamics, Waterloosesteenweg 72, 1640 Sint-Genesius-Rode, Belgium
Interests: aero/thermal aspects (including cooling) of HP gas turbines; aerodynamics of LP gas turbines; measurement methods in turbomachinery; CFD

Dr. Rodolfo Bontempo

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Guest Editor

Dipartimento di Ingegneria Industriale, Università degli Studi di Napoli Federico II, via Cluadio, 21, 80125 Napoli, Italy
Interests: aerodynamics of wind turbines; marine and aeronautical propellers; turbomachinery
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

It is with pleasure that I wish to present this collection of manuscripts from a team of top colleagues affiliated with our field, who also play key roles in its scientific management as editors, reviewers, or as chair-person. The manuscripts will appear in a Special Issue entitled “Advances in Critical Aspects of Turbomachinery Components and Systems” to be published in the International Journal of Turbomachinery Propulsion and Power. IJTPP is an international, peer-reviewed, open access journal on turbomachinery, propulsion and power, owned by Euroturbo, the European Society on Turbomachinery. This IJTPP Special Issue will comprise a collection of high-quality review papers published free of charge by editorial board members and authors invited by the society review chairman, the journal editors, and the editor-in-chief. The objective is to gather the most recent advances in the thermodynamics, the fluid mechanics, the heat-transfer, and the applied combustion of aerospace, marine, and industrial energy devices and turbomachinery-based systems, both from a component and system perspective. Critical aspects requiring major efforts and technological leaps are reviewed and analysed, starting with the state-of-the-art technologies currently available and implemented. The manuscripts address specific subjects among the following topics:

Turbomachinery;
Aerospace propulsion;
Marine propulsion;
Turbochargers;
Power generation;
Thermodynamics;
Fluid mechanics;
Heat transfer;
Vibrations;
Aero-acoustic;
Aero-mechanics;
Applied combustion (aeronautic, aerospace, stationary power systems);
Wind energy;
Marine energy.

Most of the contributions are of the Review-type, although, occasionally, regular research articles are included in the collection.

Prof. Tony Arts
Dr. Rodolfo Bontempo
Guest Editors

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. International Journal of Turbomachinery, Propulsion and Power is an international peer-reviewed open access quarterly 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 1000 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 (11 papers)

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Research

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21 pages, 8469 KiB

Open AccessFeature PaperArticle

Aerodynamics and Sealing Performance of the Downstream Hub Rim Seal in a High-Pressure Turbine Stage

by Filippo Merli, Nicolas Krajnc, Asim Hafizovic, Marios Patinios and Emil Göttlich

Int. J. Turbomach. Propuls. Power 2023, 8(3), 20; https://doi.org/10.3390/ijtpp8030020 - 10 Jul 2023

Viewed by 1178

Abstract

The purpose of the paper is to characterize the aerodynamic behavior of a rotor-downstream hub cavity rim seal in a high-pressure turbine (HPT) stage. The experimental data are acquired in the Transonic Test Turbine Facility at the Graz University of Technology: the test setup includes two engine-representative turbine stages (the last HPT stage and first LPT stage), with the intermediate turbine duct in between. All stator-rotor cavities are supplied with purge flows by a secondary air system, which simulates the bleeding air from the compressor stages of the real engine. The HPT downstream hub cavity is provided with wall taps and pitot tubes at different radial and circumferential locations, which allows the performance of steady pressure and seed gas concentration measurements for different purge mass flows and HPT vanes clocking positions. Moreover, miniaturized pressure transducers are adopted to evaluate the unsteady pressure distribution, and an oil flow visualization is performed to retrieve additional information on the wheel space structures. The annulus pressure asymmetry depends on the HPT vane clocking, but this is shown to have negligible impact on the minimum purge mass flow required to seal the cavity. However, the hub pressure profile drives the distribution of the cavity egress in the turbine channel. The unsteady pressure field is dominated by blade-synchronous oscillations. No non-synchronous components with comparable intensity are detected. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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16 pages, 33987 KiB

Open AccessArticle

Turbomachine Operation with Magnetic Bearings in Supercritical Carbon Dioxide Environment

by Alexander Johannes Hacks and Dieter Brillert

Int. J. Turbomach. Propuls. Power 2022, 7(2), 18; https://doi.org/10.3390/ijtpp7020018 - 14 Jun 2022

Cited by 3 | Viewed by 2686

Abstract

In the sCO2-HeRo project, the Chair of Turbomachinery at the University of Duisburg-Essen developed, built and tested a turbomachine with an integral design in which the compressor, generator and turbine are housed in a single hermetic casing. However, ball bearings limited operation because their lubricants were incompatible with supercritical CO₂ (sCO₂) and they had to operate in gaseous CO₂ instead. To overcome this problem, the turbomachine was redesigned built and tested in the sCO2-4-NPP project. Instead of ball bearings, magnetic bearings are now used to operate the turbomachine with the entire rotor in sCO₂. This paper presents the revised design, focusing on the usage of magnetic bearings. It also investigates whether the sCO₂ limits the operating range. Test runs show that increasing the density and rotational speed results in greater deflection of the rotor and greater forces on the bearings. Measurements are also analyzed with respect to influence of the density increase on the destabilizing forces in the rotor–stator cavities. The conclusion is that for the operation of the turbomachine, the control parameters of the magnetic bearings must be adjusted not only to the rotor speed, but also to the fluid density. This enabled successful operation of the turbomachine, which reached a speed of about 40,000 rpm during initial tests in CO₂. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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21 pages, 3648 KiB

Open AccessArticle

Acoustoelastic Modes in Rotor-Cavity Systems: An Overview on Frequency Shift Effects Supported with Measurements

by Tina Unglaube and Dieter Brillert

Int. J. Turbomach. Propuls. Power 2022, 7(2), 15; https://doi.org/10.3390/ijtpp7020015 - 06 May 2022

Cited by 1 | Viewed by 2524

Abstract

With an increase in fluid densities in centrifugal compressors, fluid-structure interaction and coupled acoustoelastic modes receive growing attention to avoid machine failure. Besides the vibrational behavior of the impeller, acoustic modes building up in the side cavities need to be understood to ensure safe and reliable operation. In a coupled system, these structure and acoustic dominant modes influence each other. Therefore, a comprehensive overview of frequency shift effects in rotor-cavity systems is established based on findings in the literature. Additionally, experimental results on coupled mode pairs in a rotor-cavity test rig with a rotating disk under varying operating conditions are presented. Measurement results for structure dominant modes agree well with theoretical predictions. The development of a forward and a backward traveling wave is demonstrated for each mode in case of disk rotation. Conducted experiments reveal the occurrence of weakly and strongly coupled mode pairs as frequency shifts are observed that cannot solely be explained by “uncoupled mode effects”, such as the added mass, speed of sound, and stiffening effect, but indicate an additional coupling effect. However, the hypothesis of a bigger frequency shift for stronger coupled modes cannot be corroborated consistently. Only for the strongly coupled four nodal diameter mode pair in the “wide cavity” setup, a coupling effect is clearly visible in the form of mode veering. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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Review

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65 pages, 7774 KiB

Open AccessReview

Unsteady Flows and Component Interaction in Turbomachinery

by Simone Salvadori, Massimiliano Insinna and Francesco Martelli

Int. J. Turbomach. Propuls. Power 2024, 9(2), 15; https://doi.org/10.3390/ijtpp9020015 - 05 Apr 2024

Viewed by 681

Abstract

Unsteady component interaction represents a crucial topic in turbomachinery design and analysis. Combustor/turbine interaction is one of the most widely studied topics both using experimental and numerical methods due to the risk of failure of high-pressure turbine blades by unexpected deviation of hot flow trajectory and local heat transfer characteristics. Compressor/combustor interaction is also of interest since it has been demonstrated that, under certain conditions, a non-uniform flow field feeds the primary zone of the combustor where the high-pressure compressor blade passing frequency can be clearly individuated. At the integral scale, the relative motion between vanes and blades in compressor and turbine stages governs the aerothermal performance of the gas turbine, especially in the presence of shocks. At the inertial scale, high turbulence levels generated in the combustion chamber govern wall heat transfer in the high-pressure turbine stage, and wakes generated by low-pressure turbine vanes interact with separation bubbles at low-Reynolds conditions by suppressing them. The necessity to correctly analyze these phenomena obliges the scientific community, the industry, and public funding bodies to cooperate and continuously build new test rigs equipped with highly accurate instrumentation to account for real machine effects. In computational fluid dynamics, researchers developed fast and reliable methods to analyze unsteady blade-row interaction in the case of uneven blade count conditions as well as component interaction by using different closures for turbulence in each domain using high-performance computing. This research effort results in countless publications that contribute to unveiling the actual behavior of turbomachinery flow. However, the great number of publications also results in fragmented information that risks being useless in a practical situation. Therefore, it is useful to collect the most relevant outcomes and derive general conclusions that may help the design of next-gen turbomachines. In fact, the necessity to meet the emission limits defined by the Paris agreement in 2015 obliges the turbomachinery community to consider revolutionary cycles in which component interaction plays a crucial role. In the present paper, the authors try to summarize almost 40 years of experimental and numerical research in the component interaction field, aiming at both providing a comprehensive overview and defining the most relevant conclusions obtained in this demanding research field. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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23 pages, 8359 KiB

Open AccessFeature PaperReview

Turbomachinery Noise Review

by Stéphane Moreau and Michel Roger

Int. J. Turbomach. Propuls. Power 2024, 9(1), 11; https://doi.org/10.3390/ijtpp9010011 - 13 Mar 2024

Viewed by 1013

Abstract

The present paper is aimed at providing an updated review of prediction methods for the aerodynamic noise of ducted rotor–stator stages. Indeed, ducted rotating-blade technologies are in continuous evolution and are increasingly used for aeronautical propulsion units, power generation and air conditioning systems. Different needs are faced from the early design stage to the final definition of a machine. Fast-running, approximate analytical approaches and high-fidelity numerical simulations are considered the best-suited tools for each, respectively. Recent advances are discussed, with emphasis on their pros and cons. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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49 pages, 38463 KiB

Open AccessReview

State of the Art on Two-Phase Non-Miscible Liquid/Gas Flow Transport Analysis in Radial Centrifugal Pumps Part B: Review of Experimental Investigations

by Michael Mansour and Dominique Thévenin

Int. J. Turbomach. Propuls. Power 2023, 8(4), 42; https://doi.org/10.3390/ijtpp8040042 - 13 Oct 2023

Viewed by 1290

Abstract

This paper aims to summarize the results of several experimental investigations regarding two-phase liquid–gas flows in radial centrifugal pumps. The main objective is to combine the corresponding experimental results and collect the obtained knowledge to provide a better understanding of this configuration. The simultaneous transport of the two phases, the phase segregation, and the regions of safe or critical pump performance were described for a wide variety of pump configurations. This review covers single- and two-phase pumping conditions, performance degradation, pump breakdown, performance hysteresis, different flow regimes, flow regime maps, flow instabilities, and surging. This manuscript also considers the influence of employing different pump configurations on pump performance and flow regimes. This includes comparisons between closed and semi-open impellers, standard and increased tip clearance gaps, and running the pump with and without an inducer. Many of the results discussed have been published in a series of research papers. They were all collected, summarized, and compared systematically in the present review. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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50 pages, 8468 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Advanced Gas Turbine Cooling for the Carbon-Neutral Era

by Kenichiro Takeishi and Robert Krewinkel

Int. J. Turbomach. Propuls. Power 2023, 8(3), 19; https://doi.org/10.3390/ijtpp8030019 - 24 Jun 2023

Cited by 3 | Viewed by 4368

Abstract

In the coming carbon-neutral era, industrial gas turbines (GT) will continue to play an important role as energy conversion equipment with high thermal efficiency and as stabilizers of the electric power grid. Because of the transition to a clean fuel, such as hydrogen or ammonia, the main modifications will lie with the combustor. It can be expected that small and medium-sized gas turbines will burn fewer inferior fuels, and the scope of cogeneration activities they are used for will be expanded. Industrial gas turbine cycles including CCGT appropriate for the carbon-neutral era are surveyed from the viewpoint of thermodynamics. The use of clean fuels and carbon capture and storage (CCS) will inevitably increase the unit cost of power generation. Therefore, the first objective is to present thermodynamic cycles that fulfil these requirements, as well as their verification tests. One conclusion is that it is necessary to realize the oxy-fuel cycle as a method to utilize carbon-heavy fuels and biomass and not generate NO_x from hydrogen combustion at high temperatures. The second objective of the authors is to show the required morphology of the cooling structures in airfoils, which enable industrial gas turbines with a higher efficiency. In order to achieve this, a survey of the historical development of the existing cooling methods is presented first. CastCool^® and wafer and diffusion bonding blades are discussed as turbine cooling technologies applicable to future GTs. Based on these, new designs already under development are shown. Most of the impetus comes from the development of aviation airfoils, which can be more readily applied to industrial gas turbines because the operation will become more similar. Double-wall cooling (DWC) blades can be considered for these future industrial gas turbines. It will be possible in the near future to fabricate the DWC structures desired by turbine cooling designers using additive manufacturing (AM). Another conclusion is that additively manufactured DWC is the best cooling technique for these future gas turbines. However, at present, research in this field and the data generated are scattered, and it is not yet possible for heat transfer designers to fabricate cooling structures with the desired accuracy. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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22 pages, 5782 KiB

Open AccessFeature PaperReview

State of the Art on Two-Phase Non-Miscible Liquid/Gas Flow Transport Analysis in Radial Centrifugal Pumps-Part A: General Considerations on Two-Phase Liquid/Gas Flows in Centrifugal Pumps

by Gerard Bois

Int. J. Turbomach. Propuls. Power 2023, 8(2), 16; https://doi.org/10.3390/ijtpp8020016 - 10 May 2023

Cited by 2 | Viewed by 1429

Abstract

Gas–liquid mixtures are present in numerous industrial applications, such as in the process industry, oil production and transport with natural gas, deep-sea extraction, and irrigation. Any pump may have to carry multiphase flows. However, the present document is related to non-miscible liquid/gas flow transport analysis in centrifugal pumps because which topic can be a more challenging task compared with axial and mixed flow machines due to specific body force and buoyancy actions and large density differences between the phases. The present document first introduces the main usual gas–liquid two-phase definitions and simplifications. A dimensional analysis introduces the main flow variables and parameters that are used for pumps. Basic physical aspects of flow motion in an impeller channel are explained, and a rapid description of two-phase flow patterns in radial flow pumps is described. Finally, a review of simplified empirical and semi-empirical analytical models is proposed with their limitations. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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23 pages, 2539 KiB

Open AccessFeature PaperEditor’s ChoiceReview

State of the Art on Two-Phase Non-Miscible Liquid/Gas Flow Transport Analysis in Radial Centrifugal Pumps Part C: CFD Approaches with Emphasis on Improved Models

by Markus Hundshagen and Romuald Skoda

Int. J. Turbomach. Propuls. Power 2023, 8(2), 15; https://doi.org/10.3390/ijtpp8020015 - 04 May 2023

Cited by 3 | Viewed by 2341

Abstract

Predicting pump performance and ensuring operational reliability under two-phase conditions is a major goal of three-dimensional (3D) computational fluid dynamics (CFD) analysis of liquid/gas radial centrifugal pump flows. Hence, 3D CFD methods are increasingly applied to such flows in academia and industry. The CFD analysis of liquid/gas pump flows demands careful selection of sub-models from several fields in CFD, such as two-phase and turbulence modeling, as well as high-quality meshing of complex geometries. This paper presents an overview of current CFD simulation strategies, and recent progress in two-phase modeling is outlined. Particular focus is given to different approaches for dispersed bubbly flow and coherent gas accumulations. For dispersed bubbly flow regions, Euler–Euler Two-Fluid models are discussed, including population balance and bubble interaction models. For coherent gas pocket flow, essentially interface-capturing Volume-of-Fluid methods are applied. A hybrid model is suggested, i.e., a combination of an Euler–Euler Two-Fluid model with interface-capturing properties, predicting bubbly flow regimes as well as regimes with coherent gas pockets. The importance of considering scale-resolving turbulence models for highly-unsteady two-phase flow regions is emphasized. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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40 pages, 10585 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Experimental Investigation Techniques for Non-Ideal Compressible Fluid Dynamics

by Stefan aus der Wiesche

Int. J. Turbomach. Propuls. Power 2023, 8(2), 11; https://doi.org/10.3390/ijtpp8020011 - 03 Apr 2023

Cited by 2 | Viewed by 2633

Abstract

The rising number of applications of the organic Rankine cycle (ORC) or supercritical CO₂ (sCO₂) power systems have shaped a new branch of fluid mechanics called non-ideal compressible fluid dynamics (NICFD). This field of fluid mechanics is concerned with flows of vapors or gases, which are characterized by substantial deviations from the perfect gas model. In extreme cases, even non-classical gas dynamic phenomena could occur. Although these non-ideal compressible flows are the subject of sophisticated numerical simulation studies today, there is also a growing need for experimental data for validating purposes. In the last couple of years, new experimental test rigs designed for investigating non-ideal compressible fluid dynamics have been developed and commissioned. Classical practical measurement techniques are currently being re-developed and applied to non-ideal compressible flows. Despite its substantial relevance, information about these measurement techniques and their differences from conventional methods in the open literature is scarce. The present review article is an attempt to reduce that gap. After briefly discussing the thermodynamics and fluid dynamics of non-ideal compressible flows, the currently available test rigs and their utilized measurement techniques are reviewed. This review discusses schlieren optical investigations, pneumatic and laser-optical methods, and hot-wire anemometry for non-ideal compressible flows. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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24 pages, 1801 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Machine Learning Methods in CFD for Turbomachinery: A Review

by James Hammond, Nick Pepper, Francesco Montomoli and Vittorio Michelassi

Int. J. Turbomach. Propuls. Power 2022, 7(2), 16; https://doi.org/10.3390/ijtpp7020016 - 13 May 2022

Cited by 16 | Viewed by 8369

Abstract

Computational Fluid Dynamics is one of the most relied upon tools in the design and analysis of components in turbomachines. From the propulsion fan at the inlet, through the compressor and combustion sections, to the turbines at the outlet, CFD is used to perform fluid flow and heat transfer analyses to help designers extract the highest performance out of each component. In some cases, such as the design point performance of the axial compressor, current methods are capable of delivering good predictive accuracy. However, many areas require improved methods to give reliable predictions in order for the relevant design spaces to be further explored with confidence. This paper illustrates recent developments in CFD for turbomachinery which make use of machine learning techniques to augment prediction accuracy, speed up prediction times, analyse and manage uncertainty and reconcile simulations with available data. Such techniques facilitate faster and more robust searches of the design space, with or without the help of optimization methods, and enable innovative designs which keep pace with the demand for improved efficiency and sustainability as well as parts and asset operation cost reduction. Full article

(This article belongs to the Special Issue Advances in Critical Aspects of Turbomachinery Components and Systems)

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