International Journal of Turbomachinery, Propulsion and Power

27 pages, 13828 KB

Open AccessArticle

Pushing the Limits: Enhancing Turbomachinery Efficiency by Riblet Application

by Konrad M. Hartung, Stefan Mauersberger, Udo Löschner and Karsten Oehlert

Int. J. Turbomach. Propuls. Power 2026, 11(2), 22; https://doi.org/10.3390/ijtpp11020022 - 15 May 2026

The reduction in aerodynamic drag remains a crucial pathway for enhancing turbomachinery efficiency. Riblet structures are a well-established passive technique to reduce viscous drag, but their application has been constrained by the challenge of adapting size and orientation to match the local flow [...] Read more.

The reduction in aerodynamic drag remains a crucial pathway for enhancing turbomachinery efficiency. Riblet structures are a well-established passive technique to reduce viscous drag, but their application has been constrained by the challenge of adapting size and orientation to match the local flow conditions. This study presents a novel laser-based fabrication process developed at the Laserinstitut Hochschule Mittweida, which enables the production of continuously adapted riblets on complex curved surfaces. Numerical simulations were employed to design riblet patterns for the NACA0012 airfoil at zero angle of attack, followed by laser manufacturing and high-resolution surface characterization. Aerodynamic performance was evaluated through wake surveys in a Göttingen-type wind tunnel at the Jade University of Applied Sciences. The results validate the numerical design approach and show that tailored riblet structures provide a notable improvement in drag reduction compared to constant geometries, with relative gains of about

8 %

for the one-sided and

16 %

for the two-sided application. These findings underline the potential of advanced laser-based manufacturing processing to enable riblet integration in turbomachinery under industrially relevant conditions. Full article

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20 pages, 3405 KB

Open AccessArticle

Improving Pressure Buildup and Water Purity in a PTJ Separation Pump

by Jessica Dafis, Xuemei Zhang, Katharina Zähringer and Dominique Thévenin

Int. J. Turbomach. Propuls. Power 2026, 11(2), 21; https://doi.org/10.3390/ijtpp11020021 - 14 May 2026

Abstract

A modified Pitot-tube jet (PTJ) separation pump combines centrifugal phase separation with pressure buildup and enables compact oil–water treatment, where a water-rich stream can be discharged at elevated pressure. This work advances an existing laboratory PTJ configuration toward a turbomachinery-oriented rotor concept for [...] Read more.

A modified Pitot-tube jet (PTJ) separation pump combines centrifugal phase separation with pressure buildup and enables compact oil–water treatment, where a water-rich stream can be discharged at elevated pressure. This work advances an existing laboratory PTJ configuration toward a turbomachinery-oriented rotor concept for systematic design studies and subsequent field-oriented prototypes. Starting from a centrifuge-like reference configuration without blades that prioritizes separation stability, an impeller with trimmed blades is introduced to increase pressure head while limiting blade interaction with the oil–water interface by operating primarily in the outer, water-rich annulus. Comparative experiments with and without the impeller show a pronounced increase in pressure head, up to about a factor of three at the maximum speed investigated. The results also indicate a purity penalty caused by blade-induced mixing and secondary flows. This exposes the central design trade-off of the PTJ machine. Higher specific work input increases pressure head but can reduce discharge quality. Hydraulic optimization, therefore, needs to be coupled to ppm-level purity constraints. Density-based monitoring lacks resolution in the relevant trace range, and chemical-based analyses are too slow for systematic investigations. An imaging-based fluorescence method using Nile Red as a selective tracer is, therefore, implemented as a rapid analysis tool. High-resolution imaging with automated region of interest evaluation provides a robust calibration from 5–500 ppm for safe, non-fluorescent model oils such as sunflower oil. This enables efficient operating-window mapping and comparative screening of rotor concepts under reproducible conditions. Full article

(This article belongs to the Special Issue Selected Papers from the Conference on Modelling Fluid Flow (CMFF’25))

17 pages, 609 KB

Open AccessArticle

Calculation of Total Tone-to-Noise Ratio and Total Prominence Ratio for Small Fan Noise and Determination of Subjective Annoyance Thresholds

by Takefumi Nakano and Gaku Minorikawa

Int. J. Turbomach. Propuls. Power 2026, 11(2), 20; https://doi.org/10.3390/ijtpp11020020 - 12 May 2026

Abstract

Fan noise from small cooling fans often contains multiple coexisting tonal components whose combined perceptual impact cannot be fully represented by conventional single-tone metrics. While the Tone-to-Noise Ratio (TNR) and Prominence Ratio (PR) defined in ECMA-418-1 are established measures for evaluating individual tonal [...] Read more.

Fan noise from small cooling fans often contains multiple coexisting tonal components whose combined perceptual impact cannot be fully represented by conventional single-tone metrics. While the Tone-to-Noise Ratio (TNR) and Prominence Ratio (PR) defined in ECMA-418-1 are established measures for evaluating individual tonal components, their direct application under multi-tone conditions may be insufficient to characterize cumulative tonal influence. To address this issue, the Total Tone-to-Noise Ratio (TTNR) and the Total Prominence Ratio (TPR) have been proposed as cumulative extensions of the ECMA framework. In this study, calculation procedures for TTNR and TPR were systematically examined for projector operating noise containing multiple tonal components, and subjective annoyance thresholds were determined using controlled jury ranking tests with 20 participants. Detection parameters for tonal extraction were adjusted within the ECMA-418-1 framework to reflect realistic product conditions. The resulting annoyance thresholds were 11.6 dB for TTNR and 14.3 dB for TPR. These findings indicate that cumulative tonal evaluation can be performed within the existing standardized framework and that TTNR and TPR provide practical tools for assessing multi-tone noise in technical products equipped with small cooling fans. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

19 pages, 1599 KB

Open AccessArticle

A Performance Analysis of a Fuel Cell Propulsion System with Micro Gas Turbine Under Realistic Environmental Conditions

by Sebastian Lück, Maximilian Bień, Patrick Meyer, Jens Friedrichs and Jan Göing

Int. J. Turbomach. Propuls. Power 2026, 11(2), 19; https://doi.org/10.3390/ijtpp11020019 - 14 Apr 2026

Abstract

A major challenge for aircraft fuel cell propulsion systems is to ensure that the air properties on the cathode side remain within a narrow, suitable envelope throughout the flight. The components must maintain almost constant temperature, pressure and humidity levels under widely varying [...] Read more.

A major challenge for aircraft fuel cell propulsion systems is to ensure that the air properties on the cathode side remain within a narrow, suitable envelope throughout the flight. The components must maintain almost constant temperature, pressure and humidity levels under widely varying ambient conditions. The choice of components must take into account the aviation-specific requirements for weight and waste heat. In this numerical study, we investigate a novel cathode air supply system for a hydrogen fuel cell propulsion system which replaces the state-of-the-art electrical components used to drive the compressor in the cathode air supply system with a hydrogen-fuelled micro gas turbine. Previous studies have shown the potential of waste heat and overall cathode gas path size reduction but the off-design performance of such system is yet to be investigated. Hence, based on realistic regional aircraft flight missions and realistic atmospheric conditions, we investigate the off-design performance of the propulsion system. Therefore, a constant mass flow algorithm along cathode and gas turbine gas paths is developed and presented. Next, earth observation data are used to determine realistic boundary conditions and air contamination. Based on these data, the possible contaminant ingestion of the fuel cell is evaluated to allow for future sizing of filters for robust operation. Furthermore, the effects of realistic ambient conditions on the thermodynamic cycle yield important information about necessary revisions of the cycle design point. Full article

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18 pages, 7291 KB

Open AccessArticle

Optimising Blade Profiles to Extend the Operating Range in BLI Fan Application

by Andrea Magrini and Ernesto Benini

Int. J. Turbomach. Propuls. Power 2026, 11(2), 18; https://doi.org/10.3390/ijtpp11020018 - 6 Apr 2026

Abstract

Boundary Layer Ingestion propulsors operate in an adverse aerodynamic environment with high levels of distortion. With the purpose of extending the operating range of transonic fan rotors for BLI applications, in this paper we present an optimisation study focused on blade profiles design [...] Read more.

Boundary Layer Ingestion propulsors operate in an adverse aerodynamic environment with high levels of distortion. With the purpose of extending the operating range of transonic fan rotors for BLI applications, in this paper we present an optimisation study focused on blade profiles design under different working conditions. Quasi-2D blade sections are optimised using a genetic algorithm and numerical simulations, by varying the camberline and thickness distribution. A method to efficiently achieve a combination of total pressure ratio at a given relative inlet Mach number is devised. The isentropic efficiency is optimised at the design point, concurrently with the stall total pressure ratio at a lower inlet Mach number, in a multi-objective fashion. Pareto-optimal profiles exhibit a moderate leading edge concavity for high efficiency and a straighter fore part with increased trailing edge deflection for higher compression at stall. Optimised airfoils are used in a preliminary three-dimensional evaluation with a realistic BLI inflow, in which the unsteady full-annulus analysis corroborates the approach of the sectional optimisation, also showing the possibility of estimating the integral performance of the machine with a simplified approach based on a single-passage simulation with a circumferential-averaged inflow distribution. Full article

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15 pages, 3240 KB

Open AccessArticle

Aeroacoustic Prediction and Optimization of Unevenly Spaced Blades in Axial Fans

by Samir Assaf, Thibaut Gras and Jacques Ferhat

Int. J. Turbomach. Propuls. Power 2026, 11(2), 17; https://doi.org/10.3390/ijtpp11020017 - 4 Apr 2026

Abstract

A common solution for reducing the tonal noise annoyance caused by fans is to change the circumferential blade spacing from even to uneven. However, this technique requires predictive tools to simulate and assess their acoustic performance at a lower cost compared to experimental [...] Read more.

A common solution for reducing the tonal noise annoyance caused by fans is to change the circumferential blade spacing from even to uneven. However, this technique requires predictive tools to simulate and assess their acoustic performance at a lower cost compared to experimental tests, which remain very costly. In this study, a hybrid analytic/numeric (HAN) approach for predicting the tonal noise of fans is proposed. It is based on the acoustic interference law, which is applied to the sound pressure generated by each blade, and Computational Aeroacoustics (CAA). This model allows for the analytical construction of a fan’s acoustic pressure spectrum from the numerically computed response of a single blade, significantly reducing computation time. An optimization procedure is then implemented to minimize the prominence of tonal noise peaks, where the decision variables are the blades’ angular positions and the constraints are rotor balance and the minimum angular distance between adjacent blades. The results show that the developed method may help designers reduce tonal noise annoyance by optimizing blade spacing. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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14 pages, 7343 KB

Open AccessArticle

Experimental Investigation of Shock Boundary/Layer Interaction on a Fan Profile Under Various Inlet Conditions

by Ahmed H. Hanfy, Piotr Kaczynski, Piotr Doerffer and Pawel Flaszynski

Int. J. Turbomach. Propuls. Power 2026, 11(2), 16; https://doi.org/10.3390/ijtpp11020016 - 3 Apr 2026

Abstract

Transonic compressors encounter significant challenges from shock formations due to high-speed supersonic blade tips, particularly at high altitudes where lower Reynolds numbers result in laminar boundary layer separation and increased mixing losses. Understanding shock wave–boundary layer interaction (SBLI) is essential for improving compressor [...] Read more.

Transonic compressors encounter significant challenges from shock formations due to high-speed supersonic blade tips, particularly at high altitudes where lower Reynolds numbers result in laminar boundary layer separation and increased mixing losses. Understanding shock wave–boundary layer interaction (SBLI) is essential for improving compressor performance. This study examines SBLI under varying Reynolds numbers, simulating higher altitude conditions in a transonic blow-down wind tunnel. Using an inlet valve setup to control inflow total pressure and Reynolds numbers, this study also reveals an increase in turbulence. The findings indicate that laminar-to-turbulent transition occurs upstream of the shock wave, resulting in interaction with a turbulent boundary layer, even at lower Reynolds numbers. Full article

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11 pages, 2532 KB

Open AccessArticle

Numerical Investigation of Scaling Effects on the Performance Characteristics of Large-Scale Axial-Flow Fans

by Tristan Oliver Le Roux, Chris Meyer and Sybrand Johannes van der Spuy

Int. J. Turbomach. Propuls. Power 2026, 11(1), 15; https://doi.org/10.3390/ijtpp11010015 - 3 Mar 2026

Abstract

Large-diameter axial-flow fans are predominantly used for cooling purposes, such as in air-cooled heat exchangers. Since it is difficult to experimentally test large-scale fans in the controlled environments provided by fan test facilities, smaller scaled-down versions of the fans are tested instead. Scaling [...] Read more.

Large-diameter axial-flow fans are predominantly used for cooling purposes, such as in air-cooled heat exchangers. Since it is difficult to experimentally test large-scale fans in the controlled environments provided by fan test facilities, smaller scaled-down versions of the fans are tested instead. Scaling laws, also called affinity laws, are then used to determine the performance characteristics of the large-scale fan. The size difference between the two scaled fans means that it is not possible to match their Reynolds numbers when testing with the same test fluid. A comparison is conducted using experimental results and four numerical models for two different fans, which are scaled to different fan sizes: 0.63 m, 1.542 m, 3.658 m and 7.315 m, to determine the effect of Reynolds number on the performance characteristics of an axial-flow fan. The numerical geometries are based on the M- and B2a-fans, and are tested in the A-type experimental setup fan test facility at Stellenbosch University, which is used to obtain the experimental results. It was found that the numerical approach discussed within this paper, namely a Reynolds-Averaged Navier–Stokes (RANS) approach, can predict the performance of multiple fan sizes without relying on turbomachinery or blade-specific empirical correlations. This approach accelerates the evaluation of fan performance while enabling the parameterization of fan configurations. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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35 pages, 7822 KB

Open AccessFeature PaperArticle

Off-Design Aerodynamics of the SPLEEN C1 Cascade

by Gustavo Lopes, Loris Simonassi, Antonino Federico Maria Torre, Marios Patinios and Sergio Lavagnoli

Int. J. Turbomach. Propuls. Power 2026, 11(1), 14; https://doi.org/10.3390/ijtpp11010014 - 2 Mar 2026

Abstract

High-speed, low-pressure turbines in geared turbofans operate at transonic exit Mach numbers and low Reynolds numbers. Engine-relevant data remain scarce. The SPLEEN C1 linear cascade was investigated at

M_{out} = 0.70 - 0.95

and

R e_{out} = 65,000 - 120,000

under [...] Read more.

High-speed, low-pressure turbines in geared turbofans operate at transonic exit Mach numbers and low Reynolds numbers. Engine-relevant data remain scarce. The SPLEEN C1 linear cascade was investigated at

M_{out} = 0.70 - 0.95

and

R e_{out} = 65,000 - 120,000

under steady inlet flow. Experiments were combined with 2D RANS and MISES, including transition modeling and inlet-turbulence decay calibrated to measurements. Results are consistent with conventional LPT behavior: loss decreased with increasing Mach and Reynolds numbers, except when shocks interacted with the blade boundary layer (

M \approx 0.95

). Profile loss dropped by

23 %

from

M = 0.70

to

0.95

at

R e = 70,000

, as well as by

19 %

at

M = 0.80

when open separation is suppressed. Secondary loss decreased by up to

25 %

at

R e = 70,000

and showed weak sensitivity to the Reynolds number. A coupled loss model predicted profile loss with a root-mean square error of 4.7%. Secondary-loss modeling reproduced global trends: separating endwall dissipation from mixing kept errors within

\pm 10 %

for most cases, but accuracy degraded near the shock–boundary layer interaction case and at the highest Reynolds number. Mixing dominated endwall loss (∼75%), with the passage vortex contributing ∼50% (±10%) of the mixing component. Full article

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20 pages, 8888 KB

Open AccessFeature PaperArticle

Two-Dimensional Flow in a Linear Cascade of Throttling Nozzles for an Adaptive Turbine Stage

by Reinhard Willinger, Khoiri Rozi and Mohammad Reza Kariman

Int. J. Turbomach. Propuls. Power 2026, 11(1), 13; https://doi.org/10.3390/ijtpp11010013 - 2 Mar 2026

Abstract

Steam turbines with controlled extraction require a flow control device to keep extraction pressure constant when the extraction mass flow rate is changed. An attractive option is an adaptive turbine stage with throttling nozzles. Flow measurements with a throttling nozzle are performed in [...] Read more.

Steam turbines with controlled extraction require a flow control device to keep extraction pressure constant when the extraction mass flow rate is changed. An attractive option is an adaptive turbine stage with throttling nozzles. Flow measurements with a throttling nozzle are performed in a cascade wind tunnel. A linear cascade with seven blades is operated at an inlet flow angle of 90° and an exit Reynolds number of about 4 × 10⁵. Since the maximum exit Mach number is about 0.2, flow is essentially incompressible. A three-hole pressure probe is traversed at half span over one blade pitch 0.33 axial chord lengths downstream of the cascade. Degree of closing is gradually changed from zero (fully open) to 0.3 (partially closed). Two principal options, closing to the suction side as well as closing to the pressure side, are investigated. Local flow quantities as well as pitchwise mass averaged quantities are extracted from the measurement data. The major outcomes are as follows: If the throttling nozzle is closed, depth and width of the blade wake increase. With increasing degree of closing, pitchwise mass averaged flow angle decreases and total pressure losses increase. Concerning total pressure losses, closing to the pressure side is the preferred option. A semi-empirical flow model is presented to explain the influence of degree of closing on exit flow angle and total pressure loss. Full article

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17 pages, 15745 KB

Open AccessArticle

The Influence of Hub Purge Flow Rate on Forced Response in a Low-Pressure Turbine

by Alexander Trafford, Sina Stapelfeldt, Gustavo Lopes and Sergio Lavagnoli

Int. J. Turbomach. Propuls. Power 2026, 11(1), 12; https://doi.org/10.3390/ijtpp11010012 - 2 Mar 2026

Abstract

We present the results of a computational investigation into the influence of hub purge flow mass flow rate on the forcing amplitudes generated on a low-pressure turbine (LPT) rotor cascade by the upstream stator vane passing (SVP). Forcing of this kind is a [...] Read more.

We present the results of a computational investigation into the influence of hub purge flow mass flow rate on the forcing amplitudes generated on a low-pressure turbine (LPT) rotor cascade by the upstream stator vane passing (SVP). Forcing of this kind is a major driver of high cycle fatigue (HCF) in turbines; however, the influence of hub purge flow, which is mandatory to seal cavities between stationary and rotating rows in turbines and to protect working components from excessively high temperatures, is minimally understood. This study was carried out via time-accurate unsteady aeroelastic simulations of the SPLEEN turbine cascade and is validated against the extensive database of test results obtained for this geometry at the Von Karman Institute for Fluid Dynamics. The effect of purge mass flow rates of

0.5 %

and

0.9 %

of the main passage flow are evaluated through measurement of the blade’s unsteady pressure and modal force at the SVP and compared to the nominal ‘no purge’ case. The introduction of purge flow was shown to reduce the amplitude of the unsteady pressure signal on the blade surface at the hub. However, a change in the phase of the unsteady pressure on certain portions of the blade could still bring about an increase in modal force for certain modes. Full article

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15 pages, 6104 KB

Open AccessArticle

Topology Optimization for Internal Cooling of Gas Turbine Guide Vanes—A Conjugate Heat Transfer Study

by Hossein Nadali Najafabadi, Sadegh Fattahi, Jonas Lundgren and Carl-Johan Thore

Int. J. Turbomach. Propuls. Power 2026, 11(1), 11; https://doi.org/10.3390/ijtpp11010011 - 13 Feb 2026

Abstract

This study explores the feasibility and validity of using topology optimization (TO) to design the internal cooling of an airfoil-like geometry approximating a turbine guide vane. A conjugate heat transfer approach where the fluid flow physics are coupled with a convection–diffusion model for [...] Read more.

This study explores the feasibility and validity of using topology optimization (TO) to design the internal cooling of an airfoil-like geometry approximating a turbine guide vane. A conjugate heat transfer approach where the fluid flow physics are coupled with a convection–diffusion model for heat transfer is used in the TO. The objective is to minimize the maximum temperature on the outer surface of the vane with a constraint on the mass flow of the internal coolant. Two different flow models are investigated for the TO process: the Stokes model and the Reynolds-Averaged Navier–Stokes (RANS) equations with a simple zero-equation turbulence model. Velocity and temperature fields in topology-optimized designs are then compared to conventional conjugate heat transfer analyses performed on post-processed designs with body-fitted meshes and those using the shear stress transport (SST) RANS turbulence model. Designs obtained with the Stokes model exhibit different flow trajectories and mixing, while the use of RANS equations improves predictions but introduces uncertainties due to turbulence modeling limitations, particularly in the presence of flow separation. Thus, considering these limitations, the findings suggest that a simple flow model, such as Stokes in TO, with a comparatively low computational cost, can yield useful design concepts. However, the simplifications in the governing equations and their impact on physics should be considered carefully, and further aerothermal validation is required. Thus, the study findings, along with advances in robust meshing, enhance the practicality of topology optimization for industrial applications. Full article

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15 pages, 85864 KB

Open AccessFeature PaperArticle

An Overview of the Benchmark Case for the Aeroacoustics and Structural Acoustics of an Enclosed Centrifugal Fan

by Felix Czwielong, Patrick Heidegger, Manuel Lauber, Christoph Heigl, Andreas Wurzinger, Marco Fritzsche, Stefan Schoder, Manfred Kaltenbacher and Stefan Becker

Int. J. Turbomach. Propuls. Power 2026, 11(1), 10; https://doi.org/10.3390/ijtpp11010010 - 3 Feb 2026

Abstract

As part of a joint research project between the Institute of Fluid Mechanics (LSTM) and the Institute of Fundamentals and Theory of Electrical Engineering (IGTE), an international benchmark case for fluid–structure–acoustic interaction was developed. The research focused on an enclosed centrifugal fan, and [...] Read more.

As part of a joint research project between the Institute of Fluid Mechanics (LSTM) and the Institute of Fundamentals and Theory of Electrical Engineering (IGTE), an international benchmark case for fluid–structure–acoustic interaction was developed. The research focused on an enclosed centrifugal fan, and its aerodynamic, aeroacoustic and structure–acoustic properties were characterised through experimental measurements. This paper provides an overview of the centrifugal fan, its enclosure and the test rig used for the experimental investigations. Rather than interpreting the results, the focus is on presenting the benchmark case and providing an overview of the available data. The entire benchmark dataset is listed and freely accessible via the Zenodo European platform in the EAA benchmark data collection. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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26 pages, 10140 KB

Open AccessArticle

Experimental and Numerical Characterization of the Stable Operating Range of a Highly Loaded Axial Compressor Stage

by Riccardo Toracchio, Koen Hillewaert and Fabrizio Fontaneto

Int. J. Turbomach. Propuls. Power 2026, 11(1), 8; https://doi.org/10.3390/ijtpp11010008 - 3 Feb 2026

Abstract

High-bypass ratio engines are currently among the most investigated solutions to achieve efficiency benefits and noise reduction in gas turbine engines. When equipped with a gearbox, these engines enable an optimized operation of the fan and of the low-pressure core, resulting in reduced [...] Read more.

High-bypass ratio engines are currently among the most investigated solutions to achieve efficiency benefits and noise reduction in gas turbine engines. When equipped with a gearbox, these engines enable an optimized operation of the fan and of the low-pressure core, resulting in reduced weight and fuel consumption. The higher spool speed allows higher pressure ratios per stage, and consequently a reduced stage count. However, all this contributes to an enhanced sensitivity of the engine components to the development of secondary flow structures and separations, with a consequent impact on the aerodynamic performance and stability. In this context, an experimental campaign was conducted at the von Karman Institute for Fluid Dynamics on a highly loaded axial compressor representative of the first stage of a modern booster. The aim was to identify the flow features responsible of the performance loss at the operating points and speeds considered more critical in terms of rotor inlet incidence. To this end, time-averaged instrumentation was employed to characterize the performance and to retrieve the distribution of flow quantities at different axial positions within the stage, while fast-response probes allowed for the detailed characterization of the rotor outlet flow field. Unsteady 3D simulations complemented the experimental results and supported this interpretation, especially in regions with limited instrumentation access. The experimental and numerical results emphasized the role of the secondary flow structures developing near the hub wall as the main drivers for aerodynamic stall, due to the enhanced loading in this blade region. Full article

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18 pages, 8380 KB

Open AccessFeature PaperArticle

An Experimental and Numerical Investigation into Compressor Casing Heat Shield Effectiveness

by Andrew Pilkington, Vinod Gopalkrishna, Christopher Barnes, Leo Lewis and Marko Bacic

Int. J. Turbomach. Propuls. Power 2026, 11(1), 9; https://doi.org/10.3390/ijtpp11010009 - 2 Feb 2026

Abstract

An investigation was conducted into the effectiveness of heat shields in an aero-engine compressor casing to slow down thermal time constants. The investigation used a combination of experimental measurements from a full-size compressor casing rig, combined with numerical analysis using CFD and thermal [...] Read more.

An investigation was conducted into the effectiveness of heat shields in an aero-engine compressor casing to slow down thermal time constants. The investigation used a combination of experimental measurements from a full-size compressor casing rig, combined with numerical analysis using CFD and thermal modelling. Experiments were performed on a compressor casing both with and without heat shielding in order to determine the heat shield effectiveness. Temperature measurements were taken throughout the casing in order to determine the thermal time constants. The experimental data was then used to validate a thermal model and CFD simulations of the compressor casing. The modelling allowed the heat transfer coefficients in the compressor casing to be determined from the experimentally measured time constants. It was found that the heat shields gave an increase in thermal time constant at each measured location. With a doubling in the time constant at some locations compared to the unshielded case. It was also found that the heat shields need to be fully sealed, as leakage flows significantly reduce their effectiveness. Full article

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16 pages, 4019 KB

Open AccessArticle

On the Impact of the Off-Design Operating Condition on the Thermal Performance of Rotor Platform Cooling

by Giovanna Barigozzi, Giovanni Brumana, Nicoletta Franchina and Elisa Ghirardi

Int. J. Turbomach. Propuls. Power 2026, 11(1), 7; https://doi.org/10.3390/ijtpp11010007 - 8 Jan 2026

Abstract

In the present work, off-design operating condition is considered to be the ability of the turbine to operate down to 50% to 20% of its nominal intake air flow rate. An important consequence of these off-design points is the change in the inlet [...] Read more.

In the present work, off-design operating condition is considered to be the ability of the turbine to operate down to 50% to 20% of its nominal intake air flow rate. An important consequence of these off-design points is the change in the inlet incidence angle, which varied from nominal to −20°. Tests were performed on a seven-blade rotor cascade with platform cooling through an upstream slot simulating the stator-to-rotor interface gap. To model the impact of rotation on purge flow injection, a set of fins were installed inside the slot to give the coolant flow a tangential direction. Different cascades’ off-design operating conditions were tested, covering downstream velocity values up to Ma_2is = 0.55, with two inlet turbulence intensity levels of 0.6% a and 7%. A thermal measurement campaign was conducted with the Thermochromic Liquid Crystal technique to measure the adiabatic film cooling effectiveness at various coolant-to-main-flow mass flow ratios, different incidence angles, mainstream Mach numbers, and turbulence levels. The results describe the complexity of the turbine operating under off-design operating conditions, relating the improvement in the platform thermal protection to the reduced secondary-flows activity induced by negative incidence. Full article

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19 pages, 2053 KB

Open AccessArticle

Aerodynamics of Short Intake at High Incidence

by Fernando Tejero, David MacManus, Josep Hueso-Rebassa, Yuri Frey Marioni and Ian Bousfield

Int. J. Turbomach. Propuls. Power 2026, 11(1), 6; https://doi.org/10.3390/ijtpp11010006 - 5 Jan 2026

Abstract

This work assesses the aerodynamics of a short aero-engine intake for a new rig that is planned to be tested at the Large Low-Speed Facility of the German Dutch Wind Tunnels (LLF-DNW) in 2025. A range of computations were performed to assess whether [...] Read more.

This work assesses the aerodynamics of a short aero-engine intake for a new rig that is planned to be tested at the Large Low-Speed Facility of the German Dutch Wind Tunnels (LLF-DNW) in 2025. A range of computations were performed to assess whether the expected aerodynamics in this arrangement encompass the envisaged range of flow field characteristics of the equivalent isolated configuration. The effect of massflow capture ratio and angle of attack are investigated. In addition, an intake flow separation taxonomy is proposed to characterise the associated flows. The wind tunnel analysis is based on two different modelling approaches: an aspirated isolated intake and a coupled fan–intake configuration. The coupled configuration uses a full-annulus model with a harmonic mixing plane method. Across the range of operating conditions with changes in the massflow capture ratio and angle of attack, there are attached and separated flows. The main separation mechanisms are diffusion-driven and shock-induced, which shows the different aerodynamics that may be encountered in a short intake. Overall, this work provides an initial evaluation of the aerodynamics of the new fan/intake test rig configuration, provides guidance for wind tunnel testing, and lays a foundation for subsequent unsteady coupled fan–intake studies. Full article

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12 pages, 7536 KB

Open AccessFeature PaperArticle

On the Effect of Tip Flow on the Noise of a Ducted Rotor

by Jose Rendón-Arredondo and Stéphane Moreau

Int. J. Turbomach. Propuls. Power 2026, 11(1), 5; https://doi.org/10.3390/ijtpp11010005 - 5 Jan 2026

Abstract

This study focuses on the aeroacoustic aspects of ducted rotors that could possibly be used in future electrically driven helicopter tail rotor systems. It provides a comprehensive understanding of the tip flow evolution, and of the interaction with the stator stage. High-fidelity compressible [...] Read more.

This study focuses on the aeroacoustic aspects of ducted rotors that could possibly be used in future electrically driven helicopter tail rotor systems. It provides a comprehensive understanding of the tip flow evolution, and of the interaction with the stator stage. High-fidelity compressible numerical simulations are performed and compared with experimental results. A periodic variation is seen in the aerodynamic performance of the rotor blades, which is associated to a potential-interaction phenomenon. Additionally, the convection of the tip vortices and further impingement in the stator vanes generate torque fluctuations on these elements. Dilatation fields and

P_{r m s}

contours confirm a noise source generated by the tip-vortex–stator interaction. Finally, excellent far-field noise comparisons between the numerical and experimental results are obtained for both tonal and broadband noise. Full article

(This article belongs to the Special Issue Advances in Industrial Fan Technologies)

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19 pages, 17228 KB

Open AccessArticle

The Influence of Leading Edge Tubercle on the Transient Pressure Fluctuations of a Hubless Propeller

by Max Hieke, Matthias Witte and Frank-Hendrik Wurm

Int. J. Turbomach. Propuls. Power 2026, 11(1), 4; https://doi.org/10.3390/ijtpp11010004 - 31 Dec 2025

Abstract

In recent years, the design priorities of modern marine propellers have shifted from maximizing efficiency to minimizing vibration-induced noise emissions and improving structural durability. However, an optimized design does not necessarily ensure optimal performance across the full operational range of a vessel. Due [...] Read more.

In recent years, the design priorities of modern marine propellers have shifted from maximizing efficiency to minimizing vibration-induced noise emissions and improving structural durability. However, an optimized design does not necessarily ensure optimal performance across the full operational range of a vessel. Due to operational constraints such as reduced docking times and regional speed regulations, propellers frequently operate off-design. This deviation from the design point leads to periodic turbulent boundary layer separation on the propeller blades, resulting in increased unsteady pressure fluctuations and, consequently, elevated hydroacoustic noise emissions. To mitigate these effects, bio-inspired modifications have been investigated as a means of improving flow characteristics and reducing pressure fluctuations. Tubercles, characteristic protrusions along the leading edge of humpback whale fins, have been shown to enhance lift characteristics beyond the stall angle by modifying the flow separation pattern. However, their influence on transient pressure fluctuations and the associated hydroacoustic behavior of marine propellers remains insufficiently explored. In this study, we apply the concept of tubercles to the blades of a hubless propeller, also referred to as a rim-drive propeller. We analyze the pressure fluctuations on the blades and in the wake by comparing conventional propeller blades with those featuring tubercles. The flow fields of both reference and tubercle-modified blades were simulated using the Stress Blended Eddy Simulation (SBES) turbulence model to highlight differences in the flow field. In both configurations, multiple helix-shaped vortex systems form in the propeller wake, but their decay characteristics vary, with the vortex structures collapsing at different distances from the propeller center. Additionally, Proper Orthogonal Decomposition (POD) analysis was employed to isolate and analyze the periodic, coherent flow structures in each case. Previous studies on the flow field of hubless propellers have demonstrated a direct correlation between transient pressure fluctuations in the flow field and the resulting noise emissions. It was demonstrated that the tubercle modification significantly reduces pressure fluctuations both on the propeller blades and in the wake flow. In the analyzed case, a reduction in pressure fluctuations by a factor of three to ten for the different BPF orders was observed within the wake flow. Full article

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Journal Description

International Journal of Turbomachinery, Propulsion and Power

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