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Int. J. Turbomach. Propuls. Power, Volume 7, Issue 4 (December 2022) – 9 articles

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Article
Effect of Sweep on Axial Fan Noise Sources Using the Lattice Boltzmann Method
Int. J. Turbomach. Propuls. Power 2022, 7(4), 34; https://doi.org/10.3390/ijtpp7040034 - 22 Nov 2022
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Abstract
The effect of blade sweep has been studied numerically with the Lattice Boltzmann Method on a family of low-speed free-vortex axial fans with sweeps of ±45°. Good overall aerodynamic agreement is first demonstrated on all fans at the design condition, particularly in the [...] Read more.
The effect of blade sweep has been studied numerically with the Lattice Boltzmann Method on a family of low-speed free-vortex axial fans with sweeps of ±45°. Good overall aerodynamic agreement is first demonstrated on all fans at the design condition, particularly in the tip gap. The local larger wall-pressure fluctuations seen in the unswept and backward swept fans compared to the forward case are traced to the stronger tip vortices that remain in the rotational plane or even move upstream. These stronger and faster vortices interacting with the fan blades are then responsible for the larger noise levels observed in the acoustic spectra of these fans, and particularly for large subharmonic humps. Excellent agreement between experimental and numerical noise predictions is finally reported stressing the dominant tip noise. Full article
(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)
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Article
Inlet Gap Effect on Tonal Noise Generated from a Voluteless Centrifugal Fan
Int. J. Turbomach. Propuls. Power 2022, 7(4), 33; https://doi.org/10.3390/ijtpp7040033 - 18 Nov 2022
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Abstract
In this study, three voluteless centrifugal fans are compared for their aeroacoustic performances. The tonal noise is predicted by coupling the IDDES with Formulation 1A of Farassat. The sources of the tonal noise at the blade passing frequency (BPF) [...] Read more.
In this study, three voluteless centrifugal fans are compared for their aeroacoustic performances. The tonal noise is predicted by coupling the IDDES with Formulation 1A of Farassat. The sources of the tonal noise at the blade passing frequency (BPF) are identified. It is found that the sources are related to the fan inlet gap, which introduces higher velocity intensities and turbulent fluctuations interacting with the blade leading edge. By redesigning the gap, the tonal noise at the BPF is reduced effectively. Full article
(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)
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Article
Evaluation of the Wear-Resistant Plate Performance on Different Locations over the Flow Path of a Large-Sized Heavy-Duty Centrifugal Fan
Int. J. Turbomach. Propuls. Power 2022, 7(4), 32; https://doi.org/10.3390/ijtpp7040032 - 17 Nov 2022
Viewed by 235
Abstract
In industrial applications such as chemical plants, cement factories, and glassmakers, large-sized centrifugal fans are commonly used for dust-laden flow processing. In many cases, the contamination is due to solid particles responsible for fouling and erosion issues. Erosion induces the reduction of mechanical [...] Read more.
In industrial applications such as chemical plants, cement factories, and glassmakers, large-sized centrifugal fans are commonly used for dust-laden flow processing. In many cases, the contamination is due to solid particles responsible for fouling and erosion issues. Erosion induces the reduction of mechanical resistance and, at the same time, the modification of the geometry and the surface characteristics of the internal flow path. The process works according to the characteristics of the erodent particles, such as dimension and hardness, which have to be coupled with the mechanical properties of the substrate, like hardness and roughness level. In addition to this, the intensity of the erosion depends on the dynamic characteristics of particles, especially velocity and impact angle. For these reasons, erosion-related issues are difficult predict and reduce. In an attempt to preserve the structural integrity of the internal walls, wear-resistant plates are positioned where the impacting contaminants are supposed to be more detrimental. In the present work, a combined experimental and numerical approach is proposed to evaluate the proper setup of wear-resistance plates over the flow path of a large-sized centrifugal fan. The results show how different regions (rotating and stationary walls) are subjected to different impact behavior, determining that the design of the position of the wear-resistant plate is not straightforward. Suggestions related to reducing the erosion intensity are reported, highlighting the possibility of designing the best compromise between erosion, performance, and costs. Full article
(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)
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Article
Energy and CO2 Impact of the Eco-Design Regulation for Fans on the European Market
Int. J. Turbomach. Propuls. Power 2022, 7(4), 31; https://doi.org/10.3390/ijtpp7040031 - 16 Nov 2022
Viewed by 257
Abstract
Fans are components in many different products and have been regulated since 2011 by the Eco-Design Regulation. A fan is typically not a final product but is used as a component in different applications, systems, and products. This study shows that it is [...] Read more.
Fans are components in many different products and have been regulated since 2011 by the Eco-Design Regulation. A fan is typically not a final product but is used as a component in different applications, systems, and products. This study shows that it is helpful to target and regulate a component (possibly additionally) such a fan and that the Eco-Design Regulation of fans is an important driver of energy efficiency and has a significant impact. Regulating fans as a component stimulates the availability of efficient fans at reasonable prices and drives efficiency, also in cases where fans are implemented in other products where a fan’s efficiency does not dominate its performance. Since it was first implemented in 2013, the following savings in electrical energy were achieved: 12 GW electrical power, 150 TWh electrical energy, and 12 MT CO2. This is significant and a good example for regulation. Full article
(This article belongs to the Special Issue Fan Noise, Aerodynamics, Applications and Systems)
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Article
Uncovering the Root Causes of Stall Flutter in a Wide Chord Fan Blisk
Int. J. Turbomach. Propuls. Power 2022, 7(4), 30; https://doi.org/10.3390/ijtpp7040030 - 02 Nov 2022
Viewed by 460
Abstract
Flutter was encountered at part speeds in a scaled wide chord fan blisk designed for a civil aeroengine during a rig test when the fan bypass flow was throttled toward its stall boundary. Analysis of the blade tip timing measurement data revealed that [...] Read more.
Flutter was encountered at part speeds in a scaled wide chord fan blisk designed for a civil aeroengine during a rig test when the fan bypass flow was throttled toward its stall boundary. Analysis of the blade tip timing measurement data revealed that the fan blades vibrated at the first flap (1F) mode with nodal diameters of two and three. To facilitate a further rig test and ultimately eliminate the flutter problem, a numerical campaign was launched to help understand the root causes of the flutter. Both the influence coefficient method (ICM) and the traveling wave method (TWM) were employed in the numerical investigation to analyze unsteady flows due to blade vibration, with the intention to corroborate different numerical results and take advantage of each method. To eliminate nonphysical reflections, a sponge layer with an inflated mesh size was used for the extended inlet and outlet regions. Steady flow field and unsteady flow field were examined to relate them to the blade flutter. The influences of vibration frequency, mass flow rate, shock, boundary layer separation and acoustic mode propagation behaviors on the fan flutter stability were also investigated. Particular attention was paid to the acoustic mode propagation behaviors. Full article
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Article
Impact of Methane and Hydrogen-Enriched Methane Pilot Injection on the Surface Temperature of a Scaled-Down Burner Nozzle Measured Using Phosphor Thermometry
Int. J. Turbomach. Propuls. Power 2022, 7(4), 29; https://doi.org/10.3390/ijtpp7040029 - 01 Nov 2022
Viewed by 387
Abstract
The surface temperature of a burner nozzle using three different pilot hardware configurations was measured using lifetime phosphor thermometry with the ZnS:Ag phosphor in a gas turbine model combustor designed to mimic the Siemens DLE (Dry Low Emission) burner. The three pilot hardware [...] Read more.
The surface temperature of a burner nozzle using three different pilot hardware configurations was measured using lifetime phosphor thermometry with the ZnS:Ag phosphor in a gas turbine model combustor designed to mimic the Siemens DLE (Dry Low Emission) burner. The three pilot hardware configurations included a non-premixed pilot injection setup and two partially premixed pilot injections where one had a relatively higher degree of premixing. For each pilot hardware configuration, the combustor was operated with either methane or hydrogen-enriched methane (H2/CH4: 50/50 in volume %). The local heating from pilot flames was much more significant for hydrogen-enriched methane compared with pure methane due to the pilot flames being in general more closely attached to the pilot nozzles with hydrogen-enriched methane. For the methane fuel, the average surface temperature of the burner nozzle was approximately 40 K higher for the partially premixed pilot injection configuration with a lower degree of mixing as compared to the non-premixed pilot injection configuration. In contrast, with the hydrogen-enriched methane fuel, the differences in surface temperature between the different pilot injection hardware configurations were much smaller due to the close-to-nozzle frame structure. Full article
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Article
A Comparative Performance Analysis of the Novel TurboAux Engine with a Turbojet Engine, and a Low-Bypass Ratio Turbofan Engine with an Afterburner
Int. J. Turbomach. Propuls. Power 2022, 7(4), 28; https://doi.org/10.3390/ijtpp7040028 - 31 Oct 2022
Viewed by 213
Abstract
Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption [...] Read more.
Presented herein is a comparative performance analysis of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine, against a turbojet engine, and a low bypass ratio turbofan engine with an afterburner is presented. The TurboAux engine is an adaption of the low-bypass ratio turbofan engine, but with secondary combustion in an auxiliary bypass annular combustion chamber for thrust augmentation. The TurboAux engine is envisioned with the desire to facilitate clean secondary burning of fuel at temperatures higher than in the main combustion chamber with air exiting the low-pressure compressor. The comparative study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. In parallel, the conventional turbofan and its mixing counterpart are analyzed, also with and without an afterburner segment. A simple optimization analysis of a conventional turbofan is performed to identify optimal ‘fan’ pressure ratios for a series of low-bypass ratios (0.1 to 1.5). The optimal fan pressure ratios and their corresponding bypass ratios are adapted to demonstrate the comparative performance of the varying configurations of the TurboAux engine. The formulation and results are an attempt to make a case for charter aircrafts and efficient close-air-support aircrafts. The results yielded increased performance in thrust augmentation, but at the cost of a spike in fuel consumption. This trade-off requires more in-depth investigation to further ascertain the TurboAux’s utility. Full article
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Article
Experimental Investigation of a Complex System of Impinging Jets Using Infrared Thermography
Int. J. Turbomach. Propuls. Power 2022, 7(4), 27; https://doi.org/10.3390/ijtpp7040027 - 01 Oct 2022
Viewed by 456
Abstract
A central task in aviation technology is the development of efficient cooling techniques for thermal highly loaded engine components. For an optimal design of the cooling mechanisms, the heat transfer characteristics have to be known and need to be describable. As a cooling [...] Read more.
A central task in aviation technology is the development of efficient cooling techniques for thermal highly loaded engine components. For an optimal design of the cooling mechanisms, the heat transfer characteristics have to be known and need to be describable. As a cooling concept for low-pressure turbine casings, complex systems of impinging jets are used in order to reduce blade tip clearances during the flight mission. In order to improve established theoretical model approaches, this paper presents a novel method for the experimental investigation of such a complex system with 200 impinging jets using infrared thermography. The presented experimental method uses a thin electrically heated chrome-aluminum foil as target plate. Modeling the transient effects inside the foil, small structures and high gradients in the heat transfer coefficient can be reproduced with good accuracy. Experimental results of the local heat transfer characteristics are reported for jet Reynolds numbers of Re=20006000. The influence of the jet-to-jet distance and the jet Reynolds number on the Nusselt numbers are quantified with Nu(S/D)0.47 and NuRe0.7. The results indicate a dependency of the flow regime for the relatively low jet Reynolds numbers, as it is known from literature. Full article
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Article
Near-Stall Modelling of a Pitching Airfoil at High Incidence, Mach Number and Reduced Frequency
Int. J. Turbomach. Propuls. Power 2022, 7(4), 26; https://doi.org/10.3390/ijtpp7040026 - 29 Sep 2022
Viewed by 518
Abstract
The prediction accuracy of aeroelastic stability in fans and compressors depends crucially on the accuracy of the underlying aerodynamic predictions. The prevalent approach in the field solves the unsteady Reynolds-averaged Navier—Stokes equations in the presence of blade vibration. Given the unsteady, three-dimensional and [...] Read more.
The prediction accuracy of aeroelastic stability in fans and compressors depends crucially on the accuracy of the underlying aerodynamic predictions. The prevalent approach in the field solves the unsteady Reynolds-averaged Navier—Stokes equations in the presence of blade vibration. Given the unsteady, three-dimensional and often separated nature of the flow in the regimes of aeroelastic interest, the confidence in URANS methods is questionable. This paper uses the simple test case of a pitching symmetric aerofoil with a sharp leading edge to illustrate the challenges of aeroelastic modelling. It compares coupled numerical simulations against time-resolved experimental measurements. The unsteady aerodynamic response of the pitching blade and its dependency on tip-clearance flow and time-averaged incidence angle are analyzed. The results indicate that differences in the unsteady aerodynamics between different numerical approaches close to stall can have a significant impact on local aerodynamic damping. Furthermore, for the chosen test case there is a strong correspondence between the local quasi-steady and unsteady behaviour which weakens, but is still present, towards stall. Full article
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