Investigation on the Aerodynamic Performance of an Annular Exhaust System for a Small Turboshaft Engine

2013 ◽  
Author(s):  
Pedro de la Calzada ◽  
Jorge Parra ◽  
Belén Mínguez
Keyword(s):  
Low Power ◽  
High Power ◽  
Engine Performance ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Performance Model ◽  
Pressure Recovery ◽  
Flow Angle ◽  
Baseline Design ◽  
Turboshaft Engine

An annular exhaust system design for being used in the bench testing of MTR390-E turboshaft engine has been performed at ITP. The exhaust system is aimed at improving the aerodynamic performance at high power compared with an existing exhaust system used in the previous version of the engine. The exhaust cone emulates to some extend the exhaust system in the helicopter and it is comprised of outer and inner cones supported by three struts. The CFD commercial code FLUENT is used to investigate the aerodynamic performance of the baseline design and to optimise the inner and outer cone angles in the new design based on 2D axisymmetric models. Representative radial exit turbine conditions and far field conditions are imposed in the model comprising the exhaust cones plus a large external domain. Two outer and inner cone angles and two inner cone lengths are analysed at low and high power conditions. The aerodynamic performance of the exhaust shows high sensitivity to the inlet flow angle which varies up to 30°/40° between the high and low power conditions. In all the simulated cases a large separation region is generated after the inner cone. Due to the high swirling flow the separation bubble behind the plug growths downstream hence reducing the effective flow exit area compared with the geometry area and reducing the pressure recovery downstream once the flow has been separated from the inner cone. Although all cases show similar qualitative behaviour, the best case based on the computed figures of merit (i.e., lowest total pressure loss) is chosen for the new design. In order to further optimise the behaviour of the exhaust at high power, in the new design the three struts are aligned with the flow angle at high power conditions (struts were axially oriented in the baseline design) and the resulting geometry is analysed by 3D CFD simulations. As expected, the orientation of the struts has a dramatic impact in the aerodynamic behaviour of the exhaust. The new design shows an improvement of 29% in pressure recovery at high power compared with the baseline configuration, although it shows a degradation of 12% at low power. Both the baseline and the new exhaust systems are tested with the real engine in the test bench. The general aerodynamic performance of the new design is compared with the CFD simulation. As a consequence of the design change an important modification in the aerodynamic behaviour of the exhaust is obtained impacting the whole engine performance. Therefore a new performance model of the exhaust system is proposed to be implemented in the whole engine performance model in order to accurately simulate the behaviour of the engine coupled with the new exhaust.

scholarly journals Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines

Acoustics ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 174-198 ◽  
Author(s):  
Mélissa Férand ◽  
Thomas Livebardon ◽  
Stéphane Moreau ◽  
Marlène Sanjosé
Keyword(s):  
Temperature Field ◽  
Low Power ◽  
Combustion Chamber ◽  
High Power ◽  
Acoustic Propagation ◽  
Combustion Noise ◽  
Far Field ◽  
Low Frequencies ◽  
Turboshaft Engine ◽  
Good Agreement

A hybrid methodology combining a detailed Large Eddy Simulation of a combustion chamber sector, an analytical propagation model of the extracted acoustic and entropy waves at the combustor exit through the turbine stages, and a far-field acoustic propagation through a variable exhaust temperature field was shown to predict far-field combustion noise from helicopter and aircraft propulsion systems accurately for the first time. For the single-stream turboshaft engine, the validation was achieved from engine core to the turbine exit. Propagation to the far field was then performed through a modeled axisymmetric jet. Its temperature modified the acoustic propagation of combustion noise significantly and a simple analytical model based on the Snell–Descarte law was shown to predict the directivity for axisymmetric single jet exhaust accurately. Good agreement with measured far-field spectra for all turboshaft-engine regimes below 2 kHz stresses that combustion noise is most likely the dominant noise source at low frequencies in such engines. For the more complex dual-stream turbofan engine, two regime computations showed that direct noise is mostly generated by the unsteady flame dynamics and the indirect combustion noise by the temperature stratification induced by the dilution holes in the combustion chamber, as found previously in the turboshaft case. However, in the turboengine, direct noise was found dominant at the combustor exit for the low power case and equivalent contributions of both combustion noise sources for the high power case. The propagation to the far-field was achieved through the temperature field provided by a Reynolds-Averaged Navier–Stokes simulation. Good agreement with measured spectra was also found at low frequencies for the low power turboengine case. At high power, however, turboengine jet noise overcomes combustion noise at low frequencies.

An Experimental Investigation of the Performance Impact of Swirl on a Turbine Exhaust Diffuser/Collector for a Series of Diffuser Strut Geometries

2015 ◽  
Author(s):  
Song Xue ◽  
Stephen Guillot ◽  
Wing F. Ng ◽  
Jon Fleming ◽  
K. Todd Lowe ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reverse Flow ◽  
Engine Performance ◽  
Pressure Recovery ◽  
Performance Impact ◽  
Flow Angle ◽  
Multiple Test ◽  
Wide Range ◽  
Flow Vortex ◽  
Turbine Exhaust

A comprehensive experimental investigation was initiated to evaluate the aerodynamic performance of a gas turbine exhaust diffuser/collector for various strut geometries over a range of inlet angle. The test was conducted on a 1/12th scale rig developed for rapid and accurate evaluation of multiple test configurations. The facility was designed to run continuously at an inlet Mach number of 0.40 and an inlet hydraulic diameter-based Reynolds number of 3.4×105. Multi-hole pneumatic pressure probes and surface oil flow visualization were deployed to ascertain the effects of inlet flow angle and strut geometry. Initial baseline diffuser-only tests with struts omitted showed a weakly increasing trend in pressure recovery with increasing swirl, peaking at 14° before rapidly dropping. Tests on profiled struts showed a similar trend with reduced recovery across the range of swirl and increased recovery drop beyond the peak. Subsequent tests for a full diffuser/collector configuration with profiled struts revealed a rising trend at lower swirl when compared to diffuser-only results, albeit with a reduction in recovery. When tested without struts, the addition of the collector to the diffuser not only reduced the pressure recovery at all angles but also resulted in a shift of the overall characteristic to a peak recovery at a lower value of swirl. The increased operation range associated with the implementation of struts in the full configuration is attributed to the de-swirling effects of the profiled struts. In this case the decreased swirl reduces the flow asymmetry responsible for the reduction in pressure recovery attributed to the formation of a localized reverse-flow vortex near the bottom of the collector. This research indicates that strut setting angle and, to a lesser extent, strut shape can be optimized to provide peak engine performance over a wide range of operation.

Investigations of Influential Factors on the Aerodynamic Performance of a Steam Turbine Exhaust System

2010 ◽  
Author(s):  
Jing-Lun Fu ◽  
Jian-Jun Liu
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Exhaust System ◽  
Aerodynamic Performance ◽  
Full Scale ◽  
Small Scale ◽  
Flow Angle ◽  
Fluid Properties ◽  
Turbine Exhaust ◽  
Exhaust Systems

The purpose of this paper is to investigate the influences of different parameters on the three-dimensional flow fields in the low-pressure steam turbine exhaust hood of a typical power station. The complex flows in both small-scale and full-scale turbine exhaust systems under different inlet flow conditions were simulated. The effects of inlet Reynolds number, inlet Mach number and fluid properties on the aerodynamic performance and flow fields in the exhaust systems were analyzed. The influential rules of inlet tangential flow angle distributions in the radial direction for a low speed small-scale model and a full speed full-scale exhaust system were summarized and compared. It is found that the inlet tangential flow angle at different radial position has different effects on the aerodynamic performance for both small-scale and full-scale exhaust systems. The influences of inlet Reynolds number on the aerodynamic performance depend on the inflow swirl conditions. The changing of inlet Mach number leads to the flow pattern variations in the exhaust system. The influences of fluid properties on the exhaust system performance are small.

An Experimental Investigation of the Performance Impact of Swirl on a Turbine Exhaust Diffuser/Collector for a Series of Diffuser Strut Geometries

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Song Xue ◽  
Stephen Guillot ◽  
Wing F. Ng ◽  
Jon Fleming ◽  
K. Todd Lowe ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reverse Flow ◽  
Engine Performance ◽  
Pressure Recovery ◽  
Performance Impact ◽  
Flow Angle ◽  
Multiple Test ◽  
Wide Range ◽  
Flow Vortex ◽  
Turbine Exhaust

A comprehensive experimental investigation was initiated to evaluate the aerodynamic performance of a gas turbine exhaust diffuser/collector for various strut geometries over a range of inlet angle. The test was conducted on a 1/12th scale rig developed for rapid and accurate evaluation of multiple test configurations. The facility was designed to run continuously at an inlet Mach number of 0.40 and an inlet hydraulic diameter-based Reynolds number of 3.4 × 105. Multihole pneumatic pressure probes and surface oil flow visualization were deployed to ascertain the effects of inlet flow angle and strut geometry. Initial baseline diffuser-only tests with struts omitted showed a weakly increasing trend in pressure recovery with increasing swirl, peaking at 14 deg before rapidly dropping. Tests on profiled struts showed a similar trend with reduced recovery across the range of swirl and increased recovery drop beyond the peak. Subsequent tests for a full diffuser/collector configuration with profiled struts revealed a rising trend at lower swirl when compared to diffuser-only results, albeit with a reduction in recovery. When tested without struts, the addition of the collector to the diffuser not only reduced the pressure recovery at all angles but also resulted in a shift of the overall characteristic to a peak recovery at a lower value of swirl. The increased operation range associated with the implementation of struts in the full configuration is attributed to the deswirling effects of the profiled struts. In this case, the decreased swirl reduces the flow asymmetry responsible for the reduction in pressure recovery attributed to the formation of a localized reverse-flow vortex near the bottom of the collector. This research indicates that strut setting angle and, to a lesser extent, strut shape can be optimized to provide peak engine performance over a wide range of operation.

Less Power, Greater Conflict

2018 ◽  
Vol 49 (1) ◽  
pp. 47-62 ◽  
Author(s):  
Petra C. Schmid
Keyword(s):  
Low Power ◽  
High Power ◽  
Goal Pursuit ◽  
Goal Conflict ◽  
Personal Goals ◽  
Multiple Goals ◽  
Objective Performance ◽  
The Future ◽  
The Way

Abstract. Power facilitates goal pursuit, but how does power affect the way people respond to conflict between their multiple goals? Our results showed that higher trait power was associated with reduced experience of conflict in scenarios describing multiple goals (Study 1) and between personal goals (Study 2). Moreover, manipulated low power increased individuals’ experience of goal conflict relative to high power and a control condition (Studies 3 and 4), with the consequence that they planned to invest less into the pursuit of their goals in the future. With its focus on multiple goals and individuals’ experiences during goal pursuit rather than objective performance, the present research uses new angles to examine power effects on goal pursuit.

AlInAs/GaInAs on InP HEMTs for low power supply voltage operation of high power-added efficiency microwave amplifiers

1993 ◽  
Vol 29 (15) ◽  
pp. 1324 ◽  
Author(s):  
L.E. Larson ◽  
M.M. Matloubian ◽  
J.J. Brown ◽  
A.S. Brown ◽  
M. Thompson ◽  
...  
Keyword(s):  
Low Power ◽  
High Power ◽  
Power Supply ◽  
Supply Voltage ◽  
Power Supply Voltage ◽  
Power Added Efficiency ◽  
Microwave Amplifiers

Effect of Power on Moral Judgment

1978 ◽  
Vol 42 (2) ◽  
pp. 387-394
Author(s):  
Russell Hamby
Keyword(s):  
Social Psychology ◽  
Moral Responsibility ◽  
Low Power ◽  
Moral Judgment ◽  
Factorial Design ◽  
High Power ◽  
Moral Judgments ◽  
Need For Power ◽  
Experimenter Effects

Ambiguous effects of power on attributions of moral responsibility for an accident are interpreted to result from the intervening effects of need for power, which is aroused by the anticipation of exercising power over another. 160 subjects from introductory social psychology classes participated in a questionnaire-type experiment comparing effects of high/low carelessness, severe/minor consequences, and high/low power of the attributor in a 2 × 2 × 2 factorial design. In a follow-up experiment 30 subjects were assigned to conditions of high or low power, and their needs for power and moral attributions were measured. High power seemed to arouse need for power, which was curvilinearly related to moral judgments. Those high and low in need for power attributed more moral responsibility to the perpetrator of an accident than those with moderate levels of need for power. The results suggest complicated models of both moral judgments and experimenter effects related to the level or arousal of motivations.

Feeling Guilty and Flattering God: The Mediating Role of Prayer

2021 ◽  
pp. 009164712199242
Author(s):  
Beata Zarzycka ◽  
Kamil Tomaka ◽  
Katarzyna Zając ◽  
Klaudia Marek
Keyword(s):  
Low Power ◽  
High Power ◽  
Mediating Role ◽  
Shame Proneness ◽  
The Relationship ◽  
Significant Mediator

Ingratiation refers to acts of flattery, typically given by a low-power person to a high-power one, performed to gain acceptance and approval. This study investigates ingratiation in the religious setting, asking whether people feeling high levels of guilt or shame tend to manifest such ingratiating behavior toward God. The study aimed to examine the mediating role of prayer in the relationship between guilt and shame and ingratiation toward God. A total of 148 respondents (80 women and 68 men) participated in the study. The Religious Ingratiation Scale, the Content of Prayer Scale, and the Guilt and Shame Proneness Scale were applied to the research. The results showed that feeling guilty increased the tendency to ingratiation toward God. Prayer was the significant mediator in this relationship. People high in guilt tend to flatter God by offering more adoration and fewer repine prayers.

scholarly journals Jet A and Propane gas combustion in a turboshaft engine: performance and emissions reductions

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Ali Hasan ◽  
Oskar J. Haidn
Keyword(s):  
Combustion Process ◽  
Engine Performance ◽  
Emissions Reductions ◽  
Gas Combustion ◽  
Liquid Petroleum Gas ◽  
Performance And Emissions ◽  
Air Mixing ◽  
Turboshaft Engine ◽  
Engine Performance And Emissions ◽  
Lower Carbon

AbstractThe Paris Agreement has highlighted the need in reducing carbon emissions. Attempts in using lower carbon fuels such as Propane gas have seen limited success, mainly due to liquid petroleum gas tanks structural/size limitations. A compromised solution is presented, by combusting Jet A fuel with a small fraction of Propane gas. Propane gas with its relatively faster overall igniting time, expedites the combustion process. Computational fluid dynamics software was used to demonstrate this solution, with results validated against physical engine data. Jet A fuel was combusted with different Propane gas dosing fractions. Results demonstrated that depending on specific propane gas dosing fractions emission reductions in ppm are; NOx from 84 to 41, CO2 from less than 18,372 to less than 15,865, escaping unburned fuels dropped from 11.4 (just Jet A) to 6.26e-2 (with a 0.2 fraction of Propane gas). Soot and CO increased, this is due to current combustion chamber air mixing design.

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