On the Efficacy of Integrating Structural Struts With Lobed Mixers in Turbofan Engine Exhaust Systems

2018 ◽  
Author(s):  
Alexander Wright ◽  
Ali Mahallati ◽  
Martin J. Conlon ◽  
Julio Militzer
Keyword(s):  
Integrated Design ◽  
Exhaust System ◽  
Cfd Simulations ◽  
Engine Exhaust ◽  
Turbofan Engine ◽  
Core Flow ◽  
Minimal Impact ◽  
The Core ◽  
Flow Through ◽  
System Length

The efficacy of integrating the lobed mixer with the core flow deswirling struts to create a single component for reducing the exhaust system length, beyond that attainable through mixer optimization alone, has been investigated. This investigation has been conducted via CFD simulations of a medium-bypass turbofan exhaust system at engine cruise representative conditions. Comparative analysis shows that integration augmented thrust output by about 0.02% while total pressure loss was increased by 3.6%. The aim of the study, to show that this new integrated design would have either minimal impact on or improve exhaust system performance, was confirmed. Comparisons of the flow fields and characteristic quantities downstream of the mixer also showed minimal impact on flow through the nozzle. The deswirling strut was offset by 0.65 Dh axially when integrated with the mixer, therefore it can be concluded that the exhaust system ducting could be reduced in length by this same measure — saving engine weight in the process.

scholarly journals Numerical and Experimental Aerodynamic Investigation of an S-Shaped Intermediate Compressor Duct With Bleed

2021 ◽  
pp. 1-16
Author(s):  
Elias Siggeirsson ◽  
Niklas Andersson ◽  
Markus Olander Burak
Keyword(s):  
Integrated Design ◽  
Axial Flow ◽  
Experimental Facility ◽  
Cfd Simulations ◽  
Disturbed Flow ◽  
Operating Condition ◽  
Guide Vanes ◽  
Flow Through ◽  
Engine Systems ◽  
Aerodynamic Investigation

Abstract A series of CFD simulations are performed to analyse the effects a rotor off-take bleed has on the performance of an Intermediate Compressor Duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid RANS/LES simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor's outlet guide vanes resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increase bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.

scholarly journals Numerical and Experimental Aerodynamic Investigation of an S-Shaped Intermediate Compressor Duct With Bleed

2020 ◽  
Author(s):  
Elias M. V. Siggeirsson ◽  
Niklas Andersson ◽  
Markus Burak Olander
Keyword(s):  
Integrated Design ◽  
Axial Flow ◽  
Experimental Facility ◽  
Cfd Simulations ◽  
Disturbed Flow ◽  
Operating Condition ◽  
Guide Vanes ◽  
Flow Through ◽  
Engine Systems ◽  
Aerodynamic Investigation

Abstract A series of CFD simulations are performed to analyse the effects a rotor off-take bleed has on the performance of an Intermediate Compressor Duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid RANS/LES simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor’s outlet guide vanes resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increase bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.

Evaluation on the performance fluctuation after water ingestion for a turbofan engine compressor during flight descent

2020 ◽  
pp. 095441002097798
Author(s):  
Lu Yang ◽  
Qun Zheng ◽  
Aqiang Lin
Keyword(s):  
Droplet Diameter ◽  
Pressure Ratio ◽  
Critical Role ◽  
Water Film ◽  
Heavy Rain ◽  
Diameter Distribution ◽  
Turbofan Engine ◽  
Water Ingestion ◽  
The Core ◽  
Engine Compressor

Turbofan engine compressor is most severely threatened by the entry of liquid water during flight descent. This study aims to deeply understand the fluctuations of compressor performance parameters caused by water ingestion through frequency spectrum analysis. The water content and droplet diameter distribution are determined based on the real heavy rain environment. Results reveal that most of the droplets actually entering the core compressor have a particle size of less than 100 μm. In addition, the formation and motion of water film plays a critical role in affecting the fluctuation characteristics. Water ingestion deteriorates the compression performance and aggravates the unsteady fluctuations of the fan. However, the performance of the core compressor is less affected by water ingestion, but their fluctuations are still exacerbated. For some important parameters, such as inlet mass flow rate, total pressure ratio, total temperature ratio, compression work and efficiency, their main frequency of fluctuation are switched from the original blade passing frequency to the rotor passing frequency, and their amplitudes are correspondingly amplified to varying degrees. These phenomena can be observed in both the fluctuations of the fan and core compressor. Moreover, the operating point of them will be in the long-period and large-amplitude fluctuations, which leads them experiences the non-optimal state for a long time and threatens their operating stability.

Thrust Measurements using Acoustic Sensing on a Turbofan Engine Exhaust Plume

2021 ◽  
Author(s):  
John Gillespie ◽  
Kevin T. Lowe ◽  
Wing Ng ◽  
Loren Crook ◽  
Victor Oechsle
Keyword(s):  
Engine Exhaust ◽  
Turbofan Engine ◽  
Acoustic Sensing ◽  
Exhaust Plume

scholarly journals Sound propagation in a lined nozzle with shear and bias flows

2018 ◽  
Vol 18 (1) ◽  
pp. 3-48
Author(s):  
LMBC Campos ◽  
C Legendre
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Boundary Layers ◽  
Lower Boundary ◽  
Cross Flow ◽  
Core Flow ◽  
The Core ◽  
Wide Range ◽  
Bias Flow ◽  
Number Formula

In this study, the propagation of waves in a two-dimensional parallel-sided nozzle is considered allowing for the combination of: (a) distinct impedances of the upper and lower walls; (b) upper and lower boundary layers with different thicknesses with linear shear velocity profiles matched to a uniform core flow; and (c) a uniform cross-flow as a bias flow out of one and into the other porous acoustic liner. The model involves an “acoustic triple deck” consisting of third-order non-sinusoidal non-plane acoustic-shear waves in the upper and lower boundary layers coupled to convected plane sinusoidal acoustic waves in the uniform core flow. The acoustic modes are determined from a dispersion relation corresponding to the vanishing of an 8 × 8 matrix determinant, and the waveforms are combinations of two acoustic and two sets of three acoustic-shear waves. The eigenvalues are calculated and the waveforms are plotted for a wide range of values of the four parameters of the problem, namely: (i/ii) the core and bias flow Mach numbers; (iii) the impedances at the two walls; and (iv) the thicknesses of the two boundary layers relative to each other and the core flow. It is shown that all three main physical phenomena considered in this model can have a significant effect on the wave field: (c) a bias or cross-flow even with small Mach number [Formula: see text] relative to the mean flow Mach number [Formula: see text] can modify the waveforms; (b) the possibly dissimilar impedances of the lined walls can absorb (or amplify) waves more or less depending on the reactance and inductance; (a) the exchange of the wave energy with the shear flow is also important, since for the same stream velocity, a thin boundary layer has higher vorticity, and lower vorticity corresponds to a thicker boundary layer. The combination of all these three effects (a–c) leads to a large set of different waveforms in the duct that are plotted for a wide range of the parameters (i–iv) of the problem.

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