Dynamics of Swirling Flow in a Dump Combustor at Elevated Pressures

2009 ◽  
Author(s):  
N. P. Yadav ◽  
Abhijit Kushari
Keyword(s):  
Flow Field ◽  
Swirling Flow ◽  
Separated Flow ◽  
Wall Pressure ◽  
Operating Conditions ◽  
Needle Valve ◽  
Chamber Pressure ◽  
Dump Combustor ◽  
Pressure Distributions ◽  
Inlet Swirl

This paper reports an experimental investigation of the flow field inside a low aspect ratio dump combustor with inlet swirl and choked exit. The length of the combustor studied was less than the reattachment length for the separated flow. The tapered exit of the combustor was choked by a needle valve to investigate the effect of elevated chamber pressure on the flow field of the combustor. The variation in wall pressure and velocity at different locations and Reynolds number was studied. It was observed that the turbulent intensity increased with the swirling flow and decreased with an increase in the chamber pressure. The exit choking reinforced the recirculation. The velocity distributions were corroborated by comparing the frequency spectrum with the wall pressure distributions and the results were found to be in good qualitative agreement with each other. This study will be helpful to design the combustor for different operating conditions.

An Impact of Self-Recirculation Casing Treatment (SRCT) Configurations on Impeller Stall Margin and the Flow Field

2012 ◽  
Author(s):  
Yan Ma ◽  
Guang Xi ◽  
Guangkuan Wu
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Operating Conditions ◽  
Centrifugal Impeller ◽  
Flow Angle ◽  
Stall Margin ◽  
Casing Treatment ◽  
Swirl Velocity ◽  
Inlet Swirl ◽  
Unsteady Simulation

The present paper describes an investigation of stall margin enhancement and a detailed analysis of the impeller flow field due to self-recirculation casing treatment (SRCT) configuration of a high-speed small-size centrifugal impeller. The influence of different SRCT configurations on the impeller flow field at near-stall condition has been analyzed, highlighting the improvement in stall flow ability. This paper also discusses the influence of the SRCT configurations on the inlet flow angle, inlet swirl velocity and loss distribution in the impeller passage to understand the mechanism of the SRCT configurations in enhancing the stall margin of the impeller. The variation of the bleed flow rate at different operating conditions is also presented in this paper. Finally, the time-averaged unsteady simulation results at near-stall point are presented and compared with steady-state solutions.

scholarly journals Flow field and species concentration measurements in the primary zone of an aero-engine combustion chamber

2018 ◽  
Vol 10 (1) ◽  
pp. 168781401774805
Author(s):  
Yinli Xiao ◽  
Zupeng Wang ◽  
Zhengxin Lai ◽  
Kefei Chen ◽  
Wenyan Song
Keyword(s):  
Flow Field ◽  
Combustion Chamber ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Species Concentration ◽  
Primary Zone ◽  
Major Species ◽  
Engine Combustion ◽  
Aero Engine ◽  
Concentration Measurements

The principal features of primary zone determine the performance parameters of the whole combustion chamber, such as the pollutant emissions and combustion efficiency. In this work, flow field and major species concentration measurements are conducted in the primary zone of an aero-engine combustion chamber. The operating conditions such as air inlet temperature, chamber pressure, and air-to-fuel ratio are chosen to replicate the realistic operating conditions. The velocity field and streamlines are obtained by particle imaging velocimetry technology. The concentrations of major species are acquired by a spontaneous Raman scattering system. This article validates the feasibility of two laser diagnostic measurement techniques and presents the initial results under realistic aero-engine conditions.

Understanding Effects of Wet Compression on Separated Flow Behavior in an Axial Compressor Stage Using CFD Analysis

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Lanxin Sun ◽  
Qun Zheng ◽  
Yijin Li ◽  
Rakesh Bhargava
Keyword(s):  
Flow Field ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Water Flow Rate ◽  
Separated Flow ◽  
Operating Conditions ◽  
Compressor Stage ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Wet Compression

The effects of wet compression on the flow field within a compressor stage, particularly in the presence of the separated flow region, are not fully understood. Numerical simulations of 3D compressible separated flows within a wet compression compressor stage are carried out using a computational fluid dynamics (CFD) program. Numerical computations of flow fields in a compressor cascade with wet compression assume that a separated region exist in the corner of the rotor blade suction surface and hub surface in the case of dry compression. Under different operating conditions and with wet compression, this study presents the changes in the extent of separated region on the flow channel surfaces, compression efficiency, pressure ratio and specific compression work, etc. Also, effects of factors such as droplet size, droplet temperature, and injected water flow rate on the compressor stage performance and flow field within compressor stage passage have been investigated. The results show that wet compression could weaken and eliminate the flow separation and then the efficiency and pressure ratio maintain a high level.

Physics of unsteady blunt-fin-induced shock wave/turbulent boundary layer interactions

1994 ◽  
Vol 273 ◽  
pp. 375-409 ◽  
Author(s):  
Leon Brusniak ◽  
David S. Dolling
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Time History ◽  
Separated Flow ◽  
Flow Region ◽  
Horseshoe Vortex ◽  
Wall Pressure ◽  
Pressure Measurements ◽  
Separation Shock ◽  
Pressure Distributions

Fluctuating wall-pressure measurements have been made on the centreline upstream of a blunt fin in a Mach 5 turbulent boundary layer. By examining the ensemble-averaged wall-pressure distributions for different separation shock foot positions, it has been shown that local fluctuating wall-pressure measurements are due to a distinct pressure distribution, [weierp ]i, which undergoes a stretching and flattening effect as its upstream boundary translates aperiodically between the upstream-influence and separation lines. The locations of the maxima and minima in the wall-pressure standard deviation can be accurately predicted using this distribution, providing quantitative confirmation of the model. This model also explains the observed cross-correlations and ensemble-average measurements within the interaction. Using the [weierp ]i model, wall-pressure signals from under the separated flow region were used to reproduce the position–time history of the separation shock foot. The unsteady behaviour of the primary horseshoe vortex and its relation to the unsteady separation shock is also described. The practical implications are that it may be possible to predict some of the unsteady aspects of the flowfield using mean wall-pressure distributions obtained from either computations or experiments; also, to minimize the fluctuating loads caused by the unsteadiness, flow control methods should focus on reducing the magnitude of the [weierp ]i gradient (∂[weierp ]i/∂x).

Stochastic estimation of a separated-flow field using wall-pressure-array measurements

2007 ◽  
Vol 19 (2) ◽  
pp. 024103 ◽  
Author(s):  
Laura M. Hudy ◽  
Ahmed Naguib ◽  
William M. Humphreys
Keyword(s):  
Flow Field ◽  
Separated Flow ◽  
Wall Pressure ◽  
Stochastic Estimation ◽  
Array Measurements

A Study of Modest CFD Models for the Design of an Annular Diffuser With Struts for Swirling Flow

2008 ◽  
Author(s):  
G. K. Feldcamp ◽  
A. M. Birk
Keyword(s):  
Swirling Flow ◽  
Turbulence Models ◽  
Surface Flow ◽  
Experimental Results ◽  
Navier Stokes ◽  
Cfd Models ◽  
Pressure Distributions ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
Visualization Techniques

Cold flow experiments were conducted to study swirling flows in an annular diffuser with various strut configurations. Experimental results at 0°, 20°, and 40° of inlet swirl were obtained. Measured properties included detailed inlet and exit traverses using three and seven hole pressure probes, surface pressure taps on the diffuser wall, and surface flow visualization techniques. Evaluation of the diffuser and strut performance was based on pressure recovery, and detailed pressure distributions. The experimental results have been studied further using Reynolds Averaged Navier Stokes (RANS) based Computational Fluid Dynamics (CFD). These models are of modest size (less than four million volumes). Several turbulence models have been used to predict the performance of the annular diffuser with struts. Both high and low Reynolds number implementations of the turbulence models have been investigated. The results show that modest CFD models can be used with confidence to design these devices.

Identification of the Cold Flow Perturbation Sources in a Dump Combustor With a Tapered Exit

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
N. P. Yadav ◽  
Abhijit Kushari
Keyword(s):  
Shear Layer ◽  
Separated Flow ◽  
Reynolds Numbers ◽  
Wall Pressure ◽  
Mean Velocity ◽  
Potential Core ◽  
Flow Perturbation ◽  
Dump Combustor ◽  
Power Spectral ◽  
Pressure And Velocity Measurements

This paper reports on the experimental investigation of the flow inside a low aspect ratio (length less than the reattachment length of separated flow) dump combustor with a tapered exit. The flow field in the combustor is evaluated using wall pressure and velocity measurements at varying flow Reynolds numbers. The mean velocity and turbulence variation closer to the wall of the combustor was found to be different from that at other radial locations due to the presence of recirculation and possible thickening of the shear layer caused by a decrease in the strength of the potential core. The power spectral study of the wall pressure and velocity fluctuations suggested the dominant presence of acoustic perturbations with amplitude modulation of such perturbations due to viscous dissipation in the shear layer.

scholarly journals Simulation of transient gusts on the NREL5 MW wind turbine using CFD

2017 ◽  
Author(s):  
Annika Länger-Möller
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Rotor Blade ◽  
Operating Conditions ◽  
Blade Loading ◽  
Pressure Coefficients ◽  
Pressure Distributions ◽  
The Impact ◽  
Blade Loads ◽  
Flow States

Abstract. The performed work presents a procedure, implemented in the CFD-solver THETA, to propagate longitudinal transient gusts through a flow field by using a resolved gust approach. Both, the gust strike of a 1–cos()-gust and an extreme operating gust following the IEC-64100-1 standard, on the generic NREL 5MW wind turbine at rated operating conditions are investigated with CFD. The impact of both gusts on pressure distributions, rotor thrust, rotor torque, and flow states on the blade are examined and quantified. The flow states on the rotor blade before the gust strike and at maximum and minimum gust velocity are compared. An increased blade loading is detectable in the pressure coefficients and integrated blade loads. The friction force coefficients indicate the dynamic separation and re-attachment of the flow during the gust.

Velocity and Droplet Diameter Distributions of Reacting N-Heptane Sprays at Varied Boundary Conditions in a Generic Gas Turbine Combustor

2010 ◽  
Author(s):  
Michael Hage ◽  
Jan Bru¨bach ◽  
Andreas Dreizler
Keyword(s):  
Boundary Conditions ◽  
Gas Turbines ◽  
Swirling Flow ◽  
Laser Diagnostics ◽  
Droplet Diameter ◽  
Measurement Techniques ◽  
Operating Conditions ◽  
Chamber Pressure ◽  
Inlet Temperature ◽  
Diameter Distributions

In addition to a previous isothermal study, the present work reports on reacting swirling flow fields and droplet diameter distributions. The employed combustion chamber enabled optical access from three sides allowing the application of laser based measurement techniques. It is equipped with an airblast atomizer nozzle typical for gas turbines. The parameters of the boundary conditions were varied to such an extent that laser diagnostics were feasible. The chamber pressure and the inlet temperature were 2–3 bar and 300–350°C, respectively. The analysis of the spray droplets were performed by two velocity component phase Doppler anemometry (PDA). The measurements allowed for the investigation of axial and radial droplet velocities, Sauter mean diameter (SMD) distributions and an estimation of the volume flow rates. Comparisons of the different operating conditions and the influence of the parameters are given in the discussion.

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