Inlet Distortion Effects in Axial Compressors

1980 ◽  
Vol 102 (1) ◽  
pp. 7-13 ◽  
Author(s):  
A. H. Stenning
Keyword(s):  
Gas Turbines ◽  
Total Pressure ◽  
Free Flow ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Axial Compressors ◽  
Inlet Distortion ◽  
Compressor Inlet ◽  
Inlet Conditions

Although uniform inlet conditions are highly desirable and system designers attempt to insure distortion-free flow entering compressors, situations frequently arise in which substantial total pressure, velocity, and angle variations exist at the compressor inlet. Aircraft gas turbines are particularly prone to inlet distortion problems due to changes in aircraft attitude and the effect of the airframe on the inlet flow conditions, but industrial insallations may also suffer from inlet distortion in cases where poorly designed bends have been installed upstream of the compressor. In this paper, problems associated with inlet distortion are discussed and some of the simpler techniques for analyzing the effects of circumferential inlet distortion are presented.

A New Inlet Distortion and Pressure Loss Based Design of an Intake System for Stationary Gas Turbines

2013 ◽  
Author(s):  
Jose Rodriguez ◽  
Stephan Klumpp ◽  
Thomas Biesinger ◽  
James O’Brien ◽  
Tobias Danninger
Keyword(s):  
Gas Turbines ◽  
Inlet System ◽  
Inlet Distortion ◽  
Surge Margin ◽  
Compressor Surge ◽  
Compressor Inlet ◽  
The Face ◽  
Flow Quality ◽  
Inlet Manifold ◽  
Distortion Parameters

This paper presents a new design for a Compressor Inlet Manifold (CIM) for a land-based power generation Gas Turbine (turbine). The CIM is the component of the Inlet System (IS) that is directly connected to the turbine via the Compressor Inlet Case (CIC). The design philosophy is to use low fidelity but fast and automated CFD (Computational Fluid Dynamics) for design iterations and then confirm the design with detailed higher accuracy CFD before proceeding to engine tests. New design features include contouring the wall to minimize areas of flow separation and associated unsteadiness and losses, and improvement of the flow quality into the compressor. The CIM in a land-based turbine acts as a nozzle whereas the inlet of an aircraft acts as a diffuser. The flow also enters the CIM at 90 deg to the engine axis. This leads to a pair of counter rotating vortices at the compressor inlet. Three main sources of flow distortions at the face of the compressor are identified: flow separations at outer walls of the IS and CIM struts and the counter rotating vortices. The higher accuracy CFD analysis including the complete IS, CIM and the first compressor stage, simulates the effect of these distortions on the compressor front stage at design conditions. A range of inlet distortion parameters are used to evaluate the inlet design. The well known DC60 based criterion derived from aircraft engines and other less known but published parameters are able to give an indication of how the compressor surge margin of stationary gas turbines is affected.

scholarly journals Experimental Investigation of Inlet Distortion Effect on Performance of a Micro Gas Turbine

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Alireza Naseri ◽  
Shervin Sammak ◽  
Masoud Boroomand ◽  
Alireza Alihosseini ◽  
Abolghasem M. Tousi
Keyword(s):  
Gas Turbine ◽  
Total Pressure ◽  
Nonuniform Flow ◽  
Inlet Flow ◽  
Micro Gas Turbine ◽  
Inlet Distortion ◽  
Air Jet ◽  
Measuring Devices ◽  
Turbine Performance ◽  
Distortion Effect

An experimental study has been carried out to determine how inlet total-pressure distortion affects the performance of a micro gas turbine. An inlet simulator is designed and developed to produce and measure distortion patterns at the inlet to the gas turbine. An air jet distortion generator (AJDG) is used to produce nonuniform flow patterns and total pressure probes are installed to measure steady-state total-pressure distribution at the inlet. A set of wind tunnel tests have been performed to confirm the fidelity of distortion generator and measuring devices. Tests are carried out with the gas turbine exposed to inlet flow with 60 deg, 120 deg, and 180 deg circumferential distortion patterns with different distortion intensities. The performance of the gas turbine has been measured and compared with that of clean inlet flow case. Results indicate that the gas turbine performance can be affected significantly facing with intense inlet distortions.

Effects of Inlet Distortion Patterns on Induced Swirl in a Highly Loaded Fan Stage

2020 ◽  
Author(s):  
Andrew D. Orme ◽  
Steven E. Gorrell ◽  
Addison C. Pulsipher
Keyword(s):  
Total Pressure ◽  
Gradual Transition ◽  
Flow Physics ◽  
Inlet Distortion ◽  
Inlet Conditions ◽  
Highly Loaded

Abstract Characterization of distortion transfer and generation through fans with distorted inlet conditions enables progress towards designs with improved distortion tolerance. The abruptness of transition from undistorted to distorted total pressure regions at the inlet impacts the induced swirl profile and therefore the distortion transfer and generation. These impacts are characterized using URANS simulations of PBS Rotor 4 geometry under a variety of inlet distortion profiles. A 90° and a 135° sector, both of 15% total pressure distortion, are considered. Variants of each sector size, with decreasing levels of distortion transition abruptness, are each applied to the fan. Fourier-based distortion descriptors are used to quantify levels of distortion transfer and generation at axial locations through the fan, principally at the stator inlet. It is shown that a gradual transition in distortion at the inlet results in decreased levels of distortion transfer and generation. The flow physics resulting in this reduction are explored.

Experimental Investigation of the Influence of Inlet Distortion on the Stall Inception in a Low Speed Axial Compressor

2009 ◽  
Author(s):  
Huabing Jiang ◽  
Yajun Lu ◽  
Wei Yuan ◽  
Qiushi Li
Keyword(s):  
Flow Field ◽  
Dynamic Response ◽  
Flow Separation ◽  
Flow Condition ◽  
Axial Compressor ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Stall Inception ◽  
Inlet Distortion ◽  
Compressor Performance

Inlet distortion is one of the major concerns for high maneuverability airplanes. An experiment is performed to investigate the influence of inlet distortion on the stall inception in a low speed axial compressor, where the distorted inlet flow field is simulated with a flat baffle placed upstream of the compressor. The flow field around a rotor blade is measured using 2D Digital Particle Image Velocimetry (DPIV) under both uniform and distorted inlet flow conditions. A comparison of flow fields reveals that the distorted inlet flow condition makes the compressor flow fields asymmetric. Flow separation and blockage within Distorted Sector A and Transition Sector B are more severe compared to Sector C. The distorted Sector A and Transition Sector B are the key regions that degrade compressor performance and stability. The large axial velocity makes the flow field within the Undistorted Sector C vigorous, which helps to suppress flow separation and blockage. Compressor rotor blades experience loading and unloading in a revolution period and the compressor exhibits strong dynamic response when it operates under distorted inlet flow conditions. Time-related pressure signals acquired at the rotor exit are utilized to analyze the development of the stall disturbance and the stall characteristic of the compressor. The development period of the stall disturbance is prolonged by the dynamic response of the compressor flow field under the distorted inlet flow condition. Dynamic development of the stall disturbance induced by inlet distortion reduces the compressor stall intensity. The frequency associated with the rotating stall cell is related to the rotating velocity of stall cells, which keeps the same value for uniform and distorted inlet flow conditions. Consequently, the stall inception of the compressor is influenced by the distorted inlet flow condition. The disturbance initiated in Distorted Sector A will experience development and damping when it propagates circumferentially, and might fail to survive the damping within Undistorted Sector C. Stall inception occurs only when the damping within Undistorted Sector C is insufficient to prevent its growth. The dynamic development of the disturbance can reasonably explain the influence of inlet distortion on compressor performance.

Temperature Effect on Particle Dynamics and Erosion in Radial Inflow Turbine

1988 ◽  
Vol 110 (2) ◽  
pp. 258-264 ◽  
Author(s):  
W. Tabakoff ◽  
A. Hamed
Keyword(s):  
Temperature Effect ◽  
Gas Turbines ◽  
Particle Dynamics ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Cold Flow ◽  
Erosion Rates ◽  
Radial Inflow Turbine ◽  
Turbine Rotors

This paper presents the results of an investigation of the particle dynamics and the resulting blade erosion in radial inflow turbine rotors. In order to determine the influence of the temperature, the computations were performed for cold and hot inlet flow conditions. The results indicate that the trajectories of these small 5-μm ash particles are quite sensitive to the flow temperatures. In addition, gas turbines operating under hot flow are subjected to higher local blade erosion rates compared to cold flow conditions.

scholarly journals Experimental Investigations of the Influence of Incoming Wakes on the Losses of a Linear Turbine Cascade

1993 ◽  
Author(s):  
M. Ladwig ◽  
L. Fottner
Keyword(s):  
Suction Side ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Low Reynolds Numbers ◽  
Blade Passage ◽  
Inlet Conditions ◽  
Hot Film

The objective of this work is to enhance the understanding of the influence of wake induced non-uniform, steady inlet flow conditions on the profile losses of highly-loaded turbines. For different Reynolds numbers wake and profile pressure distribution measurements were carried out on a linear subsonic turbine cascade as well as measurements with a single sensor hot-film probe. The non-uniform inlet flow were simulated with two different cascades of cylindrical bars. The measurements with various circumferential positions of the incoming wakes relative to the turbine cascade show at low Reynolds numbers a decrease of the losses compared to uniform inlet conditions, because no separation of the suction side boundary layer occurs. With increasing Reynolds numbers the non-uniform inlet flow conditions cause an increase in the losses compared to uniform inlet conditions, due to the forward shift of transition. Generally, the smallest influence of the non-uniform incoming flow can be observed when the wakes enter the cascade inlet plane between the pressure-side of the profiles and the middle of the blade passage. Incoming wakes have the highest influence when they enter the blade passage near to the suction side of the profiles.

Performances of Centrifugal Compressor Impellers in Steady and Unsteady Flow Regimes Under Inlet Flow Distortions

2001 ◽  
Author(s):  
V. Michelassi ◽  
S. Pazzi ◽  
S. Echtner ◽  
P. Giangiacomo ◽  
F. Martelli ◽  
...  
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Total Pressure ◽  
Characteristic Curve ◽  
Flow Coefficient ◽  
Centrifugal Impeller ◽  
Load Factor ◽  
Inlet Distortion ◽  
Inlet Conditions ◽  
Operational Range

The performance of a centrifugal impeller is predicted under steady ideal axial inlet conditions. The operational range is given in terms of load and flow coefficient and polytropic efficiency. The flow field at the exit of the impeller is analyzed to show how it deteriorates while moving close to the stall limit of the characteristic curve. The effect of a strong inlet distortion obtained by intentionally altering the geometry of an inlet volute on the impeller is analyzed. The investigation is carried out for two different distortions, without and with pre swirl, and for two pressure ratios, close to the design point and close to the stall limit of the operational range. The effect of the distortion is analyzed by both a quasi-steady and unsteady approaches. The first method, while faster, is found to give results in partial disagreement with the fully unsteady analysis and is therefore abandoned. The impeller under unsteady distorted inlet is found to have degraded performances in terms of efficiency and load factor, but the overall operational range seems not be significantly affected by the fluctuations of inlet total pressure and angles.

Flow Measurements in a Fishtail Diffuser With Strong Curvature

1999 ◽  
Vol 121 (2) ◽  
pp. 410-417 ◽  
Author(s):  
M. I. Yaras
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Secondary Flows ◽  
Total Pressure Loss ◽  
Cross Sectional ◽  
Inlet Flow ◽  
Inlet Conditions ◽  
Strong Curvature

The paper presents detailed measurements of the incompressible flow development in a large-scale 90 deg curved diffuser with strong curvature and significant streamwise variation in cross-sectional aspect ratio. The flow path approximates the so-called fishtail diffuser utilized on small gas turbine engines for the transition between the centrifugal impeller and the combustion chamber. Two variations of the inlet flow, differing in boundary layer thickness and turbulence intensity, are considered. Measurements consist of three components of velocity, static pressure and total pressure distributions at several cross-sectional planes throughout the diffusing bend. The development and mutual interaction of multiple pairs of streamwise vortices, redistribution of the streamwise flow under the influence of these vortices, the resultant streamwise variations in mass-averaged total-pressure and static pressure, and the effect of inlet conditions on these aspects of the flow are examined. The strengths of the vortical structures are found to be sensitive to the inlet flow conditions, with the inlet flow comprising a thinner boundary layer and lower turbulence intensity yielding stronger secondary flows. For both inlet conditions a pair of streamwise vortices develop rapidly within the bend, reaching their peak strength at about 30 deg into the bend. The development of a second pair of vortices commences downstream of this location and continues for the remainder of the bend. Little evidence of the first vortex pair remains at the exit of the diffusing bend. The mass-averaged total pressure loss is found to be insensitive to the range of inlet-flow variations considered herein. However, the rate of generation of this loss along the length of the diffusing bend differs between the two test cases. For the case with the thinner inlet boundary layer, stronger secondary flows result in larger distortion of the streamwise velocity field. Consequently, the static pressure recovery is somewhat lower for this test case. The difference between the streamwise distributions of measured and ideal static pressure is found to be primarily due to total pressure loss in the case of the thick inlet boundary layer. For the thin inlet boundary layer case, however, total pressure loss and flow distortion are observed to influence the pressure recovery by comparable amounts.

Experimental Investigation of Gas Turbine Axial Diffuser Performance: Part I — Parametric Analysis of Influential Variables

2020 ◽  
Author(s):  
Kenneth Brown ◽  
Stephen Guillot ◽  
Wing Ng ◽  
Lee Iksang ◽  
Kim Dongil ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Mach Number ◽  
Gas Turbines ◽  
Axial Flow ◽  
Flow Distribution ◽  
Initial Study ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Viscous Loss ◽  
Exit Mach Number

Abstract An experimental investigation of the effect of inlet flow conditions and improved geometries on the performance of modern axial exhaust diffusers of gas turbines has been completed. As the first of a two-part series, this article concentrates on characterizing diffuser sensitivity to parametric variations in internal geometry and inlet flow conditions. Full-factorial experiments were carried out on five parameters including the inlet Mach distribution, shape of the support struts, shape of the oil-drain strut, diffuser hade angle, and the hubcap configuration. To enable an efficient sweep of the design space, experiments were performed in this initial study at a down-scaled turbine exit Reynolds number (ReH roughly 3% of the value for an H-class diffuser) and at a full-scale turbine exit Mach number. The study was accomplished in a continuous, cold-flow wind tunnel circuit, and tailored distributions of Mach number, swirl velocity, and radial velocity derived from on-design conditions of an industry diffuser were generated. Measurements included 5-hole probe traverses at planes of interest. Diffuser performance was most sensitive to the inlet Mach distribution with losses of 0.081 points of pressure recovery due to a nonuniform Mach distribution with higher velocity near the hub versus a uniform one. Detailed comparisons of axial flow variation for a top-performing configuration versus related configurations shed physical insight regarding the evolution of kinetic energy distortion into viscous loss in the wake, as well as highlight the benefit of uniform inlet profiles in practice despite the lower theoretical recovery of such cases. The results presented here isolate the inlet flow distribution as a parameter of high interest for further study which is carried out for both on- and off-design conditions in the companion article [1].

Experimental Investigation of Gas Turbine Axial Diffuser Performance: Part II — Effect of Inlet Flow Profiles at On- and Off-Design Conditions

2021 ◽  
Author(s):  
Kenneth Brown ◽  
Stephen Guillot ◽  
Wing Ng ◽  
Lee Iksang ◽  
Kim Dongil ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Flow Visualization ◽  
Gas Turbines ◽  
Full Scale ◽  
Flow Conditions ◽  
Inlet Flow ◽  
Flow Angle ◽  
Companion Article ◽  
Pressure Distributions ◽  
Physical Insight

Abstract An experimental investigation of the effect of inlet flow conditions and improved geometries on the performance of modern axial exhaust diffusers of gas turbines has been completed. The first article in the two-part series [1] leveraged a scaled model to examine parametric variations in both diffuser geometry and inlet flow conditions with the latter having significant consequences for diffuser performance. This second article pivots on the conclusions of the companion article and offers findings and physical insight on diffuser performance for on- and off-design inlet flow conditions. Using a high-performing diffuser design from the companion article, an experimental investigation is carried out with tailored distributions of inlet Mach distribution, inlet swirl angle, and inlet radial flow angle which are designed to replicate conditions of an industry diffuser at various loads. Six different inlet distributions were investigated including a design condition and five other conditions which feature mass flows both greater than and less than the design condition. The measurements were taken at near full-scale turbine exit Reynolds number (ReH roughly 39% of the value for an H-class diffuser) and at full-scale turbine exit Mach number. The study was accomplished in a blow-down, cold-flow wind tunnel facility, and measurements included 5-hole probe traverses at planes of interest, axial pressure distributions, strut pressure distributions, and oil-flow visualization. Over the range of inlet conditions studied, pressure recovery at the exit varied by up to 68.5% from that of on-design operation. Tracking of performance coefficients along the axial direction suggested the existence of flow phenomena which were in some cases able to be confirmed with on-strut pressure measurements and flow visualization. In addition to physical insight, the results presented here offer an experimental benchmark for the sensitivity of diffuser performance to inlet flow conditions.

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