Experimental Research on Inlet Steady Swirl Distortion in an Axial Compressor with Non-Uniform Tip Clearance

The inlet swirl distortion and non-uniform tip clearance have great effects on aero-engine performance and stall margin.In this paper,the effects of paired swirl distortion on the aerodynamic stability and stall inception of a single stage axial compressor with non-uniform tip clearance are quantitatively analyzed by using the swirl distortion descriptors.The experimental results show that the paired swirl distortion dominated by co-rotating swirl improves the stability of the axial compressor.For a single-stage axial compressor with eccentricity of 100%,the stall inception starts at the maximum tip clearance with clean inlet.The initial position of the stall inception is determined by the maximum tip clearance when the small intensity paired swirl distortion exists at the compressor inlet.As the swirl intensity increases,it shifts towards the position of the counter rotating swirl vortex core.The inlet swirl will not change the type of stall inception.

Calibration of S-duct Swirl Distortion Based on Vortex Identification Methods

The S-shape inlet has been widely used in advanced military aircraft due to their advantage of reducing radar signature.However,the curvature of the inlet usually causes different kinds of intake distortion at the aerodynamic interface plane(AIP).Among them,the swirl distortion has been seriously concerned because of its great impact on the performance and stability of aero-engines.There is still no universal criterion for assessing the stability of compressors in the condition of strong swirl distortion.As an approach of assessing the swirl intensity and pattern,vortex identification method may be used as an auxiliary method for stability analysis.In this paper,numerical and experimental investigations on different S-ducts were carried out.The axial vorticity component and g criterion were used to analyze the quantitative correlation between geometry and swirl intensity.It was found that there is a relatively strong correlation between the geometry,the axial vorticity component and the Q criterion.The present investigation may provide a quick reconstruction method to model the effect of S-ducts for compressor stability prediction.

Design Optimization of Non-Axisymmetric Vane for an Axial Compressor under Inlet Distortion

The flow field at the inlet of compressors is generally encountered combined total pressure and swirl distortion for either aircraft engine with S-duct or gas turbine with lateral air intake.This inevitably deteriorates compressor aerodynamic performance,including not only the efficiency or pressure ratio but also the operation stability.In order to conquer this issue,appropriate measures such as integrating flow control techniques and modifying inlet or compressor design are of benefits.Due to this motivation,this article develops a full-annular two-dimensional(2D)and a partial-annular three-dimension(3D)optimization strategy for non-axisymmetric vane design.Firstly,two numerical simulation methods for evaluating performance of full-annular 2D vane and compressor with partial-annular 3D vane are developed.The swirl patterns at the inlet of a 1.5-stage axial compressor are analyzed and parametrized,and the parameterization is transferred to characterize the circumferential distribution of geometrical parameters of the vane profile.These approaches dramatically reduce computational simulation costs without violating the non-axisymmetric flow distortion patterns.Then various full-annular 2D sections at different radial locations are constructed as design space.The designed vane is reconstructed and 3D numerical simulations are performed to examine performance of the non-axisymmetric vane and the compressor with it.Also,partial annular 3D optimization is conducted for balancing compressor efficiency and stall margin.Results indicate that the designed non-axisymmetric vane based on full-annular optimization approach can decrease the vane total pressure loss under the considered inlet flow distortion,while those using partial-annular optimization achieve positive effects on compressor stall margin.