High-speed Multistage Compressor Research Articles

Effect of rotor blade tip clearance on aerodynamic performance of high-speed multi-stage axial compressor

Effect of rotor blade tip clearance on aerodynamic performance of high-speed multi-stage axial compressor

The Characteristics and Mechanisms of High-Intensity Sound in a High-Speed Multistage Compressor

An experiment with a multistage high-speed compressor is conducted to investigate the high noise with abnormal blade vibration. Different points are selected to monitor the noise in the compressor and the amplitude of blade vibration. The evolution rhythm of sound frequency and sound pressure level against speed is captured. The relation between the vibration and the noise is obtained. A research method based on an acoustic analogy is developed to investigate the characteristics and mechanisms of high-intensity sound in a rectangular cavity pipeline. The calculated distribution of the first four-order acoustic mode inside the rectangular cavity pipe is consistent with the results in the literature, and the maximum calculation error of the acoustic mode frequency value is 2.7%, which certifies the effectiveness of the method. A simplified compressor model is established to study the vortex system and the sound field characteristics of this method when high-intensity sound occurs. The results present the motion law of shedding vortices with high-intensity sound, and the calculation error of the frequency corresponding to the high-intensity sound is 3.6%. The “frequency-locked phase-locked” characteristics (i.e., character frequency) keep constant at a range of velocities, showing similarity with the phenomenon obtained in experiment above, and beta mode forms of Parker are captured. The study in the present paper makes a contribution for the cognition of mechanisms with high-intensity sound in aeroengine compressors.

Deficiencies in the Spalart–Allmaras Turbulence Model for the Prediction of the Stability Boundary in Highly Loaded Compressors

Abstract Reynolds-averaged Navier–Stokes (RANS) equations are employed for aerodynamic and aeroelastic modeling in axial compressors. Their solutions are highly dependent on the turbulence models for closure. The main objective of this work is to assess the widely used Spalart–Allmaras model suitability for high-speed compressor flows. For this purpose, an extensive investigation of the sources of uncertainties in a high-speed multi-stage compressor rig was carried out. The grid resolution near the casing end wall, which affects the tip leakage flow and casing boundary layer, was found to have a major effect on the stability limit prediction. Refinements in this region led to a stall margin loss prediction. It was found that this loss was exclusively due to the destruction term in the SA model.

Observations on Rotating Instabilities and Spike Type Stall Inception in a High-Speed Multistage Compressor

This work investigates high-frequency measurements for the contribution to the understanding of different stall inception types in high-speed multistage compressors. A 3.5-stage high-speed axial multistage compressor is investigated with a 2 MW test rig in the Laboratoire de Mécanique des Fluides et d’Acoustique (LMFA) at Ecole Centrale de Lyon, France. Two different types of instabilities arise in this compressor as a function of shaft speed. At part speed, a controversy called “rotating instability” type flow field modulation is identified with the measurements. New results are the demonstration of the periodic behavior of this instability and the analogy to classical frequency modulation, periodic to one revolution of the instability. Furthermore, the amplitude of the instability is modulated by the time period of a rotor revolution. At nominal speed, the abrupt spike type stall inception is detected, taking usually less than five rotor revolutions.

Development of body force model for steady inlet distortions in high-speed multistage compressor

This study aims at establishing a three-dimensional numerical model, compressor aerodynamic performance analysis model, to simulate the impact of complicated distorted flow on multistage axial flow compressor based on the body force model. The model solves the compressible three-dimensional Euler equations, which are modified to include source terms representing the effect of the blade rows. In this study, the association between blade source terms and entry Mach number together with attack angle could be established with the deviation angle model and loss model. In this paper, compressor aerodynamic performance analysis model is used to evaluate the effect of inlet circumferential total pressure distortion and swirl distortion on a five-stage high-pressure compressor. Calculated operating maps for compressor agree well with the experimental results. Meanwhile, the traveling process of inlet distortions in the multistage compressor is correctly revealed. The wide application prospect of the model can be seen in the area of inlet distortion problems.

Investigation of Flow Instability Mechanism Causing Compressor Rotor-Blade Nonsynchronous Vibration

This paper investigates the aerodynamic excitation mechanism of the rotor-tip flow instabilities leading to nonsynchronous vibration in a high-speed multistage axial compressor. Numerical simulations for the one-seventh annulus periodic sector of 1-1/2 stage are performed using an unsteady Reynolds-averaged Navier–Stokes solver with a fully conservative, sliding interface, boundary condition to capture wake propagation between adjacent blade rows. The present numerical simulations for rigid blades demonstrate that the tip flow instability is the main cause of the compressor nonsynchronous vibration excitation and is generated by the circumferentially traveling vortices. The frequency of the vortex passing each blade in the counter-rotation direction is roughly equal to the nonsynchronous vibration excitation frequency. Three different rotor-tip clearance sizes and shapes are studied. The nonsynchronous vibration excitation frequency and amplitude vary slightly with the tip clearance size when the clearances have the same flat shape, but they change substantially when the tip clearance has a convex-type shape. The predicted nonsynchronous vibration excitation frequency is in excellent agreement with the rig testing.

Experimental and Computational Methods for Flow Investigation in High-Speed Multistage Compressor

This study takes place in the frame of a research project to better understand the flow that develops in multistage high-speed compressors. First, the paper presents the high-speed 3.5-stage compressor CREATE and the methods that are considered to increase the data reliability and the investigation capability with such realistic compressors. Second, flow simulations, achieved with three-dimensional unsteady Reynolds-averaged Navier-Stokes computations over the whole compressor spatial and temporal periodicities, are analyzed through a study of their sensitivity to some parameters such as the inlet conditions, the space and time discretization, and technological effects such as tip and hub clearances. Finally the paper focuses on the methodology used to compare the experimental and numerical results over the whole compressor periodicities. The local spatial and temporal flow structures are well estimated. The key is the advection of these structures, which interact with each other and produce a significant part of the flow fluctuations in the downstream stages. The paper presents the zone close to the casing, where losses and blockage are induced by the interaction between the tip leakage flow and the incoming wakes. This is where the numerical simulation has to be improved, in order to accurately predict the performance.

Experimental and Computational Methods for Flow Investigation in High-Speed Multistage Compressor

Experimental and Computational Methods for Flow Investigation in High-Speed Multistage Compressor

Numerical simulation of flow instabilities in high speed multistage compressors

In the present paper, a nonlinear multi “actuator disk” model is proposed to analyze the dynamic behavior of flow instabilities, including rotating stall and surge, in high speed multistage axial compressors. The model describes the duct flow fields using two dimensional, compressible and unsteady Euler equations, and accounts for the influences of downstream plenum and throttle in the system as well. It replaces each blade row of multistage compressors with a disk. For numerical calculations, the time marching procedure, using MacCormack two steps scheme, is used. The main purpose of this paper is to predict the mechanism of two dimensional short wavelength rotating stall inception and the interaction between blade rows in high speed multistage compressors. It has been demonstrated that the model has the ability to predict those phenomena, and the results show that some system parameters have a strong effect on the stall features as well. Results for a five stage high speed compressor are analyzed in detail, and comparison with the experimental data demonstrates that the model and calculating results are reliable.

Stall Inception Measurements in a High-Speed Multistage Compressor

This paper presents unsteady measurements taken in a high-speed four-stage aeroengine compressor prior to the onset of aerodynamic flow instabilities. In this experiment, 40 fast-response pressure transducers have been located at various axial and circumferential positions throughout the machine in order to give a very detailed picture of stall inception. At all the compressor speeds investigated, the stall pattern observed is initiated by a very short length-scale finite-amplitude disturbance, which propagates at a fast rate around the annulus. This initial stall cell leads to a large-amplitude system instability in less than five rotor revolutions. Varying the IGV setting angle is found to have a strong influence on the axial location of the first disturbance detected. In particular, transferring the aerodynamic loading from front to downstream stages moves the first disturbance detected from the first to the last stage of the compressor. Other repeatable features of the stall inception pattern in this compressor have been identified using a simple analysis technique particularly appropriate to the study of short length-scale disturbances. It is found that the origins of instabilities are tied to particular tangential positions in both the stationary and rotating frames of reference. These measurements lead to the conclusion that the stall inception process in high-speed multistage compressors can be characterized by some very local and organized flow phenomena. Moreover, there is no evidence of prestall waves in this compressor.

A New Endwall Model for Axial Compressor Throughflow Calculations

It is well recognized that the endwall regions of a compressor—in which the annulus wall flow interacts with the mainstream flow—have a major influence on its efficiency and surge margin. Despite many attempts over the years to predict the very complex flow patterns in the endwall regions, current compressor design methods still rely largely on empirical estimates of the aerodynamic losses and flow angle deviations in these regions. This paper describes a new phenomenological model of the key endwall flow phenomena treated in a circumferentially averaged way. It starts from Hirsch and de Ruyck’s annulus wall boundary layer approach, but makes some important changes. The secondary vorticities arising from passage secondary flows and from tip clearance flows are calculated. Then the radial interchanges of momentum, energy, and entropy arising from both diffusion and convection are estimated. The model is incorporated into a streamline curvature program. The empirical blade force defect terms in the boundary layers are selected from cascade data. The effectiveness of the method is illustrated by comparing the predictions with experimental results on both low-speed and high-speed multistage compressors. It is found that the radial variation of flow parameters is quite well predicted, and so is the overall performance, except when significant endwall stall occurs.

A Fiber Optic Probe for Gas Total Temperature Measurement in Turbomachinery

This paper describes the design, operation, construction, and demonstration of a new type of high-bandwidth unsteady temperature sensor based on fiber optics, and capable of operating in a high-speed multistage research compressor with flow representative of jet engine conditions. The sensing element is an optical coating of zinc selenide deposited on the end of an optical fiber. During evaluation in aerodynamic testing, a 1 K gas temperature resolution was demonstrated at 9.6 kHz and an upper bandwidth limit of 36 kHz achieved.

Rotating stall performance and recoverability of a high-speed 10-stage axial flow compressor

Design factors which influence rotating stall recoverability of a high-speed multistage compressor are not yet fully understood. A high-speed, 10-stage compressor component was tested while operating in-stall to investigate parameters that affect the overall recoverability of a multistage compressor. The compressor instrumentation and data acquisition procedures were designed to obtain detailed performance data from the compressor while it entered into a rotating stall condition and while it operated in rotating stall. The compressor was tested at different in-stall operating conditions by varying compressor shaft speed, discharge throttle, and variable geometry settings to determine the effect of each variable on rotating-stall performance and recoverability. Test results suggest that the stall cell may not extend the full length of the compressor but instead can be confined to a portion (here the rear stages) of the compressor. When stages are stacked together, as is the case in a multistage compressor, the stalled performance and subsequent recoverability are greatly affected by how well the stages of the compressor are matched. The results also suggest that high-speed flows in the tenth stage may extend in-stall operation causing low recoverability of the overall test compressor at higher shaft speeds.

Unsteady Viscous Flow in a High-Speed Core Compressor

A probe incorporating a miniature high-frequency response pressure transducer has been traversed behind the first three stages of a high-speed multistage compressor operating at throttle settings corresponding to near choke, peak efficiency, and near surge. A novel method of compensating for transducer temperature sensitivity was employed. Consequently, time-averaged pressures derived from the transducer were found to be in good agreement with pneumatic pressure measurements. Analysis of the unsteady pressure measurements revealed both the periodic and random fluctuations in the flow field. This provided information on rotor-rotor interaction effects and the nature of viscous blade wake and secondary flows in each stage.

Experimental Investigation of Rotating Stall in a Mismatched Three-Stage Axial Flow Compressor

This paper reports on an examination of rotating stall in a low-speed three-stage axial flow compressor operating with various degrees of stage mismatch. The objective of this study was to simulate the mismatching that occurs in high-speed multistage compressors when operating near surge. The study of the stall zones involved the use of fast response measurement techniques. The study clearly shows how stages can operate in an axisymmetric fashion even when heavily stalled, since rotating stall inception requires the stall of more than one stage. The study also compares conditions required for full-span and part-span stall and suggests that the part-span stall structure is more relevant to high-speed multistage compressors.