Correlation Measure-Based Stall Margin Estimation for a Single-Stage Axial Compressor

2011 ◽  
Author(s):  
Yuan Liu ◽  
Manuj Dhingra ◽  
J. V. R. Prasad
Keyword(s):  
Steady State ◽  
Axial Compressor ◽  
Operating Point ◽  
Characteristic Line ◽  
Estimation Technique ◽  
Correlation Measure ◽  
Stall Margin ◽  
Estimation System ◽  
Design Speed ◽  
Speed Characteristic

This paper presents a method for estimating compressor stall margin and the results of applying the estimation technique to an axial compressor rig. Stall margin estimation is accomplished through the use of a compressor stability detection parameter called the “correlation measure.” The correlation measure captures the periodicity of the pressure in the rotor tip region of the compressor. The downcrossing frequency of the correlation measure across some preset threshold is measured while operating the compressor rig at various steady-state points along the design speed characteristic line. These measurements are used to generate a relationship with stall margin as a function of downcrossing frequency. The estimation technique is evaluated by applying it while dynamically ramping the operating point of the compressor up the design speed line towards surge. A brief investigation on the effects of inlet distortions on the correlation measure-based estimation system is also given.

Correlation Measure-Based Stall Margin Estimation for a Single-Stage Axial Compressor

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Yuan Liu ◽  
Manuj Dhingra ◽  
J. V. R. Prasad
Keyword(s):  
Steady State ◽  
Axial Compressor ◽  
Operating Point ◽  
Characteristic Line ◽  
Estimation Technique ◽  
Correlation Measure ◽  
Stall Margin ◽  
Estimation System ◽  
Design Speed ◽  
Speed Characteristic

This paper presents a method for estimating compressor stall margin and the results of applying the estimation technique to an axial compressor rig. Stall margin estimation is accomplished through the use of a compressor stability detection parameter called the “correlation measure.” The correlation measure captures the periodicity of the pressure in the rotor tip region of the compressor. The downcrossing frequency of the correlation measure across some preset threshold is measured while operating the compressor rig at various steady-state points along the design speed characteristic line. These measurements are used to generate a relationship with stall margin as a function of downcrossing frequency. The estimation technique is evaluated by applying it while dynamically ramping the operating point of the compressor up the design speed line towards surge. A brief investigation on the effects of inlet distortions on the correlation measure-based estimation system is also given.

CFD Analysis of Effects of Damage Due to Bird Strike on Fan Performance

2010 ◽  
Author(s):  
Baizura Bohari ◽  
Abdulnaser Sayma
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Structural Integrity ◽  
Operating Point ◽  
Computational Techniques ◽  
Test Case ◽  
Base Line ◽  
Bird Strike ◽  
Stall Margin ◽  
Speed Characteristic

Bird ingestion has been a hazard that affects the structural integrity and survivability of turbofan engines. It can result in deformation of one or more fan blades, in which case, the engine is likely to surge and not recover. Numerical studies and simulations of bird strikes have become essential to optimize the design of engine components simultaneously to increase the engine capabilities for acceptable damage tolerance. Good understanding of these phenomena and the implications on the behaviour of the flow field with respect to the damage affecting the fan blades are usually investigated using computational techniques and/or experimental methods. The purpose of this paper is to present a Computational Fluid Dynamics (CFD) method for the analysis of the aerodynamic behaviour of an aero-engine fan affected by a bird strike. NASA rotor 67 was used as a test case because of the availability of experimental data that can be used to calibrate the model for the undamaged fan. The undamaged fan characteristic was mapped using a modification to the methodology developed by Sayma (2007). In this method a downstream variable throttle is added which allows changing the operating point on the speed characteristic without having to change downstream boundary conditions. This approach allows for changes in fan operating point to come out of the calculation as opposed to those dictated by the downstream static pressure boundary conditions used in typical computations. The methodology is automated allowing for a sweep along a speed characteristic or along a working line in one calculation in the same way as a rig test is conducted. Agreement with experimental data when available was excellent. This provided the base line for the undamaged blades. A damaged blade was inserted among undamaged blades in the fan assembly and the fan characteristic was mapped for a range of rotational speeds. Two different degrees of damage were analysed in an attempt to establish a correlation between the extent of the damage and the locus of the stall boundary. It was found that small increments on the damage lead to significant reduction in stall margin particularly at higher rotational speeds.

Impact of Sweep on Part Speed Performance of an Axial Compressor Rotor With Circumferential Casing Grooves

2019 ◽  
Author(s):  
Shraman Goswami ◽  
M. Govardhan
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Field Investigation ◽  
Performance Comparison ◽  
Rotor Blades ◽  
Stall Margin ◽  
Compressor Rotor ◽  
Design Speed

Abstract High performance and increased operating range of an axial compressor is obtained by employing three-dimensional design features, such as sweep, as well as shroud casing treatments, such as circumferential casing grooves. A number of different rotor blades with different amounts of sweeps and different sweep starting spans are studied at design speed. Different swept rotors, including zero sweep, are derived from Rotor37 rotor geometry. In the current study the best performing rotor with sweep is analyzed at part speed. The analyses were done for baseline rotor, devoid of any sweep, and with and without circumferential casing grooves. A detailed flow field investigation and performance comparison is presented to understand the changes in flow field at part speed. It is found that that at 100% design speed, stall margin improvement is achived by both sweep and casing grooves, but at 90% speed improvement in stall margin due to sacing groove is very minimal over and above the gain due to sweep. It is also noticed that due to reduced shock loss efficiency is higher at 90% speed than at 100% speed.

Numerical Investigation on Effect of Compressor Performance in Single Rotor With Micro-Vortex Generator

2017 ◽  
Author(s):  
Shan Ma ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Jinhua Lang ◽  
Haiyang Kuang
Keyword(s):  
Secondary Flow ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Axial Flow ◽  
Flow Simulation ◽  
Vortex Generator ◽  
Leading Edge ◽  
Future Research ◽  
Characteristic Line ◽  
Design Speed

The performance of axial compressor is considerably influenced by secondary flow, like corner separation between wall and blade in a compressor stage. An extensive experimental study of vortex generator (VG) applied on axial compressor was conducted by many scholars, in order to control these effects and improve the aerodynamic performance. According to their size, they are classified as traditional VGs (h/δ>0.5) and Micro-vortex generators (MVGs, h/δ = 0.1∼0.5).MVGs is one of the hot spots of present research to restrain the secondary flow. In order to investigate the effect of MVGs used in rotor, this study was carried out on Northwestern Polytecnical University rotor (NPU rotor), which is a subsonic axial flow compressor rotor. The Vane-MVGs were placed at a distance of 11% chord length ahead of the leading edge on the end-wall. The characteristic line of 54% (8130RPM), 71% (10792RPM) and 84% (12768RPM) design speed were calculated by steady 3D RANS simulations with Spalart-Allmar turbulence model and compared with the corresponding MVGs cases, respectively. Results show that the stall margins of the 3 speeds with MVGs were larger than baseline, but the efficiency and pressure ratio were reduced in different degrees. In this paper, the flow characteristics at 54% (8130RPM) design speed and the development process of vortex generated by MVGs are analyzed in detail. The influence of MVGs height and stagger angle on rotor performance is also discussed. Moreover, flow simulation of MVGs used on axial compressor single rotor’s hub offered a guideline to future research.

Effect of Backward Sweep on Aerodynamic Performance of a 1.5-Stage Highly Loaded Axial Compressor

2020 ◽  
Author(s):  
Song Huang ◽  
Chuangxin Zhou ◽  
Chengwu Yang ◽  
Shengfeng Zhao ◽  
Mingyang Wang ◽  
...  
Keyword(s):  
Total Pressure ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Blade Loading ◽  
Stall Margin ◽  
Axial Compressors ◽  
Design Speed ◽  
Total Pressure Ratio ◽  
Highly Loaded

Abstract As a degree of freedom in the three-dimensional blade design of axial compressors, the sweep technique significantly affects the aerodynamic performance of axial compressors. In this paper, the effects of backward sweep rotor configurations on the aerodynamic performance of a 1.5-stage highly loaded axial compressor at different rotational design speeds are studied by numerical simulation. The aim of this work is to improve understanding of the flow mechanism of backward sweep on the aerodynamic performance of a highly loaded axial compressor. A commercial CFD package is employed for flow simulations and analysis. The study found that at the design rotational speed, compared with baseline, backward sweep rotor configurations reduce the blade loading near the leading edge but slightly increases the blade loading near the trailing edge in the hub region. As the degree of backward sweep increases, the stall margin of the 1.5-stage axial compressor increase first and then decrease. Among different backward sweep rotor configurations, the 10% backward sweep rotor configuration has the highest stall margin, which is about 2.5% higher than that of baseline. This is due to the change of downstream stator incidence, which improves flow capacity near the hub region. At 80% rotational design speed, backward sweep rotor configurations improve stall margin and total pressure ratio of the compressor. It’s mainly due to the decreases of the rotor incidence near the middle span, which results in the decreases of separation on the suction surface. At 60% rotational design speed, detached shock disappears. Backward sweep rotor configurations deteriorate stall margin of the compressor, but increase total pressure ratio and adiabatic efficiency when the flow rate is lower than that at peak efficiency condition. Therefore, it’s necessary to consider the flow field structure of axial compressors at whole operating conditions in the design process and use the design freedom of sweep to improve the aerodynamic performance.

scholarly journals Effects of Non-Axisymmetric Tip Clearance on Axial Compressor Performance and Stability

1997 ◽  
Author(s):  
M. B. Graf ◽  
T. S. Wong ◽  
E. M. Greitzer ◽  
F. E. Marble ◽  
C. S. Tan ◽  
...  
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Peak Pressure ◽  
Good Description ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Maximum Efficiency ◽  
Stall Margin ◽  
Compressor Performance

The effects of circumferentially non-uniform lip clearance on axial compressor performance and stability have been investigated experimentally and analytically. A theoretical model for compressor behavior with non-axisymmetric tip clearance has been developed and used to design a series of first-of-a-kind experiments on a four-stage, low speed compressor. The experiments and computational results together show clearly the central physical features and controlling parameters of compressor response to non-axisymmetric lip clearance. It was found that the loss in stall margin was more severe than that estimated based on average clearance. The stall point was, in fact, closer to that obtained with uniform clearance at the maximum clearance level. The circumferential length scale of the tip clearance (and accompanying flow asymmetry) was an important factor in determining the stall margin reduction. For the same average clearance, the loss in peak pressure rise was 50% higher for an asymmetry with fundamental wavelength equal to the compressor circumference than with wavelength equal to one-half the circumference. The clearance asymmetry had much less of an effect on peak efficiency; the measured maximum efficiency decrease obtained was less than 0.4 percent compared to the 8% decrease in peak pressure rise due to the asymmetric clearance. The efficiency penalty due to non-axisymmetric tip clearance was thus close to that obtained with a uniform clearance at the circumferentially-averaged level. The theoretical model accurately captured the decreases in both steady-state pressure rise and stable operating range which are associated with clearance asymmetry. It also gave a good description of the observed trends of (i) increasing velocity asymmetry with decreasing compressor flow, and (ii) decreasing effect of clearance asymmetry with decreasing dominant wavelength of the clearance distribution. The time resolved data showed that the spatial structure of the pre-stall propagating disturbances in the compressor annulus was well represented and that the stability limiting process could be linked to the unsteady structure of these disturbance modes. The model was also utilized for parametric studies to define how compressor performance and stability is affected by the circumferential distribution of clearance, steady-state compressor pressure-rise characteristic, and system dynamic parameters. Sensitivity to clearance asymmetry was found to fall off strongly with the (asymmetry-related) reduced frequency and to increase with peak pressure rise and increasing curvature of the characteristic near the peak.

Three-Dimensional Aerodynamic Optimization of a Multi-Stage Axial Compressor

2016 ◽  
Author(s):  
Tao Ning ◽  
Chun-wei Gu ◽  
Xiao-tang Li ◽  
Tai-qiu Liu
Keyword(s):  
Genetic Algorithm ◽  
Surrogate Model ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Optimization Method ◽  
Operating Point ◽  
Design Parameters ◽  
Aerodynamic Optimization ◽  
Stall Margin

An optimization method combined of a genetic algorithm, an artificial neural network, a CFD solver and a blade generator, is developed in this research and applied in the three-dimensional blading design of a newly designed highly-loaded 5-stage axial compressor. The adaptive probabilities of crossover and mutation, non-uniform mutation operator and elitism operator are employed to improve the convergence of the genetic algorithm. Considering both the optimization efficiency and effectiveness, a mixture of high-fidelity multistage CFD method and approximate surrogate model of the feed-forward ANN is used to evaluate the fitness. In particular, the database is updated dynamically and used to re-train the surrogate model of ANN for improving the accuracy for predicting. The last stator of the compressor is optimized at the near stall operating point. The tip bow with relative bow height Hb and bow angle αb are treated as design parameters. The adiabatic efficiency as well as the penalty of mass flow and total pressure ratio constitute the objective functions to be maximized. The optimum (Hb = 0.881, αb = 14.7°) obtains 0.4% adiabatic efficiency increase for the whole compressor at the optimized operating point. The detailed aerodynamic is compared between the baseline and optimized stator, and the mechanism is analyzed. The optimized version obtains 5.1% increase in stall margin and maintains the efficiency at the design point.

Experimental Study of a High-Throughflow Transonic Axial Compressor Stage

1984 ◽  
Vol 106 (3) ◽  
pp. 552-560 ◽  
Author(s):  
A. J. Wennerstrom
Keyword(s):  
Experimental Study ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Experimental Results ◽  
Vortex Generators ◽  
Compressor Stage ◽  
Stall Margin ◽  
Transonic Axial Compressor ◽  
Design Speed ◽  
Isentropic Efficiency

Design information and experimental results are presented for a transonic axial compressor stage passing 40 lbs/s-ft2 frontal area (195 Kg/s-m2) with a pressure ratio of 1.95 at 1500 ft/s (457 m/s) tip speed. The design incorporates several unusual features that helped it achieve a peak isentropic efficiency over 88 percent at design speed. The compressor was evaluated at three rotor tip clearances and an optimum was found. Vortex generators placed upstream on the casing proved relatively ineffective in influencing stall margin. Vortex generators installed on the rotor did improve stall margin and also increased efficiency at speeds of 90 percent and below.

scholarly journals Effects of Nonaxisymmetric Tip Clearance on Axial Compressor Performance and Stability

1998 ◽  
Vol 120 (4) ◽  
pp. 648-661 ◽  
Author(s):  
M. B. Graf ◽  
T. S. Wong ◽  
E. M. Greitzer ◽  
F. E. Marble ◽  
C. S. Tan ◽  
...  
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Peak Pressure ◽  
Good Description ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Maximum Efficiency ◽  
Stall Margin ◽  
Compressor Performance

The effects of circumferentially nonuniform tip clearance on axial compressor performance and stability have been investigated experimentally and analytically. A theoretical model for compressor behavior with nonaxisymmetric tip clearance has been developed and used to design a series of first-of-a-kind experiments on a four-stage, low-speed compressor. The experiments and computational results together show clearly the central physical features and controlling parameters of compressor response to nonaxisymmetric tip clearance. It was found that the loss in stall margin was more severe than that estimated based on average clearance. The stall point was, in fact, closer to that obtained with uniform clearance at the maximum clearance level. The circumferential length scale of the tip clearance (and accompanying flow asymmetry) was an important factor in determining the stall margin reduction. For the same average clearance, the loss in peak pressure rise was 50 percent higher for an asymmetry with fundamental wavelength equal to the compressor circumference than with wavelength equal to one-half the circumference. The clearance asymmetry had much less of an effect on peak efficiency; the measured maximum efficiency decrease obtained was less than 0.4 percent compared to the 8 percent decrease in peak pressure rise due to the asymmetric clearance. The efficiency penalty due to nonaxisymmetric tip clearance was thus close to that obtained with a uniform clearance at the circumferentially averaged level. The theoretical model accurately captured the decreases in both steady-state pressure rise and stable operating range which are associated with clearance asymmetry. It also gave a good description of the observed trends of: (i) increasing velocity asymmetry with decreasing compressor flow, and (ii) decreasing effect of clearance asymmetry with decreasing dominant wavelength of the clearance distribution. The time-resolved data showed that the spatial structure of the prestall propagating disturbances in the compressor annulus was well represented and that the stability limiting process could be linked to the unsteady structure of these disturbance modes. The model was also utilized for parametric studies to define how compressor performance and stability are affected by the circumferential distribution of clearance, steady-state compressor pressure-rise characteristic, and system dynamic parameters. Sensitivity to clearance asymmetry was found to fall off strongly with the (asymmetry-related) reduced frequency and to increase with peak pressure rise and increasing curvature of the characteristic near the peak.

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