scholarly journals Improving work stability margin by determining the optimal and critical parameters of the axial compressor stages

2015 ◽  
pp. 6-19
Author(s):  
Aleksandr Inozemtsev ◽  
◽  
Evgeniy Guzachev ◽  
Vladimir Kataev ◽  
Andrey Plotnikov ◽  
...  
Keyword(s):  
Axial Compressor ◽  
Stability Margin ◽  
Critical Parameters ◽  
Work Stability

Numerical Investigation on the Effect of Bleed Port With Self-Recirculating Casing Treatment on the Stability of a 1.5-Stage Transonic Compressor

2019 ◽  
Author(s):  
Yiming Zhong ◽  
WuLi Chu ◽  
HaoGuang Zhang
Keyword(s):  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Stability Margin ◽  
Axial Position ◽  
Stable Operation ◽  
Stall Margin ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Compressor Efficiency

Abstract Compared to the traditional casing treatment, the self-recirculating casing treatment (SCT) can improve or not decrease the compressor efficiency while achieving the stall margin improvement. For the bleed port, the main design indicator is to reduce the flow loss caused by suction, while providing sufficient jet flow and jet pressure to the injector. In order to gain a better study of the bleed port stabilization mechanisms, the bleed configuration was parameterized with the bleed port inlet width and the bleed port axial position. Five kinds of recirculating casing treatments were applied to a 1.5-stage transonic axial compressor with the method of three-dimensional unsteady numerical simulation. Fifteen identical self-recirculating devices are uniformly mounted around the annulus. The numerical results show that the SCT can improve compressor total pressure ratio and stability, shift the stall margin towards lower mass flows. Furthermore, it has no impact on compressor efficiency. The optimal case presents that stability margin is improved by 6.7% employing 3.1% of the annulus mass flow. Expanding bleed port inlet width to an intermediate level can further enhance compressor stability, but excessive bleed port inlet width will reduce the stabilization effect. The optimal bleed port position is located in the blocked area of the low energy group at the top of the rotor. In the case of solid casing, stall inception was the tip blockage, which was mainly triggered by the interaction of the tip leakage vortex and passage shock. From radial distribution, the casing treatment predominantly affects the above 70% span. The reduction of tip reflux region by suction effect is the main reason for the extension of stable operation range. The SCT also has an obvious stability improvement in tip blockage stall, while delaying the occurrence of compressor stall.

Compressor Blade and Impeller Rotating Disk Vibration Avoidance Parameters

2000 ◽  
Author(s):  
Frank Kushner
Keyword(s):  
High Cycle Fatigue ◽  
Axial Compressor ◽  
Rotating Disk ◽  
Critical Parameters ◽  
Strain Gages ◽  
Parametric Equation ◽  
Flow Conditions ◽  
Compressor Blades ◽  
Critical Design ◽  
Fatigue Failures

Abstract Interaction of rotating blades with stationary vanes is a prime consideration for disk design and vibration failure investigations. For a well-designed radial-flow impeller with a cover, the structure is inherently resistant to alternating forces at normal flow conditions. Critical parameters are reviewed with respect to excitation and response. A fundamental parametric equation originally published in 1979 is further explained and verified. Comparisons to open impellers and axial compressor blades that have additional critical design considerations are also presented. Data from strain gages on an impeller gave proof that liquid ingestion was the cause of high excitation, and validated the parametric equation for blade/vane interaction. Particular emphasis is given to avoiding high cycle fatigue failures with stages employing vaned diffusers, which are now much more prevalent. Modal analyses, as well as information from other references that confirms theories are included.

A Method for Assessing Effects of Circumferential Flow Distortion on Compressor Stability

1987 ◽  
Vol 109 (3) ◽  
pp. 371-379 ◽  
Author(s):  
T. P. Hynes ◽  
E. M. Greitzer
Keyword(s):  
Flow Instability ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Stability Margin ◽  
Direct Result ◽  
Loss Of Stability ◽  
Flow Distortion ◽  
Stability Calculation ◽  
Reduced Frequency ◽  
Sector Angle

This paper describes the development of a new analysis to predict the onset of flow instability for an axial compressor operating in a circumferentially distorted inlet flow. A relatively simple model is used to examine the influence of various distortions in setting this instability point. It is found that the model reproduces known experimental trends for the loss of stability margin with increasing distortion amplitude and with changes in reduced frequency. In particular, there is a recognizable “critical sector angle” which characterizes loss of stability margin. To the authors’ knowledge, this is the first time the effects described herein have been theoretically demonstrated as the direct result of a fluid dynamic stability calculation.

Effect of J-Shaped Casing Treatment on Flow Stability and Performance of an Axial Compressor

2012 ◽  
Author(s):  
Ramjan R. Pathan ◽  
Quamber H. Nagpurwala ◽  
Ananthesha Bhat
Keyword(s):  
Incidence Angle ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Stability Margin ◽  
Tangential Component ◽  
Favourable Effect ◽  
Slight Reduction ◽  
Stall Margin ◽  
Casing Treatment ◽  
Transonic Compressor

Casing Treatment (CT) is one of the passive methods to increase the stability margin of the compress and hence that of the aircraft jet engines. In this paper, a novel J-shaped axial CT slot geometry is designed and numerically analysed for its effect on the performance of a single stage NACA transonic compressor. The predicted performance of the isolated rotor was validated by comparing with the published experimental results. The predicted efficiency of the baseline transonic rotor agreed well with experimental data, but the total pressure ratio was under predicted over the entire operating range. The J-shaped CT slots, with 100% axial coverage over the rotor tip chord, were able to extend the stall mass flow rate by almost 19.45% compared to the baseline rotor, accompanied with a slight reduction in rotor efficiency by 1.42%. The high pressure air entered the slots at rotor exit and flowed back through the slots and the plenum, and ejected at the rotor inlet to energise the low momentum end wall flow. The interaction of main inlet flow and the ejected flow having large tangential component of velocity, had favourable effect on the rotor incidence angle, and hence on rotor stall margin.

Effects of Using Hydrogen-Rich Syngas in Industrial Gas Turbines While Maintaining Fuel Flexibility on a Multistage Axial Compressor Design

2012 ◽  
Author(s):  
Pascal Nucara ◽  
Abdulnaser Sayma
Keyword(s):  
Natural Gas ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Axial Compressor ◽  
Critical Parameters ◽  
Gas Combustion ◽  
Fuel Flexibility ◽  
Multistage Axial Compressor

Current gas turbine technology for power generation is generally optimised for natural gas. Recently the use of Low Calorific Value (LCV) fuels gained interest, particularly, Hydrogen rich syngas resulting from coal and solid waste gasification. When LCV fuels are used the performance and behaviour of the engines could significantly change and modifications may be needed. For instance, due to the relatively low heating value of the syngas, higher fuel mass flow rate is required compared to the natural gas combustion case. This leads to a decrease of demand for air from the compressor, which results in increased back pressure, reduction of stall margin and possible compressor instability. In a previous work an exploration of some compressor geometry modifications to allow for high fuel flexibility was conducted on a single axial compressor rotor. The investigation provided insights into the effect of blade shape modifications, such as stagger, lean and sweep on rotor performance. With the same purpose of identifying trends rather than producing optimum design, in this study the analysis is extended to a multistage axial compressor. Two different investigations have been performed, both having, as objective, the shifting of the original mass flow rate towards a lower value while maintaining high performance. In the first study the effect of IGV and stator vanes stagger variations only was considered while in a second approach the re-design of the original machine included modifies to rotor’s stagger angles. In order to understand the change in each single blade performance when modifying the original geometry, the variation of critical parameters such as blade loading and diffusion factor has been here considered in first analysis.

Aerodynamic Effects in a Transonic Compressor With Nonaxisymmetric Tip Clearance

2018 ◽  
Author(s):  
Maximilian Jüngst ◽  
Samuel Liedtke ◽  
Heinz Peter Schiffer ◽  
Bernd Becker
Keyword(s):  
Mass Flow ◽  
Current Knowledge ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Stability Margin ◽  
Tip Clearance ◽  
Stable Operation ◽  
Stall Inception ◽  
Transonic Compressor ◽  
Eccentric Rotor

Future axial compressor designs tend to be built with larger relative tip gaps and eccentricity, since the core engines are reduced in size. Our knowledge of the aerodynamic effects due to eccentric tip gaps is largely based on low-speed work. The aim of this study is to widen current knowledge by using the 1.5 stage Darmstadt Transonic Compressor, which is representative of the front stage of a high pressure compressor. Efficiency, peak pressure rise and stability margin of the compressor are reduced linearly at design speed when the tip clearance is increased from 0.9% to 2.5% tip chord length. This holds true for configurations with eccentric rotor tip gap, if their circumferentially averaged gaps are considered. For a compressor with 96% eccentricity and 1.7% average tip clearance, corrected mass flow at rotor exit varies locally with up to ±20% and ±10% at stator exit, which can result in inlet distortions for subsequent stages in a multi-stage configuration. Also, the redistribution of flow massively influences stall inception during throttling at constant speed. Propagating disturbances are damped in sectors with higher inlet mass flow and lower incidence. Thus, overall operation remains stable, even though some sectors are highly disturbed. Consequently, the maximum clearance of an eccentric stage is not limiting the stable operation of the whole stage.

scholarly journals Experimental and Numerical Investigation on Effects of the Steam Ingestion on the Aerodynamic Stability of an Axial Compressor

Entropy ◽  
2020 ◽  
Vol 22 (12) ◽  
pp. 1416
Author(s):  
Baofeng Tu ◽  
Xinyu Zhang ◽  
Jun Hu
Keyword(s):  
Boundary Layer ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Axial Flow ◽  
Stability Margin ◽  
Negative Influence ◽  
Suction Surface ◽  
Aerodynamic Stability ◽  
Stall Margin ◽  
Low Speed

In order to investigate the influence of steam ingestion on the aerodynamic stability of a two-stage low-speed axial-flow compressor, multiphase flow numerical simulation and experiment were carried out. The total pressure ratio and stall margin of the compressor was decreased under steam ingestion. When the compressor worked at 40% and 53% of the nominal speed, the stall margin decreased, respectively, by 1.5% and 6.3%. The ingested steam reduced the inlet Mach number and increased the thickness of the boundary layer on the suction surface of the blade. The low-speed region around the trailing edge of the blade was increased, and the flow separation region of the boundary layer on the suction surface of the blade was expanded; thus, the compressor was more likely to enter the stall state. The higher the rotational speed, the more significant the negative influence of steam ingestion on the compressor stall margin. The entropy and temperature of air were increased by steam. The heat transfer between steam and air was continuous in compressor passages. The entropy of the air in the later stage was higher than that in the first stage; consequently, the flow loss in the second stage was more serious. Under the combined action of steam ingestion and counter-rotating bulk swirl distortion, the compressor stability margin loss was more obvious. When the rotor speed was 40% and 53% of the nominal speed, the stall margin decreased by 6.3% and 12.64%, respectively.

Unsteady Numerical Research Into the Impact of Bleeding on Axial Compressor Performance

2010 ◽  
Author(s):  
Bin Zhao ◽  
Shaobin Li ◽  
Qiushi Li ◽  
Sheng Zhou
Keyword(s):  
Axial Compressor ◽  
Stability Margin ◽  
Moving Mesh ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Aero Engine ◽  
Compressor Performance ◽  
Numerical Research ◽  
Overall Performance ◽  
The Impact

The cooling gas of turbine components in aero-engine is extracted from the compressor. Its flow rate is related to the temperature before turbine. The percentage is usually about 3–5% and sometimes up to 25% of the main flow. Very few of the current studies in this field touched on the influence of air bleeding on compressor performance. This paper takes the single stage and low speed axial compressor as the research object, develops a time-accurate numerical method on the compressor overall performance by using the moving mesh to simulate the function of compressor throttle plug. Combined with experimental results, compressor flow field with and without air bleeding are compared and analyzed to study the impact of bleeding on compressor performance. The results show that if a bleeding design can ease the blockage generated by the tip leakage flow and the backflow near the trailing edge, the stall will be effectively postponed and the compressor stability margin will be expanded.

Influences of slotted blade on performance and flow structure of a transonic axial compressor

2021 ◽  
pp. 095765092199438
Author(s):  
Guochen Zhang ◽  
Tianyi Gao ◽  
Zhihui Xu ◽  
Pengcheng Liu ◽  
Chengfeng Zhang
Keyword(s):  
Flow Control ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Stability Margin ◽  
Future Research ◽  
Control Effect ◽  
Overall Stability ◽  
Transonic Axial Compressor

Main reason of compressor instability is boundary layer separation on the surface of blades. As one of flow control methods of the compressor, slotted blade has attracted many researchers’ attention because of its simple geometric structure and remarkable flow control effect. In order to evaluate its availability in the compressor, a type of convergent slot is designed to implement in a single-stage transonic axial compressor. Three configurations, i.e. rotor slot, stator slot and rotor-stator combined slot, are introduced to study the aerodynamic performance of compressor by numerical simulations. Furthermore, flow structures have been analyzed to explain the corresponding mechanism. The results show that overall stability margin of the compressor has been improved by flow control with slotted blade. Behavior of the rotor slot is better than that of the stator slot, but due to mass flow leakage in the slot, peak efficiency and chocking mass flow rate of the compressor are decreased by 1.18% and 3.8% respectively. The low momentum flow on pressure surface is sucked into the jet slot of stator blade, which improves the overall stability margin of 0.63%. The combined scheme with slotted rotor and slotted stator has obtained the best aerodynamic behavior with the increase of the overall stability margin of 2.83%. During the future research, main goal will be improvement of the compressor performance and extension of the mass flow rate range.

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