IMPACT OF EXIT DUCT DYNAMIC RESPONSE ON COMPRESSOR STABILITY

2020 ◽  
pp. 1-11
Author(s):  
Wenqiang Zhang ◽  
Mehdi Vahdati ◽  
Fanzhou Zhao
Keyword(s):  
Dynamic Response ◽  
Model Simulation ◽  
Stability Margin ◽  
Quantitative Relationship ◽  
Aerodynamic Stability ◽  
Stall Margin ◽  
Acoustic Reflection ◽  
Exit Nozzle ◽  
Fan Blade ◽  
The Stability

Abstract Abrupt distortions can appear as a result of transient crosswind or during rapid aircraft maneuvers. Such distortions can reduce the aerodynamic stability of engines and therefore present a major concern to all aero-engine manufacturers. To assess the aerodynamic stability of fan blades due to distortions, rig tests are usually carried out to establish the loss in stall margin. In such test campaigns, an exit duct followed by a nozzle is placed downstream of the fan blade and the operating condition of the fan is controlled by this nozzle. It is shown in this paper that in such rig tests the length of duct downstream of a fan has a significant impact on fan stall margin. The key contributor for such interaction is the dynamic response of the exit duct and the aerodynamic stability of the fan is affected by the acoustic reflection from the exit nozzle. To study the underlying physics, transient response in the exit duct downstream of a transonic fan stage was studied numerically using a simplified model. Simulation results, along with calculations based on analytical theories, confirmed the generation, propagation and reflection of waves induced by the inlet distortion. A quantitative relationship concerning the lengths of the compression system is introduced which determines whether a duct setup would have beneficial or detrimental influences on compressor aerodynamic stability. The findings of this research have great implications for the stability assessment of fans as the stability margin can be affected by the waves generated in bypass ducts.

Impact of Exit Duct Dynamic Response on Compressor Stability

2019 ◽  
Author(s):  
Wenqiang Zhang ◽  
Mehdi Vahdati ◽  
Fanzhou Zhao
Keyword(s):  
Dynamic Response ◽  
Model Simulation ◽  
Stability Margin ◽  
Quantitative Relationship ◽  
Aerodynamic Stability ◽  
Stall Margin ◽  
Acoustic Reflection ◽  
Exit Nozzle ◽  
Fan Blade ◽  
The Stability

Abstract Abrupt distortions can appear as a result of transient crosswind or during rapid aircraft maneuvers. Such distortions are known to reduce the aerodynamic stability of engines and therefore present a major concern to all aero-engine manufacturers. To assess the aerodynamic stability of fan blades due to distortions, rig tests are usually carried out to establish the loss in stall margin. In such test campaigns, an exit duct (which is followed by a nozzle) is placed downstream of the fan blade and the operating condition of the fan is controlled by this nozzle. It is shown in this paper that in such rig tests the length of duct downstream of a fan has a significant impact on fan stall margin. The key contributor for such interaction is the dynamic response of the exit duct and the aerodynamic stability of the fan is affected by the acoustic reflection from the exit nozzle. To study the underlying physics, transient response in the exit duct downstream of a transonic fan stage was studied numerically using a simplified model. Simulation results, along with calculations based on analytical theories, confirmed the generation, propagation and reflection of waves induced by the inlet distortion. A quantitative relationship concerning the lengths of the compression system is introduced which determines whether a duct setup would have beneficial or detrimental influences on compressor aerodynamic stability. The findings of this research have great implications for the stability assessment of fans as the stability margin can be affected by the waves generated in bypass ducts.

A Parametric Study of the Effects of Inlet Distortion on Fan Aerodynamic Stability

2018 ◽  
Author(s):  
Wenqiang Zhang ◽  
Mehdi Vahdati
Keyword(s):  
Boundary Layer ◽  
Measured Data ◽  
Rotating Stall ◽  
Aerodynamic Stability ◽  
Stall Margin ◽  
Turbofan Engines ◽  
Inlet Distortion ◽  
Recent Trends ◽  
Fan Blade ◽  
The Stability

The performance and aerodynamic stability of fan blades operating in a circumferentially non-uniform inlet flow is a key concern in the design of turbofan engines. With the recent trends in the design of civil engines with shorter inlet ducts (such as low-speed fans), or boundary layer ingesting engines, quick and reliable modelling of rotor/distortion interactions is becoming very important. The aim of this paper is to study the effects of inlet distortions on the aerodynamic stability of a fan blade and to identify the parameters that have a major impact on the stability of the blade. NASA rotor 67, for which a significant amount of measured data is available, was used for this study. In the first part of this study, the behavior of the fan with inlet distortion at near stall condition is analyzed, and it is shown how rotating stall is triggered. In the second part of this study, unsteady simulations with inlet distortion were performed to study how parameters, such as exit duct length and distortion strength, influence the stall margin of the blade.

A Parametric Study of the Effects of Inlet Distortion on Fan Aerodynamic Stability

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Wenqiang Zhang ◽  
Mehdi Vahdati
Keyword(s):  
Boundary Layer ◽  
Measured Data ◽  
Rotating Stall ◽  
Aerodynamic Stability ◽  
Stall Margin ◽  
Turbofan Engines ◽  
Inlet Distortion ◽  
Recent Trends ◽  
Fan Blade ◽  
The Stability

The performance and aerodynamic stability of fan blades operating in a circumferentially nonuniform inlet flow is a key concern in the design of turbofan engines. With the recent trends in the design of civil engines with shorter inlet ducts (such as low-speed fans), or boundary layer ingesting engines, quick and reliable modeling of rotor/distortion interactions is becoming very important. The aim of this paper is to study the effects of inlet distortions on the aerodynamic stability of a fan blade and to identify the parameters that have a major impact on the stability of the blade. NASA rotor 67, for which a significant amount of measured data is available, was used for this study. In the first part of this study, the behavior of the fan with inlet distortion at near stall (NS) condition is analyzed, and it is shown how rotating stall is triggered. In the second part of this study, unsteady simulations with inlet distortion were performed to study how exit duct length influences the stall margin of the blade.

Effects of tip air injection on the aerodynamic stability of an axial flow compressor with total pressure distortion

2021 ◽  
pp. 095441002110375
Author(s):  
Baofeng Tu ◽  
Xinyu Zhang ◽  
Liang Li ◽  
Jun Hu
Keyword(s):  
Total Pressure ◽  
Critical Role ◽  
Axial Flow ◽  
Air Injection ◽  
Aerodynamic Stability ◽  
Insertion Depth ◽  
Stall Margin ◽  
Low Speed ◽  
Inlet Distortion ◽  
The Stability

The compressor is a critical component that determines the aerodynamic stability of an aero-engine. Total pressure inlet distortion decreases the thrust and shrinks the stability margin, thus inducing severe performance degradation or even flameout. Generally, tip air injection is used to reduce the adverse influence of total pressure inlet distortion on the aerodynamic stability. In the present work, an experimental investigation on the effects of tip air injection on the stability of a two-stage low-speed axial compressor with total pressure inlet distortion was carried out. A flat baffle generated the total pressure distortion at the inlet of the compressor. The stall margin of the compressor was reduced significantly by the total pressure distortion. When the dimensionless insertion depth of the flat baffle was 0.45, the stall margin decreased to 11.4%. Under the total pressure inlet distortion, tip air injection effectively improved the distortion resistance capability of the compressor. The circumferential layout of the nozzle played a critical role in the stability expansion effect of tip air injection under the inlet flow condition of the total pressure distortion. The modal wave disturbance was likely to occur in the distortion-affected region (the low-pressure region and the mixing region). Tip air injection did not inhibit the generation of the modal wave but restrained the development of the modal wave into the stall cell. It improved the low-speed compressor’s tolerance to the modal wave and allowed a higher amplitude modal wave to occur.

An Experimental Investigation Into the Impacts of Varying the Circumferential Extent of Tip-Low Total Pressure Distortion on Fan Stability

2021 ◽  
Author(s):  
Oliver Allen ◽  
Alejandro Castillo Pardo ◽  
Cesare A. Hall
Keyword(s):  
Total Pressure ◽  
Stability Margin ◽  
Jet Engines ◽  
Stall Inception ◽  
Stall Margin ◽  
High Incidence ◽  
Circumferential Extent ◽  
Low Distortion ◽  
The Stability ◽  
The Impact

Abstract Future jet engines with shorter and thinner intakes present a greater risk of intake separation. This leads to a complex tip-low total pressure distortion pattern of varying circumferential extent. In this paper, an experimental study has been completed to determine the impact of such distortion patterns on the operating range and stalling behaviour of a low-speed fan rig. Unsteady casing static pressure measurements have been made during stall events in 11 circumferential extents of tip-low distortion. The performance has been measured and detailed area traverses have been performed at rotor inlet and outlet in 3 of these cases — clean, axisymmetric tip-low and half-annulus tip-low distortion. Axisymmetric tip-low distortion is found to reduce stall margin by 8%. It does not change the stalling mechanism compared to clean inflow. In both cases, high incidence at the tip combined with growth of the casing boundary layer drive instability. In contrast, half-annulus tip-low distortion is found to reduce stall margin by only 4% through a different mechanism. The distortion causes disturbances in the measured casing pressure signals to grow circumferentially in regions of high incidence. Stall occurs when these disturbances do not decay fully in the undistorted region. As the extent of the distorted sector is increased, the stability margin is found to reduce continuously. However, the maximum disturbance size before stall inception is found to occur at intermediate values of distorted sector extent. This corresponds to distortion patterns that provide sufficient circumferential length of undistorted region for disturbances to decay fully before they return to the distorted sector. It is found that as the extent of the tip-low distortion sector is increased, the circumferential size of the stall cell that develops is reduced. However, its speed is found to remain approximately constant at 50% of the rotor blade speed.

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.

scholarly journals Numerical Investigation on a Axial Slot Casing Treatment of a Large Circumferential Interval and Small Opening Area

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6181
Author(s):  
Zepeng Liu ◽  
Guoping Huang ◽  
Omer Musa
Keyword(s):  
Stability Margin ◽  
Field Analysis ◽  
Stall Margin ◽  
Small Opening ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Flow Field Analysis ◽  
The Stability ◽  
Slot Structure ◽  
Excessive Number

Axial slot casing treatment is a common method to extend the stall margin of a compressor. Based on the mechanism of unsteady flow control, this paper redesigns axial slots with large circumferential interval and small opening area. To test the effect of this axial slot structure, unsteady numerical simulations were carried out with different slot areas and circumferential intervals. The results show that this novel axial slot casing treatment can significantly improve compressor stall margin. Meanwhile, compared with the traditional axial slot, the efficiency loss is greatly reduced. The flow field analysis shows that the new axial slot structure proposed in this paper can suppress the development of tip leakage vortex and unsteadiness in the tip region at the near stall condition through decreasing the tip loading periodically. Moreover, we find that the slot area is proportional to the improvement of stability margin. Under the same slot area, an excessive number of slots is not conducive to the improvement of the stability margin.

The effect of high temperature steam ingestion on aerodynamic performance and stability of a low-speed axial compressor

2019 ◽  
Vol 234 (3) ◽  
pp. 871-886
Author(s):  
Baofeng Tu ◽  
Luyao Zhang ◽  
Wenjun Fu ◽  
Jun Hu
Keyword(s):  
High Temperature ◽  
Mass Fraction ◽  
Axial Compressor ◽  
Stability Margin ◽  
Aerodynamic Stability ◽  
Two Stage ◽  
Low Speed ◽  
High Temperature Steam ◽  
The Stability ◽  
The Impact

To investigate the effect of high temperature steam ingestion on the aerodynamic stability of a multistage axial compressor, a two-stage low-speed axial compressor was studied, and full-annulus steady-state and unsteady-state numerical simulations were carried out. The effect of the high temperature steam mass fraction and the distribution of steam at the inlet boundary on the aerodynamic stability of a two-stage low-speed axial compressor was investigated. From the simulation results, we found that high temperature steam ingestion has an adverse effect on the low-speed axial compressor. The larger the steam mass fraction is, the greater the impact of the steam ingestion on the stability boundary and stall margin will be. When the steam mass fraction is equal to 0.35 and 0.7%, the stability margin decreases from 36.07 to 29.72% and 28.05%, respectively. The distribution of steam at the inlet boundary will change the performance and stability. When the steam ingestion range is less than 90°, the steam ingestion area increases and the stability margin will decrease gradually. After 90°, the stability margin is almost unchanged. The difference between the calculated and experimental values of the stability margin reduction caused by steam ingestion is 0.87%. In addition, with the ingestion of high temperature steam, the blockage in the corresponding passages is intensified and the loss is increased, which leads to the occurrence of the stall in advance. It is evident that steam ingestion has a significant impact on compressor stability, ensuring that the steam mass fraction and steam ingestion range are close to the actual value.

scholarly journals Stability-Guaranteed and High Terrain Adaptability Static Gait for Quadruped Robots

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4911
Author(s):  
Qian Hao ◽  
Zhaoba Wang ◽  
Junzheng Wang ◽  
Guangrong Chen
Keyword(s):  
Impedance Control ◽  
Stability Margin ◽  
Planning Method ◽  
Legged Robots ◽  
Gait Planning ◽  
Quadruped Locomotion ◽  
Quadruped Robots ◽  
Adjustment Strategy ◽  
Compliant Behavior ◽  
The Stability

Stability is a prerequisite for legged robots to execute tasks and traverse rough terrains. To guarantee the stability of quadruped locomotion and improve the terrain adaptability of quadruped robots, a stability-guaranteed and high terrain adaptability static gait for quadruped robots is addressed. Firstly, three chosen stability-guaranteed static gaits: intermittent gait 1&2 and coordinated gait are investigated. In addition, then the static gait: intermittent gait 1, which is with the biggest stability margin, is chosen to do a further research about quadruped robots walking on rough terrains. Secondly, a position/force based impedance control is employed to achieve a compliant behavior of quadruped robots on rough terrains. Thirdly, an exploratory gait planning method on uneven terrains with touch sensing and an attitude-position adjustment strategy with terrain estimation are proposed to improve the terrain adaptability of quadruped robots. Finally, the proposed methods are validated by simulations.

Study on the characteristics of secondary arc current of UHV high compensation degree TCSC line under the fine-tuning mode

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Baina He ◽  
Yadi Xie ◽  
Jingru Zhang ◽  
Nirmal-Kumar C. Nair ◽  
Xingmin He ◽  
...  
Keyword(s):  
Transmission Line ◽  
Transmission Lines ◽  
Stability Margin ◽  
Transmission Capacity ◽  
Fine Tuning ◽  
Series Compensation ◽  
Arc Current ◽  
Compensation Device ◽  
The Stability ◽  
Recovery Voltage

Abstract In the transmission line, the series compensation device is often used to improve the transmission capacity. However, when the fixed series capacitor (FSC) is used in high compensation series compensation device, the stability margin cannot meet the requirements. Therefore, thyristor controlled series compensator (TCSC) is often installed in transmission lines to improve the transmission capacity of the line and the stability of the system. For cost considerations, the hybrid compensation mode of FSC and TCSC is often adopted. However, when a single-phase grounding fault occurs in a transmission line with increased series compensation degree, the unreasonable distribution of FSC and TCSC will lead to the excessive amplitude of secondary arc current, which is not conducive to rapid arc extinguishing. To solve this problem, this paper is based on 1000 kV Changzhi-Nanyang-Jingmen UHV series compensation transmission system, using PSCAD simulation program to established UHV series compensation simulation model, The variation law of secondary arc current and recovery voltage during operation in fine tuning mode after adding TCSC to UHV transmission line is analyzed, and the effect of increasing series compensation degree on secondary arc current and recovery voltage characteristics is studied. And analyze the secondary arc current and recovery voltage when using different FSC and TCSC series compensation degree schemes, and get the most reasonable series compensation configuration scheme. The results show that TCSC compensation is more beneficial to arc extinguishing under the same series compensation. Compared with several series compensation schemes, it is found that with the increase of the proportion of TCSC, the amplitude of secondary arc current and recovery voltage vary greatly. Considering various factors, the scheme that is more conducive to accelerating arc extinguishing is chosen.

Sign in / Sign up

Export Citation Format

Share Document