The Influence of Tip Clearance Momentum Flux on Stall Inception in a High-Speed Axial Compressor

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Joshua D. Cameron ◽  
Matthew A. Bennington ◽  
Mark H. Ross ◽  
Scott C. Morris ◽  
Juan Du ◽  
...  
Keyword(s):  
Momentum Flux ◽  
High Speed ◽  
Axial Compressor ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Axial Position ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage

Experimental and numerical studies were conducted to investigate tip-leakage flow and its relationship to stall in a transonic axial compressor. The computational fluid dynamics (CFD) results were used to identify the existence of an interface between the approach flow and the tip-leakage flow. The experiments used a surface-streaking visualization method to identify the time-averaged location of this interface as a line of zero axial shear stress at the casing. The axial position of this line, denoted xzs, moved upstream with decreasing flow coefficient in both the experiments and computations. The line was consistently located at the rotor leading edge plane at the stalling flow coefficient, regardless of inflow boundary condition. These results were successfully modeled using a control volume approach that balanced the reverse axial momentum flux of the tip-leakage flow with the momentum flux of the approach fluid. Nonuniform tip clearance measurements demonstrated that movement of the interface upstream of the rotor leading edge plane leads to the generation of short length scale rotating disturbances. Therefore, stall was interpreted as a critical point in the momentum flux balance of the approach flow and the reverse axial momentum flux of the tip-leakage flow.

scholarly journals Effects of Tip Leakage Flow on the Aerodynamic Performance and Stability of an Axial-Flow Transonic Compressor Stage

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4168
Author(s):  
Botao Zhang ◽  
Xiaochen Mao ◽  
Xiaoxiong Wu ◽  
Bo Liu
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Axial Flow ◽  
Leading Edge ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Transonic Compressor

To explain the effect of tip leakage flow on the performance of an axial-flow transonic compressor, the compressors with different rotor tip clearances were studied numerically. The results show that as the rotor tip clearance increases, the leakage flow intensity is increased, the shock wave position is moved backward, and the interaction between the tip leakage vortex and shock wave is intensified, while that between the boundary layer and shock wave is weakened. Most of all, the stall mechanisms of the compressors with varying rotor tip clearances are different. The clearance leakage flow is the main cause of the rotating stall under large rotor tip clearance. However, the stall form for the compressor with half of the designed tip clearance is caused by the joint action of the rotor tip stall caused by the leakage flow spillage at the blade leading edge and the whole blade span stall caused by the separation of the boundary layer of the rotor and the stator passage. Within the investigated varied range, when the rotor tip clearance size is half of the design, the compressor performance is improved best, and the peak efficiency and stall margin are increased by 0.2% and 3.5%, respectively.

A Proposal for Passive Wall Treatment Applied in High Performance Axial Flow Compressors

2020 ◽  
Author(s):  
Rubén Bruno Díaz ◽  
Jesuino Takachi Tomita ◽  
Cleverson Bringhenti ◽  
Francisco Carlos Elizio de Paula ◽  
Luiz Henrique Lindquist Whitacker
Keyword(s):  
Stokes Equations ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Smooth Wall ◽  
Tip Leakage Flow ◽  
Viscous Effects ◽  
Stall Margin ◽  
Tip Leakage

Abstract Numerical simulations were carried out with the purpose of investigating the effect of applying circumferential grooves at axial compressor casing passive wall treatment to enhance the stall margin and change the tip leakage flow. The tip leakage flow is pointed out as one of the main contributors to stall inception in axial compressors. Hence, it is of major importance to treat appropriately the flow in this region. Circumferential grooves have shown a good performance in enhancing the stall margin in previous researches by changing the flow path in the tip clearance region. In this work, a passive wall treatment with four circumferential grooves was applied in the transonic axial compressor NASA Rotor 37. Its effect on the axial compressor performance and the flow in the tip clearance region was analyzed and set against the results attained for the smooth wall case. A 2.63% increase in the operational range of the axial compressor running at 100%N, was achieved, when compared with the original smooth wall casing configuration. The grooves installed at compressor casing, causes an increase in the flow entropy generation due to the high viscous effects in this gap region, between the rotor tip surface and casing with grooves. These viscous effects cause a drop in the turbomachine efficiency. For the grooves configurations used in this work, an efficiency drop of 0.7% was observed, compared with the original smooth wall. All the simulations were performed based on 3D turbulent flow calculations using Reynolds Averaged Navier-Stokes equations, and the flow eddy viscosity was determined using the two-equation SST turbulence model. The details of the grooves geometrical dimensions and its implementation are described in the paper.

Contributions of Tip Leakage and Inlet Diffusion on Inducer Backflow

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
D. Tate Fanning ◽  
Steven E. Gorrell ◽  
Daniel Maynes ◽  
Kerry Oliphant
Keyword(s):  
Leading Edge ◽  
Tip Clearance ◽  
Tip Vortex ◽  
Low Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Flow Recirculation ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Inducers are used as a first stage in pumps to minimize cavitation and allow the pump to operate at lower inlet head conditions. Inlet flow recirculation or backflow in the inducer occurs at low flow conditions and can lead to instabilities and cavitation-induced head breakdown. Backflow of an inducer with a tip clearance (TC) of τ = 0.32% and with no tip clearance (NTC) is examined with a series of computational fluid dynamics simulations. Removing the TC eliminates tip leakage flow; however, backflow is still observed. In fact, the NTC case showed a 37% increase in the length of the upstream backflow penetration. Tip leakage flow does instigate a smaller secondary leading edge tip vortex that is separate from the much larger backflow structure. A comprehensive analysis of these simulations suggests that blade inlet diffusion, not tip leakage flow, is the fundamental mechanism leading to the formation of backflow.

Stall Inception and Development Process Due to Tip Leakage Flow in Axial Compressor Rotor Blades Row

2014 ◽  
Vol 30 (3) ◽  
pp. 307-313 ◽  
Author(s):  
R. Taghavi-Zenou ◽  
S. Abbasi ◽  
S. Eslami
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Leading Edge ◽  
Rotor Blades ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Compressor Rotor

ABSTRACTThis paper deals with tip leakage flow structure in subsonic axial compressor rotor blades row under different operating conditions. Analyses are based on flow simulation utilizing computational fluid dynamic technique. Three different circumstances at near stall condition are considered in this respect. Tip leakage flow frequency spectrum was studied through surveying instantaneous static pressure signals imposed on blades surfaces. Results at the highest flow rate, close to the stall condition, showed that the tip vortex flow fluctuates with a frequency close to the blade passing frequency. In addition, pressure signals remained unchanged with time. Moreover, equal pressure fluctuations at different passages guaranteed no peripheral disturbances. Tip leakage flow frequency decreased with reduction of the mass flow rate and its structure was changing with time. Spillage of the tip leakage flow from the blade leading edge occurred without any backflow in the trailing edge region. Consequently, various flow structures were observed within every passage between two adjacent blades. Further decrease in the mass flow rate provided conditions where the spilled flow ahead of the blade leading edge together with trailing edge backflow caused spike stall to occur. This latter phenomenon was accompanied by lower frequencies and higher amplitudes of the pressure signals. Further revolution of the rotor blade row caused the spike stall to eventuate to larger stall cells, which may be led to fully developed rotating stall.

scholarly journals On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Hongmei Jiang ◽  
Li He ◽  
Qiang Zhang ◽  
Lipo Wang
Keyword(s):  
High Speed ◽  
Turbine Blades ◽  
Flow Distribution ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Scaling Method ◽  
Low Speed ◽  
Tip Leakage ◽  
Speed Condition

Modern high-pressure turbine blades operate at high-speed conditions. The over-tip-leakage (OTL) flow can be high-subsonic or even transonic. From the consideration of problem simplification and cost reduction, the OTL flow has been studied extensively in low-speed experiments. It has been assumed a redesigned low-speed blade profile with a matched blade loading should be sufficient to scale the high-speed OTL flow down to the low-speed condition. In this paper, the validity of this conventional scaling approach is computationally examined. The computational fluid dynamics (CFD) methodology was first validated by experimental data conducted in both high- and low-speed conditions. Detailed analyses on the OTL flows at high- and low-speed conditions indicate that, only matching the loading distribution with a redesigned blade cannot ensure the match of the aerodynamic performance at the low-speed condition with that at the high-speed condition. Specifically, the discrepancy in the peak tip leakage mass flux can be as high as 22%, and the total pressure loss at the low-speed condition is 6% higher than the high-speed case. An improved scaling method is proposed hereof. As an additional dimension variable, the tip clearance can also be “scaled” down from the high-speed to low-speed case to match the cross-tip pressure gradient between pressure and suction surfaces. The similarity in terms of the overall aerodynamic loss and local leakage flow distribution can be improved by adjusting the tip clearance, either uniformly or locally.

Numerical investigations on tip leakage flow characteristics and vortex trajectory prediction model in centrifugal compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 757-772 ◽  
Author(s):  
Huijing Zhao ◽  
Zhiheng Wang ◽  
Shubo Ye ◽  
Guang Xi
Keyword(s):  
Prediction Model ◽  
Flow Instability ◽  
Leading Edge ◽  
Tip Clearance ◽  
Centrifugal Impeller ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Blade Tip

To better understand the characteristics of tip leakage flow and interpret the correlation between flow instability and tip leakage flow, the flow in the tip region of a centrifugal impeller is investigated by using the Reynolds averaged Navier–Stokes solver technique. With the decrease of mass flow rate, both the tip leakage vortex trajectory and the mainflow/tip leakage flow interface are shifted towards upstream. The mainflow/tip leakage flow interface finally reaches the leading edge of main blade at the near-stall condition. A prediction model is proposed to track the tip leakage vortex trajectory. The blade loading at blade tip and the averaged streamwise velocity of main flow within tip clearance height are adopted to determine the tip leakage vortex trajectory in the proposed model. The coefficient k in Chen’s model is found to be not a constant. Actually, it is correlated with h/b (the ratio of blade tip clearance height to blade tip thickness), because h/b will significantly influence the flow structure across the tip clearance. The effectiveness of the proposed prediction model is further demonstrated by tracking the tip leakage vortex trajectories in another three centrifugal impellers characterized with different h/b (s).

Effects of tip clearance size on the unsteady flow behaviors and performance in a counter-rotating axial flow compressor

2017 ◽  
Vol 233 (3) ◽  
pp. 1059-1070 ◽  
Author(s):  
Xiaochen Mao ◽  
Bo Liu ◽  
Hang Zhao
Keyword(s):  
Unsteady Flow ◽  
Incidence Angle ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Axial Flow Compressor ◽  
Flow Compressor

This paper presents the studies performed to better understand the effects of increased tip clearance size on the unsteady flow behaviors and overall performance under the rotor–rotor interaction environment in a counter-rotating axial flow compressor. The investigation method is based on the three-dimensional unsteady Reynolds-averaged Navier–Stokes simulations. The results show that the intensified tip leakage flow in front rotor (R1) caused by the increased tip clearance size will lead to the growth of incoming incidence angle near the tip of the rear rotor (R2). The increasing of double leakage flow range plays a significant role in the sensitivity of the efficiency to tip clearance size and its extent is enlarged gradually with the increase of tip clearance size. As the tip clearance size is increased to 1.5τ (τ represents the designed tip clearance size) from 0.5τ, the results of the fast Fourier transform for the static pressure near blade tip show that two other new fluctuating frequency components appear due to the happening of tip leakage flow self-unsteadiness in R1 and R2, respectively. Additionally, the fluctuating strength near the tip in R2 is significantly increased. However, both the overall fluctuation in R1 caused by the potential effect from downstream and the oscillation in the hub corner on the pressure side of R2 are decreased obviously. The relative inflow angle tends to increase when the incoming wakes and tip leakage flow from R1 encounter the blade leading edge of R2, which leads to the result that the trajectory of tip leakage flow is shifted more upstream.

Nonaxisymmetric Study of Tip Leakage Flow in a Centrifugal Compressor With a Volute During Stall Process

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Ce Yang ◽  
Botai Su ◽  
Li Fu ◽  
Hang Zhang
Keyword(s):  
Centrifugal Compressor ◽  
Static Pressure ◽  
Leading Edge ◽  
Work Capacity ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
High Static Pressure ◽  
Circumferential Nonuniformity

Abstract Tip leakage flow (TLF) patterns, which affect compressor performance, are closely related to compressor stability. To date, minimal attention has been given to circumferential nonuniformity of the TLF in a centrifugal compressor with a nonaxisymmetric volute structure. In this study, the circumferential difference of the TLF in a centrifugal compressor with a volute during the stall process is analyzed. The circumferential nonuniformity of tip leakage vortex (TLV) trajectories, loading distribution near the tip, and distance between the TLV core and the leading edge (LE) of splitter blades were also investigated. It is shown that in the circumferential direction, there are two peaks associated with the angle (α) between the TLV trajectory of the seven main blades and the axial direction. As the stall process progresses, the blade whose LE is affected by the high static pressure band (PP) induced by the volute tongue (VT) loses its work capacity first and the α difference between this blade and the other blades increases. In addition, the tip loading and TLF velocity of the blade whose LE is affected by the high static pressure band induced by the VT are at a minimum, and the flow loss in the tip clearance is higher. There is a phenomenon of the TLV breakdown. When the blade trailing edge (TE) is located in the low static pressure region, TLV streamlines appear as a significant turn at the breakdown point. However, the TLV streamlines at other circumferential positions do not exhibit this phenomenon.

scholarly journals On Scaling Method to Investigate High-Speed Over-Tip-Leakage Flow at Low-Speed Condition

2017 ◽  
Author(s):  
Hongmei Jiang ◽  
Li He ◽  
Qiang Zhang ◽  
Lipo Wang
Keyword(s):  
High Speed ◽  
Flow Distribution ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Scaling Method ◽  
Low Speed ◽  
Aerodynamic Loss ◽  
Tip Leakage ◽  
Speed Condition

Modern High Pressure Turbine (HPT) blades operate at high speed conditions. The Over-Tip-Leakage (OTL) flow, which plays a major role in the overall loss generation for HPT, can be high-subsonic or even transonic. In practice from the consideration of problem simplification and cost reduction, the OTL flow has been studied extensively in low speed experiments. It has been assumed a redesigned low speed blade profile with a matched blade loading should be sufficient to scale the high speed OTL flow down to the low speed condition. In this paper, the validity of this conventional scaling approach is computationally examined. The CFD methodology was firstly validated by experimental data conducted in both high and low speed conditions. Detailed analyses on the OTL flows at high and low speed conditions indicate that, only matching the loading distribution with a redesigned blade cannot ensure the match of the aerodynamic performance at the low speed condition with that at the high-speed condition. Specifically, the discrepancy in the peak tip leakage mass flux can be as high as 22.2%, and the total pressure loss at the low speed condition is 10.7% higher than the high speed case. An improved scaling method is proposed hereof. As an additional dimension variable, the tip clearance can also be “scaled” down from the high speed to low speed case to match the cross-tip pressure gradient between pressure and suction surfaces. The similarity in terms of the overall aerodynamic loss and local leakage flow distribution can be improved by adjusting the tip clearance, either uniformly or locally. The limitations of this proposed method are also addressed in this paper.

An Experimental and Computational Investigation of Tip Clearance Flow and Its Impact on Stall Inception

2010 ◽  
Author(s):  
Matthew A. Bennington ◽  
Mark H. Ross ◽  
Joshua D. Cameron ◽  
Scott C. Morris ◽  
Juan Du ◽  
...  
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Momentum Balance ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Clearance Flow

A numerical and experimental study was conducted to investigate the tip clearance flow and its relationship to stall in a transonic axial compressor. The CFD results were used to identify the existence of an interface between incoming axial flow and the reverse tip clearance flow. A surface streaking method was used to experimentally identify this interface as a line of zero axial shear stress at the casing. The position of this line, denoted xzs, moved upstream with decreasing flow coefficient in both the experiments and computations. The line was found to be at the rotor leading edge plane when the compressor stalled. Further measurements using rotor offset and inlet distortion further corroborated these results, and demonstrated that the movement of the interface upstream of the leading edge leads to the generation of rotating (“spike”) disturbances. Stall was therefore interpreted to occur as a result of a critical momentum balance between the approach fluid and the tip-leakage flow.

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