scholarly journals Control and Entropy Analysis of Tip Leakage Flow for Compressor Cascade under Different Clearance Sizes with Endwall Suction

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 128
Author(s):  
Botao Zhang ◽  
Bo Liu ◽  
Changfu Han ◽  
Hang Zhao
Keyword(s):  
Flow Rate ◽  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Control Effect ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
The Difference ◽  
Suction Flow

To investigate the influence of the change of tip clearance size on the control effect of the endwall suction, the effects of endwall suction on the aerodynamic performance of the axial compressor cascade were studied numerically. Three tip clearance sizes of 0.5% h, 1.0% h, and 2.0% h (h is the blade height) were mainly considered. The results show that the endwall suction scheme whose coverage range was 8–33% axial chord can reduce the leakage flow and improve the aerodynamic performance by directly influencing the structure of tip leakage vortex. The overall total pressure loss coefficients of the three clearance size schemes at 0° angle of incidence with 0.4 inlet Mach number are reduced by about 10.3%, 10.8%, and 6.0%, respectively, at the suction flow rate of 0.7%. Under the same suction flow rate, the onset position of the tip leakage vortex of the cascade with small clearance is shifted from the 15% of the axial chord length of original to the 48% of the axial chord length, which with large clearance is nearly no changed. The leakage flow rate and the distance from the leakage vortex to the suction slot are the main reasons for the different control effect of the endwall suction under different tip clearance sizes. The difference of the spanwise distribution of flow field parameters may also cause the difference of flow control effect.

Effect of endwall suction on aerodynamic performance of compressor cascade with tip clearance at a large incidence angle

2021 ◽  
pp. 095765092098395
Author(s):  
Botao Zhang ◽  
Bo Liu ◽  
Hejian Wang ◽  
Xiaochen Mao
Keyword(s):  
Boundary Layer ◽  
Incidence Angle ◽  
Boundary Layer Separation ◽  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Control Effect ◽  
Tip Leakage

In order to deeply analyze the application prospect of the boundary layer suction technique on the compressor, the flow control effect of endwall suction scheme on the tip leakage flow of a compressor cascade at a large incidence angle with complex internal flow structure and different loss proportion from the case at design incidence angle, was studied numerically, as well as on the overall aerodynamic performance. The results show that the suction scheme directly affects the structure of the tip leakage flow and makes the onset position of the tip leakage vortex move backward, which weakens the intensity and influence range of the tip leakage flow, thus improving the cascade performance in the tip region. At the large incidence angle, large flow suction makes the boundary layer separation in the low span area advance, and the corner separation region at the gap-free end expands to the upper. The position of the separation vortex shedding rises from 10% blade span under the condition without suction to about 70% blade span under the condition with the suction flow rate of 0.7%, and the separation loss increases. The overall performance of the cascade at the large incidence angle mainly depends on the increase of separation loss, while the effect of the decrease of leakage loss on it is greatly reduced. With suction, the total pressure loss coefficient of the cascade increases by about 5.7% at the incidence angle of +8°.

scholarly journals Effect of casing aspiration on the tip leakage flow in the axial flow compressor cascade

2017 ◽  
Vol 232 (3) ◽  
pp. 225-239 ◽  
Author(s):  
Xiaochen Mao ◽  
Bo Liu ◽  
Tianquan Tang
Keyword(s):  
Leakage Flow ◽  
Control Mechanisms ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Control Effect ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Onset Point ◽  
Starting Point ◽  
The Impact

Tip leakage flow is usually responsible for the deterioration of compressor performance and stability. The current paper conducts numerical simulations on the impact of casing aspiration on the axial compressor cascade performance. Three aspiration schemes with different chordwise coverage are studied and analyzed. It is found that the cascade performance can be effectively improved by the appropriate casing aspiration, and the optimum aspiration scheme should cover the area including the onset point of tip leakage vortex and its vicinity. The control mechanisms are different for the aspiration schemes located at different blade chord ranges. For the aspiration scheme covering the onset point of tip leakage vortex, the improvement of the cascade performance is mainly due to that the starting point of the tip leakage vortex is shifted downstream. The original tip leakage vortex structure is divided into two parts if the aspiration scheme is located behind the onset point of tip leakage vortex and the final control effect is the combination of the influence from the two different parts of tip leakage vortex. Additionally, the casing aspiration redistributes the blade loading along the chord near blade tip. The results of these investigations may offer guidance for the appropriate design of aspiration scheme in the future updated compressors and the overall total pressure loss coefficient caused by aspiration slot should be considered in the design process.

Characteristics of Tip-Clearance Flows of a Compressor Cascade and a Propulsion Pump

1997 ◽  
Author(s):  
Y. T. Lee ◽  
M. J. Laurita ◽  
J. Feng ◽  
C. L. Merkle
Keyword(s):  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Blade Passage ◽  
Tip Leakage ◽  
Pump Rotor ◽  
Leakage Flows ◽  
Tip Leakage Flows

Tip-leakage flows for a linear compressor cascade and a one-stage shrouded pump rotor are discussed in this paper. A numerical method solving the Reynolds averaged Navier Stokes equations is used to explore various detail features of the tip-leakage flows. Calculation results for the cascade provide an assessment for predicting flow past a non-rotating blade passage with zero and 2% chord clearances. On the other hand, the pump rotor configuration provides a swirling passage flow with the complication of a trailing-edge separation vortex mixed with the tip-clearance and passage vortices and produces a very complex three-dimensional flow in the rotor wake. The physical aspects of the tip-clearance flows are discussed including suction-side reloading and pressure-side unloading due to a tip clearance and formation and transportation of the tip-leakage vortex. Detailed velocity comparisons in the blade passage and the tip gap region are shown to indicate the difficulty of predicting tip-leakage flow. The pressure at the core of the tip vortex is also examined to evaluate the strength of the tip-leakage vortex. Some computational guidelines for design usage are provided for these tip-leakage flow calculations.

Experiment study of the winglet-cavity tip on the aerodynamic performance in a turbine cascade

2017 ◽  
Vol 231 (7) ◽  
pp. 676-685 ◽  
Author(s):  
Shaowen Chen ◽  
Zhihua Zhou ◽  
Qinghe Meng ◽  
Songtao Wang ◽  
Xun Zhou
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Static Pressure ◽  
Aerodynamic Performance ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Passage Vortex ◽  
Side Gap

The effects of a novel winglet-cavity tip on the flow field and aerodynamic performance of a turbine blade with tip clearance have been investigated in a low-speed wind tunnel. A calibrated five-hole probe is used for the measurement of three-dimensional flows downstream of the cascade. The method of oil-flow visualization is used to show the endwall flow field structure. The distribution of endwall static pressure is measured particularly by using the special moveable endwall. The downstream results show that, compared with the flat tip and cavity tip, the winglet-cavity tip reduces aerodynamic loss in the region of tip leakage vortex and passage vortex effectively and gives a 8.5% reduction of total pressure losses at a tip clearance of τ/ H = 1.0%. Meanwhile, a more uniform flow angle is obtained with the winglet-cavity tip. Thus, the winglet-cavity tip provides better aerodynamic performance. It was found that more endwall flow enters the cavity from the front of suction side gap, combines with the flow entering the tip from the pressure side, and then separates upon the cavity. This reduces the loss of passage vortex. The endwall static pressure indicates that the winglet-cavity tip reduces the driving pressure difference and weakens the tip leakage flow. With the tip clearance increasing, the leakage flow is significantly enhanced. This strengthens the interaction between the tip leakage vortex and the passage vortex. With respect to the flat tip and cavity tip, the winglet-cavity tip obtains the lowest total pressure loss at all tested tip clearances.

Pulsed suction control in a highly-loaded compressor cascade with low suction flow rates

2021 ◽  
pp. 1-39
Author(s):  
Hongxin Zhang ◽  
Shaowen Chen
Keyword(s):  
Flow Rate ◽  
Flow Separation ◽  
Aerodynamic Performance ◽  
Compressor Cascade ◽  
Control Effect ◽  
Suction Force ◽  
Flow Rates ◽  
Suction Control ◽  
Suction Flow ◽  
Highly Loaded

Abstract The influence of pulsed suction (PS) on flow separation and aerodynamic performance in a highly loaded compressor cascade is experimentally studied herein. The excitation frequency is investigated as it determines the effectiveness of PS in flow control. Low suction flow rates are examined to analyze the potential of PS in providing a satisfactory cascade performance. For comparison, the corresponding parameters of steady continuous suction (SCS) are studied as well. Oil flow visualizations and steady and unsteady pressure data are used to characterize the control effects of SCS and PS. The experimental results validate the efficacy of PS in controlling flow separation, even at a reduced suction flow rate of 0.1%. It suppresses passage vortex is suppressed, improving aerodynamic performance. PS provides a better control effect than SCS at different excitation parameters, which can be attributed to twofold main reasons: first, at the same suction flow rate, PS has a larger suction momentum than SCS during the suction phase, resulting in a stronger suction force and having a more profound effect on the flow characteristics; and second, owing to the introduction of pulsed excitation to the suction, PS creates additional vortex structures that energize the boundary layer by transporting high momentum free-stream fluid near the wall. PS is also effective at a higher incidence angle, but its control effect is reduced.

scholarly journals Influences of groove-type casing treatment on the tip leakage flow behaviour in linear compressor cascades at different tip clearances: influence of single groove at mid-chord

ACTA IMEKO ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 277
Author(s):  
Masanao Kaneko
Keyword(s):  
Flow Behaviour ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Suction Surface ◽  
Linear Compressor ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Large Expansion

In this study, the influences of the single groove installed at the mid-chord – which is known to have a large expansion effect on the stable operating flow range of low-speed axial compressors – on the flow behaviour and the loss generation in a linear compressor cascade were investigated numerically at different tip clearances. Reynolds-averaged Navier–Stokes simulations of the incompressible flow in the test cascade were performed, with the computed results clarifying the following remarkable phenomena, which are common to both small and large tip-clearance cases. The single groove locally weakens the tip leakage flow by the decrease in the blade loading and the streaming of the flow near the blade pressure side into the groove, consequently reducing the distance between the tip leakage vortex and the blade suction surface. Meanwhile, although the groove decreases the loss due to the tip leakage vortex generated from the blade leading edge, the loss generation in the entire cascade passage is almost the same as that in the cascade without the groove due to the additional loss generation resulting from the presence of the groove.

scholarly journals Tip Leakage Flow in Linear Compressor Cascade

1993 ◽  
Author(s):  
S. Kang ◽  
C. Hirsch
Keyword(s):  
Design Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Linear Compressor ◽  
Tip Leakage ◽  
Flow Mixing ◽  
Internal Loss ◽  
Linear Compressor Cascade

Tip leakage flow in a linear compressor cascade of NACA 65-1810 profiles is investigated, for tip clearance levels of 1.0, 2.0 and 3.25 percent of chord at design and off-design flow conditions. Data, velocity and pressures, are collected from three transverse sections inside tip clearance and sixteen sections within flow passage. Tip separation vortex influence is identified from the data. Leakage flow mixing is clearly present inside the clearance and has a significant influence on the internal loss.

Numerical and Experimental Investigation of Tip Leakage Vortex Trajectory in an Axial Flow Pump

2013 ◽  
Author(s):  
Desheng Zhang ◽  
Weidong Shi ◽  
Suqing Wu ◽  
Dazhi Pan ◽  
Peipei Shao ◽  
...  
Keyword(s):  
Flow Rate ◽  
Axial Flow ◽  
Tip Clearance ◽  
High Speed Photography ◽  
Rate Condition ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Starting Point ◽  
Axial Flow Pump ◽  
Flow Pump

In this paper, the tip leakage vortex (TLV) structures in an axial flow pump were investigated by numerical and experimental methods. Based on the comparisons of different blade tip clearance size (i.e., 0.5 mm, 1mm and 1.5mm) and different flow rate conditions, TLV trajectories were obtained by Swirling Strength method, and simulated by modified SST k-ω turbulence model with refined high-quality structured grids. A high-speed photography test was carried out to capture the tip leakage vortex cavitation in an axial flow pump with transparent casing. Numerical results were compared with the experimental leakage vortex trajectories, and a good agreement is presented. The detailed trajectories show that the start point of tip leakage vortex appears near the leading edge at small flow rate, and it moves from trailing edge to about 30% chord span at rated flow rate. At the larger flow rate condition, the starting point of TLV shifts to the middle of chord, and the direction of TLV moves parallel to the blade hydrofoil. As the increasing of the tip size, the start point of TLV trajectories moves to the central of chord and the minimum pressure in vortex core is gradually reduced.

Aerodynamic Interaction Between Incoming Vortex and Tip Leakage Flow in a Turbine Cascade

2018 ◽  
Author(s):  
Kai Zhou ◽  
Chao Zhou
Keyword(s):  
Numerical Study ◽  
Aerodynamic Performance ◽  
Leakage Flow ◽  
Computational Domain ◽  
Turbine Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Swirl Generator ◽  
Swirling Vortex

In turbines, secondary vortices and tip leakage vortices develop and interact with each other. In order to understand the flow physics of vortices interaction, the effects of incoming vortex on the downstream tip leakage flow are investigated in terms of the aerodynamic performance in a turbine cascade. Experimental, numerical and analytical methods are used. In the experiment, a swirl generator was used upstream near the casing to generate the incoming vortex, which interacted with the tip leakage vortex in the turbine cascade. The swirl generator was located at ten different pitchwise locations to simulate the quasi-steady effects. In the numerical study, a Rankine-like vortex was defined at the inlet of the computational domain to simulate the incoming swirling vortex. Incoming vortices with opposite directions were investigated. The vorticity of the positive incoming swirling vortex has a large vector in the same direction as that of the tip leakage vortex. In the case of the positive incoming swirling vortex, the vortex mixes with the tip leakage vortex to form one vortex near the tip as it transports downstream. The vortices interaction reduces the vorticity of the flow near the tip, as well as the loss by making up for the streamwise momentum within the tip leakage vortex core. In contrast, the negative incoming swirling vortex has little effects on the tip leakage vortex and the loss. As the negative incoming swirling vortex transports downstream, it is separated from the tip leakage vortex and forms two vortices. A triple-vortices-interaction kinetic analytical model and one-dimensional mixing model are proposed to explain the mechanism of vortex interaction on the aerodynamic performance.

Tip Clearance Investigation of a Ducted Fan Used in VTOL UAVS: Part 1—Baseline Experiments and Computational Validation

2011 ◽  
Author(s):  
Ali Akturk ◽  
Cengiz Camci
Keyword(s):  
Total Pressure ◽  
Aerodynamic Performance ◽  
Test System ◽  
Tip Clearance ◽  
Computational Techniques ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Ducted Fan ◽  
Rans Simulations

Ducted fans that are popular choices in vertical take-off and landing (VTOL) unmanned aerial vehicles (UAV) offer a higher static thrust/power ratio for a given diameter than open propellers. Although ducted fans provide high performance in many VTOL applications, there are still unresolved problems associated with these systems. Fan rotor tip leakage flow is a significant source of aerodynamic loss for ducted fan VTOL UAVs and adversely affects the general aerodynamic performance of these vehicles. The present study utilized experimental and computational techniques in a 22″ diameter ducted fan test system that has been custom designed and manufactured. Experimental investigation consisted of total pressure measurements using Kiel total pressure probes and real time six-component force and torque measurements. The computational technique used in this study included a 3D Reynolds-Averaged Navier Stokes (RANS) based CFD model of the ducted fan test system. RANS simulations of the flow around rotor blades and duct geometry in the rotating frame of reference provided a comprehensive description of the tip leakage and passage flow. The experimental and computational analysis performed for various tip clearances were utilized in understanding the effect of the tip leakage flow on aerodynamic performance of ducted fans used in VTOL UAVs. The aerodynamic measurements and results of the RANS simulations showed good agreement especially near the tip region.

Sign in / Sign up

Export Citation Format

Share Document