scholarly journals Numerical and Experimental Investigations of Steady Micro-Tip Injection on a Subsonic Axial-Flow Compressor Rotor

2006 ◽  
Vol 2006 ◽  
pp. 1-11 ◽  
Author(s):  
Xingen Lu ◽  
Wuli Chu ◽  
Junqiang Zhu ◽  
Zhiting Tong
Keyword(s):  
Mass Flow ◽  
Axial Flow ◽  
Tip Clearance ◽  
Air Injection ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Tip Injection ◽  
Flow Compressor

Steady tip injection has been demonstrated to be an effective means of extending the stable operating range of a tip-critical compressor. This study presents a state-of-the-art design for the tip injection through the casing with flush-mounted inclined holes and the effectiveness of steady micro-air injection to enhance stability in a subsonic axial-flow compressor rotor using an external-air supply. For the tested rotor, experimental results demonstrate that at 53% design speed, the stalling mass flow can be reduced by 7.69% using an injected mass flow equivalent to 0.064% of the annulus flow. Time-dependent CFD simulations were conducted to identify the physical mechanic that accounts for the beneficial effects of the steady micro-air injection on the performance and stability of the compressor. Detailed analyses of the flow visualization at the tip have exposed the different tip flow topologies between the cases without tip injection and with tip injection. It was found that the primary stall margin enhancement afforded by the steady micro-air injection is a result of the tip-clearance flow manipulation. The repositioning of the tip-clearance vortex further towards the trailing edge of the blade passage and delaying the movement of incoming/tip-clearance flow interface to the leading edge plane are the physical mechanisms responsible for extending the compressor stall margin.

Numerical Investigations of the Coupled Flow Through a Subsonic Compressor Rotor and Axial Skewed Slot

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Xingen Lu ◽  
Wuli Chu ◽  
Junqiang Zhu ◽  
Yangfeng Zhang
Keyword(s):  
Axial Flow ◽  
Tip Clearance ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Flow Through ◽  
Flow Compressor

In order to advance the understanding of the fundamental mechanisms of axial skewed slot casing treatment and their effects on the subsonic axial-flow compressor flow field, the coupled unsteady flow through a subsonic compressor rotor and the axial skewed slot was simulated with a state-of-the-art multiblock flow solver. The computational results were first compared with available measured data, that showed the numerical procedure calculates the overall effect of the axial skewed slot correctly. Then, the numerically obtained flow fields were interrogated to identify the physical mechanism responsible for improvement in stall margin of a modern subsonic axial-flow compressor rotor due to the discrete skewed slots. It was found that the axial skewed slot casing treatment can increase the stall margin of subsonic compressor by repositioning of the tip clearance flow trajectory further toward the trailing of the blade passage and retarding the movement of the incoming∕tip clearance flow interface toward the rotor leading edge plane.

The Structure of Tip Clearance Flow in Axial Flow Compressors

1995 ◽  
Vol 117 (3) ◽  
pp. 336-347 ◽  
Author(s):  
B. Lakshminarayana ◽  
M. Zaccaria ◽  
B. Marathe
Keyword(s):  
Axial Flow ◽  
Tip Clearance ◽  
Complex Nature ◽  
Tip Leakage Flow ◽  
Tip Clearance Flow ◽  
Wall Boundary Layer ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Blade Tip ◽  
Flow Compressor

Detailed measurements of the flow field in the tip region of an axial flow compressor rotor were carried out using a rotating five-hole probe. The axial, tangential, and radial components of relative velocity, as well as the static and stagnation pressures, were obtained at two axial locations, one at the rotor trailing edge, the other downstream of the rotor. The measurements were taken up to about 26 percent of the blade span from the blade tip. The data are interpreted to understand the complex nature of the flow in the tip region, which involves the interaction of the tip leakage flow, the annulus wall boundary layer and the blade wake. The experimental data show that the leakage jet does not roll up into a vortex. The leakage jet exiting from the tip gap is of high velocity and mixes quickly with the mainstream, producing intense shearing and flow separation. There are substantial differences in the structure of tip clearance observed in cascades and rotors.

Effect of tip clearance size on the performance of a low-reaction transonic axial compressor rotor

2019 ◽  
Vol 234 (2) ◽  
pp. 127-142
Author(s):  
Wei Zhu ◽  
Songtao Wang ◽  
Longxin Zhang ◽  
Jun Ding ◽  
Zhongqi Wang
Keyword(s):  
Numerical Simulations ◽  
Dynamic Balance ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Flow Phenomena

This study aimed to enhance the understanding of flow phenomena in low-reaction aspirated compressors. Three-dimensional, multi-passage steady and unsteady numerical simulations are performed to investigate the performance sensitivity to tip clearance variation on the first-stage rotor of a multistage low-reaction aspirated compressor. Three kinds of tip clearance sizes including 1.0τ, 2.0τ and 3.0τ are modeled, in which 1.0τ corresponds to the designed tip clearance size of 0.2 mm. The steady numerical simulations show that the overall performance of the rotor moves toward lower mass flow rate when the tip clearance size is increased. Moreover, energy losses, efficiency reduction and stall margin decrease are also observed with increasing tip clearance size. This can be mostly attributed to the damaging impact of intense tip clearance flow. For unsteady simulation, the result shows periodical oscillation of the tip leakage vortex and a “two-passage periodic structure” in the tip region at the near-stall point. The occurrence of the periodical oscillation is due to the severe interaction between the tip clearance flow and the shock wave. However, the rotor operating state is still stable at this working point because a dynamic balance is established between the tip clearance flow and incoming flow.

scholarly journals Influences of Tip Cooling Injection on Tip Clearance Control at Design and Off-Design Incidences

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
Maosheng Niu ◽  
Shusheng Zang
Keyword(s):  
Heat Transfer ◽  
Tip Clearance ◽  
Air Injection ◽  
Turbine Cascade ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
Blade Tip ◽  
Design Value ◽  
Tip Injection ◽  
Clearance Control

A numerical investigation has been performed to study the influences of cooling injection from the blade tip surface on controlling tip clearance flow in an unshrouded, high-turning axial turbine cascade. Emphasis is put on the analysis of the effectiveness of tip injection when the approaching flow is at design and off-design incidences. A total of three incidence angles are investigated, 7.4°, 0°, 0°, 0°, and 7.6°, 0° relative to the design value. The results indicate that even at the off-design incidences, tip injection can also act as an obstruction to the tip clearance flow and weaken the interaction between the passage flow and the tip clearance flow. It is also found that tip injection causes the tip clearance loss to be less sensitive to the incidences. Moreover, with injection, at all these incidences the heat transfer conditions are improved significantly on the blade tip surface in the middle and aft parts of blade. Thus, tip injection is proved to be an effective method of controlling tip clearance flow, even at off-design conditions. Beside that, an indirect empirical correlation is observed to be able to perform well in predicting the losses induced by tip clearance flow at design and off-design conditions, no matter whether air injection is active or not.

Unsteady tip clearance flow pattern in an isolated axial compressor rotor with micro tip injection

2007 ◽  
Vol 16 (4) ◽  
pp. 309-320 ◽  
Author(s):  
Shaojuan Geng ◽  
Hongwu Zhang ◽  
Jingyi Chen ◽  
Weiguang Huang
Keyword(s):  
Flow Pattern ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Tip Clearance Flow ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Tip Injection

Experimental Investigation of Stepped Tip Gap Effects on the Performance of a Transonic Axial-Flow Compressor Rotor

1998 ◽  
Vol 120 (3) ◽  
pp. 477-486 ◽  
Author(s):  
D. W. Thompson ◽  
P. I. King ◽  
D. C. Rabe
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Percent Improvement ◽  
Flow Compressor

The effects of stepped-tip gaps and clearance levels on the performance of a transonic axial-flow compressor rotor were experimentally determined. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine causing geometries were investigated consisting of three step profiles at each of three clearance levels. For small and intermediate clearances, stepped tip gaps were found to improve pressure ratio, efficiency, and flow range for most operating conditions. At 100 percent design rotor speed, stepped tip gaps produced a doubling of mass flow range with as much as a 2.0 percent increase in mass flow and a 1.5 percent improvement in efficiency. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an optimum casing profile.

Experimental Investigation of Stepped Tip Gap Effects on the Performance of a Transonic Axial-Flow Compressor Rotor

1997 ◽  
Author(s):  
Donald W. Thompson ◽  
Paul I. King ◽  
Douglas C. Rabe
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Compressor Performance ◽  
Flow Compressor

The effects of stepped tip gaps and clearance levels on the performance of a transonic axial-flow compressor rotor were experimentally determined. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were investigated consisting of three step profiles at each of three clearance levels. For small and intermediate clearances, stepped tip gaps were found to improve pressure ratio, efficiency, and flow range for most operating conditions. At 100% design rotor speed, stepped tip gaps produced a doubling of mass flow range with as much as a 2.0% increase in mass flow and a 1.5% improvement in efficiency. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an optimum casing profile.

Effect of Tip Clearance on the Prediction of Nonsynchronous Vibrations in Axial Compressors

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Martin Drolet ◽  
Huu Duc Vo ◽  
Njuki W. Mureithi
Keyword(s):  
Operating Temperature ◽  
Axial Flow ◽  
Tip Clearance ◽  
Turbine Engine ◽  
Tip Clearance Flow ◽  
Background Theory ◽  
Proposed Model ◽  
Clearance Flow ◽  
Flow Compressor ◽  
Nonsynchronous Vibrations

This work investigates the effect of tip clearance size and operating temperature on the predictions of the critical rotor speed at which nonsynchronous vibrations (NSV) can be encountered in a turbine engine axial flow compressor. It has been proposed that the tangential tip clearance flow, observed at high blade loading near stall, can act as an impinging resonant jet on the upcoming blades and could be the underlying physics behind NSV. A model, in the form of an equation to predict the critical blade tip speed at which NSV can occur, was proposed based on the Jet-Core Feedback Theory and was experimentally verified by Thomassin et al. (2008, “Experimental Demonstration to the Tip Clearance Flow Resonance Behind Compressor NSV,” Proceedings of GT2008: ASME Turbo Expo Power for Land, Sea and Air, Berlin, Germany, Jun. 9–13, Paper No. GT2008-50303). In the equation, a factor k that was called the “tip instability convection coefficient” was measured experimentally and found to be influenced by the tip clearance size and operating temperature. This factor has a significant impact on the accuracy of the NSV predictions obtained using the proposed model. This paper propose a numerical experiment to determine the effect of tip clearance size and temperature on k, in order to improve the critical NSV tip speed predictions using the proposed model. A review of the NSV model is presented along with the relevant background theory on the subject. Two different blade geometries are simulated to provide a generic approach to the study. The leakage flow velocity is calculated to estimate k and a correlation is proposed to model the behavior of the k parameter as a function of the tip clearance size. The latter was found to significantly improve the critical NSV speed predictions. The effect of operating temperature on k is also discussed. Finally, the variation of k with the aerodynamic loading is assessed and compared with available data in the literature to strengthen the generic nature of the results.

Investigation for the Effects of Circumferential Grooves on the Unsteadiness of Tip Clearance Flow to Enhance Compressor Flow Instability

2010 ◽  
Author(s):  
Shengfeng Zhao ◽  
Xingen Lu ◽  
Junqiang Zhu ◽  
Hongwu Zhang
Keyword(s):  
Physical Mechanism ◽  
Flow Instability ◽  
Axial Flow ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Casing Treatment ◽  
Circumferential Groove ◽  
Clearance Flow

The use of slots and grooves in the shroud over the tips of compressor blades, known as casing treatment, is a powerful method to control tip leakage flow through the clearance gap and enhance the flow stability in compressors. This paper presents a contribution to the understanding of the physical mechanism by which circumferential groove casing treatment manipulates the tip clearance flow’s unsteadiness. A series of computational studies were carried out to understand the physical mechanism responsible for improvement in stall margin of a high subsonic axial-flow compressor rotor due to the circumferential groove casing treatment from an unsteady viewpoint. Detailed analyses of the flow visualization at the tip have exposed the different tip flow topologies between the cases with circumferential groove and with untreated smooth wall. It was found that the primary stall margin enhancement afforded by the circumferential groove casing treatment is a result of the unsteady tip clearance flow manipulation. Breaking balance of incoming/tip clearance flow axial momentum by inducing the radial movement and tangential movement and delay the occurrence of tip clearance’s unsteadiness are the physical mechanisms responsible for extending the compressor stall margin.

A Correlation of Leakage Vortex Cavitation in Axial-Flow Pumps

1994 ◽  
Vol 116 (3) ◽  
pp. 551-557 ◽  
Author(s):  
K. J. Farrell ◽  
M. L. Billet
Keyword(s):  
Flow Field ◽  
Axial Flow ◽  
Suction Side ◽  
Tip Clearance ◽  
Vortical Flow ◽  
Data Sets ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Clearance Flow ◽  
High Reynolds

Tip clearance flow in turbomachinery can lead to losses in efficiency and stall margin. In liquid handling turbomachinery, the vortical flow field, formed from the interaction of the leakage flow with the through-flow, is subject to cavitation. Furthermore, this flow field is complex and not well understood. A correlation of variables which predict the vortex minimum pressure has been formulated. Measurements of the important variables for this correlation have been made on a high Reynolds number (3 × 106) axial-flow test rig. The correlation has been applied to the measured data and other data sets from the literature with good agreement. An optimum tip clearance has been theoretically identified as experiments have shown. Observations of cavitation indicate a second vortex originating along the suction side trailing edge.

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