Tip clearance

About: Tip clearance is a research topic. Over the lifetime, 2637 publications have been published within this topic receiving 32671 citations.

Research Progress of Tip Winglet Technology in Compressor

Abstract: In the present study, the research progress of tip winglets that control tip clearance leakage flow in compressors is reviewed. Firstly, the effects of tip leakage flow on the aerodynamic performance of the compressor are presented. Subsequently, the development of tip winglet technology is reviewed. Next, a series of studies on compressor tip winglet technology are conducted. Besides, the effects of tip winglets on the aerodynamic performance of rectangular cascades of low-speed and high-subsonic compressors, subsonic compressor rotor and transonic compressor rotor are discussed, respectively, and the control effect of tip winglet technology combined with tip groove design on tip leakage is investigated. Lastly, the subsequent development direction and research prospect of compressor tip winglet technology are presented.

Axial flow turbine with low shroud leakage losses

Abstract: An axial flow turbine (1) comprises a turbine casing (7) and a blade ring (2) having a shroud (5) being spaced apart from the casing thereby forming a radial tip clearance (8), through which a leakage flow is passing during operation of the turbine, wherein the casing (7) comprises a deflector (11) arranged outside the tip clearance and adapted to alter the cavity flow such that the leakage flow is turned from axial direction to radial direction and/or such that a downstream part of the cavity (8) is aerodynamically blocked by the deflector.

Stall Inception, Evolution and Control in a Low Speed Axial Fan With Variable Pitch in Motion

Abstract: Obtaining the right pitch in turbomachinery blading is crucial to efficient and successful operations. Engineers adjust the rotor’s pitch angle to control the production or absorption of power. Even for low speed fans this is a promising tool. This paper focuses on a low speed axial fan’s inception and the evolution of the flow instabilities in the tip region which drive the stall onset. The authors conducted an experimental study to investigate the inception patterns of rotating stall evolution at different rotor blade stagger-angle settings with the aim of extending the stable operating range. The authors drove the fan to stall at the design stagger-angle setting and then operated the variable pitch mechanism in order to recover the unstable operation. They measured pressure fluctuations in the tip region of the low-speed axial-flow fan using a variable pitch in motion mechanism, with flush mounted probes. The authors studied the flow mechanisms for spike and modal stall inceptions in this low-speed axial-flow fan which showed relatively small tip clearance. The authors cross-correlated the pressure fluctuations and analysed the cross-spectra in order to clarify blade pitch, end-wall flow, and tip-leakage flow influences on stall inception during the transient at the rotor blades’ different stagger-angle settings. The authors observed a rotating instability near the maximum pressure-rise point at both design and low stagger-angle settings. The stall inception patterns were a spike type at the design stagger-angle setting and a modal type at the low stagger-angle setting as a result of the interaction between the incoming flow, tip-leakage flow and end-wall backflow.Copyright © 2011 by ASME

Investigation of clearance flows in deeply scalloped radial turbines

Abstract: The tip clearance, backface clearance, and backface cavity clearance flows in deeply scalloped radial turbines are numerically investigated in this article. The secondary flow structures in the rot...

Tip-Bed Velocity and Scour Depth of Horizontal-Axis Tidal Turbine with Consideration of Tip Clearance

Abstract: The scouring by a tidal turbine is investigated by using a joint theoretical and experimental approach in this work. The existence of a turbine obstructs a tidal flow to divert the flow passing through the narrow channel in between the blades and seabed. Flow suppression is the main cause behind inducing tidal turbine scouring, and its accelerated velocity is being termed as tip-bed velocity (Vtb). A theoretical equation is currently proposed to predict the tip-bed velocity based on the axial momentum theory and the conservation of mass. The proposed tip-bed velocity equation is a function of four variables of rotor radius (r), tip-bed clearance (C), efflux velocity (V0) and free flow velocity (V∞), and a constant of mass flow coefficient (Cm) of 0.25. An experimental apparatus was built to conduct the scour experiments. The results provide a better understanding of the scour mechanism of the horizontal axis tidal turbine-induced scour. The experimental results show that the scour depth is inversely proportional to tip-bed clearance. Turbine coefficient (Kt) is proposed based on the relationship between the tip-bed velocity and the experimental tidal turbine scour depth. Inclusion of turbine coefficient (Kt) into the existing pier scour equations can predict the maximum scour depth of a tidal turbine with an error range of 5–24%.