Tip clearance

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

Turbine tip clearance measurement

Abstract: A measuring assembly for use in a gas turbine engine includes an indicia portion that extends radially inwardly from an inner surface of a ring seal structure to a location radially inwardly from tips of blades mounted on a rotor. The indicia portion of the measuring assembly comprises a section that is abraded by the blades during rotational movement of the rotor to provide a visual indication of a distance between the tips of the blades and the inner surface.

An Experimental and Numerical Study on the Aerothermal Characteristics of a Ribbed Transonic Squealer-Tip Turbine Blade With Purge Flow

Abstract: Detailed heat transfer coefficient (HTC) and film cooling effectiveness (Eta) distribution on a squealer tipped first stage rotor blade were measured using an infrared (IR) technique. The blade tip design, obtained from a Solar Turbines Inc. gas turbine, consisted of double purge hole exits and four ribs within the squealer cavity, with a bleeder exit port on the pressure side close to the trailing edge. The tests were carried out in a transient linear transonic wind tunnel facility under land-based engine representative Mach/Reynolds number. Measurements were taken at an inlet turbulent intensity of Tu =12%, with exit Mach numbers of 0.85 (Reexit=9.75x10 5 ) and 1.0 (Reexit = 1.15x10 6 ) with the Reynolds number based on the blade axial chord and the cascade exit velocity. The tip clearance was fixed at 1% (based on engine blade span) with a purge flow blowing ratio BR = 1.0. At each test condition, an accompanying numerical study was performed using Reynolds Averaged Navier Stokes (RANS) equations solver ANSYS Fluent to further understand the tip flow characteristics. The results showed that the tip purge flow has a blocking effect on the leakage flow path. Furthermore, the ribs significantly altered the flow (and consequently heat transfer) characteristics within the squealer tip cavity resulting in a significant reduction in film cooling effectiveness. This was attributed to increased coolant-leakage flow mixing due to increased recirculation within the squealer cavity. Overall, the peak heat transfer coefficient on the cavity floor increased with exit Mach/Reynolds number. NOMENCLATURE BR Averaged blowing Ratio (BR = ρcUc /ρ∞ U∞,avg )

Effects of the Tip Clearance on Vortical Flow and Its Relation to Noise in an Axial Flow Fan

Abstract: Three-dimensional vortical flow structures and velocity fluctuation near the rotor tip in an axial flow fan having two different tip clearances have been investigated by experimental analysis using a rotating hot wire probe and a numerical simulation. It is found that a tip leakage vortex is observed in the blade passage, which has a major role near the rotor tip. The tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction, and forms a local recirculation region resulting from a vortex breakdown inside the blade passage. The recirculation region is enlarged by increasing the tip clearance. The larger recirculation region induces the acceleration of the through flow, thus resulting in the increase of the broadband noise. High velocity fluctuation is observed at the interference region between the tip leakage vortex and the through flow in the flow field where the tip leakage vortex is tightly rolled up without its breakdown. Near the casing wall, a discrete frequency is formed between tip leakage vortex core and rotor trailing edge.

Effect of Tip Clearance on the Cavitation Performance of a Turbopump Inducer

Abstract: The characteristics of steady and unsteady cavitation in a two-bladed inducer for a turbopump are investigated. A helical inducer with inlet tip blade angle of 7.8 deg and a tip solidity of 2.7 is tested using water as a working fluid. To determine the effect of tip clearance on the inducer performance, a series of experiments is conducted at three different tip clearances. As the tip clearance increases, the inducer head decreases and the critical cavitation number increases. Unsteady pressure measurements at the inducer inlet indicate the existence of attached cavitation and cavitation surge, but no rotating cavitation in the test inducer. Attached cavitation and cavitation surge appear for all three cases of tip clearance. The cell number and propagation speed of the attached cavitation are determined through a cross-correlation analysis. In the case of attached cavitation, one cell rotates at the same speed as that of the inducer. In addition, the surge frequency decreases with a decrease in the cavitation number, and the ratio of surge frequency to inducer rotational frequency is found to range from 0.07 to 0.20.