Tip clearance

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

Experimental Measurements of the Flow and Heat Transfer of a Square Jet Impinging on an Array of Square Pin Fins

Abstract: An experimental investigation was conducted to explore the flow behavior, pressure drop, and heat transfer due to free air jet impingement on square in-line pin fin heat sinks (PFHS) mounted on a plane horizontal surface A parametrically consistent set of aluminum heat sinks with fixed base dimension of 25 × 25 mm was used, with pin heights varying between 125 mm and 225 mm, and fin thickness between 15 mm and 25 mm A 6:1 contracting nozzle having a square outlet cross sectional area of 25 × 25 mm was used to blow air at ambient temperature on the top of the heat sinks with velocities varying from 2 to 20 m/s The ratio of the gap between the jet exit and the pin tips to the pin height, the so-called tip clearance ratio, was varied from 0 (no tip clearance) to 1 The stagnation pressure recovered at the center of the heat sink was higher for tall pins than short pins The pressure loss coefficient showed a little dependence on Re, increased with increasing pin density, and pin diameter, and decreased with increasing pin height and clearance ratio The overall base-to-ambient thermal resistance decreased with increasing Re number, pin density and pin diameter Surprisingly, the dependence of the thermal resistance on the pin height and clearance ratio was shown to be mild at low Re, and to vanish at high Re numberCopyright © 2002 by ASME

Compressor tip clearance control and gas turbine engine

Abstract: A unique compressor includes a rotating compressor blade having a blade tip; a compressor case having a blade track disposed opposite the blade tip; and a tip clearance control system including a fluid impingement structure. This structure has a plurality of openings to impinge a fluid received from a diffuser onto the compressor case. The tip clearance control system is configured to control a clearance between the blade tip and the blade track by impinging the fluid onto the compressor case and modulating the same with a valve in fluid communication with the diffuser. A further form includes a unique gas turbine engine having a compressor with a compressor blade tip, a compressor case disposed opposite the blade tip, and a fluid impingement structure having openings to impinge a fluid onto the case. Also included are other apparatuses, systems, devices, hardware, methods, and combinations for compressor blade tip clearance control.

The Effects of Tip Leakage Flow on the Performance of Multistage Compressors Used in Small Core Engine Applications

Abstract: Large rotor tip clearances and the associated tip leakage flows are known to have a significant effect on overall compressor performance. However, detailed experimental data reflecting these effects for a multistage compressor are limited in the open literature. As design trends lead to increased overall compressor pressure ratio for thermal efficiency benefits and increased bypass ratios for propulsive benefits, the rear stages of the high-pressure compressor will become physically small. Because rotor tip clearances cannot scale exactly with blade size due to the margin needed for thermal growth considerations, relatively large tip clearances will be a reality for these rear stages. Experimental data have been collected from a three-stage axial compressor to assess performance with three-tip clearance heights representative of current and future small core machines. Trends of overall pressure rise, stall margin, and efficiency are evaluated using clearance derivatives, and the summarized data presented here begin to narrow the margin of tip clearance sensitivities outlined by previous studies in an effort to inform future compressor designs. Furthermore, interstage measurements show stage matching changes and highlight specific differences in the performance of rotor 1 and stator 2 compared to other blade rows in the machine.