Tip clearance

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

Turbine Blade Tip External Cooling Technologies

Abstract: This article provides an overview of gas turbine blade tip external cooling technologies. It is not the intention to comprehensively review all the publications from past to present. Instead, selected reports, which represent the most recent progress in tip cooling technology in open publications, are reviewed. The cooling performance on flat tip and squealer tip blades from reports are compared and discussed. As a generation conclusion, tip clearance dimension and coolant flow rate are found as the most important factors that significant influence the blade tip thermal performance was well as the over tip leakage (OTL) flow aerodynamics. However, some controversial trends are reported by different researchers, which could be attributed to various reasons. One of the causes of this disagreement between different reports is the lacking of unified parametric definition. Therefore, a more appropriate formula of blowing ratio definition has been proposed for comparison across different studies. The last part of the article is an outlook of the new techniques that are promising for future tip cooling research. As a new trend, the implementation of artificial intelligence techniques, such as genetic algorithm and neural network, have become more popular in tip cooling optimization, and they will bring significantly changes to the future turbine tip cooling development.

Effect of Blade Tip Configuration on Tip Clearance Loss of a Centrifugal Impeller

Abstract: According to the theory presented by the authors, the tip clearance loss of an unshrouded centrifugal impeller mainly consists of two kinds of loss; one is the drag due to the leakage flow through the blade tip clearance and the other is the pressure loss to support the fluid in the thin annular clearance space between the shroud and the blade tip against the pressure gradient in the meridional plane without blades. The former is proportional to the leakage flow or the contraction coefficient of leakage flow. The authors have conducted performance tests using an impeller with sixteen backward-leaning blades in three configurations of the blade tip: round edge, sharp square edge and edge with an end-plate. The experimental tip clearance effects can be predicted by the theory assuming reasonable contraction coefficients. They are 0.91, 0.73 and 0.53 for the respective tip configurations. The impeller efficiency is improved by about 1.5 point by reducing the contraction coefficient from 0.91 to 0.53 providing that the tip clearance ratio at the exit of impeller is 0.1. More improvement is expected for an impeller with highly loaded blades where the leakage loss shares the major part of the tip clearance loss.Copyright © 1989 by ASME

Outlet guide vanes for axial flow fans

Abstract: An outlet guide vane system is disclosed for axial flow fans. Construction details are described which reduce losses in the end wall regions of the vanes, particularly for axial flow fans operating at low flow coefficient with strong localized swirl associated with upstream rotor tip clearance flows. In the preferred embodiment, the vane spanwise airfoil stacking line is approximately straight, while leaning circumferentially toward the incoming swirl flow over the majority of the radial span. The stacking line then curves abruptly in the opposite direction over the radially outboard spanwise portion, so as to lean away from the incoming swirl at the vane tip station. The radially outboard portion of the vanes simultaneously include a gradual increase in vane stagger angle, vane camber angle and vane chord. The vane may also include an axial sweep component.