Computational Analysis of the Blade Loading on Tip Clearance Effects

Limin Wang,Yadong Liu,Chengqin Li

doi:10.11648/j.ijfmts.20200604.11

Abstract

Gas turbines normally have the rotating and stationary parts. The rotational blades always need clearance to rotation. Blade tip clearance is one of the important parameters affecting performance, safety and stability of a gas turbine engine. However, it is difficult to measure the tip clearance accurately during the tests. The numerical studies are important methods to study the tip clearance effects. Tip clearance effects have been studied for a long time. However, there are still many aspects that are not fully understood and industries still don’t have a good way to perform design with minimum tip clearance losses. In the gas turbine design, the tip clearance considerations are very critical for both performance and reliability. In this paper, we perform the numerical study on the tip clearance impacts during the aerodynamic design, especially the blade loading through blade counts. The study found that the proper blade loading could reduce the tip clearance sensitivity and reduce the tip clearance losses. In the cases of reasonable number of blades, the effect of clearance on the total pressure loss and efficiency had a linear relationship. But in the cases of small number of blades, the effect of clearance on the total pressure loss and efficiency is no longer linear. The study helped turbine designers to consider blade loading and tip clearance together during the turbine design.

Highlights

Gas turbines and aircraft engines need rotational turbo machines to produce the power
This demonstrated that the blade loading and tip clearance combined influences were bigger than the sum of their individual impacts. This was agreed with early study [18] that the secondary flow of the turbine blade was impacted by pitch-width ratio, i.e. blade loading. It demonstrated that the tip clearance losses impacted by the level of the clearances, and impacted by the blade loading
This study further pointed out the optimal pitch-width ratio or blade counts were related to tip clearances

Summary

Introduction

Gas turbines and aircraft engines need rotational turbo machines to produce the power. Tip leakage losses constitute a major source of losses in turbine rotor blades, typically a clearance gap equal to 1 percent of the blade height is associated with a 1-3 percent penalty in stage efficiency without tip clearance flow control. Limin Wang et al.: Computational Analysis of the Blade Loading on Tip Clearance Effects found that when the tip clearance is increased, the efficiency of a turbine rotor decreases significantly. The decrease in tip clearance can reduce the working medium leakage and the loss of the end wall, so as to improve the gas turbine performance. The reducing tip clearance needs to improve the manufacturing capability as well as a better tip clearance control system This study will help to optimize the blade counts based on the tip clearance

Geometry Information

Calculation Details and Grid Independence Validation

The Effect of the Tip Clearance Size on Flow Performance

The Effect of Blade Loading on Tip Clearance

Conclusions