Influence of Inter‐row Gap Value on Turbine Losses

Paul G A Cizmas,Harry F Martin,Shun Chen,Corbett R Hoenninger

doi:10.1155/s1023621x01000288

Abstract

This paper presents the results of a numerical investigation of the gap influence on the turbine efficiency. The rotor‐stator interaction in a (1/2)‐stage turbine is simulated by solving the quasi‐three‐dimensional unsteady Euler/Navier‐Stokes equations using a parallelized numerical algorithm. The reduced turnaround time and cost/MFLOP of the parallel code was crucial to complete the numerous run cases presented in this paper. The inter‐row gap effect is evaluated for 4 gaps, 3 radial positions and 3 angular velocities. As expected, the results presented in this paper show that the efficiency increases and losses decrease while the gap size increases. The maximum efficiency location, however, corresponds to values of the gap size which may be too large for practical use (approximately inch). Fortunately, a local maximum efficiency and minimum losses location has been found at approximately 0.5 inches gap size. The efficiency variation near the local optimum is large, in some configurations being as high as 1.4 points for a gap size variation of only 0.076 inches. Data produced by the numerical simulations can be used to develop a design rule based on the inter‐row gap size.

Highlights

Numerical simulation of unsteady effects in turbomachinery is a necessary step for advanced design and analysis
The maximum efficiency and the minimum losses location, corresponds to values of the gap size which may be too large for practical use
A local maximum efficiency location has been found at approximately 0.5 inches gap size

Summary

Introduction

Numerical simulation of unsteady effects in turbomachinery is a necessary step for advanced design and analysis. Neither stall flutter nor rotating stall can be predicted using steady flow simulation These dangerous phenomena might happen due to the fact that blade loading and turbine inlet temperature are constantly increased, quite often pushing the engine out of the envelope of traditional designs. Another reason to simulate unsteady flows in turbomachinery is to be able to predict rotor-stator interaction. Experimental investigations and numerical simulations have shown that efficiency can be improved by optimizing the circumferential relative position of consecutive airfoil rows The purpose of this project is to numerically investigate another important parameter of rotor-stator interaction, the interrow gap size. This paper will present the influence of gap size on the turbine efficiency

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