Film Cooling Patterns over an Aircraft Engine Turbine Endwall with Slot Leakage and Discrete Hole Injection

Abstract

Detailed characteristics of film cooling from discrete injection and purge flow, and associated coolant injection patterns are presented over a turbine endwall for wide engine-representative coolant flow rate ranges. Measurements, in combination with numerical simulations, are performed in a linear cascade that is geometrically and aerodynamically scaled up from the hub section of the turbine vane. Reynolds numbers at the vane cascade inlet are varied from 1.40 × 105 to 4.20 × 105, representing the variations of real engine operating conditions (from take-off to cruise conditions). In order to examine the isolated and combined cooling effects, discrete coolant injection and purge flow for the endwall cooling can be injected separately or simultaneously. Numerical simulations are conducted to gain further insight into interactions between endwall-nearby secondary flows and coolant injection. Additionally, a net heat flux reduction parameter is used to evaluate overall film cooling performance of the cooling scheme, that takes heat transfer enhancement by coolant injection into consideration. Results show that endwall-nearby flow structures dictate thermal protection patterns. Increasing coolant flow rates decreases effectiveness values of discrete film cooling but improves cooling effectiveness of purge flow. In spite of no direct interactions between discrete injection and purge flow, adding purge flow could help enhance discrete film cooling effectiveness. Higher passage inlet Reynolds number leads to reduced mixing of coolant injection and mainstream flows, resulting in improved effectiveness values. Changing trends of overall cooling performance for purge flow and discrete film cooling by increasing coolant flow rates are opposite but those are the same by increasing Reynold numbers.