A Model to Study Circumferential Hot Gas Ingestion into Secondary Air Flow Path of an Engine

摘要

Of interest in this study is to model and predict the extent of local hot gas ingestion into secondary air system flow path. In real engines, asymmetry and resulting local hot gas ingestion may occur due to various reasons. Normally, asymmetry in geometric gaps and tolerances and variations in primary gas path pressure may result in some hot gas ingestion. But more importantly, deterioration and failure of critical sealing segment(s), and failure of cooling air supply pipes may result in severe hot gas ingestion. Hot gas ingestion would result in warmer turbine parts, limiting their life and performance significantly. Additionally, asymmetry in temperatures due to local hot gas ingestion may result in distorted bearing support structure leading to detrimental effects. In this study, a simple model is developed by using 1-D pressure, flow and enthalpy modules (Kutz and Speer, 1994) in a network enveloping the extent of an engine. The pseudo-3D modeling approach is applied to a real engine component to estimate the extent of damage due to local hot gas ingestion. Results demonstrate that the model provides a quick and powerful tool for estimating flow and heat transfer information in complex engine cavities with extremely low flow rates without resorting to complex and nearly impossible 3-D CFD simulations. In this study, failure of cooling air supply pipe during engine operation is simulated. The cooling air supply pipes bleed air from high pressure compressor (HPC) and feed air into inter transition duct of a development engine. Failure of supply pipe is simulated by venting one of the pipes to atmosphere. Results demonstrate severe asymmetry in flow and pressure in the secondary airflow path leading to large local hot gas ingestion. Further, large amount of local hot gas ingestion induces circumferential temperature gradients resulting in non-uniform heating and consequent distortions of static and rotating parts. Based on the knowledge of extent of damages, corrective arrangements are also discussed.