IMPROVEMENT OF A TURBINE ENGINE START BY AN EXTERNAL OXYGEN-RICH GAS GENERATOR

Abstract

Starting of turbine engines is often required under ambient temperature and pressure that are far from their design values. Under such conditions, less air enters the combustion chamber, precluding more fuel to be burned, and making it difficult to produce sufficient energy to accelerate the engine up to idle speed. Common solutions introduce additional oxygen into the combustion chamber to enable more fuel to burn and improve the combustion efficiency, thus providing more energy to the hot gas driving the turbine to accelerate the rotor. Adding oxygen also enables faster and more reliable starting of turbine engines, even under adverse ambient conditions. Conventional oxygen-addition units require storage and supply systems, which pose a great problem for small turbine engines, where space and weight requirements are typically tight, and reliable starting is often needed. The novel approach presented in this paper uses an external module that supplies hot oxygen-rich gas to the combustion chamber, thus providing both oxygen enrichment and ignition of the air-fuel mixture. Consequently, the starting capability of the engine is enhanced. The module’s exterior location enables easy replacement and/or retrofit. Several modes of implementation and their combination are considered. One implementation may use the hot discharge from a pyrotechnic igniter to thermally decompose a solid oxidizer grain, which releases hot oxygen-rich gaseous products. Another implementation may utilize a uniform oxygen-rich solid-propellant grain, releasing hot oxygen-rich combustion products. Preliminary tests with GAP/KP/AP-based oxygen-rich propellant compositions were conducted.