A System for Identifying Compressor Operating Limits in Gas Turbine Engines

Abstract This paper introduces a novel test system capable of identifying compressor operating limits by directly testing on gas turbine engines. The system configuration is based on the fuel spiking method [2], which drives the compressor to the surge limit, accurately determining the compressor’s instability boundary. The method involves injecting a large amount of fuel into the combustion chamber for a short duration (up to 200 ms) while the engine is running stably. This results in a rapid increase in the post-combustion temperature (T4), raising the T4/T2 temperature ratio [7] (where T2 is the compressor inlet temperature), and thus causing a sudden rise in the compressor discharge pressure (P3) to the point of instability without significantly increasing engine speed. The system employs a high-flow, high-pressure fuel pump, while the fuel spiking duration and flow rate are controlled by a proportional valve. Excess fuel is returned to the fuel tank via a exhaust valve. To validate the system, static engine tests were performed to confirm the fuel spike flow and duration with varying valve positions, ranging from 50 to 200 ms. The system enables real-time detection of compressor surge and helps to reduce test time and costs, while ensuring safe engine operation. This system was successfully used to detect surge events on a small gas turbine engine. The results demonstrate the system’s effectiveness in determining compressor surge limits across a wide operating range from idle to maximum RPM, offering significant advantages in terms of cost reduction, test time, and operational safety.