Comparison and mathematical modeling of surge avoidance methods in turbojet engine compressor

The sudden surge phenomenon in an axial compressor represents one of the most critical issues that can confront a turbojet engine.This phenomenon primarily arises from the engine ingesting hot exhaust gases from weaponry systems, particularly in military aircraft, potentially leading to engine failure.This study delves into the impact of hot gas ingestion on compressor stability and compares a range of effective methods to prevent surge in such cases which are: (1) air bleed from the compressor, (2) fuel cut-off, (3) gas cooling through water injection at the air inlet.The R29-300 twin-spool turbojet engine was chosen for computational experiments due to the availability of the necessary digital information for mathematical modelling of this engine.It is a two-shaft turbojet engine consisting of a low-pressure compressor (5 stages), a high-pressure compressor (6 stages), an annular combustion chamber, a high-pressure turbine (two stages), and a low-pressure turbine (one stage).The results showed that introducing gases with a heating rate of up to 5000 Kelvin per second causes the low-pressure compressor to exit its stable operating regime and the engine to stall.The effect on the high-pressure compressor was minimal and did not exceed the stability limits, therefore the focus of the procedures was on the low-pressure compressor.The results also showed that both methods 1 and 2 are effective in preventing surge within an acceptable stability range, but they have several drawbacks, including a decrease in engine thrust and efficiency.On the other hand, the water injection method eliminates the root cause of surge by cooling the incoming gases and maintains engine stability.The amount of water required for this process is relatively small and can be carried on aircraft without a significant impact on weight and volume.