Key issues and cooling performance comparison of different closed Brayton cycle based cooling systems for scramjet

摘要

Applying the closed Brayton cycle (CBC) to scramjet for cooling purpose is a potential technology to relieve the pressure of cooling requirement in hypersonic vehicles. This study identifies the key issues in the CBC-based cooling systems and performs performance comparison to find the best cycle layout which has the lowest fuel consumption for cooling. Three typical layouts, the original simple CBC (SCBC), recuperated CBC (RCBC) and supercritical carbon dioxide cycle (S-CO2), and two common working fluids (carbon dioxide and helium) are selected in this paper. Results show that a higher compressor outlet pressure can decrease the pressure loss in cooling channel. There is a limit turbine inlet temperature due to the excessive wall temperature. The fuel consumption for cooling is mainly affected by the fuel outlet temperature, not thermal efficiency. Then the improved S-CO2 is proposed by changing working fluid inlet temperature and location of pinch point in the fuel-working fluid heat exchanger. The comparative study indicates that the improved S-CO2 has the best cooling performance. It can reduce 30% of fuel consumption for cooling compared with the conventional regenerative cooling system and output 167.9 kW power simultaneously. Besides, the optimal compressor inlet temperature of S-CO2 for cooling is higher than that of general S-CO2.