Thermodynamic efficiency analysis and cycle optimization of deeply precooled combined cycle engine in the air-breathing mode

• Published in: Acta astronautica Vol. 138; pp. 394 - 406
• Main Authors: Zhang, Jianqiang, Wang, Zhenguo, Li, Qinglian
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01.09.2017; Elsevier BV
• Subjects: Air breathing engines; Combined cycle engines; Combustion chambers; Component-level modeling; Computing time; Cycle efficiency; Cycle optimization; Efficiency; Equivalence ratio; Exergy; Exergy analysis; Flow rates; Flow velocity; Heat exchangers; Helium; Helium recirculation scheme; Hydrogen; Optimization; Rocket engines; SABRE; Studies; Thermodynamic efficiency; Thermodynamics; Cycle optimization; Component-level modeling; Exergy analysis; Helium recirculation scheme; Cycle efficiency; SABRE
• ISSN: 0094-5765; 1879-2030
• DOI: 10.1016/j.actaastro.2017.06.011

The efficiency calculation and cycle optimization were carried out for the Synergistic Air-Breathing Rocket Engine (SABRE) with deeply precooled combined cycle. A component-level model was developed for the engine, and exergy efficiency analysis based on the model was carried out. The methods to improve cycle efficiency have been proposed. The results indicate cycle efficiency of SABRE is between 29.7% and 41.7% along the flight trajectory, and most of the wasted exergy is occupied by the unburned hydrogen in exit gas. Exergy loss exists in each engine component, and the sum losses of main combustion chamber(CC), pre-burner(PB), precooler(PC) and 3# heat exchanger(HX3) are greater than 71.3% of the total loss. Equivalence ratio is the main influencing factor of cycle, and it can be regulated by adjusting parameters of helium loop. Increase the maximum helium outlet temperature of PC by 50 K, the total assumption of hydrogen will be saved by 4.8%, and the cycle efficiency is advanced by 3% averagely in the trajectory. Helium recirculation scheme introduces a helium recirculation loop to increase local helium flow rate of PC. It turns out the total assumption of hydrogen will be saved by 9%, that's about 1740 kg, and the cycle efficiency is advanced by 5.6% averagely. •A component-level model for SABRE is developed and exergy analysis is carried out.•Hydrogen flow rate should be reduced by adjusting helium loop for cycle optimization.•Increasing the helium outlet temperature of precooler will improve cycle efficiency.•Helium recirculation scheme improves the cycle efficiency by 5.6%.