Verification at Mach 4 heat conditions of an annular microtube-typed precooler for hypersonic precooled engines

The precooler with high power-to-weight ratios and robustness is a core component of hypersonic precooled engines to operate efficiently at the full speed range. In order to figure out the feasibility of precooler technology, an annular microtube-typed precooler was designed and manufactured. A high temperature test platform consisting of an extreme thermal environment system and a closed S-Helium loop system was built to experimentally verify the operating performance and reliability of this novel precooler. Moreover, a parameter matching method was proposed for stably operating the test platform. On these basis, an 1800-seconds longtime precooler performance test simulating Mach4 heat conditions and constantly supplying S-Helium at 8 MPa was successfully conducted. The test results are in a great agreement with the model results and the maximum error of the heat transfer rate is within ± 10%. The manufactured microtube-typed precooler exhibits its long-term resistance to harsh operating environment (at temperature of nearly 1000 K and pressure of over 8 MPa) and maintains its structural integrity after thermal cycles with an acceptable leakage rate of below 3vol%/h. The airflow temperatures were quenched in excess of 600 K in the test which demonstrates the precooler's ability to cool airflow at speeds significantly beyond the limit of any jet-engine powered aircraft. In addition, the measured power/weight ratio is up to 100 kW/kg, which is in the lead in precooler technology to the authors’ knowledge.