Full scale civil aircraft engine cold start experiment in climatic environmental test laboratory

In order to solve the strong disturbance and safety problems caused by the extreme low temperature start up experiment of the full-scale civil aircraft engine in the closed large climatic environmental test laboratory, based on existing capabilities of the laboratory, the aircraft engine cold start experiment technology was developed from two aspects: engine exhaust gas discharge and low temperature air make-up. In the aspect of engine exhaust gas discharge, a concept of “split discharge” and a discharge air flow rate estimation method for high bypass ration turbofan engines were proposed, which reduced the low temperature air flow discharged from the laboratory. In the aspect of low temperature air make-up, liquid N₂ was used as a cold source to cool down the normal temperature air outside the laboratory to extremely low temperature of −50 ℃ and continuously replenish it into the laboratory to make up for discharge losses, and maintain the stability of the low temperature environment in the laboratory and the balance of indoor and outdoor pressure for the experiment safety. For the first time in China, the airworthiness compliance experiment of the full-scale civil aircraft at −40 ℃ engine low temperature startup was successfully carried out. The experiment result showed that: the aircraft cold soak time continued 10 h and the experimental temperature fluctuated within ±3 ℃ during the whole experiment process; compared with normal temperature, the engine starting function and performance had no obvious degradation. The success of this experiment has provided a practical basis and technical reserve for other full-scale civil aircraft to carry out engine cold start experiment in the laboratory and formulate relevant airworthiness standards and specifications.