Abstract: Choking technique is an available way to reduce altitude test cost and respond insufficient capacity of the pumping equipments. Under the conditions of various exhaust ambient pressure， four group experiments of a turbofan engine with Laval nozzle were performed to identify the effect of choking on engine thrust. The maximum difference of test total thrust in these experiments was up to 6.2%. In order to find the reason of thrust difference and promote the accuracy of estimating engine thrust obtained in altitude test under choking condition， relative theory and calculation analysis were studied， then the estimation method of changes caused by mean influence factors was developed. The results revealed that the main influence factors of test total thrust included engine speed，correction method and flow behavior in nozzle expansion section. According to estimation method presented， the total thrust changes caused by these factors were evaluated. The maximum difference decreased to 0.8% after eliminating these changes. At the same engine speed， the referred total thrust increased with the raise of the exhaust ambient pressure and the maximum difference was 3.3%.

Key words: Choking technique;Thrust;Engine;Altitude test;Laval nozzle

摘要： 堵塞技术是降低发动机高空模拟试验成本和解决设备抽气能力不足的可行手段。在不同喷管排气环境压力条件下，某型带拉瓦尔喷管涡扇发动机完成了四组堵塞对推力影响的试验，发动机总推力试验值最大差异为6.2%。为揭示试验推力差异产生的原因，提高堵塞条件下发动机高空试验推力评估的准确性，开展了相关的理论分析和一维仿真计算，提出了主要影响量估算方法。结果表明：推力差异主要与发动机转速、结果修正方法和喷管扩张段流场特性有关；按文中提出的主要影响量估算方法计算了这些因素对推力的影响量，扣除影响量后总推力的最大差异降至0.8%；相同转速下，总推力相似换算值随喷管排气压力的升高呈增大趋势，最大差异达到3.3%。

关键词: 堵塞技术;推力;发动机;高空试验;拉瓦尔喷管