Analysis of the Fan Performance in the Turbofan Engine Test

The fan was tested in the whole turbofan engine test condition, and the post-processing of the test data was based on confidence intervals. Through the analysis of distribution characteristics of data, the indirect measurement parameters such as mass flow rate and pressure ratio, which are affected by multiple factors, all obey the normal distribution. Based on the distribution characteristics, a statistic can be constructed to calculate the confidence intervals for these parameters. It is known that the more data, the smaller the confidence interval of the parameters. As a result, it is found that the range of confidence intervals obtained from the final test data is so narrow that point estimates could be used instead of interval estimates. Comparing the test results with the numerical calculation results, the test results are in good agreement with the calculated performance curves. The processed test results show that as the area of bypass(core) throat area decreases, the fan working line will move to the the direction of reduced flow rate. However, that is not absolute. If the area is beyond a certain range of the area, the working line may move in the opposite direction. The effect of throat area variation on the performance of the fan may be related to flow state of the core and bypass. Therefore, multiple adjustments are required to match the design point.