Model-scale test of jet installation noise for aircraft turbofan engines

The noise characteristic of an isolated turbofan engine changes when it is installed to an airframe, typically to a wing part. So it is necessary to investigate the change in noise characteristic due to installation, which will lead to accurate prediction of overall aircraft noise. To estimate the installation effect on jet noise generated by turbofan engines of high bypass ratios (BPR), the noise team at Beijing Aeronautical Science and Technology Research Institute (BASTRI) of Commercial Aircraft Corporation of China, Ltd. (COMAC) has performed a series of tests, which consists of two phases. The first phase of the tests was carried out at the anechoic chamber at Beihang University (BUAA) in Beijing, China. During the test, dual nozzles of two different area ratios (secondary to primary), 5 and 7, and a simplified wing part in model-scale were tested to obtain a comprehensive database for the analysis of isolated as well as installed engine jet noise. The spectral characteristics are investigated and the effects of the following parametric variations are reported in this paper: (1) impact of area ratio with fixed, but over a range of, nozzle operating conditions; (2) at a given area ratio, systematically varying primary and secondary conditions; and (3) impact of installation on noise for various engine positions relative to a simplified wing model and various flap angles. The result shows consistent and reasonable trends for various nozzle operating conditions and installation effect on noise for both area ratios. The acquisition and analysis of the test data are expected to contribute to predict the engine installation noise of next generation aircraft that will be powered by high BPR turbofan engines.