IMPLEMENTATION OF SIMILARITY PRINCIPLE AND SCALING LAWS FOR LOW-TOHIGH SPEED MIXED FLOW COMPRESSOR

In this paper, the use of the similarity principle has been presented to extrapolate the performance and results for mixed flow compressors application in a small jet or turbofan engines. The similarity principle helps in scaling a single-stage mixed flow compressor model tested at variable operating conditions to different multistage compressors operating to varying conditions through scaling the non-dimensional compressor characteristics. To implement the similarity principle, performance governing parameters were selected and scaling laws were derived, which gives us a degree of freedom for extrapolation of mixed flow compressors. The compressor has been scaled to new specifications using the (n(s)-pi) specific speed- total pressure ratio plot, along the best-efficiency line of the baseline compressor. In this paper, a distinctive approach is taken for validating the scaling laws; the input and output for the scaling laws are target performance (n(s)-pi values) and scaling factors, respectively. The practical use of the scaling laws has been demonstrated by scaling a high-speed mixed flow compressor (maximum total pressure ratio, pi(max) =4.55) to new required specifications (pi max =1.03), and examining the conditions under which these laws are applicable. The formulated approach developed for extrapolation of the results from low-to-high speed mixed flow compressors has been justified and tested by comparing the computational results. The impact of dimensions those are not considered (tip gap and splitter blades) for scaling law formulations on flow field distribution is computationally analyzed.