Numerical Investigation into Characteristics of WIPCC and Distortion of S-shaped Intake

Abstract

Water injection pre-compressor cooling technology can efficiently increase the engine thrust and expand the flight envelope of the aircraft. Changes in the curvature of the intake and the evaporative cooling of the spray medium naturally distort the total pressure, total temperature, and characteristics of the swirl of the flow before it enters the engine. This study conducts numerical research on the aerothermal process of the WIPCC in an S-shaped intake using the Eulerian-Lagrangian method. The spatial evolution of critical variables along the flow direction and specific cross-sections were obtained by analyzing the statistical time-averaged results of multiphase flow. The transient distortion descriptors were quantified and analyzed following the SAE standard, which revealed the characteristics of various distortions and their spatial-temporal changes. Furthermore, the variables reflecting the transient flow structure were decomposed using the POD method to obtain the coherent structure of each mode and its frequency and energy characteristics. The results showed that aerodynamic breakup was the main cause of droplet size reduction and led to a decrease of 74.4% and 63.8% in Sauter droplet size under two conditions, respectively. The downstream mixing of flows in the S-duct mitigated the distortions caused by the intake's changing curvature and droplet evaporation. After the mixing of flows under specific conditions, the total pressure distortion coefficient decreased from 0.30 to 0.12, the swirl intensity decreased from 4°-6° to 2°-4°, and the high total temperature extent decreased from 0.65 to 0.35. The POD mode of the variables exhibited broadband characteristics with multiple spikes and energy dispersion. The main modes of the drop coefficients in total pressure and temperature corresponded to large- and small-scale structures, respectively, with Strouhal number ranges of 0.079-0.394 and 0.362-1.260. These results reveal the effects of WIPCC on the aerothermal processes in the S-shaped intake and the mechanism of generation and evolution of distortions. Moreover, the results provide reasonable boundary conditions for numerical investigations of wet compression under intake distortions.