关键词: 桨扇发动机, 全环形进气道, 对转桨扇, 进气道性能, 滑流

Abstract:

A study was conducted on the aerodynamic interference effects of Contra-Rotating Propfan （CRP） and propfan engine inlet. Unsteady numerical calculation was carried out by the sliding grid method， and the coupled aerodynamic effects of the 8X8 CRP and inlet were compared and analyzed under two typical operating conditions： the high-altitude cruising state and ground takeoff state. The mechanism and quantitative results of slipstream effects on inlet under different conditions， and differences of CRP aerodynamic performance before and after coupled inlet were summarized. Results indicate that the hub vortex produced by the CRP is the primary factor influencing the flow characteristics within the intake duct. Under the cruise condition， wake vortices of the rear row dominated the vortex structure of the inlet and cause non-uniform flowfield. Under the takeoff condition， the coupling of wake vortices of both front and rear rows was enhanced， leading to the presence of vortices in pairs. These paired vortices collectively impacted the flow field within the inlet. The periodic movement of wake vortices within the inlet induced periodic fluctuations in aerodynamic parameters. When propfan wake vortices dominated the vortex structure， the amplitude of parameter oscillations diminished along the duct， yet the oscillation frequency remained constant and the phase angle maintained a uniform lag. Following the detachment of wall-separated vortices， the duct’s vortex structure underwent changes， disrupting the amplitude， frequency， and phase angle of parameter oscillations due to the mixing of these separated vortices. The slipstream enhanced the total pressure of inlet； however， intricate trailing vortices significantly exacerbated the total pressure and swirl distortions at the duct's exit， leading to pronounced uneven internal flow distributions. Internal flow losses increased by 2.85 times during cruising and 1.09 times during takeoff. In addition， integration of the intake duct altered the internal flow field structure of the rear blade channel of the counter-rotating propfan. This results in a decrease in velocity within the channel， a forward shift in the position of the shock wave on the blade suction surface， and a modification of the operational characteristics of blade elements at varying heights. Consequently， this improved the thrust performance of the propeller fan. Under the design condition， the thrust coefficient of the front row blades rose by 5.9%， that of the rear row blades increased by 27%， and the overall efficiency of the propfan improved by 5.2%.

Key words: propfan engine, annular inlet, Contra-Rotating Propfan (CRP), inlet performance, slipstream