Structure And Performance Research On Ram-rotor And Scrampressor

Based on shock wave compression technology, the ram-rotor is a new compression system which uses the design of supersonic aircraft intake, the conventional axial-and centrifugal-flow compressor for reference. This kind of shock wave compression system has high pressure ratio, potential high efficiency, simple structure, light weight and less rotating parts. Over the past decade, it has much commercioganic to energy, power, transportation departments and researchers. Among numerous devices of distribution energy system which the core technology is the distribution electrical sources, the small gas turbines with low emission have the most commercial competitiveness, especially for the electrical industries which are changing towards the combination of large-scale power plant and mini type distribution power generation. The ram-rotor based on shock wave compression technology is one of research emphases of low emission small gas turbine. Research on this new efficient compression system has the important theoretical significance and practical application value. Some domestic scientific research institutions have developed relative study on ram-rotor, however, there still have a lot of works should be deeply developed.Firstly, the main factors affecting the ram-rotor performance are analyzed by theoretical methods in this paper. Secondly, basing on the theoretical analysis, many kinds of geometrical parameters are considered; CAD and FLUENT software are adopted to design the three-dimentional flow-path and simulate numerically the flow field of the ram-rotor and the Scrampressor; and the cases with best integrated performance are obtained. Furthermore, three-dimentional numerical simulation is adopted to study the flow field and the performance of two best cases at design point and off-design points. Systematic and comprehensive research data on the ram-rotor and the scrampressor are obtained which would establish a firm foundation for the further experimental study and practical application.For ram-rotor, the strake wall section with the positive trapezoid shape is better than that with the reversed trapezoid shape. Large or small throat length-height ratio can lead the adiabatic efficiency and the total pressure ratio decrease. The compression ramp angle and the subsonic divergent angle have no significant effect on the performance of the ram-rotor. Large strake straggle angle decreases the average flow angle at exit, the total pressure recovery coefficient and the total pressure ratio. The adiabatic efficiency is lower with larger or smaller strake straggle angle. Lower throat contract ratio can remarkably improve the adiabatic efficiency, the total pressure recovery coefficient, the total pressure ratio and the average flow angle at exit. With the decreasing of the exit-inlet area ratio, the average flow angle at exit, the total pressure ratio and the static pressure ratio decrease; but the adiabatic efficiency and the total pressure recovery coefficient increase. With the increasing of the relative Mach number, the average Mach number, the total pressure ratio and the static pressure ratio have an enhancive trend, and the adiabatic efficiency is the contrary. The three-dimensional effect is strong on the flow field and the main reasons of flow loss are caused by the shock wave loss, the interaction between the shock wave and boundary layer, and the boundary layer separation loss. All performance parameters do not change monotonously, so the reasonable compromises should be made among the adiabatic efficiency, the total pressure ratio, the static pressure ratio, the total pressure recovery coefficient, the average flow angle at exit, the width of the ram-rotor, the flow mass, and so on. For the ram-rotor with the diffuser, the case F1 has the highest total pressure ratio (12.2) and the case F1-2 has the best integrated performance.For the Scrampressor, the total pressure ratio, the static pressure ratio, the adiabatic efficiency and the total pressure recovery coefficient have the ascending trend with the decreasing of the throat contract ratio. The larger strake straggle angle increases the adiabatic efficiency and the total pressure recovery coefficient, decreases the average flow angle at exit, the total pressure ratio and the static pressure ratio. Shock wave loss and kinetic energy loss caused by the lower energy flow in the boundary layer are the main reasons of the entropy increasing before the throat exit. The final curve shock wave loss, the mixing loss between the low energy flow in the boundary larye and the main flow, the lateral migration of the low energy flow are the main reasons of the entropy increasing after the throat exit. For the scrampressor without the diffuser, the case N3 has the highest adiabatic efficiency (85.18%) and total pressure recovery coefficient (87.81%), and the case has the best integrated performance.The major difference between the ram-rotor and the scrampressor is the latter without the diffuser which causes the seperatioanal zone and the distinctness of performance at exit. Under the same throat contract ratio or strake straggle angle, the scrampressor has the higher adiabatic efficiency and the lower total pressure ratio than the ram-rotor. Therefore, scrampressor would be a good choice with smaller throat contract ratio and somewhat larger strake straggle angle when high adiabatic efficiency is needed.The back pressure almost does not affect the flow field before the throat exit. With the increasing of the back pressure, the position of flow separation zone moves towards the inlet; the total pressure ratio and the average flow angle at exit increase; the adiabatic efficiency of the ram-rotor decreases firstly and then increases, and that of the scrampressor increases firstly and then decreases. Under the same back pressure, the ram-rotor has the higher total pressure ratio and the average flow angle, but the scrampressor has the higher adiabatic efficiency.The rotational speed can significantly change the shock wave structure. With the increasing of the rotational speed, the shock wave will move towards the exit. Under the same rotational speed, the scrampressor is superior to the ram-rotor at a certain extent, such as the adiabatic efficiency, the total pressure recovery coefficient.The characteristic curves of the ram-rotor and the scrampressor are perpendicular to the abscissa axis, namely, the flow mass can be affected only by the rotational speed. The highest total pressure ratio increases with the increasing of the rotational speed. The compression ability of the scrampressor is weaker than the ram-rotor, and the total trend of the adiabatic efficiency is degressive. At the lower rotational speed, the ram-rotor could enter into the unsteady state easily, but the stability margin of the scrampressor changes mildly and keeps a good working status.