Design And Investigation On Interaction Between Geometry And Performance Of Supercritical Carbon Dioxide Radial Inflow Turbine's Inlet Volute

The Supercritical carbon dioxide(SCO2)Brayton cycle is environmentally friendly andefficient,and its structure is compact.It is of great significance to the development of the national economy,so it has been widely concerned by scholars at home and abroad.The radial inflow turbine(RIT)is the core component of the new cycle.As the first circulation component of the working fluid entering the RIT,the design of the inlet volute affect the performance of the whole machine.In addition,compared with the RIT with the vaned stator,the vaneless volute RIT can significantly reduce the size of the radial dimension,and thus broaden its application area.Therefore,it is of great significance to study the aerodynamic design and investigation on interaction between geometry and performance of the inlet volute.In this paper,based on the numerical simulation results of the SCO2 RIT with the vaned stator,the geometry of the inlet volute is adjusted by summarizing the influence law of volute shape,and finally the vaneless inlet volute matching the target impeller is obtained.The details are as follows:Based on the one-dimensional design method,the design of the inlet volute of the SCO2 RIT with the vaned stator is completed and the numerical simulation of the whole RIT is carried out.Then,the preliminary design of the vaneless inlet volute is checked with reference to the simulation results of the impeller inlet of the RIT with vaned stator.The results show that the inlet volute matches well with the nozzle and the impeller.And the matching performance between the preliminary design of the vaneless inlet volute model and the target impeller needs further study and improvement.Based on the preliminary design of the vaneless inlet volute,the interaction between geometry(different throat areas and profile distributions)and performance of the vaneless inlet volute is studied.Under the same profile distribution,the total pressure loss coefficient and the outlet average flow angle of the volute decreases with the volute throat area increasing.The volute throat area has little effect on the circumferential distribution trend of the outlet flow angle.With the same volute throat area and the profile distribution changes from concave to convex,the total pressure loss coefficient of the volute increases,the outlet average flow angle increases first and then decreases.The vaneless inlet volute with small-scale convex profile has a relatively uniform outlet flow angle distribution.Based on a circular cross-section vaneless inlet volute with good initial matching,the interaction between different cross-section shape and performance of the SCO2 vaneless volute RIT is studied.The results show that the total pressure loss coefficient decreases with edge length ratio(F)increases of the inverted pear cross-section vaneless inlet volute,and the efficiency of the corresponding SCO2 vaneless volute RIT increases until F = 1,then it remains basically unchanged.The total-total efficiency of the SCO2 vaneless volute RIT with the inverted pear cross-section volute is higher than that with circular cross-section volute,but the maximum increase is 0.88%.Combined with actual processing difficulty,it has better economy and engineering practicability to select the circular cross-section vaneless inlet volute for the SCO2 vaneless volute RIT involved in this paper.By summarizing the interaction law between geometry and performance,the final design scheme of the vaneless inlet volute model with good comprehensive performance matching the target impeller is determined,which is analyzed with the impeller full channel model under off-design operating conditions.The total-total efficiency of the full channel simulation of the SCO2 vaneless volute RIT is 85.68%,which meets the design requirements.Compared with the SCO2 RIT with vaned stator,the radial dimension of the SCO2 vaneless volute RIT is reduced by 33.55% at the maximum radius.And its efficiency curve under off-design operating conditions is more gentle than that of the SCO2 RIT with vaned stator.The range of maintaining high efficiency near the design point is also slightly increased.Finally,a vaneless inlet volute with smaller size and better matching with the target impeller is designed.