Numerical Study On Flowfield Of Partial-admission Radial-inflow Turbine

Distributed energy system has been more and more important in energy marketdue to its energy saving and high efficiency. In some foreign countries, the CCHPsystem which takes the microturbines as the core has developed rapidly. In China,both the increasingly powerful national defense and the rising living requirementshave created a large market for the development of microturbine technology. Whilethe radial-inflow turbine is the key of the microturbine and its performance directlydetermines the level of the microturbine technology.This paper has studied the microturbine of a CCHP system and carried out theaerodynamic design of a large expansion ratio,low flow rate, high efficiency radial-inflow turbine. One dimensional Fortran program and CFturbo software have beenemployed to calculate and complete the aerodynamic design respectively，as wellas the CFX software has been used for numerical simulation and validation. Thedifferent pitch positions of rotor blades have been analyzed and it offers anoptimum match of stators and blades in the designed partial-admission radialturbine. Besides，this article has studied the turbine performance under differentintake sector positions，partial-admission degree and variable working conditions.The results show that the efficiency of the partial-admission radial-inflowturbine designed in this paper is77.29%, which has met the requirements of thissubject. As a result of changing the pitch positions of blades, the maximumefficiency has a1.52percentage points higher than the minimum. During thepartial-admission radial turbine working process, the rotors experiences intake andnon-intake sectors periodically, which leads to an obvious circumferential pressuregradient at the impeller inlet but uniform outlet pressure distribution. With theincrease of partial admission, the massflow and output power of this turbine hasincreased linearly. The existence of tip clearance flow causes a more complex flowfield while the leakage vortices in each intake passage have a differentdevelopment process. The efficiency and output power decreased when the tipclearance grows higher. With the increase of the expansion ratio, the massflow andpower increased linearly and the highest efficiency appears at the optimumexpansion ratio, which is getting closer to a higher value. Moreover, the turbineefficiency has kept higher than70%over the entire range of expansion ratio atdesigning speed.