Abstract
Organic Rankine cycle (ORC) is a reliable technology to recover low-grade heat sources. The radial-inflow turbine is a critical component, which has a significant influence on the overall efficiency of ORC system. This study investigates the effects of the blade installation angle and blade number on the flow performance of radial-inflow turbine stator. R245fa and toluene were selected as the working fluids in the low and high temperature range, respectively. Two-dimensional stator blades model for the two working fluids were established, and numerical simulation was conducted through Computational Fluid Dynamics (CFD) software. The results show that for low temperature working fluid R245fa, when the installation angle is 32° and blade number is 22, the distribution of static pressure along the stator blade has no obvious pressure fluctuation, and the flow loss is least. Meanwhile, the stator blade obtained the optimal performance. For high temperature working fluid toluene, when the installation angle is 28° and blade number is 32, the average outlet temperature is the lowest, while the average outlet velocity is the largest. The flow state is well and smooth, and the remarkable flow separation and shock wave are not present. Moreover, the stator blade for R245fa has a larger chord length, cascade inlet diameter, and cascade outside diameter but a lower blade number compared to toluene.
Highlights
Due to massive consumption of primary energy, the problems of energy shortage and environmental deterioration are prominent
The blade installation angle of the stator could affect the absolute velocity angle at the rotor inlet, which has a significant influence on the velocity triangles and stator velocity coefficient
This work investigates the effects of the blade installation angle and blade number on the performance of radial-inflow turbine stator
Summary
Due to massive consumption of primary energy, the problems of energy shortage and environmental deterioration are prominent. The recovery of low-grade heat sources such as solar energy, geothermal energy, biomass energy, and low temperature waste heat is imperative [1,2,3]. Organic Rankine cycle (ORC) has proven to be a viable alternative to convert low-grade heat source into electricity [4,5]. It has advantages of high reliability, small size, and low capital cost since it has the same configuration as conventional steam Rankine cycle [6]. A higher inlet pressure of the turbine can be obtained even for the low temperature heat sources [7]. The thermal efficiency of the ORC system is at a relatively low level due to the low operating temperature
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