&nbsp;Engine Waste Heat Recovery (WHR) technologies convert the exhaust waste heat to useful power resulting in lower fuel consumption and pollutant emissions. Compared to other technologies, Organic Rankine Cycle (ORC) systems are considered as the most promising technology for engine waste heat recovery applications due to their comparatively higher maturity, relative technological simplicity, lower cost and small back pressure impact on engine performance and fuel consumption.ORC systems used in engine waste heat recovery applications are generally medium-sized ORC power systems, of the range of tens to hundreds of kilowatts that employ radial inflow turbines for expansion. The design of turbines, which is the most critical component in the Organic Rankine Cycle is quite involved due to the molecularly complex and high dense characteristics of ORC fluids. Moreover, as the single-stage high-pressure radial turbines are generally operated close to the critical point of the working fluids, they will exhibit complex flow characteristics like shock waves.Although different approaches for ORC turbines have been reported in the literature, a substantial advancement in small scale ORC turbine design is necessary for its design and manufacture in large volumes in view of the importance of expander efficiency to the commercial viability of ORC systems in various applications. Also, as a wide range of fluids are employed for ORC applications there is a&nbsp; need for selection of appropriate blade profiles that incorporates the complex fluid behaviour of organic fluids.The present paper investigates the selection of suitable nozzle and turbine wheel blade profiles for a 30 kW ORC system for a stationary diesel engine. Novec649 an engineered fluid is chosen as the working fluid as it exhibits near-zero GWP (global warming potential) and is non-flammable. 3D Computational Fluid Dynamic analysis of the turbine was performed using commercially available Ansys CFX software for the different nozzle and turbine wheel blade profiles to analyse the effect of blade profile on the turbine flow field. The analysis involved the identification of various sources of inefficiency and the geometric parameters that affect these losses.The stator profiles used are mostly simple geometrical constructions with the diverging section of the nozzle developed following the method of characteristics (MoC). The turbine wheel design is based on Hasselgruber’s blade design technique proposed by Balje.&nbsp; The paper opens avenues to the possibility of improving the blade profiles for small scale ORC turbines for efficient turbine performance and also to simplify the blade profile generation technique of ORC turbines.

Design of Supersonic Nozzles for Organic Rankine Cycle (Orc) Based Waste Heat Recovery Systems

Paper Proceedings: https://asmedigitalcollection.asme.org/GTINDIA/GTINDIA2021/volume/85536

ASME 2021 Gas Turbine India Conference (GTINDIA2021)

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