Abstract
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•ORC as a waste heat recovery technology in heavy duty diesel engine is studied.•Various types of organic fluids are investigated in two regions in the t-s diagram.•In superheated region, wet fluids present best powertrain and turbine performance.•Near saturated vapor curve, isentropic fluids present best system performance.•Engine power and BSFC are substantially improved after installing the ORC system.
This paper outlines a comparative assessment of the effects of various fluid types on the performance of powertrain performance (i.e. heavy-duty diesel engine + organic Rankine cycle) and the design of the radial inflow turbine. The considered organic fluids are R123 (dry), R21 (wet) and R141b (isentropic). The exhaust gas of a 7.25ℓ heavy duty diesel engine is utilized as the system heat source. The powertrain system, including the radial inflow turbine, is analyzed under superheated conditions and near saturated vapor curve, at various operating conditions. Surprisingly, wet fluids offer attractive cycle performance in the superheated region (12.65% on average) followed by isentropic fluids (12% on average). Near the saturated vapor curve, isentropic fluids are found to present best cycle performance (13.77% on average) while wet fluids offer the lowest (10.90% on average). However, wet fluids present a compact turbine design and best isentropic efficiency with an average value of 82% in the superheated region. Near the saturated vapor curve, isentropic and dry fluids offer relatively lower turbine efficiencies (80.9% and 80.3 on average) while wet fluids result in two-phase condition at the turbine exit which results in poor turbine performance (63.30% on average). Moreover, R141b shows best improvements of engine power and BSFC with values of 11.18% and 10%, respectively, at 1 kg/s. Compared to R123 and R141b, R21 improved the engine power and BSFC by at least 7.86% and 7.63% under superheated conditions.