Waste heat recovery using Organic Rankine cycle (ORC) systems has been regarded as the most potential technology for diesel engine fuel economy improvement. The compactness of ORC system is very important, so reducing the total volume of heat exchangers of the ORC system is the main challenge for ORC applications in truck engines. This paper proposes a new ORC system for waste heat recovery of truck diesel engines. The ORC system uses the hot compressed intake air and the exhaust gas as heat sources. The conventional air intercooler is substituted with the pre-heater of the ORC system. Hence the condenser of the ORC system can be installed at the original place of the intercooler, which could make the system integration much easier. A one-dimension simulation model of the combined diesel engine and ORC power system is set up. In combined ORC-engine system the output power of turbine is combined with the output power of crack shaft at a specific gear ratio to increase effective power of the engine system. The combined ORC-engine system performance is analyzed at common operating conditions and compared with the original engine. Results show that the combined system thermal efficiency is increased by 8.38% and the brake special fuel consumption (BSFC) reduces by 7.82% at peak. In design point, net output power of ORC system is 28.72kW, which increases thermal efficiency by 9.31% and reduces BSFC from 199.76 g/(kW·h) to 182.76 g/(kW·h). In addition, the cost of ORC system is estimated, and Payback time is 4.92 years.

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