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The supercritical CO2 power cycle system for waste heat recovery (WHR) of internal combustion engine (ICE) has widely been concerned as a research hotspot. And the expander is a key component in the supercritical CO2 power system. Rolling rotor expander has the following advantages: compact size, light weight, less moving parts, high stability and long service life, which qualify it a very suitable choice for engine’s waste heat recovery system. For a self-designed rolling rotor expander using supercritical CO2 as its working fluid, FLUENT software was used to simulate its internal flow field in this study, obtaining the changes of the internal pressure field and turbulent kinetic energy. The causes of local vortex in the expansion process were analyzed. Under different working conditions of the expander, the change of internal pressure and the distribution of P-V curve were observed, and the work capacity under different inlet pressure was analyzed.

This paper presents a model system TEG-DORC that employs thermoelectric generator (TEG) as a topping cycle integrated with a dual-loop organic Rankine bottoming cycle (DORC) to recover exhaust heat of internal combustion engine (ICE). The thermodynamic performance of TEG-DORC system is analyzed based on the first and second law of thermodynamics when system net output power Wnet, thermal efficiency ηth, exergy efficiency ηe and volumetric expansion ratio are chosen as objective functions. The model has many parameters that affect combined system performance such as TEG scale, evaporation pressure of high temperature ORC loop (HT loop) Pevp,HT, condensation temperature of HT loop Tcond,HT. It is suggested that HT loop has a vital influence on system performance.

A novel combined power and cooling cycle based on the Organic Rankine Cycle (ORC) and the Compression Refrigeration Cycle (CRC) is proposed. The cycle can be driven by the exhaust heat from a diesel engine. In this combined cycle, ORC will translate the exhaust heat into power, and drive the compressor of CRC. The prime advantage of the combined cycle is that both the ORC and CRC are trans-critical cycles, and using CO₂ as working fluid. Natural, cheap, environmentally friendly, nontoxic and good heat transfer properties are some advantages of CO₂ as working fluid. In this paper, besides the basic combined cycle (ORC-CRC), another three novel cycles: ORC-CRC with an expander (ORC-CRCE), ORC with an internal heat exchanger as heat accumulator combined with CRC (ORCI-CRC), ORCI-CRCE, are analyzed and compared.

A bottoming waste-heat-recovery (WHR) model based on the Organic Rankine Cycle (ORC) is proposed to recover waste heat from exhaust gas and jacket water of a typical diesel engine (DE). The ORC model is detailed built based upon real structural and functional parameters of each component, and is able to precisely reflect the working process of the experimental ORC system constructed in lab. The DE is firstly tested to reveal its energy balance and the features of waste heat. The bottoming ORC is then simulated based on experimental data from the DE bench test using R245fa and R601a as working fluid. Thermodynamic evaluations are done on key parameters like waste heat recovered, expansion power, pump power loss and system efficiency. Results indicate that maximum expansion power and efficiency of the ORC are up to 18.8kW and 9.6%. Influences of engine condition, fluid mass flow and evaporating pressure on system performance are analyzed and meaningful regularities are revealed.

The combined thermo-generator and organic rankine cycle (TEG-ORC) used in exhaust heat recovery of internal combustion engine (ICE) is analyzed theoretically. Only about one third of the total energy released from fuel combustion is converted into useful work in engines, while the remaining energy goes into ambient environment, among which exhaust gas possesses high-grade thermal energy. Most of previous studies on energy recovery from engines have focused on exhaust heat recovery by ORC. However, if the heat is exchanged directly with high-temperature exhaust gas, organic working fluid would resolve with its lower decomposition temperature, and this is extremely harmful to ORC system. To avoid this phenomenon and utilize waste heat, preliminary thermoelectric modules are used to lower exhaust temperature and to generate electricity simultaneously.