基于有机朗肯循环的固定式天然气发动机排气余热回收系统性能分析

摘要

An organic Rankine cycle (ORC) system with an internal heat exchanger (IHE) is designed to recover exhaust energy from a stationary compressed natural gas (CNG) engine. According to the ifrst and second laws of thermodynamics, the performances of the ORC system are analyzed. Thereafter, the stationary CNG engine-ORC with IHE combined system is presented. The electric efifciency and the brake speciifc fuel consumption (BSFC) are chosen to evaluate the operating performances of the combined system. The results show that, when the evaporation pressure is 3.5 MPa and the engine is operating at the rated condition, the net power output and the thermal efifciency of ORC system with IHE can reach up to 62.7kW and 12.5%, respectively. Compared with the stationary CNG engine, the electric efifciency of the combined system can be increased by 6.0%, while the BSFC can be reduced by a maximum 5.0%.%针对一台固定式天然气发动机的排气能量变化规律，设计了带回热器的有机朗肯循环排气余热回收系统。基于热力学第一定律和第二定律，对固定式天然气发动机排气余热回收系统性能指标进行了理论计算和分析，进而构建了固定式天然气发动机-带回热器有机朗肯循环联合系统，并采用发电效率和有效燃料消耗率评价联合系统的性能。研究结果表明：当蒸发压力为3.5 MPa，发动机运行在额定工况点时，带回热器有机朗肯循环系统最大净输出功率和热效率分别为62.7 kW和12.5%；与固定式天然气发动机相比，联合系统发电效率最大可提高6.0%，有效燃料消耗率最大可降低5%。