Experimental study on operating parameters matching characteristic of the organic Rankine cycle for engine waste heat recovery

Abstract

The organic Rankine cycle (ORC) is a promising engine waste heat recovery (WHR) technology. However, with a change in the engine operating conditions, the choice of ORC-WHR system operating parameters have great influence on system performance. Therefore, this study investigated the changing law of ORC-WHR system operating parameters optimal value and the sensitivity of the system to the operating parameters under eight different engine operating conditions. That is, the research on operating parameters matching characteristic. The two key operating parameters selected were expander speed (Sexp_shaft) and superheat degree (SD). The performance indexes of the system included expander shaft efficiency (ηexp_shaft), thermal efficiency (ηth), evaporator heat exchange (Qeva), expander output work (Wexp_shaft), pump work consumption (Wpump), and net power output (Wnet). The results showed that Sexp_shaft was the most significant parameter affecting the system performance. As engine load increased from 1000 rpm, 300 Nm to 1350 rpm, 650 Nm, the best Sexp_shaft of Wnet increased from 1200 to 1600 rpm. As the engine load increased, the sensitivity of the system to Sexp_shaft and SD gradually decreased. The influence of the Sexp_shaft on Wnet decreased from 90.28% to 7.78%. The effect of the SD on the Qeva decreased from 11.26% to 5.16%.