A Brayton cycle waste heat recovery (WHR) system for turbocharged diesel engines was described and the performance of a diesel engine integrated with this system was investigated. The waste heat recovery system is integrated with the turbocharging system of the diesel engine, with the turbocharger compressor working as the Brayton cycle compressor simultaneously.
The combined cycle of diesel cycle and Brayton cycle was simulated using the engine cycle simulation code GT-Suite 7.0, and the performance of the Brayton cycle WHR engine was investigated. The turbocharging turbine and the Brayton cycle turbine were designed and their performances were simulated with turbine through-flow model. The mass-flow rates of the diesel cycle and the Brayton cycle have a great influence on their power outputs, which are determined by the turbocharger performance greatly. The influence of the charging turbine geometric parameters on the performance of the Brayton cycle WHR system was discussed. Results show that there is a tradeoff in performance between high and low engine-speed operating conditions with the investigated parameters variation, and different geometric dimensions should be selected when different common operating conditions are considered.