Experimental study on the effects of exhaust heat recovery system (EHRS) on vehicle fuel economy and emissions under cold start new European driving cycle (NEDC)

Abstract

Over the decades, unremitting efforts have been made to achieve energy conservation and emission reduction throughout the world. While for a vehicle engine, a great deal of the fuel energy is wasted as exhaust heat. Based on a novel exhaust heat recovery system devised and modified on a vehicle exhaust channel, the chief objective of this study is to improve the vehicle economy and emissions under cold start. Therefore, a detailed experimental investigation was conducted on the chassis dynamometer (CD) under cold start NEDC at 25 °C and −7 °C temperatures. And the method of comparative analyses of the coolant temperature, gasoline fuel consumption and exhaust emissions including total hydrocarbon (THC), carbon monoxide (CO) and nitrogen oxide (NOX) have been obtained to reveal the effects of EHRS on vehicle economy and emissions under cold start. The results show that, since the coolant temperature can be quickly increased with EHRS to shorten engine warm-up time under cold start, vehicle economy is enhanced during NEDC. Moreover, the device of EHRS can effectively alleviate the combustion deterioration and wall frame quenching effect in the cylinders under cold start, which greatly decreases THC emission. Although the excess air coefficient cannot be changed by EHRS, it can improve the combustion environment in cylinders, which contributes to the reduction of CO emission. It is unexpected to find that NOX emission is also decreased with EHRS actuation, which can be explained by a new theory called Fenimore mechanism. All these aims to provide helpful preliminary work for vehicles to meet the upcoming stringent limit of the real driving emission (RDE) of CHINA 6.