A study of regulated and green house gas emissions from a prototype heavy-duty compressed natural gas engine under transient and real life conditions

A newly designed Compressed Natural Gas prototype engine was benchmarked against its parent Euro V compliant engine in terms of gaseous emissions and with particular view on regulated and Green House Gas emissions. The main technological innovation included a new cylinder head equipped with a Variable Valve Actuator system designed to increase the efficiency compared to the reference throttled engine. The objective of the study was to examine the effect of this system on the operation of the prototype engine. Engine stand-alone tests represented the first step of this analysis. Afterwards, both engines were installed on the same truck and tested under different operating conditions. Vehicle tests included measurements on a chassis dynamometer as well as on-road with the aim of verifying real world emissions. CO2 emissions and Brake Specific Fuel Consumption of the prototype were lower compared to the reference engine, with this phenomenon being more pronounced on-road. Furthermore, reduced NOx and CO emissions were observed under all operating conditions. On the other hand, the introduction of the prototype engine had a negative effect on CH4 emissions. Despite that the prototype was initially designed to fulfill the EURO V standards, no pollutant exceeded the EURO VI limits over homologation cycles. (C) 2016 The Authors. Published by Elsevier Ltd.