Heavy-duty vehicle diesel engine efficiency evaluation and energy audit

A main input for vehicle efficiency simulation tools is a fuel consumption map that characterizes the efficiency of the engine at its various operational points. This work provides a complete engine fueling map characterization of modern diesel engines for heavy-duty vehicles. The analysis also includes a detailed breakdown of engine energy loads and losses, as well as estimates of technical efficiency potential for future engines. This engine, in turn, is utilized in the ICCT’s tractor-trailer simulation modeling.

The project’s approach involved laboratory engine testing and analysis of heavy-duty and medium-duty diesel engines that are compliant with the 2010 U.S. Environmental Protection Agency (US EPA) emissions standards. In addition, data from industry colleagues and from the research literature were utilized to understand the change in energy flows and losses due to various efficiency technologies. Two primary outputs from this study were the characterization of the engines’ fuel consumption maps, and detailed energy audit analyses across varying engine speed-load conditions.

The research also points to many areas where there is the potential for heavy-duty diesel engine efficiency improvements. The findings indicate that, over regulatory test cycles, diesel engines have the potential for substantially increased efficiency. The potential efficiency technologies include increased compression ratio and peak in-cylinder pressures, reduced pumping losses through low-pressure drop aftertreatment systems, exhaust gas recirculation improvements, improved turbocharging technology, advanced lubricants to reduce frictional parasitic losses, engine material coatings that lower friction, and variable speed water and oil pumps. The work indicates how, from tested 2011 and 2013 engines, fuel consumption could be reduced by 8-10% to meet 2017 standards, and by 18-20% in advanced engines in the 2020-and-later timeframe. Finally, the simulation of a waste heat recovery system shows further efficiency improvements.