Westport Innovations Inc. has completed an engineering program with Daimler AG to develop and to assess the Westport High Pressure Direct Injection (HPDI) system for a Daimler heavy duty engine. The prototype HPDI engine met all technical targets resulting in a payment of €2.4 million (approximately US$2.7 million) by Daimler to Westport. For competitive reasons, further terms of the program have not been disclosed.
Westport HPDI 2.0 delivers performance and fuel economy equivalent to that of current high performance diesel-fueled engines, but with diesel substitution of more than 90%. This combination of high performance and high efficiency is critical for heavy-duty engines in demanding commercial applications. In addition to delivering performance and fuel economy, Westport HPDI 2.0 is designed to meet the latest in stringent emission regulations, including Euro VI and EPA 2014.
Most current natural gas engines used in mobile applications require up to 30% reduction in compression ratio and 15% to 20% reduction in peak torque output to avoid the risk of engine-damaging knock, which reduces fuel economy and performance. Late-cycle direct injection of fuel—a principle fundamental to the Westport HPDI architecture—eliminates the danger of engine knocking.
In SI gasoline and natural gas engines, air and fuel are pre-mixed before entering the combustion chamber. Knock can occur when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. SI engines that run on natural gas need a lower compression ratio to reduce the chance of engine knock. The compression ratio must be low enough to ensure combustion events do not begin until after compression is complete and the spark plug is fired. Inevitably, lower energy efficiency is the result, which means more fuel burned to achieve the same level of work.
Westport HPDI uses natural gas as the primary fuel along with a small amount of diesel as an ignition source. The two fuels are not pre-mixed with the intake air before they enter the combustion chamber so there is no risk of engine knock and therefore no need to lower the compression ratio and peak torque output. As compared to diesel fuel, directly injected natural gas burns with a lower adiabatic flame temperature and has a low propensity to the formation of carbon particles and therefore offers inherent NOx and particulate matter (PM) emissions.
HPDI 2.0 continues the evolution of Westport natural gas storage and delivery systems with a new generation of proprietary fuel tank, fuel pump, and system controls.