Managing cryogenic fuels on heavy-duty HPDI vehicles

Westport Fuel Systems’ High Pressure Direct Injection (HPDI) technology is commercially available in Europe on OEM Heavy Duty trucks, with further applications expected to be released in China shortly. HPDI allows Heavy Duty trucks to retain the advantages of the diesel engine (torque, transient response, efficiency and durability) while gaining the advantage of a cheaper fuel and maximizing the CO2 reduction relative to diesel. The latter is particularly important with the latest European legislation, which requires a reduction of 15% by 2025, and 30% by 2030; HPDI equipped engines have already shown a 20% reduction in CO2, and, coupled with the planned vehicle and engine improvements, is expected to meet the 2030 targets. The potential inclusion of renewable natural gas as a further reduction factor in the legislation could effectively lead to a 100% reduction in the CO2 emissions of an HPDI vehicle.While an HPDI engine runs on high pressure compressed gas, the off-engine system typically stores the fuel cryogenically to maximize the vehicle range. Cryogenics present interesting challenges for vehicle applications; hold time is a consideration for any cryogenic system, while customer requirements such as maximizing range, and minimizing weight and space claim add conflicting factors. While these considerations impact any vehicle using a cryogenic system, the high pressure gas requirement for HPDI adds another factor: how to supply compressed gas with minimal parasitic impact to the engine. This paper explores internal and external pumping of gas, and approaches for minimizing vented gas and maximizing hold time. The paper concludes with a look toward future opportunities.