High pressure direct injection with pilot ignition (H₂-HPDI), a combustion approach for hydrogen in engines, has the potential to achieve fuel economy close to that of a fuel-cell electric vehicle (FCEV) for heavy duty applications, due to its high efficiency at both part and full loads. This finding is the result of a model-based analysis by alternative fuel transportation technology developer Westport Fuel Systems and powertrain system developer AVL.

The study considers the case for hydrogen use in an internal combustion engine (ICE) with Westport Fuel Systems’ patented HPDI 2.0 fuel system, as the most cost-competitive near-term pathway to reduce carbon dioxide emissions to near-zero from on-road long-haul transportation. The total cost of ownership (TCO) analysis applies inputs from HPDI hydrogen simulations and operating costs with AVL’s existing TCO models for diesel and fuel cell powertrains.

The H₂-HPDI system was determined to outperform hydrogen-fueled port fuel injection with spark ignition and early cycle direct injection with spark ignition options in thermal efficiency. Hydrogen combustion engines significantly reduce CO₂, hydrocarbon and particulate matter emissions, leaving nitrogen oxides as the most prominent tail pipe emission. For H₂-HPDI under identical operating conditions compared to a diesel engine, it is expected that nitrogen oxides emissions would be higher due to higher temperature combustion of hydrogen, but these can be managed with exhaust as recirculation and available urea-selective catalytic reduction exhaust aftertreatment technology.

As a high efficiency hydrogen ICE powertrain, the H₂-HPDI system can outperform FCEVs in terms of TCO. This is possible because H₂-HPDI leverages powertrain systems currently in high volume production while achieving near fuel cell-like efficiency in heavy duty applications.

Components of the H2-HPDI powertrain. Source: Westport Fuel Systems