Analysis of a Gas Engine with Arbitrary Mixture Ratio of H ₂ and CNG for HDV 2021-01-1177

To reduce exhaust emissions in commercial vehicles, hydrogen, as a carbon-free fuel, is a reasonable alternative to conventional fuels. In order to circumvent the current problem of hydrogen availability, the use of a gas engine for heavy duty vehicles (HDV), which is able to operate with pure compressed natural gas (CNG), pure hydrogen as well as any mixture of these both gases, is sensible.

For this purpose, an operating concept for a gas engine was developed, which is able to operate with an arbitrary hydrogen-natural gas mixture ratio. Therefore, the mixture formation of a hydrogen-natural gas-air mixture was analyzed in a 3D CFD simulation. The results for pure hydrogen and pure CNG operation show a very good homogenization of the fuel distribution at the point of ignition when an outward-opening injector was used. Based on these results, an 1D simulation was used to generate an operating map of the gas engine and investigate it with regard to its efficiency and exhaust emissions. A lean operation (λ > 1.8) was established to avoid high NO_x emissions. For the final evaluation, this HDV-concept was analyzed regarding to its economic efficiency. Due to this, the capital and operational expenditure (CAPEX/OPEX) of the hydrogen-natural gas ICE were compared with a proton-exchange membrane (PEM) fuel cell system. The capital costs for heavy duty vehicles of a PEM fuel cell system are significantly higher in comparison to the capital costs of a gas engine. Even the lower operating costs of the fuel cell cannot compensate for this. Accordingly, a gas engine shows significantly higher potential in the economic evaluation today.