Opposed-piston two-stroke engines offer numerous advantages over conventional four-stroke engines, both in terms of fundamental principles and technical aspects. The reduced heat losses and large volume-to-surface area ratio inherently result in a high thermodynamic efficiency. Additionally, the mechanical design is simpler and requires fewer components compared to conventional four-stroke engines. When combining this engine concept with alternative fuels such as hydrogen and pre-chamber technology, a potential route for carbon-neutral powertrains is observed. To ensure safe engine operation using hydrogen as fuel, it is crucial to consider strict safety measures to prevent issues such as knock, pre-ignition, and backfiring. One potential solution to these challenges is the use of direct injection, which has the potential to improve engine efficiency and expand the range of load operation. In order to achieve compression ignition with hydrogen, it is necessary to either have high compression ratios or pre-heat the fresh charge. Accordingly, the utilization of a pre-chamber serves as a means to facilitate turbulent jet ignition, enabling the generation of high-momentum, elevated-temperature jets. This method boosts turbulence during combustion, expanding operational range into leaner fuel-air mixtures, affirming the pre-chamber`s efficacy in enhancing ignition. In this study, the numerical assessment of the ignition of a direct-injected hydrogen plume through a pre-chamber jet is conducted using CONVERGE as the solver. The aim is to determine the optimal configuration for exploiting momentum exchange between the jets while also keeping the flames away from the walls to reduce heat losses. To achieve this, three different piston bowl designs are created to prevent flame-wall interaction. A merit function is used to select the most efficient and least NOx emitting case. This case is then compared to premixed combustion without a pre-chamber. Finally, the study concludes with a comparison between the best hydrogen combustion case and conventional diesel combustion.
Session:
Hydrogen I
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| 11:30 - 12:00