Exhaust gas recirculation strategy in the hydrogen SI engine

It is known that Exhaust Gas Recirculation (EGR) can be successfully applied not only for reducing NOx content in exhaust gases but also for reduction of combustion knock in SI engines. From this point of view, EGR can be particularly effective for knock elimination in the hydrogen reciprocating engine. Additionally with the application of EGR, the H2-air combustion can be maintained at the stoichiometric ratio enabling highly efficient NOx reduction in catalytic converters. In this paper a strategy of estimating EGR for the naturally aspirated, hydrogen fuelled engine is explained. On the basis of this strategy, the closed loop control system of the EGR was built and was implemented for the single cylinder CFR engine. There is also an outline of the test bed and several examples of in-cylinder pressure courses recorded under various EGR percentages. Next, the impact of EGR on combustion knock in the hydrogen fuelled engine is presented. Finally, conclusions concerning EGR application for hydrogen combustion in the IC engine are presented. EGR calculation and control scheme, main diagram of EGR calculation, subroutine (Sub-block) for calculating the molecular weight of EGR gases, in-cylinder pressure traces for several EGR levels during hydrogen combustion in the CFR engine, the fluctuating component of in-cylinder pressure during hydrogen combustion with several levels of EGR, peak pressure of fluctuation component of in-cylinder pressure vs. EGR percentage are presented in the paper.