Basic Investigation of Thermodynamic Effects on a Hydrogen Two-Stroke Engine

<div class="section abstract"><div class="htmlview paragraph">The spark ignited two-stroke engine, as a cost-efficient power unit with low maintenance demand, is used millionfold for the propulsion of hand-held application, motorcycles, scooters, boats and others. The outstanding power to weight ratio is the key advantage for two-stroke engines. However, poor exhaust emissions, caused by high scavenge losses, especially on port controlled two-stroke engines, and a low efficiency are disadvantages of this combustion process. Under the aspect of increasing environment- and health awareness, the two-stroke technology driven with fossil resources, shows no future advantage. The anthropogenic climate change force for sustainable development of combustion engines whereby reduction of fuel consumption or usage of alternative fuels is an important factor. Best way of a decarbonization to fulfil future climate goals is the utilization of non-carbon fuels. In this field of fuels, hydrogen, with its high energy content and close inexhaustible availability, shows a good solution.</div><div class="htmlview paragraph">Four-stroke gasoline engines are developed since many years for the use of hydrogen. Different strategies of mixture preparation, like port- or direct injection with low- or high injection pressure are available and well known. Compared with two-stroke engines, the usage of hydrogen and, therefore, the knowledge about thermodynamic effects, is still at the beginning. Challenges, such as inhomogeneous air-fuel mixture within the cylinder at high speed, short-circuiting of fuel to the exhaust, and backfiring in the crankcase are open points. In the context of this paper basic investigations of the combustion process with thermodynamic limits are presented. Starting with the general layout of the mixture preparation, an overview of the whole system and safety features are shown. The aim of research is to declare the limits of the combustion and gas exchange process with respect to the combustion abnormalities such as self/pre-ignition and knocking. From this, possible optimizations can be derived. To gain knowledge about the combustion specific relations with the focus on high output performance, different basic approaches are tested. In conclusion, a better understanding of limits in terms of temperatures, mixture preparation, spark advance and injection timing is achieved.</div></div>