To control the ignition timing in a gasoline compression ignition (GCI) engine, ozone (O3) was introduced into the intake air. The O-radicals are decomposed from the O3 above 550 K during the compression stroke, and combine into oxygen (O2) in a very short time.The authors adopted two-stage direct injection to mix the fuel injected into the cylinder at very early timings with the O-radicals, before a reduction of the O-radicals would take place. The ignition timing of the second fuel injection for the main combustion is controlled by the heat release from the first fuel injection. In this paper, engine experiments were performed to examine the feasibility of the ignition control with a primary reference fuel, octane number 90 (PRF90). The O3 concentration, the quantity, and the timing of the first injection were changed as experimental parameters. The results showed that a very small quantity of O3, tens of ppm, is sufficient to promote the heat release of the first injected fuel. The heat release increases with the O3 concentration and

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Abstract-Hydrogen is a means to chemically store energy. It can be used to buffer energy in a society increasingly relying on renewable but intermittent energy or as an energy vector for sustainable transportation. It is also attractive for its potential to power vehicles with (near-) zero tailpipe emissions. The use of hydrogen as an energy carrier for transport applications is mostly associated with fuel cells. However, hydrogen can also be used in an internal combustion engine (ICE). When converted to or designed for hydrogen operation, an ICE can attain high power output, high efficiency and ultra low emissions. Also, because of the possibility of bi-fuel operation, the hydrogen engine can act as an accelerator for building up a hydrogen infrastructure. The properties of hydrogen are quite different from the presently used hydrocarbon fuels, which is reflected in the design and operation of a hydrogen fueled ICE (H 2 ICE). These characteristics also result in more flexibility in engine control strategies and thus more routes for engine optimization. This article describes the most characteristic features of H 2 ICEs, the current state of H 2 ICE research and demonstration, and the future prospects.

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