A study if backfire in hydrogen engines

摘要

A 4 cylinder diesel engine is modified for hydrogen use by the installation of a gas carburettor. If the fuel-air mixture formed in the intake manifold pre-ignites before the inlet valve is closed, the result is backfire. This backfire phenomenonoccurs easily in external mixture formation type hydrogen fuelled engines.In a first study the development of the pressure in the combustion chamber of one cylinder and the pressure in the inlet manifold is stored prior to backfire (during 32 successive cycles), as well as during and after backfire. The pressure traces arecarefully examined and analysed to determine the start of combustion, the combustion duration, the maximum combustion pressure and the occurrence of knock for each of the successive cycles. It is observed that prior to backfire sudden pre-ignitioncombined with knock appears, which results in a run-away pre-ignition.In a second study the influence of engine parameters (ignition timing, supercharging conditions) on the occurrence of backfire are examined, as a function of the air-fuel ratio.Finally the behaviour of hythane mixtures (mixtures of natural gas and hydrogen) with respect to backfire is analysed in a GM V8 engine. For hythane mixtures with a hydrogen content of 80% or less, safe operation of the engine is guaranteed (no backfirenor knock), whatever the air-fad ratio of the engine.