Air:fuel ratio control in a gas engine supplied with a weak fuel gas via a venturi mixer

摘要

An apparatus for supplying fuel gas from a fuel gas source 3 to a gas engine 2 comprises a zero pressure regulator 2, venturi mixer with flow path 21 and first fuel inlet 24, supply duct 7 and enrichment valve 40. The flow path comprises an air inlet region 22 and a mixing region 23, and reduces in cross-section from the air inlet region to the mixing region. The first fuel inlet opens into the mixing region, the mixing region arranged to mix fuel gas and air to form a mixture M. The zero pressure regulator supplies fuel gas from the source to the first fuel inlet at a first static pressure equal to the static pressure of air supplied to the air inlet region. The supply duct receives the mixture M wherein a second fuel inlet opens into the supply duct, downstream of the mixing region, and the enrichment valve controls the supply of fuel from the source to the second fuel inlet at a second static pressure which is higher than the first. Ideally, the apparatus supplies weak fuel gas to an engine, the enrichment valve supplying addition fuel gas in response to increased engine load.