A Study of Quasi-Homogeneous Lean Burn Gasoline Engine Performance Based on the Numerical Simulation

A CA3GA2 lean combustion gasoline engine one dimensional model was built by AVL BOOST software. The relationship between air-to-fuel ratio (A/F) and emission characteristic and fuel economy was simulated. Simulation shows that: (1) CO emission decreases as the A/F ratio increases; (2) HC emission reaches its lowest point at A/F=16~18; (3) NOX emission reaches its highest point at A/F=16~18; (4) the engine lean combustion limit is A/F=22, the brake specific fuel consumption (BSFC) decreases as the A/F ratio increases within the lean combustion limit.

Secondary Fire Induced by Mine Methane Explosions

The mechanism of fire induced by methane explosions was studied to know about the great danger of induced fire. Firstly, from the point of heat ignition to study it, then the especial heat environment after explosions was studied. Lastly, from the point of characteristics of gas separated from fuel to judge whether fire to be induced. The part of heat ignition was based on conservation of energy. And the special heat environment was studied by using CFD software Fluent to do some numerical simulation. As to gas separated from fuel, mainly from three aspects to discuss it: yields of gas and relating conversion, diffusion velocity, minimum combustion supporting oxygen concentration. And the research shows that, if the gas separated out from fuel could diffuse to satisfy the minimum combustion limit before the temperature of environment reduce to its fire induced temperature, and there is enough oxygen, sub-fire could be induced. This research could provide some technique support to prevent and cure such kind of accident, and has great significance.

Effects of Engine Operating Parameters on Lean Combustion Limit of Hydrogen Enhanced Natural Gas Engine

An experimental study was conducted on a S.I. engine fueled by compressed natural gas and hydrogen blends (HCNG), in order to test different engine operating parameters that affect lean combustion limit (L.C.L) of HCNG engine. Firstly, constant ignition timing and ignition timing under maximum L.C.L (L.L.T) conditions were compared, then L.L.T conditions were adopted in this paper. The results indicated that for each condition, neither over-retarded nor over-advanced ignition timing are advised in order to achieve leaner combustion. L.C.L increases with hydrogen fraction in the blends, and slightly increases with throttle opening, while decreases when the engine speed is raised