Effects of lean combustion coupling with intake tumble on economy and emission performance of gasoline engine

To improve the economy and emission performance of automotive gasoline engine, the approach of lean combustion coupling with intake tumble was investigated. A port blocker was designed on intake manifold so as to generate intake tumble, and then the sweeping test of excess air coefficient was conducted under engine common conditions (2000 r/min, 2.6 bar) in two port blocker states (opening and closing). On this basis, the effects of lean combustion coupling with intake tumble on the working process, combustion and emission performance of gasoline engine were studied. The tested results indicate that lean combustion limit is obviously extended with acceptable combustion stability by utilizing intake tumble, thus the potential of energy conservation and emission reduction by lean combustion can be further enhanced. Compared with the initial state of original engine (λ = 1.0, port blocker closing), the indicated thermal efficiency can be increased by 7.2%, and the specific emissions of CO2, CO, HC and NOX can be reduced by 5.8%, 72.2%, 12.0% and 85.3% at most, respectively. In particular, the minimum specific emission of NOX is only 2.0 g/(kW·h). The results demonstrate that lean combustion coupling with intake tumble has great potential of energy conservation and emission reduction for gasoline engine.