Distributed Gas Ignition Using Injection Strategy for High Efficiency and Clean Combustion Under Lean Condition

Jet ignition is an efficient way to achieve lean burn of the engine and a promising strategy to meet the stringent emission regulations in the future. This paper presents a distributed gas ignition (DGI) combustion concept and realizes a DGI combustion mode using a newly designed DGI igniter. The igniter integrates a fuel injector and a spark plug to achieve minimum volume and easy installation. As the mixture preparation within the jet chamber is essential for the performance of the igniter, different jet chamber injection strategies were tested with varying excess air–fuel ratio ranging from 1.4 to 2.0. By addressing the dual injection strategy, the ignition delay and combustion duration were improved evidently. Compared with the single injection strategy, dual injection strategy improves the flexibility when preparing the mixture inside the jet chamber and therefore retains more fuel. The increased energy density of the jet chamber helps to generate more energetic jets under dual injection strategy, resulting in the improvement of ignition and combustion performance with lean burn. A higher thermal efficiency and a leaner limit of the engine are attained with dual injection than that with single injection. Dual injection exhibits its potential in reducing CO and THC emissions to an acceptable level with leaner mixture. Based on dual injection strategy, the maximum indicated thermal efficiency of 45% is achieved.