Distributed Gas Ignition Using Injection Strategy for High Efficiency and Clean Combustion Under Lean Condition
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Distributed Gas Ignition Using Injection Strategy for High Efficiency and Clean Combustion Under Lean Condition Ziqing Zhao1 · Wei Liu1 · Fubai Li1 · Qinhao Fan1 · Zhi Wang1 Received: 27 March 2020 / Accepted: 12 August 2020 © China Society of Automotive Engineers (China SAE) 2020
Abstract 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. Keywords Distributed gas ignition · Multi-scattering flame · Injection strategy · Thermal efficiency · Lean combustion Abbreviations ATDC After top dead center BTDC Before top dead center CA Crank angle COV Coefficient of variation DGI Distributed gas ignition EGR Exhaust gas recirculation HCCI Homogeneous charge compression ignition HRR Heat release rate IMEP Indicated mean effective pressure ITE Indicated thermal efficiency NG Natural gas SI Spark ignition TDC Top dead center
* Zhi Wang [email protected] 1
State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China
1 Introduction The stringent emission regulations are driving more and more research of clean fuel and advanced technology in the internal combustion engine industry. Among the clean fuels, natural gas (NG) is one of the most promising fuels due to its low carbon-to-hydrogen ratio [1]. The global distribution of NG contributes to its potential for wider applications. Apart from the fuel, higher thermal efficiency of the engine is being pursued by researchers. Among the technologies to maximize the engine efficiency, lean burn is indispensable. The excess air improves the isentropic coefficient of mixture and reduces combustion cooling loss. Both factors benefit the engine efficiency. However,
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