THE EFFECT OF SPRAY ON COMBUSTION AND EMISSION IN DIRECT-INJECTION SPARK-IGNITION ENGINES = THE EFFECT OF SPRAY ON COMBUSTION AND EMISSION IN DIRECT-INJECTION SPARK-IGNITION ENGINES

다국어 초록 (Multilingual Abstract)

In the light of energy and environmental concerns, the CO₂ regulation for light-duty vehicles has become stricter than ever. Direct-injection spark-ignition (DISI) engine with a turbocharger is regarded as a major technology to improve the thermal efficiency and to lower the specific fuel consumption. However, the direct injection of gasoline leads the inhomogeneous air-fuel mixture in the cylinder and the fuel film deposition on the walls. As a result, the particulate matter (PM) emission is deteriorated compared to conventional port fuel injection engines. European Union enforced the emission regulation on the particulate number (PN) of DISI engine powered vehicles as 6×10¹¹/km from September 2017. To satisfy the stringent regulation without an after-treatment system, an in-depth understanding of the spray and combustion fundamentals, as well as a substantial optimization effort for the engine operating strategy, are required.
The PM emission arises from the local fuel-rich mixture around the fuel film in DISI engines so that the spray injection plays the key role in the PM reduction. In this presentation, both experimental and numerical investigation on the effect of spray injection in a DISI engine will be covered. First, the potential of injection strategy on the PN emission level will be discussed based on the PM measurement in both metal and optical-accessible single-cylinder research engine. Then, the combustion and soot emission modeling and their application to CFD simulation will be presented to propose an efficient and reliable tool for the optimization of engine system. The rig-experiment enables the fundamental understanding of spray behavior and provides the valuable reference data for the model validation. This talk also discusses the spray evolution including penetration length, spray cone angle, and sauter mean diameter under various injection conditions. Finally, the measurement and modeling work on the spray-wall impingement and fuel film formation will be presented.