Review on spray, combustion, and emission characteristics of recent developed direct-injection spark ignition (DISI) engine system with multi-hole type injector

Given diminishing fossil fuel resources and severe environmental pollution, governments are strengthening their regulations regarding the exhaust emissions and fuel consumption of transportation vehicles. To satisfy the new stringent requirements for emission and efficiency, researchers have attempted to combine the advantages of gasoline and diesel engines in a single engine. Studies on gasoline direct -injection (GDI) engines have been conducted since the early 1990s. In a GDI engine, the fuel is directly injected into the combustion chamber to form a stratified air/fuel mixture for ultra-lean combustion. To achieve the proper mixture in the combustion chamber of a GDI engine, various injection and airflow strategies have been implemented, such as the multiple-injection and spray-guided techniques. In addition, various emission after-treatment devices, such as a gasoline particulate filter and lean NOx trap have been used to reduce exhaust emissions. Major injector manufacturers recently embarked on the development of a piezo-outwardly type injector and a multi-hole type injector to improve engine performance and reduce exhaust emissions. In addition, researches are actively pursuing alternative fuels, such as bioethanol and biobutanol, eco-friendly alcohol fuels, for use in GDI engines. In this review article, we examine and discuss the GDI engine system. Our objective in the review is to examine the injection, spray, combustion, and exhaust emission characteristics of a GDI engine with a multi-hole injector. We also review numerical methods for modeling a GDI engine and describe the characteristics that make alcohol fuels useable in GDI engines.