6. Overview, Advancements and Challenges in Gasoline Direct Injection Engine Technology

Gasoline direct injection engines have become the popular powertrain for commercial cars in the market. The technology is known for its characteristics of high power output, thermal efficiency and fuel economy. Accurate metering of fuel injection with better fuel utilization makes the engine possible to run on lean mixtures and operation under higher compression ratio relatively makes it of greater potential than PFI engines. Due to its capability of being operated under dual combustion mode by varying fuel injection timing, it can be realized as a cornerstone for future engine technology. Under mode switching, the homogeneous mixture for higher power output at medium and high load-rpm conditions, and stratified mixture for greater fuel economy at low load-rpm conditions are achieved respectively. It can be considered as the technology having the benefits of both diesel engine of higher thermal efficiency and gasoline engine of higher specific power output. But, with the growing concerns towards the limited fuel reserves and the deteriorated environment conditions, strict norms for tail-pipe emissions have been regulated. And considering the higher particulate matter and particle number emissions as a major drawback for GDI engine, upgradation and improvement in designs is needed to meet the required norms of emissions. In the initial section, the chapter gives a brief idea of the overview of the GDI combustion system and its operating modes. Subsequently, the improvements and researches in various aspects like fuel injection parameters and strategies, dual fuel utilization, mixture formation, lean burn control and application of providing turbocharging and residual gas fraction, are elaborately discussed in the direction of optimizing the performance of the engine. Further, the following section explains the major challenges and overcoming of this technology. Review of the work done by various researchers is discussed, focussing on the effect of operating parameters on particulates emissions, injector deposits and knocking in GDI engine. Finally, the chapter presents the concluding ways for enhancing the performance, way forward for making it more efficient and reliable by overcoming the limitations of GDI engine technologies.