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Wall temperature in GDI engine is influenced by both water jacket and gas heat source. In turn, wall temperature affects evaporation and mixing characteristics of impingement spray as well as combustion process and emissions. Therefore, in order to accurately simulate combustion process, accurate wall temperature is essential, which can be obtained by conjugate heat transfer (CHT) and piston heat transfer (PHT) models based on mapping combustion results. This CHT model considers temporal interaction between solid parts and cooling water. This paper presents an integrated methodology to reliably predict in-cylinder combustion process and temperature field of a 2.0L GDI engine which includes engine head/block/gasket and water jacket components. A two-way coupling numerical procedure on the basis of this integrated methodology is as follows.

This paper describes a simulation guided design methodology for developing direct injection combustion systems of gasoline engines. The first step is the optimization of engine gas flow. The intake port is optimized by CFD simulations to compromise the engine breathing capacity and its tumble flow. Secondly, the piston crown shapes and the injection system designs (injection pressure, hole number, hole size and orientations) are optimized based on dedicated CFD simulation results. Thirdly, different injection strategies are used at different engine operating conditions to achieve best engine performance, such as split injections being used at cold starting and catalyst heating period to realize stratified charge combustion for fast catalyst light-off, and a single injection being used to achieve homogeneous mixture combustion at almost all other operating conditions.

Gasoline direct injection (GDI) engines have been developed rapidly in recent years, driven by stringent legislative requirements on vehicle fuel efficiency and emissions. However, one challenge facing GDI is the formation of particulate emissions, particularly with the presence of injector tip deposits. The Chinese market features some gasoline fuels that contain no detergent additives and are prone to deposit formation, which can affect engine performance and emissions. The use of detergent additives to mitigate the formation of injector deposits in a GDI engine was investigated in this study by testing a 1.5L turbocharged GDI engine available in the Chinese market. The engine was operated both on base gasoline and on gasoline dosed with detergent additives to evaluate the effect on injector deposit formation and engine performance and emissions.

Due to its load control strategy via fresh charge quantity, pumping loss in a homogenous charge gasoline engine is a significant contributor to the high fuel consumption rate at light load. Exhaust gas recirculation (EGR) and lean burn technologies are the common means to reduce gasoline engine pumping loss for fuel economy improvement. Many previous publications compared the EGR and lean burn concepts. However, few of those were able to compare the EGR and lean burn concepts under the same in-cylinder dilution basis. Usually the un-swept in-cylinder residual gas fraction (RGF), which can be significant at very low loads, was ignored due to lack of appropriate method to determine it. Also the theoretical potential and practical limitations were rarely discussed. In this paper, a Naturally Aspirated (NA) gasoline engine was systematically tested for both the EGR and lean mixture concepts on an engine dyno. under the same speed and load conditions.

Changan has upgraded its 1.6 L naturally aspirated GDI engine to meet future fuel economy and emission regulation base on its previous 1.6 L naturally aspirated GDI engine, the major upgrades include a high compression ratio of 13, 35Mpa direct injection system, cooled external EGR, thermo management module,and extensive measures to reduce friction. With this new engine, the vehicle fuel consumption is reduced by 9%, and meet the China 6b emission standard without GPF.

Performance and particulate emissions of a modern common-rail and turbocharged diesel engine fueled with diesel and biodiesel fuels were comparatively studied. An electrical low-pressure impactor (ELPI) was employed to measure particle size distribution and number concentration. Two biodiesel fuels, BDFs (biodiesel from soybean oil) and BDFc (biodiesel from used cooking oil), as well as ultra-low sulfur diesel were used. The study shows that biodiesels give higher thermal efficiency than diesel. Biodiesels give obviously lower exhaust gas temperature than diesel under high engine speed. The differences in fuel consumption, thermal efficiency and exhaust gas temperature between BDFs and BDFc are negligible. The first peaks of heat release rate for biodiesels are lower than that of diesel, while the second peaks are higher and advanced for biodiesels. BDFs show slightly slower heat release than BDFc during the first heat release stage at low engine speed.

Gasoline direct injection (GDI) engine technology is now widely used due to its high fuel efficiency and low CO2 emissions. However, particulate emissions pose one challenge to GDI technology, particularly in the presence of fuel injector deposits. In this paper, a 4-cylinder turbocharged GDI engine in the Chinese market was selected and operated at 2000rpm and 3bar BMEP condition for 55 hours to accumulate injector deposits. The engine spark timing, cylinder pressure, combustion duration, brake specific fuel consumption (BSFC), gaseous pollutants which include total hydro carbon (THC), NOx (NO and NO2) and carbon dioxide (CO), and particulate emissions were measured before and after the injector fouling test at eight different operating conditions. Test results indicated that mild injector fouling can result in an effect on engine combustion and emissions despite a small change in injector flow rate and pulse width.

Gasoline Direct Injection (GDI) engines have developed rapidly in recent years driven by fuel efficiency and consumption requirements, but face challenges such as injector deposits and particulate emissions compared to Port Fuel Injection (PFI) engines. While the mechanisms of GDI injector deposits formation and that of particulate emissions have been respectively revealed well, the impact of GDI injector deposits and their relation to particulate emissions have not yet been understood very well through systematic approach to investigate vehicle emissions together with injector spray analysis. In this paper, an experimental study was conducted on a GDI vehicle produced by a Chinese Original Equipment Manufacturer (OEM) and an optical spray test bench to determine the impact of injector deposits on spray and particulate emissions.