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1、New Development of Gasoline Direct Injection Engine in AsiaNew Development of Gasoline Direct Injection Engine Abstract: In recent years, as emission regulations being stricter, many automobile manufacturers and research institutions are both seeking ways to improve engine performance by injecting f
2、uel into cylinder directly. This article gives an outline of development of GDI engine in Asia and emphatically introduces the Toyota GDI engine and Hyundai Theta II GDI engine.Keywords: GDI; Asia; Toyota; D-4S combustion system; Hyundai.6INTRODUCTIONThe requirement of reduced emissions is critical
3、for modern automobiles. As a possible solution to increase the fuel economy and reduce emissions of automotive engines, GDI engines have been considered for many years. Compared with conventional PFI engines, GDI engines are higher full-load performance, lower emissions such as HC, NOx and CO emissi
4、ons and better fuel economy. So far, several automobile manufacturers have introduced GDI engines to the worldwide markets. DEVELOPMENTMitsubishi was the first to develop gasoline direct injection engine 4G93 1.8L inline-four in the market in 1996. It is available in both SOHC and DOHC versions. It
5、also developed the first six-cylinder GDI engine, the 6G74 3.5L V6, in 1997. It had a crown-curved rather than flat combustion chamber, upright intake ports rather than angled, and a 10.4:1 compression ratio. Mitsubishi claimed 30 percent better fuel economy, a 30 percent reduction in emissions, and
6、 higher power outputs than diesels.Nissan released the Leopard featuring the VQ30DD equipped with direct injection in 1997. The engine has bore and stroke of 93mm and 73.3mm, with a compression ratio of 11:1. In 1998, the first direct injection system of Toyota D4 appeared on Japanese market vehicle
7、s equipped with the SZ and NZ engines. Toyota later introduced its D4 system to European markets with the 1AZ-FSE engine found in the 2001 Avensis. In 2005, Lexus GS 300 equipped with the 3GR-FSE engine was found in US markets. Toyotas 2GR-FSE V6 uses a more advanced direct injection system, which c
8、ombines both direct and indirect injection using two fuel injectors per cylinder, a traditional port fuel injector (low pressure) and a direct fuel injector (high-pressure) in a system known as D4-S. In 2003, Honda released its own direct injection system on the Stream sold in Japan. Hondas fuel inj
9、ector is placed directly atop the cylinder at a 90-degree angle rather than a slanted angle. In 2005, Mazda began to use their own version of direct-injection in the Mazdaspeed6 and later on the CX-7 sport-utility, and the new Mazdaspeed3 in the US and European market. It is referred to as Direct In
10、jection Spark Ignition (DISI). In 2011, the Hyundai Sonata 2011 use GDI engines. Hyundais Theta I-4 engine family is a proprietary design, engineered in Namyang, Korea and currently in production for applications all over the world.TOYOTA 1st GENERATION GDI ENGINESThe Toyota first-generation direct-
11、injection combustion system, the D-4 is swirl-based, wall-guided (Fig.1). Fig.1 Schematic of the Toyota first-generation D-4 engine systemThe helical intake port utilizes a variable-valve-timing-intelligent (VVT-i) cam-phasing system on the intake camshaft. According to engine operating conditions,
12、valves can be controlled to acquired desired angle. The engine uses swirl current valve (SCV) in different load conditions. The SCV is closed in light-load condition to form a stratified air-fuel mixture. The SCV is opened in heavy-load to form homogeneous mixture.It is hard for fuel flow to penetra
13、te against high environmental pressure and atomize in a short time during the compression stroke, so high fuel injection pressure is necessary. The newly developed high pressure swirl injector (Fig.2) uses an injection pressure of 12 MPa to meet these requirements. The direction of injection is offs
14、et from the spark plug to allow enough time for the fuel to vaporize.Fig.2 Swirl injectorThe D-4 engine also uses a NOx storage catalyst. The stored NOx is converted at time intervals of 50 seconds during lean operation by utilizing very brief periods of stoichiometric operation. TOYOTA 2nd GENERATI
15、ON GDI ENGINESIn 1999, Toyota marketed a second-generation D-4 combustion system (Fig.3). This latest D-4 engine operates in three modes: (1) for cold start, high-load, or NOx-reduction operations is homogeneous-charge combustion with an air/fuel ratio in the range of 12:1 to 15:1;(2) for medium-loa
16、d operation is weakly-stratified-charge combustion with an air/fuel ratio between 15:1 and 30:1; (3) for low-load operation is stratified-charge, lean-to-ultra-lean operation, employing an air/fuel ratio ranging from 17:1 to 50:1. Fig.3 Schematic of the Toyota first-generation D-4 engine systemCompared to the first-generation D-4 combustion system, one of the major changes is the elimination of the helical port, which enables the latest
