1、Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection New Words Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Although MPI provides a drastic improvement in response and combustion quality, it is still limited due to fuel and air mixing prior to entering the cylinder.

2、To further increase throttle response and combustion efficiency, while lowering fuel consumption and increasing output, systems may use direct injection. Gasoline direct injection engines are engineered to inject the gasoline directly into the cylinder in a manner similar to diesel direct injection

3、engines (Fig.2-14).Direct injection is designed to get better fuel economy. This is accomplished by enabling combustion of an ultra-lean mixture under many operating conditions. Direct injection is also designed to allow higher compression ratios, delivering higher performance with lower fuel consum

4、ption. Currently, direct injection gasoline engines are being deployed throughout the world in passenger cars. Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Fig.2-14 Gasoline direct injectionA variety of air-fuel mixtures can be created according to changes in the fuel injection

5、timing. The GDI engine provides both lower fuel consumption and higher output. This is achieved with the use of two combustion modes. These two modes are represented in Figure 2-15. Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Figure 2-15 Mitsubishi GDI uses two combustion modes

6、 Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Ultra-lean Combustion Mode. Under most normal driving conditions, up to speeds of 120 km/h, the Mitsubishi GDI engine operates in ultra-lean combustion mode, resulting in less fuel consumption. In this mode, fuel injection occurs at

7、the latter stage of the compression stroke and ignition occurs at an ultra-lean air-fuel ratio of 30-40. This operating mode is also called as stratified-charge mode. Superior Output Mode. When the GDI engine is operating with higher loads or at higher speeds, fuel injection takes place during the i

8、ntake stroke. This optimizes combustion by ensuring a homogeneous, cooler air-fuel mixture which minimizes the possibility of engine knocking. This mode is also called as homogeneous-charge mode. Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Two main operating modes of Volkswagen

9、 AGs fuel stratified injection (FSI) which uses more operating modes and FSIs fuel-saving potential is shown in Figure 2-16. A typical pulse injection system with direct injection is given in Fig.2-17. Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Figure 2-16 Main operating modes

10、 and fuel-saving potential of Volkswagen AGs FSI direct-injection Chapter 2 Internal Combustion Engine2.7 Gasoline direct injection Fig.2-17 Gasoline direct injection systemChapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System New WordsChapter 2 Internal Combustion Engine2.8 Diesel Fu

11、el Injection System New Words Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System 2.8.1 Conventional SystemTypical diesel system components include the fuel tank, fuel pump, fuel filter, injection pump, injectors, and the necessary fuel lines (Fig.2-18). The system in Fig.2-19 is ty

12、pical of newer systems that utilize a computer-controlled electronic fuel injection pump. Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System Fig2-18 A conventional diesel fuel injection system Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System Fig2-19. An computer

13、 controlled diesel fuel injection system with axial-piston distributor injection pump Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System Fuel Filter. Diesel fuel must be kept clean to avoid injector system trouble. Very small particles are enough to clog injector nozzles. Diesel fu

14、el systems typically use one or more filters to trap dirt and other deposits. Injection Pump. Due to the high compression (around 22:1) used in diesel engines, the diesel injection pump must be capable of producing high pressures. There are a number of injection pump designs. The most commonly used

15、automobile and light truck diesel injection pumps are classified as inline or distributor. The inline injection pump（Figure 12-18） uses a separate cylinder plunger-cam unit （Fig.2-20）for each cylinder. These units are contained in a straight row in a common housing. Chapter 2 Internal Combustion Eng

16、ine2.8 Diesel Fuel Injection System Figure 2-20. Pump plunger construction. When the control rack is moved, the plunger will be forced to rotate by the segmented gear sleeve acting on the plunger flange. Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System Fig.2-21 Cutaway view of a

17、distributor type injection pump. The distributor injection pump is shown in Figure 2-21. You will note that a single, double-plunger type pump serves all injector outlets. A single delivery valve is located in the rotor. A distributor type fuel injection pump witch is electronically controlled is sh

18、own in Fig.2-22. Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System Fig.2-22 A electronically controlled distributor type fuel injection pump. Fuel shutoff solenoid is controlled by the powertrain control module (PCM). When energized, it is designed to completely stop the fuel flow

19、 into the injection pump. Chapter 2 Internal Combustion Engine2.8 Diesel Fuel Injection System Injector. There are many different injector designs, but all are a variation of two basic types-inward opening and outward opening. Diesel spray patterns will vary depending upon engine design.Glow Plug an

20、d Intake Air Heaters.To aid in igniting the compressed air-fuel mix during cold starting, diesel engines use glow plugs and intake air heaters. The glow plug is an electrically operated device that protrudes into the precombustion chamber. On later engines, the glow plugs are turned on and off autom

21、atically. Intake air heaters warm the air as it passes through on its way to the intake manifold. The heater element is a wire mesh that is electrically heated. The computer energizes the heater element before cranking.Chapter 2 Internal Combustion Engine2.9 Common rail injection systems New Words C

22、hapter 2 Internal Combustion Engine 2.9 Common rail injection systems Newer diesel engines are equipped with common rail injection systems (Fig.2-23 to Fig.2-26). Common rail systems are direct injection (DI) systems. The injectors nozzles are placed inside the combustion chamber. The piston top has

23、 a depression where initial combustion takes place. The injector must be able to withstand the temperature and pressure inside the cylinder and must be able to deliver a fine spray of fuel into those conditions. These systems have a high pressure fuel rail connected to individual injectors. Chapter

24、2 Internal Combustion Engine2.9 Common rail injection systems The injectors are controlled by a computer that attempts to match injector operation to the operating conditions of the engine. There are two types of injectors: solenoid-type and piezoelectric (Fig. 2-27 and Fig.2-28). Newer diesel fuel injectors rely on stacked piezoelectric crystals rather than solenoids. Piezoelectric-crystals quickly expand when electrical curre