The advantages of the diesel engine are: fuel-efficient, environmentally friendly, strong power, convenient and economical maintenance, as long as it has a larger address the shortcomings of market prospects, electrically controlled diesel generator program now appears to be a good solution measures. As people’s awareness of environmental protection and energy saving “style =” float: right; clear: both; top: 0; vertical-align: top; “>
The advantages of the diesel engine are: fuel-efficient, environmentally friendly, strong power, convenient and economical maintenance, as long as it has a larger address the shortcomings of market prospects, electrically controlled diesel engine program now appears to be a good solution measures. With the people’s awareness of energy conservation and environmental protection has been strengthened to diesel engine technology requirements are also increasing. These requirements are: to improve dynamic performance while reducing fuel consumption and reduce exhaust pollution. Achieve these goals, the accuracy and precision diesel fuel injection system put forward higher requirements. Meet these requirements are four injection technology unit pump, pump nozzle, dispensing pumps and high-pressure common rail system (Figure 1), are described below.
Figure 1 – The four modern diesel fuel injection technology
1. Unit Pump technology
Consists of a single pump plunger and plunger sleeve constituted itself, without camshaft, some even without a wheel drive components. Because of this ease of single pump is disposed in the cylinder head near the site, greatly reducing the high-pressure tubing, currently used in a bore of 200mm or more in high-power, low-speed diesel engine. As BFM1013 Deutz series diesel engine is the use of unit pump fuel injection system. (Editor: China full power) 2. Pump nozzle technology (Figure 2) is to improve the excellent mixture of diesel diesel power, fuel economy; reduce emission rates, a key factor in the rate of noise. This requires the injection system to produce a sufficiently high injection pressure, “style =” float: right; clear: both; top: 0; vertical-align: top; “>
2. Pump nozzle technology (FIG. 2)
An excellent mixture to improve diesel diesel power, fuel economy; a key factor in reducing the rate of emissions, noise ratio. This requires the injection system to produce a sufficiently high injection pressure to ensure good fuel atomization, and also must be precisely controlled fuel injection starting point and injection quantity. The pump nozzle systems can meet the stringent requirements mentioned above. Thus, as early as 1905, the founder Mr. Rudolf diesel diesel diesel pump injector proposed the concept envisaged injection pump and nozzle in one, eliminating the need for high-pressure pipeline and obtain high injection pressure. 1950s, intermittent control pump diesel injection systems used in diesel engines already on the boat and truck wheel. After, Volkswagen and Robert Bosh AG companies developed to apply to passenger cars solenoid valve controls the pump injection system. The role of the main components of the pump nozzle is as follows:
(1) one-way valve: When the diesel engine does not work, to prevent the fuel return.
(2) the bypass valve: If the air in the fuel is discharged through here.
(3) orifice and filter: collection, separation of tubing for air bubbles.
(4) pressure limiting valve 1: adjusted for within the rail pressure is greater than 0.75MPa open.
(5) pressure limiting valve 2: to maintain the internal pressure in the return pipe 0.10MPa.
(6) Fuel pump: Fuel pump vane pump is intermittent, the advantage is at low speed diesel oil are also available. Pump body pump rotor oil passage so that the fuel is always in the state of infiltration, which can at any time delivery of fuel.
Figure 2 – Bosch pump nozzle
(7) the fuel distribution pipe integration: fuel distribution pipe is integrated in the cylinder head for the pipeline, whose function is to allocate the same amount of each fuel pump nozzle, in this fuel and heating fuel mixture, and was forced back into the supply pump nozzle tubing. So that for each cylinder fuel flow consistent temperature within the tubing. All pump nozzles are provided the same amount of fuel, so that the diesel engine running smoothly. Otherwise, the oil pump nozzle will be different, and the fuel pump nozzle is provided different quality. This will make the diesel engine is not running smoothly and produce extremely high temperatures the first few cylinders.
(8) Fuel cooling pump: cooling liquid circulating in the cooling loop. When the fuel temperature reaches 70 ℃, diesel engine control unit through the fuel cooling pump relay turn it on.
Using a pump nozzle on many domestic passenger car, such as: Bora TDI, Audi TDI Touran TDI and the like. Pump nozzle technology with respect to the prior art (eg piston), it has been significantly improved and its biggest advantage is that greatly increased the fuel injection pressure, the turbo booster pump nozzle injection pressure can reach 200MPa or more. Since the injection pressure acting directly affect diesel combustion efficiency, combustion efficiency pump nozzle is very high. (Editor: China full power) 3. Common Rail technology (Fig. 3) due to the diesel engine load and speed regulation is without intake throttling directly by varying the amount of fuel injection to achieve, so the fuel injection system must at a pressure of 35 ~ 200MPa between the “style =” float: right; clear: both; top: 0; vertical-align: top; “>
3. The high pressure common rail technology (Fig. 3)
Since the diesel engine load and speed regulation is without intake throttling directly by varying the amount of fuel injection to achieve, so the fuel injection system pressure must be between 35 to 200MPa fuel injected into the diesel engine cylinder and form uniform combustible mixture. During the fuel injection quantity measurement must be as accurate as possible, fuel injection during injection pressure, injection timing and injection frequency control must be very flexible, and must be able to operate with the working conditions and any changes. Therefore, continue to use the lower adjustable mechanical fuel injection system or injection pressure control function is limited electronically controlled dispensing pump has been unable to meet these requirements, the new electronically controlled high pressure common rail fuel injection system is the best choice. In recent years, therefore, electronically controlled high pressure common rail injection system in the vehicle diesel engine has been rapid promotion. So far, electronically controlled high pressure common rail injection system has developed three generations.
Figure 3 – High Pressure Common Rail Diesel Injection System
The first generation of common-rail high-pressure pump is always kept at maximum pressure, resulting in wasted fuel and high fuel temperature. The first generation of common rail system for the commercial vehicle design, the maximum injection pressure of 140MPa, passenger injection pressure of 135MPa.
Second-generation common-rail diesel engine system according to the needs of changing output pressure, and having a pre-injection and post-injection capabilities. With control of fuel pumps, injection pressure can reach 160MPa. Even at low pressure, the system can also provide the right amount of fuel injection pressure according to the actual situation. Not only helps to reduce fuel consumption, but also reduce the fuel temperature, thereby eliminating the need for fuel cooling means. Pre-injection diesel engine reduces noise: In the main injection millionth of a second before a small amount of fuel is sprayed into the cylinder compression ignition, preheat the combustion chamber. After preheating the cylinder so that the main injection after a compression ignition easier, the in-cylinder pressure and temperature increase abruptly no longer conducive to reduce combustion noise. After injection during expansion, secondary combustion, increasing the cylinder temperature 200 ~ 250 ℃, reducing the exhaust gas hydrocarbons. Bosch’s second-generation common rail system on the product has been tested in the Volvo S60, V70D5 and BMW 230d and other passenger cars. (Editor: China full power) third-generation common rail system with piezo inline injectors. In 2003, third-generation common-rail system available, a piezoelectric actuator piezoelectric (piezo) common rail system instead of the solenoid valve, thereby obtaining a more precise injection control “style =” float: right; clear: both; top: 0; vertical-align: top; “>
Third-generation common rail system with piezo inline injectors. In 2003, third-generation common-rail system available, a piezoelectric actuator piezoelectric (piezo) common rail system instead of the solenoid valve, thereby obtaining a more precise injection control. Eliminating the return pipe, the structure is simpler. Flexible pressure adjustment from 20 ~ 200MPa. The minimum injection quantity can be controlled in 0.5mm3, reduces smoke and NOX emissions. The maximum injection pressure reached 180MPa. This sets using a newly developed piezo inline injectors makes the system after spray and spray with pre-injection rate curve range more freely.
About electronically controlled high pressure common rail fuel injection system of the book details, see Chapter 4: Structure and maintenance of diesel electric controlled common rail fuel injection system.
4. The dispensing pump fuel supply system (Fig. 4)
Distribution injection pump DIP (Distributor Injection Pump), referred to as the dispensing pump, in the late 1980s introduced a new era in lightweight and compact high-performance injection system. Today, Bosch already enumerating generations dispensing pump an upgrade, the latest 4th generation product dispensing pump VP30 and VP44 radial axial dispensing pump maximum injection pressures of up to 1550 bar and 2000 bar. Enhance the high injection pressure nozzle gasification (atomization) effect, thereby reducing fuel consumption and emissions. At the same time, by integrating pre-injection function, the new Bosch dispensing pumps can help reduce the noise of diesel vehicles and diesel vehicles to improve ride comfort. Bosch dispensing pumps for passenger cars and medium commercial vehicles and diesel injection systems, such as FAW-Volkswagen Jetta and Audi A6 and the like.
Figure 4 – dispensing pump fuel supply system (Editor: China full power) 5.EGR exhaust gas recirculation technology (Fig. 5) action (1) EGR: The exhaust gas recirculation (EGR) system for reducing emissions of nitrogen oxides ( NOx) in emissions. Only nitrogen and oxygen at high temperature and pressure conditions will occur chemical reaction “style =” float: right; clear: both; top: 0; vertical-align: top; “>
5.EGR exhaust gas recirculation technology (Fig. 5)
(1) EGR effect:
Exhaust gas recirculation (EGR) system for reducing emissions of nitrogen oxides (NOx) in emissions. Only nitrogen and oxygen at high temperature and pressure conditions will occur chemical reaction, the diesel engine combustion chamber temperature and pressure to meet the above conditions, especially during acceleration mandatory.
Figure 5 – Electronically Controlled Diesel Engine EGR system
When the diesel engine running under load, EGR valve opening, a small amount of exhaust gas into the intake manifold, and the combustible mixture into the combustion chamber together. Idling EGR valve is closed, almost no exhaust gas recirculation to diesel engines. Automobile exhaust is a non-combustible gas (excluding fuel and oxidizer), does not participate in the combustion in the combustion chamber. It does this by absorbing some of the heat generated by the combustion pressure and combustion temperature to decrease to reduce the amount of nitrogen oxides. The amount of exhaust gas into the combustion chamber with the increase in engine speed and load increases.
(2) How it works:
The main components of the EGR system is digitally controlled EGR valve. Digitally controlled EGR valve is mounted on the right exhaust manifold, whose role is independently to the diesel engine exhaust gas recirculation amount for accurate control, regardless of the size of the vacuum manifold.
EGR valve aperture through three incremental metering orifice to control the amount of exhaust gas back into the intake manifold from the exhaust manifold to produce seven kinds of different combinations of traffic. Each metering orifice by a solenoid valve and needle composition, when the solenoid valve is energized, the armature magnet it is attracted upward, so metering Kong Kaiqi. Characteristics of the rotary needle valve ensures that when the EGR valve is closed, has a good seal.
EGR valve is usually open under the following conditions:
① diesel engine warm-up operation. ② more than idle speed. According to ECM diesel engine cooling water temperature sensor, throttle position sensor and air flow sensor to control the EGR system.