Common Rail Direct InjectionSystem Structure of Common Rail Direct Injection System 3. Conclusion 8. Reference . An insight to Cdi Engine 7. Introduction to Common Rail 2. Common Rail Injection System 4. Advantages 6.CONTENTS 1. Operating Principle 5. it is vital to determine how the 4 rate of injection from the common rail system compares to the rate of injection from a traditional injection system.COMMON RAIL DIESEL INJECTION INTRODUCTION Diesels known for their power handling capabilities acquired the title workhorse engines. When the rate of injection is the key to an effective combustion process. Diesel fuel is pressurized and injected into the combustion chamber through a fuel injector nozzle. and other construction equipment. especially in that the majority of them operate at constant load and speed most of the time. Diesel engines Petrol fuel is injected as an air/fuel mixture into the combustion chamber and ignited by the spark from spark plugs. . Petrol engines 2.. The common rail injection system is not capable of supplying all possible rate shapes. Traditional fuel injection systems for diesel engines are designed with the objective to secure acceptable fuel spray characteristics during the combustion process at all load conditions. just when the air in the chamber has been subjected to high pressure that it is hot enough to ignite the fuel spontaneously. tractors. buses. cranes. variable timing and duration of the injection. and trains. Medium speed diesel engines are different from the automotive diesel engines. not to mention large ships. Among the advantages claimed with respect to the common rail concept are injection rate shaping. There are basically 2 types of popular engines used in the world today: 1. Diesels may reside in heavy-duty trucks. lawn equipment and recreational vehicles. and rate shaping is mostly restricted to delivering a pre injection prior to the main injection. Incorrect injection causes reduced efficiency and increased emission of harmful species. Gasoline engines might dwell in the typical passenger vehicle. and the advantages of the more complicated common rail system may not be justified. in addition to variable injection pressure. bulldozers. enabling high injection pressure even at low engine loads. Tandem fuel pumps. In axial-piston and radial-piston distributor pumps. Throughout the vehicle’s service life. 3. Irrespective of operating state. 2. Particulate filtration:. Mechanically driven gear pump 3. With a minimum of noise.STRUCTURE OF COMMON RAIL DIRECT INJECTION SYSTEM The Common Rail Direct Diesel Injection system consists of the following parts: Injection nozzle: Injects fuel into the combustion chamber (for direct injection) or pre-combustion (for indirect injection). Water Separation: Two filters can also be fitted in parallel. Many pumps leed themselves automatically so that starting is possible even when fuel tank has run dry. Fuel Supply Pump: The fuel supply pump in low pressure stage is responsible for maintaining an adequate supply of fuel to the high pressure components. Functions of fuel filter are: 1. 2. Connecting the filter in series produces a higher filtration efficiency. . This applies: 1. There are three designs: 1. Pre-filter is fitted on the suction or pressure side if requirements are particularly high with a filter fineness matched to the main filter. resulting in greater particulate storage capacity. at necessary pressure. Fuel Filter: The service life design of the fuel injection system depends on a specific minimum purity of the fuel. electric fuel pump 2. a vane type supply pump is used as pre-supply pump and is integrated directly in the fuel injection pump. The fuel supply pump draws fuel out of the fuel tank and conveys it continuously in the required quantity to the high pressure fuel injection installation. 4. The Rail of Common Rail Injection System: The common rail is a modular system. This ensures that. In so doing accumulator volume has to dampen pressure fluctuations caused by fuel pulses delivered by the fuel pump and the fuel injection cycles. The high pressure fuel lines must withstand the systems maximum pressure as well as pressure variations that can attain very high fluctuations. In-line type 2. 3. when the injector opens the injection pressure remains constant. The lines are seamless precision made steel tubing in killed cast steel which has particularly consistent microstructure. High-pressure Line: In common rail systems. The pipe is made of steel as it has to withstand high pressures. 2.In-line type 2. Sealing cone and union nut 2. they serve as the connection between the high pressure pump and the rail and from rail to the injector. and can therefore be easily adapted for different engines. Mechanically controlled fuel injection pumps are available as: 1. The following types of fittings are used: 1. They have been around the longest and include Camshaft-Less (PFR) types. Distributor type Electronically controlled fuel injection pumps are available as: 1. Perpendicular connection fittings. Heavy duty insert fittings 3. Fuel injection pumps: Diesel fuel injection pumps are generally divided into two categories: 1. the fuel rail also distributes fuel to the injectors. The function of the high pressure accumulator is to maintain the fuel at high pressure. Distributor type Common Rail type Mechanically controlled fuel injection pumps: In-line Fuel Injection pumps have the same number of plungers as cylinders in the engine. . Besides acting as fuel accumulator. thereby resulting in fine and accurate control. thereby resulting in fine and accurate control. fuel injection quantity and injection timing are controlled electronically. Unlike conventional mechanical control. fuel injection quantity and injection timing are controlled electronically. High-pressure stage of the radial-piston distributor injection pump: . Electronically controlled fuel injection pump: An electronically controlled fuel injection pump utilizes a microcomputer to control fuel injection quantity and injection timing according to running conditions of the engine.Electronically controlled fuel injection pump: An electronically controlled fuel injection pump utilizes a microcomputer to control fuel injection quantity and injection timing according to running conditions of the engine. It can be referred to as Electronic Control Diesel or ECD. Unlike conventional mechanical control. It can be referred to as Electronic Control Diesel or ECD. The guide slots simultaneously act as the locating slots for the roller supports. As the roller supports are forced outwards by centrifugal force. The nozzle is designed to atomize the fuel to make as fine am mist as possible so that it can burn easily. allowing the pressurized fuel to squirt out through a tiny nozzle. they also require more power to drive themThe radial-piston high-pressure pump is driven directly by the distributor Pump driveshaft. Injector: A fuel injector is nothing but an electronically controlled valve. the delivery plungers follow the profile of the cam ring and describe a cyclical reciprocating motion. The drive plate drives the distributor shaft. The roller supports and the rollers held by They run around the inner cam profile of the cam ring that surrounds the drive shaft. Consequently.Radial-piston high-pressure pumps produce higher injection pressures than Axial-piston high-pressure pumps. The nozzle is kept closed by the rail pressure . The delivery plungers rest against the roller supports. The head of the distributor shaft holds the delivery lungers which are aligned radially to the drive-shaft axis (hence the name “radial-piston high-pressure pump”). an electromagnet moves a plunger that opens the valve. Different types of injectors are Solenoid Valve Injector: When the injector is energized. Piezo-Inline Injector: The nozzle needle on piezo-inline injector is controlled indirectly by servo valve. and it is capable of opening and closing many times per second. The main pump components are the cam ring the roller supports rollers the delivery plungers the drive plate the front section (head) of the distributor shaft The drive shaft drives the drive plate by means of radially positioned guide slots. It is supplied with pressurized fuel by the fuel pump in your car. The required injected fuel quantity is then controlled by the valve triggering period. The number of cams corresponds to the number of cylinders in the engine. This is called the pulse width. Electronic Control Unit: An Engine Control Unit (ECU). The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open.exerted in the control chamber. This is called the pulse width. The range of tasks performed by the engine control unit includes the following functions: Common-rail injection Delivery control of the high-pressure pump Engine speed limitation Deceleration fuel cut-off Fuel pump Air supply Drive control Diagnosis . and it is controlled by the ECU. The main component on this circuit board is a microcontroller chip (CPU). The software is stored in the microcontroller or other chips on the PCB. typically in EPROMs or flash memory so the CPU can be re-programmed by uploading updated code. which reads several sensors in the engine and uses the information to control the ignition systems of the engine. This is also referred to as an (electronic) Engine Management System (EMS). that is part of an internal combustion engine. The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. When the piezo actuator is triggered. also known as Engine Management System (EMS) is an electronic device. fundamentally a computer. The hardware consists of electronic components on a printed circuit board (PCB). There are two main types of control for multi-port systems The fuel injectors can all open at the same time. An electronic control unit contains the hardware and software (firmware). and it is controlled by the ECU. Each one can open just before the intake valve for its cylinder opens (this is called sequential multi-port fuel injection). the serve valve opens and closes the bypass passage. Common-rail technology is intended to improve the pulverisation process. which lies at the heart of an innovative quick-start low system.A separate data network links the engine management system with the generator and the glow control unit. thus pulverise. The main components on the rail assembly are: 1. the fuel must be injected at a very high pressure. pioneered Common Rail Direct Injection for diesel engines. This shortens the preheating time for the engine to just a moment. More Torque. Less Emission and Less Noise. The high-pressure fuel is fed to . so high that normal fuel injectors cannot achieve. lower fuel efficiency and less power. more Imperfect pulverisation leads to more unburnt particles. Filter unit To improve pulverisation. Nothing ‘COMMON’ About It. While the Japanese are leading in petrol direct injection technology. Electronic control unit (ECU) 6. Inlet metered high-pressure supply pump with integrated lift pump 4. Compare with petrol. High pressure regulator (option) 3. so hat the diesel is now also the equal of a petrol engine in this respect. Injectors 5. Germany's Bosch. working in conjunction with several European car makers. Common pressure accumulator (the “rail”) 2. The rail assembly used in CRDi is as shown in figure. diesel is the lower quality ingredient of petroleum family. Diesel particles are larger and heavier than difficult to petrol. the fuel pressure is implemented by a strong pump instead of fuel injectors. In common-rail system. hence more pollutant. the high-pressure fuel can be injected into combustion chamber quickly. the pipe withstand the pressure as high as 1.000 psi. but the duration of fuel injection can be shortened and the timing can be precisely controlled. The pressure in the system is controlled by the actuator. Exceptions are the exhaust-gas treatment sensors and the rail pressure sensor as their installation positions are required to understand the system. which injects small amount of fuel during the expansion phase thus create a small scale combustion before the normal combustion takes place. and the duration of injection can be freely chosen from a wide range. The figure shows all the components in a common rail system for a fully equipped. Benefited by the precise timing. Fuel always remains under such pressure even in stand-by state.350 bar or 20. In the current first generation design. Data exchange between the various sections takes place via the CAN bus in the interfaces suction: • Starter Motor • Alternator • Electronic Immobilizer . As a result. which is adjusted depending on engine needs. Depending on the type of vehicle and its application. The sensors and setpoint generators are not depicted in their real installation position to simplify presentation. some of the components may not be fitted. the actual start of injection.individual fuel injectors via a common rigid pipe (hence the name of "common-rail").The introduction of pilot injection. OPERATING PRINCIPLE A feed pump delivers the fuel through a filter unit to the high pressure pump through feed pipe. common-rail injection system can introduce a "postcombustion". The high-pressure pump delivers fuel to the high-pressure accumulator (the rail). The electronically controlled injectors inject fuel into the combustion chamber when the solenoid valve is actuated. Therefore whenever the injector (which acts as a valve rather than a pressure generator) opens. results in significant engine noise reduction. not only pulverisation is improved by the higher fuel pressure. Because the injection pressure is independent of engine speed and load. 4 cylinder. together with a reduction in NOx emissions. passenger car diesel engine. the injection pressure. • Transmission control • Traction Control System • Electronic Stability Program System Diagram For Passenger Cars . and the rate at which this pressure rises during the combustion process normally produce higher noise levels in direct injection engines than in their pre-chamber (indirect injection) counterparts.ADVANTAGES -More power is developed -Increased fuel efficiency -More stability -Pollutants are reduced -Particulates of exhaust are reduced -Exhaust gas recirculation is enhanced -Precise injection timing is obtained -Pilot and post injection increase the combustion quality -The powerful microcomputer makes the whole system more perfect AN INSIGHT INTO THE CDI ENGINE Pilot Injection Feature: The high combustion pressure of up to 145 bar (2130 psi) in the CDI engine. . com .CONCLUSION CRDI technology revolutionized diesel engines.technolog. It has changed the way one looks as diesel cars by providing the above said advantages.co.in www.crdi. REFERENCES: http/www.google.