Air Injection and Solid Injection System
- 1. GANDHINAGAR INSTITUTE OF TECHNOLOGY MECHANICAL DEPARTMENT INTERNAL COMBUSTION ENGINE
- 2. CONTENT :- • Introduction • Classification of Injection System • Air Injection • Solid Injection & Airless Injection
- 3. INTRODUCTION :- • Fuel-Injection System is vital to the working and performance of CI engine. This system serves the purpose of initiating and controlling the combustion to meet the demand requirements. • Fuel is injected into combustion chamber towards the end of compression. It is atomized as it enters under high velocity and the droplets get vaporized to form a fuel-air mixture. Due to continued heat transfer from hot air to fuel, the fuel reaches to its self ignition temperature to ignite spontaneously initiating combustion. Depending upon the demand requirements the fuel injection system continues to deliver the fuel during initial part of combustion.
- 4. Classification Injection System Air Injection Solid or Airless Injection Common rail system Individual pump and injector system Distributor system
- 5. AIR INJECTIONSYSTEM :- In this system fuel is injected along with high pressure air into combustion chamber. The pressure of this air is about 70 bar. A multistage air compressor is required to supply the blast of air at high pressures. A fuel pump draws fuel from fuel tank through a filter and discharge a definite quantity into an injector. The high pressure air from compressor is also led to the injector valve which force the fuel, through the nozzle, when it is opened mechanically. This type of system is not used now-a-days in diesel engines.
- 6. Advantages:- It provides good atomization and distribution of fuel. Fuel pump needs to develop less pressure. Disadvantages:- It requires high pressure multi stage compressor. Air compressor needs extra maintenance.
- 7. SOLID INJECTON &AIRLESS INJECTION SYSTEM :- In solid Injection system , fuel is directly injected into the cylinder without aid of compressed air. That’s why this system is called solid or airless injection system. Fuel is supplied at very high pressure (about 200 bar) from fuel pump to fuel injector from where it is injected to the combustion chamber with the help of injector. There are three types as: 1.Common rail system 2.Individual pump and injector 3.Distributor injection system
- 8. COMMON RAIL INJECTION SYSTEM :- In this system, single fuel pump supplies high pressure diesel oil to common rail or header. High pressure in the header forces fuel to each of the nozzle. At given instant, the fuel is injected in a specific cylinder by a mechanically operated valve, by means of a push rod and rocker arm. The amount of fuel is regulated by varying the length of the push rod stroke. The pressure in header is as per injector design for penetration & dispersion of fuel in combustion chamber.
- 9. Advantages:- It can control fuel supply according to load and speed of the engine. Only one pump is required for multi cylinder engine. The arrangement of system is very simple & Maintenance cost is less. Disadvantages:- Very accurate design and workmanship is required.
- 10. INDIVIDUAL PUMP & INJECTOR :- In this system , individual fuel pump is provided for each nozzle. The metering of fuel quantity and control of injection timing are done by the each pump for corresponding nozzle. The needle valve in nozzle is actuated by fuel oil pressure. The amount of fuel entering the cylinders is regulated by changing position of control rack.
- 11. DISTRIBUTOR INJECTION SYSTEM :- In this system, the pump is used to pressurizes, meters and times the injection. Then fuel is supplied to central distributor block. From distributor block fuel is distributed to each cylinder in correct firing order by cam operated poppet valves which open to admit fuel to nozzles. The amount of fuel to entering the cylinders is regulated by changing position of control rack. The number of injection strokes per cycle for the pump is equal to the number of cylinders.
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