Power Plant Engineering

1. COMMON RAIL INJECTION
A typical common rail injection system is shown in Fig. 8.4. It incorporates a pump with built in
pressure regulation, which adjusts pumping rate to maintain the desired injection pressure. The function
of the pressure relief and timing valves is to regulate the injection time and amount. Spring-loaded spray
valve acts merely as a check. When injection valve lifts to admit high-pressure fuel to spray valve, its
needle rises against the spring. When the pressure is vented to the atmosphere, the spring shuts the
valve.

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POWER PLANT ENGINEERING
2. INDIVIDUAL PUMP INJECTION
In this system, each fuel nozzle is connected to a separate injection pump, Fig.8.5. The pump
itself does the measuring of the fuel charge and control of the injection timing. The delivery valve in the
nozzle is actuated by fuel-oil pressure.
Pressure
Relief
and Timing
Valve
Spring Loaded
Spray Valve
Fuel Lines to
other Cylinder
Control
Lever
Cam Shaft
Accumulator
Pump Drive Shaft
Fuel From
Day Tank
Controlled Pressure Pump
Control Rod
Pump Shaft
Injection
Pump
Injection Nozzles
 Fig. 8.4. Common Rail Injection.
Fig. 8.5. Individual Pump Injection.
3. DISTRIBUTOR SYSTEM
This system is shown in Fig. 8.6. In this system, the fuel is metered at a central point i.e., the
pump that pressurizes, meters the fuel and times the injection. From here, the fuel is distributed to
cylinders in correct firing order by cam operated poppet valves, which open to admit fuel to nozzles.
Distributor
Block
Nozzles
Metering
and Pressure
Pump
Control Rod
Cam
Cams
Primary Pump
Fig. 8.6. Distribution System.