04-05-2012, 03:17 PM
Electronic control systems for diesel injection
8c. CRDI engines.ppt (Size: 1.33 MB / Downloads: 96)
Mechanical control systems have proven their reliability and precision for many years.
The first electronic diesel control (EDC) was used in 1983 with distributor pumps which used electronic controls:
It is possible to adjust the start of injection more accurately and flexibly according to the engine requirements.
Electronic control systems improves fuel economy and reduce the amount of pollutants in the exhaust.
In overall the electronic control systems has provided greater degree of flexibility and accurate control in many key parameters like;
Types of Injection System
Diesel injection systems - two types
Air injection system ( 60-70 bar)
Air less injection system- solid injection for high pressure system
Air less injection system- solid injection
Individual pump & injector or jerk pump system
Common rail system
Distributor system
Common-Rail Direct Injection (CRDI)
The manner in which fuel is injected into the cylinder determines the engine's torque, fuel consumption, emission and noise level.
Critical factors which influence the Injections are;
Injection pressure.
Shape of injector and no of holes
No. of injections
Imp. components are:
High Pressure Pump- For generating high pressure fuel in the rail.
Rail- Reservoir of high pressure fuel.
Injectors- Inject the required amount of fuel into the combustion chamber.
Electronic Control Unit (ECU)- Acts as a control center with inputs from a number of sensors.
Requirement for CRDI:
Common rail with electronic control unit eliminate the problems associated with interconnecting pipes in traditional pump-line-injector systems.
CRDI have scope for pilot injection and more desirable injection pressure characteristics.
Pilot injection means: It is an additional small amount of fuel injection before the power producing main fuel pulse.
Modern engines use a pilot injection before the power producing main fuel pulse. This smoothens the pressure spike and dramatically reduces the engine noise.
Pilot injection also reduces peak combustion temperature which helps to reduce NOx emissions drastically.
It means it controls the amount of fuel injected during the ignition delay period