Crop Harvester

Introduction:

Overview of Diesel engine operation-
Diesel engine is (CI) compression ignited engine. It doesn’t use a premixed charge like SI engines. At the end of the compression stroke, liquid fuel is injected in the hot air present in the engine. The fuel injected at high velocity through one or more small orifices and nozzle, atomizes into small drops and penetrates into combustion chamber. The fuel vaporizes and mixes with hot air. Since temperature of air is above the ignition point of fuel spontaneous ignition of fuel-air mixture occurs after a delay period of few crank angle degrees.
Diesel injection: The function of a fuel injection system is to inject proper quantity of fuel into the engine cylinder at the correct time and at a predetermined rate. In case of multi-cylinder engines the injection system takes care of the sequence of injection in addition to the injection timing.
Conventional “Individual pump fuel injection system”: (Refer fig….)
This system uses in-line injection pump. Fuel is drawn from the fuel tank by means of a fuel feed pump which is operated from the injection pump camshaft. The fuel is then passed through a filter and then to the fuel injection pump. The fuel injection pump than, injects definite quantity of fuel into individual cylinders in turn according to firing order, through injectors fitted on them. This system is most commonly found on today’s diesel engine. However with the advent of stringent emission norms the system is bound to get outdated.
Brief Introduction of Common rail accumulator fuel-injection system.
In this system generation of pressure and fuel injection are completely decoupled from each other. The injection pressure is generated independent of injected fuel quantity. The fuel is stored under pressure in the high pressure accumulator ready for injection. The injected fuel quantity is defined by the driver, and the start of injection and injection pressure are calculated by the ECU on the basis of stored maps. The ECU triggers the solenoid valves so that the injector at each engine cylinder injects accordingly. Using the input signals from various sensors the ECU registers the drivers requirements and defines the instantaneous operating performance of the engine and the vehicle as a whole.

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