A diesel generator is a diesel powered machine capable of converting mechanical energy to electrical energy. It basically consists of a diesel engine, who's drive shaft is directly connected to something called an alternator. The job of the alternator is to convert the mechanical energy provided to it by the diesel engine to electrical energy. So the alternator consists of 2 windings called the stator winding and the rotor winding. During operation the stator winding is stationary while the rotor winding are performing circular motion (since they are connected to the drive shaft of the diesel engine).
Working Of The Alternator:
The rotor windings are excited by some DC current so that a magnetic field is produced around the coil. Since it is performing circular motion the magnetic flux linked with it also keeps performing circular motion at the same speed. This magnetic flux is intersected by the stator winding which is fitted around the rotor. According to Faraday's Law since the stator coil is subjected to change in magnetic flux,an E.M.F. is developed at the ends of the stator coil(which is our output). So basically the battery provides DC current to excite the rotor coil and create a magnetic field and hence generate electric energy. This current is supplied by slip rings which are on the rotor.
At times a DC generator is connected to the end of the rotor coil to excite the coil. Such types of alternators are called self excited.
Just a like a car, the diesel engine uses a closed loop liquid cooling system. A pump turned by the engine pumps coolant through channels in the engine to collect heat. At the end of the loop is a radiator with many small tubes and fins to help it dissipate the heat. The radiator “radiates” the heat.
A fan blows air through the radiator which moves the heat away from the radiator and the coolant. It’s fairly efficient system. Liquid coolants easily absorb heat from the heavy engine and use moving air to dissipate the heat, thus keeping the diesel generator cool.
One of the inefficiencies of an internal combustion engine is the blow by of hot gasses during combustion. The pressure inside the cylinder rises dramatically as the fuel mixture burns rapidly. The pressure drives the piston down.
The combustion chamber is sealed by the valves and by the rings on the piston. However, the piston rings and valves are an imperfect seal. Some of the hot gases blow by and enter the crankcase and valve cover. When these hot gases cool they turn into sludge, a thick byproduct of the combustion process.
In early engines, nothing was done to combat sludge. Engines leaked oil and the sludge leaked with it through gaskets and bearings. Later engines incorporated a draft tube. As moving air passed over the tube, such as when a vehicle was moving, it created suction which pulled the blow-by gases from the crankcase.
This didn’t work for stationary engines. Further, it was discovered in the 1950s that crankcase gases were major component of smog—unburned hydrocarbons.
Positive Crankcase Ventilation was implemented on vehicles as a way to combat smog. A valve connects the crankcase to the air intake. Unburned hydrocarbons are routed back through the engine to burn instead of entering the atmosphere.
This is where the “breather” comes into play. In order for the PVC valve to pull fumes from the crankcase (usually through the valve cover) it needs a source of fresh air. The “breather” is an inlet tube that connects the crankcase to the air filter.
The PVC valve uses intake manifold pressure (suction) to pull fumes from the crankcase. You can’t suck air through a straw if your finger is over the end, but remove your finger and it’s easy to suck air through it. The breather tube is like taking your finger off the straw - it allows air to enter the crankcase so the PVC valve can suck the fumes out.
When intake manifold pressure spikes, the PVC valve may close. The breather now acts in reverse. Pressure in the crankcase forces the unburned gases back through the breather tube to the air intake where they enter the fuel-air mixture and are burned.
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