I. Diesel generatorBasic structure
The basic structure of a diesel generator is composed of a diesel engine and a generator, and the diesel engine is used as power to drive power generation machine to generate electricity.
The basic structure of a diesel engine: it consists of cylinders, pistons, cylinder heads, intake valves, exhaust valves, piston pins, connecting rods, crankshafts, bearings and flywheels. The diesel engine of the diesel generator is generally a single-cylinder or multi-cylinder four-stroke diesel engine. Let me talk about the basic working principle of a single-cylinder four-stroke diesel engine: the starting of the diesel engine is to rotate the crankshaft of the diesel engine by manpower or other power to make the piston in the top sealed cylinder. Reciprocate up and down. The piston completes four strokes in motion: intake stroke, compression stroke, combustion and work (expansion) stroke, and exhaust stroke. When the piston moves from top to bottom, the intake valve opens, and the fresh air filtered by the air filter enters the cylinder to complete the intake stroke. The piston moves from bottom to top, the intake and exhaust valves are closed, the air is compressed, the temperature and pressure increase, and the compression process is completed. When the piston is about to reach the top, the injector sprays the filtered fuel into the combustion chamber in a mist form and mixes with the high-temperature and high-pressure air, and immediately ignites and burns by itself. power stroke. After the power stroke is completed, the piston moves from bottom to top, the exhaust valve opens to exhaust, and the exhaust stroke is completed. Each stroke crankshaft makes half a revolution. After several working cycles, the diesel engine gradually accelerates into work under the inertia of the flywheel.
The rotation of the crankshaft of the diesel engine drives the generator to rotate and generate electricity. The generator includes a DC generator and an AC generator.
The DC generator is mainly composed of generator shell, magnetic pole iron core, magnetic field coil, armature and carbon brush. Working principle of power generation: When the diesel engine drives the generator armature to rotate, due to the residual magnetism of the magnetic pole core of the generator, the armature coil cuts the magnetic field lines in the magnetic field. According to the principle of electromagnetic induction, the magnetic induction generates current and outputs the current through the carbon brush. .
The alternator is mainly composed of a plurality of permanent magnets (called rotors) with alternating north and south poles made of magnetic materials and armature coils (called stators) made of silicon cast iron and wound with multiple series coils . Working principle of power generation: the rotor is driven by the diesel engine to cut the magnetic field lines axially, the alternately arranged magnetic poles in the stator form an alternating magnetic field in the coil iron core, the rotor rotates once, the direction and size of the magnetic flux change many times, due to the transformation of the magnetic field, Induced currents of varying magnitude and direction are generated in the coils and delivered by the stator coils.
In order to protect the electrical equipment and maintain its normal operation, the current sent by the generator also needs to be adjusted and controlled by a regulator.
Second, The working principle of diesel generators
In short, diesel power generation The machine drives the generator to run.
In the cylinder, the clean air filtered by the air filter is fully mixed with the high-pressure atomized diesel fuel injected from the fuel injection nozzle. Under the upward extrusion of the piston, the volume shrinks and the temperature rises rapidly , to reach the ignition point of diesel. The diesel fuel is ignited, the mixed gas burns violently, and the volume expands rapidly, pushing the piston down, which is called ‘work’. Each cylinder performs work in a certain order, and the thrust acting on the piston becomes the force that pushes the crankshaft to rotate through the connecting rod, thereby driving the crankshaft to rotate. By installing the brushless synchronous alternator and the crankshaft of the diesel generator coaxially, the rotor of the generator can be driven by the rotation of the diesel generator. Using the principle of ‘electromagnetic induction’, the generator will output the induced electromotive force, and the closed load loop will current can be generated.
Only the basic working principle of the generator set is described here. A series of diesel generators and generator controls, protection devices and circuits are also required to obtain a usable, stable power output.
Second, Diesel Generator Operating Procedures
One or more diesel generators operating without being connected to the grid is called islanding operation model. Working generators in parallel can achieve better efficiency at part load. An islanded power plant for mains power to an isolated community will typically have at least three diesel generators, any two of which are rated to carry the required load.
The generators can be electrically connected together through a synchronization process. Synchronization involves matching voltage, frequency and phase before connecting the generator to the system. Failure to synchronize prior to connection may result in high short-circuit currents or wear on the generator or its switchgear. The synchronization process can be done automatically by the automatic synchronization module, or manually by a guided operator. The automatic synchronizer will read the voltage, frequency and phase parameters from the generator and bus voltage while regulating the speed through the engine governor or ECM (Engine Control Module).
Load can be shared between generators operating in parallel through load sharing. Load sharing can be achieved by using a droop speed control controlled by the generator frequency while it constantly adjusts the engine fuel control to transfer load to or from the remaining power source. The diesel generator will take on more load when the fuel supply to its combustion system increases, and release the load if the fuel supply decreases.
