The working principle of a diesel generator set involves the coordinated operation of a diesel engine and generator to progressively convert the chemical energy of diesel fuel into electrical energy. The specific process is as follows:
I. Diesel Engine: Converting Diesel Energy into Mechanical Energy
The diesel engine operates through a four-stroke cycle: “intake, compression, power, exhaust”.
1. Intake Stroke: The piston moves downward, drawing in air (diesel engines do not require fuel intake).
2. Compression Stroke: The piston moves upward, compressing the air to significantly increase its temperature and pressure (temperatures can reach 500–700°C).
3. Power Stroke: The injector sprays diesel fuel into the cylinder. The fuel ignites spontaneously upon contact with the hot air, generating high-pressure combustion gases that push the piston downward. This motion drives the crankshaft via connecting rods, outputting mechanical energy (crankshaft speed typically ranges from 1500 to 3000 rpm).
4. Exhaust Stroke: The piston moves upward, expelling the spent combustion gases to prepare for the next cycle.
II. Generator: Converting Mechanical Energy into Electrical Energy
Driven by the diesel engine, the generator produces electricity through electromagnetic induction:
 Rotor Rotation: The diesel engine drives the generator's rotor (equipped with magnets or excitation windings) to spin at high speed, creating a rotating magnetic field.
 Stator Generation: The stationary stator windings cut through the magnetic field lines of the rotating field, inducing alternating current (AC).
 Voltage Regulation: The excitation system adjusts magnetic field strength to ensure stable output voltage (e.g., 220V/380V).
 Frequency Stability: Generator speed must remain constant (e.g., 1500 rpm commonly used domestically) to maintain output frequency at 50Hz.
III. Auxiliary Systems: Ensuring Stable Unit Operation
Fuel System: Stores and delivers diesel fuel to the engine injectors.
Cooling System: Lowers engine and generator temperatures via water or air cooling.
Lubrication System: Supplies lubricating oil to moving parts, reducing wear.
 Control System: Monitors parameters like RPM, voltage, and frequency in real time. Automatically shuts down during faults such as overload or low oil pressure, and enables automatic start/stop or remote monitoring functions.
IV. Overall Operational Logic
1. Start-up: Engages the battery-powered starter motor to rotate the diesel engine crankshaft until diesel combustion occurs, allowing the unit to run autonomously.
2. Power Generation: The diesel engine drives the generator to produce electricity, which is regulated and output externally.
3. Shutdown: Fuel supply is cut off. After the unit idles and cools, the electrical circuit is disconnected.
Diesel generator sets are widely used in scenarios requiring emergency backup power (e.g., hospitals, data centers), mobile operations (e.g., construction sites), and independent power supply in remote areas. Their advantages include rapid startup, stable power delivery, and adaptability to complex environments.