A diesel generator produces electricity by burning diesel fuel to generate mechanical energy, which is then converted into electrical power through an alternator. In this process, air is compressed, fuel is injected, combustion occurs, and the resulting motion of the pistons drives the crankshaft—ultimately producing electrical energy.
| Step | Description |
|---|---|
| 1. Fuel Injection and Combustion | Diesel fuel is injected at high pressure and ignites from the heat of compression. |
| 2. Piston Movement | Expanding gases push the pistons, creating reciprocating motion. |
| 3. Crankshaft Rotation | The linear motion is transferred to the crankshaft, turning it into rotational energy. |
| 4. Power Generation | The rotor spins within the stator, generating AC power through electromagnetic induction. |
| 5. Voltage Regulation | The AVR keeps voltage and frequency stable and can convert AC to DC if needed. |
Fuel Injection and Combustion in the Cylinder
Fuel Injection:
A high-pressure pump injects atomized diesel fuel into the cylinder.
Compression:
The piston compresses air inside the cylinder, raising pressure and temperature to around 500–700 °C, sufficient for self-ignition.
Combustion:
When the fuel reaches its ignition temperature, it burns spontaneously (without spark plugs), producing powerful expansion that pushes the piston downward.
According to Pleavin Power (UK),
“A diesel generator creates electricity by converting mechanical energy into electrical power. It channels this energy through power cables, similar to how water flows through pipes. It doesn’t create or destroy electrons—it simply enables their movement in a controlled manner.”
Piston Motion and Mechanical Energy Production
The expanding gases push the piston down in each power stroke, while exhaust and intake valves open alternately.
This reciprocating motion is converted into rotational energy through the crankshaft, forming the mechanical energy that drives the alternator.
Crankshaft Rotation and Power Transfer to the Alternator
The crankshaft is connected to the alternator shaft via a coupling or gear reducer, ensuring optimal rotational speed for efficient power generation.
As the crankshaft rotates, it transfers mechanical torque to the rotor of the alternator.
Electromagnetic Induction (Rotor–Stator Interaction)
Alternator Components:
Rotor: Rotating magnetic field
Stator: Stationary coils of wire
Faraday’s Law:
When the rotor spins inside the stator, it changes the magnetic flux across the coils, inducing an alternating current (AC).
Voltage and Frequency:
The number of poles and rotational speed determine the output voltage (e.g., 380–400 V three-phase) and frequency (50 or 60 Hz).
Voltage Regulation by AVR (Automatic Voltage Regulator)
The AVR controls the excitation current of the rotor to maintain constant output voltage even when load demand fluctuates.
In some configurations, the AC output may be converted to DC, but most generators produce AC for direct use in residential or industrial applications.
✅ Key Technical Insights
The diesel engine relies on compression ignition, not spark plugs (unlike gasoline engines).
The AVR ensures stable voltage and frequency under variable loads.
The overall process involves three stages of energy conversion:
Chemical → Thermal (combustion)
Thermal → Mechanical (piston and crankshaft movement)
Mechanical → Electrical (alternator generation)
