Fuel supply system of diesel plant

The fuel supply system of a diesel power plant receives, stores, cleans and delivers fuel oil to the engine cylinders in the right quantity, at high pressure and at the correct time.

 Tanker/rail -> unloading pump -> Main storage tanks
                                      |
                                transfer pump
                                      |
                                filter (strainer)
                                      |
                                  Day tank
                                      |
                               fine filter
                                      |
                            fuel (booster) pump
                                      |
                           fuel injection pump
                         (high pressure, metered)
                                      |
                       injectors -> engine cylinders

Components

1. Storage tanks: large tanks (above or below ground) holding about a month's fuel, filled from tankers through unloading pumps and strainers.
2. Transfer pump and strainer: move fuel from storage to the day tank after coarse filtering.
3. Day tank: small tank near the engine, holding about 8 hours' supply; often placed high so fuel flows by gravity.
4. Fine filters: remove dirt and water; dirty fuel blocks injector holes and wears pump plungers.
5. Fuel (booster) pump: feeds fuel to the injection pump at low pressure.
6. Fuel injection pump: plunger-type pump that raises pressure to about 100–200 bar (much higher in modern engines) and meters exact quantity per cycle as set by the governor.
7. Injectors (atomisers): spray fine fuel droplets into hot compressed air in the cylinder at the end of the compression stroke; the fuel ignites by itself.
8. Heaters (for heavy oil) and return lines from injectors back to the day tank.

Types of fuel injection systems

• Common rail system: one high-pressure pump keeps a common header at constant pressure; injectors open by timing.
• Individual pump system: separate pump for each cylinder; most common.
• Distributor system: one pump meters fuel and a distributor sends it to each cylinder in turn.

Requirements

• Accurate metering and timing; fine atomisation; quick start and stop of injection without dribble.