--- title: "Diesel layout, starting and fuel supply systems" subject: "Power Plant Equipment" chapter: 5 key: "semester_7/power_plant_equipment:diesel-layout-starting-fuel" source: https://www.bctengineer.com/q/semester_7/power_plant_equipment/diesel-layout-starting-fuel site: BCT Engineering --- # Diesel layout, starting and fuel supply systems Power Plant Equipment · Chapter 5: Diesel Power Plant - Asked in: 2079 Baisakh, 4+2+2 marks - Video: [Diesel Power Plant || working and layout || Diesel Engine](https://www.youtube.com/watch?v=ly9CI9nXaC8) — Aeran Classes - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/power_plant_equipment/diesel-layout-starting-fuel - Whole chapter: https://www.bctengineer.com/md/semester_7/power_plant_equipment/chapter-5 ## Question Draw a neat sketch of general layout of Diesel Power Plant with all major components. Explain the starting system and fuel supply system as well. ## Short answer Major components are engine, alternator, air intake, fuel supply, exhaust, cooling, lubrication, starting, and governing systems. Starting uses compressed air from bottles, an electric starter motor, or a small auxiliary engine. Fuel flows from bulk tank through filters to day tank, then to injection pump and injectors; excess fuel returns to the day tank. ## Answer A **diesel power plant** uses a compression-ignition (CI) engine coupled to an alternator. Air compressed in the cylinder becomes hot enough to ignite the injected fuel; the engine's shaft power is converted to electrical power by the alternator. Plants are usually 2–50 MW and are used for standby, peak load and isolated supply. #### General layout ```text Bulk tank -> Filter -> Day tank -> Inj. pump | v Air filter -> Supercharger -> +--------+ | DIESEL |==> ALTERNATOR Comp. -> Air bottle --------> | ENGINE | +--------+ | | | Lube tank, filter, cooler-+ | +-> Silencer->Stack v Cooling tower <- Heat exch <- Jacket pump ``` Main components: engine, alternator, air intake system (filter, supercharger), fuel system, exhaust system (silencer, stack), cooling system, lubricating system, starting system and governing system. #### Starting system A diesel engine cannot start by itself because the high compression needs an external torque to turn it to a speed at which compression temperature ignites the fuel. Methods: 1. **Compressed-air starting (most common for large plants):** an air compressor charges air bottles to about 17–25 bar. To start, a starting valve admits this air to some cylinders in firing order; the air pushes the pistons and rotates the crankshaft. When the engine reaches firing speed, fuel is injected and air supply is cut off. 2. **Electric starting:** a battery-driven DC motor turns the engine through a gear on the flywheel; used for small engines. 3. **Auxiliary petrol engine:** a small engine cranks the main engine through a clutch; rarely used now. #### Fuel supply system 1. Fuel oil arrives by tanker and is pumped through a strainer into the **bulk storage tank**. 2. A **transfer pump** sends it through filters to a **day tank** (holding about one day's need), placed higher so oil flows by gravity. 3. From the day tank oil passes through fine filters to the **fuel injection pump**, which raises the pressure (about 100–200 bar or more) and meters the correct quantity according to the governor setting. 4. The **injector (atomiser)** sprays fine droplets into the hot compressed air at the right instant, where it ignites. 5. Excess oil from the injectors returns to the day tank. Heaters are used for heavy oils to reduce viscosity. The fuel system may be a **common-rail**, **individual pump** or **distributor** type injection system. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why can a diesel engine not start by itself? A. It has no battery B. The high compression needs external torque to reach a speed at which compression temperature ignites the fuel C. The fuel is too thin to burn D. The alternator blocks rotation Answer: B. An external torque must turn the engine up to firing speed so compression heat ignites the injected fuel. (Key point: Why starting system is needed) 2. How does compressed-air starting work? A. Air bottles at about 17-25 bar admit air through a starting valve to cylinders in firing order, then fuel is injected and air is cut off B. A battery motor engages the flywheel C. A small petrol engine cranks through a clutch D. Air is blown into the fuel tank Answer: A. Air pressure pushes pistons to rotate the crankshaft; at firing speed fuel injection takes over. (Key point: Compressed-air starting) 3. Why is the day tank placed above the engine? A. To reduce injection pressure B. So oil flows to the injection pump by gravity C. To heat the oil D. To store months of fuel Answer: B. The day tank holds about a day's need and is elevated so fuel flows by gravity after fine filtering. (Key point: Role of day tank) 4. What does the fuel injection pump do? A. Filters water from fuel B. Stores bulk fuel C. Raises pressure to about 100-200 bar and meters the quantity per governor setting D. Cools the fuel Answer: C. It pressurises and meters oil, which the injector then atomises into hot compressed air. (Key point: Injection pump function) 5. What happens to excess oil from the injectors? A. Returns to the day tank B. Goes to the exhaust C. Is burnt in the silencer D. Is sent to the alternator Answer: A. Surplus/leak-off oil is returned to the day tank. (Key point: Leak-off oil) ## Related in Power Plant Equipment - [Diesel plant components and fuel supply](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-components-fuel-supply) — Power Plant Equipment, chapter 5, asked 3× - [Fuel supply system of diesel plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-fuel-supply) — Power Plant Equipment, chapter 5, asked 3× - [Diesel components and starting air system](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-starting-air-system) — Power Plant Equipment, chapter 5 - [Diesel layout with its five systems](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-layout-five-systems) — Power Plant Equipment, chapter 5 - [Layout of diesel power plant](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-plant-layout) — Power Plant Equipment, chapter 5, asked 3× - [Diesel fuel supply and lubrication functions](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_plant_equipment%3Adiesel-fuel-supply-lubrication) — Power Plant Equipment, chapter 5 ## Related in other subjects - [Types of power supply system for industrial plant](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aindustrial-supply-system-types) — Industrial Power Distribution and Illumination, chapter 1, asked 2× - [Major components of a power station](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Apower-station-major-components) — Power System Analysis I, chapter 1, asked 2× - [Major components of a power station and functions](https://www.bctengineer.com/question.md?key=semester_4%2Fpower_system_analysis_i%3Apower-station-components-functions) — Power System Analysis I, chapter 1 - [Components of a hydroelectric power plant](https://www.bctengineer.com/question.md?key=semester_5%2Ffluid_machines%3Ahydroelectric-plant-components) — Fluid Machines, chapter 2