Diesel Generator

Introduction

This is a 3D model of a Diesel Generator.

3D Model Annotations

Emergency Diesel Generator (EDG)

An emergency diesel generator supplies electrical power to a facility during a blackout (loss of power). The emergency generator busbar is typically isolated from the main bus. Power is distributed to electrical loads that are classified as ‘critical’ for plant operations. For example, critical loads often include cooling pumps, cooling fans, and process valves. Unlike the main bus, only some machinery is connected to the emergency busbar e.g. 1 of 2 pumps connected, not 2 of 2; this decreases the load on the generator, and consequently its required kW size. To ensure the generator is autonomous, it is fitted with its own means of starting (air or electrical) and its own fuel tank.

Lubrication Oil Filter

Lubrication oil is continuously filtered to prevent foreign particles damaging internal engine parts (cylinder liners, piston rings etc.).

Fuel Filter

Fuel is filtered to prevent incombustible particles entering the combustion space; these particles can corrode engine parts and block fuel injector spray holes (changing the spray pattern and causing a reduction in engine efficiency). A dirty filter may lead to the engine being starved of fuel, and the engine stalling as a result.

Cooling/Jacket Water Pump

The cooling water (or ‘jacket water’) pump circulates jacket water through the engine and has two purposes. It ensures heat is dissipated through the engine uniformly and the circulation of jacket water allows the removal of heat generated by the engine.

Expansion Tank

The jacket water (cooling water) expansion tank allows for volumetric expansion and contraction due to increasing and decreasing temperature. A low level alarm is usually fitted to the expansion tank.

Charge Air Cooler / Intercooler

Charge air (compressed air) is cooled in order to increase the density of the air. The increase in density means that there is more oxygen available for combustion per volumetric space. The air density must not be too high otherwise moisture will form and corrosion of the engine's internal parts will occur.

Crankcase Breather Filter

Air/Oil vapour is vented from the crankcase. Oil from the vapour is separated and drained back to the crankcase, the air is expelled. Separation of the oil reduces oil losses and reduces overall running costs.

Turbocharger

A turbocharger compresses air into the combustion space in order to generate more power. Compressed air has a larger air mass than ambient air and this increases the amount of fuel that can be burnt efficiently within the combustion space (more air = more oxygen for combustion). Increasing the amount of fuel that is burnt efficiently has a corresponding effect upon the engine’s power output (power output increases) and thus a higher power to weight ratio can be obtained for an engine equipped with a turbocharger compared to one without.

Drive Shaft

The drive shaft connects the engine with the intended power recipient. Normally, a gearbox or clutch will be installed as an intermediary; this allows greater control of how the engine power is utilised.

Exhaust Discharge

After the turbocharger exhaust gas turbine, exhaust gas is discharged and expelled to atmosphere.

Flywheel

A flywheel stores rotational energy and resists changes to rotational speed. Essentially a flywheel is a heavy metal disc that smooths the engine combustion cycles. The amount of energy stored in the flywheel is the square root of its rotational speed.

Engine Block / Cylinder Block

The engine block houses the pistons, connecting rods, and cylinders of the engine. Channels within the block are used to distribute jacket water for cooling.

Starter

The starter is a device used to rotate the engine crankshaft upon receiving a start signal. It is not possible to start the engine without the starter as the engine must be in motion prior to fuel injection. Starters are typically electrically (starter motor) or pneumatically (air starter) operated.

Lubrication Oil Sump/Reservoir

Lubrication oil is stored in the oil sump/reservoir.

Rocker Arm Cover

The rocker arm cover encases the rocker arms. It is necessary to encase them as they are splash lubricated and operate at relative high speeds.

Generator

The generator converts the mechanical power from the combustion engine (prime mover) into electrical power. Mechanical power is transferred from the engine’s drive shaft to a rotor within the generator. The generator rotor rotates within the stator, which causes electrical current to be induced in the stator (electromagnetic induction). The stator is connected to an external circuit so that the electrical power can be dispatched. Medium and large industrial generators use three electrical phases.

Air Filter

Foreign particles are prevented from entering the combustion space and turbocharger compressor by filters. It is essential air filters are changed periodically as a dirty filter will starve the engine of the necessary oxygen it requires for combustion; thus a reduction in engine efficiency will occur and in extreme cases the engine will stall.

Fuel Tank

Many diesel generators are sold as package units. Package units come with all the machinery they need in order to operate. For ease of installation, the fuel tank is often mounted directly below the main engine.

Bearing Temperature Monitoring

Bearing lubricating oil temperatures are monitored in real-time using temperature sensors. Should a bearing begin to overheat, the bearing lubrication oil temperature will also rise, and personnel will be alerted by an alarm.

Instrumentation

Electronics are installed on almost all modern diesel engines. Flow, temperature, pressure, speed, and level sensors, feed data to an engine control unit (ECU) and computer monitoring system. Alarms, shutdowns, and feedback loops, all operate based upon the data they receive from these sensors.

Lubrication Oil Pump

Lubrication oil is circulated by the lubrication oil pump. Oil pressure will typically be 3-4 bar (43-58 psi) when the engine is operating. A low oil pressure will lead to a low oil pressure alarm sounding. A very low (‘low low’) oil pressure will cause the engine to shutdown. IMPORTANT – some emergency generators are considered ‘sacrificial’ and will operate until they can no longer operate (‘run to destruction’). The logic for this breakdown decision relates to the effects that would occur should the generator shutdown during an emergency e.g. if a plant requires cooling pumps to remain in service for safety reasons, but the generator shuts-down leading to a resultant plant explosion, this is not desired. For this reason, sometimes the generator will be setup to be sacrificed (sacrificial component); the same setup is often used for steam turbine lubrication oil pumps (the motor overload temperature relay is removed).

Jacket Water Cooler

Jacket water is cooled using two shell and tube type heat exchangers. Heat is rejected to an external cooling circuit.

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