What type of drive should be used in a fire pump？

Fire pumps are usually driven by electric motors or diesel engines. Consideration must be given to ensure that sufficient power or sufficient fuel is available to drive these drives in the event of a fire. Engines are often used as pump drives where there is an unacceptable risk of interruption, unreliability, unavailability ,or unsuitable electrical power.

Diesel-driven pumps are typically used where the electrical grid is unreliable or unable to handle electric power to drive the pump load. They are also used where there is a lack of emergency power, such as generators.  Because of the extra steps required to handle fuel systems, cooling, exhaust, vibration, etc., you can expect diesel-driven pumps to have more provisions than electric pumps. For example, diesel-driven pumps require additional space to store fuel tanks and must be located in a separate enclosure or room with direct access to the outside. Diesel engines operate in the following modes.

The Operating mode of diesel generator： 

A diesel engine is a type of internal combustion engine that uses compression ignition to ignite the fuel as it is injected into the engine.  It relies on compression for combustion, which results in increased fuel efficiency compared to other types of engines.  

Engine Construction：

The main components of a diesel engine look like the components of a gasoline engine and perform the same job. However, because of the higher loads involved, diesel engine components must be stronger than their gasoline engine counterparts.

Diesel engine blocks typically have much thicker walls than blocks designed for gasoline engines, and they have more supporting webs to provide additional strength and absorb stresses. In addition to being stronger, heavy-duty blocks are also more effective at reducing noise.

Pistons, connecting rods, crankshafts ,and bearing caps must be stronger than in gasoline engines. The design of the cylinder head described must be because the fuel injector is also due to its shape and very different combustion and vortex chamber.

Diesel engines work：

Diesel engines work by four processes: intake, compression, combustion expansion, and exhaust, which form a work cycle. A diesel engine in which the piston goes through four processes to complete a work cycle is called a four-stroke diesel engine.

The first stroke - air intake, its task is to make the cylinder full of fresh air. When the intake stroke begins, the piston is located in the upper stop, the cylinder in the combustion chamber still has some exhaust gas.When the crankshaft rotates the elbow, the connecting rod makes the piston from the upper stop point to the lower stop point move, at the same time, the use of the crankshaft with the drive mechanism to open the intake valve.

The second stroke--compression. The Compression when the piston from the lower stop point between the upper stop point movement, the function of this stroke are two, one is to improve the temperature of the air, for the fuel to prepare for their fire: two is to create the conditions for gas expansion work. When the piston goes up, the intake valve is closed, and the air in the cylinder is compressed, with the volume of the continuous fine, the pressure and temperature of the air are rising, the pressure and humidity at the end of compression, and the degree of compression of the air, that is, with the compression ratio, the general pressure ,and temperature of the end of compression.

the temperature of the end of compression is much higher than the temperature of diesel fuel self-ignition, enough to ensure that the fuel injected into the cylinder self-firing combustion.

Sprayed into the cylinder of diesel fuel, not immediately after the fire, and after the physical and chemical changes before the fire, this time about 0.001 to 0.005 seconds, called the fire delay period. Therefore, to turn the crank to the upper stop before 10 to 35 ° crank angle when the start of the atomized fuel sprayed into the cylinder, and make the crank in the upper stop after 5 to 10 °, in the combustion chamber to reach the highest combustion pressure, forcing the piston downward movement.

The third stroke – is combustion expansion. At the beginning of this stroke, most of the fuel injected into the combustion chamber is burned. Combustion gives off a lot of heat, so the pressure and temperature of the gas will rise sharply, the piston under the action of high temperature and the high pressure gas downward movement, and through the culm to make the crankshaft rotation, external work. So this stroke is also called work or work stroke.

With the piston down, the volume of the cylinder increases, the pressure of the gas drops, the work stroke in the piston line to the next stop, the exhaust valve open when the end.

The fourth stroke - exhaust. The function of the exhaust stroke is to exhaust the exhaust gas after expansion, to fill the fresh air, for the next cycle of air intake for preparation.

Once the exhaust valve is opened, with a certain pressure of gas immediately rushed out of the cylinder, the cylinder pressure drops rapidly, so that when the piston moves upward, the cylinder exhaust gas relies on the piston upward to discharge. In order to use the exhaust airflow inertia to make the exhaust gas discharge clean, the exhaust valve is in the upper stop point before closing.