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Preheating Device of Diesel Generator Set

Jan. 09, 2019

How is the engine of the diesel generator set preheated and run-in?

1. Engine warm-up


It takes a while for the oil film to re-establish between the crankshaft and the bearing, between the piston and the cylinder liner after the engine is started. The optimum clearance between moving parts can only be obtained after the engine parts reach the normal working temperature. Therefore, with the engine's heat engine, the engine speed is gradually increased from no-load speed 650r/min to 1000-1200r/. The preheating operation of the diesel engine is carried out at min. When the outlet water temperature reaches 55 °C and the oil temperature reaches 45 °C, the full load operation is allowed to avoid the piston from seizing in the cylinder, the shaft and the bearing generate dry friction.

Preheating Device of Diesel Generator Set.jpg

 2. Engine running-in

New diesel engines or overhauled diesel engines must be run-in before starting use. Because the parts will always leave different degrees of knife marks on the surface after processing, if the load is not carried out immediately after a certain running-in, it will cause zero, the components are worn out, affecting the service life of the diesel engine or malfunctioning until damage


Diesel generator set preheating device


The diesel engine is self-igniting by high temperature and high pressure. Therefore, when the diesel engine is started, the temperature inside the cylinder has a great influence on starting the diesel engine, especially in the case of low ambient temperature. Therefore, a diesel engine that is started by a DC motor usually has an electric preheating device installed in the auxiliary combustion chamber so that the diesel fuel is atomized in the combustion chamber to form a combustible mixture. The structure and circuit of the glow plug are shown in Figure 1.

Preheating Device of Diesel Generator Set (2).jpg


Glow plugs are typically installed in diesel engines employing vortex or pre-combustion combustors to preheat the air in the combustion chamber at startup. One end of the spiral resistance wire is welded to the center screw, and the other end is welded to the bottom of the heating cylinder sleeve made of high temperature resistant stainless steel. The steel sleeve is filled with an alumina filler having certain insulation properties, good heat conduction and high temperature resistance. The screw of the center plug of each glow plug is connected in parallel and connected to the battery. Before the start of the diesel engine, the glow plug circuit is turned on with a special switch. The heat-generating steel sleeve raises the temperature of the air inside the cylinder, thereby increasing the air temperature at the end of the compression, making the diesel fuel injected into the cylinder easy to catch fire. .


When the diesel engine is started, press the heating button, and the battery supplies power to the glow plug through an additional resistor to raise the temperature of the air inside the cylinder. When heated, it is indicated by the indicator plug.


Principle of flame preheating device for diesel generator set


The flame preheating device of the diesel generator set is a cold start auxiliary device used in cold weather. The whole system consists of a temperature sensor, a solenoid valve, a flame preheat plug, an electronic control device and a preheating indication installed on the engine outlet pipe of the unit. (The schematic diagram is shown below). The fuel enters the glow plug from the low-pressure oil pipeline of the fuel system, and is electrically ignited and ignited. The flame of the fuel combustion enters the air in the intake pipe, making the engine easy to start. The whole process is automatically completed by the control system. It can automatically control the warm-up time of the glow plug installed on the intake pipe and the warm-up time of the flame according to the different ambient temperature. The user only needs to turn on the key switch after the key switch is turned on. Start the engine after the heat indicator flashes.




1. Electronic control device A24     2. Engine cooling water pipe            3, temperature sensor R1 

4. Oil supply pipe         5 connected to high pressure oil pump, solenoid valve Y21         6, oil pipe 

7, engine intake pipe         8, glow plug R3           9, 24V battery            10, key switch 

11, fuse 25A         12, preheat indicator light 112/29        13, generator             14, start button



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