This article discusses the prevention methods for cylinder pulling and piston burning in silent generator sets with Dingbo Power Generation Equipment, as improper operation often leads to unexpected failures of the unit. The following are the prevention methods analyzed by Dingbo Power Generation Equipment for reference by users:
To maintain normal movement of the piston in the cylinder of the silent generator set and maintain good air tightness, it is necessary to have a reasonable fit gap between the piston and the cylinder. At present, there are several methods for selecting the fit clearance between the piston and cylinder when assembling a diesel engine:
1. The calculation method only considers the thermal expansion caused by temperature, while in reality, the state changes of the diesel engine of the silent generator set during working time are very complex, such as the thermal deformation of the piston and cylinder, which are not taken into account. Therefore, the calculation method is only studied theoretically, and there are still certain problems in practical application, so this method has not been widely promoted and applied.
2. Tension matching method
The tension matching method is to invert the piston into the cylinder, select a certain size of thin plate from the thickness gauge and insert it between the piston skirt and the cylinder wall in a direction perpendicular to the piston. Then, use a scale to pull the thickness gauge and determine the reasonable range of the fitting gap by measuring its frictional resistance. The more piston and cylinder assemblies are grouped and the smaller the radial clearance value in the group direction, the more guaranteed the fitting clearance can be. Foreign manufacturers often adopt this method.
3. Group selection method
The grouping selection method is to group the processed pistons and cylinder holes according to different diameters, and then perform the same group matching.
In addition, premature fuel injection time and too lean mixture can increase the temperature of the silent generator set engine, and even cause the top of the piston to burn or pull the cylinder. For example, in a 12150L diesel engine, the fuel injection advance angle is 34 °. If this is too early (the fuel injection advance angle is greater than 35 °), the engine will significantly knock during operation, and the source of the knock is generally generated at the back of the fuel injector and the 1/4 edge of the piston top.
During the maintenance, it was found that if two 12150L diesel engines both experienced piston crown damage due to the explosion of the above parts, one of them even caused severe piston burning and cylinder locking. If the mixture is too lean, the combustion speed is slow, the temperature increases, and the combustion deposits carbon, causing local ignition at the top of the piston, leading to further temperature increase and deterioration of the piston's working condition in the cylinder, resulting in severe burning of the piston and cylinder pulling.
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