CROSSHEAD DIESEL ENGINE PISTON LIFETIME EXTENTION

https://doi.org/10.33815/2313-4763.2019.2.21.059-066

Abstract

The crosshead diesel engine piston is designed, which has additional piston grooves under compression rings. The number of the piston grooves is equal to the number of the compression rings. The safety rings are installed into additional piston grooves.The dimensions of the safety rings match as closely as possible with those of the piston grooves. The design with the number of additional piston grooves under compression rings which equals the number of compression rings, reduces thermal load and enables to make additional piston grooves for the whole group of compression rings. Positioning of satefy rings into additional piston grooves, the dimensions of which, when installed, match as close as possible with the dimensions of additional piston grooves, protect the additional piston grooves from cylinder oil and combustion products ingress.  Piston grooves and rings wear leads to the drop in cylinder pressure, loss of engine power, and eventually to rings breakage and engine failure. The process of restoring the efficiency of engine performance is time-consuming and requires significant material expenses. This is especially true for the pistons restoration. Pistons repair process is carried out in specialized workshops and requires highly-qualified technical personnel and material expenses. Taking into account the widespread use of piston internal combustion engines, as well as high maintenance and repair costs, the problem of pistons lifetime extention and repair process expenses reduction, is of practical importance. Compression rings and piston grooves wear is due to their friction with each other in conditions of insufficient lubrication and contact with abrasive particles on the surface. Replacement of the rings does not cause contamination and can be carried out by the engine room team during regular repair of the cylinder-piston group. Repair of the piston is possible to be carried out only in a specialised workshop and requires considerable investment. Piston lifetime extention by increasing the wear resistance of the working surfaces of the piston grooves has given a certain result, but it has already outlived its usefulness. The purpose of the research is to modernize the cylinder-piston group of crosshead diesel engine so as to extend piston lifetime twice without conducting additional repair of the piston grooves in a specialized workshop. To achieve this goal, it is necessary to analyze the design of the piston and piston rings, to determine the cause of premature wear of grooves and offer an option to compensate for this deficiency. The crosscut engine piston has been designed, where additional grooves are made under the compression rings and their number equals the number of compression rings. Safety rings are installed into additional grooves so that their dimensions match as close as possible when installed. Application of additional grooves under compression rings in the number equal to the number of compression rings, reduces their thermal loads and makes it possible to make additional grooves for the whole group of compression rings. Safety rings installation into additional grooves, the dimensions of which, when installed, are as close as possible to the dimensions of additional grooves, protect additional grooves from ingress of cylinder oil and combustion products. The application of the proposed technical solution, extends piston’s lifetime twice and does not require the repair process of the grooves to be carried out in a specialized workshop. It is possible to implement upgrades in the manufacture of new pistons and cylinder liners or, after consultation with the engine manufacturer, to redesign already manufactured elements of the cylinder-piston group.