Limit state, engine oil, operational tests

The article analyzes the possibility of using a new criterion for assessing the limit state of a compression-ignition internal combustion engine. The proposed criterion expands the decision-maker’s options regarding the selection of an appropriate, optimal criterion at the stage of assessing the limit state of an engine-vehicle. The paper presents problems resulting from the correct selection of indicators and their limit values for the proposed criterion, while simultaneously indicating methods for their resolution.The Polish Standard [1] defines the limit state of an object as a physical (technical) state in which further operation of the object is impossible or inadvisable.
From the moment of manufacture until the limit state is reached, the engine is in the class of operational states.
After crossing the boundary of the operational area, the engine enters the class of non-operational states. In literature, such an event is referred to as parametric failure. The process of changes in the technical state of the engine within the area of operational states is determined by the physical processes of engine component wear. This is an objective relationship, and the course of changes in the technical state results from the operational wear of components. However, the determination of the boundary between the area of operational states and the area of non-operational states is conventional. Limit state criteria depend on the adopted parameters of the quality of the engine’s technical state. Considering that the quality of products is measured by the degree of fulfillment of the buyer’s requirements (the degree of buyer satisfaction), it should be stated that the most important criteria for the limit state of an automotive engine should be the criteria postulated by the user, i.e., [2]: technical criteria, economic criteria.
Below, the discussion is limited to the area of technical criteria, with particular emphasis on engine oil as a structural element of the piston-piston ring-cylinder (TPC) system of a compression-ignition internal combustion engine [3]. (…)

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