Harmful deposits in reciprocating internal combustion engines - methods of assessment and scope of application

The deposits forming on the surfaces of various internal parts of reciprocating internal combustion engines and the systems operating in conjunction with them are an undesirable phenomenon which intensifies during the operation of the engines and threatens their proper operation. More and more complicated engine designs and the increasing accuracy of workmanship of the parts working in conjunction with them necessitate the multi-directional testing of harmful deposits. An increasing number of factors affecting deposit formation are being identified, which leads to the development of increasingly complex classifications and subdivisions of deposits according to their type, composition, and form. The article presents the problems of the deposits produced in reciprocating internal combustion engines and their fuel systems. Standard and non-standard engine and analytical methods for both quantitative and qualitative assessment of deposits are discussed. The significance of currently applied assessment methods for the formation of deposit classification is presented. The paper presents the scope of application and usefulness of methods for the determination of the threats posed by various types of deposits to the functioning of the engine and for the identification of the causes for their formation, including in particular those related to the composition of fuels and engine lubricating oils used. A practical approach to the quantitative and qualitative assessments of deposits is discussed on the examples of engine, microscopic and spectral test assessments of real deposits produced on various elements of SI and CI engines and their fuel systems, including both the fuel supply systems using hydrocarbon fuels and those using fuels containing biocomponents.