Applying logical and probabilistic methods to determine the causes of failure of turbochargers in the internal combustion engines operation

Abstract

Problem. Despite the success in research and development of turbocharger designs for internal combustion engines, to date, reliable methods have not been created to determine the causes of their failures, and the application of known methods in practice is so labour-consuming that it is practically ineffective. As a result, in operation, consumers, as a rule, find it difficult to determine the cause of the malfunction. Goal. The goal of the study is the development of a simple technique for determining the causes of the turbochargers failures. Methodology. The study showed that the causes of failure of turbochargers of the internal combustion engines can be determined using logical and probabilistic methods, including those on the basis of a failure tree analysis, using on existing experience in studying turbocharger faults. For this purpose, a block diagram of a turbocharger was adopted, consisting of 4 main components – a compressor, a turbine, a bearing assembly and a control system. Consistent approximations were used to compile the methodology: first, the sources, symptoms and causes of malfunctions were identified with their breakdown into groups, then, based on the existing experience of studying the causes of failures, the signs and causes were detailed by nodes, with a detailed description of the characteristic types of damage to the turbocharger, based on which all the necessary data were used to compile a fault tree. Results. A modified (inverted) fault tree was developed, which allows performing logical analysis in the opposite direction to the generally accepted direction – from the system failure event to the basic events initiating the failure. Testing the proposed methodology in real cases of failures showed that determining the cause of the failure can be done with sufficient reliability for practice with minimal time. Originality. The well-known fault tree analysis method was used to develop a new methodology for determining the causes of failures in ICE turbochargers. Practical value. Using the proposed methodology eliminates repetition of failures and unreasonably high costs of operation and repair arising from improper determination of the cause of failure of the turbocharger.

Keywords: internal combustion engine; turbocharger; failure; cause; fault tree analysis.