Robust Estimation of Blow-by and Compression Ratio for Large Diesel Engines based on Cylinder Pressure Traces

The development of condition monitoring systems (CMS) for large diesel engines has gained importance due to the continuous integration of electronic and nautical functions on ships. Such systems should be able to assess engine health, to predict developing failures, i.e. engine state degradation, and to diagnose failure modes at a low price. Based on this information, maintenance intervals can be recommended or operational actions can take place. Condition monitoring for large diesel engines is still a challenging issue since robust estimates of certain engine failures as well as their unique identification from sparse observations of e.g. the cylinder pressure are required. Moreover, the engine state should be accessible with real-time performance. In this article, a fast model-based approach to detect and to separate two common failure modes-increased blow-by and compression ratio failures-of large diesel engines given cylinder pressure traces with low sampling interval is proposed. Special focus is put on estimation robustness and reliability by excluding the combustion phase and signal parts with high noise level. The nonlinear parameter identification problem is solved in terms of constrained optimization. The proposed approach is validated with experimental data.