Methodological Aspects of Assessing the Thermal Load on Diesel Engine Parts for Operation on Alternative Fuel

The decarbonization of maritime transport has become a crucial strategy for the adoption of renewable low-carbon fuels (LCFs) (MARPOL 73/78 (Annex VI) and COM (2021) 562-final 2021/0210 (COD)). In 2018, 98% of operated marine diesel engines ran on fossil fuels. The application of LCFs, according to expert assessments (DNV GL), is considered the most effective solution to the decarbonization challenge in the maritime sector. This publication presents methodological proposals related to assessing the reliability of operational diesel engines when transitioning to low- carbon fuels. The proposed methodology implements an interconnected assessment of the combustion cycle parameters and the limiting reliability factors of the thermal load on the most critical components of the cylinder-piston group. The optimization of the combustion cycle parameters for the indicators of energy and the environmental efficiency of low-carbon fuel applications was combined with the evaluation and assurance of permissible values of the thermal load factors on the components to determine the overall reliability of the engine. Thus, the possibility of overload and engine failures was already eliminated at the retrofitting design stage. The algorithm for the parametric analysis was grounded in the practical application of established alpha-formulae for the heat exchange intensity, such as those of the Central Diesel Engine Research Institute and G. Woschni. This approach was combined with modeling the combustion cycle parameters by employing statistical or single-zone mathematical models such as IMPULS and AVL BOOST. The alpha-formulae for low carbon fuels were verified based on the thermal balance data. The structure of the solutions for the effectiveness of the practical implementation of this methodology was comprehensively oriented towards diesel "families", as exemplified by the models 15/15 (pmi = 1.2, 1.4, and 1.6 MPa). The long-term goal of the obtained results in the structure of comprehensive decarbonization research was to assess the factors of the reliable operation of characteristic groups of medium-speed (350-1000 rpm) and high-speed (1000-2100 rpm) marine engines for reliable operation in the medium term on ammonia.