Abstract
<jats:p>BACKGROUND: Associate Professor of the Department of Marine Internal Combustion Engines at the Leningrad Shipbuilding Institute (now St. Petersburg State Marine Technical University), Konstantin Nikolaevich Koptev (1929–1996), from 1990 until the last day of his life, developed a methodology for the design calculation of the working cycle of low- and medium-speed diesel engines, which made a significant contribution to the development of the discipline “Theory of Working Processes of Internal Combustion Engines.” The most important refinement of the traditional Grinevetsky–Mazing methodology is the rejection of the assumption of the equality of the compression ratio and the expansion ratio. This assumption contradicts the well-known fact that an additional means of improving the working process is to use the difference between the actual compression ratios. AIM: To refine the Grinevetsky–Mazing methodology by eliminating the causes of deviation of the calculated economic efficiency parameters of the design working cycle from the practical results achieved not only by experimental but also by production engines. METHODS: The method of studying this function to find its maximum using derivatives is applied. RESULTS: The result is a set of parameters that ensures maximum efficiency of an ideal cycle with mixed heat supply. CONCLUSION: The article has theoretical significance. The results can be used in practice when modeling in-cylinder processes of modern high-efficiency marine diesel engines.</jats:p>