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A method for evaluating theoretical and real operation of diesel engines in energy conversion formulation taking into account their operating indices


The article proposes valuating the operation of an arbitrary diesel engine, based on the sample case of a ship’s main engine in which energy conversion processes take place in a given time. The above operation is understood as the energy transfer to the screw propeller in the given time in which the energy conversion into work and/or heat and its further transmission take place. The here proposed method for evaluating the operation of the main engines installed in marine power plants consists in comparing the operation of these engines to a physical quantity the measuring unit of which is the joule-second (joule×second). A new term is introduced which bears the name of the theoretical engine operation and is the standard (ideal) operation which can be compared to the operation of real engines revealing different levels of wear. It was shown that the calculations of the theoretical operation defined in the above way cannot make direct use of commonly known theoretical Diesel and Sabathe cycles. Instead they should use the cycles modified by heat abstraction taking place in accordance with the isobaric, or isothermal process. Other new terms introduced in the article are: the degree of excellence of energy conversion to work, considered as the measure of excellence of engine operation, and the degree of engine operation dissipation, being the measure of its real operation. It is shown that if in time t of engine operation the case takes place that: Li = idem and Le= idem, then the engine operation dissipation is equal to its mechanical efficiency.


operation, energy, diesel engine, ship’s main engine


Vol. 18 No. 3(70) (2011)
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Jerzy Girtler

Gdansk University of Technology, Faculty of Ocean Engineering and Ship Technology

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