The main trend in the development of modern engine building is the acceleration of internal combustion engines at an average effective pressure and boost pressure. This leads to an increase in thermal and mechanical loads on the main parts of the engine, the increase in vibration of diesel engines, which necessitates the improvement of systems that ensure reliable operation of the engine in the entire range of operating conditions, especially lubrication and cooling systems. One of the factors negatively affecting the reliability of engines with liquid cooling systems are erosion and corrosion damage to the elements of the systems, especially the outer surfaces of the cylinder sleeves, washed by the coolant. The article is devoted to the actual problem-the choice of cooling parameters of modern internal combustion engines with a high level of acceleration and advanced engines. The method of choice of cooling parameters includes the identification of the most important of them and the reasonable determination of the preferred values of these parameters, taking into account the requirements of efficiency and reliability of marine diesel engines. To solve this problem, an algorithm is proposed that takes into account the design characteristics of the engine, the parameters of the workflow, cooling modes. The article presents the calculation formulas that allow to implement the proposed algorithm. The temperature and pressure in the cooling system and the hydrogen index of the coolant are set as the main cooling parameters affecting the intensity of erosion-corrosion damage and the efficiency of the diesel engine. The results of the calculations allow to estimate the influence of these factors on the intensity of erosion-corrosion damage and specific fuel consumption, as well as to recommend the most preferred cooling parameters. The conclusions made on the basis of the calculations are confirmed by the results of motor tests. The article offers technical solutions that allow automatic control of cooling parameters of marine diesel engines.
One of the perspective directions of improving diesels used as the main and auxiliary engines in the ship power plants composition is increasing the temperature level providing heat losses reduction, increase of engines thermal efficiency and their fuel economy. To implement this direction, many modern diesels are equipped with hightemperature cooling systems. Increasing the coolant temperature in such systems is accompanied by increasing the pressure in the cooling systems. Increasing pressure in the cooling systems leads to increasing the power consumption required to drive the circulation pump of the internal circuit of the diesel cooling system. The research purpose is a comparative assessment of the thermal-hydraulic efficiency of high-temperature and low-temperature cooling. As an evaluation criterion, the ratio of heat withdrawn through the cooling system and the power consumption for pumping the coolant, which provides this heat removal, is used. To determine this ratio, both known analytical dependencies and the results of numerical simulation of heat transfer processes in a cylindrical channel are used during the research. The use of both research methods allows us to obtain consistent results. Based on the conducted research results, it can be concluded that despite increasing the power costs for the circulation pump drive, the transition to high-temperature cooling provides an increase of the thermal-hydraulic efficiency of the ship diesel cooling systems. The most significant increasing the thermal-hydraulic efficiency of high-temperature cooling systems is possible when using water-water heat exchangers that provide the maximum permissible temperature difference of the coolant at the engine outlet and inlet.
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