Abstract
The article summarizes the results of heat engineering tests of diesels used in the educational process of Volga State University of Water Transport and its branches. Although the test goals were different in each case, the indicator diagrams of the working process in each cylinder were recorded in the course of the tests. Analysis of indicator diagrams helped to determine the indicator power of the engine in each case. By comparing the indicator parameters with the corresponding effective ones there was performed the estimation of the mechanical efficiency of each engine at different speeds of rotation of the crankshaft. The studies were carried out on engines of brands 6NVD48AU, 6L275RrII/PN, 8NVD36U, 6L160PNS. It was found that in almost all cases, mechanical losses included fan losses in load devices and friction losses in their bearings. The concept of a screw characteristic is considered. A graph of the propeller characteristics in relative units for various types of engines is built. It is noted that it is very difficult to set a specific value of the crankshaft speed required for testing, the actual points will be close to the theoretical ones, shifting along the helical characteristic. An algorithm for testing and processing the results is presented. There have been analyzed the dependences covered in literature (analytical and statistical) for determining the mechanical efficiency.
Highlights
The test goals were different in each case, the indicator diagrams of the working process in each cylinder were recorded in the course of the tests
By comparing the indicator parameters with the corresponding effective ones there was performed the estimation of the mechanical efficiency of each engine at different speeds of rotation of the crankshaft
There have been analyzed the dependences covered in literature for determining the mechanical efficiency
Summary
Волжский государственный университет водного транспорта, Нижний Новгород, Российская Федерация. Что задать конкретное требуемое для испытаний значение частоты вращения коленчатого вала очень сложно, действительные точки будут находиться вблизи теоретических, смещаясь по винтовой характеристике. Имеющиеся в ФГБОУ ВО «Волжский государственный университет водного транспорта» и филиалах двигатели (марок 6NVD48AU, 6L275RrII/PN, 8NVD36U, 6L160PNS) оснащены индикаторными кранами, что позволяет при помощи специального аппаратно-программного комплекса записать индикаторную диаграмму для каждого цилиндра. Если номинальная мощность достигается при частоте вращения коленчатого вала ниже номинальной, то такая винтовая характеристика будет гидродинамически тяжелой. Что задать именно то значение частоты вращения коленчатого вала, которое требуется для испытательного режима, при проведении испытаний достаточно сложно, а зачастую и невозможно вовсе. 2. При этой же частоте вращения коленчатого вала по винтовой характеристике определить эффективную мощность двигателя Pe. 3. В этом случае для сокращения времени прогрева двигателя целесообразно проведение испытаний, начиная с больших частот вращения коленчатого вала к меньшим.
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