Abstract
Internal combustion engines are the most common sources of energy among heat engines. Therefore, the improvement of their design and workflow is an urgent task in the development of world energy. Thermal-mechanical perfection of the exhaust system has a significant impact on the technical and economic performance of piston engines. The article presents the results of experimental studies of gas-dynamics and heat exchange of pulsating gas flows in the exhaust system of a piston engine. Studies were carried out on a full-scale model of a single-cylinder engine. The article describes the instrument-measuring base and methods of experiments. The heat transfer intensity was estimated in different elements of the exhaust system: the exhaust pipe, the channel in the cylinder head, the valve assembly. Heat transfer studies were carried out taking into account the gas-dynamic nonstationarity characteristic of gas exchange processes in engines. The article presents data on the influence of gas-dynamic and regime factors on the heat transfer intensity. It is shown that the restructuring of the gas flow structure in the exhaust system occurs depending on the engine crankshaft speed, this has a significant impact on the local heat transfer coefficient. It has been established that the heat transfer intensity in the valve assembly is 2-3 times lower than in other elements of the exhaust system.
Highlights
One of the ways to improve the performance of piston internal combustion engines (ICE) is to improve its workflow [1,2,3]
It should be noted that in most cases mathematical modelling of gas dynamics and heat exchange of gas flows is performed in stationary conditions
The studies were conducted on a full-scale model of a piston engine in order to establish the influence of gas-dynamic non-stationarity on the heat transfer intensity in different elements of the exhaust system of the ICE
Summary
One of the ways to improve the performance of piston internal combustion engines (ICE) is to improve its workflow [1,2,3]. The heat transfer intensity in the exhaust system significantly affects several technical and economic indicators of the engine, such as external heat balance, average cycle temperature, temperature stresses of the exhaust system components (exhaust valve, cylinder head, exhaust manifold, etc.). There are studies of physical processes in the exhaust system based on mathematical modelling in order to improve the technical and environmental parameters of piston engines. It should be noted that in most cases mathematical modelling of gas dynamics and heat exchange of gas flows is performed in stationary conditions. Since it is known that the heat transfer coefficient in non-stationary conditions may differ from the stationary case by 2-4 times [16, 17]. The purpose of this study was to obtain data on the heat transfer intensity in different elements of the exhaust system under the conditions of gas-dynamic non-stationarity (pulsating gas flows)
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