Abstract
The paper presents a heat exchange model for the cooling system of any complex, physical system. Verification of the correctness of the theoretical model was carried out on the example of a vehicle with a combustion engine and additionally equipped with a hydraulic retarder. The results of laboratory tests, which were carried out on an engine test bench, were also performed for the above mentioned powertrain, so as to compare the results of modelling with the results of the tests. Determining the operating parameters of the components of the cooling system aimed at protecting the entire powertrain against overheating is a key task. Theoretical analysis of heat exchange in the powertrain of a road vehicle was carried out, with particular emphasis on the hydraulic retarder (a device braking the vehicle during a descent on roads with a high gradient of the road, mandatory according to the ADR convention). The subject of the study was a mathematical model of a complex cooling system developed by the authors, described by means of balance equations and differential equations. This model was tested with the use of the Matlab-Simulink suite for given load parameters of the cooling system, which were used in tests on an engine test bench. The values of coefficients describing the thermal state of the powertrain were obtained. Simulations were performed for different variants of technical parameters of the expanded cooling system. In this way, individual units and components of the cooling system were optimized so that it fulfilled its role in the assumed operating conditions and the ecologization of emission of energy sources (fuel) and harmful substances.
Highlights
Modern trucks for the transport of cargo/humans, apart from the conventional braking system, are equipped with additional braking systems which can take the form of an electrodynamic brake, engine brake or hydraulic brake [5, 9, 10, 12]
When driving on long and steep road sections, the vehicle often uses the service brake, which can lead to increased heat load and serious wear to the brake system
A series of tests was carried out taking into account different ambient temperatures, heat exchange surfaces of the radiator, increasing the thermal capacity of the system
Summary
Modern trucks for the transport of cargo/humans, apart from the conventional braking system, are equipped with additional braking systems which can take the form of an electrodynamic brake, engine brake or hydraulic brake [5, 9, 10, 12]. When driving on long and steep road sections, the vehicle often uses the service brake, which can lead to increased heat load and serious wear to the brake system. This is a dangerous phenomenon affecting the decrease in the efficiency of the mechanical brake due to the thermal recession of the system [3, 4, 28]. Compared to other auxiliary equipment, hydraulic retarders have many advantages such as low weight, high braking torque, long operating hours, good thermal diffusivity and zero environmental pollution.
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