Research of changes of characteristics of the engine and operational properties of the truck owing to change of diameters of cylinders.
Students Name: Zhytnetskyi Oleh Yuriiovych
Qualification Level: magister
Speciality: Motor Vehicle Transport
Institute: Institute of Mechanical Engineering and Transport
Mode of Study: part
Academic Year: 2020-2021 н.р.
Language of Defence: ukrainian
Abstract: Zhytnetskii O. Y., Kotsiumbas O. Y. (supervisor). Research of changes of characteristics of the engine and operational properties of the truck owing to change of diameters of cylinders. Master’s thesis. – Lviv Polytechnic National University, Lviv, 2020. Extended abstract. Improving the reliability of the internal combustion engine (ICE) of the car is provided primarily by the durability of the parts of the connecting rod-piston group. For these parts, important indicators are the level of production technology, mechanical characteristics of materials, the quality of the working surfaces of parts, taking into account the further possibilities of their repair. The most common method of increasing the service life of engines is the method of restoring their sleeves by boring to the repair size. It provides for an increase in the diameter of the cylinder liners, which leads not only to a change in the temperature of the engine as a whole, which determines the stability of the performance of the internal combustion engine. Increasing the diameter of the cylinder liners affects the traction and speed performance and fuel economy of the car. In this regard, the study of the processes of changing the characteristics of the internal combustion engine and traction and speed of the car with restored sleeves is an urgent scientific and applied task. Object of study — the characteristics of the internal combustion engine, primarily external speed, traction and speed properties, primarily traction on the driving wheels, acceleration of the car. Scope of research: patterns between changes in cylinder diameters and engine performance together with the dynamic properties of the car. Goal of research: to determine the degree of influence of increasing the diameter of the cylinders on the change of energy parameters of the car engine in combination with the traction and speed properties of the car. The first section considers the issues of operational reliability of automobile engines. The causes and sources of harmful effects that impair the performance of automobile engines, the scheme of interaction of engines with the environment are analyzed. According to this scheme, the process of wear of parts dominates in the considered processes. The extreme complexity of wear processes of working surfaces of cylinders and their dependence on a large number of design and operational factors is noted. The second section is devoted to the mathematical description of the external speed characteristic (ESCH) as a function of effective power, engine torque from the angular velocity of the crankshaft. It is proved that boring leads to changes not only in temperature, but also in the characteristics of the engine, resulting in changes in the performance of the car as a whole. In the third section it is substantiated that among a number of properties one of the most important places is occupied by traction - speed (TSP), which are affected by the increase in the diameter of the cylinder. The generally accepted criteria for assessing TSP are the limit (test) capabilities of the car, which are determined by the engine’s engine capacity. Considered and compared parameters depending on the speed of the car, reflecting or directly affecting the change of its traction and speed properties with the nominal and repair dimensions of engine cylinders: 1) torque on the drive wheels and the distribution of power balance; 2) the dynamic factor and acceleration of the car; 3) duration and acceleration path, in particular, for 60 km / h and 80 km / h. An N2 class truck was selected for consideration. Analytical calculations show that an increase in the degree of compression by 2.6% together with an increase in working volume by 3% due to boring of cylinders causes an increase in torque and power at low speeds - by 4.1%, at medium - by 3.8 %, and for the maximum - by 3%. The analysis of the dynamic characteristics of the car showed that for the increased diameters of the cylinders, the maximum dynamic factor in the first gear increased by 4.3%, and in the higher (direct) transmission by 4.5%. Comparing the acceleration dynamics, it was found that the duration of acceleration from standstill to a speed of 60 km / h of a car with restored engine cylinders decreased by 4.6%; the corresponding path by 5%. Keywords: repair dimensions; traction-speed properties; external speed characteristic; dynamic factor; duration (time) and acceleration path.