Influence of various road and climatic operating conditions on the process of wear of vehicle parts

ABSTRACT

The article presents the results of work on a qualitative assessment of the degree of influence of various causes on the wear of parts of automobile engines operating in conditions of high temperature and dusty air in the Central Asian zone. Based on the analysis, specific conclusions and proposals are proposed for increasing the durability of cars by applying an effective system for protecting engines from mechanical (dust) particles of pollution that enter them along with air, fuel and oil.

АННОТАЦИЯ

В статье представлены результаты работы по количественной оценке степени влияния различных причин на износе деталей автомобильных двигателей, работающих в условиях высоких температур и запыленного воздуха в зоне Центральной Азии. На основе анализа, конкретные выводы и предложения предложены для повышения долговечности машин путем применения эффективной системы для защиты двигателей от механических (пыли) частиц загрязнений, которые входят в их вместе с воздухом, топливом и маслом.

Keywords: Car, engine, engine oil, road and climatic conditions, wear, abrasive, corrosive, mechanical, road dust.

Ключевые слова: Автомобиль, двигатель, моторное масло, дороги и климатические условия, износ, абразивная, коррозионная, механическая, дорожная пыль.

The operation of motor vehicles in various operating conditions, especially in quarries, where the increased dust content of the air causes increased wear of their parts and mechanisms, and with the increase in the wear of the car parts, the consumption of fuel and other operating materials increases, and frequent failures and breakdowns occur.

Deterioration of steering and braking system parts impairs vehicle handling, making it less safe to drive. The wear of parts, assemblies and mechanisms causes a change in the original dimensions of the parts and their geometric shape, subsequently this leads to a significant increase in the gaps between rubbing parts, the appearance of noise, knocking and vibration. 

The largest number of malfunctions and failures in units and mechanisms occurs due to the natural process of wear of parts. An increase in the clearance in mating parts is allowed up to a certain limit, which is different for different mates and depends on their design and purpose. When the mechanism operates with a clearance that exceeds the permissible limit, wear of parts increases intensively and can lead to a significant increase in fuel and operating materials consumption, to a strong emission of toxic substances that pollute the atmosphere and to a decrease in the efficiency of the car.

When designing cars and their engines, as a rule, they are designed to work in a temperate flat climate, although various natural and climatic conditions, especially extreme ones, have a significant impact on the reliability of operation and wear resistance of engines.

Due to the fact that the climatic conditions of the European zones are moderate, we believe that the influence of such operating conditions on the process of wear of machine parts is minimal in comparison with other extreme cases. When operating cars in temperate climatic zones, the main influence on the wear of parts is mainly provided by the technical factors of maintenance and repair.

A large number of cars are operated in the climatic conditions of the Far North and in hot, dry, highly dusty zones of Central Asia.If the temperature in the Far North in winter drops to -50⁰ C, then in Central Asia the heat can reach +50⁰ C and higher. Let us consider what effect these climatic operating conditions have on the intensity and type of wear of car parts.

Due to the fact that engine parts are subject to the greatest friction and wear, as well as 43% of all costs for spare parts of a car fall on the engine, in order to reduce a large amount of work, we consider it appropriate to further consider the nature and degree of influence of climatic conditions on the intensity of wear parts as applied to the engine [15]. 

There are the following main types of wear of engine parts: abrasion and scuffing of rubbing surfaces. Under normal operating conditions of the engine, mainly abrasion occurs on the cylinder liners, piston rings, liners and bearings. The nature of abrasion can be mechanical, corrosive and abrasive. Under normal operating conditions, it is the abrasion of the parts that determines the life of the engine. The table shows the components of the total operational wear of cylinders of automobile engines for the temperate climatic zone and the Far North [5].

Table.

Components of total wear of cylinders of automobile engines in operation (in percent)

* When transporting ore.

** Including unsettled engine operation modes in terms of speed and load.

Engine operation in the Far North in the cold season is considered extremely difficult. Extremely low ambient temperatures can cause a drop in power and increase fuel consumption, cylinder seizure and others. With a decrease in the temperature of the cooling liquid from 80⁰ C to 60⁰ C, the wear of parts increases by 30%, and with a decrease to 40⁰ C - by 140% [13]. In this case, the wear of parts is corrosive and with a decrease in the temperature of the coolant of the cooling system, the magnitude of this type of wear increases greatly.

Changes in the rate of wear of engine cylinders at low temperatures are due to the following reasons: the presence of semi-dry friction between the cylinder walls and piston rings; corrosive destruction of the surface layers of metals.

Reduced thermal conditions, including cold starts, unsteady modes, increased load and speed modes, as well as the rigidity of the working process, affect the wear rate of engine parts in different ways. However, in ordinary operation, the wear of parts of the cylinder-piston group is most influenced by abrasive dust, which gets into the engine from the ambient air in various ways [6,8 ].

High and dry ambient temperature contributes to the appearance of knocking combustion in the engine, which is also one of the reasons for the increased wear rate of the cylinder, piston rings and piston. It is known that with a strong detonation, the engine overheats, as a result of which a molecular-mechanical type of wear, fumes and breakage of compression rings and piston grooves can occur. 

High heat with ineffective operation of the cooling system leads the engine to overheating, as a result of which the engine power decreases, and the specific consumption increases.

The climate in Central Asia is sharply continental: summers are long and very hot, and winters are short and cold. During the day, the absolute maximum air temperature in the shade reaches + 45⁰ C, +47⁰ C, sometimes +50⁰ C and more, and at night it drops to + 5⁰ ... 10⁰ C. In mountainous regions, after intense heat (40-47⁰ C), a car passing through mountain passes falls into conditions when the air temperature is 0-1⁰ C, i.e. a sharp drop in temperature is 40-46 ⁰ C. At a mountain height, the density and pressure of air decreases by 18.5% and 21.5%, respectively (at an altitude of 2000 m above sea level) [13].

As a result, the filling of the cylinders decreases, the mixture is enriched, incomplete combustion and smoke of the engine occurs, excessive fuel consumption and intensive wear of the parts of the cylinder-piston group.

Road and atmospheric dust has a significant effect on the wear rate of parts. The dust content of the air in a significant part of the territory of Central Asia reaches 3.5 g / m3, and during strong winds and storms -17 g / m3, which is more than 10 times higher than the dust content of the air in the temperate zone (0.003 ... 1.42 g / For clarity, it is enough to say that when the air is dusty 0.8-1.2 g / m3, visibility is completely lost [6].

Dust getting into the engine causes abrasive wear of its parts. This is due to the fact that the dust contains quartz, the content of which ranges from 50 to 95%. The hardness of quartz (1000-1200 kg / mm2) is greater than the hardness of structural materials, which is why it causes abrasive wear of rubbing engine parts. Underestimation of this factor in the design and operation of the engine can lead to an unjustified increase in the intensity of wear of parts and a sharp decrease in its reliability [5, 6].

Abrasive particles that enter the engine have different effects on the wear of its parts. Abrasive dust entering the engine together with air and fuel causes the greatest wear of the cylinders in the upper part, i.e. in the zone where the piston stops at top dead center, the upper compression rings and piston grooves. Abrasive particles entering the engine along with the oil cause the most wear on the crankshaft bearings, mid-section cylinders, oil scraper rings, piston pin and bushings (Fig. 1).

Figure 1. The degree of influence of an abrasive dust particle on the process of wear of engine cylinders under various operating conditions [3]:
1-moderate natural and climatic conditions; 2-moderate dustiness of the air (0.4 g / m3); 3- oil contaminated with abrasive dust; 4-intake of dust into the engine with air and oil; 5-boost engine operation in dusty air, oil and fuel

Figure 1 shows that with an increase in the amount of dust entering the engine along with air, fuel and oil (line 5), the wear rate of its parts increases and in this case the wear is abrasive. It should be noted that the wear rate of rubbing parts depends on the ratio of the surface hardness of parts and abrasive particles. The lower the surface hardness of the parts and the higher the hardness of the abrasive, the greater the abrasive wear.

An increase in fuel temperature affects its density and viscosity. A decrease in density and viscosity causes a decrease in the mass supply of fuel to the cylinders, and increases the amount of fuel flowing through the gaps in the plunger pairs. In this case, the high temperature of the fuel pump causes semi-dry and dry friction in the plunger pairs and parts lubricated with fuel, which leads to their intense wear. The listed reasons lead to a decrease in the service life of the fuel equipment by 1.5-2 times compared with operation at normal temperature. 

This, the analysis of the influence of various factors on the wear process allows us to draw the following conclusions: the wear of automobile engine parts is influenced by many factors, such as load and speed modes of operation, which mainly determine the magnitude of molecular-mechanical wear and thermal mode of operation, including periods start-up and warm-up, which determined the value of corrosion-mechanical wear.

From this it follows that with insufficient protection of the engine from dust particles of pollution, abrasive wear of parts sharply increases and this becomes of particular importance for vehicles operating in the conditions of the Central Asian zone, where there is a high temperature and dustiness of atmospheric air.

We believe that the most affordable and cost-effective way to reduce wear of engine parts is to effectively clean air, fuel and oil and seal all places where dust can enter the engine.

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