Метод исследования формоизменения шатунных вкладышей коленчатого вала автомобильного двигателя в эксплуатации (на примере КамАЗ-740)

<div class="htmlview paragraph">Very few data seem to be available on the frictional losses in automobile engines caused by the failure of the oil to perform its function as a lubricant. The researches of the Lubrication Inquiry Committee in England indicate that the friction of a flooded bearing is proportional to the speed of the engine, the area of the bearing and the viscosity of the lubricant and is independent of the pressure and of the materials of which the opposing surfaces are composed.</div> <div class="htmlview paragraph">The principal sources of friction in an engine are the crankshaft, the camshaft and the connecting-rod bearings, which rotate; the pistons and the valves, which slide; and the auxiliaries, such as the generator, the pump and the distributor. Experiments by the author led to the conclusion that a variation in the viscosity of the lubricant can easily account for reduced mechanical efficiency and consequently for the increased consumption of gasoline, and that the friction-loss is proportional to the cubic capacity of the engine, whereas the brake mean effective pressure for the same horsepower is inversely proportional to the capacity. Tables are given showing the variation of the friction mean effective pressure at various speeds and at various temperatures of the water and the oil, the fuel consumption of the engine at part throttle and at varying oil and water temperatures and a method of calculating the reduction of the gasoline consumption, assuming a constant indicated thermal efficiency. The identity of the results, as determined from the friction curves and from actual tests, is said to suggest that the thermal efficiency is affected but little by the water-jacket temperatures and that the saving on account of the thermostats and the radiator shutters is caused almost entirely by the reduction in the viscosity of the oil. Because of thermostatic control the water temperature rises very rapidly to 120 deg. fahr. in short runs and to about 170 deg. fahr. after 15 or 20 min., but the oil temperature, even for periods of 30 min. of city driving, does not rise more than 40 deg. fahr. above atmospheric temperature, and after prolonged fast driving the rise amounts to about 90 deg. fahr. On the assumption that the temperature-difference between the oil and the atmosphere is independent of the atmospheric temperature, it is shown that to obtain a mean oil and water temperature of 170 deg. fahr., the condition of maximum efficiency, with water at 170 deg. fahr., the atmospheric temperature must be about 80 deg. fahr. if the car is driven at approximately 40 m.p.h., while for ordinary city driving the conditions of maximum efficiency are not realized unless the atmospheric temperature is about 130 deg. fahr. The suggested use of thin oil might not avail because in winter very severe conditions of load and speed are frequently encountered and a slight difference in the viscosity might be of great importance.</div> <div class="htmlview paragraph">In making a study of methods of keeping dirt out of an automobile-engine crankcase, it was found that certain oils that worked well under normal conditions became too viscous in cold weather. This was remedied by making the troughlike conduit to the pump suction of wire gauze through which the oil when sufficiently hot drops into the main body of oil in the oil-pan. The property of oiliness increases in importance as the bearing surfaces more nearly touch each other, and especially when the engine is starting from rest.</div>

<div class="htmlview paragraph">Diesel engine fuel consumption is mainly a function of engine component design and power requirements. However, fuel consumption can also be affected by the environment in which the engine operates. This paper considers two controlling parameters of the engine's thermal environment, oil temperature and coolant temperature. The effects of oil and coolant temperatures on Brake Specific Fuel Consumption (BSFC) are established for a turbocharged diesel engine. Data are also presented for a direct injection, naturally aspirated diesel engine.</div> <div class="htmlview paragraph">A matrix of test conditions was run on a Cummins VT-903 diesel engine to evaluate the effects of oil and coolant temperatures on BSFC for several loads and speeds. Loads and speeds were selected based on where a typical semi-tractor engine would operate over the road on a hills and curves route. Oil temperature was monitored and controlled between the oil cooler and the engine. Coolant temperature was monitored and controlled at the engine outlet. The BSFC data were fit to a regression equation as a function of load, speed, oil temperature and coolant temperature for the matrix of test conditions. The test results showed that BSFC decreases as both oil and coolant temperatures increase. The results also indicate that BSFC was more sensitive to changes in oil temperature than to changes in coolant temperature over the range of the test data.</div>

<div class="htmlview paragraph">This paper describes the features and capabilities of a comprehensive yet flexible computational tool ORBIT developed for analyzing journal bearings (e.g. connecting rod bearings and crankshaft bearings) in internal combustion engines. Several techniques for solving the hydrodynamic Reynolds Equation have been developed within this methodology which can be used appropriately by bearing designers/analysts depending on the level of detail required. Besides ideal circular bearings, this simulation tool also enables the analyst to consider the influence of a) non-circular journal bearing geometry, b) oil-feed holes/grooves, c) surface roughness, d) journal misalignment, e) rise in oil temperature and f) bearing elasticity effects (EHL) on bearing performance. The capabilities of the simulation code are demonstrated through a series of validation and case studies.</div>

In this paper, the effects of clearance between piston and cylinder and oil viscosity index on the friction of area between the piston and cylinder of an internal combustion (IC) engine were investigated experimentally and theoretically. To this end, two values of 33 and 66 µm for the piston clearance, and two types of engine oil namely SAE10W40 and SAE20W50 were considered. To carry out the experiments, the engine was run under motored condition. The experiments were implemented at different oil temperatures and engine speeds. Based on the experimental results, although reduction in the piston clearance and the use of 20W50 oil caused an increase in the friction, but the effects of these two parameters became less with an increase in oil temperature and engine speed. The experimental results showed that the effect of clearance on the friction was more noticeable for low speeds. The maximum influence of the piston clearance decrease on the friction was 16% with the use of 20W50 oil at 1000 r/min when the oil temperature was 35 °C. The minimum influence of the piston clearance on the friction was 0.5% when the oil temperature was 90 °C and the engine speed was set on 6000 r/min. The theoretical results showed that the most contribution of the friction of piston/ring/cylinder assembly belonged to the piston skirt. Moreover, the effect of the piston skirt on the friction at high speeds was more than that of the piston rings. The friction value of the piston rings was not significantly altered by changing the engine speed, but it was considerably changed by the oil temperature variation. Whereas the piston skirt friction had an increasing trend with the speed rise, the change in the engine oil temperature, especially for low temperatures, had no significant effect on the piston skirt friction.

The relationship between oil temperature, convective heat transfer coefficient, and heat flux during immersion frying was investigated. Potato cylinders were fried in 120, 150, and 180C oil and convective heat transfer coefficients and heat flux measurements were made. These measurements followed the expected trends predicted by fundamental heat transfer calculations. the maximum convective heat transfer coefficient and heat flux reached during frying increases as oil temperature increases. the process time to reach these maxima decreases as oil temperature increases. This research provides fundamental knowledge relevant to the effects of oil temperature on the coupled heat and mass transfer problem present during immersion frying. This knowledge will provide a first step towards better understanding the frying process, and eventual process optimization through manipulation of the time-temperature regime of the frying processes.

<div class="htmlview paragraph">This paper describes the development and application of a method for detecting bearing damage occurring in diesel engines during production engine test. The method involves the analysis of a special lube oil filter disc for content of the trace element silver which has been added to the engine main and connecting rod bearings. Use of the procedure eliminates the cost of disassembly of production engines to check for bearing damage before shipment.</div>

The solution to the problem of increasing the resource of an internal combustion engine (ICE) is directly related to the reduction of energy losses to overcome friction in the elements of systems, mechanisms and complexly loaded tribounits. A special place among the mechanical friction losses is occupied by the hydromechanical friction losses in the ICE tribounit. A complex loaded tribounit is characterized by loadings that are variable in time and magnitude, at which the position of the movable element in conjunction is characterized by high eccentricities. Such a complexly loaded tribounit includes the main and connecting rod bearings of the crankshaft, the interface “piston skirt-cylinder liner” and “piston ring-cylinder liner” and thrust bearings of the ICE, etc. The only way to reduce oil starvation is to texturize the contacting surfaces, which will increase the bearing capacity of a heavily loaded bearing by creating many “micro wedges”. In particular, the texturing of the surface of the liners of the crankshaft bearings can be performed in the form of elliptical pits, which allow the oil to be stored on the friction surface under any operating conditions of the diesel engine. The article provides an overview of the main types of micro-texturing of a friction surface tribounit. The calculation model was created and the program of calculation analysis “crankshaft journal bearing” was developed. The calculations of hydromechanical characteristics are performed for various types of micro-texturing by the example of a connecting rod bearing in a diesel engine for commercial vehicles.

Monitoring the insulation status of a transformer requires the availability of accurate information of the oil temperature at any moment. Considering the importance of oil temperature prediction in oil-immersed transformers and its direct relation with the life of transformer, a novel model is presented in this paper using the concept of thermal resistance with consideration of solar radiation for expressing the heat transfer in distribution transformers. The results of the proposed model are compared and validated with experimental results. These results show that in the studied transformer and rated loading, solar radiation can increase the oil temperature by about 3.7 °C. In this paper, the thermal resistance model with solar radiation is used to predict the thermal behavior of the transformer in overloading condition. Finally, the transformer operation with/without consideration of solar radiation effect is studied and its impact on the transformer's loss of life due to the increase in oil temperature is investigated. In order to consider the effect of solar radiation on oil temperature, new equations using the concept of thermal resistance are presented to calculate the shadow surface created on the fin-folded transformers, and a novel equation is proposed for permissible loading of distribution transformers.

Traction measurements for two kinds of synthetic naphthenic traction oils were carried out, using a two-roller machine. The Eyring stress and shear modulus of test oils were estimated simultaneously by a curve-fitting procedure based on the nonlinear viscoelastic model introduced by Johnson and Tevaarwerk. As a consequence, it has been found that the Eyring stress decreases with an increase in contact pressure, and it increases with oil temperature. It has been also clarified that the effective shear modulus, including the effect of the roller compliance, decreases with an increase in contact pressure. At higher pressure it decreases as the oil temperature increases, whereas at lower pressure it increases with the oil temperature. In addition, the influences of operating conditions such as the kind of oil, pressure, and oil temperature upon the Eyring stress, shear modulus, and traction coefficient were also investigated. It has been shown that under the operating conditions where the effect of oil viscosity is predominant, the accuracy of the shear modulus calculation deteriorates when the shear modulus is estimated by assuming that the oil is perfectly elastic.

In present study, a gear transmission system was used to evaluate the effects of oil viscosity, speed, oil temperature as well as the applied load on torque efficiency. The experimental results reveal that the efficiency is increased with the increasing oil temperature and/or applied load whether the multigrade or singlegrade oil was employed. Under a constant torgue, the power loss is increased with the increasing pitch line velocity. The above characteristic resulting from the use of high-viscosity oil yields the substantial variations. However, as the oil film thickness is quite small, the viscosity speed, oil temperature and applied load produces the limited effect on torque efficiency, It indicate that EP additives create an opposite effect on torque efficiency at poor lubrication.

Moisture loss and oil adsorption kinetics, structural properties (apparent density, true density, specific volume and internal porosity), color changes and viscoelastic behavior (compression tests, crispness) were investigated during deep fat frying of french fries. The effect of frying conditions (oil temperature, sample thickness and oil type), drying pretreatment and osmotic dehydration pretreatment on the above properties was also examined. The results showed that oil temperature and thickness of potato strips have a significant effect on oil uptake, moisture loss and color parameters of french fries, while the use of hydrogenated oil in the frying medium does not affect these properties. The porosity of french fries increases with oil temperature increases and sample thickness and it is higher for products fried with hydrogenated oil. Maximum stress and maximum strain increase during frying, while crispness of potato strips is higher for hydrogenated oil, and lower for refined oil. Air drying and osmotic pretreatment increase porosity of fried potatoes but decrease their oil and moisture content. A negative effect on color development with drying time was also observed. Pre-fry drying as well as osmotic pre-treatment increases the maximum stress and maximum strain of french fries during frying. Air drying pre-treatment increases the crispness of potato strips while osmotic pre-treatment does not affect it, with the exception of sugar solutions.

Thermo-mixed-hydrodynamics of compression rings and big-end bearings are presented. Frictional losses under normal engine operating conditions for a gasoline engine and those with cylinder deactivation (CDA) are predicted. With CDA, the combustion chamber pressure increases in the active cylinders, whilst some residual pressure remains in the deactivated ones. For the former, the increased in-cylinder temperatures reduce viscous friction, whilst reducing the load carrying capacity, promoting increased boundary interactions. In deactivated cylinders, lower contact temperatures yield increased viscous friction. Overall, a 5% improvement in expended fuel is expected with the application of CDA. However, 10% of these gains are expended due to increased friction. The study demonstrates the need to consider total system effects when introducing new technologies such as CDA.

THE INFLUENCE OF FAULTS IN THE LUBRICATION SYSTEM ON THE DAMAGE OF THE ENGINE BEARINGS

This article presents the analysis and results of analytical, calculation, and design solutions for the development of piston engines for aircraft (tractors, automobiles, etc.). The authors propose an original design of a W-shaped engine with trailer connecting rods and made a comparative analysis of design features. The main feature of the W-shaped engine design is a significant reduction in length, and, consequently, the length of the crankshaft. As known, the manufacturing of internal combustion engine crankshafts is a long, complex, and expensive procedure requiring a number operations for its mechanical and heat treatment. An important aspect of crankshaft design is the calculation of mechanical tension, torsional vibrations, and the hydraulic performance evaluation of the main and connecting rod bearing, including engine balancing as a whole. At the end of the article the operating schemes of the engine section are presented (the section consists of four pistons, two main and two connecting rods bearing kinematically connected to one crankpin). The design differences from the classical schemes of crank-connecting mechanism (CCM) allow us to design the W-shaped engine in accordance with the technical requirements. For example, maximum power can be achieved by using variant “A”, with an increase in the power and heat stress of the parts of the cylinder-piston group (CPG), when the section is organized according to variants “B” or “C”, the loading of CCM parts is increased, but the loading of CPG parts is reduced. Considering that a W-shaped engine with trailed connecting rods has a same piston stroke in main and side cylinders and the workflow pattern in each cylinder is identical and is moved at the crankshaft rotation angle – which allows the engine to be designed according to variants above – the performance characteristics of such an engine are significantly expanded due to electronic control. The authors consider continuation of the work in the implementation of a full set of calculation studies taking into account the design features of the engine with a W-shaped design of CCM.

The lubrication state of connecting rod bearing has influence on the reliability and lifetime. It is necessary to analyze the lubrication state of connecting rod bearing to evaluate and design the lubrication performance. The connecting rod bearing hydrodynamic lubrication simulation model was set up for 9XX diesel engine and journal bearing fatigue test-rig at Glacier Vandervall. The effect of maximum oil film pressure, minimum oil film thickness and maximum asperity contact pressure on the lubrication performance were studied. Then the lubrication states of connecting rod bearings under different working conditions were discussed based on two test machines. The results are of great significance for analyzing the lubrication performance of connecting rod bearings and the reliability of bearings.