RU2447416C1 - Method of defining ice pressure at compression stroke end - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed method consists in that ICE is accelerated to normal opening rpm by means of additional power source. Said additional power source is disconnected, fuel feed to ICE is shut off and said additional sourced is connected again thereto. ICE cylinder pressure is measured simultaneously with cylinder surface temperature measurement. Measurements are made at two points. Taken-off values are used to plot pressure-to-temperature graph. Note here that compression pressure magnitude represents pressure on horizontal section of said graph.

EFFECT: higher accuracy.

2 dwg

Description

The invention relates to measuring technique, namely to determining the technical condition of internal combustion engines by pressure in the cylinders at the end of the compression stroke, and can be used to diagnose the condition of piston machines indirectly.

The pressure measurement at the end of the compression stroke is carried out to assess the quality of the seal of the cylinder-piston group of the internal combustion engine, on which the gas leak from the working space and, as a consequence, the engine power and fuel and oil consumption depend.

A known method for determining the pressure at the end of the compression stroke (see AS USSR No. 1059459, 02.25.82, G0L 23/00), based on the supply of gas under pressure in the cylinder of the internal combustion engine to prevent ignition of the fuel, which allows using the sensor pressure register the pressure in the cylinder while the engine is running.

The disadvantage of this method is the lack of accuracy in determining the compression pressure associated with the error due to the significant influence of the temperature of the cylinder walls on the value of the measured parameter. Thus, for a more accurate pressure measurement, it is necessary to take into account at what temperature the measurements were made and the temperature of which point of the cylinder was taken as the control value, which accordingly complicates the measurement process.

The closest analogue of the proposed solution is the method common in the practice of diagnosing ICE (see textbook for universities Authors Lukanina V.N., Morozova K.A. et al., Vol. 1 "Theory of work processes." - M .: Higher School, 2007 .-- S.466-467). The known method is based on determining the pressure at the end of the compression stroke by simultaneously measuring the pressure and temperature of the engine while cranking the internal combustion engine crankshaft with an external source of energy without supplying fuel to the latter.

The method is as follows.

Using an external source of energy, the internal combustion engine is brought to the operating mode, then the fuel supply is shut off and the crankshaft of the heated engine is turned using the same source. An electric motor can serve as an extraneous source of energy, if the diagnosis is carried out on a stand described, for example, in the manual of author. Stefanovsky B.S., Skobtseva E.A. and others. "Tests of internal combustion engines. - M .: Mechanical Engineering, 1972. - S.62-64, or starter, if diagnosed with a car engine. As the ICE cools down, a pressure gauge or pressure sensor measures the pressure and at the same time the temperature at the end of the compression stroke. It is known that when the temperature decreases, the viscosity of the lubricants increases, which accordingly affects the readings of the device, therefore, in order to obtain undistorted parameters, it is necessary to maintain the temperature regime of the cylinder walls constant. However, in the known method, this condition is not satisfied, and the fact of changing the properties of lubricants in the determination of pressure is not taken into account.

The disadvantage of the above method is the lack of accuracy in determining the pressure at the end of the compression stroke due to the unaccounted for influence on the removed parameters of the properties of lubricants that change with temperature.

The inventive method allows to obtain a new technical result compared to the prototype, which consists in increasing the accuracy of determining the pressure at the end of the compression stroke, taking into account the influence of the properties of lubricants on the value of the readings.

To achieve the specified technical result, the following set of essential features is used: in the method for determining the pressure of the internal combustion engine at the end of the compression stroke, as well as in the prototype, the internal combustion engine is put into operation using an additional energy source, then the additional source is turned off, the fuel supply is shut off in the internal combustion engine and again connect an additional energy source to it, after which the pressure in the internal combustion engine cylinder is measured and at the same time the temperature on its surface, unlike According to the measured values, the pressure is plotted against the temperature and the pressure on the horizontal section of the constructed dependence is taken as the pressure value.

The essence of the method lies in the fact that, in contrast to the prototype, where the compression pressure is determined by the readings taken at any arbitrary point in the cooling period of the engine, in the proposed method, to obtain reliable data on the specified parameter, readings are taken only at a certain section. Since the compression pressure, as mentioned above, due to the influence of the viscosity of lubricants increases with decreasing temperature of the internal combustion engine, the parameters obtained in the well-known analogue may not correspond to the actual characteristic of the technical condition of the cylinder-piston group. In contrast, in the proposed method, only those readings are taken into account that do not change with temperature, i.e. are located on a horizontal plot of pressure versus temperature.

Comparison of the proposed method and the prototype showed that the task - improving the accuracy of determining the pressure at the end of the compression stroke - is solved as a result of a new set of features, which proves the conformity of the proposed invention with the patentability criterion of "novelty".

In turn, the information search in the field of measuring technology did not reveal solutions containing individual distinctive features of the claimed invention, which allows us to conclude that the proposed method meets the criterion of "inventive step".

The essence of this method is illustrated in the drawing, where

figure 1 presents a diagram of a device that implements the specified method;

figure 2 is a graph of pressure at the end of the compression stroke on the temperature of the cylinder walls.

To implement the method, a device is used (Fig. 1), consisting of an internal combustion engine 1, paired and driven by an electric motor 2, pressure sensors 3 installed in the cylinders 4 of the internal combustion engine 1 and outputting pressure values from the angle of rotation of the crankshaft 5 on the PC 6, chromel-kopel thermocouples 7, displaying the temperature values on the temperature meter 8 in the region of top dead center 9, the valve 10 installed in the fuel line 11 connecting the internal combustion engine 1 to the fuel tank 12 and used to shut off the fuel supply to the internal combustion engine 1 when scrolling the engine from the electric motor 2.

Figure 2 shows the dependence of the compression pressure on the temperature of the cylinder wall, which can be represented as follows:

where p _c is the pressure at the end of the compression stroke; p _railway - the liquid component of the pressure at the end of the compression stroke; T is the temperature, p _gr is the boundary component of pressure. P _train component - is the proportion of the pressure p _s, the sealing effect provided by the lubricating fluid layer (oil) between the cylinder sleeve surface and the piston rings; the value of p is determined _railway viscosity properties of engine oil, i.e. is a function of temperature. The constituent p _gr is the fraction of pressure p _c provided by the gaps between the rings and the cylinder wall, and therefore is determined by the condition of the rubbing surfaces and the thickness of the adsorbed oil layer — the boundary film — on the friction surfaces of the cylinder bushing and rings; pressure p _gr does not depend on temperature. As a value characterizing the pressure at the end of compression, the value of p _gr corresponding to the horizontal section of the dependence p _c (T) is taken, i.e. parallel to the abscissa axis.

An example implementation of the method

The pressure at the end of the compression stroke in the cylinders of the D120 diesel engine was determined by specialists of the St. Petersburg State University of Water Communications in laboratory conditions. The tests were carried out on a diesel bench equipped with a three-phase induction motor 2, the shaft of which is paired with the crankshaft 5 of diesel 1. The gas pressure in the cylinders was measured using pressure sensors 3, and the temperature of the cylinder walls using chromel-kopel thermocouples 7. Diesel 1 was brought to predetermined mode, then stopped, while the fuel supply from the fuel tank 12 was shut off by the valve 10, after which the electric motor 2 was turned on to crank the crankshaft 5 of diesel 1. When cranking as the diesel cools down, the pressure p _{c was} periodically recorded through a PC 6 and the corresponding temperature T _cyl of the cylinder walls in the region of the top dead center 9. According to the readings, the dependence p _c (T _cyl ) was constructed (Fig. 2). As can be seen from the graph, the compression pressure has a constant value in the area from 120 ° to 95 °. Further, as it cools, it begins to increase due to the influence of oil viscosity on it. Thus, for this example, 4.60 MPa corresponds to the exact value of the compression pressure, which can be used to judge the technical condition of the cylinder-piston ICE pair with greater objectivity.

The above allows us to conclude that the invention meets the criterion of "industrial applicability".

Claims (1)

The method of determining the pressure of the internal combustion engine at the end of the compression stroke, which consists in the fact that the internal combustion engine (internal combustion engine) with the help of an additional energy source is put into operation, then the auxiliary source is turned off, the fuel supply to the internal combustion engine is shut off and the additional energy source is reconnected to it and then measure the pressure in the cylinder of the internal combustion engine and at the same time the temperature on its surface, characterized in that the measurements are taken at several points, according to the values taken, the dependence of pressure and temperature are taken as the pressure on the horizontal section of the constructed dependence.

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