Method for diagnosing the ICE cylinder-piston group in the com- 1 bustion chamber in the mode of cranking the engine crankshaft

. To increase the diagnostic efficiency, significantly reduce the unpro- 10 ductive time, and mainly increase the reliability and accuracy, we propose a new 11 method and tools implementing it - an oscillographic method for monitoring the pres- 12 sure and phase parameters during the dynamic change in the operating parameters. The 13 proposed work is aimed at improving the internal combustion engine (ICE) perfor- 14 mance by timely diagnosing the cylinder-piston group (CPG) and its maintenance 15 based on the diagnostic results. The scientific novelty of the work lies in the estab- 16 lishment of the interconnection of the CPG parameters obtained in the test modes of 17 the ICE operation, allowing us to justify the diagnostic modes and their limiting val- 18 ues; the development of diagnostic methods and tools allowing us to justify the test 19 modes for diagnosing the ICE CPG; the experimental data, which revealed that the in- 20 stantaneous pressure signal in the combustion chamber is a sensitive diagnostic sign, 21 which reflects the technical condition of the ICE CPG and its elements; the results of 22 the experimental studies of diagnosing the ICE CPG in test modes. The results of the 23 experimental work were compared with the results of theoretical modeling, the con- 24 vergence between them was 97–99%. The production validation of the new method demonstrated the reliability within 0.92–0.97.


Introduction
We have established that the lack of diagnostic tools reliably determining the 32 technical condition of the CPG, together with the generalized costs for restoring com-33 ponents and mechanisms (connecting rod and piston group, cylinder heads, valve of 34 the gas distribution mechanism, cylinder head gasket) can reach 2300 € depending on 35 the car model. A critical approach to determining the disadvantages and advantages of 36 various CPG diagnosing means allowed us to determine the main disadvantage, which 37 is the prohibitively long time of preparatory and final operations, low reliability, and 38 unacceptable sensitivity. The above conclusion applies to the cylinder-piston group 39 and rings. The purpose of the work is to develop an in-place oscillographic method for 40 monitoring the pressure and phase parameters during the dynamic changes in the oper-41 ating parameters. 3 failure of the combustion chambers, and the displacement of the GDM phases leads to 48 significant emissions of exhaust gases into the atmosphere, as well as to an increase in 49 the fuel and oil consumption, and a decrease in road traffic safety. In the operating 50 practice, wear is formed smoothly provided that all the technical conditions are satis-51 fied. However, in practice, ICEs are operated in the most severe conditions: high tem-52 perature, gaseous environment, high cyclic loads [4,5,6]. Under these conditions, the 53 law of the change in the technical condition takes an exponential form. Failures occur 54 instantly, and it is most important at this moment to assess the condition [7,8]. 55 The issues of technical diagnostics of the engine CPG and GDM have been 56 studied by some researchers.

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Also these authors presented results of application of the artificial neural net-79 works for diesel diagnostics based on the results of a spectral analysis of engine oil.

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Artificial neural network has been created and trained to identify pre-failure condition 81 of the details of cylinder-piston group and crank-And-rod mechanism using the diesel 82 locomotive 49 as an example [12].  The studies of the evaluation of combustion chamber leakage of four stroke ma-  The diagnostic model was based on parameter estimation using the Levenberg-103 Marquardt method and results showed a high degree of confidence.

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Methodology that can be used as a diagnostic tool to determine the compression 105 condition of diesel engines is developed in [17]. An experimental investigation is con-106 ducted to examine the effect of the initial pressure at the inlet valve closure, the com-107 pression ratio and the blowby on the cylinder pressure trace. From analysis of the 108 measured data, it is followed that each parameter has a different effect on the different The existing routine maintenance strategy presupposes maintenance and appli-117 cation diagnostics included in it [19]. As the circumstances require, the strategy is 118 most often applied in cases of extreme wear. External diagnostic tools, which include 119 compression testers, leak indicators, pneumatic testers, and flow meters, are used for 120 the existing system of scheduled preventive maintenance and repair. Using the above 121 diagnostic methods, the time of the preparatory work can be up to 90% of the total di-122 agnostic process period [14,16,20]. At the same time, the accuracy and reliability re-  The main purpose of the theoretical research is to establish the relationship be-133 tween the pressure parameters and phase parameters with the technical condition of 134 the CPG in the dynamic mode of testing. 135 We will take the specifications of the widely used ZMZ-406 engine as a calcula-136 tion basis and introduce the boundary conditions. The main condition for the initial 137 state of the system will be the adiabatic compression process, which is an ideal process 138 without any exchange with the atmosphere [22,23]. In the theory of thermodynamic 139 7 calculations, such a system is called closed and used to simplify the calculation of the 140 ICE operating cycles [24,25,26]. In such an ideal system, the output parameters of the 141 operating cycle, pressure and phase, and temperature parameters are uniform in vol-142 ume, and local drops and gradients are not taken into account in the calculations. In 143 fact, in real conditions, the main and accompanying processes seem to be more com-144 plicated for theoretical calculations [27,28]. At the initial calculation stage, we apply 145 the well-known formula: where Р is the pressure in the working chamber of the cylinder, Pa; V is the volume of 148 compressed air, mm 3 ; µ is the molar mass of the air or fuel-air mixture depending on 149 the mode; R is the universal gas constant, J/kg; Т is the operating temperature of the 150 compression process in the cylinder, K.

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Let us represent the condition for the implementation of the ideal adiabatic pro-152 cess, which has the form: where k is the characteristic of the adiabatic process (equal to 1.4 for our variant).

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The working stroke of the ZMZ-406 engine piston can be determined by degrees 156 using the formula known in the tractor industry: 8 where φ is the geometric angle characterizing the arc of the crankshaft rotation from 159 the zero value taken as the counting base, rad; is the working radius of the crank-160 shaft journal, mm; λ is a parametric coefficient.

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Let us calculate the dependence of the piston stroke on the crankshaft rotation 162 angle when substituting the data into equation (3), which results in a graph shown in For the subsequent calculation of the pressure and temperature value of the 176 compression process, we make calculations according to equation (4), based on which 177 we obtain the dependence shown in Figure 2. The calculation of the characteristic of the change in the volume in the space 183 above the piston shown in Figure 2 indicates the typical minimum and maximum 184 points, which correspond to the points of 180 and 0 degrees.

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Let us use the ratio between the pressure and volume values, which results in the 186 formula for calculating the pressure value in the combustion chamber (Р 2 ) depending 187 on the variation of the working volume of the space above the piston: where Р 1 is the pressure in the combustion chamber corresponding to the beginning of

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One of the calculation conditions is to assume that at the initial counting mo-214 ment, the air temperature in the space above the piston is at the level Т 1 =293°K.

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For further calculations of the pressure value (Q) in the combustion chamber, 216 taking into account heat transfer, we calculate the instantaneous amount of heat trans-217 ferred by the air during compression to the cylinder head and the working walls of the 218 combustion chamber, depending on the change in the ICE crankshaft rotation angle.

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Against this background, the calculation formula will be as follows: where t is the time of the engine crankshaft rotation at an angle φ, s; is the air heat 222 transfer coefficient, W/m 2 ·K; is the area of the cylinder and combustion chamber 223 walls, through which the heat is transferred, mm 2 , = + ;.

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The air heat transfer coefficient is a function of pressure and temperature in the 225 cylinder and is determined by the following dependence: Substituting the data of Т 2 and P 2 in equation (8), we obtain the dependence 228 shown in Figure 4. An analysis of Figure 4 shows that the maximum value of the heat transfer coef-234 ficient corresponds to a pressure of 12.5-13.0 bar.

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After the heat is transferred to the cylinder walls, the air temperature in the cyl- For the variant when the pressure value changes according to equation (15), the 287 temperature will also change according to the nonlinear dependence, which gradient 288 depends on the adiabatic coefficient:   An analysis of the graph in Figure 10 shows that the pressure sensitivity at the 410 end of the compression stroke also takes on the maximum values at low engine speeds 411 (100 rpm).

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To calculate the displacement of the maximum pressure phase depending on 413 various diagnostic modes, we carried out experimental studies, which resulted in a de- An analysis of the graph in Figure 12 shows that the phase sensitivity coefficient