Environmental Control and Test Dynamic Control of the Engine Output Parameters

In modern transport, environmental control plays a key role in shaping the strategy for managing the technical condition of nodes and systems. The first step in reducing the toxicity of exhaust gas emissions was the introduction of EURO standards, successively from EURO-0 to EURO-6. Accompanying the appearance of EURO standards, exhaust systems were supplemented with catalytic converters, which deactivated most of the harmful emissions. Oxygen sensors also began to play a key role, the installation of which resulted in the appearance of feedback. Thus, the global automotive industry is closer to the controllability of the engine output parameters. However, there are not enough parameters, operating modes, and additional controls available for this purpose. The presented studies used a new method of selective control of exhaust gases in each cylinder. The following parameters were used for monitoring: the crankshaft speed, complete and partial (cycle-by-cycle) disconnection of cylinders, O2, CO, CO2, and CH. The mode was provided by the number of the engine’s disconnected operated cycles and the crankshaft speed. The control was performed by the internal adjustment of the fuel supply under the influence on the injection duration of the electromagnetic nozzle. During the research, we established the minimum values of the exhaust toxicity parameters during the test effects. This method with a combination of modes and parameters allows us to reduce the toxicity of exhaust gases and to improve the efficiency and effectiveness of vehicles.


INTRODUCTION
One of the main tasks of modern engine building is to improve the operational and environmental performance of internal combustion engines (ICEs) [1][2][3][4][5][6][7]. Due to the increased number of motor vehicles, the share of oil fuel consumption is constantly growing. Along with the increasing number of electric vehicles, ICEs are still the basis of the world transport fleet [8]. Until a complete transition to electric transport, considerable attention should be paid to monitoring the environmental parameters of ICEs [9][10][11].
Along with the development of fundamentally new ICE models, which require complex long-term studies and significant capital investments, it is essential to improve the existing ICEs and their diagnosing methods [12].
The main works of the leading scientists in the field of transport ecology are aimed at the development of new devices for the neutralization of exhaust emissions, systems for monitoring the parameters of exhaust toxicity, as well as selective adjustment of fuel supply when the technical condition of ICE systems changes [13][14][15][16]. The effectiveness of these solutions has been proven during the operation of completely new vehicle systems having no running time [17][18][19][20]. Ideal conditions for the operation of vehicles were in these studies. However, the realities of operation show that, in most cases, car owners, car fleets, and automobile enterprises are unable to provide ideal conditions for the operation and maintenance of vehicles [21][22][23][24]. The high complexity of troubleshooting in the main ICE systems affecting the environmental performance of vehicles also encourages the development of new troubleshooting methods to maintain the highest environmental vehicle class [25][26][27][28].
Thus, the purpose of the study is to increase the reliability of diagnosing ICEs by supplementing the composition of the measured parameters with the results of studying exhaust gases of individual cylinders in test modes [29].

THEORETICAL RESEARCH
The lack of diagnostic tools that reliably determine the factors affecting the environmental performance of ICEs leads to high costs for detecting the troubleshooting (about 3000...7000 troubles per car). Based on the analysis of the existing methods for assessing the factors affecting the environmental performance of ICEs and the wear of the main ICE systems, we can conclude that such elements as the cylinder-piston group (CPG) are a rather reliable system, and the CPG wear factor can be neglected. However, at the same time, we should have a way to control the technical condition of the CPG, preferably integrated into the ICE control system to be able to control the CPG at any time. An analysis of ICE element failures shows that the maximum number of them falls at electromagnetic nozzles, spark plugs, and the exhaust catalytic converter. Besides, these elements significantly affect the environmental performance of ICEs [30][31][32].
Given the aforesaid and according to the set purpose, we identified the following research tasks.
1. To identify the relationship between the technical condition of ICE elements and the toxicity parameters.
2. To develop a method for assessing the technical condition of electromagnetic nozzles, spark plugs, and exhaust catalytic converters by the toxicity parameters during selective exhaust gas sampling.
3. To develop diagnostic equipment and experimentally establish diagnostic test modes and control parameters to study the technical condition of ICE systems.
4. To justify the diagnostic method using the developed equipment, carry out comparative studies and show their effectiveness.

RESEARCH PROCEDURE
In the course of the experimental studies, the input parameters are: 1) the spark gap of the spark plug; 2) the change in the capacity of the electromagnetic nozzle; 3) the resistance of the catalytic converter. The controlled parameters include the temperature of the ICE coolant, the technical condition of the cylinder-piston group (CPG), the gas distribution mechanism (GDM), the oil temperature. The output parameters include the ICE crankshaft, СО, СО 2 , СН, О 2 . After that, the data was processed in the SigmaPlot software suite, the verification and comparative studies were carried out with the use of Excel and Mathcad.
As we can see from the graph in Fig. 1, the nature of the change in the concentration of СО 2 and NO x in the exhaust gases is rather similar. When the engine operates in the rich mixture zone at α = 0.55...0.9, the concentration of СО 2 increases almost linearly from 4 to more than 11%. At the same time, the concentration of NO x in the same range increases from 0 to 0.42%. The law of the change in the concentration of NO x can be almost taken as linear in this section. Next, we can see from Fig Then, at α > 1.05...1.10 the formation of NO х decreases, which is connected with a decrease in the combustion temperature. The nature of the change in СО 2 and NO x also remains the same in this range. Thus, we can indirectly judge on the value of NO x by the value of the concentration of СО 2 , with a good approximation. Notably, the given research material did not set the task to determine the dependence of NO x , but in our future work we will use a gas analyzer enabling to measure NO x .
To study the relationship between the spark gap of the spark plug and the ionization voltage, we studied this process. To this end, we artificially set the gaps of 0.5, 0.7 and 1.4 mm. At the same time, the air density in the chamber of the test device changed from 7 to 20 kg/m 3 . After that, we monitored the change in the increment of the secondary voltage dU2/dt, V/s (Fig. 2).  (2) where δ SP is an interelectrode gap of the spark plug, mm; dU2/dt is the growth rate of the secondary voltage, kV/μs; ρ is the air density in the plug gap, kg/m 3 .
The presented Eqs. (1-2) link the increment of the ionization voltage and the air density in the chamber of the test device with the breakdown gap of the spark plugs.
So, for example, at an interelectrode gap of 0.9 mm, the breakdown voltage U br (kV) will be higher for a smaller change in the secondary voltage dU2/dt (V/s) (Fig. 3). The analytical studies allowed us to establish that the limit value of the spark plug gap is a gap of 1.1 mm upwards and 0.3 mm downwards.
A joint analysis of the preliminary experiments on studying the relationship between the spark gap of the spark plug, the change in the capacity of the electromagnetic nozzle, and the resistance of the catalytic converter with the exhaust toxicity parameters showed their significant relationship. These studies allowed us to create a generalized mathematical model taking into account the composition of the exhaust gases to the catalytic converter with the technical condition of the spark plugs, electromagnetic nozzles, and the catalytic converter. All research results were summarized in a series of functional dependencies: where n is the crankshaft speed of the internal combustion engine, rpm; О 2 is the oxygen content in the exhaust gases, %; CH is the hydrocarbon content, ppm; CO is the carbon monoxide content, %; CO 2 is the carbon dioxide content in the exhaust gases, %; Z is the spark plug gap, mm; F is the capacity of the electromagnetic nozzle, %; R is the equivalent resistance of the converter, mm. The data was processed using the MatlabSimulink software suite. The calculation model is presented in Fig. 4. When processing the data in the MatlabSimulink software, we obtained the dependencies of various output parameters on the combination of three input parameters. So, Fig. 5 and Fig. 6 present the dependence of the concentration of СO 2 (%) in the exhaust gases on the equivalent resistance of the catalytic converter R (mm), the capacity of the electromagnetic nozzle F (%), and the spark plug gap Z (mm).  We can see from Fig. 5 and Fig. 6 that the concentration of СО 2 increases with a decrease in the equivalent resistance of the catalytic converter from 10 to 34 mm in the catalytic converter. The concentration of СО 2 decreases sharply with an increase in the capacity of the electromagnetic nozzles from 94 to 106%. The concentration of СО 2 increases with an increase in the spark plug gap from 0.3 to 1.1 mm.
A failure analysis of automotive catalytic converters shows that when their cross-section is reduced, cleaning of the working cylinders is significantly impaired. This causes the accumulation of exhaust gases and their return into the combustion chamber through the exhaust system, which results in an increased content of CO, CH, interrupted the mixture ignition, excessive fuel consumption, and a significant power loss. An increase in the capacity of the electromagnetic nozzles causes an over-enrichment of the fuel and, as a consequence, worsened fuel combustion and an increase in CO and CH emissions. A decrease in the capacity of the nozzles leads to excessive depletion of the mixture and an increase in NO and СО 2 . The increase in the crosssection of the spark plug gap leads to an increase in the power of the spark in the gap, but it simultaneously complicates the mixture ignition. Then, NO increases sharply. At the same time, a reduced spark plug gap leads to the appearance of a weak spark unable to ignite the mixture, which causes a sharp increase in CH.
We similarly built the dependences of the concentration of CO, CH, O 2 in exhaust gases on the equivalent resistance of the catalytic converter R the capacity of the electromagnetic nozzle F and the spark plug gap Z.
Let us analyse the change in the ICE crankshaft speed n (rpm) on the equivalent resistance of the catalytic converter R, the capacity of the electromagnetic nozzle F, and the spark plug gap Z (Fig. 7. and Fig. 8).  We can see from Fig. 7 and Fig.8 that the ICE crankshaft speed sharply increases with a decrease in the equivalent resistance of the catalytic converter from 10 to 34 mm. The ICE crankshaft speed increases with an increase in the capacity of the electromagnetic nozzles from 94 to 106%. The speed decreases in the interval of the change in the spark plug gap of 0.3-0.7 mm. It grows when the gap changes from 0.7 to 1.1 mm.

THE HEAT CALCULATION OF THE STUDIED ICE
Let us make a heat calculation to analyse the composition of the exhaust gases. Let us choose the source data for the calculation. It is well known that our experimental setup based on the ICE of a VAZ-2112 car has a compression ratio of ε =11. During the experiments, we used A-92 gasoline. Besides, the average elemental composition and molecular weight of A-92 gasoline was: carbon C = 0.855; hydrogen H = 0.145; molecular weight m T =115 kg/kmol. The lower heating value of A-92 gasoline can be calculated by Eq. (8) . (8) The theoretical amount of air needed to combust 1 kg of fuel is determined by Eq. (9-10): The excess air ratio is determined based on the following considerations. An injection engine power supply system is installed on modern engines, [30,31,32]. The usability of the injection supply system for the designed engine allows us to obtain, provided that an appropriate adjustment is used, both the power and the economic mixture α = 0.7...1.3 according to the assignment.
The amount of the combustible mixture at α=0.95 is determined by Eq. (11): The number of individual components of complete combustion products at K=0.5 and the adopted speed mode: Since the excess air ratio for the desired ICE varies within 0.7-1.3, substituting these values with an increment of 0.05 into Eqs. (12)(13)(14)(15)(16)(17), we obtain the following dependencies (Fig. 9).
We can see from the analysis of Fig.9 that with an increase in the excess air ratio α, the consumption of the combustible mixture increases, and the emissions of СО 2 and Н 2 О increase slightly. The emissions of NО х also increase due to a larger amount of free oxygen and an increased fuel combustion temperature, which results in the increase in the amount of molecular oxygen. Here, we presented a generalized calculation of the largest possible number of components of exhaust gases based on the main, well-known models from the course of ICE calculation and combustion process chemistry. Although in the next work, the concentration of NO x is controlled indirectly by the content of СО 2 . As we can see from Fig. 9, in the rich mixture zone at α = 0.7...0.9, we should steadily increase the amount of the combustible mixture to maintain the combustion process, while it can be seen that the total number of complete combustion products and the amount of N 2 sharply increase. In the poor mixture zone at α > 1.05...1.30, these parameters grow with the same dynamics. At the same time, the dynamics of an increasing concentration of СО 2 and Н 2 О is very low throughout the change in the excess air ratio α. Meanwhile, in the rich mixture zone at α = 0.7…0.9, the amount of Н 2 and CO changes insignificantly. In the poor mixture zone at α > 1.05...1.30, the amount of Н 2 and CO decreases dynamically. This is explained by better combustion completeness.

CHOOSING THE RESEARCH METHODOLOGY
We developed a research methodology to carry out all the planned complex works. It included the following steps: 1. To select the necessary experimental setup; 2. To select the necessary equipment and additional control devices; 3. To select diagnostic modes and diagnostic parameters. We opted for the VAZ-2112 ICE as the most common in the Russian Federation. The experimental setup and additional devices are shown in Fig. 10 and Fig. 11.
Besides, we selected the following main equipment: DBD-4 gasoline engine loader and INFRAKARM2.01 4-component gas analyser. Additional control devices were needed to control the secondary parameters of the ICE systems [17,18]. The additional control devices include a MT-10 motor tester and a PC.  In the exhaust system, exhaust gas intake points are shown in individual exhaust manifolds. Holes were drilled at these points and nuts with adapters were installed to connect the gas analyser probe to them. Notably, this connection is made through a cooling coil to cool the exhaust gas before the gas analyser [33,34,35].
A λ -probe is shown further along the exhaust system. The catalytic converter and silencer come next. Special washers are installed at the end of the silencer to generate artificial resistance. The wires of the DBD-4 device are connected to the gap of the electromagnetic nozzles. DBD-4 is also connected to the control unit (ECU) of the ICE.

THE RESULTS OF THE EXPERIMENTAL STUDIES
Further tests were focused on comparing different exhaust gas intake options. To this end, we used an experimental setup based on the VAZ-2112 ICE (Fig.  10). The concentrations of СО, СН, СО 2 , and О 2 were measured in three different ways: 1) the operation of the 1st cylinder and the exhaust gas intake in the common exhaust pipe; 2) the operation of all the four cylinders and the exhaust gas intake in the common exhaust pipe; 3) the operation of the 1st cylinder and the exhaust gas intake in the exhaust manifold immediately after the exhaust gases leave the cylinder. The measurements were carried out with a resolution of 500 rpm, starting at 1000 rpm. As a result, we obtained the dependence of the concentration of CO (%) in the exhaust gases on the ICE crankshaft speed n (rpm) (Fig. 11). The load level when one cylinder is on corresponds to 0.25 of the rated power at nominal crankshaft speeds. All the intermediate load values were determined using a tester motor. The parameter -ICE power during testing was displayed in its standard parameters.
As we can see from Fig. 11, during the operation of all the four cylinders and the exhaust gas intake in the common exhaust pipe, the concentration of СО in the exhaust gases reaches the highest values from 9.4 to 10.2%. The maximum is manifested at a point corresponding to 4,000 rpm. During the operation of the 1st cylinder and the exhaust gas intake in the exhaust manifold, immediately after the exhaust gases leave the cylinder, the concentration of CO reaches its maximum value of 4% at 1000 rpm. With an increase in the speed, the concentration of CO decreases, reaching 1% at 5000 rpm. During the operation of the 1st cylinder and the exhaust gas intake in the common exhaust pipe, the concentration of CO reaches its minimum value of 1.98% at 1000 rpm. Further, the concentration of CO is kept at a level of no more than 1% with an increase in the ICE crankshaft speed. However, this low CO value is explained by the mixing of free air entering the outlet from neighbouring idle cylinders. Based on the experimental data, we obtained the dependence of the concentration of CH (ppm) in the exhaust gases on the ICE crankshaft speed (Fig. 12).
An analysis in Fig. 12 shows that CH reaches significantly higher values during the operation of all the four cylinders and the exhaust gas intake in the common exhaust pipe. So at 1,000 rpm, the concentration of CH reaches a maximum of 715 ppm. Further, with an increase in the ICE crankshaft speed, CH decreases and amounts to 400 ppm at 5000 rpm. During the operation of the 1st cylinder and the exhaust gas intake in the common exhaust pipe and the operation of the 1st cylinder and the exhaust gas intake in the exhaust manifold immediately after the exhaust gases leave the cylinder, we observe almost identical results varying within the experimental error.
Based on the results of the experiment, we also built the dependence of the concentration of СО 2 (%) in the exhaust gases on the ICE crankshaft speed n (rpm) (Fig. 13). An analysis of the data in Fig. 13 shows that the highest value of the concentration of СО 2 is observed during the operation of the 1st cylinder and the exhaust gas intake in the exhaust manifold immediately after the exhaust gases leave the cylinder. So, at the ICE crankshaft speed of 1,000 rpm, the concentration of СО 2 is 10.7%. Then, the concentration of СО 2 grows and reaches a maximum of 14% at the ICE crankshaft speed of 4,500 rpm. During the operation of all the four cylinders and the exhaust gas intake, a slightly lower СО 2 value is observed in the common exhaust pipe. This is explained by free oxygen coming from the neighbouring cylinders in the absence of combustion in them. The lowest СО 2 value is observed during the operation of the 1st cylinder and the exhaust gas intake in the common exhaust pipe. Free oxygen from the neighbouring cylinders also has a significant effect in the absence of combustion in them. Based on the results of the experiment, we built the dependence of the concentration of О 2 (%) in the exhaust gases on the ICE crankshaft speed n (rpm) (Fig. 14). Analysing Fig. 14, we can see that the concentration of О 2 reaches its maximum values during the operation of the 1st cylinder and the exhaust gas intake in the common exhaust pipe. We can see that the concentration of О 2 is on average 16.2%, whereas the concentration of О 2 is below 2% during the operation of the 1st cylinder and the exhaust gas intake in the exhaust manifold immediately after the exhaust gases leave the cylinder and the operation of all the four cylinders and the exhaust gas intake in the common exhaust pipe. This is also explained by the impact of free oxygen from the neighbouring cylinders on the control result.

OPERATIONAL TESTS
As a result of the operational tests, we obtained comparative nomograms for determining the technical condition of the electromagnetic nozzles, the catalytic converter and the spark plugs of VAZ cars according to the results of analysing the exhaust gas composition. The maximum value of the upward or downward change in the registered parameter was taken for 100%. Zero value is taken at the reference condition of the elements specified by the manufacturer. It is convenient to consider the relative values of the parameters in %. The following parameters were controlled at the output: CO content, СО 2 content, CH content, О 2 content, and the ICE crankshaft speed n. These parameters are measured by different values, but it is very convenient to compare them in % (Fig. 15).
We can see from Fig. 15 that the parameters СН and О 2 take the maximum change. The concentration of CH increases significantly with an increase in the capacity of the electromagnetic nozzle. The concentration of О 2 , on the contrary, decreases significantly with an increase in the capacity of the electromagnetic nozzle. The ICE crankshaft speed increases almost linearly with an increase in the capacity of the electromagnetic nozzle. The parameters СО and СО 2 begin to increase significantly with a change in F from 100 to 106%, with an entry of the rich air-fuel mixture.
Let us consider the complex dependence of the relative values of the controlled parameters of the СО content, СО 2 content, СН content, О 2 content, and the ICE crankshaft speed n on the spark plug gap Z (mm) (for VAZ ICE) (Fig. 16). An analysis of Fig. 16 shows that the parameters CH and the ICE crankshaft speed reach the maximum changes. At the same time, the parameters CH and n sharply increase to Z=0.8 mm with an increase in the spark plug gap.
The values of CO and О 2 grow with an increase in Z, but at Z=0.8 mm, the growth slows down.
We should say that varying the spark plug gap did not show the expected result. This particularly concerns the placement of gaps less than 0.6 mm. We observed a tendency that with an increase in the temperature of the exhaust manifold, the concentration of CH decreased markedly. The values of the concentration of CH presented in Fig. 16 also varied from 0 to 30-40 ppm. That is, these changes were too close to the error margin of the gas analyzer and the imposition of other external factors.
Let us consider the complex dependence of the relative values of the controlled parameters of the СО content, СО 2 content, СН content, О 2 content, and the ICE crankshaft speed n on the equivalent resistance of the catalytic converter R (mm) (for VAZ ICE) (Fig. 17). An analysis of Fig. 17 shows that the parameters CO and n change to the maximum extent. The concentration of CO increases with an increase in the equivalent resistance of the catalytic converter. At the same time, the value of n, on the contrary, drops sharply with an increase in the equivalent resistance of the catalytic converter.
The parameters СН, СО 2 and О 2 will not change so noticeably, but they have obvious maximums and minimums within R=22 mm.