Possibility of reduction of the environmental impact of a diesel engine by means of changing the compression ratio

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Report. The article is devoted to solving environmental problems arising from the operation of mobile energy vehicles with diesel engines in the agro-industrial sector and installed on cars, tractors, combines. Contrary to all forecasts, the use of environmentally friendly engines capable of competing with piston engines is limited in agricultural production, therefore, solving the problem of reducing harmful emissions from exhaust gases of diesel engines used in agriculture is very important and relevant.

The research is aimed at solving one of the key tasks of our time – reducing the anthropogenic load from harmful emissions of diesel engines on the environment by changing the compression ratio. As a result of the test, it was found that an increase in the compression ratio from 13.5 to 15.5 leads to a decrease in emissions from exhaust gases of solid particles (PM), hydrocarbons (C_xH_y) and carbon monoxide (CO), however, over the entire load characteristic from Pe =0 to Pe=1.24 MPa at 1900 min^-1 emissions of nitrogen oxides (NO_x) increases. Emissions of particulate matter from exhaust gases are reduced from 0.122 to 0.063. When the compression ratio changes from 13.5 to 15.5, the estimated values change: for nitrogen oxides – by 1.88 times; for carbon monoxide – by 1.22 times; for hydrocarbons – by 1.35 times; for solid particles – by 1.15 times. The evaluation results showed that the values of the anthropogenic load were Htn = 78.31 ut/g with serial configuration at = 13.5 and Htn = 90.4 ut/g at = 14.5. This indicates a decrease of 1.15 times with a decrease to 13.5. In order to obtain the best results in reducing the anthropogenic load on the environment, it is recommended to use complex methods, for example, simultaneous changes in the degree of compression and catalytic neutralization.

Justification. The annual growth in the number of mobile cars and power plants with diesel engines is many times faster than the rate of improvement of their environmental qualities [1]. Contrary to all forecasts, currently the use of environmentally friendly engines capable of competing with piston engines is limited in agricultural production. At the same time, agricultural production itself is a source of air pollution, in this regard, solving the problem of reducing harmful emissions from exhaust gases of internal combustion engines used in agriculture is one of the effective methods of reducing the anthropogenic burden on the environment [2, 3, 4].

Global standards for harmful emissions from exhaust gases of internal combustion engines are constantly becoming tougher. This indicates that it is becoming increasingly difficult to implement them. In this regard, it becomes relevant to apply new technical solutions aimed at reducing harmful emissions from exhaust gases and reducing the anthropogenic burden on the environment [1, 2, 3, 4, 12, 13]. The possibilities of reducing the toxicity of diesel exhaust gases by changing the compression ratio have been used by most companies and noted by a number of researchers [1, 4, 5, 6, 7, 8, 9, 10, 11, 12]. Purpose. Reducing the anthropogenic impact on the environment from harmful emissions from diesel engines of mobile vehicles by changing the compression ratio.

Methods. This paper specifically describes the experimental data obtained during bench tests of the 4ChN 15/18 diesel engine (BM-4). The stands were equipped according to GOST 14846-2020. The diesels were assembled according to the general specifications according to GOST 10150-2014. The test methods were in accordance with GOST 10448-2014. In the experiment, diesel fuel according to GOST 305-2013, grade L-0.2-40, and engine oil according to GOST 6360-2020, grade MT-16P were used. During bench tests, the nominal (effective) power of the 4ChN 15/18 diesel (BM-4) was Ne=250 kW, the crankshaft speed was n=1900 min^-1, the specific effective fuel consumption was ge=224 g/kWh, the oil burn was Dm=0.29%. Microclimatic conditions in the box: ambient temperature T₀=290...292 K, atmospheric pressure P₀ =0.100...0.101 MPa, relative humidity j₀ =80...83 % [13].

The study of emissions of harmful substances (CO, C_xH_y , NO_x) was carried out on an AUG gas analyzer-4-0-5-01 according to GOST 31967-2012. Measurement of smokiness (based on emissions of particulate matter - PM) according to GOST 24028-2013, on a BOSCH smoke meter. All measurements were made at steady-state modes (according to the VCC - in terms of power, RPM and hourly fuel consumption). According to the test program, diesel exhaust gases were selected, their composition and dispersion of solid particles were analyzed at compression ratios = 13.5 ...14.5 ...15.5 according to the load characteristic at 1900 min^-1. All tests at various values were carried out by the diesel engine manufacturer.

Results. As a result of the test, it was found that over the entire load characteristic from Pe=0 to Pe= 1.24 MPa at 1900 min^-1 , emissions of nitrogen oxides (NO_x) increase, and with an increase in the compression ratio from 13.5 to 15.5, emissions of particulate matter (PM) decrease (Fig. 1). Emissions of particulate matter (PM) with exhaust gases is reduced significantly from 0.122 to 0.063 (at Pe = 1.24 MPa and n= 1900 min^-1) or almost twice. This result can be explained by the fact that with an increase in the compression ratio and constant cyclic supply, the temperature in the cylinder becomes higher, the position of Tmax shifts to TDC, while the probability of nitrogen oxidation increases. With an increase in the compression ratio from 13.5 to 15.5, emissions of hydrocarbons (C_xH_y) and carbon monoxide (CO) also decrease (Fig.2). The change in emissions with an increase in the compression ratio is explained by the fact that the completeness of combustion increases, the ignition delay period becomes shorter and the time allotted for fuel combustion increases in the cycle.

The growth leads to a higher heating of the charge near the cold walls of the cylinder liner, which increases the completeness of combustion. In accordance with the tasks set, the dispersion of PM was studied with a change in the compression ratio in the cylinders (Fig. 3).

Figure 1. The effect of the compression ratio on the levels of harmful NO_x and PM emissions of diesel 4ChN15/18 according to the load characteristic at 1900 min^-1

Figure 2. The effect of the compression ratio on the levels of harmful emissions of C_xH_y and CO of diesel 4CHN15/18 according to the load characteristic at 1900 min^-1

Figure 3. The effect of the compression ratio on the dispersion of PM diesel 4ChN15/18

 

 

A change in the compression ratio from 13.5 to 15.5 leads to an increase in the average diameter of solid particles in the exhaust gases of diesel 4ChN15/18.

 

 

Table 1

The effect of the compression ratio on the values of the estimated indicators of harmful diesel emissions 4ChN15/18

 

Estimated indicator	Values of estimated indicators, g / (kW • h)								The degree of excess of permissible estimated emissions according to standards:Stage 2/3a/3b/4/Russia by =14,5
	acceptable standards					valid compression ratios,
	Stage 2	Stage 3a	Stage 3b	Stage 4	For Russia since 2021	13.5	14.5	15.5
q ei NOx	6.00	4.0	2.00	0.40	6.00	9.75	11.30	18.35	1.88/2.83/5.65/28.3/1.88
q ei СO	3.50	3.50	3.50	3.50	3.50	11.60	10.50	9.50	3/3/3/3/3
q ei СxНy	1.00	1.00	0.19	0.19	0.40	1.82	1.70	1.34	1.7/1.7/8.95/ 8.95/4.25
q ei PM	0.20	0.20	0.20	0.02	0.10	0.15	0.14	0.13	0.7/0.7/0.7/7/ 1.4

Analysis of the data in Table 1 showed that when the compression ratio changes from 13.5 to 15.5, the estimated values change significantly: for nitrogen oxides – by 1.88 times; for carbon monoxide – by 1.22 times; for hydrocarbons – by 1.35 times; for solid particles – by 1.15 times. The anthropogenic load on the environment was calculated according to the methodology given in [2, 3] and amounted to Htn=78.31 ut/g with serial configuration at =13.5 and Htn =90.4 ut/g at =14.5, which indicated its decrease by 1.15 times when reduced to 13.5.   

Conclusion. 

1. The compression ratio can be taken as an adjustable parameter when solving problems of reducing emissions of nitrogen oxides from exhaust gases.
2. The compression ratio has little effect on changes in PM and CO emissions.
3. When the compression ratio is reduced from 14.5 to 13.5, the anthropogenic load on the environment is reduced by 1.15 times.
4. Reducing harmful emissions from diesel exhaust gases to the required standards of the Stage and the Russian Federation can be achieved by using integrated methods, for example, by simultaneously changing the compression ratio and installing a catalytic converter or a particulate filter.

About the authors

Alla A. Melbert

Altay State Technical University named after I.I. Polzunov

Author for correspondence.
Email: aamelbert@mail.ru
ORCID iD: 0000-0002-3973-8315
SPIN-code: 5949-5831
Scopus Author ID: 57194693283

Dr. Sci. (Engineering), Professor of the Life Safety Department

Russian Federation, 46 Lenina ave, Barnaul, 656038

Ekaterina A. Mashenskaya

Altay State Technical University named after I.I. Polzunov

Email: suzuki468@mail.ru
ORCID iD: 0000-0003-3122-0412
SPIN-code: 8323-5725

Applicant, Life Safety Department

Russian Federation, 46 Lenina ave, Barnaul, 656038

Aleksander Yu. Kalin

Altay State Technical University named after I.I. Polzunov

Email: aleksandr.aleksandr.74@bk.ru
ORCID iD: 0009-0005-2028-798X
SPIN-code: 6446-5236

Cand. Sci. (Agriculture), Associate Professor of the Life Safety Department

Russian Federation, 46 Lenina ave, Barnaul, 656038

Ilya S. Litvinenko

Altay State Technical University named after I.I. Polzunov

Email: litvinenko.i.s@mail.ru
ORCID iD: 0009-0001-1213-4503
SPIN-code: 3516-0704

Lecturer of the of the Life Safety Department

Russian Federation, 46 Lenina ave, Barnaul, 656038

References

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