OPTIMIZATION OF WORKING PROCESSES OF GAS ENGINES

SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 11 OPTIMIZATION OF WORKING PROCESSES OF GAS ENGINES Z.E. Musabekov1, R.R. Tillahodjaev2, F.M. Raxmatova3 Tashkent State Technical University1,2,3 https://doi.org/10.5281/zenodo.17389075 Abstract. The article presents a methodology for formulating requirements for high power indicators imposed on a gas engine and its systems during design to ensure the best fuel efficiency based on the development of scientific and experimentally substantiated methods for increasing the energy efficiency of gas engines. The main provisions of the engine theory are based on thermodynamics, the theory of experiment planning using factor models, correlation theory and methods. Of interest is such a method for increasing fuel efficiency as the use of the Miller cycle, which is used in gasoline engines and stationary gas engines. Keywords: gas engine, thermodynamics, Miller cycle, efficiency, direct gas injection, fuelair mixture, torque. Introduction. Of the two methods of performing the Miller cycle (with early "E-Miller" and "L-Miller" late closure of the valve), the early valve closure method was chosen as the main one. This is due to the fact that the late closing of the valve implies that the input will perform gas spraying directly after closing the valve. Without dwelling on the advantages and disadvantages of this method of mixture formation, we note that we have adopted the formation of an outer mixture with a stepwise gas spray distributed to the inlet channel in the area of the inlet valves. With the method of forming an external mixture, late closure of the inlet valve causes the fuel-air mixture to be re-introduced into the intake system. Thus, the introduction of a new profile should ensure that the valve closes early so that the actual compression ratio, as determined by the position of the piston at the time of insertion valve closing, will be in the range of 12-14 units. But for the late closing of the input valve, it is necessary to make a distribution shaft in which it has a profile. When implementing a shortened input tactile workflow, the positive thing is that we will actually have an extended expansion engine. Therefore, one of the optimization issues is to choose the ratio of the actual degree of expansion to the actual level of compression, which is characterized by the Atkinson coefficient (A). Studies show that the best values of indicator effectiveness are achieved with values of the At coefficient in the range of 1.2 – 1.5. (Figure 1). The actual compression ratio in this case will be in the range of 14 - 11 units. On the one hand, the compression beat is determined by the conditions that limit the maximum pressure at the end, and the conditions of the chamber's clock-free operation with a narrower profile of the shortened input beat. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 12 Figure 1. The efficiency of the indicator (1-curve) and the real compression ratio Ɛd (2curve) with respect to the value of the horse coefficient. In this regard, further optimization steps have been made in relation to a particular engine. Table 1. Technical data of main diesel engine. Table 1. Selected configuration name Values 1. Engine Type ISUZU 4HK1 fourstroke four-cylinder diesel 2. Cylinder diameter, mm 115 3. Piston road, mm 110 4. Engine size, L 4,5 5. Geometric compression ratio 19 6. Rated power kWh (hors. p) in accordance with UNECE Regulation No. 85, net 140 (190) 7. Maximum B/M, N/m, (rpm) in accordance with UNECE Regulation No. 85 510 (1600 months/m) 8. Rotational frequency at rated power, min-1 3200±25 km 9. Gas distribution phase: inlet valve - Opening top dead center to 21.4 - Close bottom dead center then 36.7 Gas distribution phase: Exhaust valve - Opening bottom dead center to 53.7 - Close top dead center then 21.7 Research Methods and the Received Results It is assumed that the maximum power of a gas engine should be 180 kW, work in the stoichiometric composition of the fuel-air mixture and the specific effective consumption should not exceed 230g/kWh. The maximum torque should be at least 900 Nm at a speed of 1400-1800 min-1. The actual compression ratio for this engine was calculated as the dependence of the engine crankshaft tilting angle (ECTA) at which the input valve and the corresponding piston track close (Figure 2). ECTA angles achieved at ɛd = 11–14 lie in the range of 95–120 ECTA angles (calculated from top dead center). In the future profiling of the first of the distribution shaft, they will be guided by these values. Calculations show that a smaller value of the input valve closing angle (ECTA from top dead center) reduces Ɛd and reduces the risk of detonation, but leads to a significant decrease in the actual fill factor, and as a result, it is necessary to increase the supercharging level in order to achieve the values set in terms of power indicators. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 13 Figure 2. The true compression ratio is the dependence of Ɛd on the ECTA angle of the engine, in which the input valve and the corresponding piston path Sn are closed. 1 is the actual compression ratio, 2 is the piston path. In this regard, it is of interest to consider the relationship between the values of the air input (pressure at the end of the injection stroke Pa) and the pressure pc values at the end of the compression stroke at different values of the At coefficient, but Pe at the same values of the average effective cycle pressure. The pressure at the end of the compression beat is determined by a certain relationship: pc=pa Ɛdn1 (1) where: Ɛd is the actual compression ratio. N1 is the compression polytropic index. The pressure at the end of the injection bar is determined on the condition that the required maximum mass airflow is achieved on the basis of the requirement to maintain the fixed value of pa. The required maximum air consumption of the engine will be determined here: Gв = 0.008338al0gereVhn (2) where: a – Y/H mixture composition; L0 is theoretically the required amount of air, kg / kg; ge - predicted effective fuel consumption, kg/kWh; re-averaging effective cycle pressure, MPa; Vn is the geometric working capacity of the engine l; n is velocity, min-1. We envisage the determination of airflow by cyclical supply. Gв =30Ghtsni (3) where: Ght cyclical supply, kg/cycle; i - the number of cylinders. Cyclical air supply: Ght =Vhd ρв /(1+1/α l0) ηv (4) where: ρ is the density of the air charge in the cylinder. ηv is the fill coefficient. SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 14 Vhd is the actual working volume of the cylinder. The density of the air charge to ensure a given mass airflow and average effective pressure: ρv = Gv (1+1/α l0) / (30 Vhd nηv) (5) Then the air pressure at the inlet is determined by a certain dependence: P = ρv Rnh (t1+273) / ρнhTнh (6) where: Pressure, density, and air temperature under normal conditions, Rnh, ρnh, and Tnh; ρv is the density of the air charge in the cylinder according to the formula (2.5); t1The temperature of the air introduced after the introduction (in Celsius) Figure 3 shows the dependence of pa and pc on the value of the At coefficient. Calculations were performed at the same values of the rotation frequency of pe = 16 bar and 1600 min-1. It should be noted that as soon as the Horse coefficient rises by values of 1.3 - 1.4, at the end of the compression beat, the pressure decreases, and then the pressure increases. From the point of view of efficiency, the pressure at the end of the compression stroke differs in the range of the optimal values of At no more than 2-2.5%. The complex nature of curve 1 is explained by the change in the effective efficiency of the engine in accordance with curve 1 in Figure 2.1 with an increase in the horse coefficient. Accordingly, the specific effective fuel consumption will increase. The filling coefficient decreases as well. And in order to maintain a constant average effective pressure, it is necessary to increase the velocity of the air mass flow, its density, and therefore the inlet pressure. Figure 3. dependence of pa and pc on the value of the coefficient At. 1 is the pressure at the end of the compression charge at ηevar; and ηv; - var. 2 is the pressure at the end of the input beat in ηevar; and ηv; - var. 3 is the pressure at the end of the compression beat in ηeconst; and ηv; - const. 4 - pressure at the end of the insertion beat in ηeconst; and ηv; - const. By comparison, Figure 3 shows how the pressure can change at the end of the compression beat if ηe and ηv are ηv; it has remained constant (curves 3 and 4). But this is only an approximate assumption, which is impossible in practice. Conclusion This means that if the average effective pressure is constant, from the point of view of detonation, it does not make sense to shorten the input stroke as much as possible and reduce the actual compression ratio. You can limit yourself to its minimum cost, which will ensure high efficiency and minimum value. Thus, the values of the at coefficient, where the best fuel efficiency SCIENCE AND INNOVATION INTERNATIONAL SCIENTIFIC JOURNAL VOLUME 4 ISSUE 10 OCTOBER 2025 ISSN: 2181-3337 | SCIENTISTS.UZ 15 indicators and minimum pressure values are achieved at the end of the compression stroke, lie in the same range - 1,2... 1.6. REFERENCES 1. Zakirjon Musabekov, Rustam Tillahodjaev, Abdulla Mirzayev, Avaz Yangibayev, Hilola Uralova. "Increasing energy efficiency as a result of the influence on the operation of a Sano automobile engine with the adding of hydrogen as an additive to primary fuel doi":10.1088/1755-1315/1284/1/012038 2. Rustam Tillahodjaev, Abdulla Mirzayev "Improving the quality of fuel with the use of a zeolite filter in the supply system of engines running on compressed and liquefied gas". Conference: Problems and prospects of innovative technique and technology in agri-food chain. Proceedings scientific papers of the III-International conference. -Tashkent, 2023.At: Tashkent 3. Rustam Tillahodjaev, Abdulla Mirzayev "The influence of the correct selection of engine oil on the economic and environmental performance of internal combustion engines with gasballoon equipment". Academic Leadership 2:11-15 DOI: 10.5281/zenodo.6563097 June 2022 4. Rustam Tillahodjaev "Natural compressed and liquefied gases as an alternative to improving the environmental and economic performance of cars". Conference: Problems and prospects of innovative technique and technology in agri-food chain. Proceedings scientific papers of the II-International conference. -Tashkent, 2022.At: Tashkent 5. Tulaev BR, Musabekov ZE, Daminov OO "Application of supercharged to internal combustion engines and increase efficiency in achieving high environmental standards." AIP Conference Proceedings 2432, 030012 (2022). DOI: 10.1063/5.0090304 6. Rustam Tillakhodjaev "Improving the environmental properties and economic performance of gas engines". Conference: Actual problems and techniques of teaching engineering disciplines At: November 2022 Termez 7. Musabekov ZE, Khakimov JO, Ergashev B. Differential equations for calculating gas exchange in an internal combustion engine. E3S Web of Conferences 264, 01003 (2021). The International Scientific Conference "Construction Mechanics, Hydraulics and Water Resources Engineering (CONMECHYDRO 2021)". 1-3 April 2021. Published online: 02 June 2021. DOI: 10.1051/e3sconf/202126401003 8. Musabekov Z., Khakimov J., Yangiboev A., Tairova N., Usmonov J., Petruchenko A. Flow stabilization and pulsation in external channels in fuel engines. (2023) IOP Conference Series: Earth and Environmental Science, 1142 (1), article no. 012022. DOI: 10.1088/17551315/1142/1/012022