Low Engine Speed Research Articles

Experimental verification of changes in the control map of a diesel engine operation due to fuel consumption

The paper describes an experiment related to the introduction of changes in the control software of a supercharged diesel engine in order to reduce fuel consumption, as a measure of useful efficiency. The map shaping the torque in the range of low and medium engine speeds was modified. The fuel dose for a specific engine speed at maximum engine load was changed and the boost pressure was increased, without exceeding the permissible values. A vehicle from the age group of 16 years - typical for the automotive market in Poland, was selected for the tests. It meets the EURO 5 standard. The experiment was carried out on a chassis dynamometer and in road traffic conditions. The average fuel consumption was obtained lower by 0.4 dm3 per 100 km than the factory assumed.

Science and Technology of Supercapacitor and its Applications

Super-capacitors (SCs) are significant because of their unique characteristics, which include long cycle life, high strength, and environmental friendliness. SCs use electrode substances with high specific surface area and thinner dielectrics. Referring to the energy storage mechanism, all kinds of SCs were reviewed in this review paper; a quick synopsis of the materials and technology used for SCs is provided. Materials such as conducting polymers, carbon materials, metal oxides, and their composites are the main focus. The performance of the composites was evaluated using metrics such as energy, cycle performance, power capacitance, and rate capability, which also provides information on the electrolyte materials. To precisely appraise the state of Charge (SoC) in the super SCs cell module, its identical model o is used. It is expected that this model will accurately capture the features of the cell module, specifically its standing-related self-discharge behavior, and the outcomes of parameter identification directly impact its accuracy. Engine downsizing is a result of the requirement to increase fuel efficiency and lower CO2 and other hazardous pollutant emissions from internal combustion engine cars. However, smaller turbocharged engines have a relatively poor torque capability at low engine speeds. To solve this issue, an electrical torque boost based on SCs may be used to help recover energy during regenerative braking as well as during acceleration and gear changes.

Performance study of an innovative dual injection mode injector for marine low-speed dual-fuel engine

Marine low-speed dual-fuel engines typically have two sets of fuel injection system, main-injection and micro-injection. In order to make the fuel injection system of marine low-speed dual-fuel engine compact in structure and flexible in injection control, an innovative dual injection mode injector (DIMI) which can achieve both the functions of main-injection and micro-injection was proposed. The switching between main-injection and micro-injection mode of the injector is achieved through the collaborative control of dual solenoid valves. Based on the constructed AMESim model, the injection quantity characteristic and hydraulic efficiency of the DIMI were investigated under different working conditions and injection modes. The results show that, when the DIMI in main-injection mode achieves injection quantity characteristic similar to those of a traditional electronically controlled injector (TECI), the electromagnetic forces of solenoid valves of the DIMI are less required to 80% of that of the TECI, and the fuel return quantity and hydraulic efficiency of the DIMI are comparable to those of the TECI under the same working conditions. By changing the minimum limit height of the needle of the DIMI under micro-injection mode, different ranges of micro-injection quantity could be designed according to the requirements of the engine, and the control accuracy of injection pulse width (IPW) on micro-injection quantity is higher than on main-injection quantity. Both the hydraulic efficiency of the DIMI under main-injection and micro-injection mode increase with the rail pressure and IPW in the small IPW range, then gradually tend to be saturated with the increase of IPW. As the minimum limit height of the needle increases, the injection quantity and hydraulic efficiency of the DIMI under micro-injection mode increases overall, however, the saturation values of the hydraulic efficiency in micro-injection mode under different needle minimum limit heights are still smaller than those in main-injection mode.

Turbocharged DISI engine low-load performance improvement investigation through ozone seeding with residual gases and excess air charge dilution

The automotive industry has long prioritized the search for more efficient engines, driven by environmental concerns, fuel prices, and consumer demand for fuel-efficient vehicles. Various technologies and strategies are explored to enhance performance while reducing fuel consumption and emissions. Despite potential combustion stability issues, techniques like using lean mixtures or retaining exhaust gases are commonly employed. Ozone seeding has emerged as a combustion enhancer for internal combustion engines, particularly effective under lean mixtures or high residual gas levels, aiming to stabilize de-throttling conditions, minimize pumping losses, and enhance engine efficiency by enhancing the reactivity of the mixture through the release of radicals that facilitate fuel oxidation. This study investigates the impact of ozone addition on engine performance, emissions, and fuel consumption using a turbocharged SI vehicular engine on a dynamometer bench under different loads. Ozone was introduced to the engine intake using an ozone generator with compressed air, considering two mixture dilution strategies: fresh air and residual gases. Results show that ozone application, with Brazilian Gasoline Type C, induces autoignition of the end-gas under specific low-load, low-engine speed conditions. Up to 1000 ppm, ozone has no discernible impact on DISI engine operation under excess air dilution, maintaining performance equivalent to the baseline. For specific operating conditions with 3 and 4 bar BMEP, where ozone stabilizes combustion with higher residual gas fraction (RGF) percentages, there is a notable reduction in specific fuel consumption, suggesting a potential 1%–1.5% increase in brake efficiency. However, ozone seeding with high RGF percentages leads to a slight increase in CO emissions, elevated NOX emissions, and a tendency to reduce THC emissions up to a certain RGF limit.

Effect of ignition timing on combustion characteristics and emissions of an X-type rotary engine with the high efficiency hybrid cycle

X-type rotary engines (XREs), using the high efficiency hybrid cycle, possess advantages of simple structure, high power-to-weight ratio, and high theoretical efficiency, making XREs as potential power sources in hybrid vehicles and small unmanned aerial vehicles. Typically, ignition timing has a promising potential to improve the combustion performance of spark ignition engines. In this work, the effects of ignition timing on flame propagation, combustion characteristics, and pollutants formation were studied adopting a three-dimensional simulation method. The results showed that at different engine speeds, significantly different flow forms and flow velocities in the larger chamber recess of the XRE were formed, resulting in large differences in flame propagation velocities at leading side and trailing side of the combustion chamber. Advancing ignition timing increased the flame propagation velocity at the given engine speed. Ignition timing had a more significant effect on peak pressure at medium-high speeds compared to low engine speeds. At 3000 RPM and 5000 RPM, the peak pressure was increased significantly with advancing ignition timing, but when ignition timing was advanced to -30 °CA, the increment in the in-housing pressure was minimal. As ignition timing was retarded, the ignition delay was slowly reduced. The effect of ignition timing on ignition delay was more significant for low speeds than for medium-high speeds. However, the influence of ignition timing on combustion duration showed the opposite trend. Delayed ignition showed a slight increase in indicated thermal efficiency and indicated mean effective pressure at low speeds, while the opposite was true at medium-high speeds. Nevertheless, the effect of ignition timing and engine speed on indicated specific fuel consumption is opposite to the trend of the above laws. With the increase of ignition timing, the NOx mass fraction first increased and then decreased at low speeds, with the maximum occurred at -30 °CA, but the NOx mass fraction continued to increase at high speeds. Soot and CO productions were slightly affected by ignition timing. To sum up, this XRE, setting the ignition timing of -30 °CA, achieved better flame propagation and engine performance at the price of a smaller increment of NOx emissions.

Design, optimisation and evaluation of the S-CO2 Brayton cycle for marine low-speed engine flue gas

Five configurations of the S-CO2 Brayton cycle (SCBC) were constructed for flue gas waste heat recovery (WHR) of the marine low-speed engine HHM-6EX340EF on the EBSILON platform using the bench test data to save energy, reduce emissions and the efficient operation of ocean-going vessels. Experimental data from Sandia National Laboratories (SNL) was utilised to validate the accuracy of the model and the effect of Brayton cycle parameters on flue gas WHR for different configurations was analysed. The parameters of the SCRBC (S-CO2 recompression Brayton cycle) were optimised by combining the Neural Network Fitting (NNF) model, Multi-objective optimisation algorithms, and multi-criteria decision-making methods. Finally, the thermodynamic analysis of the low-speed engine was comprehensively evaluated by comparing five configurations of SCSBC (S-CO2 simple Brayton cycle), SCCBC (S-CO2 recuperative Brayton cycle), SCHBC (S-CO2 reheating Brayton cycle), SCIBC (S-CO2 intercooling Brayton cycle), and SCRBC. The optimised SCIBC configuration had the highest net recuperated work of 195.76 kW and the highest Brayton cycle efficiency of 20.13 %. The engine efficiency was improved by 0.82 %, 1.45 %, 1.78 %, 1.86 % and 1.68 %, the BSFC was decreased by 3.20 g/kW·h, 5.56 g/kW·h, 6.82 g/kW·h, 7.04 g/kW·h, and 6.43 g/kW·h, and the output power increased by 86.90 kW, 153.33 kW, 195.76 kW, 189.36 kW, and 178.14 kW, respectively. The maximum exergy loss of the cooler was 162.67 kW with an exergy loss efficiency of 14.54 % in the SCSBC configuration. Optimising the flue gas heat exchanger and cooler will further enhance the efficiency and reduce emissions. Research on the parameter and configuration optimisation of the SCBC for marine low-speed diesel engines can be extended to other low-speed engines.

Conversion of a small size passenger car to hydrogen fueling: simulation of full load performance

Abstract Hydrogen offers a valid choice when considering zero emissions transport. This alternative fuel is well suited for spark ignition (SI) engines and it can be implemented with relatively minor changes in terms of added components. Initial evaluations of feasibility with respect to available space for the fuel tank revealed that it is possible to convert a small size passenger car to hydrogen fueling and maintain a range comparable to the fully electric alternative. Peak power assessment showed that additional boosting was required compared to gasoline operation, close to the limit of compressor surge. As a result, the present study extended the engine speed range so as to evaluate full load performance levels that can be obtained when using hydrogen. 0D/1D simulation was applied for simulating power unit output as well as related control parameters. A dedicated laminar flame speed sub-model was implemented for including fuel chemistry effects. Predicted combustion phasing showed the required changes in ignition timing when switching fuels and revealed that the engine could be operated close to stoichiometry when using hydrogen. A reduction of torque was calculated at low engine speed, even if peak power ratings were practically the same as with gasoline fueling.

Flow and heat transfer in multi-cavity pistons with oscillating cooling

Under high temperature and pressure conditions, pistons play a crucial role in managing thermal stress within combustion chambers. To analyze of the heat transfer characteristics of piston cooling systems in low-speed engines, this study developed and validated an oscillating cooling model featuring a composite piston with multiple cooling cavities. Using numerical simulation methods combined with dynamic mesh technology, the model replicates the long-stroke behavior of actual diesel engines and is validated against preliminary experimental data. The results demonstrates that during reciprocating motion, oil flowing through the telescopic sleeve interacts with gas from breather holes, forming a gas–liquid two-phase flow that significantly alters the liquid film coverage ratio (LFC) on wall surfaces, influencing heat transfer efficiency. As the filling rate increases from 28 % to 71 %, the average liquid film coverage (ALFC) rises by 0.27, and LFC fluctuation frequency decreases, with amplitude increasing by 0.08. Notably, the average Nusselt number (Nuavg) shows significant increases for top surface of inner cavity (TSIC) and side surface of inner cavity (SSIC) between filling rates of 52 % and 64 %, while the maximum increase for top surface of outer cavity (TSOC) and side surface of outer cavity (SSOC) occurs between 37 % and 52 %. Temperature drops at points A and B in the filling rate range of 28 % to 52 % were 1.37 K (4.09 K), which is notably higher than the 0.35 K (0.86 K) drop in the 52 % to 71 % range. Analyzing these changes indicates that the optimal filling rate for enhanced heat transfer performance is approximately 52 %. Furthermore, as engine speed increases from 135.2 to 202.8 rpm, the piston head filling rate decreases from 0.60 to 0.46, reducing both the contact area and the surface heat transfer coefficient. This study provides profound insights of the multiple cooling cavities under reciprocating motion and presents new strategies for optimizing piston cooling systems designed for low-speed engines.

Experimental Study of the Effect of Roller Shape Variations on the CVT System using Petrol-Pyrolytic Fuels toward the Power Characteristics of Automatic Motorcycles

There are two types of two-wheeled vehicles when viewed from the transmission system: manual and automatic. The automatic transmission circuit on the automatic motor, the roller (ballast), is on the primary pulley. In the market, various rollers (weights) are sold, starting from those that are standard and different from the standard with lighter or heavier weight variations. However, there are also aftermarket rollers produced in several automotive industries, one of which is UNIONMATERIAL. The difference lies in the shape and materials used. This study aims to analyze the effect of variations in the shape of the roller on the characteristics of power transmission on automatic motorcycles. The type of vehicle used is a motorcycle produced in 2009 using a dyno test test with two test methods. The first test is from low engine speed ± 1400-1600 rpm to 9000 rpm, while the second test is from medium engine speed ± 4000 rpm to 9000 rpm. In addition, the fuel consumption test was also carried out. The variation used is a roller shape consisting of a round roller, a sliding roller, and a flying roller weighing 12 grams. The highest results obtained at a power of 0.7 HP occurred on the flying roller with 7.1 HP/ 3916 rpm, while the torque was 5.19 N.m on the flying roller (23.96 N·m/1250 rpm). There is an effect on fuel consumption, but not too significant. The biggest difference occurred in the engine parameter RPM 5000 of 0.1 between the flying roller (0.9 L/h) and sliding roller (0.9 L/h) with the round roller (1 L/h) - this happens because the shape of the flying roller is not cylindrical and more dynamic, which is adapted to the movable drive face. There is an additional wing on the roller weight. The data from the results of this study have implications for increasing vehicle performance without changing engine capacity, which requires large costs.

Numerical and experimental analyses for performance and emissions assessment of a four-stroke engine powered by oleic acid methyl ester biofuel made from waste frying oil

<p style="text-align:justify"><span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,sans-serif"><span lang="EN-US" style="font-size:12.0pt"><span style="line-height:150%"><span style="font-family:"Times New Roman",serif">Recently, several earlier works conducted research works dedicated to replacing fossil-based fuels with environmentally friendly ones. The goal of the research is to construct a multivariate linear regression model for the attributes of a four-cylinder diesel engine fueled by biodiesel. In this context, the goal of the research is to structure a multiple linear regression example for characterizing a four-cylinder engine fueled by biodiesel. In fact, experimental research was conducted on an agricultural tractor equipped with a 4-cylinder direct-injection diesel engine. The biodiesel is made from waste frying oil without blending referred to as the oleic acid methyl ester (OAME) biofuel. The biodiesel was extracted through a chemical transesterification reaction. The four-stroke engine is tested for both pure OAME biofuel and conventional diesel. One-dimensional numerical simulations were conducted. A strong correlation between numerical and experimental data was observed, validating the numerical model. Using the engine model, in-cylinder pressure, heat release rate, in-cylinder temperature, and emissions including Carbon monoxide (CO), nitrogen oxides (NO<sub>x</sub>), and Carbon dioxide (CO<sub>2</sub>) were recorded across a broad range of engine operating speeds. Additionally, brake-specific fuel consumption (BSFC) and brake power were numerically calculated and compared to experimental data. The results showed that usage of the OAME as a biofuel could be a promising solution that enables similar performances with lower CO emissions compared to petroleum diesel particularly at low engine speeds.</span></span></span></span></span></span></p>

Investigation on the lean-combustion characteristics of non-uniform orifice pre-chamber spark plug in low engine speed working conditions compared with high energy spark ignition

For a long time, pre-chamber jet ignition has been an effective method to achieve stable lean-combustion of the engine. However, due to the lack of an additional fuel injector, the passive pre-chamber easily leads to unstable combustion and even misfires during the engine’s low-speed working conditions. This study used simulation and optical single-cylinder engine visualization experiments to investigate the ignition and combustion performance of the pre-chamber spark plug (PCSP) ignition system and different orientations of the scavenging jet nozzle in the cylinder. The results indicate that the PCSP at low speed (1200 r/min) can improve the lean-combustion load performance by up to 6.7% compared with traditional high-energy spark ignition but cannot significantly improve the lean combustion limit and stability. In addition, under each λ condition, the scavenging jet nozzle face toward one of the intake valves (IV2) is most advantageous. The effect of lean combustion on reducing NO began to manifest after λ > 1.3 and achieved the best at 1.6. This kind of jet ignition pre-chamber provides a more stable ignition solution than high-energy spark ignition for low speed and medium/low load aspects.

The Influence of Pre-Chamber Parameters on the Performance of a Two-Stroke Marine Dual-Fuel Low-Speed Engine

With increasing environmental pollution from ship exhaust emissions and increasingly stringent International Maritime Organization carbon regulations, there is a growing demand for cleaner and lower-carbon fuels and near-zero-emission marine engines worldwide. Liquefied natural gas is a low-carbon fuel, and when liquefied natural gas (LNG) is used on ships, dual-fuel methods are often used. The pre-chamber plays a key role in the working process of dual-fuel engines. In this paper, an effective three-dimensional simulation model based on the actual operating conditions and structural characteristics of a marine low-pressure dual-fuel engine is established. In addition, the effects of changing the Precombustion chamber (PCC) volume ratio and the PCC orifice diameter ratio on the mixture composition, engine combustion performance, and pollutant generation were thoroughly investigated. It was found that a small PPC volume ratio resulted in a higher flame jet velocity, a shorter stagnation period, and an acceleration of the combustion process in the main combustion chamber. When the PCC volume was large, the Nitrogen oxygen (NOx) ratio emission was elevated. Moreover, the angle of the PCC orifice affected the flame propagation direction of the pilot fuel. Optimizing the angle of the PCC orifice can improve combustion efficiency and reduce the generation of NOx. Furthermore, reasonable arrangement of the PCC structure can improve the stability of ignition performance and accelerate the flame jet velocity.

The impact of scavenging air state on the combustion and emission performance of marine two-stroke dual-fuel engine

The scavenging process significantly affects the combustion and emission performance of marine low-speed two-stroke dual-fuel engines. Optimizing scavenging air pressure and temperature can enhance the engine's combustion efficiency and emission control performance, thereby achieving more environmentally friendly and efficient operation of dual-fuel engines. This study focuses on marine low-speed two-stroke dual-fuel engines, analyzing the effects of scavenging air pressure (3.0 bar, 3.25 bar, 3.5 bar, and 3.75 bar) and scavenging air temperature (293 K, 303 K, and 313 K) on engine performance and emission products. The results indicate that scavenging air pressure has a greater impact on engine performance than scavenging air temperature. An increase in scavenging air pressure leads to higher thermal efficiency and power. As the scavenging air pressure increases from 3 to 3.75 bar, the indicated thermal efficiency (ITE) increases from 44.02 to 53.26%, and indicated mean effective pressure (IMEP) increases by approximately 0.35 MPa. Increased scavenging air pressure improves nitrogen oxide (NOx) and hydrocarbons (HC) emissions. For every 0.25 bar increase in scavenging air pressure, NOx emissions decrease by 3.53%, HC emissions decrease by 33.35%, while carbon dioxide (CO2) emissions increase by 0.71%. An increase in scavenging air temperature leads to lower ITE and IMEP. As the air temperature changes from 293 to 313 K, the ITE decreases by approximately 1%, and IMEP decreases by about 0.04 MPa. Increased scavenging air temperature improves CO2 emissions. For every 10 K increase in the air temperature, the CO2 emissions decrease by 0.02%, while NOx emissions increase by 4.84%, HC emissions increase by 34.39%. Therefore, controlling scavenging air pressure is more important than scavenging air temperature in the operational management of marine two-stroke engines. Higher power and lower NOx and HC emissions can be achieved by increasing the scavenging air pressure.

Evaluation of Ammonia Co-fuelling in Modern Four Stroke Engines

Ammonia is emerging as a promising alternative fuel for longer range decarbonised heavy transport, particularly in the marine sector due to highly favourable characteristics as an effective hydrogen carrier. This is despite generally unfavourable combustion and toxicity attributes, restricting end use to applications where robust health and safety protocols can be upheld. In the currently reported work, a spark ignited thermodynamic single cylinder research engine equipped with gasoline direct injection was upgraded to include gaseous ammonia port injection fuelling, with the aim of understanding maximum viable ammonia substitution ratios across the speed load operating map. The work was conducted under overall stoichiometric conditions with the spark timing re-optimised for maximum brake torque at all stable logged sites. The experiments included industry standard measurements of combustion, performance and engine-out emissions (including ammonia ‘slip’). With a geometric compression ratio of 12.4:1, it was possible to run the engine on pure ammonia at low engine speeds (1000–1800 rpm) at low to moderate engine loads in a fully warmed up state. When progressively dropping down below a threshold load limit, an increasing amount of gasoline co-firing was required to avoid engine misfire. Due to the favourable antiknock characteristics, pure ammonia operation was up to 5% more efficient than pure gasoline operation under stable operating regions. A maximum net indicated thermal efficiency (ITE) of 40% was achieved, with efficiency tending to increase with speed and load. For the co-fuelling of gasoline and ammonia in a pure ammonia attainable operating region, it was found that addition of gasoline improved the combustion, but these improvements were not sufficient to translate into improved thermal efficiency. Emissions of ammonia slip reduced with increased gasoline co-fuelling, albeit with increased NOx. However, the reduction in ammonia slip was nearly ten times the increase in NOx emissions. Comparing pure ammonia and pure gasoline operation, NOx reduced by ~60% when switching from pure gasoline to pure ammonia (as the latter is associated with longer and cooler combustion). Results were finally compared to those obtained a modern multicylinder Volvo ‘D8’ turbo-diesel engine modified for dual-fuel operation with ammonia port fuel injection (PFI), with the focus of the comparison being ammonia slip and NOx emissions.

Simulation and verification of cylinder head’s temperature field for marine low-speed engine

Abstract The high load capacity of marine low-speed engines poses a challenge to the thermal load of the cylinder head and temperature field simulation can guide its structural design and optimization. The 3-dimensional models of the fluid domain for the cooling water and the solid domain for the cylinder head are established and meshed, the fluid domain model is simulated to research the heat transfer pattern by Fluent software, and the surface temperature and heat transfer coefficient of the cooling water is calculated. The thermal boundary conditions of the gas in the cylinder are simulated through the analysis of the engine working process. The temperature of the cylinder head is calculated based on the fluid-structure interaction model with the thermal boundary conditions by Workbench software. The validation of the model is carried out by comparing the simulated and measured temperature data in the heated inner wall of the cylinder head. The research results show that compared with the measured value, the error of simulation results is small, which shows that the model and method are reasonable. The temperature in the inner wall of the combustion chamber is low, which can provide possibilities to appropriately improve the power density of the low-speed engine and reduce the risk of low-temperature corrosion.

Features of the operation of the lubrication system for lubricating ships' low-speed engines

The article examines the optimization of high-alkaline cylinder oil consumption in lubrication systems of marine low-speed engines (MODs), as well as the peculiarities of operation of the cylinder lubrication system in view of modern trends in the development of low-speed marine engines. An overview of the lubricator lubrication systems of the cylinders of marine main engines was carried out and possible prospects for improving the lubricator lubrication systems of the cylinders of marine diesel engines were considered. Attention is paid to the causes of occurrence and methods of combating a whole range of problems, which represent the possibility of increased wear of cylinder sleeves, pistons, piston rings, this is related to the type and grade of fuel and its sulfur content. Sulfur in the fuel is neutralized with the help of cylinder oils with high alkalinity, problems arise when changing the grade of fuel, this requires changing the brand of cylinder oil (CLO BN). The possibility of using a cylinder oil mixing system (ACOM) to neutralize sulfur in the fuel and improve protection against low-temperature corrosion of MOD cylinder liners is proposed and considered. This system mixes and doses cylinder oil depending on the load of the ship's engine and the type of fuel. ACOM allows the dosing of oil on marine engines operating in dual fuel consumption (SDF) modes, where the ratio between pilot (ignition) and gas fuel is defined, the system mixes two different types of cylinder oil into one with the required BN base number, it can be determined as the oil's ability to neutralize acids produced during use. The results of optimal consumption of cylinder oil, which ensures minimal wear of cylinder liners of a diesel engine, are given. Features of lubrication regimes and control of the technical condition of the cylinder group of marine low-speed diesel engines during their operation at reduced rotation frequency are described

Study on fuel injection stability improvement in marine low-speed dual-fuel engines

Pressure waves within the fuel injection system exert a significant influence on the fuel injection process. This study investigated the impact of pressure waves on injection quantity stability. To quantify the influence of pressure waves on injection quantity stability, the relative standard deviation (RSD) was introduced as a metric. Through computational analysis under various operating conditions, the following results were obtained: when the target rail pressure is constant, the RSD tends to diminish as the injection quantity increases. The elevated RSDs observed during small injection quantities are predominantly attributed to the short power-on period of the solenoid valve. Subsequently, parameter optimization and structural improvements were carried out on the injector to address this problem. The results indicate that optimizing structural parameters alone has a limited effect on reducing RSD. However, by adding a block in the control chamber above the needle to improve the structural layout of the injector, the maximum RSD has been reduced from 21.08% to 4.58% under the action of pressure waves caused by fuel injection, and from 29.24% to 6.67% under the action of given random high-frequency pressure waves. The proposed improvement idea for existing injectors enhances injection stability across the entire operating condition range, thereby improving fuel utilization efficiency.

Numerical Simulation Research on Combustion and Emission Characteristics of Diesel/Ammonia Dual-Fuel Low-Speed Marine Engine

Amid increasingly stringent global environmental regulations, marine engines are undergoing an essential transition from conventional fossil fuels to alternative fuels to meet escalating regulatory requirements. This study evaluates the effects of injection pressure, the timing of ammonia injection, and the pre-injection of ammonia on combustion and emissions, aiming to identify optimal operational parameters for low-speed marine engines. A three-dimensional model of a large-bore, low-speed marine engine in a high-pressure diffusion mode was developed based on computational fluid dynamics (CFD). Simulations were conducted under 25%, 50%, 75% and 100% loads with a high ammonia energy substitution rate of 95%. The results indicate that, compared to traditional pure diesel operation, adjusting the injection pressure and the ammonia injection timing, along with employing appropriate pre-injection strategies, significantly enhances in-cylinder pressure and temperature, improves thermal efficiency, and reduces specific fuel consumption. Additionally, the dual-fuel strategy using diesel and ammonia effectively reduces nitrogen oxide emissions by up to 37.5% and carbon dioxide emissions by 93.7%.

Prospects for the development of drivetrain systems in trucks

The article presents the directions of development of drive systems in trucks. A database of vehicles and their technical data was developed. This data contains information about the drivetrain configuration. The external characteristics of the engines and the structure of the drivetrain were analyzed. It was found that the factors determining development are primarily economic and ecological aspects. It was noticed that, based on the configuration of the drive system, vehicles can be divided according to their purpose and type of transport. Vehicles intended for international transport are characterized by low gears and engines that achieve high torque at low engine speeds. Construction vehicles and vehicles intended for oversize transport are characterized by large gear ratios and torque amplification systems. The structure of electric vehicle drive systems is different from conventional vehicles. Gearboxes usually have two gears, drive axles may have integrated engines located next to the main gear or in the final drive position. The study also made it possible to outline the problem of the short range of such cars and the need for further work on increasing it.

Performance of Motorcycle Fueled with Pertalite‒LDPE Pyrolytic Oil Blendings

Plastic use has expanded substantially, and its waste is primarily disposed of in landfills, which further harm ecosystems owing to inadequate waste management. Pyrolysis, which converts plastic waste into liquid fuel, is one of the potential chemical recycling alternatives for plastic. The purpose of this study is to determine the viability of using pyrolytic oil from an LDPE grocery bag as an alternative fuel for a four-stroke spark ignition motorcycle engine. The LDPE grocery bag was pyrolyzed at 500 oC at a heating rate of 3 oC/min, and the condensed pyrolytic vapor's characteristics were determined. Torque, power, and fuel consumption were investigated using a four-stroke spark ignition motorbike powered by pertalite‒LDPE pyrolytic oil blends. The results reveal that the properties of LDPE pyrolytic oil and pertalite were considerably different; hence, when the blending fuel was applied to the motorcycle, the engine torque and power decreased at low engine speed (2000‒3500 rpm), about equal at medium speed (3500‒5500 rpm), and increased at high engine speed (5500‒8500 rpm). Furthermore, the greater blending fuel greatly reduced fuel usage due to the high viscosity of the LDPE pyrolytic oil.