Search Results (74)

This study aimed to investigate the effects of diesel/ethanol/n-butanol mixed fuel on the marine diesel engine combustion and emissions at different ethanol blending ratios, different single injection times, and pre-injection times. In addition, this study takes the injector fault phenomenon as an example, simulates the three fault phenomena of the injector, and uses a variety of algorithms to optimize the probabilistic neural network model to achieve the fault state identification and diagnosis of the injector. The results of research showed that, with the increase in the ethanol blending ratio, the peak cylinder pressure shows a decreasing trend. The ignition delay period is extended, and the peak instantaneous heat release rate increases. Compared with D100, the nitrogen oxide (NO_x) emissions of D50E40B10 mixed fuel are reduced by 12.3%, soot emissions are reduced by 29.18%, and carbon monoxide (CO) emissions are increased by 5.7 times. With the injection time advances, the peak values of cylinder pressure and heat release rate show an increasing trend, soot emissions gradually decrease, and NO_x and CO emissions gradually increase. The peaks of the cylinder pressure and heat release rate in the pilot injection stage gradually decrease as the pilot injection time advances, while the peak heat release rate in the main injection stage increases. In terms of emissions, NO_x emissions first decrease and then increase as the pilot injection time advances, while soot emissions gradually increase. The average accuracy of the PSO-PNN neural network model reaches 90%, and the average accuracy of the WOA-PNN neural network model reaches 95%. Therefore, the WOA-PNN neural network model is determined to be the optimal injector fault diagnosis model, which can be applied to the identification and diagnosis of injector fault states of diesel engines. Full article

This study investigates the impact of circumferential angle (φ) and interaction angle (θ) between hydrogen jets and diesel sprays in a co-axial hydrogen–diesel injector on combustion and emissions in a hydrogen–diesel dual-fuel engine using 3D CFD simulations. The results demonstrate that a co-axial dual-layer nozzle design significantly enhances combustion performance by leveraging hydrogen jet kinetic energy to accelerate fuel–air mixing. Specifically, a co-axial alignment (φ = 0°) between hydrogen and diesel sprays achieves optimal combustion characteristics, including the highest in-cylinder pressure (20.92 MPa), the earliest ignition timing (−0.3° CA ATDC), and the maximum indicated power of the high-pressure cycle (47.26 kW). However, this configuration also results in elevated emissions, with 29.6% higher NOx and 34.5% higher soot levels compared to a φ = 15° arrangement. To balance efficiency and emissions, an interaction angle of θ = 7.5° proves most effective, further improving combustion efficiency and increasing indicated power to 47.69 kW while reducing residual fuel mass. For applications prioritizing power output, the φ = 0° and θ = 7.5° configuration is recommended, whereas a φ = 15° alignment with a moderate θ (5–7.5°) offers a viable compromise, maintaining over 90% of peak power while substantially lowering NOx and soot emissions. Full article

Nowadays, the use of ammonia as a green fuel for internal combustion engines has attracted wide attention. The diesel/ammonia dual direct injection mode has shown great potential, but there is still a lack of basic research on injection strategies for this mode. In this study, the combustion and emission characteristics of diesel/ammonia dual direct injection mode were investigated using a rapid compression and expansion machine (RCEM) combined with CONVERGE software_v3.0. The research focuses on the effects of two injection strategies, including ammonia injection pressure, the ammonia injector nozzle hole diameter, and the compression ratio. The results indicate that minor increases in ammonia injection pressure have negligible impacts on emissions with the same nozzle hole diameter. Increasing the nozzle hole diameter significantly reduces unburned ammonia emissions while increasing HC and N₂O emissions. Increasing the compression ratio enhances diesel combustion but does not significantly affect ammonia combustion. Considering the ammonia energy substitution rate and the combustion performance of the actual engine, a high ammonia injection pressure and compression ratio are necessary for engine applications, while an appropriate ammonia orifice diameter is required to meet the emission performance. Full article

Ammonia, being 17.6% hydrogen by mass, is regarded as a hydrogen carrier and carbon-free fuel as long as its production methods rely on renewable energy sources. The production and combustion of green ammonia do not generate carbon dioxide, offering a promising avenue for substantial reductions in greenhouse gas (GHG) emissions from a well-to-wake perspective. This paper presents a comprehensive methodology for the development and validation of a thermodynamic model for a two-stroke low-speed marine engine incorporating a hybrid ammonia-diesel diffusion combustion system. The simulation tools are rigorously validated using experimental data obtained during diesel operation. Subsequently, the study explores various aspects of the novel ammonia-diesel combustion system, addressing combustion and emissions characteristics. The investigation incorporates diverse simulation scenarios involving direct fuel injection through dedicated valves into the cylinder head of a six-cylinder, turbocharged compression-ignition engine. The engine features two diesel injection valves, employed to initiate the combustion process, and two ammonia injection valves. Simulation scenarios include variations in the injection timing of the pilot diesel injector and the relative orientation of diesel and ammonia sprays. Case C emerges as the preferred configuration, demonstrating superior metrics in terms of combustion stability, air-fuel mixing, and emissions profile compared to other cases. The results indicate a reduction of CO₂ emissions of approximately 95% in mass compared to the baseline diesel operation. Furthermore, notable reductions in NO_x emissions are observed, preliminarily attributed to the lower flame temperature of ammonia. Despite the appearance of N₂O emissions as a result of ammonia oxidation, the overall potential reduction in GHG emissions, in CO₂-equivalent terms, exceeds 85% at selected operating points. This work contributes valuable insights into the optimization of cleaner propulsion systems for maritime applications, facilitating the industry’s transition toward more sustainable and environmentally friendly practices. Full article

This study conducts a detailed analysis of the mixed combustion of dissociated methanol gas (DMG) and methanol in a marine medium-speed methanol engine through numerical simulation methods. The research focuses on the impact of partially replacing methanol with DMG on engine combustion characteristics and emissions under both stoichiometric and lean-burn conditions. Employing the MAN L23/30H diesel engine as the experimental model, direct injection of DMG is achieved by installing gas injectors on the cylinder head. Utilizing the CONVERGE software, we simulate the injection and combustion processes of methanol and DMG and subsequently analyze the effects of varying DMG blending ratios on in-cylinder pressure, heat release rate, mean chamber temperature, as well as NOx, HC, CO, and soot emissions. The research findings indicate that, under stoichiometric combustion conditions at both rated and idle speeds, the incorporation of DMG leads to increases in the peak in-cylinder pressure, peak heat release rate, and peak in-cylinder temperature, with these peaks occurring earlier. Additionally, it is observed that emissions of HC, CO, and soot are reduced. Under lean combustion conditions at rated speed, in the absence of DMG blending, increasing the excess air ratio results in an initial increase followed by a decrease in both fuel-indicated and overall-indicated thermal efficiency. However, with the blending of DMG, these efficiencies improve as the excess air ratio increases. Notably, the highest efficiencies are achieved when the excess air ratio is 1.8 and the blending ratio of DMG is 30%. Full article

This article presents the authors’ considerations regarding the possibilities of developing fuel equipment for modern compression ignition engines used in special and non-road vehicles. The paper discusses the process of fuel combustion and atomization in the chamber of a piston combustion engine. The paper then presents the concept of modifying the atomizer of a modern fuel injector for operation using hydrogen-containing fuels of plant origin. The authors present a review of tests performed using an engine dynamometer on a modern engine with a Common Rail system running on biofuel. The CI engine operated with standard and modified fuel injectors. During the tests, the external ecological characteristics of the engine were analyzed as a function of rotational speed; the values of injection doses at individual rotational speeds and their effects on the characteristics were read from the current parameters, and the pressure and temperature in the engine’s combustion chamber were measured. The research results show that implementing the changes proposed by the authors of this work is a good direction for the development of compression ignition engines. Full article

The valve, armature, and armature pin are critical factors influencing the hydraulic pressure differences in diesel injectors, and are essential for injection and backflow quantity control. These components play crucial roles in enhancing energy efficiency and reducing engine emissions. This experimental study investigated the effects of clearance between the valve, armature, and armature pin guidance. Forty-nine 2000 bar common-rail injectors (Bosch) were tested in calibrated stations. Injection quantities were assessed at both minimum and maximum operational pressures. Backflow rates were specifically examined at maximum pressure. A correlation matrix was created using Python to analyze the relationship between inputs and outputs, identifying dominant characteristics that define injector behavior. Increased injector precision correlated with reduced fuel consumption and enhanced energy efficiency. The study found that the effect of clearance between the armature and armature pins was more significant than that between the valve and armature. Injection quantities were observed to increase with pressure, and no critical difference in injection quantities was noted among different diameter groups at the minimum pressure point. Backflow quantities were consistent within groups when the armature–armature pin and valve–armature clearances were minimized. Full article

Plastic is one of the most widely used materials worldwide. The problem with plastic arises when it becomes waste, which needs to be treated. One option is to transform plastic waste into synthetic fuels, which can be used as replacements or additives for conventional fossil fuels and can contribute to more sustainable plastic waste treatment compared with landfilling and other traditional waste management processes. Thermal and catalytic pyrolysis are common processes in which synthetic fuels can be produced from plastic waste. The properties of pyrolytic oil are similar to those of fossil fuels, but different additives and plastic stabilizers can affect the quality of these synthetic fuels. The quality of fuels and the permissible particle sizes and number density are regulated by fuel standards. Particle size in fuels is also regulated by fuel filters in vehicles, which are usually designed to capture particles larger than 4 μm. Problems can arise with the number density (quantity) of particles in synthetic fuels compared to that in fossil fuels. The present work is a numerical study of how particle size and number density (quantity) influence cavitation phenomena and cavitation erosion (abrasion) in common-rail diesel injectors. The results provide more information on whether pyrolysis oil (synthetic fuel) from plastic waste can be used as a substitute for fossil fuels and whether their use can contribute to more sustainable plastic waste treatments. The results indicate that the particle size and number density slightly influence cavitation phenomena in diesel injectors and significantly influence abrasion. Full article

In order to improve the fuel economy of heavy-duty diesel engines under high-load conditions, based on the combustion pathway model, it is proposed that the proportion of lean mixture with 0 < Φ < 1 is the most important spray characteristic affecting the overall diesel combustion process. Answering the question of how to increase the proportion of lean mixture inside the spray is the key to achieving the efficient and clean combustion of diesel engines. This paper investigated the mechanism of injector nozzle diameter on the in-cylinder air–fuel mixture and combustion process based on a high-density and lean mixture characteristic combustion strategy. The experimental results show that with an increase in nozzle diameter, the peak pressure and instantaneous heat release rate significantly increase, the combustion duration is shortened by about 20%, and the heat release becomes more concentrated. At 1200 rpm and IMEPg~2.3 MPa conditions, the indicated thermal efficiency increases by 1.3%, reaching a maximum of 51.5%. The numerical simulation results show that with the increase in nozzle diameter from 0.169 mm to 0.218 mm, the spray ejection momentum per unit time increases by 30%, the momentum transferred to the air by the spray increases, the oxygen transport process becomes more intense, and the air entrainment mass during the spray free development stage increases by 42%. The proportion of lean mixture inside the spray throughout the entire spray development process increases, resulting in an increase in the heat release rate of the lean mixture, making the overall combustion more intense and concentrated. Full article

The present research analyses the injection rate of a direct rail injection diesel engine, focusing specifically on the influence of the nozzles and various operating conditions from real road tests on the rate of injection. A diesel injector test bench was used for feedback with real data from the test vehicle under real road conditions. An analysis of the behaviour of the injection rate was carried out using the zero-dimensional model. This model generated a predictive model that incorporated the five variables identified through a developed multivariate analysis of variance, showing a high correlation of dependence between variations in injection pressure, the diameter of the holes, and the number of holes with greater representativeness. The results obtained showed that the nozzle geometry and the physical properties of the fuel had a direct effect on the injection rate. This analysis enriches the understanding of fuel injection and its effects on diesel engine performance by providing an analysis of the system components that influence the injection rate and generating a simple tool to feed thermodynamic diagnostic models. The proposal model may be used as an input in thermodynamics predictive models and reduce the simulation load in computational fluid dynamics predictive models. Full article

This paper presents a fuel injection rate predictive model based on zero-dimensional correlations from experimental results. This model estimates the fuel injection rate behavior with varying parameters such as fuel injection pressure-injector energizing, the injection nozzle geometrical characteristics, and fuel viscosity. The model approach was carried out with diesel fuel. Then, the model was applied to the use of two alternative low-carbon fuels without diesel. An experimental methodology was used under controlled conditions, employing an injection rate indicator to measure the injection parameters in real time. The setup was carried out on a pump test bench using a common rail injection system. The results show that the model can be adapted to different injection conditions and fuels. Full article

Improving diesel engine performance requires a comprehensive understanding of fuel atomization and air–fuel mixing within the combustion chamber. Numerous studies have been conducted to reduce emissions and enhance diesel engines. However, further investigation is required on the detailed diesel spray process. In this study, we adopted extinction measurement to analyze the effects of a fuel injection pressure range of 300 to 700 bar on spray morphology. For the extinction imaging setup, we utilized a high-intensity continuous LED source along with a diffuser to ensure uniform light distribution. The high-speed extinction and image processing results indicate that increasing the injection pressure from 300 to 700 bar effectively produced a smaller particulate size (15% reduction) and a better air–fuel mixing process. Especially at the end of injection, our results show smaller liquid ligaments (50% reduction) and droplets around the injector tip with higher injection pressure cases. Full article

This article discusses the potential applications of the Fuel Shot liquid catalyst in compression ignition (CI) engines for reducing toxic substances in exhaust gases. Incorporating catalysts into fuel can optimize the combustion process, consequently reducing the emission of toxic substances into the atmosphere. Toxic compounds, such as nitrogen oxides, particulate matter, and hydrocarbons, adversely affect flora and fauna. Various methods are known for reducing their concentration in engine exhaust gases, one of which is the Fuel Shot liquid catalyst. The authors conducted experiments on a Fiat 1.3 JTD engine with a Common Rail system. The results indicate that the application of the liquid catalyst reduces the content of nitrogen oxides and hydrocarbons in the exhaust gases and slightly decreases fuel consumption. Additionally, investigations were carried out on the engine’s injection apparatus, which was fueled with modified fuel. The findings demonstrate that the fuel additive does not affect the wear of precision parts of fuel injectors and high-pressure pumps. Full article

The combustion process of traditional diesel engines is mainly determined by the injection timing of diesel. There is a trade-off relationship between the soot and NOx (nitrogen oxides) during this combustion process, making it difficult to reduce these two emissions simultaneously. The use of methanol can not only solve the above problem, but also replace some fossil fuels. However, the effects of methanol injection into the intake duct on the flame propagation in diesel/methanol dual-fuel engines is not yet clear, and there is relatively little research on it. The effects of methanol addition on the combustion process of diesel/methanol dual fuel (DMDF) were achieved based on a modified optical engine in this paper. One injector is installed on the intake inlet to inject methanol, and the other injector is installed in the cylinder to inject diesel in two stages before the top dead center of compression. There are three tests conducted separately in this paper. Firstly, the effects of the methanol ratio (40%, 50%, 60%, and 70%) on the combustion process are investigated, with the total heat remaining unchanged. Secondly, the effects of the pre-injection mass of diesel (20%, 30%, 40%, and 50%) on the combustion process are investigated, which keeps the total diesel mass unchanged. Finally, the effects of the total mass of diesel on the combustion process are investigated while maintaining the mass of methanol unchanged. The dual-fuel combustion process is recorded by a high-speed camera. A combustion analyzer and other equipment were used to analyze the combustion. The results showed that CA10 is delayed, the pressure and the heat release rate (HRR) are reduced, and the number of pixels of the KL factor (KL) decreases significantly with the increasing methanol ratio. CA10 and CA50 are advanced, the pressure and HRR decrease, and the KL increases when the mass of pre-injected diesel increases. CA10 and CA50 are advanced, respectively, and CA90 is postponed due to the increase in diesel mass. The pressure and HRR increase, and the KL increases when the total mass of diesel increases. Full article

The presented paper addresses two significant issues of the present time. In general, the studies of the effect of synthetic fuels on cavitation formation and cavitation erosion prediction in the nozzle tip of common-rail diesel injectors were addressed. The first problem is plastic waste, which can have a significant negative environmental impact if not treated properly. Most plastic waste has high energy value, so it represents valuable material that can be used in resource recovery to produce various materials. One possible product is synthetic fuel, which can be produced using thermal and catalytic pyrolysis processes. The first issue addressed in the presented paper is the determination of fuel properties since they highly influence the fuel injection process, spray development, combustion, etc. The second is the prediction of cavitation development and cavitation erosion in a common-rail diesel injector when using pyrolytic oils from waste plastic. At first, pyrolytic oils from waste high- and low-density polyethylene were obtained using thermal and catalytic pyrolysis processes. Then, the obtained oils were further characterised. Finally, the properties of the obtained oils were implemented in the ANSYS FLUENT computational program and used in the study of the cavitation phenomena inside an injection nozzle hole. The cavitating flow in FLUENT was calculated using the Mixture Model and Zwart-Gerber-Belamri cavitation model. For the modelling of turbulence, a realisable k–ε model with Enhanced Wall Treatment was used, and an erosion risk indicator was chosen to compare predicted locations of cavitation erosion. The results indicate that the properties of the obtained pyrolytic oils have slightly lower density, surface tension and kinematic viscosity compared to conventional diesel fuel, but these minor differences influence the cavitation phenomenon inside the injection hole. The occurrence of cavitation is advanced when pyrolytic oils are used, and the length of cavitation structures is greater. This further influences the shift of the area of cavitation erosion prediction closer to the nozzle exit and increases its magnitude up to 26% compared to diesel fuel. All these differences have the potential to further influence the spray break-up process, combustion process and emission formation inside the combustion chamber. Full article