نشریه سوخت و احتراق
سال پانزدهم شماره 3 (پیاپی 40، پاییز 1401)

The present study aimed to model and optimize the performance and emission characteristics of a diesel engine fueled with water-diesel emulsions containing metal-organic framework nanoparticles using a combination of adaptive neural-fuzzy inference system with optimal algorithm particle swarm generation (PSO-ANFIS). The multi-purpose particle swarm algorithm (MOPSO) was used to optimize engine performance and fuel composition. Water inclusion rate, engine load, and metal-organic framework nanoparticle concentration were considered as input parameters of the model. Brake specific fuel consumption, brake thermal efficiency, CO, CO2, UHC, NOx, and smoke were considered as model outputs. Sixteen experimental data were used in modeling and optimization processes. The results showed that the developed PSO-ANFIS models could accurately predict the objective functions. There was a good agreement between all the target data and the output of the developed models. According to the optimization results, water-diesel emulsion fuel containing 26.27 ppm metal-organic framework nanoparticles and 4.14 wt% water under engine load 60.15% of the full-load operating level was found to be optimal conditions.
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In recent decades, low temperature combustion engines have been the focus of researchers as an effective strategy to achieve the optimal combustion model. In this method of combustion, initially, the fuel with high octane is sprayed in the inlet manifold and then another fuel with a high cetane number is injected into the combustion chamber at a different time. Combustion in reaction-controlled compression ignition engines does not use direct control tools and depends on the reactions' initial conditions and chemical kinetics. Considering the importance of ignition timing and its control in low-temperature combustion engine performance, in this study, using the control variables of ignition delay, fuel injection time and maximum pressure inside the cylinder, along with the fuel injection system as the ignition control operator, to the experimental investigation of the performance of a direct injection low temperature combustion engine has been discussed. The results show that the injection time of diesel fuel inside the cylinder is one of the most important factors influencing the performance and efficiency of the engine. For low methane injection rate (15 slm), with increasing delay in pilot fuel (diesel) injection time, the value of the maximum heat release rate and specific fuel consumption decreased, while the mean effective pressure and gross indicator efficiency increased. By controlling the reactivity of the mixture and the fuel injection time with more reactivity, it is possible to achieve the appropriate ignition time, which indicates the importance of the fuel injection time as an essential control parameter in the ignition control of a low-temperature engine. In general, the methane rate has a secondary effect on ID compared to SOI.

The driving force of typical urban vehicles is usually produced by spark-ignited internal combustion engines operating with gasoline as fuel. The combustion of gasoline fuel in spark ignition engines leads to air pollution in urban areas and also to the reduction of fossil fuel reserves. Due to the biological structure of the fuel, using ethanol as a blend with gasoline, along with other alternatives to fossil sources, is one of the solutions to decrease gasoline-based air pollution. Even though adding ethanol compounds allows better fuel combustion and reduces pollutants, these compounds lead to an elevated emission of nitrogen oxides into the air when used at higher percentages in blended with fuel. On the contrary, glycerin, a byproduct of the biodiesel production process, acts as a restricting factor in the mass production of biodiesel. Taking these into account, this study proposes a novel blend of biofuels for gasoline fuel by converting glycerin into solketal and then injecting it into ethanol-containing gasoline fuel. The proposed fuel blend provides optimal performance and comes with the least emission of pollutants. The results showed that adding 5%  by volume of solketal to gasoline fuel containing 20% ​​ by volume of ethanol resulted in the best engine performance and lower air pollution compared with the combustion of pure gasoline alone and gasoline fuel containing 20% ​​ethanol. In addition, brake specific fuel consumption with fuel containing 5% solketal at 25, 50 and 75% torques has decreased by five, two and seven tenths of percent, respectively. Also, the addition of 5% solketal, in addition to maintaining the positive effects of adding ethanol in reducing engine exhaust emissions, causes a significant reduction in the emission of nitrogen oxides by about 90%, which is one of the disadvantages of adding ethanol to fuel

In this study, the experimental investigation of oxygen-methane combustion has been done by investigating the effect of nitrogen dilution in a novel spiral-channel combustion chamber along with the recovery of thermal energy of the products.  The methane-oxygen non-premixed flame by a fixed equivalence ratio of 1.69, with nitrogen dilution percentages of 0%, 5%, 10%, and 18%, has been investigated with the spectroscopy method. The chamber is made of aluminum and created as a spiral-form channel to aid heat recovery. In this chamber, the combustion gases then pass a path parallel to the inlet flow, causing the inlet gases to be preheated. Also, oxygen is diluted and mixed with nitrogen before entering the chamber. Based on the results, by increasing of the diluent ratio the reduction of the H2O* radical radiation spectrum has been observed, where indicates complete combustion. In general, with the increase of the dilution ratio, the flame length increases, and in 5% and 10% dilution states, the best temperature distribution uniformity, and the completion of the combustion reaction chain are observed.

Steam reforming of natural gas is the most used method to produce the hydrogen required for chemical industries. The increased demand for hydrogen consumption makes development of new technologies for hydrogen production. One of the proposed technologies is a catalytic membrane reactor due to removal of hydrogen from the reaction side and prevents the achievement of equilibrium conditions. This research investigates kinetic reaction model with utilization of Ru-based catalysts with MgO and Nb2O5 as the supports that develop the activity and selectivity of this reaction in the temperature range of 350ºC-750ºC and pressure range of 2-30 bar. The effects of different operational parameters such as temperature, pressure of the reaction, methane to steam ratio, membrane thickness, and sweep gas on total methane conversion and hydrogen production were studied. Based on the Δ-index, the optimum condition of catalytic membrane reactor was obtained within the operating condition ranges of temperature 410–475 0C, pressure ≥ 20 bar, thickness <10 μm, steam-to methane ratio 2< m < 3 and sweep factor s ≥ 10.

To achieve the zero carbon emissions goal, it is of great importance to replace conventional hydrocarbon fuels with carbon-free fuels. In terms of carbon-free fuel, ammonia has several advantages over hydrogen, despite of problems such as low flame speed and high NOx emission. The present experimental study investigates the effect of adding ammonia to methane and its ratio on the combustion performance of a can-type micro-turbine combustion chamber under atmospheric condition at two different heat powers. The results show that with an increase in the percentage of ammonia in the fuel mixture, maximum flame temperature has decreased and combustion has delayed until the end of chamber. Also, the addition of ammonia, despite not reducing CO, results in a sharp increase in the NOx production. In addition, although the outlet temperature of the chamber has not changed much except for one condition, combustion efficiency of the chamber has decreased with the increase of ammonia ratio, and pattern factor is more than the case of pure natural gas. Therefore, although the use of methane/ammonia fuel mixture with stable combustion conditions in the existing chamber is possible, it requires modifications to achieve optimal combustion performance.a
 
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Investigating the effects of pilot fuel containing low percentages of ethanol and water in the diesel-biodiesel fuel mixture in a dual-fuel combustion process with natural gas can have favorable results on the performance and emissions of a diesel engine. In the present study, three levels of ethanol (0, 2, and 4%), two levels of biodiesel (0 and 5%), and four levels of water (0, 0.3, 0.6, and 0.9%) were mixed with diesel fuel. All these fuel samples were considered as pilot fuel in the dual fuel combustion process with an 80% natural gas replacement percentage. Based on the obtained results, the presence of water, ethanol, and the combination of water-ethanol and natural gas can improve the diesel engine's performance by increasing the combustion chamber pressure and reducing the pollutants. The presence of oxygen content in ethanol can improve the combustion process by pushing the combustion toward complete combustion. The results of the optimization using the response surface method showed that the optimal point of engine performance at full load with a fuel sample containing biodiesel in the amount of 2.5 ml, ethanol in the amount of 11.5 ml, water in the amount of 9.3 ml and gas fuel occurs in 65%. Under this condition, compared to the control sample, the braking power increased by about 79%, and the specific fuel consumption decreased by about 58%. This fuel sample reduced the amounts of carbon monoxide, carbon dioxide, nitrogen oxides, and energy production costs by 54, 33, 29, and 39%, respectively, and increased sulfur oxides by 11%.