جستجوی مقالات مرتبط با کلیدواژه « موتور دیزل » در نشریات گروه « مکانیک »

In this research, the effective factors on the liner failure of the turbocharged engine (16rk215T) of the locomotive have been investigated. By preparing three liner samples from different manufacturers and sending them to the laboratory, the mechanical properties, including hardness and tensile strength, as well as the percentage of constituent elements and the difference in their values in different samples, were studied. Next, the effect of the weight percentage of different elements on the mechanical properties of gray cast iron was investigated. By preparing microscopic images at 100x magnification, the background structure was seen. Also, the shape and arrangement of lamellar-graphite in different samples were compared with each other and it effect on the fracture and crack growth in the liner was investigated. Three samples of liner, grade and material have been determined. With the appearance of eutectic phosphide in the structures of two samples A (broken liner) and B (liner with crack), as well as the high percentage of phosphorus, structural defects and the presence of dislocations in the grain cause the failure of these samples. Also, non-uniform production of lamellar-graphite in these two samples, its short length and thickness increases strength, reduces absorption and reduces energy.

The investigation of alternative fuels, such as biodiesel, have been prompted by the detrimental emissions resulting from the combustion of fossil fuels. Undoubtedly, the primary concern in fuel selection lies in the examination of emissions. Hence, the present study aims to examine the performance and environmental life cycle assessment methodologies of a dual fuel diesel engine. Furthermore, a fuel blend is made by combining biodiesel sourced from sunflower oil with varying concentrations of bioethanol (3%, 5%, and 7%) and pure biogas, with a percentage ranging from 50% to 80%. This fuel blend is intended for use in the combustion process. In this study, a total of eight fuel samples were meticulously produced and subsequently examined, alongside diesel fuel which served as the control fuel. The entire life cycle evaluation encompasses several stages, starting with the manufacturing of inputs to the combustion of fuel samples. This includes the extraction of oil from sunflower seeds, the production of biodiesel and bioethanol, as well as the generation of natural gas produced from pure biogas. These processes are regarded as captivating and pioneering topics within the field. The provided samples underwent combustion within a dual fuel engine. The findings indicate that the B5 fuel sample, when combined with a 3% bioethanol additive, demonstrates superior engine performance and reduced exhaust emissions. Furthermore, enhanced conditions were achieved in terms of engine performance and exhaust emissions when operating at the lowest rate of natural gas fractionation, which was 50%. The findings of a thorough life cycle evaluation, which examines the entire process from farm to combustion, indicate that the blend B5E7, consisting of 50% natural gas portion at maximum engine load, demonstrates both environmental friendliness and appropriate performance characteristics.

Diesel engines are considered the main sources of energy production and diesel fuel consumption. The use of biodiesel fuel as a part of diesel engines can have a positive effect on reducing the use of fossil resources and the emission of pollutants. Using biodiesel fuel, along with its advantages, has disadvantages such as increasing the emission of nitrogen oxides, which is considered a toxic gas. Many researchers have proposed different additives to cover some of the disadvantages of biodiesel fuel. In this article, two types of oxygen additives, including dimethyl carbonate and n-butanol, were combined with small amounts in B2 (2% biodiesel and 98% diesel) and B5 (5% biodiesel and 95% diesel) fuels. Using small amounts of these additives can reduce the cost of fuel production. Based on the obtained results, B2D10N10 and B2D10N0 fuel samples were able to increase the braking power of the diesel engine by about 12 and 10%, respectively, compared to B2 fuel. On the other hand, the use of fuel samples containing dimethyl carbonate and n-butanol additives in B2 fuel reduced the special brake fuel consumption by about 18% compared to diesel fuel and about 32% Diesel engines are considered the main sources of energy production and diesel fuel consumption. The use of biodiesel fuel as a part of diesel engines can have a positive effect on reducing the use of fossil resources and the emission of pollutants. Using biodiesel fuel, along with its advantages, has disadvantages such as increasing the emission of nitrogen oxides, which is considered a toxic gas. Many researchers have proposed different additives to cover some of the disadvantages of biodiesel fuel. In this article, two types of oxygen additives, including dimethyl carbonate and n-butanol, were combined with small amounts in B2 (2% biodiesel and 98% diesel) and B5 (5% biodiesel and 95% diesel) fuels. Using small amounts of these additives can reduce the cost of fuel production. Based on the obtained results, B2D10N10 and B2D10N0 fuel samples were able to increase the braking power of the diesel engine by about 12 and 10%, respectively, compared to B2 fuel. On the other hand, the use of fuel samples containing dimethyl carbonate and n-butanol additives in B2 fuel reduced the special brake fuel consumption by about 18% compared to diesel fuel and about 32% compared to B2 fuel. Using the combined additives of dimethyl carbonate and n-butanol increased the thermal efficiency by an average of 15-30% compared to diesel, B2, and B5 fuels. The addition of dimethyl carbonate and n-butanol in combination in small amounts significantly reduced carbon monoxide emissions. The highest amount of carbon dioxide emission occurs in fuels containing the combined compounds of dimethyl carbonate, n-butanol, and B5, which was about 10-15% higher than the control sample. During the optimization process, the B2D3N2 fuel sample was selected as the optimal formulation in combining diesel fuel, biodiesel, dimethyl carbonate, and n-butanol.

Pressure fluctuations during fuel injection are one of the factors that negative effect on performance of diesel engine. These fluctuations are caused by the rapid opening and closing of the nozzles and the creation of pressure waves in the fuel rail. One way to control these pressure fluctuations is to change the injector design and use an accumulator in the injector. This study is performed to investigate the effect of adding accumulator on the injector to control pressure waves in the common rail fuel injection system of diesel engines. As the simulation results show, at injection pressure of 1000 bar and energizing time of 0.8 milliseconds, in the case of no accumulator, the maximum pressure fluctuation in the fuel rail is 1046 bar and the minimum pressure is 891 bar. By adding an accumulator with a volume of 4 cm3, the maximum pressure continued to decrease and reached 1023 bar, and the minimum pressure of the fuel rail increased by 17 bar, 943 bar. These changes are also noticeable in other pressures and energizing times, so the best accumulator that has the most impact on reducing pressure fluctuations is the accumulator with a volume of 4 cm3.

In this study, the combination of biodiesel-diesel, ethanol-diesel, and ethanol-biodiesel-diesel emulsion blends on performance and emissions of a direct injection diesel engine was investigated. High purity ethanol in three levels of 2, 4 and, 6 by volume percent and biodiesel prepared from waste cooking oil in four levels of 5, 10, 15 and 20 by volume percent were mixed with pure diesel. Thus, 11 fuel samples were prepared which were shown with BxEy, that x and y represent the volume percent of biodiesel and ethanol in the prepared mixtures, respectively. The experiments were performed at full load with the change in engine speed from 800 to 1800 rpm, with the interval 200 rpm. The results showed that pure diesel has the lowest specific fuel consumption at all of the speeds compared to other prepared mixtures. Using of B15E6 blend, reduced the emission of carbon monoxide by 40% compared to pure diesel. This mixture also, reduced the emissions of carbon dioxide and hydrocarbon by 27 and 55% compared to pure diesel, respectively.

Numerous studies on using light fuels in compression ignition engines to reduce emission and increase efficiency have been done. The Reactivity Controlled Compression Ignition engines are one of these studies. Nevertheless, using heavy fuels vapor for achieving partially premixed combustion is not investigated. Using diesel fume (to upgrade conventional combustion to premixed combustion) resolves the need for a secondary fuel tank in a car. However, diesel fuel has heavy hydrocarbons and is a high reactivity fuel. So in this study, diesel has evaporated in a tank, and its vapor has injected into the intake air for studying a semi homogeneous combustion. The tests have performed at 2000 rpm (the speed of maximum torque). According to the achieved results, although diesel has heavy hydrocarbons and is a high reactivity fuel, adding diesel fumigation can reduce soot and NOx emissions up to 20% and 50%, respectively. Increasing load reduces the positive impact of adding diesel fumigation on soot and NOx emission reduction. However, the positive impact of adding diesel fumigation continues up to 80% of the full load. Adding diesel fumigation has no impact on cyclic variation and ringing intensity, but increases CO and HC emission. The evaporation of diesel averagely consumes 15% of brake power. Also on average, 5% of diesel evaporation energy can be supplied by recovering heat energy from the exhaust gas (warming up diesel from ambient temperature to the exhaust gas temperature).

Nowadays, due to the competitive market, quality evaluation criteria at different stages of production are very important. One of these criteria is reliability, which is calculated using statistical evaluations of after-sales service data in most cases or with the help of accelerated tests at the early stage of the product development life cycle. In this research study, various accelerated test scenarios in proportion to the stresses on the diesel engine have been conducted to evaluate the lifetime of the connecting rod parts. The considered criterion for the reliability analysis is the time between failures which is evaluated after collecting and classifying the data using accelerated tests and confirming independent and uniform distribution of data via MIL-Hdbk, Laplace’s, and Anderson-Darling functions. Finally, the distribution diagram of reliability at different operating times was drawn using log-logistic statistical distribution, according to the best agreement with the experimental results. The results depicted that the reliability of the connecting rod would be equal to (0.99 @ 177417 hrs.) and (0.95@ 212753 hrs.) kilometers of cumulative operation, respectively, and after 448240 kilometers it would be less than 0.05.

One of the major problems in the world is the supply of energy. Biodiesel is one of the alternative fuels and renewable energy sources. The use of B5 biodiesel in diesel fuel mixtures is common and most countries have planned to use B20 biodiesel. The use of natural gas in diesel engines and the study of the possibility of using it in high quantities is another new solution, which can reduce dependence on diesel fuel. In this study, biodiesel was produced from waste oil by transesterification process and used in two levels of 5 and 20% in diesel composition. Then natural gas was used in three levels of 60, 70, and 80% (% G / T) in the diesel engine. Engine tests were performed at full-load at 1500 rpm. In general, the test results showed that in conditions where biodiesel B20 was used in the composition of diesel fuel and gaseous fuel was used in the amount of 80% in a diesel engine, suitable conditions in terms of reducing emissions, increasing energy efficiency, and reducing economic costs were obtained; Under these conditions, compared to a conventional diesel engine, brake power, and energy efficiency increased by 8.86 and 29.06%, respectively. Also, brake specific fuel consumption, CO and CO2 were reduced by 26.5, 57.58, and 4.54%, respectively. Although the amount of NOx increased slightly, but, decreased the economic cost compared to diesel 26.47% $/kwh, so the results were valuable.

In recent decades, rising greenhouse gas emissions have become a major challenge and concern. Environmental pollution is one of the greatest human challenges of the 21st century. Improving the performance of internal combustion engines and reducing the amount of pollutant emissions has always been a concern for researchers. The use of alternative fuels and the control and adjustment of the lambda coefficient are known as the most effective ways to increase fuel efficiency, reduce pollution and improve engine mobility. Therefore, in this study, the relationship between air-to-fuel equilibrium ratio or lambda coefficient with engine performance and exhaust emissions of a diesel engine using diesel-ethanol fuel blends as an alternative fuel at 1700, 1800 and 1900 rpm engine speeds has been investigated. The results showed that increasing the percentage of ethanol in the diesel-ethanol fuel blend increased the lambda coefficient. This increase reduced engine power and torque. The highest power reduction was achieved at 1900 rpm at the rate of 1.18 kW and the maximum torque reduction at 1800 rpm at the rate of 5.94 N.m. As the lambda coefficient increased, the exhaust oxygen output increased by 42.89% at 1700 rpm. The increase in lambda also reduced the emissions of unburned hydrocarbons and carbon monoxide. Thus, the highest reduction of these pollutants was 23.8% at 1800 rpm and 38.75% at 1900 rpm, respectively. Also, increasing the lambda coefficient slightly increased the nitrogen oxides. Finally, due to the use of diesel-ethanol fuel blends and as a result of increasing the lambda coefficient, a significant reduction in the amount of emissions of exhaust gases was achieved.

Despite recent improvement in energy efficiency of diesel engines, more than 50% of the energy input is lost as waste heat in the form of hot exhaust gases, cooling water, and heat lost from hot equipment surfaces. Exhaust pollution from internal combustion engines can potentially result in severe damages on earth atmosphere, including ozone depletion, global warming, and significant health problems. Waste heat recovery based on Rankine cycle has been identified as a potential solution to increase the energy efficiency and consequently to reduce the engine emissions. In this rather low cost technology, waste heat is recovered in a Rankine cycle, aiming to convert mechanical power into electrical power. Output electrical energy is stored in a battery and can be used in electric usages. In this paper, the possibility of using the exhaust heat recovery system without utilizing the heat of other recyclable materials has been investigated, using the organic Rankine cycle (ORC), in order to increase the efficiency of the diesel engine of the bus. Depending on amount of achievable heat of exhaust, in some performance point of diesel engine, the amount of fluid flow rate and output power of Rankine cycle was calculated. Our results exhibit 5.1 KW increase in the diesel engine power resulting in 1.12% increase in energy efficiency in engine part load condition. The output mechanical power from the micro-generator is converted to electrical power and is stored in an energy storage system. The storage energy can be utilized to supply power for electrical equipment such as fans, bulbs, and also phone chargers of passengers.

Under modern direct injection diesel engine conditions, the spray and combustion processes are known to be controlled by mixing. In large eddy simulation method, large eddies are solved directly and small scales are modeled, so it can potentially improve the predictive capability by better capturing the large-scale mixing of ambient air with the fuel vapor. In this paper, turbulent spray combustion is studied using the large eddy simulation method together with partially stirred reactor model using EPISO- SPRAY code. To develop this code, large eddy simulation method is applied in an Eulerian – Lagranian approach in which conservation equations of both phases are solved and then results of large eddy simulation are compared with those of Reynolds averaged of Navier-Stocks. Simulation of spray combustion using different sub-grid scale models of large eddy simulation method (Simple Smagorinesky and dynamic Smagorinesky) with partially stirred reactor combustion model are presented here. It is shown that with a fine mesh, results are in good agreement with experimental data. Results of non-reacting spray penetration length in gas environment and velocity profile during the intake stage are compared with related experimental data in order to validate the EPISO-SPRAY code performance. It is proved in this study that large eddy simulation results with relative fine mesh are much better than the Reynolds-averaged Navier–Stokes equations results. Results of reacting liquid spray using simple step kinetic and fuel vapor penetration length are compared with experimental data. It is shown that overall characteristics of diesel spray combustion such as liquid spray penetration and fuel vapor penetration are both in good agreement with experimental data using Reynolds-averaged Navier– Stokes equations or large eddy simulation models. Although small differences in the flame shape are seen with the two methods, maximum and minimum temperatures are predicted to be the same in both models.

Diesel-fueled engines, despite all their benefits for heavy-duty vehicles, emit a large amount of particulate matter and Nitrogen oxides. Direct measurements of these vehicles’ exhaust have shown that the major part of emitted particulate matter consists of carbon or soot. The pollutant Black Carbon (BC) has a destructive effect on human’s health and environment and it is necessary to control its emission. For this purpose, BC concentration and its sources should be clearly estimated. In this study, direct measurement of BC concentration was conducted at two air quality monitoring stations in Tehran. This measurement, with a special instrument, illustrates the intensity of presence of BC in Tehran’s air. Other prevailing pollutants, including particulate matters with a diameter of 2.5 micrometers or less (PM2.5) and Nitrogen oxides, were monitored in the same period of time and the results were compared with BC in order to source apportionment and find correlations between pollutants concentrations. The results showed that heavy-duty fleet are the main source of BC and Nitrogen oxide pollution in Tehran’s air. BC concentration increased as soon as heavy trucks were admitted into the streets and remained high during their night activity. After sunrise, when heavy trucks were prohibited, BC concentration decreased to a low level and remained steady until night.

In the present study, we aimed to investigate the optimum amount of surfactants to be used in emulsion and nano-emulsion fuels. This would ideally overcome the probable setbacks rooted in surfactant over use and dramatically decrease fuel production expanses, while preserving the fuel stability. In this regard, tween80 and span80 were exploited to produce emulsion and nano-emulsion fuels. The biodiesel-diesel-water emulsion and nano-emulsion fuels were produced in different quantities and HLBs of surfactant. All evaluations were carried out using the B5 as the base fuel and water volume percentage of 5. The produced emulsions had milky and turbid appearance. Being stable for 8 days, the emulsion with HLB of 6 indicates the highest stability. The volume percentage of 1 at HLB of 6 was determined to be the minimum amount of the surfactants required to produce biodiesel-diesel-water emulsions. Moreover, the volume percentage of 5 with HLB of 8 is reported to be the minimum amount of surfactants required to produce nano-emulsion.

Nowadays, the world is facing to increasing loss of fossil resources, energy crisis and environmental problems. On the other hand, diesel engines due to wide application in various sectors such as transport, agriculture, industry, etc., are the main sources of emissions and fuel consumption. Accurate measurement of fuel consumption and engine pollution is time-consuming and costly. Hence, the main objective of this study was to develop proper linear regression models of some important performance parameters of ITM285 tractor engine based on engine torque and engine speed. Experiments were carried out in 11 levels of primary engine speed (1063, 1204, 1346, 1488, 1629, 1771, 1818, 1913 and 2054 rpm) by 10 N.m steps of torque from zero (no load) to full load. The measured parameters include fuel consumption mass flow, exhaust temperature, instantaneous engine speed, maximum and mean exhaust opacities. Four different linear regression models were used to estimate the parameters. The results of regression models performance evaluation showed that quadratic model had the highest efficiency and the lowest RMSE for all parameters. The maximum and minimum effects of engine torque were on exhaust temperature and instantaneous engine speed, respectively; while, this result was completely reverse for primary engine speed. The results of regression models evaluation showed a high adaptation between the output of each model and the desired output. Also, the fuel mass flow and exhaust temperature were highly correlated to the maximum and mean exhaust opacity with correlation coefficients of 0.96 and 0.99, respectively.

Biodiesel fuel is a methyl ester that is usauly produced from plant oils, animal fats or waste cooking oils by transesterification methods. This fuel can blend with crude diesel and shows different behavior. In some cases, these fuels can be mixed with nanoparticles to improve its performance and emission. In this study, the B20 fuel mixed with Ag nanoparticles were used to evaluate the performance and vibration of a single-cylinder engine, and after the post-processing, the results were analyzed statistically. Ag nanoparticles with ratios of 5, 20, 35, 50, 65 and 80 ppm mixed with B20 fuel were used. The measured characteristics were vibration, torque, power, specific fuel consumption and exhaust temperature for under load engine at three levels speeds of 2500, 2000 and 3000 rpm. The results showed that the vibration, torque, power and temperature exhaust were increased by 10.8, 6.8, 6.8, and 8.3%, respectively, using Ag nanoparticles (Ag50) compared to B20. However, the specific fuel consumption was reduced 6.7% for this fuel.

In this study, a numerical investigation of using Rapeseed Oil in National Diesel Engine has been developed and validated against the experimental data. By using validated model, the effect of injection timing, exhaust gas recirculation and initial pressure on performance and emissions of this engine with three different range of using diesel and biodiesel fuels have been investigated. Biodiesel fuel has two significant characteristics, existing Oxygen Atom in its structure and low lower heating value comparing diesel fuel. The results show by increasing biodiesel fuel, better combustion process has been achieved and consequently, increasing in thermal efficiency and reducing carbon monoxide emission have been observed. Because of different characteristics of biodiesel fuel, increasing and decreasing in the amount of this fuel can effect differently on engine power and producing nitrogen oxide emission.

Performance optimization of diesel engines is the subject of most researchers in the field of internal combustion engine in recent decades. One of the the most effective ways toward optimizing the performance of heating systems is exergy analysis. In this study, energy and exergy concepts are applied to evaluate the performance of a compression ignition engine with premixed gasoline fuel at various loads and constant speed. To reach proper performance of diesel engine with premixed fuel, in addition to first and second-law efficiencies, exhaust emission characteristics are reviewed. The results of this study indicated that greater portion of exergy transfer was due to the irreversibility, averaged 50% while at high loads exergy destruction rate decreased to %5 by using premixed gasoline fuel. Also, energy and exergy losses through exhaust emissions with premixed fuel will be reduced to about %8.5 and %16/5 (averaged on all engine loads), respectively. The use of premixed fuel gasoline can increase energy and exergy efficiency (maximum 8% at high loads) at all loads while NOX pollutants will be reduced. It was also found that both HC and CO emissions with premixed gasoline fuel will be increased at all loads.

In this paper, the effect of fuel injection and intake systems on upgrading the power of RK215 HD diesel engine investigated. The process simulated in four state with full load performance by AVL-Fire V8.3.1 software.
The first state is about the original engine with semi-triangular discharge curve, 139mg fuel injection per cycle, nozzle diameter of 3mm and air intake pressure of 4.2bar. In the second state the effect of changing the discharge curve to rectangular type and reducing the nozzle diameter and increasing fuel injection quantity is investigated which is resulted in 0.2, 21, 16.6 and 27 percent increase in peak pressure, output power, NO and soot emissions, respectively. In the third state, only the effect of air intake pressure increase (5bar) with respect to the second state is considered. In this state the amount of peak pressure, output power and NO emission is increased by 15.3, 26, 9 percent, respectively and soot emission reduced by 4.6%. In the fourth state the nozzle diameter is reduced with respect to the third state. The result is 10.4 and 24 percent increase in peak pressure and output power, respectively. In the other hand, the Soot and NO emissions are decreased about 22 and 4.6 percent, respectively.

In the current study a combined heat and power (CHP) system based on diesel engines is studied. A CHP system is investigated parametrically according to first and second laws of thermodynamics. In this investigation instead of modeling the air standard cycle, the fuel air standard cycle and fuel combustion are simulated, which leads to more accurate results. Since a standard cycle has many differences with an actual cycle, the exhaust gas from combustion chamber of a diesel engine is also used to simulate the CHP system, and the heat exchanger of the CHP is investigated from exergetic and economic viewpoints. It was seen that applying the pre-described system, it is possible to warm up 0.17Kg/s water from 25°C to 68.64°C. This enhances the overall efficiency of the system about 20%, raising it up to 80%. Exergy destruction in heat exchanger is almost high which is due to heat transfer process and high temperature difference in the heat exchanger.