M. Gholinia, M. Pourfallah, H.r. Chamani,
Volume 19, Issue 2 (2-2019)
Abstract
The heat transfer from walls has a significant role in the correct estimation of temperature distribution in order to investigate the thermal stresses and low cycle fatigue in the engine liner. Therefore, it is necessary to investigate the details of the flow and heat transfer over a wide range of engine operation in the design and exact simulation of the cooling jacket. An efficient approach to study the cooling system is to simulate using Computational Fluid Dynamics (CFD) as a three-dimensional model by simultaneously solving the structure and fluid, which leads to accurate prediction of wall temperature and heat flux. In the present paper, the distribution of heat transfer coefficients (HTC) in the cooling jacket of a 16-cylinder heavy-duty diesel engine has been calculated, using ANSYS/Fluent based on 3D-CFD method. Also, equations of subcooled boiling phenomenon have been solved based on two commonly used patterns of Chen and BDL, and the effects of fluid pressure, velocity, and temperature at the time of the phenomenon of boiling on the heat transfer of cooling jacket wall have been studied. The results indicate that the best condition for a cooling jacket is when the coolant flow in critical heat points reaches to a velocity so that subcooled nucleate boiling occurs.
M. Nazemi Babadi, S. Kheradmand ,
Volume 19, Issue 4 (4-2019)
Abstract
In this paper, the numerical simulation of the diesel and gasoline fuels injection in a constant volume chamber is conducted under the operating conditions of a compression ignition engine with openFoam software. In order to check out the possibility of using gasoline instead of diesel to increase the volumetric efficiency of the compression ignition engine and reduction air pollution, the spray characteristics of the gasoline and diesel under injection pressures of 40 and 80MPa, as well as temperatures of 243, 273 and 313K, is investigated. The simulation results are compared with the experimental data derived from fast imaging techniques. The results show that under the same conditions, the vapor penetration length for the two fuels is approximately equal. Also, due to the lower volatility of the diesel fuel, its liquid penetration length in 40 and 80MPa injection pressure was found to be 7 and 9 mm higher than gasoline, respectively, and high volatility of gasoline leads to enough time to make air and fuel mixtures in compression ignition engine. In addition, the reduction in fuel temperature from 313K to 243K resulted an increase in the penetration of gasoline and diesel liquids by 12 and 10 mm, respectively, and decrease in the evaporation rate, which causes a non-homogeneous mixture and an increase in unburned hydrocarbons and emissions.
N. Hajilary , M. Rezakazemi ,
Volume 19, Issue 5 (5-2019)
Abstract
The combustion system used by the Hoffman furnaces for brick factories has a very low efficiency. In the current paper, the performance of the combustion system of Hoffman furnaces of Kolet Pottery Brick Co has improved, using computational fluid dynamics (CFD) by making changes to the Hoffman furnace torch, including the converging the torch head, inserting the spring in the pipe to create the swirl flow, shortening the nozzle length for the better mixing of the fuel and air, and more. The changes were simulated in each step with the FLUENT simulation software. Based on the theoretical results and simulation, optimized torch was made and a field test was carried out on it in a brick factory and the gases from their combustion were analyzed. As a result of these reforms, the combustion efficiency of the Hoffman furnaces has increased from 27% to 47 %, and consumption of fuel oil has decreased by a third. Also, the CO value of 16854 ppm in the old torch was reduced to 298 ppm in the optimized torch and the NO value ranged from 49 to 18 ppm as a result of optimizations.
A.m. Shamekhi, A.h. Shamekhi,
Volume 19, Issue 5 (5-2019)
Abstract
In this paper, an improved, real-time, highly accurate control-oriented style, named Neuro Mean Value Modeling, is presented for IC engine modeling. This model is a combination of neural networks and mean value model, and is able to overcome the shortcomings of both styles. In other words, taking advantage of both methods, this -box extension will be of more reliability than a mere black-box neural network, and also of more accuracy than roughly white-box mathematical relations of In this paper, the model is modified to become suitable for designing an engine controller. Thanks to the sophisticated methods applied (such as committee method, improved partitioning, and especially, simplifying neural networks’ tasks), neural networks of high accuracy with line-like regressions will be achieved. As will be seen, the model is precisely validated - and it is capable of accurately predicting the engine’s outputs (such as pollutant emissions, manifold pressure, knock probability, and engine speed) all in real time. In the end, the effect of engine control inputs on pollutant emissions and fuel consumption will be examined. The engine employed to establish the model is a ported fuel injection SI engine.
M. Salehi, A.h. Kakaee, Iman Chitsaz,
Volume 19, Issue 10 (10-2019)
Abstract
Natural gas characteristics make it an attractive choice for replacing with oil fuels which causes climatic problems and environmental pollutions in the world. Generally, using natural gas in an internal combustion engine leads to lower volumetric efficiency of the engine, but gas direct injection technology would improve volumetric efficiency. Furthermore, more research is essential for improving the effectiveness of direct injection engines. A partially stratified charge is an appropriate idea for combustion efficiency improvement in direct injection engines. In the present study, a port injection engine is converted to direct injection engine and feasibility and condition of partially stratified mixture formation are investigated. Also, its effects on combustion and efficiency of the engine, with regards to location and injection timing of injector are noticed. Numerically simulation of current study shows that the formation of partially stratified charge, because of using air-guided method and located injector between air intake valves, is so hard and inaccessible. The high momentum of CNG jet makes a rapid motion of injected gas fuel and is not able to perform an appropriate mixture of air and fuel. Accordingly, an increase in air and fuel ratio is locally seen in the combustion chamber as this causes a drop in combustion efficiency. Although the increase in flame propagation and heat release can be expressed as results of this study, however, the benefits of rapid burning of CNG combustion due to the problems that are mentioned are not so impressive.
H. Keshaverzian, M. Jabbari, M. Soheili,
Volume 19, Issue 11 (11-2019)
Abstract
Abrasion in pipelines and fluid transfer equipment along with impurities in oil and gas and other industrial processes is one of the most important problems of oil, gas and petrochemical industries. Repair of this equipment is considered as one of the major challenges in industry. Wearing was created by the impact of solid particles with gas and liquid particles or by the collision of liquid droplets with the inner wall of the fluid passageway. This research aims to examine the factors affecting the rate of vane wearing including circulation speed of compressor vane, size of particles within methane, density of particles in compounds, angle of incidence and target metal stiffness. To obtain and analyze the rate of vanes' wearing, degraded pieces of vanes' substance were provided and were used as specimen according to the operational conditions, exploitation, and transfer of gas. During the experimental steps, the rate of wearing with varying conditions in solution and solid particles' compounds was measured. According to the results, the speed rate of circulation of centrifugal compressor impeller is an important parameter in increasing efficiency. To obtain this parameter, the mechanical and metallurgical properties of the compressors should have a good quality. Also, considering the relationship with a parabola form, the abrasion increases with increasing the density of particle. The results of the research were compared to the existing standards and theories and the approaches were presented to decrease degradation and wearing in centrifugal compressors' vanes.
M. Talei, S. Jafarmadar, Sh. Khalilarya,
Volume 20, Issue 1 (1-2020)
Abstract
In the present research, the performance of a single-cylinder engine with a pre-chamber and natural gas fuel designed in Urmia University has been investigated and the effect of Exhaust Gas Recirculation (EGR) on engine performance has been analyzed. The results indicate that the simultaneous use of the pre-chamber and the EGR reduces significantly nitrogen oxides emission. Also, the amount of unburned hydrocarbons (HC) decreases in the low EGR, but the amount of HC increases significantly with higher EGR. EGR increases the carbon monoxide (CO) emission but does not have a significant effect on carbon dioxide (CO2) emission. Simultaneous use of EGR and pre-chamber can reduce the amount of emission while it can maintain the engine braking. The engine power and the indicated mean effective pressures (IMEP) which are the main indicators of the engine's performance, decrease by 3 to 4 percent for every 5 percent of the EGR. The results show that the EGR reduces the velocity of the jet flames out of the pre-chamber which ultimately reduces the advance of the flame front. Analysis of the results of the experimental test and the simulated model shows that an ideal range for EGR in an engine with a pre-chamber can be defined in which the emission is minimal and the engine power is maintained. In the engine used in this research, the exhaust gas reaction is in the ideal 10% range.
M. Sarabi, E. Abdi Aghdam,
Volume 20, Issue 2 (1-2020)
Abstract
The advantages and disadvantages of using gasoline and NG as single-fuel is a challenge for researchers in development of SI engines. Singular utilization of these fuels results in some advantages and disadvantages from economics, thermodynamics, pollution and development aspects and make it difficult to prefer one to the other. Assuming that using combination of the fuels can modify the output results, in the present research, different combinations of 100, 90, 75 and 60% gasoline and the rest of natural gas, designated as G100, G90, G75 and G60, were investigated in a SI single-cylinder engine at running at 1800rpm, 9 compression ratio and stoichiometric equivalence ratio. After collecting and processing in-cylinder experimental data in the combinations and different spark advances and their experimental data processing, consecutive cycle-to-cycle data were extracted and analyzed with engine output data. First, optimum spark advance of each combination was determined and then, the combinations were compared at their spark advances. The results revealed that increasing natural gas fraction in combination causes substantial reductions in standard deviation, σ, and coefficient of variation, COV of IMEP, so that σ and COV of G60 reduced by 51.6% and 49.2%, respectively, in comparison with G100. Reducing the gasoline presence in combination, the amount of CO2, NOx and HC reduced except G90 which have the higher HC and NOx, whereas, CO amount in G90 decreased to the lowest level. Also, no satisfactory performance was observed in the G90 combination.
M. Sedighi, M. Aelaei, M. Aghnia,
Volume 20, Issue 6 (6-2020)
Abstract
Fuel system is one of the most important parts of the micro gas turbine. Due to the variation of environmental conditions such as temperature, relative humidity of air and height in different geographical locations, the operational features of the fuel system change. In this study, the fuel system of the GTCP85-180 gas turbine is modelled by applying PID mechanical controller. The governing equations of the controller is coupled with classical thermodynamic equations of the gas turbine and the effects of different environmental conditions on start-up and norminal operation of the motor are investigated. The range of variations of the environmental conditions is choosed by considering the geographical locations of Iran. The results of the numerical simulation were verified by comparing the numerical results obtained with written code in Matlab software with experimental measurements. The results showed that the environmental temperature has the strongest effect on the operational features of the fuel control system and causes 16.3% variation of exhaust gas temperature, 3.7% variation of fuel discharge, 14.7% variation of start-up time of the motor and 4.7% variation of fuel pressure in injectors. Also, the start-up operation of the motor showed more sensitivity to environmental conditions compared to normal operation of micro gas turbine.
A. Gharehghani,
Volume 20, Issue 8 (8-2020)
Abstract
Reducing fossil fuel sources together with tighter environmental laws to control the engine exhaust emissions makes the use of cleaner and renewable fuels inevitable. Therefore, the use of biodiesel fuel as a strategy to conserve energy and reduce emissions is becoming increasingly important in engines. On the other hand, biodiesel fuels increase NOx emissions in the engines, which necessitate the use of water additives to reduce the combustion temperature. To compensate for the negative effect of water addition by reducing combustion quality and thus reducing thermal and exergy efficiency, the use of metal-based nano-particles additive can be a reliable solution. In this study, the effect of adding different concentrations of nano-particles on improving efficiency of the first and second laws as well as fuel consumption of a single-cylinder engine with different fuel combinations with BXWYNZ formula (diesel fuel with X% biodiesel mass, Y% water mass%, and Zppm nano-particles), has been studied experimentally. The results of this study show that adding 60ppm nano-particles to B0W5 will improve about 3% efficiency in the first law and 2.5% efficiency in the second law compared to pure diesel fuel. These values were about 4 and 3.8% for 90ppm nano-particles, and 5 and 4.7% for 120ppm nano-particles, respectively. In addition, based on the experimental results, the B15W5N120 has 7.5% higher first-law efficiency and 7% higher second-law efficiency than pure diesel fuel.
S. Ghaffarzadeh, A. Nassiri Toosi , M.t. Zarrinkolah,
Volume 20, Issue 8 (8-2020)
Abstract
RCCI as low temperature combustion is one of the common methods for reducing nitrogen oxides and soot pollutants. In this study, the effect of exhaust gas recirculation on combustion and emission of an RCCI engine, fueled with diesel and CNG was investigated. The investigated engine is a single-cylinder engine with diesel direct injection to the combustion chamber as high-reactivity fuel and a port fuel injection of CNG fuel as low-reactivity fuel. The start of injection, the injection shape, and the injection duration of both injectors are controlled by the developed ECU. Since the engine tested has good stability in the premix ratio of 60% and is capable of operating with high EGR percentage, it was selected for investigation. The results of this study show that with an increase of the exhaust gas recirculation rate from 0 to 34%, the amount of IMEP and thermal efficiency decrease by about 18%. As the EGR increases, the start, middle, and end of the combustion are delayed due to the decrease in oxygen content inside the combustion chamber. With the increase of EGR, the temperature of the combustion chamber decreased so that increasing CO and UHC production, showing an increase of 86 and 300%, respectively, while NOx decreases by 350%.
Farid Haghighat Shoar, Bahman Najafi,
Volume 21, Issue 3 (2-2021)
Abstract
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 B
5 biodiesel in diesel fuel mixtures is common and most countries have planned to use B
20 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 B
20 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 CO
2 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.
Mohsen Bashi, Mohsen Ghazikhani,
Volume 22, Issue 2 (1-2022)
Abstract
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).
Seyed Reza Mousavi, Mohammad Askari, Seyed Mohammad Reza Miri,
Volume 23, Issue 6 (5-2023)
Abstract
Fossil fuel reserves are running out and its use for energy production also affects the environment. Therefore, sustainable and clean energy sources must be produced to meet the needs. In this research, mixed fuels of methyl esters of rapeseed oil, soybean oil and palm oil were produced with diesel fuel. To achieve the advantages of palm oil biodiesel (high calorific value) and soybean and rapeseed oil biodiesel (low kinematic viscosity), different biodiesel mixtures (BS10, BS20, BR10, BR20, BP10, BP20, BRSP10 and BRSP20) were used to evaluate their effect on engine performance and greenhouse gas emissions at speeds of 1800 to 2700 rpm with a step of 300 rpm under full load conditions. The physical and chemical properties of all fuel mixtures were measured according to the ASTM D6751 standard. An air-cooled, 4-stroke, naturally aspirated single-cylinder diesel engine was used for different mixture testing. The experimental results showed that in all the combined fuels, the values of power and specific fuel consumption increase with increasing engine speed, while the torque decreases. Also, the number of pollutants increases with the increment of engine speed. Based on the results, BP20 mixture fuel can be used as an alternative in diesel engines without any engine modification.
Ashkan Sadeghi Ahangar, Amir Hossein Shamekhi,
Volume 24, Issue 12 (11-2024)
Abstract
This study investigates the effects of water-methanol mixture injection on the performance and emissions of the EF7 TC engine. Using GT Power software, the engine was first simulated and validated with gasoline fuel. Subsequently, a nozzle was used to introduce the water-methanol mixture, simulated in three different ratios: 50% water-50% methanol, 25% water-75% methanol, and 75% water-25% methanol. The novelty of this research lies in the simulation of this injection process to enhance combustion quality. Results indicate significant temperature reductions at various points, alongside notable changes in knock characteristics and emissions, including nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO₂), and nitrogen monoxide (NO).
