Papers by Keyword: Combustion

Abstract: The aim of this work is to examine the performance, combustion as well as emission characteristics of diesel engine performed for various mixtures of methane-enriched biogas (95% CH₄). Experiments were performed on a single cylinder, four-stroke constant speed, direct injection, water-cooled diesel engine. The engine is operated by means of dual fuel mode using diesel and different mixtures of methane-enriched biogas (BG) like BG10, BG20, BG30, and BG40 mixed with the air (i.e. BG40-40% of CH₄ by volume respectively) for different loads and at injection timing of 27.5° before top dead centre (bTDC). The performance, combustion and emission characteristics of the engine operated by dual fuel mode were experimentally analyzed, and compared with respect to diesel mode. The experimental result reveals that better performance and lower emissions were observed for BG40 compared to other mixtures. The brake thermal efficiency of BG40 is lower by 2.43% compared to diesel at full load. The cylinder peak pressure for dual fuel mode is higher by 6.55% when compared with diesel mode. NOx emission reduced by 2.6 % and CO emission increased by 3.3% compared to diesel at full load respectively. Keywords: Biogas, Energy, Combustion, Emission, Injection timing, dual fuel mode

Abstract: Efficient use of depleting petroleum fuel and stringent environmental policy drives the researchers to unveil the alternative fuel to run the diesel engines. Biodiesel has come out to be the immediate alternative due to its properties, but the problem of higher NOx emission is still an issue. With the development of nanotechnology, efforts are made to explore the performance of different nanoadditives with diesel-biodiesel blends. In line with this, it is intended to find the performance of a diesel engine fuelled with diesel-biodiesel blend (B20) with iron nanoparticle (INP). Tranesterified soapnut oil biodiesel is used in the blend. Results reveal that dosing level of 75 ppm of INP with B20 results in an increase in BTE by 3.2% and reduce SFC by 4% than that of diesel. This may be due to additional surface energy provided by the INP which lead to a reduction of ignition delay and thus the better combustion. While the emission of HC and NO_x is found to reduce by 7.3% and 8.5%, respectively.

Abstract: The rapid rise in energy requirement and problem regarding atmosphere pollutions, renewable biofuels are the better alternative choice for the internal combustion engine to partially or totally replace the pollutant petroleum fuel. In the present work, thumba (Citrullus colocynthis) non-edible vegetable oil is used for the production of biodiesel and examine its possibility as diesel engine fuel. Transesterification process is used to produce biodiesel from thumba non-edible vegetable oil. Thumba biodiesel (TBD) is used to prepare five different volume concentration (blends) with neat diesel (D100), such as TBD5, TBD15, TBD25, TBD35 and TBD45 to run a single cylinder diesel engine. The diesel engine's combustion parameter such as in-cylinder pressure, rate of pressure rise, net heat release rate, cumulative heat release, mean gas temperature, and mass fraction burnt analyzed through graphs and compared all thumba biodiesel blends result with neat diesel fuel. The mass fraction burnt start earlier for thumba biodiesel blends compared to diesel fuel because of less ignition delay while peak in-cylinder pressure, maximum rate of pressure rise, maximum net heat release rate, maximum cumulative heat release, and maximum mean gas temperature has found decreased results up to 1.93%, 5.53%, 4.11%, 4.65%, and 1.73% respectively for thumba biodiesel.

Abstract: In this work, the ignition and combustion characteristics of mixed rice straw and sewage sludge pellets in air atmosphere were investigated using a plasma combustion system. One common pellet shape (solid spherical pellet) and another new shape (hollow spherical) are used in this study. High-speed camera was used to record and observe ignition and combustion process of pellets. In case of hollow pellets, the shape and distribution of flame are found to be better compared to solid pellets. Also, it is clear that the values of volatile combustion times in case of hollow pellets are low compared to solid pellets. The overall heat transfer enhanced in case of hollow pellet due to the large area subjected to hot gases and the high surface to volume ratio. Hollow pellet consumed less time for internal ignition and volatiles char combustion compared to solid pellet. Volatiles and char combustion lasted for 63.05 and 61 s, respectively for hollow pellet while these values were found to be 72.8 and 83 s, respectively for solid pellet.

Abstract: The domestic anthracite is the most important fuel for Vietnamese thermal power plants. Due to high carbon percentage and low volatile matter it is difficult to ignite and to burn out the domestic anthracite. The rest carbon in ash is very high, in some cases approximately 40 %. To solve this problem some methods have been tested. In this research a mixture of anthracite and coal gas is considered. The purpose of the research is to describe a combustion behavior in a boiler, namely temperature, carbon and volatile matter distributions using CFD. The mixture consists of 4.3 % coal gas and 95.7% anthracite in mass. The boiler is divided into two combustion zones, the main zone 1 and the zone 2, to extend combustion area and through it to improve burning conditions for anthracite particles and to reduce NOx formation. All the anthracite mass and 1/3 coal gas volume are delivered into the zone 1, the rest of coal gas is into the zone 2. The CFD simulation is used for the zone 1. The simulation findings show that anthracite particles are ignited earlier, the mixture combustion develops in a larger space with higher temperatures, the carbon burning rate is remarkably improved due to coal gas. That means the domestic anthracite can be used better in boilers if some coal gas, 4 or 5 %, is mixed and the obtained ash can have lower unburned carbon, below 10%, and be more friendly for the environment.

Abstract: The reheat furnace process step has a profound effect on the TMCP performance, final hot rolled steel quality and mechanical property consistency during the production of hot rolled steels. The uniformity of heating applied across the entire width and length of the slab or billet is critical in the achievement of customer properties regardless of the chemistry. The resultant ferrite grain size in the final hot rolled product is significantly governed by the initial prior austenite grain size. Numerous reheat furnace process metallurgy and combustion parameters in actual operation affect mill productivity, microstructure, austenite grain size, scrap rate and diverts. This reheating step in the steelmaking process often receives low priority in the evaluation of product quality and mechanical property performance, especially the toughness through the plate thickness. Heat transfer conditions of radiation, convection and conduction affect furnace heating efficiency. In laboratory studies, the furnace heating step is typically quite uniform resulting in a homogeneous and fine prior austenite grain size. During production, it is much more difficult to control the uniformity of heating and heat transfer consistency along the entire length and through the thickness of the work piece. The furnace conditions are correlated to product quality via furnace process variables such as the air to gas ratio, furnace burner condition, furnace pressure, energy efficiency, adiabatic flame temperature (AFT) and furnace refractory condition. Operational practice recommendations are presented to minimize inhomogeneous heating which results in inferior product quality, hot rolling model anomalies and toughness variations in the through-thickness-direction.

Abstract: An experimental investigation was carried out of coal-water fuel (CWF) drops ignition and combustion. CWF examples were produced by using of coal of different metamorphic stages, including brown coal, flame coal, and gas coal. The processes of combustion and ignition of CWF took place in the air. Time-temperature dependences of ignition and combustion processes were obtained; basic stages of CWF combustion were established and investigated; combustion completeness was defined and ash residue structure and properties were investigated during the experimental research. Influence of the working medium temperature on the time duration of each burning stage was defined. Generalization of results was carried out. It is shown, that duration of the volatiles combustion stage doesn’t depend on the medium temperature and stay constant for each of coal grade. Time interval before CWF ignition can be described with power-type dependence, which is identical for all metamorphic stages of coal. The maximum temperature of CWF combustion grows linearly in respect to the medium temperature in the oven.

Abstract: The paper presents a numerical simulation of combustion of a metallized composite solid propellant with additives of micron-and nanosized aluminum particles. The model takes into account the thermal effect of decomposition of the condensed phase, convection, diffusion, the exothermic chemical reaction in the gas phase, heating and combustion of aluminum particles in the gas flow, the flow of combustion products, the particle velocity lag relative to the gas. The effect of the Al particle size and mass fraction, emitted from the burning surface, on the burning rate is also taken into consideration.

Abstract: Nowadays, plant biomaterials have been used in several types of industries for related purposes for example energy and electricity production, as our world is facing energy shortage problems. In this paper, the combustion behavior of a typical plant biomaterial, corn cob, was investigated using TG-DSC technique. Combustion experiments were conducted from room temperature to 900 °C at three heating rates of 10, 20 and 30°C/min in air atmosphere. It is observed that the process can be divided into three stages: dehydration (25°C-150°C), pyrolysis (150°C-380°C) and combustion (above 380°C). Besides, ignition and burnout temperature were investigated based on DSC profiles. Finally, two model-free methods (FWO and KAS) were adopted to perform the kinetic analysis for combustion reaction process. It is found that activation energies values against conversion rate present a rising trend (from about 172.40 KJ/mol to 326.95 KJ/mol) in the pyrolysis stage, while an opposite tendency was observed in the combustion stage (from about 365.55 KJ/mol to 202.86 KJ/mol), indicating that corn cob combustion is a complex process and relatively complex reaction schemes should be adopted to describe its combustion. It is anticipated that our current work could be helpful in providing reference to the design of energy conversion facilitates.

Abstract: Nowadays, increase in numbers of automotive results in a large amount of used engine oil, which is a waste and has a tremendous effect on the environment. Used engine oil, however, has a relatively high calorific value so that it is interesting to be used this waste as a renewable fuel for heat generation. The present experimental study on used engine oil combustion in a vertical tube burner, therefore, had been conducted. The two-stage combustion was divided by the air supply to the burner into two levels and the air flow rate of both levels can be adjusted. The fuel in the first stage was heated and vaporized by the incompletes combustion. The exhaust gases and residual fuel vapor from the first stage were then flow to the second combustion stage and the complete combustion was achieved. The combustion temperatures along the length of the burner in both of the single and the two stage combustion had been measured and compared. Amount of exhaust gases at the exit of the burner was also monitored. The results revealed that the temperature profile along the length of the burner in the combustion zone of the two-stage burner was higher than those in the single-stage type as a result of a better mixing of air and fuel. In addition, it also found that an increase in a distance of air supply location between two stages resulted in an increase of the emission.