Increase In Combustion Temperature Research Articles

Influence of small calcium additives on the structure and properties of ML5 (AZ91) alloy

The influence of calcium additives (from 0,1 to 1,0 wt.%) on the phase composition and the solidus temperature of ML5 magnesium alloy was studied. During the alloy crystallization in the presence of aluminum, calcium forms an intermetallic compound with a variable composition containing Al (53,4–57,4 %), Ca (42,6–42,8 %) and Mg (0,002–3,8 %). As the temperature decreases, this compound degenerates to Al 2 Ca combination. The impact of calcium on the number of Mg 17 Al 12 and Al 2 Ca phases as well as its distribution in the structure of the cast and heat-treated ML5 alloy was analyzed. By means of the electron microprobe analysis, it was found that calcium and aluminum were concentrated along the boundaries of the solid magnesium solution. It was shown that satisfactory mechanical properties of magnesium alloys containing calcium could only be acquired by their smelting and casting according to the process preventing metal contamination with rough inclusions. It was found that small calcium additions (up to 1 wt.%) increased combustion temperature and reduced the oxidation of the alloy at elevated temperatures (up to 715 °C). The effect of sulfur hexafluoride on the loss of calcium in flux-free melting was found.

Experimental research on the NOx evolvement of pulverized coal combusted in CO2, Ar and N2 atmospheres

A fixed-bed reaction platform was employed to study the influences of combustion atmospheres (O2/N2, O2/Ar and O2/CO2), oxygen concentrations, combustion temperatures, and particle diameters on the combustion behavior of Shen Hua (SH) bituminous. It was found that in O2/CO2, the fuel-NO yield per O2 consumption (YNO) is the lowest among the three atmospheres. All the tests in O2/CO2 show that YNO decreases with increasing combustion temperature. On the basis of the tests in N2 and Ar atmospheres at high temperature (1873K), the inhibition of fuel-NO by thermal-NO was revealed quantitatively. As the combustion temperature increases, the pulverized coal ignites earlier and the combustion durations get shorter. When at a low temperature (1273K), the combustion duration in the CO2 atmosphere is twice or three times longer than that in N2 and Ar atmospheres. When the temperature is above 1573K, the combustion durations in CO2 atmosphere are nearly the same as that of the other two atmospheres, indicating the high temperature would guarantee similar combustion characteristics between O2/CO2 and O2/N2. Furthermore, according to all the fuel-NO cumulative curves of the reaction processes, a cumulative percentage mathematical model (CPM) describing the fuel-NO release process in context of oxygen concentration, temperature, burnout rate, and atmosphere was proposed for comprehensive understanding of experimental results. As the combustion temperature and oxygen concentration increases, larger portion of fuel-NO is formed prior to coal burnout due to the enhanced char gasification and pyrolysis at high temperature. This phenomenon is enhanced in CO2 atmosphere, which further facilitates the reduction of fuel-NO.

Effects of oxygen enriched combustion on pollution and performance characteristics of a diesel engine

Oxygen enriched combustion is one of the attractive combustion technologies to control pollution and improve combustion in diesel engines. An experimental test was conducted on a single cylinder direct injection diesel engine to study the impact of oxygen enrichment on pollution and performance parameters by increasing the oxygen concentration of intake air from 21 to 27% by volume. The tests results show that the combustion process was improved as there is an increase in thermal efficiency of 4 to 8 percent and decrease in brake specific fuel consumption of 5 to 12 percent. There is also a substantial decrease in unburned hydro carbon, carbon mono-oxide and smoke density levels to the maximum of 40, 55 and 60 percent respectively. However, there is a considerable increase in nitrogen oxide emissions due to increased combustion temperature and extra oxygen available which needs to be addressed.

A comparative study on the first and second law analysis and performance characteristics of a spark ignition engine using either natural gas or gasoline

Abstract In this study, the effect of fuel type; gasoline or natural gas on the energy and exergy balance as well as the performance of spark ignition engine was experimentally investigated. The experiments were conducted using a four cylinder, naturally aspirated CNG–gasoline bi-fuel engine at wide open throttle (WOT) operating condition. The results showed that when engine was fed with gasoline, the output power was higher than that of gaseous fuel by 4.2 kW on average throughout the engine speed range. Thermal efficiency of the engine with natural gas was higher than that of the gasoline by approximately 5.4% throughout the engine speed range. In addition, CNG fuel showed higher exergetic efficiency than gasoline, and based on these results second law efficiency of CNG engine was higher than that of gasoline engine by 3.18% on average. This was largely due to combustion temperature increase in CNG case. For all operating points, the percentage of energy and exergy transfer through exhaust gases and the cooling system in gasoline are lower than CNG. However the destructed exergy of gasoline was higher than CNG by about 5.8%, averagely.

An experimental and thermodynamic equilibrium investigation of the Pb, Zn, Cr, Cu, Mn and Ni partitioning during sewage sludge incineration

The effects of different chlorides and operational conditions on the distribution and speciation of six heavy metals (Pb, Zn, Cr, Cu, Mn and Ni) during sludge incineration were investigated using a simulated laboratory tubular-furnace reactor. A thermodynamic equilibrium investigation using the FactSage software was performed to compare the experimental results. The results indicate that the volatility of the target metals was enhanced as the chlorine concentration increased. Inorganic-Cl influenced the volatilization of heavy metals in the order of Pb>Zn>Cr>Cu>Mn>Ni. However, the effects of organic-Cl on the volatility of Mn, Pb and Cu were greater than the effects on Zn, Cr and Ni. With increasing combustion temperature, the presence of organic-Cl (PVC) and inorganic-Cl (NaCl) improved the transfer of Pb and Zn from bottom ash to fly ash or fuse gas. However, the presence of chloride had no obvious influence on Mn, Cu and Ni. Increased retention time could increase the volatilization rate of heavy metals; however, this effect was insignificant. During the incineration process, Pb readily formed PbSiO4 and remained in the bottom ash. Different Pb compounds, primarily the volatile PbCl2, were found in the gas phase after the addition of NaCl; the dominant Pb compounds in the gas phase after the addition of PVC were PbCl2, Pb(ClO4)2 and PbCl2O4.

Fast Prepared Ni-Al2O3 Nanocomposite Through Solution Combustion Synthesis

Solution combustion synthesis (SCS) is a well-known method for fabrication of different materials such as oxides and composite materials in an extensive range. In this investigation, solution combustion synthesis is used for fabrication of Ni-10 wt% Al2O3 nanocomposite. Nickel and aluminum nitrates, urea, and distilled water are used as oxidizer, fuel, and solvent, respectively. The results show that if the fuel to oxidizer ratio exceeds the stoichiometric ratio, the combustion temperature increases. However, introduction of graphite to the solution could conduce to the reduction of the combustion temperature. With the addition of an auxiliary material, graphite, so a nickel oxidation is postponed, Ni-Al2O3 nanocomposite is produced only in one step.

Release and transformation of sodium during combustion of Zhundong coals

Zhundong coalfield is one of the super-huge coalfields newly discovered in Xinjiang Autonomous Region of China. Zhundong coal is characterized by high content of sodium. This study deals with the release and transformation of sodium during combustion of two Zhundong coals. The volatilization of sodium and evolution of its occurrence modes in resultant ash were investigated in a laboratory-scale reactor. Experimental results show that sodium is the principal alkali metal and water-soluble sodium is the predominant chemical form in Zhundong coals. Combustion temperature has a pronounced effect on the release and transformation of sodium. The fraction of water-soluble sodium in residual ash decreases significantly and more HCl-soluble form is generated with the increase of combustion temperature. The tendency of ash deposition during coal combustion is closely related to occurrence mode of alkali metals. In addition, halite (NaCl) is clearly present in ash of Zijin coal at low temperature, while most sodium in form of NaCl is released into gas phase and the remainder is transformed into aluminosilicates with increasing temperature. Chlorine has a significant influence on transformation of sodium and NaCl(g) is the main form of sodium volatized from coal between 600 and 800 °C.

A dynamic smoke generation and nose-only inhalation exposure system for rats: preliminary results from studies of selected transportation materials

Context: Smoke inhalation injury is the main cause of fatalities for fire victims. Understanding in the pathophysiology of the injury has not been fully explored in recent years. To further explore the pathophysiological mechanism, a dynamic and controllable animal model is necessary.Objective: To develop a rat model of smoke inhalation injury to simulate human victims in air-restricted vehicle cabin fires.Materials and methods: Smoke concentration, including CO, O2, VOCs and smoke temperature under different combustion conditions, were detected. Levels of COHb, respiratory function, lung wet-to-dry weight ratio and protein concentration in BALF and blood were measured. Pathological evaluations of lung in tissues were conducted at 1, 6, 24 and 48 h post-exposure.Results: Smoke concentration rose with the increase of combustion temperature and decrease of oxygen flow. Further, 215 kinds of VOCs in the smoke were detected, and the concentrations of benzene, methylbenzene, ethylbenzene, dimethylbenzene, phenylethylene and trimethylbenzene was 32.93, 402.06, 764.03, 113.73, 1006.61 and 89.28 mg/m3, respectively. Significant hypoxemia and CO poisoning occurred in rats. The FCOHb after exposure for 14 min immediately rose to (44.2 ± 12.3) % and then gradually decrease to a normal level at 300 min post-exposure. At 24 h post-exposure, Penh increased significantly (p < 0.05), and high pulmonary vascular permeability and significant lung edema (p < 0.05) were observed in the smoke inhalation group.Discussion and conclusion: In summary, the novel rat model of smoke inhalation injury system used in the study is dynamic and controllable, and appropriate for use in smoke inhalation injury studies of air-restricted cabins in vehicles.

Reduction of fine particles exhausted from small-size combustor using agricultural waste residue by controlling burning temperatures

About 3.9 million tons of agricultural residue waste biomass such as rice husk and straw are stably produced from rice each year in Japan. It is reported that vapor pollutants and particles emitted from the burning of agricultural residue waste biomass such as waste rice husk and straw have serious infl uences on visibility, human health, and global climate. Therefore, it is necessary to utilize waste rice husk and straw effectively to reduce air pollution. In recent years, there has been an increasing demand for the effective utilization of waste agricultural residue biomass instead of fossil fuel in combustors for farming such as greenhouses heating during the winter season. However, there is a lack of regulations or laws to control air pollution from these small-size combustors in Japan. So far, small-size combustors have been characterized by their structural simplicity and low cost. Therefore, it is necessary to evaluate and control the emission of air pollutants such as fiparticles (i.e. PM 2.5 ‐ particles below 2.5 µm in aerodynamic diameter) due to the poor combustion performance of small-size combustors. In this study, it was investigated whether it would be possible to utilize biomass fuel selected from waste rice husk and straw of agricultural residue waste biomass based on the laboratory combustion experiments. The emission behavior of harmful suspended particulate matter produced from burning rice husk and straw was evaluated by measuring carbonaceous and ionic composition of PM 2.5 in the exhaust gases. From the analytical results, it was found that particulate mass concentrations reduced substantially at high-temperature combustion. However, ionic compositions were increased with the increase in combustion temperature. It can be suggested that stable combustion should be performed under suitable conditions to control air pollutants emitted from biomass fuel, although small-size combustors are still not regulated to control PM 2.5 emission.

Influence of increasing combustion temperature on the AMS 14C dating of modern crop phytoliths.

Several attempts have been made to directly date phytoliths, but most 14C results are not consistent with other independent chronologies. Due to the limited dataset, there is not a clear explanation for these discrepancies. Herein, we report the 14C ages of phytolith-occluded carbon (PhytOC) from contemporary rice and millet crops that were combusted at different temperatures to investigate the relationship between the combustion temperature and resulting 14C age. Our results show that the 14C age of PhytOC increases directly with combustion temperature (up to 1100°C) and results in age overestimations of hundreds of years. Considerably older ages are observed at higher temperatures, suggesting that it may be possible to distinguish between two fractions of organic carbon in phytoliths: labile and recalcitrant carbon. These findings challenge the assumption that PhytOC is homogeneous, an assumption made by those who have previously attempted to directly date phytoliths using 14C.

Thermogravimetric Analysis of Coal Char Combustion Kinetics

Four chars prepared from pulverized coals were subjected to non-isothermal and isothermal combustion tests in a thermogravimetric analysis (TGA) device. Three different test methods, i.e., non-isothermal single heating rate (A), non-isothermal multiple heating rate (B), and isothermal test (C), were conducted to calculate the kinetic parameters of combustion of coal char. The results show that the combustion characteristics of bituminous coal char is better than that of anthracite char, and both increase of heating rate and increase of combustion temperature can obviously improve combustion characteristics of coal char. Activation energies of coal char combustion calculated by different methods are different, with activation energies calculated by methods A, B and C in the range of 103. 12–153. 77, 93. 87–119. 26, and 46. 48–76. 68 kJ/mol, respectively. By using different methods, activation energy of anthracite char is always higher than that of bituminous coal char. In non-isothermal tests, with increase of combustion temperature, the combustion process changed from kinetic control to diffusion control. For isothermal combustion, the combustion process was kinetically controlled at temperature lower than 580 °C for bituminous coal char and at temperature lower than 630 °C for anthracite char.

Effects of alumina nanoparticles in waste chicken fat biodiesel on the operating characteristics of a compression ignition engine

An experimental investigation was carried out to study the performance, emissions and combustion characteristics of a compression ignition (CI) engine fuelled with waste chicken fat biodiesel with alumina nanoparticles as an additive. The disposal of waste chicken creates environmental pollution, hence it is decided to extract oil from the waste chicken fat and produce biodiesel through transesterification process. As the chicken fat contains 13.6 % free fatty acid (FFA), a pre-treatment process was carried out using Ferric sulphate as a catalyst in order to reduce the FFA content less than 1 % to prevent soap formation during the process. Potassium hydroxide was used as catalysts for the effective conversion of triglycerides of waste chicken fat into methyl ester. Various diesel–biodiesel–alumina blends were prepared by varying the biodiesel proportions of 20 and 40 % by volume and 25 and 50 ppm of alumina nanoparticles to study its operating characteristics on a computerized single cylinder, constant speed CI engine. Aluminium oxide (Al2O3) nanoparticles were used as fuel born catalyst in order to enhance the combustion characteristics and reduce the harmful emissions. The engine test results showed less improvement in brake thermal efficiency and significant reduction on the hydrocarbons and carbon monoxide emissions. However, higher nitrogen oxide emissions were recorded due to the increase in combustion temperature as the nanoparticles enhanced the surface area to volume ratio which improves the thermal conductivity of the fuel blend resulted in improved combustion. Smoke reduction of 52.8 % was observed in B40 fuel blend with 50 ppm alumina nanoparticles under full load conditions.

A study on the spray and engine combustion characteristics of diesel–dimethyl ether fuel blends

The purpose of this study was to compare the spray characteristics, the combustion characteristics and the emissions (nitrogen oxides, carbon monoxide, hydrocarbon and smoke) of typical fuels (100% diesel and 100% dimethyl ether) and diesel–dimethyl ether fuel blends in a constant-volume chamber and a single-cylinder direct-injection diesel engine. The spray characteristics were investigated by varying the ambient pressure and the fuel injection pressure using a common-rail fuel injection system with various fuel mixture ratios. The spray characteristic research parameters were the spray shape, the penetration length and the spray angle at the seven-hole injector. Common types of injector were used (Bosch). Two types of fuel blended by mass fraction were employed. Typical fuels (100% diesel and 100% dimethyl ether) and fuel blends with diesel:dimethyl ether mixture ratios of 95:5 and 90:10 were used. The injection pressure was fixed at 70 MPa while the ambient pressure was varied (0 MPa, 2.5 MPa and 5 MPa). The combustion experiments were conducted in a single-cylinder engine equipped with a common rail. The injection pressure was 700 bar at 1200 r/min. The amount of injected fuel was adjusted to obtain a fixed input calorific value of 972.2 J/cycle in order to make a comparison between the fuel types. The results showed that the injection quantity was greater with diesel fuel but not for dimethyl ether fuel and for the fuel blend with the higher mixing ratio. The spray penetration length increased with increasing ambient pressure for diesel but decreased for dimethyl ether with a larger spray angle. The ignition delay and the heat release rate decreased with increasing dimethyl ether which led to a higher indicated mean effective pressure and higher thermal efficiency because there was less negative work in the expansion. The total hydrocarbon emissions and the carbon monoxide emissions decreased with increasing dimethyl ether, but the nitrogen oxide emissions generated were greater owing to the increased combustion temperature.

Environmental analysis of present and future fuels in 2D simple model marine gas tubines

Increased worldwide concerns about fossil fuel costs and effects on the environment lead many governments and scientific societies to consider the hydrogen as the fuel of the future. Many researches have been made to assess the suitability of using the hydrogen gas as fuel for internal combustion engines and gas turbines; this suitability was assessed from several viewpoints including the combustion characteristics, the fuel production and storage and also the thermodynamic cycle changes with the application of hydrogen instead of ordinary fossil fuels. This paper introduces the basic environmental differences happening when changing the fuel of a marine gas turbine from marine diesel fuel to gaseous hydrogen for the same power output. Environmentally, the hydrogen is the best when the CO 2 emissions are considered, zero carbon dioxide emissions can be theoretically attained. But when the NO x emissions are considered, the hydrogen is not the best based on the unit heat input. The hydrogen produces 270% more NO x than the diesel case without any control measures. This is primarily due to the increased air flow rate bringing more nitrogen into the combustion chamber and the increased combustion temperature (10% more than the diesel case). Efficient and of course expensive NO x control measures are a must to control these emissions levels.

Preparation and Microwave Absorption Property of Nickel Spinel Ferrite

NiFe2O4 ferrite was synthesized by sol-gel method. Its structural characteristics, morphology, electromagnetic and microwave absorption properties were analyzed by X-ray diffraction, scanning electron microscope and network analyzer, and analyzed the influence of the combustion temperature and citric acid. The results indicated that the particle size be enlarged with an increased combustion temperature and be diminished first, then increased with the increased of citric acid, and the best ratio of citric acid with metal ions for nCA: nFe: nNi = 4:2:1. Its microwave absorbing property is increased with the increased combustion temperature. Its complex permittivity imaginary part first decreases with temperature increases and then increases, the imaginary part of complex permeability with increasing temperature increases, indicating that the increase of calcination temperature, help to improve the sample microwave absorbing properties.

Effect of Injection Timing on Combustion Characteristics of a DI Diesel Engine Fuelled with &lt;i&gt;Pistacia chinensis&lt;/i&gt; Bunge Seed Biodiesel

In this study, the effect of injection timing on combustion characteristics of a direct injection, electronically controlled, high pressure, common rail, turbocharged and intercooled engine fuelled with different pistacia chinensis bunge seed biodiesel/diesel blends has been experimentally investigated. The results indicated that brake specific fuel consumption reduces with the increasing of fuel injection advance angle and enhances with the increasing of biodiesel content in the blends. The peak of cylinder pressure and maximum combustion temperature increase evidently with the increment of fuel injection advance angle. However, the combustion of biodiesel blends starts earlier than diesel at the same fuel injection advance angle. At both conditions, the combustion duration and the peak of heat release rate are insensitive to the changing of injection timing.

Towards reconstruction of past fire regimes from geochemical analysis of charcoal

Production of charcoal has accompanied human life from the beginning. We aimed at evaluating the degree to which the chemical signatures of charcoal may serve as a fingerprint for burning conditions. After a compilation of fire literature we differentiated three typical fire regimes [grass and forest ground (285±143°C), shrub (503±211°C) and domestic fires (797±165°C)] and three main factors impacting on charcoal formation: charring duration, temperature and fuel. For fingerprint calibration and validation, typical fuels of prehistoric burning events (wood and grass) were charred under laboratory conditions (300–700°C; varying duration) and compared with residues from natural fires in SE Europe. Analysis comprised assessment of benzene polycarboxylic acids (BPCAs), organic carbon (Corg) content, nitrogen content, oxygen index (OI, CO2/Corg) and hydrogen index (HI, HC/Corg), temperature of maximum heating (Tmax) and mid-infrared spectroscopy (MIRS). All parameters including mass loss increased with increasing combustion temperature, but were unaffected by charring duration. Grass charcoal had consistently lower Corg content and HI than wood, but values showed a bias towards the natural charcoals, probably because the latter contained higher amounts of mineral matter or were combusted under greater O2 supply. Nevertheless, natural charcoals could be differentiated into forest ground fires (B5CA/B6CA 1.3–1.9; OI>20; intense CH2 stretching, Tmax<488°C) and grass fires (B5CA/B6CA 0.8–1.4; OI>20; weak CH2 stretching, Tmax<425°C), whereas domestic fires revealed B5CA/B6CA values <0.8, OI values <20 and little MIRS absorbance. In summary, it appears possible to reconstruct fire regimes from the temperature sensitivity of BPCA patterns, Tmax, OI and aromatic and aliphatic MIRS signals, whereas assignment of fuel source was less reliable.

Application of Thermal Barrier Coatings in Diesel Engines: a Review

A review of research on low heat rejection engines, to incorporate various systems of ceramic materials in intermittent combustion engines, and on the use of ceramics in these engines is presented. The reduction of heat loss from the combustion chamber of diesel engines improves fuel efficiency only by 3 or 4 per cent. Some other gains may be possible from a smaller cooling system, recovery of exhaust energy, and improvements in aerodynamics. The use of thermal barrier coatings (TBCs) to increase the combustion temperature in diesel engines has been pursued for over 20 years. Increased combustion temperature can increase the efficiency of the engine, decrease the CO and (possibly) the NOx emission rate. However, TBCs have not yet met with wide success in diesel engine applications because of various problems associated with the thermomechanical properties of the coating materials. Although, the in-cylinder temperatures that can be achieved by the application of ceramic coatings can be as high as 850-9000C compared to current temperatures of 650-7000C. The increase in the in-cylinder temperatures helped in better release of energy in the case of biodiesel fuels thereby reducing emissions at, almost the same performance as the diesel fuel. The purpose of this paper is to explain the effect of insulation on engine performance, heat transfer characteristics, combustion and emission characteristics. Many researchers have carried out a large number of studieson Low Heat Rejection Engine (LHRE) concept. Some of them are experimental work and many are theoretical studies. In the case of LHR engines almost all theoretical studies predict improved performance but many experimental studies show different picture. This paper analyses the reason for this deviation. The operating conditions, under which the experimental and simulation studies are carried out, have been clearly discussed. The factors, which affect thermal efficiency, combustion, and exhaust emissions in LHR engine, are deduced and their influences discussed.

Role of fuel/oxidizer ratio on the synthesis conditions of Cu–Al2O3 nanocomposite prepared through solution combustion synthesis

The role of fuel/oxidizer ratio in the synthesis conditions of Cu–Al2O3 nanocomposite, which was prepared through solution combustion synthesis, method was investigated. For this purpose, copper and aluminum nitrates as well as urea were used as oxidizer and fuel, respectively. The fuel/oxidizer (F/O) ratios were selected from the range of 0.9–1.75. The products were analyzed using X-ray diffraction, SEM and TEM techniques. During the process the temperature was recorded as a function of time. The results showed that by increasing the F/O ratio up to the stoichiometric amount, the combustion temperature increases. Further increment of F/O ratio resulted in a decrease in the combustion temperature. Microscopic evaluations, using SEM and TEM, proved feasibility of the production of Cu–Al2O3 through this method.

Simulations of Multiphase Particle Deposition on a Showerhead With Staggered Film-Cooling Holes

The demand for cleaner, more efficient energy has driven the motivation for improving the performance standards for gas turbines. Increasing the combustion temperature is one way to get the best possible performance from a gas turbine. One problem associated with increased combustion temperatures is that particles ingested in the fuel and air become more prone to deposition with an increase in turbine inlet temperature. Deposition on aero-engine turbine components caused by sand particle ingestion can impair turbine cooling methods and lead to reduced component life. It is necessary to understand the extent to which particle deposition affects turbine cooling in the leading edge region of the nozzle guide vane where intricate showerhead cooling geometries are utilized. For the current study, wax was used to dynamically simulate multiphase particle deposition on a large scale showerhead cooling geometry. The effects of deposition development, coolant blowing ratio, and particle temperature were tested. Infrared thermography was used to quantify the effects of deposition on cooling effectiveness. Although deposition decreased with an increase in coolant blowing ratio, results showed that reductions in cooling effectiveness caused by deposition increased with an increase in blowing ratio. Results also showed that effectiveness reduction increased with an increase in particle temperature. Reductions in cooling effectiveness reached as high as 36% at M = 1.0.