Effect of Nozzle Inclination Angle on Fuel-Air Mixing and Combustion in a Heavy Fuel Engine

Heavy-fuel engines are widely used in UAVs(Unmanned Autonomous Vehicles)because of their reliability and high-power density.In this study,a combustion model for an in-cylinder direct injection engine has been imple-mented using the AVL FIRE software.The effects of the angle of nozzle inclination on fuel evaporation,mixture distribution,and combustion in the engine cylinder have been systematically studied at 5500 r/min and consider-ing full load cruise conditions.According to the results,as the angle of nozzle inclination increases,the maximum combustion explosion pressure in the cylinderfirst increases and then it decreases.When the angle of nozzle incli-nation is less than 45°,the quality of the mixture in the cylinder and the combustion performance can be improved by increasing the angle.When the angle of nozzle inclination is greater than 45°,however,the mixture unevenness increases slightly with the angle,leading to a deterioration of the combustion performances.When the angle of nozzle inclination is between 35°and 55°,the overall combustion performance of the engine is rela-tively good.When the angle of nozzle inclination is 45°,the combustion chamber’s geometry and the cylinder’s airflow are well matched with the fuel spray,and the mixture quality is the best.Compared with 25°,the peak heat release rate increases by 20%,and the maximum combustion burst pressure increases by 5.5%.

Gas-phase oxidation of NO at high pressure relevant to sour gas compression purification process for oxy-fuel combustion flue gas

The removal of NO from oxy-fuel combustion is typically incorporated in sour gas compression purification process. This process involves the oxidation of NO to NO2 at a high pressure of 1–3 MPa, followed by absorption of NO2 by water. In this pressure range, the NO conversion rates calculated using the existing kinetic constants are often higher than those obtained experimentally. This study aimed to achieve the regression of kinetic parameters of NO oxidation based on the existing experimental results and theoretical models.Based on three existing NO oxidation mechanisms, first, the expressions for NO conversion against residence time were derived. By minimizing the mean-square errors of NO conversion ratio, the optimum kinetic rate constants were obtained. Without considering the reverse reaction for NO oxidation, similar mean-square errors for NO conversion ratio were calculated. Considering the reverse reaction for NO oxidation based on the termolecular reaction mechanism, the minimum mean-square error for NO conversion ratio was obtained. Thus, the optimum NO oxidation rate in the pressure range 0.1–3 MPa can be expressed as follows:-d[NO]/dt=d[NO2]/dt=0.0026[NO]2[O2]-0.0034[NO2]2 Detailed elementary reactions for N2/NO/NO2/O2 system were established to simulate the NO oxidation rate. A sensitivity analysis showed that the critical elementary reaction is 2 NO + O2? 2 NO2. However, the simulated NO conversions at a high pressure of 10–30 bar are still higher than the experimental values and similar to those obtained from the models without considering the reverse reaction for NO oxidation.

Improved combustion stability of biogas at different CO_(2) concentrations using inhomogeneous partially premixed stratified flames

Biogas is a renewable and clean energy source that plays an important role in the current environment of lowcarbon transition.If high-content CO_(2) in biogas can be separated,transformed,and utilized,it not only realizes high-value utilization of biogas but also promotes carbon reduction in the biogas field.To improve the combustion stability of biogas,an inhomogeneous,partially premixed stratified(IPPS)combustion model was adopted in this study.The thermal flame structure and stability were investigated for a wide range of mixture inhomogeneities,turbulence levels,CO_(2) concentrations,air-to-fuel velocity ratios,and combustion energies in a concentric flow slot burner(CFSB).A fine-wire thermocouple is used to resolve the thermal flame structure.The flame size was reduced by increasing the CO_(2) concentration and the flames became lighter blue.The flame temperature also decreased with increase in CO_(2) concentration.Flame stability was reduced by increasing the CO_(2) concentration.However,at a certain level of mixture inhomogeneity,the concentration of CO_(2) in the IPPS mode did not affect the stability.Accordingly,the IPPS mode of combustion should be suitable for the combustion and stabilization of biogas.This should support the design of highly stabilized biogas turbulent flames independent of CO_(2) concentration.The data show that the lower stability conditions are partially due to the change in fuel combustion energy,which is characterized by the Wobbe index(WI).In addition,at a certain level of mixture inhomogeneity,the effect of the WI on flame stability becomes dominant.

Combustion behavior and mechanism of molecular perovskite energetic material DAP-4-based composites with metal fuel Al

Combined with the oxidizer anions and fuel cations,molecular perovskite energetic materials show a good potential.In this work,the combustion behavior and mechanism of metal fuel aluminium(Al)with molecular perovskite energetic material(H_(2)dabco)[NH4(ClO_(4))_(3)](DAP-4)as a high-energy oxidant was investigated.The DAP-4 based composites with metal fuel Al were designed and fabricated by the different mass ratios.Results showed that DAP-4 exhibits a good oxygen-supplied capacity for enhancing the combustion performance of Al.The maximum combustion heat of DAP-4/Al-3 at the Al/O mass ratio of 38:62 is up to 10,412 J/g in the inert gas,which is higher than those of other ratios and the mixtures of other energetic materials and Al.The evolution of pressure output,pressurization rate,and flame temperature was monitored for DAP-4/Al with different mass ratios.Composites DAP-4/Al/F were characterized by burning rates.The combustion reaction mechanism of metal fuel Al with DAP-4 as a high-energy oxidant was provided.DAP-4 was ignited firstly and released acid and oxidizing gases,which corroded Al_(2)O_(3)shells on Al particle surfaces and accelerated the combustion reaction with Al to release a lot of energy.This work offered a new idea that molecular perovskite energetic materials have great potential in the high-energy Al-based solid rocket propellants.

Transformation of alkali and alkaline-earth metals during coal oxy-fuel combustion in the presence of SO_2 and H_2O

The occurrence modes of alkali and alkaline-earth metals（AAEMs） in coal relate to their release behavior and ash formation during combustion. To better understand the transformation of AAEMs,the release behavior of water-soluble,HCl-soluble,HCl-insoluble AAEMs during Shenmu coal（SM coal） oxy-fuel combustion in the presence of SO2 and H2O in a drop-tube reactor was investigated through serial dissolution using H2O and HCl solutions. The results show that the release rates of AAEMs increase with an increase in temperature under the three atmospheres studied. The high release rates of Mg and Ca from SM coal are dependent on the high content of soluble Mg and Ca in SM coal. SO2 inhibits the release rates of AAEMs,while H2O promotes them. The effects of SO2 and H2O on the Na and K species are more evident than those on Mg and Ca species. All three types of AAEMs in coal can volatilize in the gas phase during coal combustion. The W-type AAEMs release excessively,whereas the release rates of I-type AAEMs are relatively lower. Different types of AAEM may interconvert through different pathways under certain conditions. Both SO2 and H2O promote the transformation reactions. The effect of SO2 was related to sulfate formation and the promotion by H2O occurs because of a decrease in the melting point of the solid as well as the reaction of H2O.

Thermo economic evaluation of oxy fuel combustion cycle in Kazeroon power plant considering enhanced oil recovery revenues

Oxy fuel combustion and conventional cycle(currently working cycle) in Kazeroon plant are modeled using commercial thermodynamic modeling software. Economic evaluation of the two models regarding the resources of transport and injection of carbon dioxide into oil fields at Gachsaran for enhanced oil recovery in the various oil price indices is conducted and indices net present value(NPV) and internal rate of return on investment(IRR) are calculated. The results of the two models reveal that gross efficiency of the oxy fuel cycle is more than reference cycle(62% compared to 49.03%), but the net efficiency is less(41.85% compared to 47.92%) because of the high-energy consumption of the components, particularly air separation unit(ASU) in the oxy fuel cycle. In this model, pure carbon dioxide with pressure of 20×105 Pa and purity of 96.84% was captured. NOX emissions also decrease by 4289.7 tons per year due to separation of nitrogen in ASU. In this model, none of the components of oxy fuel cycle is a major engineering challenge. With increasing oil price, economic justification of oxy fuel combustion model increases. With the price of oil at $ 80 per barrel in mind and $ 31 per ton fines for emissions of carbon dioxide in the atmosphere, IRR is the same for both models.

Heat Transfer Characteristics of Boiler Convective Heating Surface Under Pressurized Oxygen-fuel Combustion Conditions

增压富氧燃烧是一项极具前景的减排CO2新技术。对增压富氧燃烧条件下,对流受热面换热特性进行研究具有重要的意义。该文以一台实际300MW等级机组煤粉锅炉为计算对象,采用维里方程及Chun等的计算方法计算确定增压富氧燃烧烟气物性,采用宽带关联k模型计算富氧燃烧烟气辐射特性。进行了常规空气燃烧以及φ（O2）：φ（CO2）=21：79、φ（O2）：φ（CO2）=30：70两种比例的0.1、0.5、1.0、1.5、6 MPa五种压力下增压富氧燃烧各对流受热面的热力计算,分析了增压富氧燃烧条件烟气压力变化对各受热面换热特性的影响。研究结果表明：随烟气压力的升高,烟气流速下降,但烟气的Re却基本保持不变,对流换热系数有所增加。增压富氧燃烧烟气的辐射换热系数比空气燃烧烟气辐射换热系数大。实现同样的换热量,增压富氧燃烧条件下（φ（O2）：φ（CO2）=21：79、φ（O2）：φ（CO2）=30：70）对流受热面所需换热面积比常规空气燃烧条件下少。

Comparisons of Fly Ash and Deposition Between Air and Oxy-Fuel Combustion in Bench-Scale Fluidized Bed with Limestone Addition

In Oxy-fuel circulating fluidized bed,the residual Ca O particles may react with high concentration of CO2 in flue gas to form bonded deposit on heat transfer surfaces in backpass when limestone is used as a sorbent to capture SO2.In this paper,experiments were designed on ash deposition in a bench-scale fluidized bed under oxy-fuel and air atmosphere. A novel ash deposit sampling probe was used to simulate the tubes of tail surfaces.The chemical composition of fly ash and ash deposit from both air-firing and oxy-fuel firing cases were analyzed by Inductively Coupled Plasma-Atomic Emission Spectrometry( ICP-AES) and Scanning Electron Microscopy( SEM),respectively. The degrees of carbonation reaction of ash deposits were measured by Thermo Gravimetric Analysis. The results showed that there are distinct differences in fly ash deposition rate between oxy-fuel and air firing cases,and oxy-fuel combustion with limestone addition can affect chemical composition of fly ash and ash deposit,especially for elements of Ca,Na,K,and S. However,the carbonation reaction degree of ash deposits is found weak,which is due to the relatively low Ca O content in ash deposit or not long enough of the sampling time.

Microstructure and Performances of Glasses Melt under Oxy-fuel Combustion

We prepared a series of glass samples under the different simulated atmosphere.Systematic evaluation about the performances of the glasses fabricated under the different simulated atmosphere indicates that the increase of the H2O：CO2 ratio under the simulated atmosphere will decrease the softening point temperature,microhardness,viscosity,and chemical resistance,while increase the thermal expansion coefficient.Through the analysis of the hydroxyl content and network structure according to the IR transmitting spectra and NMR spectra,the structural origin of the evolution of the performances for the samples fabricated under different simulated atmosphere was elucidated.According to the feedback information from the customers,despite the decrease of some performances,the glass produced under oxy-fuel combustion can also fulfill the requirements of the engineering applications.Therefore,the technique of oxy-fuel combustion is worthy to be promoted in glass industry.

Synthesis of La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_(3-δ) Powder for Solid Oxide Fuel Cell by a Nitrate-Citrate Combustion Route

A nitrate-citrate combustion route to synthesize La0.9Sr0.1Ga0.8Mg0.2O3-σ powder for solid oxide fuel cell application was presented. This route is based on the gelling of nitrate solutions by the addition of citric acid and ammonium hydroxide, followed by an intense combustion process due to an exothermic redox reaction between nitrate and citrate ions. The optimum technical parameters are that the pH value is 5, and the molar ratio of citric acid to the total metallic ion is 1.5:1. X-ray diffraction characterization of calcined gel shows that pure phase was synthesized after calcination at 1400℃for 10 h, and the TEM result shovvs the calcined powder with average particle size is about 150 nm. The grain resistance contributes to the total resistance of sintered peliet below 500℃. The conductivity of the sintered peliet at 800℃ was 0.07 S-1·cm-1 higher than the conductivity of YSZ (0.05 S-1·cm-1 at 800℃)

Effect of Atmosphere on Volatile Emission Characteristic in Oxy-Fuel Combustion

A new type of power supply which was called oxy-fuel combustion power plant was introduced to reduce greenhouse gasses emission. In this paper the volatile emission characteristic of pulverized coal is studied under air atmosphere and oxy-fuel atmosphere. Combustion experiments of Datong bituminous coal were carried out in a wire mesh reactor at heating rates of 1 K/s, 10 K/s and 1000 K/s respectively under air and O2/CO2 atmosphere conditions in order to investigate the volatile emission characteristic. The concentrations of volatile (mainly CO and CH4) emission were on-line measured by infrared gas analyzer. It was indicated that the concentrations of CO and CH4 in O2/CO2 atmosphere were higher than those in air. The direct oxidation of carbon and gasification reaction between carbon and CO2 are the main causes of the increased amount of CO. The higher concentration of CO2 also results in the increased amount of CH4 in O2/CO2 conditions.

Activation of anthracite combustion by copper acetate:mechanism,effect of particle size and introduction method

This paper addressed the efect of copper acetate on the combustion characteristics of anthracite depending on the fractional composition of fuel and additive introduction method.Anthracite was impregnated with 5 wt%of Cu(CH_(3)COO)_(2)by mechanical mixing and incipient wetness impregnation.Four anthracite samples of diferent fraction with d<0.1 mm,d=0.1-0.5 mm,d=0.5-1.0 mm,and d=1.0-2.0 mm were compared.According to EDX mapping,incipient wetness impregnation provides a higher dispersion of the additive and its uniform distribution in the sample.The ignition and combustion characteristics of the modifed anthracite samples were studied by thermal analysis and high-speed video recording of the processes in a combustion chamber(at heating medium temperature of 800℃).It was found that copper acetate increases anthracite reactivity,which was evidenced by decreased onset temperature of combustion(ΔT_(i))by 35-190℃and reduced ignition delay time(Δτ_(i))by 2.1-5.4 s.Copper acetate reduces fuel underburning(on average by 70%)in the ash residue of anthracite and decreases the amount of CO and NO_(x)in gas-phase products(on average by 18.5%and 20.8%,respectively).The mechanism for activation of anthracite combustion by copper acetate is proposed.

Numerical Investigation of Fuel Dilution Effects on the Performance of the Conventional and the Highly Preheated and Diluted Air Combustion Furnaces

This numerical study investigates the effects of using a diluted fuel （50% natural gas and 50% N2） in an industrial furnace under several cases of conventional combustion （air with 21% O2 at 300 and 1273 K） and the highly preheated and diluted air （1273 K with 10% O2 and 90% N2） combustion （HPDAC） conditions using an in-house computer program. It was found that by applying a combined diluted fuel and oxidant instead of their uncombined and/or undiluted states, the best condition is obtained for the establishment of HPDAC＇s main unique features. These features are low mean and maximum gas temperature and high radiation/total heat transfer to gas and tubes; as well as more uniformity of theirs distributions which results in decrease in NOx pollutant formation and increase in furnace efficiency or energy saving. Moreover, a variety of chemical flame shape, the process fluid and tubes walls temperatures profiles, the required regenerator efficiency and finally the concentration and velocity patterns have been also qualitatively/quantitatively studied.

Response Surface Modeling of Fuel Rich and Fuel Lean Catalytic Combustion of the Stabilized Confined Turbulent Gaseous Diffusion Flames

The Response Surface Methodology (RSM) has been applied to explore the thermal structure of the experimentally studied catalytic combustion of stabilized confined turbulent gaseous diffusion flames. The Pt/γAl2O3 and Pd/γAl2O3 disc burners were situated in the combustion domain and the experiments were performed under both fuel-rich and fuel-lean conditions at a modified equivalence (fuel/air) ratio (&oslash;) of 0.75 and 0.25 respectively. The thermal structure of these catalytic flames developed over the Pt and Pd disc burners were inspected via measuring the mean temperature profiles in the radial direction at different discrete axial locations along the flames. The RSM considers the effect of the two operating parameters explicitly (r), the radial distance from the center line of the flame, and (x), axial distance along the flame over the disc, on the measured temperature of the flames and finds the predicted maximum temperature and the corresponding process variables. Also the RSM has been employed to elucidate such effects in the three and two dimensions and displays the location of the predicted maximum temperature.

Response Surface Methodology and Artificial Neural Network Methods Comparative Assessment for Fuel Rich and Fuel Lean Catalytic Combustion

Modeling, predictive and generalization capabilities of response surface methodology (RSM) and artificial neural network (ANN) have been performed to assess the thermal structure of the experimentally studied catalytic combustion of stabilized confined turbulent gaseous diffusion flames. The Pt/γAl2O3 and Pd/γAl2O3 disc burners were located in the combustion domain and the experiments were accomplished under both fuel-rich and fuel-lean conditions at a modified equivalence (fuel/air) ratio (ø) of 0.75 and 0.25, respectively. The thermal structure of these catalytic flames developed over the Pt and Pd disc burners was scrutinized via measuring the mean temperature profiles in the radial direction at different discrete axial locations along with the flames. The RSM and ANN methods investigated the effect of the two operating parameters namely (r), the radial distance from the center line of the flame, and (x), axial distance along with the flame over the disc, on the measured temperature of the flames and predicted the corresponding temperatures beside predicting the maximum temperature and the corresponding input process variables. A three-layered Feed Forward Neural Network was developed in conjugation with the hyperbolic tangent sigmoid (tansig) transfer function and an optimized topology of 2:10:1 (input neurons:hidden neurons:output neurons). Also the ANN method has been exploited to illustrate the effects of coded R and X input variables on the response in the three and two dimensions and to locate the predicted maximum temperature. The results indicated the superiority of ANN in the prediction capability as the ranges of & F_Ratio are 0.9181 - 0.9809 & 634.5 - 3528.8 for RSM method compared to 0.9857 - 0.9951 & 7636.4 - 24,028.4 for ANN method beside lower values for error analysis terms.

Using KELEA (Kinetic Energy Limiting Electrostatic Attraction) to Improve the Efficiency of Fuel Combustion

There are many reports of devices and fuel additives being able to enhance the performance of automobiles and other forms of transportation that rely upon the combustion of gasoline or diesel fuels. The claims extend from increased mileage and power to significant reductions in toxic exhaust emissions of carbon monoxide and unburnt hydrocarbons. Progress towards more widespread applications of means of improving fuel efficiency has been impeded by the lack of a coherent explanation of the mechanism of action. Fuel combustion allows for the conversion of much of the available chemical energy in volatile hydrocarbons to mechanical energy, which moves the pistons within an engine. It is proposed that the amount of chemical energy in hydrocarbons can be increased by the absorption of an environmental force termed KELEA (kinetic energy limiting electrostatic attraction). In addition to providing greater mechanical energy with relatively less heat output, the combustion of KELEA activated fuels proceeds further with less toxic emissions of carbon monoxide and unburnt hydrocarbons from incomplete combustion. KELEA activation of fuels should become standard practice in the transportation industry, with potential additional benefits in slowing the rate of global warming.

Syngas Fuel Combustion in Re-circulating Vortex Combustor

This paper presents results on the combustion of syngas fuel in re-circulating vortex combustor. The combustion stability is achieved through the use of cavities in which recirculation zones of hot products generated by the direct injection of fuel and air are created and acting as a continuous source of ignition for the incoming main fuel-air stream. CFD （computational fluid dynamics） analysis was performed in this study to test the combustion performance and emissions from the vortex trapped combustor using synthetic gas or syngas fuel produced from the gasification process. The flame temperature, the flow field and species concentrations inside the vortex trapped combustor were obtained. Several syngas fuels with different fuel compositions （H2, CO, CH4, CO2, N2 and H20） and lower heating values were tested in this study. The changes on the flame temperature and species concentrations inside the combustor, the emissions of NOx, CO, CO2 at the exit of the combustor, the combustor efficiency and the total pressure drop for syngas fuels are presented in this paper. The effect of H2/CO ratio and the mass fraction of each constituent of syngas fuels and hydrogen-methane fuel mixtures on the combustion and emissions performances were investigated.

THE ESTIMATE OF THE EFFECTIVE FUEL COMBUSTION VALUE OF FOREST COMMUNITY IN THE DAXINGAN MOUNTAIN

Under the condition of absolute dry, more than thirty forest fuel pararneters,ash content. extract and burning point were measured. By the method of regression step by step. we found an experience formula which can estimate effective fuel high combusti on value of forest community from the Daxingan Mountain,and then,By means of modifying moisture content. we gave an approximate formula about actual heat releasing of forest fuels in the forest fire behavior.

Statistical model for combustion of high-metal magnesium-based hydro-reactive fuel

We investigate experimentally and analytically the combustion behavior of a high-metal magnesium-based hydro- reactive fuel under high temperature gaseous atmosphere. The fuel studied in this paper contains 73% magnesium powders. An experimental system is designed and experiments are carried out in both argon and water vapor atmo- spheres. It is found that the burning surface temperature of the fuel is higher in water vapor than that in argon and both of them are higher than the melting point of magnesium, which indicates the molten state of magnesium particles in the burning surface of the fuel. Based on physical considerations and experimental results, a mathematical one-dimensional model is formulated to describe the combustion behavior of the high-metal magnesium-based hydro-reactive fuel. The model enables the evaluation of the burning surface temperature, the burning rate and the flame standoff distance each as a function of chamber pressure and water vapor concentration. The results predicted by the model show that the burning rate and the surface temperature increase when the chamber pressure and the water vapor concentration increase, which are in agreement with the observed experimental trends.

Influence of Combustion Initial Conditions on Emissions Production Rates and Released Heat for Methane Fuel Mixtures

An estimation of combustion products (pollutants) which include CO, CO2 and NO mole fraction are reported in this paper for premixed methane/air flames. Different mixtures were used in this study, including lean, stoichiometric and rich subjected to varying degrees of pressures and temperatures ranging from 5 - 40 bars and 350 - 600 K, respectively. In this work, computer software was used to calculate the produced emissions species as well as the final (adiabatic) temperatures for each mixture. Results show that rich mixture of methane fuel produces the highest rate for carbon monoxide (CO) with slight increase as pressure and temperature increase. Where the stoichiometric mixture produces the highest rate of carbon dioxide (CO2). Results showed that this type of emission decreases with the increase of pressure and temperature. On the other hand, nitric acid (NO) was found to be the highest for the lean mixture with sharp increase as pressure and temperature increase. Finally, the combustion heat (Q) for each mixture where plotted against pressure and it was found that the rich mixture of methane produced the highest rates. Results also showed that combustion heat increases sharply with increased pressures and temperatures.