富氧燃烧对柴油机排放特性的影响

柴油机因其废气中的碳烟排放高而被排除在清洁发动机之外。减少碳烟排放的一种方法是增加缸内空气的氧含量，使燃烧更彻底充分进行。本文介绍了在S195柴油机上进行富氧燃烧试验。对其排放特性进行比较与分析，通过试验研究，找到在富氧条件下同时降低碳烟和NOx排放的方法。     

富氧燃烧烟气焓温特性分析

针对富氧燃烧锅炉增加了尾部再循环烟气和空气分离单元抽取的氧气特点,比较了常规空气燃烧锅炉焓温表计算方法与富氧燃烧方式下焓温表计算内容的区别,分析了富氧燃烧锅炉循环烟气焓、分离氧气焓和炉膛进口热燃烧气焓随氧气的体积分数变化的特性,给出了富氧燃烧锅炉烟气焓温表的计算方法,为富氧锅炉热力计算提供了理论依据.     

高温空气燃烧和富氧燃烧在加热炉生产应用中的对比研究

以韶钢加热炉富氧燃烧试验和高温空气燃烧技术的改造实践为基础,介绍了这两个新技术的不同应用和效果.富氧燃烧可以降低能耗,提高产量,富氧3.69%时,产量提高15.6%.富氧2%～40%时,可节约燃耗16.4%～31.3%.采用高温空气燃烧技术,也可提高产量,降低燃料消耗,同时火焰弥散地充满炉膛,亮度均匀,钢坯加热均匀,氧化烧损少.     

柴油机富氧燃烧排放特性的试验研究

介绍了在S195柴油机上进行富氧燃烧的试验，对柴油机排放特性进行了比较与分析，目的是通过试验研究，找到在富氧条件下同时降低碳烟和NOx排放的方法。研究结果表明，增加进气氧的质量分数，碳烟排放大幅度下降，HC和CO也趋于下降，但NOx排放显增加；推迟供油提前角，可以使NOx排放降低，但碳烟有上升趋势，HC和CO排放增加。所以，采用富氧燃烧时必须同时推迟供油提前角，才能获得较低的排放量组合。     

膜法富氧试验及富氧燃烧

介绍膜法富氧的原理和作者进行的富氧试验,阐明富氧燃烧的意义及工程应用的特点。     

柴油机应用富氧空气对燃烧及排污的影响

1引言“柴油机应用富氧空气的探讨”(见《内燃机》1988年第6期)一文,就富氧空气对柴油机的指示功率、机械效率和燃油消耗率的影响做了探讨。结果表明:富氧空气对提高柴油机的指示功率、机械效率及降低燃油消耗率起到了积极作用。至于对柴油机的燃烧过程及其排污的影响未作深入探讨,本文仅就这两个方面作些浅析。     

炉内烟气成分对富氧燃烧锅炉传热特性的影响

针对炉内烟气成分及其物性在不同燃烧方式下的变化对富氧燃烧锅炉炉内流动、温度及传热特性的影响进行了研究．研究表明,除烟气质量流量m外,不同燃烧方式间烟气成分的差异使烟气的物性有明显的不同,如密度、比热容和气体辐射吸收系数等,将显著影响炉内的流动、温度及传热分布．首先,炉内烟温取决于m cp的共同作用,由于CO₂、H₂O与N₂比热的差异,富氧燃烧烟气的比热明显高于空气燃烧,使富氧燃烧锅炉烟气质量流量在显著低于空气燃烧条件下才可获得与之相近的炉内烟温分布;其次,由于CO₂、H₂O与N₂辐射性质的差异,富氧燃烧烟气的吸收系数明显高于空气燃烧,不利于炉内高温火焰与壁面的辐射换热,因此富氧燃烧需在更高炉内烟温下才可获得与空气燃烧相近的壁面传热量．因此,在设计新型富氧燃烧系统或改造现有空气燃烧系统时,需综合考虑烟气流量与成分及物性变化的影响．     

富氧燃烧技术在内燃机中的应用

利用高分子选择性气体分离膜对空气进行分离,从而得到含氧量≥２８％的富氧空气用于工业燃烧,是一种节能效果好,经济效益高,可较少环境污染的高效燃烧技术。但是,这一燃烧新技术在应用最为广泛的动力机械－内燃机上却基本未得到研究和应用。     

天然气加湿富氧燃烧特性分析及烟气置换NGH方案

天然气工业锅炉的污染物排放标准日趋严格,采用单一的控制污染物排放技术手段已难以满足现有需求.本文以提高燃烧热效率与控制污染物排放量为目标,基于富氧燃烧、加湿燃烧与低氮燃烧的组合技术路线,提出一套天然气富氧加湿燃烧及烟气置换开采天然气水合物(NGH)方案.对天然气预混水蒸气燃烧进行数值模拟,确立最佳水蒸气预混比为Rf=0.33.在此基础上,分析不同烟气再循环率及过量空气系数对天然气加湿燃烧特性及污染物排放特性的影响规律以得出最优工况.该工况经烟气循环一次后,直接置换开采NGH的能源投资回报值(EROI)为7.5,具有实际开采价值.     

富氧燃烧锅炉初探

介绍了不同目的的锅炉富氧燃烧技术,重点分析了膜法富氧对于锅炉性能所带来的影响,对于进一步发展膜法富氧锅炉技术和扩大应用提出了建议.     

不同气体燃料燃烧特性及热特性分析

由于气体燃料容易实现燃烧过程精确控制及燃烧的清洁化,文章采用数值计算的方法,对6种常见气体燃料的燃烧特性及热特性进行理论计算,并通过改变空气过量系数、空气预热温度、富氧度等燃烧条件对其燃烧特性及热特性进行对比和分析.结果表明,预热温度每提高200℃,对于天然、焦炉煤气和沼气来说,可提高燃烧温度约90℃,高炉煤气和发生炉...     

Characteristics of oxy-fuel combustion in gas turbines

This paper reports on a numerical study of the thermodynamic and basic combustion characteristics of oxy-fuel combustion in gas turbine related conditions using detailed chemical kinetic and thermodynamic calculations. The oxy-fuels considered are mixtures of CH₄, O₂, CO₂ and H₂O, representing natural gas combustion under nitrogen free gas turbine conditions. The GRI Mech 3.0 chemical kinetic mechanism, consisting of 53 species and 325 reactions, is used in the chemical kinetic calculations. Two mixing conditions in the combustion chambers are considered; a high intensity turbulence mixing condition where the combustion chamber is assumed to be a well-stirred reactor, and a typical non-premixed flame condition where chemical reactions occur in thin flamelets. The required residence time in the well-stirred reactor for the oxidation of fuels is simulated and compared with typical gas turbine operation. The flame temperature and extinction conditions are determined for non-premixed flames under various oxidizer inlet temperature and oxidizer compositions. It is shown that most oxy-fuel combustion conditions may not be feasible if the fuel, oxygen and diluent are not supplied properly to the combustors. The numerical calculations suggest that for oxy-fuel combustion there is a range of oxygen/diluent ratio within which the flames can be not only stable, but also with low remaining oxygen and low emission of unburned intermediates in the flue gas.     

Liquid fuels spray and combustion characteristics in a new micro gas turbine combustion chamber design

Experimental nozzle spray analysis of different nozzle sizes was performed to investigate the effect of the spray profile on combustion quality. Detailed numerical investigation analysis investigated the effect of discrete phase model (DPM) on liquid fuel atomization and combustion characteristics. Four injectors of 2.98, 5.95, 8.93, and 11.90 kg/h nominal capacities numbered from 1 to 4 were tested on new micro gas turbine (MGT) chamber designed especially for liquid biofuels. The fuel was tested in the range of 2.36 to 9.43 kg/h achieving stable turbine operation in the pressure range of 0.1 to 1 bar. Stable operation was achieved for injector number 2 in the range of 0.1 to 0.5 bar compared with 0.2 to 0.6 bar for injector number 3 and 0.5 to 1 bar for injector number 4, while the smallest injector number 1 was not operational above 0.1 bar. The experimental results produced favourable low CO emissions of 95 ppm, NO_x emission of 31 ppm, and average turbine inlet temperature (TIT) of 1316 K at maximum pressure. The numerical simulation with DPM using similar injector and operating conditions showed good agreement with the experimental results averaging CO emissions of 99 ppm and NO_x of 13 ppm at TIT of 1329 K.     

Experimental study on the flame propagation characteristics of heavy oil oxy-fuel combustion

This paper studied the flame propagation characteristics of heavy oil oxy-fuel combustion in ignition and stable combustion. The results showed that the ignition process could be divided into three stages: the pro-ignition, mid-ignition and end-ignition. The pro-ignition, the fire core generated and evolved into spherical; the mid-ignition, the spherical fire core gradually turn into tapered structure; the end-ignition, the flame tapered structure disappeared and turn into a relative stable columnar structure. By calculating the flame propagation velocities, we found that in the same combustion atmosphere, the flame propagation velocity in 29% O2 was higher than that in 21% O2; in the same O₂ concentration, the flame propagation velocity in O₂/N₂ atmosphere was higher than that in O₂/CO₂. During the stable combustion, we observed the local flame structure extinguished, distorted and grew.     

Thermal analysis and kinetics of coal during oxy-fuel combustion

The pyrolysis and oxy-fuel combustion characteristics of Polish bituminous coal were studied using non-isothermal thermogravimetric analysis. Pyrolysis tests showed that the mass loss profiles were almost similar up to 870℃ in both N_2 and CO_2 atmospheres, while further mass loss occurred in CO_2 atmosphere at higher temperatures due to char-CO_2 gasification. Replacement of N_2 in the combustion environment by CO_2 delayed the combustion of bituminous coal. At elevated oxygen levels, TG/DTG profiles shifted through lower temperature zone, ignition and burnout temperatures decreased and mass loss rate significantly increased and complete combustion was achieved at lower temperatures and shorter times. Kinetic analysis for the tested coal was performed using Kissinger-Akahira-Sunose(KAS) method. The activation energies of bituminous coal combustion at the similar oxygen content in oxy-fuel with that of air were higher than that in air atmosphere. The results indicated that, with O_2 concentration increasing, the activation energies decreased.     

Comparative study on combustion and oxy-fuel combustion environments using mixtures of coal with sugarcane bagasse and biomass sorghum bagasse by the thermogravimetric analysis

Biomass and coal have different physicochemical properties and thermal behavior. During the co-combustion of coal-biomass mixtures, their thermal behavior varies according to the percentage of each fuel in the mixture. Thereby, this research aims to characterize the thermal behavior of mixtures of coal, sugarcane bagasse, and biomass sorghum bagasse as biomass in simulated combustion (O₂/N₂) and oxy-fuel combustion (O₂/CO₂) environments. Experiments have been performed in duplicate on a thermogravimetric analyzer at heating rate of 10 °C/min. A uniform granulometry was considered for all materials (63 μm) in order to ensure a homogeneous mixture. Four biomass percentages in the mixture (10, 25, 50 and 75%) have been studied. Based on thermogravimetric (TG) and thermogravimetric (DTG) analyses, parameters such as combustion index, synergism, and activation energy have been determined, as well as the combustion environment influence on these parameters. The results indicate that, although sugarcane bagasse has the lowest activation energy, the thermal behavior of both types of biomass is similar. Thus, biomass sorghum bagasse can be used as an alternative biomass to supply the power required during sugarcane off-season. For both mixtures, optimal results were obtained at 25% of biomass. By analyzing the environment influence on combustion behavior, the results indicate that when N₂ is replaced with CO₂, it is observed an increase in reaction reactivity, a higher oxidation rate of materials and an improvement in evaluated parameters.     

Combustion characteristics of Turkish lignites at oxygen-enriched and oxy-fuel combustion conditions

Combustion and oxy-fuel combustion characteristics of two Turkish lignites (Orhaneli and Soma) were investigated by Thermogravimetric Analysis (TGA) method. Experiments were carried out under oxygen-enriched air and oxy-fuel combustion conditions with 21, 30, 40% oxygen concentrations. Three heating rates of 5, 10, and 20 °C/min were considered and the isoconversional kinetic methods of FWO, KAS, and Friedman were employed to estimate activation energies. The uncertainty assessment in obtaining the activation energy values was also considered. The obtained results indicated that the combustion of volatiles at both air and oxy-fuel conditions were approximately identical. However, at air combustion conditions, the decomposition of CaCO₃ took place at temperatures above 700 °C. This decomposition process was independent of the oxygen concentration and took place when the temperature reached to a certain threshold. The decomposition of CaCO₃ did not accomplish in oxy-fuel conditions as far as the temperature was higher than 900 °C. Combustion in oxy-fuel conditions had higher activation energy values comparing to conventional combustion atmosphere. The activation energy values were approximately unchanged at the start of combustion regardless of oxygen concentration or combustion atmosphere at about 165 kJ/mol and 150 kJ/mol for Orhaneli and Soma lignites, respectively. The apparent activation energies were higher at elevated oxygen concentrations. The uncertainties values related to FWO method were lower than KAS and Friedman methods. The calculated average uncertainty values were found to be at the range of 5–15% for most of the cases.     

不同长度泡沫陶瓷内低浓度瓦斯燃烧特性研究

搭建了碳化硅泡沫陶瓷内低浓度瓦斯燃烧实验台,研究了不同长度碳化硅泡沫陶瓷内低浓度瓦斯燃烧温度分布及污染物排放,探究了不同长度碳化硅泡沫陶瓷对低浓度瓦斯燃烧特性的影响。结果表明:在相同的当量比和相同的混合气流速下,燃烧室温度随着碳化硅泡沫陶瓷长度的增加而增加,同时,出口排烟温度降低,而温升梯度随着碳化硅泡沫陶瓷长度的增加而减小;在相同的当量比、相同的混合气流速下,随着碳化硅泡沫陶瓷长度的增加,CO和NO的排放量减少;而相同的当量比、相同长度的泡沫陶瓷和不同混合气流速下,CO排放随流速的增大而减小,NO排放随着流速的增加而增加;在相同的流速、相同长度的泡沫陶瓷内,CO排放随着当量比的增大而减少;NO排放随当量比的增大而升高。     

灰煤混合燃料的燃烧动力学特性研究

利用TGA/SDTA851e型热重分析仪,对煤及不同灰煤比的混合燃料进行了热失重实验,获得了其热失重特性曲线。采用单个扫描速率的Coats-Redfern法、多重扫描速率的FWO（Flynn-Wall-Ozawa）法和Starink法三种典型的热分析方法求取了各样品的动力学参数。结果表明：随着灰煤比的升高,样品燃烧反应平均过程的活化能增高;灰煤比由0升高到0.15时,样品的活化能、着火温度和燃烬温度变化较大;灰煤比从0.15升高到0.45时,活化能、着火温度和燃烬温度变化较小。同时,通过对比几种分析方法的计算结果,认为采用多重升温速率法求取活化能时要谨慎,建议采用单重升温速率法和多重升温速率法相结合来分析燃料的热解及燃烧机理。     

Experimental study on oxy-fuel combustion of heavy oil

Oxy-fuel combustion of heavy oil can be applied to oil field steam injection boilers, allowing the utilization of both heavy oil and CO₂ resources. The present study investigated the oxy-fuel combustion characteristics of heavy oil under different conditions, including the flame, temperature, and pollutant emission characteristics. The results showed that heavy oil combustion was stable at O₂ concentrations of 29%, as the O₂ concentration was increased, the flame began to brighten gradually, becoming shorter and thicker, while the temperature gradient became higher and the high temperature zone moved closer to the burner exit. The overall temperature and the combustion rates in O₂/CO₂ atmospheres were below those seen in O₂/N₂ atmospheres. The volume of NO emitted in the flue gas was almost unaffected by the change in O₂ concentrations in atmospheres containing high concentrations of CO₂, but it increased rapidly with increasing O₂ concentration in O₂/N₂ atmospheres.