燃气轮机燃烧室的现状及发展趋势

针对我国燃气轮机燃烧室污染物排放的现状,介绍了各国对民用航空和工业用燃气轮机的排放规定,分析了燃气轮机燃烧室主要污染物的生成机理、影响因素以及减少污染物排放的措施.对先进的低污染燃烧室中具有代表性和发展前景的四种类型燃烧室作了简要的介绍,它们分别为双环预混旋流(TAPS)燃烧室、贫油预混预蒸发(LPP)燃烧室、富油燃烧-焠熄-贫油燃烧(RQL)低污染燃烧室以及驻涡燃烧室(TVC).并且介绍了高温升燃烧室的研究现状以及关键技术难题.最后,对燃烧室火焰筒多斜孔冷却、冲击/多斜孔复合冷却、层板冷却以及冲击/气膜冷却等四种方式的现状进行了讨论.     

Combustion of hydrogen in an experimental trapped vortex combustor

Combustion performances of pure hydrogen in an experimental trapped vortex combustor have been tested under different operating conditions. Pressure fluctuations, NOx emissions, OH distributions, and LBO (Lean Blow Out) were measured in the tests. Results indicate that the TVC test rig has successfully realized a double vortex construction in the cavity zone in a wide range of flow conditions. Hydrogen combustion in the test rig has achieved an excellent LBO performance and relatively low NOx emissions. Through comparison of dynamic pressure data, OH fluctuation images, and NOx emissions, the optimal operating condition has been found out to be Φp =0.4, fuel split =0.4, and primary air/fuel premixed.     

Flow field measurements in the cavity of a trapped vortex combustor using PIV

The experimental research on cavity flow field plays an important part in the structural design and optimization study of trapped vortex combustor (TVC). Many of the previous flow field experiments were conducted in the cold condition instead of during combustion. This paper adopting PIV system and Lambda-2 vortex criterion in-vestigates the influence of various factors, such as equivalent ratio in the cavity, air intake parameter in the cavity, mainstream air intake parameter and mainstream holder structure, on cavity flow field for a TVC using methane as the fuel. The experimental research showed that cold-condition flow field differed from the combustion flow field, in terms of either vortex core position or vortex structure. Mainstream air intake velocity and cavity air intake velocity affected the flow field structure. U-type and V-type mainstream holders had significant influence on cavity flow field.     

The role of in-cylinder gas density and oxygen concentration on late spray mixing and soot oxidation processes

An analysis of in-cylinder gas density and oxygen mass concentration (YO₂) impact on the mixing and oxidation processes and the final soot emissions in conventional high temperature diffusive Diesel combustion conditions is presented in this paper.Parametrical tests were performed on a single cylinder heavy duty research engine. The density was modified adjusting the boost pressure following two approaches, maintaining the YO₂ either before or after the combustion process. The YO₂ was modified by diluting fresh air with exhaust gas maintaining a constant density. The possibility of controlling the soot emissions combining both parameters (YO₂ and density) is evaluated and, in a final part, the NO_X emission results are also addressed.Results show that YO₂ has a strong effect on both mixing and oxidation processes while density affects principally the mixing process. Both parameters affect the final soot emissions. The density modification through adjustment of boost pressure modifies the trapped mass and has a strong impact on the evolution of YO₂ (thus on the evolution of the mixing process) during combustion. If the density is increased maintaining constant the YO₂ at the beginning of the combustion, the NO_X-Soot trade-off is enhanced.     

空气分级比对同轴分级燃烧室性能参数的影响

为掌握同轴分级燃烧室性能参数随空气分级比(主燃级空气流量的比值)的变化规律,以某同轴分级燃烧室为研究对象,数值分析了空气分级比对燃烧室的燃烧效率、总压损失、出口温度分布、污染物排放和绝热壁面最高温度的影响。结果表明：空气分级比主要会改变角涡位置的燃烧温度和高温烟气的停留时间;随着空气分级比的升高,燃烧室总压损失、出口温度分布系数、NO_x排放、绝热壁面最高温度逐渐升高,但燃烧效率、CO污染物排放、径向温度分布系数对空气分级比不敏感;在同轴分级燃烧室设计中,在保证燃烧稳定的前提下可采用较小的空气分级比以实现燃烧室高效、低阻、低污染燃烧。     

Measurement of the mixing quality in premix combustors

The problem of mixing fuel and air is the essential point of low emission combustion in gas turbines. In premixed combustors and fuel staged combustors the quality of the fuel–air mixture is the determinant parameter for the amount of emissions of nitric oxides (NO_x). The nearly perfect preparation of the fuel–air mixture is also a condition for trouble-free operation in catalytical combustion. Prevaporization of liquid fuels hampers the process of mixing. So the investigative work at the Department of Steam and Gas Turbines at the University of Bochum concentrated on experiments with liquid fuels. The results show that there is a great potential of reducing NO_x emission even with liquid fuels and reveal the key role of prevaporization and mixing. The experiments were carried out at a premix combustion test rig at moderate pressure. By using the technique of planar-laser induced fluorescence (LIF), highly time and spatially resolved measurements of fuel concentrations were yielded from the experiments. The optical measurements showed the structure of the mixture field of fuel and air in the zone downstream of the flameholder. The pollutant emissions were simultaneously monitored with conventional gas analysers. As the main result, the strong dependence of the pollutant emissions on the mixture could be clearly revealed. On one hand the homogeneity over the cross-section of the combustor was the main condition for low emission combustion. On the other hand the time-resolved two-dimensional LIF images of the turbulent mixture field showed that the instationary distribution also had a considerable influence on the rate of emissions. Even the mixture of static mixers contained spatial and temporal inhomogeneities, which could be observed by using the LIF-technique but not with conventional methods.     

Experimental Investigations on NOx Emission and Combustion Dynamics in an Axial Fuel Staging Combustor

Axial Fuel Staging(AFS)technology is an advanced low-emission combustion method in modem gas turbine,which divides the combustor into two axially arranged combustion zones.For revealing the characteristics of axial staged combustion,an industrial-grade combustor was designed and built.The distribution of temperature and velocity field in the combustor was presented with numerical simulation.And an Atmospheric Combustor Test Rig for axial staged combustion was built.The flow resistance characteristics of the combustor were measured at first.Then the effects of the equivalent ratio and the preheating temperature on the pollutant emission and combustion instability were investigated.The results show that the total pressure recovery coefficient in cold state is always above 98%;starting the secondary combustion at low load can reduce NO emissions by 50%,and can suppress the combustion oscillation amplitude of the combustor.At the design point with φ=0.62 and preheating temperature=400°C,NO emission and CO emission are 15.68 and 4.22 mg/m³(@15%O₂).     

市政污泥流化床掺烧生物质的NO与SO2排放特性研究

为了探究市政污泥燃烧过程中的气态污染物排放特性，在30 kW鼓泡流化床实验台上进行了市政污泥的燃烧实验，研究燃烧温度、二次风率、秸秆掺混比等参数对气态污染物排放特性的影响。结果表明：燃烧温度的升高会显著提高NO与SO₂的排放；提高二次风率使NO排放浓度减少，SO₂排放浓度增加；由于生物质中较低的N、S含量以及生物质与污泥燃烧的协同作用，污泥掺烧生物质能够有效地减少NO与SO₂的排放；秸秆占比由0提升至40%,NO由289 mg/m³下降至140 mg/m³,而SO₂排放浓度也从3 949 mg/m³下降至1 725 mg/m³;污泥掺烧秸秆时，NO与SO₂的整体排放特性与污泥单独焚烧相似，掺烧秸秆能够加快整体的燃烧速率，并加强燃烧气氛的氧化性，进而影响气态污染物的排放。     

微型燃气轮机燃烧室NOx排放性能实验研究

作为微型燃气轮机的核心部件之一,燃烧室性能的优劣将直接影响微型燃气轮机的整体性能。随着环保意识的增强和环保法规的日益严格,控制燃烧室污染物的排放业已成为一个重要课题。以一微型燃气轮机燃烧室为对象进行了热态条件下NOx排放性能的实验研究。实验结果表明：随着过量空气系数的增加,NOx的排放浓度呈下降趋势;燃烧区温度的升高以及在高温区停留时间变长,NOx生成量大大上升;在较高负荷工况下,NOx的排放量较小。     

Flame stability and emission characteristics of propane-fueled flat-flame miniature combustor for ultra-micro gas turbines

An engineering model of a propane-fueled miniature combustor was developed for ultra-micro gas turbines. The combustion chamber had a diameter of 20 mm, height of 4 mm, and volume of 1.26 cm³. The flat-flame burning method was applied for lean-premixed propane–air combustion. To create the stagnation flow field for a specific flat-flame formation, a flat plate was set over the porous plate in the combustion chamber. A burning experiment was performed to evaluate the combustion characteristics. The flame stability limit was sufficiently wide to include the design operation conditions of an equivalence ratio of 0.55 and air mass flow rate of 0.15 g/s, and the dominant factors affecting the limit were clarified as the heat loss and velocity balance between the burning velocity and the premixture flow velocity at the porous plate. CO, total hydrocarbons (THC), and NO_x emission characteristics were established based on the burned gas temperatures in the combustion chamber and the temperature distribution in the combustor. At an air mass flow rate of less than 0.10 g/s, CO and THC emissions were more than 1000 ppm due to large heat loss. As the air mass flow rate increased, the heat loss decreased, but CO emissions remained large due to the short residence time in the combustion chamber. NO_x emission depended mainly on the burned gas temperature in the combustion chamber as well as on the residence time. To reduce emissions despite the short residence time, a platinum mesh was placed after the combustion chamber, which drastically decreased the CO emissions. The combustor performance was compared with that of other miniature combustors, and the results verified that the present combustor has suitable combustion characteristics for a UMGT, although the overall combustor size and heat loss need to be reduced.     

废塑料流化床焚烧及排放特性的试验研究

在一内径40mm、高500mm小型电加热流化床焚烧炉上对废塑料的燃烧特性，包括燃烧效率、挥发份析出特性及烟黑的生成进行了试验，分析了主要气体污染物（SO2、NO、HCl)的排放特性及运行条件（过剩空气率、床温及水份等参数）对废塑料燃烧和排放的影响。     

喷嘴与安装孔之间的缝隙对微型燃气轮机燃烧室影响的数值分析

为了探究喷嘴与燃烧室壁面安装孔间的缝隙对微型燃气轮机燃烧室流动及燃烧特性的影响,运用三维数值计算软件,对30 kW微型燃气轮机燃烧室在不同面积缝隙下的燃烧过程进行了数值计算,得到了燃烧室内的流场及温度场,并对比分析了燃烧室各处的气体流量分配、燃烧室内部温度分布以及污染物排放量。计算结果表明:缝隙面积的变化对燃烧室内气量分配的影响是全局性的,随着缝隙面积的增大,缝隙内的气体流量增加,燃烧室其它各处的流量则相应减小。在贫燃的条件下,这一过程使得燃烧室内部的整体温度逐渐减低,随之C0的排放量小幅增大。此外,一定范围内的缝隙能够在降低燃烧室整体温度的同时维持火焰形态,有效降低NOx的排放量。     

Combustion and emission characteristics of a swirling fluidized-bed combustor burning moisturized rice husk

Burning of rice husk in a swirling fluidized-bed combustor (SFBC) was the focus of this experimental study. Swirl motion of a fluidized bed in this combustor was induced by an annular spiral distributor of primary air and also promoted by tangential injection of secondary air into the bed splash zone. “As-received” rice husk was moisturized with the aim to control NO emission from the combustor. The SFBC was tested at a constant fuel feed rate (of about 80 kg/h) for six fuel-moisture contents (from 8.4% to 35%). In each test series for the particular fuel quality, excess air was ranged from about 20% to 80%. Radial and axial profiles of temperature and gas concentrations (O₂, CO and NO) were plotted for different fuel options and operating conditions with the aim to study pollutants formation and reduction in different regions of the SFBC. With increasing the fuel-moisture content, the emission of NO from the combustor apparently reduced, while the emission of CO was adjusted at a quite low level due to the effects of secondary air. An effective least-cost control of both NO and CO emissions and high (over 99%) combustion efficiency are achievable when firing moisturized rice husk in this SFBC.     

Experimental study on N2O emission in O2/CO2 combustion with high oxygen concentration in circulating fluidized bed

To characterize the N₂O formation and fuel nitrogen conversion in an oxy-fuel circulating fluidized bed (CFB) combustor with high oxygen concentration, tests were carried out by analysing the axial concentrations of N₂O in a 50 kW_th CFB combustor. The conversion ratios from fuel nitrogen to gaseous N-containing pollutants were calculated. The initial N₂O concentrations in the bottom of the combustor were similar between oxy-fuel firing and air-firing. The axial N₂O formation was more in oxy-fuel combustion than in air-firing, improving the N₂O emission during 50% O₂/50% CO₂ combustion. The atmospheric variation significantly affected the conversion ratio from fuel nitrogen to N₂O. In addition, the conversion from fuel nitrogen to N₂O was much higher than that to NO. As a result, the N₂O emission during oxy-fuel CFB combustion cannot be ignored. Gas staging little influenced the N₂O emission. With the increasing ratio of secondary gas, the initial N₂O formation in the dense zone increased, while the axial N₂O formation along the combustor declined. By analysing the conversion ratios of fuel nitrogen, it was also found that gas staging obviously affected the conversion ratio from fuel nitrogen to NO by enhancing the NO to N₂ conversion. However, gas staging did not impact the conversion ratio from fuel nitrogen to N₂O.     

Development of high intensity CDC combustor for gas turbine engines

Colorless distributed combustion (CDC) has been demonstrated to provide ultra-low emission of NOx and CO, improved pattern factor and reduced combustion noise in high intensity gas turbine combustors. The key feature to achieve CDC is the controlled flow distribution, reduce ignition delay, and high speed injection of air and fuel jets and their controlled mixing to promote distributed reaction zone in the entire combustion volume without any flame stabilizer. Large gas recirculation and high turbulent mixing rates are desirable to achieve distributed reactions thus avoiding hot spot zones in the flame. The high temperature air combustion (HiTAC) technology has been successfully demonstrated in industrial furnaces which inherently possess low heat release intensity. However, gas turbine combustors operate at high heat release intensity and this result in many challenges for combustor design, which include lower residence time, high flow velocity and difficulty to contain the flame within a given volume. The focus here is on colorless distributed combustion for stationary gas turbine applications. In the first part of investigation effect of fuel injection diameter and air injection diameter is investigated in detail to elucidate the effect fuel/air mixing and gas recirculation on characteristics of CDC at relatively lower heat release intensity of 5 MW/m³ atm. Based on favorable conditions at lower heat release intensity the effect of confinement size (reduction in combustor volume at same heat load) is investigated to examine heat release intensity up to 40 MW/m³ atm. Three confinement sizes with same length and different diameters resulting in heat release intensity of 20 MW/m³ atm, 30 MW/m³ atm and 40 MW/m³ atm have been investigated. Both non-premixed and premixed modes were examined for the range of heat release intensities. The heat load for the combustor was 25 kW with methane fuel. The air and fuel injection temperature was at normal 300 K. The combustor was operated at 1 atm pressure. The results were evaluated for flow field, fuel/air mixing and gas recirculation from numerical simulations and global flame images, and emissions of NO, CO from experiments. It was observed that the larger air injection diameter resulted in significantly higher levels of NO and CO whereas increase in fuel injection diameter had minimal effect on the NO and resulted in small increase of CO emissions. Increase in heat release intensity had minimal effect on NO emissions, however it resulted in significantly higher CO emissions. The premixed combustion mode resulted in ultra-low NO levels (<1 ppm) and NO emission as low as 5 ppm was obtained with the non-premixed flame mode.     

油页岩干馏残渣和生物质混烧污染物释放特性研究

基于自行搭建的流化床试验台,对桦甸油页岩干馏残渣和生物质混合燃料进行了不同掺混比例、不同床温、不同粒径下的燃烧试验,得到了混合物燃烧后污染物气体释放的体积分数,并分析了其产生机理.结果表明:各燃料中SO2的释放体积分数与其中的含硫量成正相关性;NOx气体的产生机理复杂,其主要取决于氮元素的转化率;油页岩干馏残渣和燃料灰烬均对SO2和NOx具有吸附作用;混合燃料颗粒粒径过小会阻碍反应的继续进行,导致燃烧不彻底.     

Characterization and challenge of development of producer gas fuel combustor: A review

Producer gas, which derived from a biomass gasification process, is considered as one of the alternative fuels, which is suitable for the heating process and power generation. Due to low heating density and impurities, combustion in an external combustion chamber constitutes an obvious option for the utilization of producer gas via the combustion process. This paper reviews the technical challenges and the development of the producer gas combustor. Various combustion techniques are reviewed. A stable flame combustion with low emissions (both CO and NO_x) constitutes a main requirement of the producer gas combustion. Flame stabilization techniques such as swirl-vane coupled with bluff-body, swirl flow configuration, and staging combustion were successfully employed to enhance the stability and performance of the producer gas combustion. As shown in the results of the studies, the combustion process can operate in a wide range of equivalence ratios with the exhaust gas temperature >600 °C. This temperature is sufficiently hot for the power generation and heating applications. Overall, NOx and CO emissions were below 700 ppm and 1.3%, respectively. In the flameless combustion mode, ultra-low emission for both CO and NOx were recorded. However, higher emission can be found when operated at a higher thermal load combustor. Homogeneity of the thermal field and low polluting emissions make flameless combustion a promising lean and clean combustion technology. Integration of the benefits of flameless combustion and producer gas fuel is an outstanding contribution in reducing emissions and enhancing the efficiency of the combustion systems.     

部分预混旋流燃烧的大涡模拟

采用耦合涡耗散概念模型的大涡模拟方法,探究了Re和组分变化对部分预混旋流火焰动力学特性的影响。通过与实验结果定性和定量的比较,验证了大涡程序模拟燃烧过程的可靠性。计算结果显示Re的增加,会明显提高空-燃混合效率,从而导致部分预混火焰中预混燃烧模式的比例有所增加,且预混燃烧区域向上游移动,Re的增加也会使得火焰下游产生更多更快的涡破碎结构。N_2含量的增加,会减小流向回流区尺寸,降低空-燃混合效率,但对减小火焰温度具有明显效果,从而对降低NO_x排放产生积极作用。结论为进一步研究部分预混旋流燃烧室的不稳定性及燃烧效率提供了理论和方法上的指导。     

An overview on dry low NOx micromix combustor development for hydrogen-rich gas turbine applications

The paper presents a survey of the interactive optimization cycle at Aachen University of Applied Sciences, used for the development of a new low emission Micromix combustor module for application in hydrogen fueled industrial gas turbines. During the development process, experimental and numerical methods are applied to optimize a given baseline combustor with 0.3 mm nozzles with respect to combustion efficiency, combustion stability, higher thermal power output per nozzle and reduced manufacturing complexity.Within the described research cycle combustion and flow simulations are used in the context of parametric studies for generating optimized burner geometries and the phenomenological interpretation of the experimental results. Experimental tests, carried out on an atmospheric combustion chamber test stand provide the basis for validation of simulation results and proof of the predicted combustion characteristics under scaled down gas turbine conditions.In the presented studies, an integration-optimized Micromix combustor with a nozzle diameter of 0.84 mm is tested at atmospheric pressure over a range of gas turbine operating conditions with hydrogen fuel. The combustor module offers an increase in the thermal power output per nozzle by approx. 390% at a significant reduced number of injectors when compared to the baseline design. This greatly benefits manufacturing complexity and the robustness of the combustion process against fuel contamination by particles.During atmospheric testing, the optimized combustor module shows satisfactory operating behavior, combustion efficiency and pollutant emission level. Within the evaluated operating range, which correlates to gas turbine part-, full- and overload conditions, the investigated combustor module exceeds 99% combustion efficiency. The Micromix combustor achieves NO_x emissions less than 2.5 ppm corrected to 15 Vol% O₂ at the design point.Based on numerical analyses and experimental low pressure testing, a full-scale gas turbine combustion chamber is derived. High pressure testing in the auxiliary power unit Honeywell/Garrett GTCP 36–300 shows stable operation during acceleration of the engine, during IDLE and during load variations between IDLE and Main Engine Start (MES) mode. Throughout the investigated operating range, the combustion chamber generates low NO_x emissions under full-scale gas turbine conditions.     

Experimental investigation of combustion characteristics in a multi-staging vortex combustor firing rice husk

The paper described the combustion characteristics in a multi-staging vortex combustor by using rice husk as fuel. Effects of the operating conditions namely: equivalence ratio (Φ = 0.8, 1.0 and 1.2) and secondary air ratio (λ = 0.0, 0.15 and 0.25) on combustion characteristics (temperature distribution, fly ash and gas emission) were experimentally studied. In the experiments, the conventional vortex combustor consisted of two straight concentric cylindrical pipes, combustion chamber (outer chamber) and exhaust pipe (inner chamber). The variable size of middle section of the combustor was designed to be adjustable from 1.0D (conventional vortex combustor), to 0.75D and 0.5D as desired. The changes of the middle chamber size lead to multi-staging vortex inside the combustor. In the experiments, the rice husk was fed into the combustor at constant mass flow rate of 0.3 kg/min. Test results revealed that the mean temperature distribution for the multi-staging vortex combustor with middle chamber size of 0.5D was higher than those of 0.75D and 1.0D. The experimental results showed the maximum temperature of about 1176 °C in the vortex chamber with the middle chamber of 0.5D at equivalence ratio, Φ = 0.8 and no secondary air injection, λ = 0.0. Measurements of gas emissions from cyclone collector consisted of O₂ = 2.5%, CO₂ = 17.3%, and CO = 270 ppm, respectively.