高空低压低温环境航空发动机燃烧室熄火特性实验

航空发动机高空熄火是非常严重的安全威胁,高空燃烧稳定性与可靠再点火是航空发动机燃烧室的普遍要求.文章介绍了高空低压低温条件下航空发动机燃烧室模拟实验设备方案和调试结果,实现了对地面状态到高空10 km处环境条件的模拟.研究表明,随着高度增加,贫油熄火极限油气比不断增大.地面状态的贫油熄火油气比为0.016,高空10 km条件下,熄火油气比为0.071,增大3倍以上.低压低温环境下,火焰锋面位置不断向喷嘴收缩,燃烧释放热区域缩小到燃油喷嘴头部附近,CH*发光强度不断衰减.在模拟高度4 km时,火焰开始转为淡蓝色,10 km时燃烧室内为淡蓝色火焰,燃烧趋于不稳定.      

燃气轮机合成气双旋流非预混燃烧室的设计及实验测试

本文针对上海交通大学25 kW燃气轮机性能试验台的合成气燃烧室开展了设计研究,完成了燃烧室样机的加工与实验测试。研究过程中,首先对合成气燃烧室开展了结构设计;采用双旋流结构的燃烧器进行合成气燃烧火焰组织;采用了燃烧室头部贫燃方式(低当量比)设计以保证燃烧室低排放特性;利用双层壁冷却方式进行火焰筒壁面冷却。在燃烧室结构设计的基础上,利用数值方法系统分析了合成气双旋流非预混燃烧室工作特性,完成了合成气非预混母型燃烧室的设计优化。根据优化方案,完成了燃烧室样机的加工、安装,并进行了实验性能测试。实验结果表明实验工况该燃烧室燃烧稳定,NO_x排放小于25 mg/m~3@15%O_2。     

DMM燃料柴油机可控预混合燃烧的研究

本文介绍了在压燃式发动机上进行的预混合燃烧研究。在柴油机的进气道入口处安装了一个电控燃料喷射系统,喷入具有低十六烷值、低沸点的甲缩醛(DMM)燃料,在压缩冲程中形成均匀的混合气,并在上止点附近喷入少量柴油来点燃混合气。本文研究了预混合燃料比、发动机负荷、进气中CO2浓度和喷孔直径对发动机燃烧和排放的影响。试验结果表明,进气道喷射DMM的预混合燃烧能同时大幅降低NOx和碳烟排放,为降低柴油机有害排放提供了一种新途径。     

AVC中钝体布置与燃烧室流动特性研究

先进旋涡燃烧室具有高燃烧效率、低污染物排放和总压损失小等优点,其性能明显优越于其他贫燃料预混合燃烧设备.本文对不同钝体布置方式下,先进驻涡燃烧室中三维冷态气流的流动特性进行了数值模拟研究,得出了燃烧窜流阻、驻涡结构及其稳定性受前、后钝体距离和后钝体宽度两个几何参数影响的规律,为对先进驻涡燃烧室流动和燃烧特性的深入研究打下了基础.     

进气温度对微燃机燃烧室燃烧特性的影响分析

本文通过实验研究了在保持微型燃气轮机燃烧室出口排气温度不变的情况下,改变进口空气温度对燃烧室燃烧特性的影响.结果表明,随着燃烧室进气温度的增大,燃烧效率提高,燃烧室出口温度不均匀性系数减小,热阻增大,总压恢复系数有所降低.同时,实验结果还表明,随着燃烧室进口空气温度的增大,燃烧室出口处CO及未燃烬碳(UHC)排放浓度显著降低,但NO排放浓度则增大.根据实验结果,本文还分析了进气温度的改变对燃烧室燃烧特性的影响规律,为今后微型燃气轮机燃烧室的研制及改进提供了参考依据.     

湍流燃烧自适应求解技术在低排放燃烧室计算中的应用

基于各向异性非结构网格生成技术, 开发了面向复杂几何和复杂湍流燃烧问题的自适应求解算法, 并进行了程序代码的可靠性验证工作, 展示了各向异性网格自适应算法在降低问题求解规模、提高火焰面和流场计算精度等方面的优势.应用该自适应求解技术准确捕捉到了一维预混层流火焰、二维对冲火焰和三维本生灯湍流火焰的流场信息, 火焰面附近的温度、速度、组分等物理量与实验值吻合很好.对一款富油-快速混合-贫油(rich-burn, quick-mix, lean-burn, RQL)低排放发动机燃烧室进行了计算分析, 发现了燃烧室内的热声不稳定现象.      

二甲醚燃料微动力装置内HCCI试验研究

二甲醚(DME)是一种能从煤、天然气和生物质中制取的燃料,能够实现发动机超低排放。本文以二甲醚为燃料,改变压缩比,对微型HCCI自由活塞式动力装置进行了单次冲击的可视化试验,采用高速数码相机拍摄燃烧过程,且首次开发了微燃烧室内部压力测试及分析系统。通过可视化试验研究,得出了压缩比等关键参数对微动力装置内燃烧特性的影响规律,获得了本文工况下微动力装置压缩着火的临界状态条件,并且通过燃烧压力测试及分析系统首次得到了微燃烧室内部燃烧压力曲线。本文试验研究结果为揭示微动力装置微压缩燃烧规律,以及为微动力系统的设计提供了一定的理论依据。     

不同喷嘴结构合成气燃烧室动态特性的实验研究

通过中压全尺寸燃气轮机燃烧室测试平台的合成气燃烧试验,对单喷嘴和多喷嘴燃烧室的动态特性进行了比较分析.在本文的测试工况下,燃烧室没有产生强烈的热声振荡,所有的燃烧过程都很稳定,说明喷嘴的设计是合理的.多喷嘴燃烧室在相似工况下动态压力幅值比单喷嘴燃烧室要小一半以上,功率谱曲线相对平滑,说明多喷嘴燃烧室确实能降低燃烧噪声....     

基于乙烯或氢气的吸气式旋转爆轰发动机实验

基于氢气的旋转爆轰发动机研究较多,而碳氢燃料与空气混合较为困难,导致基于乙烯的旋转爆轰发动机燃烧技术难度很高.使用宽视野范围的可视化燃烧室观察旋转爆轰波的研究在国内尚未开展.在同一燃烧室内进一步开展了乙烯或氢气的吸气式旋转爆轰实验,来流总温为283~284 K,燃烧室壁面有140°石英玻璃观察窗,便于观察旋转爆轰波运动过程.空筒燃烧室爆轰环腔外径为100 mm,轴向长度为151 mm.燃料通过150个直径0.8 mm圆柱孔进入燃烧室,空气通过喉部1 mm宽的收敛扩张环缝流入环腔.高速摄影和低高频压力传感器均验证了旋转爆轰波的存在和速度值.以氢气为燃料的旋转爆轰波速度最高可达理论值的101%,爆轰波增压效应可达40%左右,乙烯旋转爆轰波速度可达理论值的89%.旋转爆轰波结构容易发生变化,不规则.氢气旋转爆轰的维持对燃烧室的结构要求比碳氢燃料要低,比乙烯旋转爆轰波更加稳定.      

进气预冷富燃预燃混排涡扇发动机热力循环

为满足高超声速飞行器对高比冲和大推力发动机的需要,提出了一种可重复使用的进气预冷富燃预燃混合排气涡扇发动机(Pre-cooled and Fuel-rich Pre-burned Mixed-flow Turbofan,PFPMT)热力循环。PFPMT发动机的特点是增大内涵空气进气预冷程度,内涵压气机为富燃燃气发生器提供空气作为氧化剂,内涵空气与预冷器出口燃料混合燃烧产生富燃燃气,驱动涡轮、带动内涵压气机与风扇增压,风扇外涵空气与涡轮出口排气在主燃烧室中掺混燃烧,产生高温燃气由喷管产生推力。对发动机热力循环进行了参数化分析,发动机比冲随着压气机压比的增大而增加,尤其是随着风扇压比增加的更为明显;单位推力主要随风扇压比增加而增加,受内涵压比影响较小。发动机地面的比冲与单位推力分别可以达到4500 s与900 N·s/kg以上;在Ma=5.0飞行条件下,发动机比冲与单位推力在3500 s与1100 N·s/kg以上。     

Towards the development of an efficient low-NOx ammonia combustor for a micro gas turbine

Recent studies have demonstrated stable generation of power from pure ammonia combustion in a micro gas turbine (MGT) with a high combustion efficiency, thus overcoming some of the challenges that discouraged such applications of ammonia in the past. However, achievement of low NOx emission from ammonia combustors remains an important challenge. In this study, combustion techniques and combustor design for efficient combustion and low NOx emission from an ammonia MGT swirl combustor are proposed. The effects of fuel injection angle, combustor inlet temperature, equivalence ratio, and ambient pressure on flame stabilization and emissions were investigated in a laboratory high pressure combustion chamber. An FTIR gas analyser was employed in analysing the exhaust gases. Numerical modeling using OpenFOAM was done to better understand the dependence of NO emissions on the equivalence ratio. The result show that inclined fuel injection as opposed to vertical injection along the combustor central axis resulted to improved flame stability, and lower NH₃ and NOx emissions. Numerical and experimental results showed that a control of the equivalence ratio upstream of the combustor is critical for low NOx emission in a rich-lean ammonia combustor. NO emission had a minimum value at an upstream equivalence ratio of 1.10 in the experiments. Furthermore, NO emission was found to decrease with ambient pressure, especially for premixed combustion. For the rich-lean combustion strategy employed in this study, lower NOx emission was recorded in premixed combustion than in non-premixed combustion indicating the importance of mixture uniformity for low NOx emission from ammonia combustion. A prototype liner developed to enhance the control and uniformity of the equivalence ratio upstream of the combustor further improved ammonia combustion. With the proposed liner design, NOx emission of 42?ppmv and ammonia combustion efficiency of 99.5% were achieved at 0.3?MPa for fuel input power of 31.44?kW.     

小型航空发动机燃烧室设计软件包的工程应用

1引言小型航空发动机燃烧室设计软件包由燃烧室大量成熟的经验设计关系和多维气动热力分析软件组成，其中经验关系用于燃烧室初始方案设计，多维气动热力分析软件对燃烧室流场和性能进行全面分析，用于燃烧室详细设计。它的优越性在于能将经验设计的可靠性和多维数值分析的先进性结合起来，从而优化燃烧室的设计，缩短燃烧室研制周期。在文献出中介绍了软件包的开发过程和技术内容，本文着重举例介绍软件包对两台回流燃烧室进行气动性能分析和工程设计的情况，由此可以看到软件包对燃烧室设计的重要指导作用。2软件包的组成和功能软件包由六…     

LES studies of the flow in a swirl gas combustor

Environmental and other practical concerns have led to the development of compact gas turbine combustors burning lean mixtures leading to potentially low CO and NO_x emissions. The compact design requires efficient atomization and mixing together with a compact premixed flame. Associated with these requirements are higher temperatures, increased heat transfer, and thermal load, thus increasing the danger of combustion instabilities (causing performance deterioration and excessive mechanical loads), and possible off-design operation. Numerical simulations of reacting flows are well suited to address these issues. To this end, large eddy simulation (LES) is particularly promising. The philosophy behind LES is to explicitly simulate the large scales of the flow and the thermochemistry, affected by boundary conditions whilst modeling only the small scales, including the interaction between the flow and the combustion processes. Here, we examine the flow and the flame in a model gas turbine combustor (General Electric’s lean premixed dry low NO_x LM6000) to evaluate the potential of LES for design studies of engineering applications and to study the effects of the combustor confinement geometry on the flow and on the flame dynamics. Two LES models, a Monotone Integrated LES model with 1 and 2 step Ahrrenius chemistry, and a fractal flame-wrinkling LES model coupled to a conventional one-equation eddy-viscosity subgrid model, are used. Reasonable agreement is found when comparing predictions with experimental data and with other LES computations of the same case. Furthermore, the combustor confinement geometry is found to strongly affect the vortical flow, and hence also the flame and its dynamics.     

燃气轮机中热值合成气燃烧室改造技术——现场调试与考核

将某型烧天然气的燃气轮机改为烧中热值合成气,需要改造燃烧室、燃机控制系统、燃料供给系统和相关配套系统,并校核燃机关键部件的通流匹配情况.在完成合成气燃烧室设计、试验和制造之后,需要进行燃气轮机组的安装调试、现场测试和考核.本研究所建立了燃气轮机现场测试平台;进行了合成气燃气轮机的安装调试、168小时连续运行考核和第三方的燃机性能考核;初步掌握了燃机控制系统和配套系统的改造技术.现场测试平台用贴片式热电偶对火焰筒壁温进行了监测,用示温漆测量了满负荷工况火焰筒壁温分布,用燃气分析仪测量了燃烧室效率和污染物排放.考核结果表明燃机功率、燃机热耗、燃烧效率、污染物排放基本达标.     

燃料空气供给条件对热声不稳定燃烧影响的研究

对Solar低排放预混燃烧系统的燃烧稳定性进行了数值研究.应用非定常N-S方程、雷诺应力紊流模型及涡团耗散燃烧模型,数值模拟了该类型燃烧器在不同的燃料空气供给条件下的气流流动特性和压力振荡特性,并给出了不稳定发生时压力和速度振荡的幅值和频率.根据供给条件的不同,燃烧可以是稳定的或是不稳定的,取决于燃料到火焰前沿的迟滞时间.采用CFD方法,可精确地获得燃料到火焰前沿的迟滞时间,证实了所采用的模型能够精确预测不稳定燃烧的出现及振荡特性.通过调整燃料与空气的供给条件,可使振荡激励或阻尼.     

燃气轮机合成气燃烧室燃料气加湿实验研究

本文针对一种燃用合成气的40MW级燃气轮机燃烧室,进行了该型燃烧室的全压燃料气蒸汽加湿试验研究,得到了燃烧室在基本负荷下随加湿量变化污染物排放、燃烧室内动态压力、火焰筒壁面温度等重要参数的变化规律,分析了燃料气加湿对燃气轮机总体性能、污染物排放、火焰筒壁温及燃烧稳定性方面的影响,探讨了燃料气加湿对合成气燃烧中Nox生成的机理性作用. 研究表明燃料气加湿是降低燃用合成气的燃气轮机氮氧化物排放的有效方式.     

Modeling of a self-excited pulse combustor and stability analysis

The major bottleneck for popularization and utilization of the conventional mechanical valve pulse combustors is the self-priming mode of gas supply. An aerodynamic valve (as against mechanical valve) self-excited pulse combustor of the Helmholtz-type with continuous supply of gas and air was designed and a mathematical model was established in this paper. The theoretical model employed well-stirred reactor model and a single step Arrhenius chemistry, and took those factors which might affect the combustion stability into account. The factors include the variation of the mass rate of the reactants affected by the pressure in the combustion chamber, the convective and radiation heat loss in the combustion chamber, and the heat transfer and wall friction in the tailpipe. The effect of wall temperature of combustion chamber, wall heat transfer coefficient, tailpipe length and friction coefficient on combustionstability were analyzed. The range of combustion oscillations can be predicted. It is theoretically and experimentally shown that combustion oscillations can be produced with a continuous supply of fuel and air without mechanical valves. The experimental data show qualitative agreement with predictions from the theoretical model. The theoretical model could be a tool for designing and optimizing the self-excited pulse combustor.     

旋流燃烧室内同向和反向旋转射流湍流流动的数值模拟

针对发展高效低污染旋流燃烧技术的需要,对旋流燃烧室内两股同轴旋转射流相互作用的湍流旋流流动进行了数值模拟.计算中采用了一种新的代数Reynolds应力模型和QUICK离散格式.在两股射流同向旋转和反向旋转两种条件下,将模拟得到的燃烧室内湍流旋流流动的时均气体轴向速度场、切向速度场和静压场与实验数据进行了比较.     

Bifurcation analysis of steady states and limit cycles in a thermal pulse combustor model

Oscillatory behaviour of state variables is desirable in pulse combustors, as properly designed pulsations lead to improved performances, such as higher thermal efficiency and lower emissions compared to steady combustors. In the present work, we perform a systematic investigation of the stability of steady states and limit cycles of a pulse combustor model through numerical continuation. Different bifurcation parameters such as tailpipe friction factor, wall temperature, convective heat transfer coefficient, inlet temperature and inlet fuel mass fraction are varied to identify the complete ranges of those parameters at which limit cycles can be expected. This analysis identifies alternative stable periodic regimes in parameter space (e.g. friction factor). In addition, a few performance indicators such as amplitude of oscillations, cycle-averaged heat transfer and cycle-averaged specific thrust are compared between different ranges of friction factor yielding limit cycle oscillations. The comparison clearly shows that, depending upon the application, friction factor can be chosen from different regimes. The time-integration of the model is also performed to support the bifurcation results obtained from numerical continuation, wherever appropriate. The complete stability margin of limit cycle oscillations for those bifurcation parameters can be useful for improved design of the combustor and for determining the optimal operating conditions of pulse combustors.