【作者】 邢双喜；

【导师】 黄伟光； 徐纲；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2012， 博士

【摘要】 微小型燃气轮机作为分布式供能的核心单元得到了越来越广泛的应用。为了降低燃气轮机的NOX排放,近几十年来各国大力开展低NOX燃烧技术研究,主要包括稀态预混燃烧技术、富燃-焠熄-稀态燃烧技术、催化燃烧技术和无焰燃烧等,其中稀态预混燃烧技术已在工业燃气轮机上得到成功应用,然而稀态预混燃烧过程中非常容易出现热声耦合振荡问题。热声耦合振荡中的低频高幅的压力振荡会干扰燃烧过程,增大污染物的排放,严重时会对整个燃烧系统造成结构性的破坏。本文通过数值计算和实验相结合的手段,研究了径向旋流预混型燃烧室的污染物生成与热声耦合振荡特性。本文中的径向旋流器采用切向方形进气通道产生旋流,在每条进气通道上游布置有一根开有多个喷孔的预混燃料喷杆,由喷孔流出后的预混燃料与来流空气经过旋流器进气通道进入预混通道内预混,并在预混通道和燃烧室内燃烧,径向旋流器中心处安装有值班喷嘴,用于稳定预混火焰。研究了三种旋流强度（S1=0.81、S2=0.93和S3=1.03）、两种预混燃料喷射方向（离心喷射和向心喷射）、两种喷孔布置方式（A型：喷孔距旋流器端壁较远。B型：喷孔紧临旋流器端壁。）、两种喷杆周向位置（0°：喷杆位于进气通道正上方。10。：喷杆向进气通道压力面方向周向偏离10°。）和值班比（值班燃料量占总燃料量百分比）对燃烧室内流动特性和燃烧特性的影响。首先,本文通过三维数值计算的方法研究了旋流强度、预混燃料喷射方向、喷孔布置方式、喷杆周向位置和值班比等参数对燃烧室内流动特性和燃烧特性的影响。研究发现,预混燃料采用向心喷射时的预混效果较好,采用离心喷射时则容易造成预混通道中心区燃料过富；预混喷孔采用B型布置时预混效果非常好,而采用A型布置时则造成预混通道中心处燃料浓度偏低,不利于火焰的稳定；喷杆位置对预混通道内的燃料分布影响明显,采用正对旋流器进气斜槽中心的0。布置时预混效果最好,而采用偏离10°布置时则造成预混通道内燃料分布呈现出中心和靠近壁面略高的形式；增大值班比有利于火焰的稳定,但会增加高温区范围,造成NOX排放的增加。然后,在设计建造的燃烧实验台上测试了结构参数（预混燃料喷射方向、喷孔布置方式和喷杆周向位置）和进气参数（进气温度、当量比、理论火焰温度、速度、值班比和压力）对污染物排放和热声耦合振荡的影响。研究发现：1)由结构参数造成的燃料在预混通道内的不均匀分布将增加NOX和CO的排放水平,并导致热声耦合振荡加强。预混燃料采用向心喷射、喷孔B型布置和喷杆0°布置时的NOX排放最低,且燃烧平稳,未出现强烈的热声耦合振荡问题；2)随着进气温度和当量比的提高,CO迅速降低,NOX逐渐提高,热声耦合振荡的声压级先增加后降低,并伴随有典型的分叉现象和迟滞现象；3)将进气温度和当量比统一用理论火焰温度Tad表示,对于预混良好的C₃结构燃烧室,在进气速度为34-46m/s,理论火焰温度为1600-1700K时,可使NOx和CO排放均小于10ppm@15%O2,且具有很好的稳定性,NOx正比于exp（0.01Tad）；4)随着进气速度的提高,CO近似线性增加,NOx近似线性降低,热声耦合振荡的声压级随着进气速度的增加先增加而后降低；5)提高值班比造成CO和NOx排放的同时提高,火焰稳定性提高,但在某一值班比附近热声耦合振荡的声压级会加强,随着值班比的增加声压级先增加而后突然降低；6)测试了进气压力分别为0.11和0.22MPa的工况,随着值班比的增加,进气压力对NOx排放的影响越来越显著,当值班比为0时NOx排放几乎不受进口压力的影响,而在值班比为15%时NOx排放则从17ppm@15%02提高到了25ppm@15%O2。最后,将上述最优的组合方案应用于国家863项目的某型燃机,对该燃机不同负荷下燃烧室的工作状态在常压下进行了模化性能试验。分别测试了值班点火和复合点火（值班喷嘴和预混喷嘴同时喷入燃料）两种点火方式下点火曲线,证明采用复合点火方式更加可靠。测试了熄火曲线,随着进气空气量的增大,吹熄当量比逐渐降低,当进气空气量为额定空气量的4.56%时,可在当量比高于0.038时成功点火和稳定燃烧,而当空气量增加到10%时,该当量比降到了0.019。设计状态下：燃烧室总压损失为0.063略大于0.05的设计目标；出口温度场分布OTDF为0.0327,RTDF为0.0214,满足OTDF小于0.2、RTDF小于0.08的设计要求；壁面温度最高不超过650℃,远小于材料允许的工作温度；纯预混工作方式下NOx排放不大于9.5ppm@15%O2,满足小于25ppm@15%O2的设计要求,而CO排放接近于零。本文系统的研究了预混燃料供给方式和旋流强度等结构参数和进气温度、当量比、理论火焰温度、速度、压力、值班比等进气参数对径向旋流预混型燃烧室的污染物生成和热声耦合振荡特性的影响,为开发微小型燃气轮机低污染燃烧室提供了技术支持,并且对稀态预混燃烧中的热声耦合振荡的形成机制方面的研究进行一定的补充。采用的径向旋流预混燃烧室具有极低的污染物排放和稳定的燃烧特性,基本满足863项目微小型燃气轮机低污染燃烧室的性能要求,具有广阔的应用前景。更多还原

【Abstract】 As key equipment of distributed energy supply system, the micro and small gas turbine have been widely used gradually. In order to reduce the NOx emission of gas turbine, more efforts have been made on developing Low NOx combustion technology in the recent decades, including Lean-Premixed combustion, Rich-burn Quick-quench Lean-premixed combustion （RQL）, Catalytic Combustion and Flameless combustion etc. The Lean-Premixed combustion has already been used in industrial heavy gas turbine, but it is prone to thermoacoustic coupled oscillation. Low bands of oscillations can disturb the combustion process and increase the emission of pollution, and in some case may structurally damage the combustor.In this paper, the pollution formation and thermoacoustic coupled oscillation characteristics have been researched with numerical and experimental methods.The radial swirler used in this paper takes tangential rectangular passages as swirl generator, and mount a main fuel spray rod with many tiny holes just upstream of each inlet passage. The fuel and air flow through the swirler inlet passages and mix in the mixing-passage, and then are burned in the mixing-passage and combustor. A pilot nozzle is mounted in the center of radial swirler to stabilize the premixed flame. Three swirl number （S1=0.81, S2=0.93and S3=1.03）, two main fuel inject direction （centrifugal and centripetal）, two spray holes position （A type: spray holes are away from the swirler wall. B type:the spray holes are near the swirler wall.）, two spray rod circumferential position （0°:just upstream of the inlet passage center.10°:rotated10°at the direction of pressure face） and pilot percentage （the percentage of pilot fuel in the total fuel supply） have been researched to reveal all the effects on the flow and combustion characteristics in gas turbine combustor.Firstly, the effect of swirl number, main fuel’s inject direction, position of spray hole and spray rod, percentage of pilot fuel on the flow and combustion characteristics of combustor were researched with3-dimentional computation. Our research found that good mixing of fuel could be reached by injecting fuel centripetal, and when fuel is centrifugally injected the fuel will be rich in the center zone of mixing passage. Spray hole positioned with B type could reach good mixing and with A type will form a lean fuel zone at the mixing passage center, which could lead to blow off of the flame. The position of spray rod has strong effect on the distribution of fuel in the mixing passage. When the spray rod is just positioned at0°, a good mixing of fuel will be reached. And if the spray rod is biased to10°, the fuel distribution in the passage will be rich at the center and near the passage wall. When increase the percentage of pilot fuel, the flame will be more stable, but the high temperature zone near the pilot will be extended and thus the NOx formation increased.Secondly, the effects of structural parameters （such as main fuels inject direction, position of spray hole and spray rod） and operating conditions （such as inlet temperature, inlet velocity, equivalence ratio, percentage of pilot fuel and pressure） on pollution emission and thermoacoustic coupled oscillations have been tested. Results show that:1) The nonuniform of fuel\air mixture in the mixing passage formed by the structure will increase the NOx and CO emission, and enhance the thermoacoustic coupled oscillation level. When main fuel is centripetally injected, with main fuel spray rod mounted at0°and B type spray hole position, the NOx emission is the lowest without obvious thermoacoustic coupled oscillation;2) With the increase of inlet temperature and equivalence ratio, the CO will decrease sharply and the NOx increase linearly, the thermoacoustic coupled oscillations’sound pressure level first will increase and then decrease, and hysteresis and bifurcation phenomena will be observed;3) Adiabatic flame temperature Tad is used to combine inlet temperature and equivalence ratio. In the well premixed C₃combustor, when inlet velocity is34⁴6m/s and Tad is1600¹700K, the NOx and CO emission can be less than10ppm@15%O2, and has a good flame stability, NOx is proportional to exp（0.01Tad）;4) With the increase of inlet velocity, CO will increase and NOx decrease linearly at the same time, the thermoacoustic coupled oscillations’sound pressure level first will increase and then decrease;5) With the increase of pilot percentage, CO emission will increase quickly and NOx increase gradually, the flame stability will be enhanced, but the thermoacoustic coupled oscillation will appear at some critical pilot percentage, with the increase of pilot percentage, the sound pressure level will increase first and then decrease abruptly;6) The pollution emission of0.11and0.22MPa operating conditions were tested, with the increase of pressure, the effect of pressure on NOx emission is enhanced, when the pilot percentage is0%the NOx emission has no change at the two operating pressure, but when the pilot percentage is15%, the NOx emission is17ppm@15%O2at0.11MPa and25ppm@15%O2at0.22MPa.At last, the best structure of combustor has been tested at modeled operation conditions at the863program’s low emission combustor project’s request, and the characteristics of ignition, blow-off, total pressure loss, outlet temperature field, wall temperature and pollution emission were tested. Two types of ignition methods were tested, which are pilot ignition and multi-ignition, the multi-ignition has stable ignition characteristics. And the blow-off characteristics is also been tested, with the increase of air mass flow rate the blow-off equivalence ratio will decrease. When air mass flow rate is4.56%of the full-load, the blow-off equivalence ratio is0.038, and when the mass flow rate increased to10%, the blow-off equivalence ratio will decrease to0.019. The total pressure loss is0.063and greater than the aim of0.05. the outlet temperature field is very uniform, the OTDF=0.0327and RTDF=0.0214, and fulfills the aim of OTDF≤0.2and RTDF≤0.08. The combustor wall temperature is no higher than650℃,which is within the allowable limit of the combustor’s material. The NOx emission can reach9.5ppm@15%O2at pure premixed combustion, and is much lower than the aim of25ppm@15%O2and CO emission nearly zero.In this paper, structural parameters （the main fuel supply methods and swirl number） and operating conditions （such as inlet temperature, inlet velocity, equivalence ratio, percentage of pilot fuel and pressure） on the pollution emission and thermoacoustic coupled oscillation characteristics of radial swirl lean premix combustor have been researched systematically, and offered technical support for developing of micro and small gas turbines low emission combustor, and have made some complement for the research of thermoacoustic coupled oscillation mechanism in the lean premixed combustion. The radial swirl lean premix combustor can reach ultra low pollution emission and has a stable combustion characteristic, can fulfill the863program’s low emission combustor project’s request, and thus has a wide application prospect.更多还原