轴对称湍流冲击射流场的数值预测

应用标准k-ε模型和一种重正化群（RNG）k-ε模型，对半封闭轴对称湍流冲击射流场进行了数值模拟。通过两种模型计算结果的比较以及与参考文献中LDV测量结果的比较，评价了RNGk-ε模型对冲击射流场的数值预测能力。最后，根据数值模拟的结果，从流体动力学角度分析了冲击射流场的结构特性。     

中心射流对旋流燃烧器热声振动的影响

在CH4与空气的化学当量比为0.7、空气量为25 m/s时进行了旋流燃烧器热声振动试验.分析了不同中心风量下旋流燃烧的热声不稳定特性.结果表明:在中心风量为10%时,旋流核心区明显受到中心射流的影响,热声振动振幅明显下降,最大峰值脉动压力下降216 Pa;中心射流对热声振动的影响存在一个阈值,提高射流速度可使中心射流作用于旋流核心区,从而影响燃烧与声波的耦合,以实现对热声振动的被动控制.     

Experimental Investigation on Liner Cooling Characteristics of a Mixed-Flow Trapped Vortex Combustor

The mixed-flow trapped vortex combustor(TVC) is a new type of combustor that applies trapped vortex flame stabilization technology to mixed-flow combustor.Compared with the traditional mixed-flow combustor,the mixed-flow TVC has many advantages,such as complicated structure of the vortex flow field inside liner,large cooling area,significant local hot spots on the liner,and large wall temperature gradient.In this paper,for a mixed-flow TVC with inclined multi-hole cooling,the liner wall temperat...     

低排放燃烧室空气雾化喷嘴射流破碎特性研究

针对当前广泛应用于低排放燃气轮机燃烧室中的空气雾化喷嘴,采用大涡模拟（Large Eddy Simulation,LES）和流体体积法（Volume of Fluid,VOF）研究了其在流动模糊（Flow Blurring,FB）和流动聚焦（Flow Focusing,FF）模式下射流一次破碎过程的差异。结果表明：两种模式的射流一次破碎过程均可分为3个阶段,气液交界面波动阶段、射流发展阶段和射流破碎阶段;喷嘴内部回流区的演变决定了气液交界面的波动程度,流动模糊模式下射流在后两个阶段的径向速度和形态变化程度均远高于流动聚焦模式,气泡回流过程在其射流破碎阶段占据主导地位,液体管道内气泡分布位置与涡的强度呈正相关。     

Numerical Study of the Swirl Effect on a Coaxial Jet Combustor Flame Including Radiative Heat Transfer

A numerical study of the swirl effect on a coaxial jet combustor flame including radiative heat transfer is presented. In this work, the standard k-ε model is applied to investigate the turbulence effect, and the eddy dissipation model (EDM) is used to model combustion. The radiative heat transfer and the properties of gases and soot are considered using a coupled of the finite-volume method (FVM), and the narrow-band based weighted-sum-of-gray gases (WSGG-SNB) model. The results of this work are validated by experiment data. The results clearly show that radiation must be taken into account to obtain good accuracy for turbulent diffusion flame in combustor chamber. Flame is very influenced by the radiation of gases, soot, and combustor wall. However, swirl is an important controlling variable on the combustion characteristics and pollutant formation.     

基于横向射流的旋流燃烧器热声不稳定控制

为研究横向射流控制旋流燃烧器内自激热声不稳定的机理,搭建了旋流燃烧器热声不稳定控制试验台架,分别采用了横向射流(JICF)和横向火焰射流(JFCF)研究了空气流率为1.333.3 mL/s、化学当量比为0.9、旋流强度为0.77时旋流燃烧器的热声不稳定控制作用.试验发现横向射流能够大幅度降低旋流燃烧器的热声不稳定强度,而且横向射流所占用的空气流率比例小.当横向射流空气流率比例XJICF为6%时,热声不稳定的有效压力振幅从1.712.Pa降到185.Pa,降低了89.2%.另外,横向射流的控制作用远远优于横向火焰射流,横向火焰射流需要在燃料流率比例XJFCF50%,时才能获得大于32.5%的控制效果.     

Experimental and Numerical Investigation of Effusion Cooling Performance Over Combustor Liner Flat Plate Model

ABSTRACT

This article presents a study of cooling performance of combustor liner of a gas turbine, using a flat plate model. The combustion process in gas turbine engines liberates very high temperature gases, which impacts the properties of the combustor liner. Hence, cooling of liner is important and is carried out by effusion cooling method. Experiments are carried out over a flat plate with staggered effusion holes. The hot mainstream air flows at a Reynolds number of 2.325 × 10⁵, which indicates a turbulent flow. The coolant to mainstream density ratios of 1.3 and 1.5 is maintained by varying the blowing ratios ranging from 0.5 to 2.5. Test plate surface temperature measurements are recorded by an infrared camera and the overall cooling effectiveness in the flow direction is calculated. Numerical validation for conjugate heat transfer analysis is performed using ANSYS workbench and the temperature contours obtained are compared with infrared camera images. MATLAB program is used to obtain the effectiveness contours for experimental and computational fluid dynamics results. The effectiveness contours are found to be similar, showing the increase in effectiveness with the increase in blowing ratios. Density ratios comparison shows that with the increase in density ratio, the overall cooling effectiveness marginally decreases.     

Annular Impinging Jet Controlled by Radial Synthetic Jets

This experimental study focuses on generation and control of annular impinging jets. The annular nozzle used in the investigations was designed with an active flow control system using 12 synthetic jets issuing radially from the central nozzle body. Measurements of the control effects were made on the impingement wall. The data acquisition involved wall pressure and wall mass transfer (by the naphthalene sublimation technique) using air as the working fluid. Also measured was time-mean flow velocity (by a Pitot probe) in the jet flow field. Moreover, flow visualization was carried out. Two main flow-field patterns (A and B) were identified. The patterns differ in the size of the separated-flow recirculation regions that develop attached to the nozzle central body: While pattern A is characterized by a quite small recirculation region (bubble) extending not far from the nozzle exit, pattern B exhibits a large recirculation region, reaching up to the impingement wall, on which it forms a stagnation circle. The control action modifies the flow field, resulting in changes of the corresponding heat/mass transfer distributions. The convective transfer rate on the stagnation circle can be demonstrably enhanced by 20% at a moderate nozzle-to-wall distance, equal to 0.6 of the nozzle outer diameter.     

小喷嘴间距撞击流的径向射流速度分布

采用热线风速仪对小喷嘴间距撞击流产生的径向射流的速度分布进行了实验研究.研究结果表明,径向射流在各个r.2D的径向断面上的速度分布具有相似性,呈高斯分布.在撞击面上无因次径向射流速度随着无因次径向距离的增大先增大后减小,而与喷嘴直径(D)、喷嘴间距(L)和出口气速无关.无因次径向速度在达到最大值前,与无因次径向距离成正比,在达到最大值后,无因次径向速度与无因次径向距离的1.33次方成反比.在撞击面上径向射流速度的最大值与出口气速成正比,与无因次喷嘴间距的0.551次方成反比.当L/D1时,无因次最大径向速度的位置随无因次喷嘴间距的增加而增加,当L/D1时,无因次最大径向速度的位置保持不变.     

The Mechanisms of Flame Stabilization and Low NO_x Emission in an Eccentric Jet Pulverized Coal Combustor

The mechanisms of flame stabilization and low NO_x emission features of an eccentric jet pulverized coal com-bustor were studied through numerical modelling and experimental investigation.The results show that theformation of the unique flowfield structure is closely related to the interaction among combustor configuration,the primary jet and the control jet;and that certain rules should be followed in order to obtain the optimumcondition for flame stabilization.The distributions of temperature and concentrations of NO,O_2,CO and CO_2inside the combustor were experimentally measured.The effects of structural and operational parameters oncombustion and NO formation were studied.It was found that reduction of primary air,suitable use of controljet and reasonable uptilt angle of the primary jet all contributed to the reduction of NO_x at the combustor exit.A new hypothesis,that reasonable separation of oxygen and fuel within the fuel-rich zone is beneficial to furtherreduction of NO_x emission,is given.The study showed that good compatibility existed between the capabilityof flame stabilization and low NO_x emission for this type of combustor.