Spouted and spout-fluid bed combustors 1: Devolatilization and combustion of coal volatiles

The devolatilization and volatile combustion of a single coal particle in spouted and spout-fluid beds have been studied. The results showed that the flame extinction time increases with the particle diameter, and decreases with the bed temperature. When the bed temperature and the air flow rate were fixed, the operation modes (spouted or spout-fluid bed) showed less effect on the mean flame extinction time. A mathematical model of the spouted bed mode for preignition and postignition periods has also been developed assuming the devolatilization rate to be controlled by heat transfer and multireaction pyrolysis kinetics based on volatile products. Ignition, heat transfer back from the volatile flame to the particle surface, variation in flame temperature, and the hydrodynamics of SB are taken into account. The model predictions, with some adjusting parameters, were in good agreement with experimental results.     

双模态燃烧室激波链/附面层相互干扰研究

研究优化燃烧室控制问题,燃烧引起的压力升高扰动对于双模态燃烧室流场内激波链/附面层相互干扰强度影响,同时由于喷油调节对燃烧效率也影响较大。为解决上述问题,采用变换燃烧室出口反压。计算出燃烧室内燃烧引起压力升高的实际情况,对不同出口反压条件下的双模态燃烧室冷流流场进行了数值仿真,并与试验结果进行对比,两者相互吻合。结果表明,燃烧室内激波链结构强度及位置对于出口反压的变化非常敏感,在实际燃烧室工作中可通过选择合适的供油规律来获得燃烧引起压力扰动对激波链结构强度及位置的气动控制,可实现双模态燃烧室的模态转换,使得燃烧室工作在最优模态。     

微型涡喷发动机燃烧室全覆盖气膜冷却

为了延长微型涡喷发动机燃烧室的使用寿命,针对燃烧室壁面高温区进行全覆盖气膜冷却研究. 在KJ-66微型涡喷发动机试车实验的基础上,比较实际燃烧工况下,排布方式和燃烧室外环的扩张孔对气膜冷却效果及燃烧室整体性能的影响. 结果表明,在实际微型涡喷发动机模型中,顺排的平均综合冷却效率低于叉排,但对壁面的综合降温效果优于叉排. 随着扩张孔出口直径的增大,气膜冷却效果逐渐改善,但会影响燃烧室出口温度分布的均匀性. 由于燃烧室后排冷却孔的影响,二次流射入主流会发生偏转,提升了气膜的冷却效果. 整体而言,全覆盖气膜冷却在实际燃烧工况下对燃烧室壁面有着很好的冷却作用,扩张型气膜孔能够有效改善燃烧室外环的气膜冷却效果.     

滚筒式煤泥干燥系统的改进

对滚筒式煤泥干燥系统中往复式燃烧炉在生产中出现的问题进行了分析,找出了燃烧炉砌体缝隙生成的原因;采用新型浇注材料烧结整体密封耐磨陶瓷对炉体进行密封后,煤泥干燥系统生产稳定,燃烧炉热工效率大大提高,节约了能源消耗,干燥机的生产能力增加。     

甲烷高温燃烧催化剂研究进展

催化燃烧具有环保、高效、节能等诸多优点.综述了甲烷高温催化燃烧的研究现状,对甲烷燃烧催化剂材料的研究进展做了较详细的介绍,并阐述了甲烷高温催化燃烧反应器的研究进展.     

强旋湍流气-固两相流动和煤粉燃烧数学模型及其在涡旋燃烧炉的应用(Ⅰ)——模型

结合新型燃煤涡旋燃烧炉的研制和冷、热态实验,建立并发展了二维强旋湍流气固两相流动和煤粉燃烧的数学模型,以此作为对涡旋燃烧炉内多相流动。传热和燃烧过程进行数值模拟和分析的基础。     

Corrosion of nickel-base and iron-base alloys in a simulated fluidized-bed coal-combustion environment

The modes of initiation and propagation of corrosion attack on a series of high-temperature alloys were studied in synthetic gas mixtures at 900°C. The gas mixtures were intended to simulate the oxygen and sulfur partial pressures experienced in reducing zones in a coal-fired fluidized-bed combustor and comprised mixtures of CO, CO₂, and SO₂. The alloys studied were candidates for in-bed heat exchanger tubing for an air-heater cycle operating at 843°C and 300–500 psig and so ranged from type 300-series stainless steels to nickel-base alloys. With the exception of two FeCrAlY alloys and types 304 and 347 stainless steels, it was found that sulfidation corrosion could be initiated on all the alloys within 0.25 hr; the rate of propagation of the corrosive attack depended on the flux of SO₂ in the environment and on the nickel content of the alloys. The presence of iron in the alloys appeared to slow the initiation of sulfidation, by forming a continuous iron oxide layer. The effects of various alloying additions are discussed, and a schematic model for the initiation of sulfidation is proposed.     

Investigation of gas-solid flow characteristics in a novel internal fluidized bed combustor by experiment and CPFD simulation

Based on the coal self-preheating combustion technology, this research proposed a novel internal fluidized bed combustor (IFBC) with an internal separator for stable preheating of fuel. In order to verify feasibility and operation stability of IFBC, cold experiment, electrical capacitance tomography (ECT) and computational particle fluid dynamic (CPFD) simulation were performed in a laboratory-scale IFBC. The effects of superficial air velocity (U_g) and return valve structure on the operation and gas-solid flow characteristics were investigated. The results revealed that the CPFD prediction agreed well with the experiment values. The pressure balance curve presented an “8″ shape distribution, and the particle volume fraction (PVF) showed ‘core-annular’ distribution features. With the increase of U_g, the PVF in the standpipe increased, and the discharge pattern of the return valve changed from continuous discharge to intermittent discharge, and the solid circulation flux showed a trend of increasing first and then decreasing. With the decrease of the outlet opening of return valve (Φ), the gas–solid flow behavior in standpipe experienced a transition from gas leakage, stabilizing material seal, and blocking state. For U_g = 2 m/s, Φ = 50 %, an effective solid seal in the return valve was established and IFBC has a stable circulation and operation.     

Combustion of Liquid and Gaseous Fuels in a Supersonic Combustor

Results of an experimental study of a full scramjet model operating on kerosene, which was performed in an IT-302M hotshot wind tunnel based at the Institute of Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Sciences, and an experimental study of a model operating on hydrogen, which was performed in a hotshot wind tunnel with fire heating based at the China Aerodynamic Research and Development Center, are reported. The tests were performed for Mach numbers 5 and 6 for flow parameters close to in-flight conditions. An optimal system for kerosene injection under these conditions was determined, and the thrust characteristics of the engine model were examined. The possibility of controlling kerosene combustion in tests in the short-duration wind tunnel was analyzed, and special features of fuel ignition in a short combustor were considered. Intense combustion of kerosene was achieved with upstream injection of more than 3% of hydrogen, which allowed obtaining effective thrust. The distributions of static pressure and force characteristics of the model in the case of kerosene and hydrogen combustion were compared.     

燃烧室下游流场优化数值模拟研究

建立燃气轮机燃烧室点火前的流体流动计算模型,利用计算流体力学软件,对3组不同速度流体的流动情况进行了模拟计算分析燃烧筒流道内的速度场,压力场,对比燃烧筒内在不同压力和速度下流场内流体的流动,模拟计算区域的流场,然后实际进行点火实验,验证模拟结果,发现流场分布最均匀最有利于点火.