集成点火式燃烧器在催化装置余热锅炉中的应用

锅炉燃烧器的运行状况直接影响到整个锅炉的热效率及其尾气的排放,因此合理地设计和布置燃烧器非常重要。该项目主要是针对某催化装置余热锅炉燃烧器出现的一系列问题进行改进,通过对燃烧器进风结构的优化和出口流速的整合计算,并首次采用集成控制等方式将点火枪与控制柜集成一体化,减小了设备的占地面积。经过现场模拟点火测试,该设备的改型增强了燃烧器的工作稳定性,提高现场工作人员的操作效率和整个锅炉的经济性。     

Experimental study of the effects of hydrogen addition on the thermoacoustic instability in a variable-length combustor

The current study examined the self-excited thermoacoustic instability of hydrogen/methane premixed flames using a variable-length combustor (300–1100 mm). The global dynamic pressure, heat release rate oscillation, together with the flame dynamics were studied. Results showed that both the hydrogen concentration and the chamber length were critical in determining the acoustic oscillation mode and instability trend. Low-frequency primary acoustic modes (<200 Hz) were mainly excited when the hydrogen concentration was low, whereas primary acoustic modes with relatively higher frequencies (~400 Hz) tended to occur in cases with a high hydrogen proportion (>40%). For primary acoustic modes lower than 200 Hz, the primary oscillation frequency tended to increase linearly with a rising hydrogen proportion. Heat release oscillation and flame dynamics analyses demonstrated that for the flame with large-scale shape deformation, the initial addition of hydrogen would intensify the heat release oscillation. Nevertheless, a further increase in the hydrogen level tended to inhibit the heat release oscillation by weakening the flame shape deformation. Eventually, a sufficient high-level of hydrogen addition would weaken the primary acoustic modes that have similar frequencies.     

Reduction in nitrogen oxides emissions by MILD combustion of dried sludge

Demands for the thermal treatment of sewage sludge are increasing due to the regulation of its ocean disposal and the desire to recover its potential energy. Because of the high nitrogen content in sewage sludge, one of the concerns about its combustion is a potential increase in NO_x emissions. Although a number of studies have been conducted to reduce NO_x emissions by combustion modifications, very few studies have addressed the combustion of dried sludge. In this study, a combustion technique called moderate or intense low oxygen dilution (MILD) was applied to the combustion of dried sludge with the goal of reducing NO_x emissions. MILD combustion of dried sludge was tested using both our laboratory-scale vertical combustor with internal circulation and our horizontal cyclone combustor with external circulation. Tests were conducted to find suitable operating conditions and to demonstrate the stable MILD combustion of dried sludge. From these tests, fuel and air flow patterns were found to be an important factor in maintaining stable MILD combustion, and the horizontal cyclone combustor demonstrated excellent performance in the reduction of NO_x emissions by the MILD combustion of dried sludge.     

Co-firing hydrogen and dimethyl ether in a gas turbine model combustor: Influence of hydrogen content and comparison with methane

To promote the utilization of hydrogen (H₂) in existing gas turbines, dimethyl ether (DME) was used to co-fire with H₂ in a model combustor. The swirl combustion characteristics of DME/H₂ mixtures were measured under the varying H₂ content up to 0.7. The results show that the flow velocity elevates as the H₂ content increases, which is associated with the increased flame temperature. The OH level firstly increases and subsequently keeps nearly unchanged as the H₂ content increases. Meanwhile, the OH area nonlinearly increases with the increasing H₂ content. Moreover, the increasing H₂ content induces almost linearly decreased lean blowout limit (LBO), increased NO emission, and intensified combustion acoustics. Furthermore, the combustion characteristics of the 0.46DME/0.54H₂ mixture and CH₄ with the same volumetric heat value were compared. The 0.46DME/0.54H₂ flame displays lower LBO and higher NO emission than the CH₄ flame, which mainly results from the higher reactivity of 0.46DME/0.54H₂ mixture.     

Numerical study on premixed hydrogen/air combustion characteristics and heat transfer enhancement of micro-combustor embedded with pin fins

Aimed at improving the energy output performance of the Microthermal Photovoltaic (MTPV) system, it is necessary to optimize the structure of the micro combustor. In this paper, micro combustor with in-line pin fins arrays (MCIPF) and micro combustor with both end-line pin fins arrays (MCEPF) were presented to realize the efficient combustion and heat transfer enhancement, and the influence of inlet velocity, equivalent ratio, and materials on thermal performance was investigated. The results showed that pin fins embedding is beneficial to improving combustion, and the combustion efficiency of MCIPF and MCEPF reaches 98.5% and 98.7%, which is significantly higher than that of the conventional cylindrical combustor (MCC). However, with the increase of inlet velocity from 8 m/s to 14 m/s, MCIPF exhibits the highest external wall temperature with a range of (1302–1386 K), while MCEPF maintains the best temperature uniformity. As the inlet velocity increases to 10 m/s, the external wall temperature and temperature uniformity reach the optimum. Besides, under the conditions of different equivalence ratios, both external wall temperature and heat flux increases first and then decreases, meanwhile the temperature uniformity of MCEPF is significantly improved compared with that of MCIPF, they all exhibit the highest external wall temperature with an equivalence ratio of 1.1, and the thermal performance is greatly enhanced. By comparing the heat transfer performance of combustors with different materials based on MCEPF, it is interesting to find that the application of high thermal conductivity materials can not only increase the external wall temperature, but also improve the temperature uniformity. Therefore, materials with high thermal conductivity such as Aluminum, Red Copper and Silicon Carbide should be selected for application in micro combustors and their components. The current work provides a new design method for the enhanced heat transfer of the micro combustor.     

涡流技术在降低水煤浆燃烧产物中有毒物质的应用

为了在试验台和半工业性试验时,确定水煤浆燃烧过程中释放的气体中有害气体的质量浓度,采用涡流燃烧工艺,对水煤浆燃烧时释放气体的成分进行了试验研究。结果表明:采用涡流燃烧工艺,由于化学不完全燃烧减少,气体释放物中的CO含量随燃烧室温度提高而降低,NOx含量甚至低于标准值。这主要是因为涡流燃烧室燃料燃烧温度相对不高;喷射水煤浆的颗粒在燃烧层停留时间长,可以完全燃烧。该水煤浆燃烧工艺可以减少有害物质向大气的释放。     

软组织内金属异物Ｃ臂下单针定位特制钳取出术

【 摘要】 目的 探讨软组织内金属异物C臂下单针定位特制钳取术的可行性、微创性和安全性。方法 诊治38例 137颗金属异物软组织内存留患者,异物长度为0.2 ~ 3.5 cm,宽度为0.1 ~ 1.0 cm,离体表距离为0.5 ~ 6.5 cm,存留时间1 h ~ 10年。采用C臂透视下单针定位引入特制异物钳到异物处,夹住异物取出体外。结果 38例患者134颗异物均1次成功取出。手术时间为5 ~ 35 min,X线照射时间为0.5 ~ 4 min。未发生并发症。结论 C臂下单针定位特制钳取出术,是取出软组织内金属异物的1种简便、安全、微创,值得推广的方法。     

Design and study on performance of axial swirler for annular combustor by changing different design parameters

Recent technologies have been introduced for gas turbine engine to meet with stringent emission regulations. One of the technologies is to introduce recirculation in the combustion zone to control the residence time and mixing by help of swirling flow. Effect of variation in geometric parameters and inlet mass flow of swirler have been examined in this study by help of CFD. Detailed design methodologies have been proposed in this study to design a series of axial swirler with different vane angles and vane numbers. Substantial variation in swirler performance has been observed by changing vane angle, vane number and mass flow. Four different types of axial and radial velocity profiles have been observed. Turbulence distribution pattern shows double peaks at all positions and reduces with increasing axial distance.     

基于CO2稀释的旋流无焰燃烧理论判别方法

基于温度判据和时间判据,本文建立了考虑旋流入口条件和CO₂稀释的无焰燃烧理论判别方法并进行验证,进而讨论了结构参数和操作参数对燃烧模式和火焰稳定性的影响。模型预测的旋流无焰燃烧临界氧浓度与文献中实验数据相比,最大相对误差不超过8%。降低氧浓度、减小当量比或提高入口流量时,温度判据1变化不大,而时间判据更易满足,因此有利于实现无焰燃烧;低旋流数条件下,无焰燃烧稳定性较差。增大燃烧室高度时,温度判据1更易满足,而时间判据更难满足,温度判据1分界线下移更快,有利于形成无焰燃烧;减小燃烧室截面积时,温度判据1变化不大,而时间判据更易满足,有利于实现无焰燃烧;增大燃烧器出口面积时,温度判据1和时间判据均更难满足,且时间判据分界线下移更快,不利于形成无焰燃烧。     

Numerical simulation of oxy-coal combustion for a swirl burner with EDC model简

The characteristics of oxy-coal combustion for a swirl burner with a specially designed preheating chamber are studied numerically. In order to increase the accuracy in the prediction of flame temperature and igni- tion position, eddy dissipation concept （EDC） model with a skeletal chemical reaction mechanism was adopted to describe the combustion of volatile matter. Simulation was conducted under six oxidant stream conditions with dif- ferent OjN2/CO2 molar ratios： 21/79/0, 30/70/0, 50/50/0, 21/0/79, 30/0/70 and 50/0/50. Results showed that 02 en- richment in the primary oxidant stream is in favor of combustion stabilization, acceleration of ignition and increase of maximum flame temperature, while the full substitution of N2 by CO2 in the oxidant stream delays ignition and decreases the maximum flame temperature. However, the overall flow field and flame shapes in these cases are very similar at the same flow rate of the primary oxidant stream. Combustion characteristics of the air-coal is similar to that of the oxy-coal with 30% 02 and 70% CO2 in the oxidant stream, indicating that the rear condition is suitable for retrofitting an air-coal fired boiler to an oxy-coal one. The swirl burner with a specially designed preheating chamber can increase flame temperature, accelerate ignition and enhance burning intensity of pulverized coal under oxy-coal combustion. Also, qualitative experimental validation indicated the burner can reduce the overall NOx emission under certain 02 enrichment and oxy-coal combustion conditions against the air-coal combustion.