环形脉冲喷吹在袋式除尘清灰系统中的应用研究

针对袋式除尘脉冲喷吹清灰不彻底、不均匀的问题,提出了一种环形脉冲喷吹方式。采用数值模拟的方法,对环形脉冲喷吹与圆形脉冲喷吹在袋式除尘清灰系统中的清灰过程进行对比分析。在不同的喷吹压力、滤袋长度以及喷吹距离的条件下对这两种喷吹方式效果的差异性进行了讨论。结果表明:对于不同模拟条件下的这两种喷吹形式,滤袋侧壁压力峰值的变化规律大致相同;相同条件下,环形喷吹的整体清灰效果优于圆形喷吹;环形喷吹清灰方式滤袋侧壁压力峰值有更好的均匀性,对于袋式除尘清灰中常出现袋口清灰过度和袋底清灰不利的问题,有很好的改善作用。     

袋式除尘器喷吹过程的数值模拟

采用计算流体动力学(CFD)方法,通过改变袋式除尘器喷嘴和滤袋之间的距离,对喷嘴和滤袋之间的速度场以及滤袋内部脉冲喷吹气流的速度分布进行了数值模拟;在1个喷吹周期内不同的喷吹时刻,对滤袋内部喷吹气流的压力分布进行了数值模拟.根据模拟结果,分析了喷嘴和滤袋之间的距离变化以及不同喷吹时刻对清灰效果的影响,可为袋式除尘器的设...     

基于ZigBee的袋式除尘器的分布式压力监测

流场分布不均匀的袋式除尘器除尘效率会大幅度降低,因此开发分布式压力监测系统。用ZigBee技术开发终端采集节点、路由节点和中心分站等结构,节点的压力数据通过ZSC31050采集并利用温差程序进行补偿,校准后的压力数值通过ZigBee网络传送数据,利用240 cm除尘器滤袋检测实验分析压力。试验结果显示当喷吹压力为30 kPa、喷吹距离为240 cm时,检测长滤袋各点的分布压力,并测量喷口的不同压力。结果显示监测系统可以精确识别出袋式除尘器的压力分布。     

滤筒除尘器脉冲清灰参数优化设计

采用正交试验法对常用的?325 mm×?660 mm规格的滤筒进行脉冲喷吹实验,研究喷吹系统结构参数对滤筒清灰效率的影响,并采用F检验法确定主要影响因素,利用插值法获得该规格滤筒的最佳清灰参数组合,为滤筒除尘器的喷吹系统设计提供理论指导。     

600MW燃煤机组配套电袋复合除尘器进出口压差高问题的分析与处理

针对电袋复合除尘器进出口压差升高并超过设定值,吹灰效率下降,无法正常运行的问题,通过排查、核算、改造喷吹清灰系统,来提高清吹压缩空气流量、气源品质,同时完善了运行维护措施,使进出口压差回落至设定值,保证了除尘效率达到标准。     

顶驱内防喷器可靠性试验研究

为了提高顶驱内防喷器的可靠性,对三种不同内防喷器进行模拟工况试验,分别对寿命、通道压力关闭扭矩值、单向压差开启扭矩值三项关键指标进行了测试,并在试验结束后对产品进行解体检查。试验结果显示,密封失效是内防喷器的主要失效形式之一,提高装配精度、改善材料性能等均能提高其使用寿命。通道压力关闭情况下,55MPa以内不同产品扭矩值相差不大,但在大于55MPa后其扭矩值呈非线性增长;单向压差开启下不同产品受材质选型等因素影响扭矩值相差较大,15 MPa压差情况下不同产品扭矩值成倍增加,造成现场操作困难。     

高压水射流数值模拟研究及冲击载荷分析

针对不同工况的高压喷射流,利用VOF算法基于OpenFOAM开源平台开展流场模拟研究。模拟结果显示,当压差为10 MPa时,液核结构始终保持光滑的圆柱状轮廓,未发生雾化现象,靶件表面的压力分布及总打击力总体较为平稳;压差为30,50 MPa的工况均存在明显的一次雾化现象,液核表面形成坑洼不平的形貌特征,并产生众多小液滴散布于液核四周,喷雾锥角分别为1.2°和1.6°,广泛存在的压力波证实喷射流存在跨音速流动现象,在喷口出口处产生数量巨大的漩涡结构,靶件表面的压力分布变化剧烈,产生瞬时压力峰值,分别高达32.5,54.5 MPa,总打击力具有较大的波动趋势,其标准差为0.136和0.517。研究表明,雾化现象导致靶件表面的压力分布剧烈波动,诱发瞬时压力峰值并使总打击力剧烈波动,从而能够提升高压清洗效果。     

组合式滤筒脉冲反吹清灰过程的数值模拟研究

滤筒除尘器的关键技术是清灰技术,清灰效果关系到滤筒除尘器的效率、滤筒使用寿命及运行经济效益等各项指标,因此对滤筒除尘器的清灰性能研究具有重要意义。本文利用FLUENT软件,对2种不同喷嘴型式的组合式滤筒进行了脉冲反吹清灰过程的数值模拟,分析不同喷嘴模型下滤筒内的速度场以及压力场,从固定监测点和沿流向2个方向探究不同模型清灰时滤筒侧壁的压差峰值和压差峰值到达时间情况,以及不同喷嘴型式对滤筒清灰性能的影响。结果表明无散射器拉法尔喷嘴对组合式滤筒清灰效果比带散射器拉法尔喷嘴好,散射器的作用虽然对上滤筒清灰效果有明显改善,但对于下滤筒清灰效果较差。本文成果可为解决组合式滤筒清灰问题提供指导作用。     

燃气轮机进气滤筒动态清灰效果评价

针对目前在燃机进气段广泛应用的燃机进气滤筒缺乏清灰效果评价方法和标准的现状，基于一般通风过滤器EN779标准的试验方法，针对燃机需求设计了滤筒脉冲喷吹性能评价指标并开发了一种实验室试验系统；利用该试验系统对几种典型滤筒进行测试比较后发现，脉冲喷吹后过滤效率均没有下降；同时揭示了不同材质滤筒在脉冲喷吹后的清灰性能，指出复原率能够较好地反映滤筒的动态清灰性能，可以考虑将其作为效果评价的主要指标。相关成果可为相关从业人员的设计、选型和科研提供参考。     

烧结压力对粉末冶金铁基材料显微组织与性能的影响研究

烧结压力是粉末冶金材料制备过程中关键的工艺因素之一.根据45钢的铁碳配比,选取四种烧结压力4MPa、24MPa、40MPa和56MPa,在其他相关因素相同的情况下,分别考察这四种烧结压力对铁基粉末冶金材料的显微组织和性能的影响.实验表明,随着烧结压力的增加材料的密度也增加,当压力增加到一定程度即40MPa时,密度不再有大的变化;硬度也同样逐渐增大,在40MPa时达到峰值;断裂方式和烧结压力没有关系,但随着压力的增加断裂韧性越来越大,断裂痕迹愈发明显.     

高压水射流切割粘釜物的实验分析

为研究不同高压射流参数作用下粘釜物的切割清除效果,开展了粘釜物的高压水射流切割清除实验研究。实验以切割深度及切割宽度为衡量目标,研究了入射角、靶距、横移速度和出口压力4个射流参数对切割清除效果的影响,通过正交实验实现了射流参数的优化。结果表明:切割深度和宽度均随出口压力增加而增大,随横移速度增加而减小;而靶距接近初始段长度,入射角度为30°时切割深度及宽度达到最大值;正交实验表明,射流参数对切割深度的影响效果顺序依次为横移速度、入射角、出口压力、靶距;当前工况的最佳射流参数组合为:横移速度7.5 mm/s,入射角30°,出口压力值120 MPa,靶距15 mm。研究结果为工业现场清釜作业提供了实验依据及技术支持。     

双腔室自振脉冲喷嘴空化射流数值模拟

以风琴管喷嘴为基础,串联一个谐振腔形成双腔室自激振荡脉冲喷嘴,利用Fluent对其流场进行数值模拟,分析射流靶距、二级谐振腔腔长比、腔径比的变化对空化射流流场的影响。结果表明：谐振腔尺寸过大或过小均会影响涡环结构的形成,进而影响空化效果。当谐振腔腔长比为0.77、腔径比为2.6时,谐振腔内涡环结构对称性好,轴向含气率高,射流速度较高,该结构利于清洗效率的提高。靶面滞止压力可对空化效果产生影响。当射流靶距较小时,在滞止压力的作用下二级谐振腔无涡环结构产生,轴向含气率较低。当靶距增加到18 mm时滞止压力产生的影响减小,轴向含气率明显提高,因此清洗靶距应至少为18 mm。但靶距的增加会降低射流到达靶面的动能,因此最佳靶距应取18 mm。     

长袋低压脉冲袋式除尘器的应用

客观详实地介绍和分析丁长袋低压脉冲袋式除尘器在水泥、电炉炼钢、烧结行业除尘系统中的应用状况。实践证明，长袋低压脉冲袋式除尘器确吏足一种经济效益显著的除尘设备；它具有清灰能力强、喷吹压力低、除尘效率高、换袋方便、维修简单、成本低、自动化程度高等特点，有待进一步推广。     

爆炸等离子化合器的设计

为研究爆炸合成超硬材料,运用动力系数法设计一台50gTNT当量可重复使用的爆炸等离子化合器,主体材料采用16MnR钢,圆柱形结构,简体内径800him,圆柱形筒体长350mm,两侧为标准椭圆形封头,应用H．L．Brode,Kinneyand Graham,W．E．Baker3种方法计算得入射超压最大值为8．425×10^5Pa,相应反射超压为44．295×10^5Pa,运用动力系数法计算得50gTNT等效静载荷为2．5MPa,壁厚设计为10mm,采用自动埋弧焊。经有限元分析、3MPa水压和50gTNT爆轰实验,化合器完整,无破裂或塑性变形;经过1013Pa的抽真空实验,保压0．5h无泄漏。说明该设计方法科学可行。     

钻杆外壁清洗射流流场的数值分析

在采用高压水射流清洗钻杆外壁过程中,为了得到最佳的清洗位置和清洗角度,必须提高钻杆的清洗效率和质量,文章建立了外部射流流场控制方程组,结合标准的k-ε湍流模型进行化简求解,采用ICEM CFD建立网格模型,通过Fluent软件采用VOF气液两相流模型和SIMPLE算法对喷嘴外部流场进行数值模拟分析。在一定的喷射范围内,改变喷射角度模拟对钻杆外壁的理论清洗情况,在最佳的清洗情况下确定喷头在整个清洗装置中的安装位置和喷射角度。分析结果表明:在600mm的安装距离中,随着喷射角度的减小,射流束的分流情况越来越明显,当减小到15°时,流束基本朝向一边;该喷射范围内,随着轴线位置的增大,速度和压力都呈现衰减状态,当距离超过500mm,速度衰减较明显,所以适宜的喷射距离为500mm;当喷射角度除15°和90°时衰减较大外,其余角度下衰减情况基本相同。再通过对壁面打击力的分析得出最佳的喷射角度为60°。     

Experimental and numerical analysis on the effect of inlet distortion on the performance of a centrifugal fan with a mixing chamber

Inlet flow distortions, which are caused by fluid mixing, cause a significant deterioration in fan performance. An experimental test rig for an industrial fan with dual inlets and a mixing chamber was constructed. The flow fields in the mixing chamber of the fan were numerically investigated. Consequently, impact parameters, including the length of the mixing chamber (100, 200, and 300 mm) and the mass flow rate ratio (1 to 10), as well as their effects on fan performance, were discussed. A generalized formula considering the Reynolds number, hydraulic diameter, and mixing length was proposed to predict the pressure drop in dual inlets. Results show that the efficiency of and pressure in the fan decreased by 6.5% and 203 Pa, respectively, under mixing inlet condition. Optimum fan performance is achieved at a flow rate ratio of 5 under the same mass flow rate. The increase in the flow rate ratio kept the fan performance almost constant. At the design stage, fan performance and pressure decrease by an average of 2% and 70 Pa in increments of 100 mm mixing length, respectively. The results presented in this paper provide a basis in the design optimization of mixing structures.     

低压脉冲袋式除尘器在锅炉烟尘处理中的应用

低压脉冲袋式除尘器由于清灰效果好、喷吹强度和频率可调、所需压缩空气压力低等优点,广泛应用于锅炉烟尘除尘系统中。文章介绍了低压脉冲袋式除尘器工作原理,阐述了提高低压袋式除尘器除尘效果的主要控制途径,并对除尘器日常操作维护等方面做了简介。     

Effects of area discontinuity at nozzle inlet on the characteristics of self-resonating cavitating waterjet

The current research on self-resonating cavitating waterjet(SRCW) mainly focuses on the generation mechanism and structure optimization. Researches relating to the influences of disturbances at nozzle inlet on the characteristics of the jet are rarely available. In order to further improve the performance of SRCW, effects of area discontinuity(enlargement and contraction) are experimentally investigated using three organ-pipe nozzles. Axial pressure oscillation peak and amplitude as well as aggressive erosion intensity of the jet are used to evaluate the effects. The results reveal that area enlargement and contraction affect the peak differently, depending on the inlet pressure, nozzle geometry, and standoff distance; while area contraction always improves the amplitude regardless of these factors. At inlet pressures of 10 MPa and 20 MPa, area discontinuity improves the peak at almost all the testing standoff distances, while this only happens at smaller standoff distances with the inlet pressure increased to 30 MPa. The capability of area discontinuity for improving the amplitude is enhancing with increasing inlet pressure. Moreover, the cavitation erosion ability of the jet can be largely enhanced around the optimum standoff distance, depending on the type of area discontinuity and nozzle geometry. A preliminary analysis of the influence of area discontinuity on the disturbance waves in the flow is also performed. The proposed research provides a new method for effectively enhancing the performance of SRCW.     

An investigation on the spray characteristics of DME with variation of ambient pressure using the common rail fuel injection system

We investigated the DME spray characteristics about varied ambient pressure and fuel injection pressure using the common rail fuel injection system when the nozzle holes diameter is varied. The common rail fuel injection system and fuel cooling system were used since DME has compressibility and vaporization at atmospheric temperature. The fuel injection quantity and spray characteristics were measured. The spray was analyzed for spray shape, penetration length, and spray angle at the six nozzle holes. There are two types of injectors: 0.166 mm diameter and 0.250 mm diameter. The ambient pressure, which was based on gage pressure, was 0, 2.5, and 5 MPa. The fuel injection pressure was varied by 5 MPa from 35 to 70 MPa. By comparing with the common injector, using the converted injector it was shown that the DME injection quantity was increased 127% but it didn??t have the same low heating value. Both the common and converted injectors had symmetric spray shapes. In case of converted injector, there were asymmetrical spray shapes until 1.2 ms, but after 1.2 ms the spray shapes were symmetric. Also, the converted injector had shorter penetration length and wider spray angle than the common injector.