离心式空气压缩机水冲洗除垢技术

介绍了离心式空气压缩机水冲洗除垢技术的方法,要求(水质、频度、时间、喷嘴及连接管道)、步骤、效率。该技术美国空气制品公司已成功用于140多套空分装置的离心式空压机上,包括鞍钢引进的35000m~3/h空分装置。它可延长压缩机的寿命,提高压缩机的空气流量和工作效率。图2表2参6。     

喷嘴结构对真空喷射雾化性能影响研究

基于Fluent软件模拟了柱型、扇型、锥型和混合型喷嘴真空喷射射流雾化过程,研究了喷嘴结构对动压力转换、射流速度和喷嘴出口湍动能的影响。结果表明,锥型喷嘴动压力较大,可提高静压能转换效率;扇型和锥型喷嘴喷射束宽度较大,利于大面积喷射成膜;扇型喷嘴易形成空化,出口湍动能较大,有助于液滴初次雾化破碎,而混合型喷嘴的空化层厚度最小,湍流区域最大。通过分析雾化锥角与喷嘴流量系数,发现扇形和锥直形喷嘴具有较大雾化锥角,但流量系数较小喷嘴压力损失较大;喷嘴直线段会提高锥型喷嘴雾化锥角和喷嘴出口湍动能,并使扇型喷嘴的流量系数增大,但射流雾化锥角减小。最后,本文尝试构建了真空喷射射流雾化数学模型。     

热流道系统喷嘴泄漏测试装置设计

与传统的冷流道模具相比,热流道模具具有节约原料、提高生产效率等优点而被广泛采用。喷嘴是热流道模具中的主要部件,喷嘴通常由喷嘴体和螺纹连接在其上的喷嘴头组成,在喷嘴体和喷嘴头的螺纹连接处有可能存在泄漏。现在由于没有专门的对喷嘴泄漏进行测试的装置,所以只能在用户使用时发现喷嘴体和喷嘴头的连接处存在泄漏后再对喷嘴进行修复或更换,影响了正常生产,甚至有可能造成质量和生产事故。     

新型环形复合喷嘴的数值模拟分析与研究

为解决传统气流粉碎能量利用率不高、粉碎物料所需成本高、产量低、物料加工范围有限等问题,通过对气流粉碎中喷嘴结构的改进,开发设计了一种新型环形复合喷嘴,运用数值模拟的方法对常规喷嘴和新型环形复合喷嘴进行了模拟。模拟结果表明,这种新型环形复合喷嘴比常规喷嘴具有射流速度快、射流相对集中和射程远等优点。     

PX—I型空调用大雾化角强旋流离心式喷嘴的设计

本文介绍了ＰＸ－Ｉ型空调用离心式喷嘴的结构设计特点,给出了喷嘴的主要性能参数,并对性能测试结果进行了全面分析。理论分析和实测结果表明,该喷嘴具有大雾化角和强旋流等特点,是一种新型空调用高效、节能喷嘴。     

空调用离心式喷嘴的雾化机理及性能评价

本文全面地阐述了空调用离心式喷嘴的雾化机理,并理论联系实际,分析了喷嘴结构设计中的一些问题。对喷嘴的性能评价指标进行了系统分类,提出了喷嘴性能综合评价指标。为喷嘴的研究开发和应用提供了理论基础和客观评价的依据。     

临界流喷嘴流道廓形对流出系数影响初探

研究低雷诺数临界流喷嘴流动特性.阐述了喷嘴的基本廓形和检测流量公式,对日本OVAL公司制造的喷嘴和国产喷嘴进行了入口段和出口扩散段形状的比对实验.实验结果表明:同一喷嘴,改变流向,流出系数也随即改变;圆弧入口的喷嘴的流出系数和临界背压比值,比锥形入口的喷嘴大;喷嘴喉径越小,这一特性越明显.实验结果对喷嘴设计与应用者具有一定的参考价值.     

喷水室喷嘴内部及喷嘴出口流场数值模拟

利用计算流体软件FLUENT建立了喷水室内喷嘴及喷嘴出口外部流场的三维数学模型。采用标准κ-ε湍流模型模拟了喷嘴内部及出口外部流场,并根据各种情况分析了喷嘴参数对流场速度分布、压力分布和出口速度的影响。结果表明,喷嘴的扩散角和扩散段尺寸对喷嘴及出口流场影响较大:喷嘴的扩散角直接影响喷嘴出口后液滴的方向和速度大小,并影响流场的湍流分布情况,影响流场的紊流区域分布,最终影响水滴与风流的热湿交换;扩散段尺寸影响流场压力分布,特别会产生负压区直接影响射流后液滴的状态。     

印刷涂布烘箱V型条缝喷嘴冲击射流流场的数值模拟

为了解印刷涂布设备烘箱V型条缝喷嘴冲击射流流场分布及其影响因素,采用标准k-ε湍流模型,对喷嘴射流冲击移动壁面进行数值模拟。分析了喷嘴冲击射流壁面附近速度场和压力场分布情况,考虑了影响喷嘴冲击射流壁面附近速度分布的喷嘴宽度和高度等因素。研究结果表明:在冲击射流中,喷嘴距壁面的高度和喷嘴宽度对壁面附近速度分布影响较为明显;综合考虑各种因素,较理想的喷嘴高度是15 mm,相应的喷嘴宽度为2.5 mm。     

三喷嘴蒸汽喷射泵的三维数值模拟研究及分析

蒸汽喷射泵的操作工况在偏离设计值时,喷射性能会严重恶化。本文借助连续介质力学数值模拟工具-STARCCM+,对三喷嘴蒸汽喷射泵内部流场进行了三维数值模拟。分析了操作参数(背压、工作蒸汽压力和引射蒸汽压力)对其喷射系数的影响,并与相同工况下单喷嘴蒸汽喷射泵进行对比。此外,对三喷嘴蒸汽喷射泵的结构参数(喷嘴轴线的汇交点位置)进行了考察。结果表明,在工作蒸汽变工况操作条件下,三喷嘴蒸汽喷射泵能够保持稳定、可靠运行;在相同工况下,三喷嘴蒸汽喷射泵的临界背压值小于单喷嘴。在多喷嘴蒸汽喷射泵的设计中,各喷嘴轴线的汇交点位置存在一最佳值。     

Performance Comparison of Four Waterjet Nozzles

This article presents the results of laboratory tests on four waterjet-cleaning nozzles for industrial use. The nozzles selected for the tests included standard cone-jet and fan-jet nozzles, a cavitating jet nozzle and a resonating jet nozzle. A series of cleaning and erosion tests were conducted to compare the performance of the nozzles in terms of erosion rates and jet coverage, based on the same amount of energy input. The fan-jet nozzle was extremely sensitive to small variations in standoff distance. The cavitating jet nozzle gave similar performance over a large range in standoff distance. The cavitating jet and fan-jet nozzles were more efficient at an angle of incidence of 0° and 40°, respectively. For the same settings, the cone-jet and resonating jet nozzles gave an overall poorer performance than the fan-jet and cavitating jet nozzles. The cavitating jet nozzle exhibited even better erosion rate, erosion depth, and footprint covered than the fan-jet nozzle.     

Selecting the nozzle assortment for a Gantry-type placement machine

Electronics manufacturing systems employ increasingly multi-head gantry machines, where several vacuum nozzles are used simultaneously in pick-and-place operations to insert components on bare PCBs. Their use includes several options that have an impact on the overall manufacturing speed of the machine. In the present paper we address the problem of selecting the nozzles for this kind of a gantry machine, which is an important subproblem of the larger scheduling problem of multi-head gantry machines. Nozzles come in different types, and different types of components may require different types of nozzles in their placing. We address first a case where a single PCB type is manufactured and the only limitation on the number of nozzles is given by the capacity of the placement head. Then we discuss the case where there is a budget limitation on the total cost of the nozzles we can buy. We show that both of these problems can be solved optimally by the means of efficient greedy algorithms. We also discuss the case of selecting nozzles when manufacturing multiple different PCB types.     

包装印刷设备的烘干风嘴分布参数规律研究

目的为了提升包装印刷设备烘干性能,针对风嘴分布进行研究。方法依据实际包装印刷设备风嘴为参考,建立风嘴分布模型并进行非结构网格划分,根据实际情况建立适用于其工况的边界条件和控制方程;控制风嘴间距和承印物距离这2个关键参数,建立风嘴分布参数与热风场性能之间的数学模型;依据所建立数学模型估算不同参数模型的烘干效果。结果根据多组仿真实验得到了风嘴间距和承印物距离等参数对热风场分布的影响,相应经验公式为v (=-0.007×L+2.568)x~(4.311/L+0.056)。风嘴间距对于烘干风嘴影响效果明显,增加风嘴间距离可以提升烘干风嘴风速和热风场的均匀性;同时发现随着承印物不断前进和风嘴作用效果的叠加,其表面风速将持续呈现上升。结论经过研究分析,掌握了不同参数下的热风场分布规律,这对指导实际生产对于烘干风嘴设计具有重要参考价值。     

Effects of welding defects on reducing lifetimes of first stage nozzles of a 123 MW gas turbine made of FSX-414 alloy

In this paper, premature failure of one set of first stage nozzles (stationary blades) in a 123 MW gas turbine has been analyzed. Metallurgical and mechanical experiments showed that the main mechanism for such unexpected cracks is thermal fatigue phenomenon accelerated by presence of welding defects in nozzles. Based on the results, it is recommended that repaired nozzles be thoroughly checked before being re-installed in turbines. Moreover, it is recommended; based on the results; to coat nozzles by corrosion/oxidation resistant coatings after their welding by low chromium filler metals such as L-605.     

Using a multi-phase model to predict flushing of sprayed seal pavements

Flushing is a pavement defect that has a negative effect on the structural integrity and performance of a pavement surface. The aim of this study was to develop a model to predict the occurrence and progression of flushing on sprayed seal pavements. Data analysis and model development were performed using data sourced from New Zealand's Long-Term Pavement Performance programme. The developed model consists of two phases to model (1) the probability of flushing initiating on a pavement and (2) the progression of flushing. The probability of flushing initiation was modelled using a logistic model format, and the progression of flushing was modelled using a linear model format. Testing of the developed model revealed that the logistic model predicted the probability of flushing initiation at 76% accuracy, whereas the linear model had statistically robust predictions of flushing. The developed model is recommended for use in sprayed seal pavement management processes.     

渗透度对锯齿形尾缘喷嘴气动声学影响研究

在低马赫数条件下（Ma=0.12）,采用时间分辨TR-PIV以及远场噪声测量方法,对不同渗透度锯齿形尾缘喷嘴的气动声学特性进行实验研究。流场测量结果表明,锯齿形尾缘喷嘴缩短势核长度,增加势核内气流和周围环境气流的掺混,随渗透度的增加该趋势得到增强。远场声学测量结果表明,随着渗透度增加,锯齿形尾缘喷嘴对于噪声低频降低和高频增加的幅度都有所增强。低渗透度的锯齿形尾缘喷嘴有效降低噪声总声压级,在150°时总声压级降低达到1.3 dB,研究对于降低工厂排空噪声有现实意义。     

基于病毒防控背景下的自助加油站消毒设施设计

目的 在病毒防控的背景下,针对自助加油站的加油枪所设计开发的消毒设施,使每一位自助加油站的用户在不改变原有的使用流程前提下接触到清洁无毒的加油枪,从而在最大限度上阻止病毒在加油站公共区域的交叉传播。方法 利用紫外线消毒技术,将加油枪的外表面充分地消毒杀菌,并在每一次用户使用过后都重复该流程,使得加油枪时刻保持无毒无菌的状态,从而阻绝了病毒在用户之间的传播。结果 经过计算和推演,该设计可以有效的消除加油枪表面的病菌,有效阻隔了病毒的传播途径,与此同时新型设备的介入并没有影响到用户原有的自助加油使用流程,保留了原有的使用体验。结论 该设计在公共卫生领域起到了阻隔病毒传播的作用,对病毒的防御有着深刻而广泛的作用。     

Effects of process parameters on surface morphology of metal powders produced by free fall gas atomization

There are a number of process parameters which affect the characteristics of metal powders produced by free fall gas atomization. In the following work effects of various process parameters like apex angle of atomizer, focal length of atomizer, number of nozzles, diameter of nozzles, diameter of liquid metal delivery tube, superheat of liquid metal and type of metal etc. were studied on their surface morphology. It was observed that shape of powder particles depends on apex angle, superheat of liquid metal, type of metal and particle size range within a powder collective. Other parameters like focal length of atomizer, number of nozzles, diameter of nozzles and diameter of liquid metal delivery tube were found to have no effect on the shape of powder particles. However, Surface porosity and solidification shrinkage were observed on almost all types of metal powders.     

固体火箭发动机喷管用C/C复合材料的研究进展

C/C复合材料已成为固体火箭发动机(SRM)最理想的喷管材料.综述了国内外SRM喷管用C/C复合材料的研究进展、应用状况以及烧蚀性能的研究状况,展望了今后C/C复合材料喷管的发展.     

The influence of nozzle geometry on powder flow behaviors in directed energy deposition additive manufacturing

To show the relationship between the nozzles and the powder flows, computational fluid dynamics and discrete element methods were used to simulate the interactions between the powder particles and the gas flows. Experiment was carried out for the validations. Then, laser irradiation rate (LIR) and powder aggregation degree (PAD) were defined to evaluate the influences of the nozzle geometries on the powder flow behaviors in DED. Results indicate that the divergence angle of the powder stream can be obviously affected by the changes of nozzles. The divergence angle can be increased from 15° with three-jet nozzle to 17° with four-jet nozzle. But at the same work conditions, the divergence angle with annular nozzles is only 8°. The powder mass concentration (PMC), LIR and PAD can be further used for the determination of the stand-off distance in DED. The determined stand-off distance of the annular coaxial nozzle is larger than the three-jet and four-jet nozzles. The PMC is increased by 66.7% in DED with annular coaxial nozzle in comparison with the three-jet and four-jet nozzles. The defined parameters of PMC, LIR and PAD can be used for the systematic determination of stand-off distance for better controlling of DED.