共查询到20条相似文献，搜索用时 265 毫秒
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本文对送风口径可调的圆盘形散流器进行了实验研究,该散流器呈倒蘑菇形,设计有不同开口高度对应的三档扇叶位置。本文分别对各出风位置进行不同风量下常温射流特性实验和压力特性实验,比较了不同高径比和净面积比下散流器的最大中心速度、射程、全压损失的变化情况。实验结果表明:开口高度设在最小的档位时向下射流,最大中心速度下降快,全压损失大,风量对扩散半径影响很小。随着开口高度增大,风口变为水平送风,射流最大中心速度随开度的增大下降减慢,全压损失减小,到达一定开口高度后,射程几乎不受风量的变化影响。该圆盘形散流器可在高大空间中满足输送冷、暖风所需的不同送风方式。 相似文献
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卢义玉 《重庆大学学报(英文版)》2002,1(1):11-15
A new type jet, the oscillating & deflecting jet, is put forward and its oscillating and deflecting characteristics are investigated. The nozzle of the self-oscillating & deflecting water jet consists of an upstream nozzle, a downstream nozzle, an oscillating chamber and two switches. It is experimentally shown that the deflective angle may reach 9.53 degree. The generated pressure fluctuation is very regular and the jet can efficiently increase the ability for breaking and cutting by eliminating the water cushion effect associated with a continuous jet. 相似文献
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为研究微小孔径气体受限冲击射流的换热特性,采用电阻丝加热方形酚醛树脂薄板作为模拟发热芯片的换热表面,沿对角线均匀布置热电偶以采集表面温度分布。以3mm孔径的圆形单孔及1mm孔径两种不同排列的圆形多孔喷射板对发热面进行中低Re数的射流冲击换热实验．通过改变风数及高度孔径比等参数得到了批数的径向分布及驻点区的换热特性,为射流冲击换热在封装芯片冷却上的应用提供了实验基础。 相似文献
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Mathematical model for abrasive suspension jet cutting based on orthogonal test design 总被引：2，自引：0，他引：2
This paper describes the application of orthogonal test design coupled with non-linear regression analysis to optimize abrasive suspension jet (AS J) cutting process and construct its cutting model. Orthogonal test design is applied to cutting stainless steel. Through range analysis on experiment results, the optimal process conditions for the cutting depth and the kerf ratio of the bottom width to the top width can be determined. In 'addition, the analysis of ranges and variances are all employed to identify various factors: traverse rate, working pressure, nozzle diameter, standoff distance which denote the importance order of the cutting parameters affecting cutting depth and the kerf ratio of the bottom width to the top width. Furthermore, non-linear regression analysis is used to establish the mathematical models of the cutting parameters based on the cutting depth and the kerf ratio. Finally, the verification experiments of cutting parameters' effect on cutting performance, which show that optimized cutting parameters and cutting model can significantly improve the prediction of the cutting ability and quality of ASJ. 相似文献
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The effects of the vortex generator jet(VGJ)attached at the endwall on the corner separation/stall control are investigated by numerical simulation in a high-turning linear compressor cascade. The results show that the corner separation could be reduced significantly, which results in a wider operation range as well as a more uniform exit flow angle and total pressure profile. At the near-stall operation point, the maximum relative reduction of the total pressure loss is up to 32.5%,, whereas the jet mass ratio is less than 0.4%,. Based on the analysis of the detailed flow structure, three principal effects of the VGJ on the endwall cross flow and corner separation are identified. One is to increase the tangential velocity component opposite to cross flow, thus inhibiting the endwall secondary flow near the jet exit. The second is to suppress the pitchwise extension of the passage vortex as an air fence. The third is to sweep the low energy fluids towards the mainstream on the up-washed side and to transport the mainstream fluids to the endwall to reenergize the boundary layer on the down-washed side. 相似文献
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喷嘴是水射流切割系统的关键元件，通过研究一级喷嘴直径、二级喷嘴直径、混合腔直径和喉管距、系统工作压力、磨料直径大小等对轴向射流速度的影响，为水切割喷嘴的优化设计奠定了基础，其结果可为高压水切割工具的设计提供参考依据。 相似文献
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实验室利用差压传感器测量空气相对压力系数时,真空泵的抽真空度对于实验结果有很大的影响。实验采用控制变量法,对真空泵抽真空度这一影响因素进行了研究。结果表明,真空泵抽真空程度越高,测量所得空气相对压力系数值越小,并且越接近其真实值,空气相对压力系数测量值的改变量随真空度的增大而不断减小,二者之间呈现出一条斜率渐渐减小的曲线关系。真空泵无法完全抽真空时,可以通过将最终测得的空气相对压力系数值乘以其对应真空度值的方法对实验结果进行修正。 相似文献
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王从东 《淮南职业技术学院学报》2009,9(3):22-24
将声音信号特征技术应用于高压水射流切割效能判断,利用水射流设备、Labview和M atlab软件搭建了高压水射流切割声音信号采集和分析系统;实验结果表明,采用声信号对高压水射流切割效能进行判断是可行的。 相似文献
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分析了4类风口模型（即基本模型、盒子模型、N点动量模型、主流区风口模型）在计算流体动力学中的应用以及在实际工程案例中的运行情况.在环境舱内进行了足尺实验,利用全方位热风速表测量了环境舱内的气流速度和温度场,并与4类风口模型的模拟结果进行比较.结果表明：基本模型与盒子模型并不适用于结构复杂的送风口模拟;基于N点动量模型和主流区风口模型的流体速度在工作区的模拟值与实测值的相对误差小于20%;在主流区风口模型中,送风口附近的气体速度模拟值与实测值的最大相对误差小于15%.证明主流区风口模型相对于其他3类风口模型而言,对于结构复杂的送风口模拟更准确,应用性更强. 相似文献
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从熵态视角对空调负荷进行划分,基于双温冷源空调系统基础上,根据不同新风处理方法,探讨设计参数选取及负荷计算。通过系统优化遵循“高熵负荷用高温冷源消除,低熵负荷用低温冷源消除”的原则,除高温冷源降温外,提出串联高、低温冷源的除湿循环,建立双温冷源能耗模型,数值模拟计算得到最佳除湿、除热冷源有效温度。 相似文献
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The low temperature plume exhausted from a cryogenic wind tunnel may sink down, posing a severe threat to public health and safety. Quantitative risk assessment of cryogenic plume flow behavior therefore plays an important role in the design and optimization of a cryogenic wind tunnel. A numerical model with a modified Hertz-Knudsen relation considering the phase change physics of the small quantity of water involved is applied to analyze the dispersion of the low temperature nitrogen plume exhausted from a 0.3 m cryogenic wind tunnel. The homogeneous multiphase flow is modeled using the single-fluid mixture model. A model validation is presented for the exhaust plume from the US National Transonic Facility (NTF). The predicted results are found to be better than those predicted by National Aeronautics and Space Administration (NASA)’s two-stage analytical model. The influences of the environmental wind speed, the environmental wind temperature, the relative humidity, and the exhaust flow rate, on low temperature nitrogen plume dispersion are obtained. In particular, the parametric sensitivities of different influence factors are analyzed. The environmental wind temperature and the exhaust flow rate of the nitrogen gas have greater impact on the temperature of the plume near the ground than do the environmental wind speed and the relative humidity. The exhaust flow rate of the nitrogen gas has greater impact on the oxygen concentration near the ground than does the environmental wind speed, while the environmental wind temperature and the relative humidity have negligible impacts. The results provide guidance on the operation and design improvement of a cryogenic gaseous nitrogen discharge system to avoid its potential hazards. 相似文献
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Reaction thrust of water jet for conical nozzles 总被引：1，自引：0，他引：1
Clear knowledge on the reaction thrust of water jet is valuable for better design of water jet propulsion system. In
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions． 相似文献
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions． 相似文献
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Computational fluid dynamics simulation of formaldehyde emission characteristics and its experimental validation in environment chamber 总被引：1，自引：0，他引：1
We investigated the effect of supply air rate and temperature on formaldehyde emission characteristics in an environment chamber. A three-dimensional computational fluid dynamics （CFD） chamber model for simulating formaldehyde emission in twelve different cases was developed for obtaining formaldehyde concentration by the area-weighted average method. Laboratory experiments were conducted in an environment chamber to validate the simulation results of twelve different cases and the formaldehyde concentration was measured by continuous sampling. The results show that there was good agreement between the model prediction and the experimental values within 4.3% difference for each case. The CFD simulation results varied in the range from 0.21 mg/m3 to 0.94 mg/m3, and the measuring results in the range from 0.17 mg/m3 to 0.87 mg/m3. The variation trend of formaldehyde concentration with supply air rate and temperature variation for CFD simulation and experiment measuring was consistent. With the existence of steady formaldehyde emission sources, formaldehyde concentration generally increased with the increase of temperature, and it decreased with the increase of air supply rate. We also provided some reasonable suggestions to reduce formaldehyde concentration and to improve indoor air quality for newly decorated rooms. 相似文献
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研制了一种温差电效应发电演示热功小车,演示了从热能到电能再到机械能的能量转换过程。该小车以温差发电为电源,利用珀尔帖片、散热片与酒精灯构成核心组件,由酒精灯加热下散热片,下散热片将热量集中到珀尔帖片,珀尔帖片通过上散热片散热,维持珀尔帖片冷热两面有较大温差,输出电能驱动电机旋转,电机带动小车跑动。该小车结构简单,工作原理明晰易懂,运动速度达15 cm/s,演示结果达到了引起人们对温差发电的关注和研究的目的。 相似文献
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二氧化碳低温制冷循环分析 总被引：1，自引：1，他引：0
钱怀洲 《顺德职业技术学院学报》2010,8(2):7-9
对两种不同的二氧化碳双级压缩低温制冷循环进行了分析．得到在一定的蒸发温度和冷却器出口温度下．一次节流不完全中间冷却二氧化碳双级压缩循环COP较大、最优冷却压力较低、具有良好的发展前景。 相似文献
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为了改善超高强度钢的塑韧性,实验分析了奥氏体化温度分别为840℃、880℃、920℃与等温温度分别为275℃、325℃、375℃对中碳超高强度钢组织性能的影响．结果表明,随着奥氏体化加热温度的升高,贝氏体/马氏体复相组织趋向粗大,钢的强度上升,而塑韧性下降;随着等温温度的升高,钢的抗拉强度呈平缓下降趋势,而钢的塑韧性在275～325℃等温温度范围内呈上升趋势,在325～375℃等温温度范围内呈下降趋势．在试验等温处理温度范围内,奥氏体化温度880℃×30min保温＋等温温度325℃×2min保温油冷,可获得强韧性配合良好的贝氏体/马氏体复相组织,钢的残余奥氏体的含碳量≥76．％,钢的抗拉强度Rm≥2065M Pa ,断面收缩率ψ≥255．％． 相似文献