流体动力式空调喷水室的理论与热工性能实验研究

系统地研究了流体动力式空调喷水室的工作原理，该流体撞击式喷嘴具有不易堵塞、容易拆卸且喷嘴雾化参数可调的优点，同时，在建立喷水室简化数学模型的基础上，对喷水室热工性能进行了实验研究，得出了影响喷水量及热交换效率的主要因素及最佳运行工况。实践证明，该喷水室使用效果良好，具有广泛的应用前景。     

自振脉冲喷嘴异形结构对射流冲蚀性能的影响

从提高射流冲蚀效率出发,利用自振脉冲射流对不同形状喷嘴的冲蚀性能进行分析。根据自振脉冲装置结构参数与射流振荡频率之间的关系,建立不同形状的下喷嘴冲蚀性能分析模型;以砂砖为靶件,测量了同等当量面积的圆形和方形喷嘴冲蚀体积和深度,研究冲蚀时间、振荡腔长和靶距对射流冲蚀效果的影响规律。结果表明,随冲蚀时间增加,方形喷嘴的冲蚀体积和冲蚀深度均高于圆形喷嘴,超过最佳冲蚀时间段后方形喷嘴冲蚀深度增长放缓明显。振荡腔长的变化对冲蚀深度影响较大,圆形喷嘴所对应的最佳腔长略小于方形喷嘴。相同工况下,随靶距增大,方形喷嘴冲蚀深度与冲蚀体积的降幅小于圆形喷嘴,前者所对应的冲蚀表面损伤面积大于后者,实验结果与理论分析相一致,所得结论对脉冲射流装置的设计与优化具有参考意义。     

几何参数对引射器及两相流引射制冷系统性能的影响

用两相流引射器代替膨胀阀,可回收两相流引射制冷循环中高压工质的压力能,提高制冷系统效率。对以R134a为工质的两相流引射制冷系统性能进行了实验研究,分析了喷嘴喉部直径和混合室直径对R134a两相流引射器及引射制冷系统性能的影响。实验结果表明,在固定工况条件下,存在使引射比达到最大的最佳喷嘴喉部直径和混合室直径组合。在蒸发温度为3℃、冷凝温度为55℃的工况下,当喷嘴喉部直径为2.0mm、混合室直径为16mm时引射器的引射比最大。在固定工况条件下,使引射比达到最大值的喷嘴喉部直径和混合室直径的最佳组合与使系统COP达到最大值的几何参数组合并不一致。这可能是由于在引射器中产生了激波等因素引起的,其中机理尚需要进行更深入的研究。     

空调超声波喷水室净化PM2.5的研究

通过对比论证的方法，进行了超声波喷嘴雾化机理及除尘性能方面的工作研究，探索了超声波喷嘴的雾化及除尘机理，并就传统喷水室除尘机理和超声波雾化喷嘴的除尘机理两者作了理论对比。为纺织、烟草、矿山等行业在设备的除尘效果及选择方面奠定了基础。     

喷嘴直径对喷砂清理效率的影响

研究以实验为基础，利用回归分析法得喷嘴直径与喷砂清理效率之间的函数关系，为提高砂清理效率提供了理论指导。     

喷嘴结构对水喷射泵抽气效率影响的数值研究

采用FLUENT计算软件,对渐缩型喷嘴和孔口型喷嘴水喷射泵内气液两相流动过程进行了数值模拟。比较了相同工况下两种喷嘴结构水喷射泵的抽气特性,并对水喷射泵内部的水相百分数、速度、湍流动能分布进行了分析。结果表明,在相同工况下,孔口型喷嘴抽吸气体的性能优于渐缩型喷嘴的抽气性能。孔口型喷嘴形成的射流结构有利于与气相的能量交换和组分混合,渐缩型喷嘴的湍流分布不利于能量交换,大量的能量耗散是其抽吸气体效率下降的主要原因。对水喷射泵内部两相流动过程进行数值模拟分析,不仅可以加深水喷射泵抽气机理的理解,还为水喷射泵的抽气效率提高和优化设计提供了一定的参考。     

布袋除尘器应用中的优化

LKPN-2＊6＊387—8型布袋除尘器是专门为燃煤电厂干法脱硫系统设计的脱硫后置布袋除尘器，它的运行工况直接影响除尘效率及脱硫工况稳定，实际运行中存在气流不均，内部旁路档板密封不严，仪用气不可靠等问题，采用除尘器人口加装气流分布板、密封风机加装进、出口阀门，内部旁路档板加装槽钢、仪用储气罐加装伴热带一系列优化措施后，除尘器内部气流分布均匀，旁路密封严密，提高了除尘效率及滤袋使用寿命，保证工况稳定。     

开启式压缩机两种工质变转速工况下容积效率的实验研究

选用某种容积式压缩机在变转速工况下进行了两种工质压缩机的性能实验,得出了不同工况(压缩比)对容积效率的影响以及转速变化的影响,存在一个最佳转速或转速范围使容积效率达到最大值.用实验数据拟合出了两种工质压缩机变转速工况下的容积效率关联式,计算结果与实验数据的平均误差在5%以内,拟合公式具有一定的可信度.     

喷射器极限工况特性实验研究

喷射器作为热驱动喷射式制冷系统的核心部件,其性能会影响整个制冷系统的运行效率。极限工况是指喷射器从可以工作状态到不能工作状态的极端工况,对该工况下喷射器的特性研究具有重要意义。本文自行设计并搭建了以R134a为制冷剂的喷射式制冷系统极限工况的实验装置,分别对引射流体质量流量为零的极限工况下不同喷射器工作流体压力及喷射器出口背压对缩放喷嘴出口背压的影响规律进行了实验研究。结果表明:极限工况下,喷嘴出口背压同时受工作流体压力和喷射器出口背压的影响,随工作流体压力升高而降低,随喷射器出口背压升高而升高。同时,得到该喷射器在工作流体压力为1.5~3.2MPa,且喷射器出口背压在0.66~0.96 MPa范围内的最低引射流体压力,为工程应用提供参考。     

二次纤维新闻纸最佳实地密度的研究

本课题的目的是寻找二次纤维新闻纸的最佳印刷实地密度的实验方法,实现对彩色报纸印刷品图像再现质量的控制.分析了实地密度与图像再现的关系,根据印刷相对反差和色彩反差与实地密度的间接关系,求出二次纤维新闻纸的最佳实地密度范围.研究结果表明:实地部位的密度和色彩与网点覆盖率为共同构成影响报纸印刷图像再现质量的主要因素.     

Enhancement of Particle Removal Performance of High-speed Air Jet by Setting Obstacle in Jet Flow

Surface cleaning using high-speed air jet can be applied to cleaning of an object with concavo-convex shape. In such cases, the distance between the air jet nozzle and the surface becomes on the order of cm. An increase in the distance causes a decrease of the air velocity at the surface resulting in deterioration of the particle removal performance of the air jet. Therefore, a method to enhance removal efficiency is required. In this study, we investigated two methods for the enhancement of removal efficiency: one is to set a wire in the air flow and the other is to set two cylindrical rods. Although the wire set at the center of the jet flow deteriorates the removal efficiency, experimental results imply that the wire has a positive effect on the efficiency when it is set at a position where it does not interfere with the main flow of the jet. On the other hand, when two cylindrical rods are set at a theoretical periphery of the air jet, it shows clearly an enhancement in removal efficiency. This fact implies that the removal efficiency can be enhanced by controlling flow fluctuation by means of setting an obstacle.     

Numerical simulation on adsorbent injection system for mercury removal from coal-fired flue gas

Optimizing the injection system significantly reduces the cost of adsorbent injection technology for mercury removal from coal-fired flue gas. In this work, the effects of three common injection system layouts, namely single-sided four-way pipe (SFP), quadtree (QT), and long to short (L-S), on adsorbent particle concentration, mercury concentration, and mercury removal efficiency were systematically investigated by simulation calculation. It shows adsorbent coverage, and particle concentration standard deviation coefficient at the initial injection satisfies SFP > QT > L-S. The number of nozzle and injection directions affect the distribution of adsorbent particle concentration. The apparent mercury removal occurs within 2 s after adsorbent injection. The SFP arrangement has the best average coverage rate of adsorbent (86.86%), average standard deviation coefficient (2.40), and mercury removal efficiency (60.12%). The coupling degree between particle concentration and flue gas mercury concentration field is essential in determining mercury removal performance.     

Aerosol Sampling Efficiency in a Model Room

The sampling process of a model room with a suction nozzle in a calm or low movement environment was numerically simulated and experimentally analyzed. Computational fluid dynamics (CFD) software, Fluent (Fluent Inc.), was used for the numerical simulation. The flow was considered to be compressible and turbulent, and particles were considered to be spheres of constant density. A good agreement was found between the numerical and experimental results (maximum difference of 15% in the overlapping zone), and the numerical model was further extended and used for parametric analysis. The influence of sampling velocity and shape of the suction nozzle on sampling efficiency was investigated experimentally and numerically in a particle size range of 2–45 µm. It was found that sampling efficiency is smaller for V-shaped nozzles, mainly for lower velocities. Sampling efficiency was calculated for each particle diameter and for the whole particle size distribution as well. Sampling efficiency decreases as particle size increases. It is concluded that knowledge of sampling efficiency for each of the sampled particle sizes may indicate the concentration and size distribution in the sampled space.     

Observation Evaluation of Nozzle Clogging in a Micro-orifice Impactor Used for Atmospheric Aerosol Sampling

A micro-orifice impactor uses micro-orifice nozzles to extend the cut sizes of the lower stages to as small as 0.18 μm in diameter without resorting to low pressures or creating excessive pressure drops across the impactor stages. In this work, the phenomenon of nozzle clogging caused by particle deposition was investigated experimentally for a commercial micro-orifice uniform deposit impactor (MOUDI, MSP model 100). Using an optical microscope, we observed that the micro-orifice nozzles of the lower three stages were partially clogged due to particle deposition during the atmospheric aerosol sampling. To examine the effect of nozzle clogging on the performance of the impactor, the pressure drop and the particle collection efficiency were evaluated for the lower three stages. The pressure drops across the clogged nozzles were higher than the nominal values given by the manufacturer. The particle collection efficiency of each stage was evaluated by using an electrical method for fine particles with diameters in the range of 0.1-0.6 μm. Monodisperse liquid dioctyl sebacate (DOS) particles were used as test aerosols. A Faraday cage was employed to measure the low-level current of the charged particles upstream and downstream of each stage. The collection efficiency curves shifted to correspondence to smaller orifice sizes, and the 50% cutoff sizes were much smaller than those given by the manufacturer for the three stages with nozzles less than 400 μm in diameter.     

Aerosol Sampling Efficiency in a Model Room

The sampling process of a model room with a suction nozzle in a calm or low movement environment was numerically simulated and experimentally analyzed. Computational fluid dynamics (CFD) software, Fluent (Fluent Inc.), was used for the numerical simulation. The flow was considered to be compressible and turbulent, and particles were considered to be spheres of constant density. A good agreement was found between the numerical and experimental results (maximum difference of 15% in the overlapping zone), and the numerical model was further extended and used for parametric analysis. The influence of sampling velocity and shape of the suction nozzle on sampling efficiency was investigated experimentally and numerically in a particle size range of 2-45 µm. It was found that sampling efficiency is smaller for V-shaped nozzles, mainly for lower velocities. Sampling efficiency was calculated for each particle diameter and for the whole particle size distribution as well. Sampling efficiency decreases as particle size increases. It is concluded that knowledge of sampling efficiency for each of the sampled particle sizes may indicate the concentration and size distribution in the sampled space.     

Removal of Nano-sized Particles Using Carbon Dioxide (CO2) Gas Cluster Cleaning without Pattern Damage

As pattern size of semiconductor device becomes less than 20 nm, the removal of particles smaller than 10 nm without pattern damages requires new physical dry cleaning technology. CO₂ gas cluster cleaning is an alternative dry cleaning process to meet these cleaning requirements. To demonstrate gas cluster cleaning performance, particle removal efficiency (PRE) and gate structure pattern damages were evaluated. When pressurized and low temperature CO₂ gas was passed through a convergence–divergence (C–D) nozzle, high energy CO₂ gas clusters were generated at high speed in a vacuum atmosphere. The cleaning force of the CO₂ gas cluster is related to the flow rate of the CO₂ gas. The optimum CO₂ gas flow rate for the particle removal without pattern damage was found to be 6 L/min (LPM). Removal efficiency for 50 nm silica particles was greater than 90%, and no pattern damage was observed on 60 nm poly-Si and a-Si gate line patterns. It was confirmed that the CO₂ gas cluster cleaning force could be controlled by the CO₂ gas flow rate supplied to nozzle.     

Advances in Particle Removal without Damage

Particle removal without damage to sensitive device structures on semiconductor devices is a necessary process to maximum device yield. The use of an atomized aerosol spray for damage-free particle removal has proven to be one of the more effective strategies. Continued improvements in nozzle design have enabled the use of this technique to 1Xnm technology nodes. Recently, the freezing of water has also shown promise for damage-free particle removal, and the performance of this new technique is compared with aerosol spray cleaning.     

Design and Evaluation of Four-Stage Low-Pressure Cascade Impactor Using Electrical Measurement System

The low-pressure cascade impactor has been used to collect ultrafine particles that cannot be measured by conventional cascade impactors. Low-pressure cascade impactors resemble ordinary impactors, but are operated at reduced pressures of 0.05 ～ 0.4 atm. Many kinds of low-pressure impactors have been developed by different researchers. However, it is still difficult to accurately design and evaluate the low-pressure cascade impactor.

In this study, a four-stage low-pressure cascade impactor for measuring the size distribution of submicron aerosol particles was designed and evaluated. To evaluate particle collection efficiency of each stage, an electrical measurement system was used. The cut-point diameters of Stages 1 through 4 were 0.238, 0.173, 0.111, and 0.063 μm in aerodynamic diameter. Stage 2 showed poor steepness of the collection efficiency curve and larger cut-point Stokes number than theory, which may be attributed to high nozzle velocity. The fluorometric method for particle collection efficiency measurement was shown to be unreliable for ultrafine particles.

The solid particle collection efficiency of the designed impactor was examined with different substrate conditioning methods. Porous metal substrate and silicon-coated substrate were tested with NaCl particles. It was shown that silicon coating did not effectively reduce the particle bounce because of high nozzle velocity, whereas the porous metal substrate considerably enhanced the particle collection efficiency.     

Design and Evaluation of Four-Stage Low-Pressure Cascade Impactor Using Electrical Measurement System

The low-pressure cascade impactor has been used to collect ultrafine particles that cannot be measured by conventional cascade impactors. Low-pressure cascade impactors resemble ordinary impactors, but are operated at reduced pressures of 0.05 ∼ 0.4 atm. Many kinds of low-pressure impactors have been developed by different researchers. However, it is still difficult to accurately design and evaluate the low-pressure cascade impactor.

In this study, a four-stage low-pressure cascade impactor for measuring the size distribution of submicron aerosol particles was designed and evaluated. To evaluate particle collection efficiency of each stage, an electrical measurement system was used. The cut-point diameters of Stages 1 through 4 were 0.238, 0.173, 0.111, and 0.063 μm in aerodynamic diameter. Stage 2 showed poor steepness of the collection efficiency curve and larger cut-point Stokes number than theory, which may be attributed to high nozzle velocity. The fluorometric method for particle collection efficiency measurement was shown to be unreliable for ultrafine particles.

The solid particle collection efficiency of the designed impactor was examined with different substrate conditioning methods. Porous metal substrate and silicon-coated substrate were tested with NaCl particles. It was shown that silicon coating did not effectively reduce the particle bounce because of high nozzle velocity, whereas the porous metal substrate considerably enhanced the particle collection efficiency.