An Experimental Investigation into the Feed Rate Capacity of Rotary Valve and Blow Tank Feeders

Industry widely uses rotary valves and blow tanks for the pneumatic conveying of products, each having their pros and cons depending on the specific application. This article shows the differing results obtained when low-velocity conveying a product through a common pipeline using both a drop-through rotary valve and a bottom-discharge blow tank feeder. A number of issues arise in the rotary valve system, the main one being rotary valve air leakage. A blow tank system, on the other hand, does not leak, as it is an enclosed system. The experimental results show dramatic differences in product throughput. Further exploration leads to a novel modification being made to the rotary valve system in an attempt to increase its capacity. The result of this modification shows a slight increase in output tonnage, but still significantly less than that obtained from the blow tank.     

Prediction of Pressure Drop at the Entry Section from Top Discharge Blow Tank in a Pneumatic Conveying System

Although some literature can be found on the behavior of blow tanks, very few studies could be found on the pressure loss at the entry section to a pipeline (henceforth called entry pressure loss) from a top discharge blow tank in a pneumatic conveying system, even though its magnitude can be significant as compared to the total system pressure drop. This article presents the results of an experimental study carried out to assess this entry pressure loss. The results indicate that it is possible to scale up the entry pressure loss based on laboratory-scale tests with a reasonable degree of accuracy.     

Experimental study on stepless capacity regulation for reciprocating compressor based on novel rotary control valve

A capacity-regulation system based on a novel rotary control valve for reciprocating refrigeration compressor is proposed and designed for the first time. The regulation system is mainly composed of a rotary control valve and an adaptive regulation system. The structure and working principle of the rotary control valve is described in detail, and the control process of the adaptive regulation system for the valve is studied together with the program design. In addition, the parameters for the design and control of the rotary control valve are theoretically determined. To verify the feasibility and effectiveness of the proposed system, a three-cylinder reciprocating compressor was adopted as a test device. Experimental results showed that the technology was able to realize continuous stepless capacity regulation for the compressor within the range of (0)10–100%, and power consumption decreased correspondingly with the load reduction.     

滚动转子式补气压缩机在热泵系统中的实验研究

介绍了滚动转子式补气压缩机的设计,并将其在热泵系统中进行了实验研究。分析了不同制热工况下滚动转子式补气压缩机的性能,对比了带闪发器与过冷器的经济器热泵系统、滚动转子式与涡旋式补气压缩机的性能。结果表明:随着室外环境温度的下降,滚动转子式补气压缩机补气后制热量提升比例逐步增大;滚动转子式补气压缩机制热实验中,带闪发器系统的制热量较高;在超低温制热工况下滚动转子式补气压缩机制热量提升18%左右,与涡旋式补气压缩机相比制热量相当,性能略高。     

Transient and steady-state experimental investigation of flash tank vapor injection heat pump cycle control strategy

Recent research on vapor injection technique has been mostly focused on performance improvement using different system configurations. The flash tank cycle typically shows better performance than the internal heat exchanger cycle. However, the flash tank cycle control strategy is not yet clearly defined. In this study, a novel cycle control strategy is proposed for an R-410A vapor injection flash tank heat pump system and its feasibility was experimentally investigated. The proposed novel cycle control strategy utilized an electronic expansion valve (EEV) for the upper-stage expansion and a thermostatic expansion valve for the lower-stage expansion, and applied an electric heater in the vapor injection line to introduce superheat to the injected vapor by providing a control signal to the upper-stage EEV. Both transient and steady-state system behaviors were studied. The proposed cycle control strategy was found to be able to provide reliable control to the system.     

Numerical simulation of a GM-type pulse tube cryocooler system: Part II. Rotary valve and cold head

A simplified model to characterise a rotary valve is proposed. This model is used inside a complete GM-type pulse tube cryocooler (GMPTC) simulation including the compressor, rotary valve and cold head. The verification of the model is presented including the pressure wave, cooling power and COP by comparing the simulation results to the experimental data of an existing GMPTC system. The exergy losses produced by the compressor, rotary valve and cold head are discussed. This paper is aimed to propose a simulation method which can be applied to analyse and optimise a GMPTC cold head by using the characteristics of a specific compressor and rotary valve.     

Simple integral high vacuum valve

A simple mechanical system is described which enables a vessel to be roughly evacuated by a rotary pump, then by turning a handle through a third of a revolution, the vessel can be evacuated by combined rotary and diffusion pumps. A further turn will allow air into the vessel, and completing one revolution brings the system back to the initial state of being roughed. This is effected by coupling a baffle valve and specially designed rotating plate valve.     

闭式高洁净取注浆机的设计开发

为保证取注浆机在取出和运送过程中金属浆料的洁净度和温度,研发设计了一种由浆罐、浆罐移动系统和机架等3部分组成的闭式高洁净取注浆机,包括方案设计、浆罐移动系统的设计和机架的设计.闭式高洁净取注浆机提高了取注浆过程的安全性、准确性,原料质量处于受控状态,在生产对浆料质量要求较高的压铸件时,闭式高洁净取注浆机可以替代传统的浇汤机,使压铸件产品的质量得到进一步提升.     

Numerical study of solid–liquid two-phase flow and erosion in ball valves with different openings

In the coal chemical industry, petrochemical industry, and other industries, ball valve is a common and important valve due to its reliable structure. The conveying medium has particles that affect the valve surface under the drive of water flow, thereby making the ball valve face the risk of erosion and damage. In this study, the CFD-DEM method was adopted to study the influence of different openings and particle diameters on the two-phase flow and erosion characteristics inside the ball valve. The two-phase flow and particle distribution of the ball valve were analyzed, and the main erosion wall surfaces were determined. The erosion distribution of these walls was obtained. The variation rule of particle number with erosion rate was analyzed, which shows that particle number played a dominant role in erosion degree. Result also showed that in the case of small opening, the erosion decreased with the increase in particle diameter.     

Analysis of Gas-Solids Feeding and Slug Formation in Low-Velocity Pneumatic Conveying

Gas and solids feeding is a key operation in pneumatic conveying of particulate materials. This article presents an analysis of the interfacing effects between a nozzle gas supplier, a rotary valve solids feeder with dropout box, and the pipeline of a pneumatic conveying test rig for low-velocity dense-phase flow. Experiments were carried out to examine the flow pattern of slugs in different combinations of gas flow conditions and solids loading ratios. The effect of gas and solids feeding on the formation of slugs is analyzed by using both experimental data and computer-modeled results. Solids accumulation and sliding motion at the bottom of the dropout box and near the entrance of the downstream pipe, which happen prior to the bulk motion in the form of a slug, are found important in determining the size of a slug. Gas retention and pressure buildup characteristics in the feed section are also found crucial in influencing the flow patterns of slugs.     

膜式燃气表内部流动数值模拟研究

采用CFD数值模拟方法对有柔性膜片的膜式燃气表内部流动进行数值模拟研究,解决了皮膜和旋转阀之间的联动关系以及旋转阀转动与皮膜运动的仿真实现等技术问题;运用滑移网格、动网格及用户自定义函数(UDF)技术实现了膜式燃气表内部流动的动态数值模拟,获得了旋转阀与阀座存在1mm间隙的情况下膜式燃气表内部流场和仪表压损数据.结果表明,数值模拟技术用于膜式燃气表这种复杂结构的内部流动研究是可行的.     

簧片阀流量系数的实验研究与数值模拟

在压缩机簧片阀的数值模拟中,簧片阀的流量系数和相应的有效流通面积是须预先知道的关键参数。一般来说,流量系数和有效流通面积是通过实验测得的。但是,当制冷剂在封闭的系统中流动时,很难测得簧片阀的流量系数。本论文提出了一种思路,建立以空气为工质来测量簧片阀流量系数的模型,同时用静态吹风实验来测量空气的流量系数,得到了空气在不同流量和阀片升程下的流量系数。改变工质为R600a后,模拟计算了簧片阀的流量系数,并通过压缩机整机性能实验对流量系数的正确性进行了间接的验证。结果表明:以空气为工质模拟计算的流量系数与实验结果符合较好,这一模型能够用于计算工质为R600a时的流量系数。     

Flow characteristics and flow rate prediction of pulverized coal through a regulation valve

In this paper, experiments of dense-phase pneumatic conveying of pulverized coal were carried out in an industrial-scale system to study the control characteristics of the regulation valve and to predict the solid mass flow rate. Firstly, effects of valve sweeping gas on conveying stability and solid mass flow rate were investigated and the optimum valve sweeping gas was determined. Second, effects of valve opening on pressure distribution and solid mass flow rate were investigated by conducting experiments at different conveying pressure drops and different valve openings. A good linear relationship between the valve pressure drop ratio and the valve opening was found, and as the valve opening increased from 13 % to 70 % the solid mass flow rate increased gradually. Limit operating conditions of the regulation valve including flow blockage and control failure were consequently determined and analyzed. Finally, a robust model was established to predict the solid mass flow rate by introducing the valve sensitivity coefficient into the traditional pressure drop ratio model. The model can predict the solid mass flow rate well by providing errors mostly within ± 10 %. This study will provide certain reference for solid mass flow rate regulation in the dry coal gasification process.     

Development of capacity modulation compressor based on a two stage rotary compressor – part I: Modeling and simulation of compressor performance

Two-stage rotary compressors are gaining popularity because of their ability to reduce operating and energy costs over the entire compressor life cycle. In this work, a capacity modulation compressor based on a two-stage rotary compressor (CMCTR) is developed to improve the performance of the rotary compressor system. The working principle of the CMCTR is presented and the cycle efficiency of the compressor through two-stage compression is numerically investigated. The CMCTR model considers mass and energy balance for a control volume, the internal leakage condition for all leakage paths, the discharge valve motion, and the force and moment balance. For simulation results, the motor efficiency is estimated with respect to shaft power and the pressure during an entire cycle is obtained with respect to the compression volume for saving mode and power mode. The optimum efficiency of the CMCTR is obtained for the modulation for these modes.     

Valve timing effect on the cooling performance of a 4 K pulse tube cooler

Generally, a compressor together with a rotary valve system generates the pressure oscillation in GM-type cryocoolers. The timing of the rotary valve, which is one of the key operating parameters for cryocoolers, determines the relationship between intake and exhaust processes. A systematic investigation of valve timing effects on cooling performance of a two-stage 4 K pulse tube cooler (PTC) is reported. The experiments show that the optimization of valve timing can considerably improve the cooling performance for both stages. For the same PTC, a performance comparison for operation on different compressors with various input powers ranging from 0.5 to 6.0 kW is also presented.     

Experimental study on the fluidization discharging characteristics of Geldart-C kaolin powders in a blow tank with pulsed gas

Kaolin powders have been suggested to be able to adsorb heavy metal vapor from coal-fired flue gas. However, due to the influence of inter particle forces, such as liquid bridge force, it is difficult to realize stable pneumatic conveying. In the present work, the fluidization characteristics of kaolin powders were investigated. A series of unstable flow phenomena such as agglomeration, channeling, and slugging occurred during the fluidization process. Also, the fluidization discharging characteristics of kaolin powder in an optimized blow tank were experimentally studied. The results indicated that the introduction of pulsed gas can effectively destroy agglomeration and thus improving the stability of discharging. Visual experiments in pseudo-2D fluidized bed were also confirmed the destructive effect of pulsed gas on agglomeration. With an increase in either fluidization gas velocity U_f or pulsed gas velocity v_pulsed, the mass flow rate of kaolin powder G first increased and then decreased. Finally, drying experiments demonstrated that there is free water on the surfaces of the kaolin powders. The analysis of forces indicated that the liquid bridge force F_lb between particles is much larger than the particle gravity F_g. The liquid bridge force might be one of key reasons for kaolin powder agglomerating.     

摆动辗压成形在粉末冶金件生产上的应用

介绍了粉末冶金止推轴承环、NT130汽车后桥差速器行星锥齿轮、冶金齿类零件的生产工艺流程,并对双金属阀座环、铁基双金属止推轴套、铁基双金属轴套（滑动轴承）等典型零件的粉末冶金摆辗成形过程进行了介绍。和其他成形方法相比,通过摆动辗压成形的零件,所需要的成形力大幅度降低,产品能耗和成本明显降低、产品强度提高10％以上。     

摆动辗压成形在粉末冶金件生产上的应用(续)

介绍了粉末冶金止推轴承环、NT130汽车后桥差速器行星锥齿轮、冶金齿类零件的生产工艺流程,并对双金属阀座环、铁基双金属止推轴套、铁基双金属轴套（滑动轴承）等典型零件的粉末冶金摆辗成形过程进行了介绍。和其他成形方法相比,通过摆动辗压成形的零件,所需要的成形力大幅度降低,产品能耗和成本明显降低、产品强度提高10％以上。     

中浓纸浆输送系统储浆罐的自振特性分析

为了研究对中浓纸浆输送系统储浆罐的固液耦合自振特性问题。利用ANSYS软件建立有限元简化模型,采用缩减法对储罐的自振特性进行分析,提取前30阶模态并给出部分模态的三维振型图。结果表明,储罐模态振型呈环向多波形式,罐内中浓纸浆悬浮液的晃动幅度呈中心弱,四周强的趋势。分别采用有限元计算方法和现行标准中理论公式的计算方法对系统固有频率进行求解,发现两种方法计算的结果基本一致,表明文中所建有限元模型是合理的,为该储罐动力分析的进一步研究提供依据。     

Industrial Multi-Plug Conveying Analysis

Single-plug conveying systems have the advantage of being easy to handle and highly controllable. In industry, however, multi-plug conveying systems are the most common choice due to their high transporting capacity. In order to study a multi-plug industrial conveying system, the system parameters were varied along with the materials being conveyed. The responses obtained were compared to the single-plug laboratory system, noting differences and similarities. The pneumatic conveying system at an industrial facility consisted of a 0.01 m Schedule 10 aluminum pipe, approximately 100 m long. To measure the pressure at different points along the system, a total of seven transducers were installed, four air transducers and three flush transducers. This study also used a high-speed video camera to view the plugs as they passed through the transparent viewing port, providing more detailed information on the multi-plug conveying process. Three materials were tested at different superficial air velocities and solid mass flows. In each experiment all transducers took data with a sample rate of 1,000 Hz, giving a highly detailed overview of the conveying process. The analysis included plug velocity and plug size with respect to the superficial air velocity. The Mi model for plug-flow pressure drops was found to yield agreement with the data within ±25%. For this type of industrial operation, this agreement is considered acceptable. The visual observations recorded with the camera showed that there were conditions of stable plug formation as well as varying degrees of plug stability and integrity depending on the operational conditions.