Traditional Baffle Research Articles

Influence of combinational distortion generator geometrical parameters on the steady and dynamic components of the total pressure distortion

To construct a method for designing a total pressure distortion generator with adjustable, steady, and dynamic components, we experimentally investigated the influences of combinational distortion generator geometrical parameters on the steady and dynamic components of the total pressure distortion based on an indraft wind tunnel. Different types of annular plates and cylindrical rods were installed upstream of a traditional baffle total pressure distortion generator; the total pressure distortion was then measured using rotatable total pressure rakes. The installation of cylindrical rods upstream of the baffle plate could maximally reduce the ratio of steady and dynamic components of total pressure distortion by 30%. Increasing the number and height of the rods, as well as the axial distance between the rod and baffle plate, were effective methods of reducing the steady components of total pressure distortion. Similarly, changing the geometrical parameters of the annular plate was also an effective method for adjusting the ratio of steady and dynamic components of total pressure distortion. The ratio of the steady and dynamic components of total pressure distortion first experienced a decrease and then increased variance law with the increase in the height and circumferential scale of the annular plate. During this procedure, the steady and dynamic components ratio of total pressure distortion could be maximally reduced by 24% and maximally increased by 20%.

Effects of longitudinal excitation on liquid hydrogen sloshing in spacecraft storage tanks under microgravity conditions

Based on the real physical model and operating environment of the spacecraft tank, the numerical model of the tank is established and the sloshing behavior of liquid hydrogen in the tank under different longitudinal excitations is studied in this work. The Realizable k- ε model is used to predict the fluid turbulence, and the mixture model is used to analyze the phase transitions and flows. The harmonic external excitation is loaded by the user-defined function (UDF). Based on the CFD sloshing model verified through comparison with experimental results, the influences of different longitudinal external excitation frequencies and amplitudes on the liquid hydrogen volume fraction in the tank are firstly analyzed. On this basis, including pressure and other physical quantities of the monitoring points and whole internal fluid domain during the sloshing simulation process are studied quantitatively. In addition, the relationship between the carrier amplitude of the sloshing curves and the external excitation amplitude is discussed. The simulation results show that in microgravity environment, compared with large amplitude excitation, high-frequency longitudinal harmonic excitation has a significant effect on the variation of physical parameters in the tank, which may become a negative factor for the safety of liquid hydrogen storage and supply systems. Meanwhile, the traditional baffle design has a limited influence on the liquid hydrogen motion under the high-frequency longitudinal excitation which may occur during the spacecraft changing load process. The results provide valuable information for the understanding of sloshing behavior and safety evaluation of the tank under longitudinal excitation.

Reduced power consumption in stirred vessel with high solid loading by equipping punched baffles

Solid–liquid suspension in stirred tank is a common operation in the chemical industry. The power consumption, flow pattern and flow field instability of three systems named as unbaffled stirred tank, traditional baffled stirred tank and punched baffled stirred tank (Pun-BST) were studied by using the computational fluid dynamic analysis. Results showed that perforating holes in the baffles could reduce power consumption of mixing. Meanwhile, the punched baffle system could maintain the solids in suspension as traditional baffle system. The results also showed that the baffles could increase the “effective flow” of stirred tank even though the whole velocity of the vessel is lower than un-baffled vessel. In addition, both the solid–liquid suspension and “effective flow” were related to instability of the flow field. Perfect solid–liquid suspension results always along with obvious instability of the flow field. But, the strengthening effect of punched baffle on flow field instability mainly happened in the near-wall area. It’s because the collision and aggregation among sub-streams induced by holes intensified the unstable fluid flow. On the whole, the Pun-BST system provided much better mixing characteristics and recommended to apply in the industrial process.

PRIMER PROTOTIPO DE TRAMPA FRÍA CON PASANTE ELÉCTRICO PARA VACÍODE BAJO COSTO

n a previous work, Conde Garrido and Silveyra proposed a novel cold trap (baffle) technology capable of trapping contaminants in vacuum systems. The baffle was designed to be applied in systems to synthesize chalcogenide glass thin films by pulsed laser deposition. While traditional baffles are cooled down with compression cooling systems or cooling solutions such as liquid nitrogen, the reported baffle is cooled down by the thermoelectric effect, which allows for reducing the capital investment, operating costs, as well as start-up and maintenance times. This paper presents the construction, tuning, and characterization of the first physical prototype of the baffle. The characterization included, first, the control of the final pressure reached by the device. To characterize the thermal performance of the baffle, a temperature measurement system was designed and manufactured. Within this measurement system, we highlight a low-cost electric vacuum feedthrough. The results indicate that the constructed baffle can reach pressures lower than 2×10−5mbar, while the cold surfaces reach temperatures of approximately−12◦C. The vacuum and cold temperature levels meet the required conditions for the pulsed laser deposition of chalcogenide glass thin films. However, temperatures are not as low as those estimatedfor the virtual prototype (down to−50◦C). Thermal bridges and resistances present in the fabricated device, neglected in the model, were then identified, pointing out opportunities for improvement. Finally, revisions to the current design are proposed that simplify its manufacturing process, improve its robustness and efficiency, and facilitate its operation and maintenance.

Experimental Evaluation of Tubular Flocculator Implemented in the Field for Drinking Water Supply: Application in the Developing World

The purpose of this study was to evaluate the efficiency of a large-scale Horizontal Tubular Flocculator (HTF) as an easy-to-implement technology for potable water provision compared to the efficiency of a traditional baffle flocculator. The HTF was built with a 4-inch diameter PVC pipe and coupled to a sedimentation and filtration process. Experimental tests were performed using lengths of 68.4 m and 97.6 m for the HTF. These lengths were combined with raw water flow rates of 0.25, 0.5, 0.75, 1, and 2 L/s and five turbidity ranges <10 NTU, 10–20 NTU, 21–50 NTU, 51–100 NTU, >100 NTU, giving a total of 100 tests for one year. Jar tests were performed to determine the optimal dose of aluminum sulfate used as a coagulant. Hydraulic characteristics such as time of retention (TR) and velocity gradient (G) were evaluated; likewise, plug flow, dead volume, and short-circuit ratios were determined by tracer tests using the Wolf–Resnick model. The average results determined a removal of 98.8% of turbidity and 99.93% of color. The TR varied between 4.62 and 36.97 min and G varied between 6.15 and 109.62 s−1. The results showed that HTF can be useful as a flocculation unit in a purification system.

A Methodological Study on the Design Defending Baffles Based on Mangrove Bionics

In terms of the failure of giving considerations to both aesthetic ornamental and low-carbon function for the current disaster prevention and mitigation engineering. This study proposes the debris-disaster prevention baffles applicable to natural scenic areas which designed based on mangroves properties, to solve this problem by adopting bionic design method. The research methodology is as follows: (1) To propose a Six Elements and Ten Steps Design Method for extracting the critical bionic elements of mangrove plants that contributes to the prevention of winds and waves. (2) To construct a decision objective model based on the Analytic Hierarchy Process method (AHP). Prioritize the critical bionic design elements and build a geometric structure model. (3) To compare the disaster mitigation performance through numerical simulations, and thus select an optimal one for further studies. (4) To design the final disaster prevention product based on the above theoretical guidance, low-carbon concept, efficient protection orientation, and environment-friendly principles. This study indicates that the use of bionic design satisfies aesthetic ornamental, and low-carbon demands. The appliance of AHP avoids subjective one-sidedness in design process when considering the priority of bionic elements. The numerical simulation experiments adopted in this study aim to compare the blocking effect of different baffle models and achieve the optimization the performance in disaster prevention of traditional baffle groups. In this study, the bionic product design methodology is adopted for baffle design to solve existing aesthetic and environmental problems. The particle accumulation mass after the new baffles can be effectively reduced by 2–3 times compared to the traditional baffles. Furthermore, the new baffle is more aesthetically pleasing than the traditional ones.

Study on instability strengthening of flow field in stirred tank

BackgroundLow-frequent instabilities within flow pattern of stirred tank (ST) which well-known as macroinstability (MI) further as “flow field instability” has significant additional effect to common turbulence concerning effectivity of mixing process. MethodsIn this work, numerical simulation methods were used to study the impact of baffle on flow field instability. Significant FindingsThe results showed that flow field instability in baffled stirred tank (BST) was full of global tank compared with unbaffled stirred tank (Un-BST), and the instability of near baffle zone was stronger than that in near impeller zone. By comparing the power consumption in ST equipped with different structure baffles, find that the punched baffle stirred tank (Pun-BST) and isolated baffle stirred tank (Iso- BST) system have lower power consumption than the traditional baffle stirred tank (Trad-BST) system. Also, the degree of global instability decreased partly. In addition, the instability intensity of near baffle zone in the Pun-BST system was lifted locally, and the maximum increase can be as much as 4 times, compared with Un-BST.

New baffle design and analysis of long-wave infrared camera

A structure of suppressing stray light of space-based infrared optical system was designed. In order to reduce the internal radiation, reflective baffles and traditional baffles were designed. The system of reflective baffles described here consist of vanes whose outward facing surfaces are ellipsoids and whose backward facing surfaces are hyperboloids of one sheet. Software tracepro was also used to build the system model and simulate analysis of the system. According to the simulated dates, the PST curve was drawn. The results indicate that stray light off axis was well suppressed. Thermal radiation of the system respectively at different temperature were also simulated. When the temperature was down below 115 K, the illumination of target that gets to imager is an order of magnitude higher than the internal thermal radiation that gets to imager. The results indicate that thermal radiation was also well suppressed.

Influences of flow rate and baffle spacing on hydraulic characteristics of a novel baffle dropshaft

Due to limited flow capacity and the instability of the asymmetric structure of traditional baffle dropshafts, a novel baffle dropshaft with a symmetric structure, adopting the construction shield well directly, is proposed for large-range flow discharge in deep tunnel drainage systems. In this study, a two-phase flow field of the novel baffle dropshaft with three different baffle spacings was simulated at seven different flow rates with a three-dimensional (3D) numerical model verified with experiments, to study hydraulic characteristics of this novel baffle dropshaft. The results show that the novel baffle dropshaft has a remarkable energy dissipation effect. Baffle spacing of the novel baffle dropshaft has a greater effect on flow patterns and baffle pressure distributions than the comprehensive energy dissipation rate. Flow rate is a critical issue for the selection of baffle spacing in the design. Some guidance on baffle spacing selection and structure optimization for the application of this novel baffle dropshaft in deep tunnel drainage systems is proposed.

Investigation of the flow characteristics of liquid–liquid two-phase mixing in an agitator equipped with a “V-shaped” horizontal baffle

An agitator is an important operating unit in industrial production, and baffles play a vital role in the performance of the agitator. Compared to the performance of unbaffled agitators, traditional baffles can break vortices and improve the mixing in a stirred tank, but traditional baffles can also contribute to high energy consumption. A newly invented “V-shaped” horizontal baffle is introduced based on a traditional baffle, and the new baffle is attached to the inner wall of the agitator at the height of the impeller. Based on several different baffle conditions (an agitator without the “V-shaped” horizontal baffle and agitators with “V-shaped” horizontal baffles at angles of 30°, 60° and 90°), the fluid flow characteristics of the liquid–liquid two-phase flow mixing process are investigated by the computational fluid dynamics (CFD) method. The multiple reference frame method, the standard k − e model and the Eulerian–Eulerian two-fluid model are adopted. The “V-shaped” horizontal baffle is found to reduce energy consumption and improve mixing, which provides new approaches for the optimization and innovation of baffles.

Numerical investigation of effects of “baffles - deceleration strip” hybrid system on rock avalanches

Arrays of baffles are usually installed in front of protection site to attenuate the flow energy of rock avalanches in mountainous areas. Optimization design is crucial for efficiency promotion in hazard energy dissipation engineering. In this study, a deceleration strip was added in the baffles protection system to optimize the traditional baffles system. The effects of the "baffles - deceleration strip" hybrid protection system was discussed in detail with the nails number and nails angle. This study presents details of numerical experiments using the discrete element method (DEM). The effect of the optimization of hybrid protection system (nail angle and nail number) were investigated specifically, especially the impact force that avalanches exerted on structures. The results show that the maximum impact forces and kinetic energy of the rock avalanches decreases with the increase of the number and angle of the nail. Moreover, the distance between the toe and the bearing structure (L-m) is also a key factor. The shorter the distance L-m (30m) is, the higher the maximum impact force are. The longer the distance L-m (70m) is, the lower the maximum impact force are. Under the same size of the nails, increasing the numbers can enhance the dissipation ability of the hybrid protection system. Meanwhile, increasing its angle can also enhance the dissipation ability. There are three key ways for nails attenuate rock avalanches: (i) block the fine particles directly; (ii) form the particles bridge between nails and baffles; (iii) dissipate the coarse particles energy directly. The effect of segregation in rock avalanches is crucial for the energy dissipation mechanism, which is a key factor to optimize the traditional baffle system.

Abstract 14364: Hemodynamic Evaluation of 30 Y-Graft Fontan Completions

Background: Fontan completion, resulting in a total cavopulmonary connection (TCPC), is accomplished using either a traditional baffle or bifurcated Y-graft. The use of Y-grafts was originally hypothesized to provide more even hepatic blood flow distribution to the lungs, a factor related to pulmonary arteriovenous malformations. This study evaluates the hemodynamic performance of the largest Y-graft cohort to date, compares those results with a traditional baffle, and highlights Y-graft cases that exhibit both favorable and poor performance. Methods: Thirty Y-graft and 30 traditional baffle Fontan patients were analyzed. TCPC anatomies and vessel flow waveforms were reconstructed using cardiac magnetic resonance (CMR) images and phase-contrast CMR. Computational fluid dynamic simulations were performed to quantify TCPC power loss, resistance, and hepatic flow distribution (HFD). Comparisons between graft types and subanalysis of favorable versus poor performing Y-grafts were investigated. Results: The TCPC resistance distribution, HFD distribution, and the effect of LPA stenosis on power loss for Y-grafts and traditional baffles are shown in Fig. 1A-1C. TCPC resistance was significantly lower in traditional baffle patients. HFD was similar overall, with median and range of 40 (1-77) and 51 (1-99) for the traditional baffle and Y-graft, but show a discrepancy at extreme values with more unbalanced flow in the Y-graft cohort. Power loss was more sensitive to LPA stenosis in the Y-graft cohort. Prediction of Y-graft HFD is multi-factorial and six representative cases are shown in Fig. 1D. Conclusions: Y-grafts do not inherently provide more balanced HFD than traditional baffles. Traditional baffles are more energetically favorable and less sensitive to PA stenosis. Graft type should be considered on an individual basis as hemodynamic performance is based on a combination of factors, including global flow distribution, PA stenosis and SVC positioning.

Enhanced axial mixing of rotating drums with alternately arranged baffles

Traditional rotating drums are a popular type of tumbling mixer; however, they generally suffer from poor axial mixing with granular materials. To overcome this weakness, a system of alternately arranged baffles is presented, and its effect on particle mixing is numerically assessed using a GPU-based discrete element method. It is found that this arrangement of baffles displays better axial mixing performance than drums with (or without) traditional baffles, and that maximum mixing efficiency can be obtained through a suitable choice of baffle dimension and number. Essentially, this novel arrangement promotes the bulk movement of particles in the axial direction because of the combined radial scattering and axial guiding effects of the baffles. Together with the enhanced dispersive mixing, axial convective mixing serves to increase the axial mixing efficiency. Moreover, it is found that alternately arranged baffles produce good performance in various granular systems of rotating drums. Thus, the proposed system is a promising approach for industrial applications in more complicated mixers.

Numerical Study on Improved Baffle in Compact Test Separator

The aim of this paper is to design two improved baffles to solve the injection problem caused by traditional baffle in compact test separatorand use FLUENT software to study their effects on separator pressure loss and separation efficiency. The result shows: that anti-injection baffle can make compact test separator with a high separation efficiency with a relatively low pressure loss. Also, the diameter of anti-injection plate which makes the compact test separator at its highest separation efficiency is slightly smaller than that which makes the lowest pressure loss.

Development of guidelines for improved hydraulic design of waste stabilisation ponds

Pond hydraulic behaviour is influenced by the inlet/outlet configuration, baffles and wind, but design information relating to these factors is still very limited. This paper reviews the development of "Guidelines for the Improved Hydraulic Design of Waste Stabilisation Ponds" and summarises some of the key findings and recommendations. This work was based on review of previous research, laboratory experimentation, field studies and mathematical modelling using computational fluid dynamics. The inlet design can have a significant influence on the flow regime in a pond. Poorly considered positioning of the inlet and the outlet can create hydraulic short-circuiting problems. As an example of the nature of the work undertaken in this project, the use of a small horizontal inlet pipe was compared against a vertical inlet design. A practical method of assessing the relative significance of wind versus inlet power input was presented. The application of this analysis may allow engineers to size inlet pipes to help control the flow patterns in ponds for efficient performance. Extensive testing has been undertaken on a wide range of baffle configurations. An example of this research showed how short stub baffles could provide similar improvements to longer "traditional" baffle designs, potentially offering significant savings in construction costs. For traditional baffle designs a minimum of two baffles is recommended. For the pond modelled in this work, it was found that any more than four baffles gave only marginal improvements.