Papers by Keyword: Flow

Abstract: In this paper, the compressive strength quality characteristics of lightweight formedmagnesia composite using super absorbent polymer as basic material for biological panels wereevaluated. The experimental parameters were evaluated with respect to the compressive strength ofthe mortar according to the water binder ratio (W/B), the volume ratio of fine aggregate (Vs/Vm), theamount of foaming agent (FA) and the amount of super absorbent polymer (SAP). Statistical analysiswas performed on the compressive strength obtained through the experiment and the influencecoefficient on the compressive strength quality was obtained. The compressive strength qualityprediction model equation of the magnesia composite is proposed through the obtained influencecoefficient. The proposed model equation shows that the experimental and predicted values are over80%.

Abstract: It was proposed to use air flow screw straightened units in outlet pipe of the dust collectors to reduce the aerodynamic resistance of exhaust ventilation systems. It is allowed to decrease power consumption for their maintenance operation consequently. The article describes the results of experimental studies to evaluate its effectiveness by applying the tangential screw straightened unit within ventilation system. The obtained results showed that the use of this device allows reducing the aerodynamic resistance of the cyclone by 14.6%, and for counter-swirling flows’ dust collector (CSFC) by 17.2-23.6%. It was found that meanings of the aerodynamic resistance depend on value the share proportion of the flow entering into lower CSFC apparatus’ input.

Abstract: This paper covers the results of study of the influence of cavitation treatment on nanostructuring of the alkali aluminosilicate binder for intumescent coatings. The results of study suggested to establish optimal parameters of cavitation treatment. At pressure of 20...25 atm, temperature below 30 °С, time of treatment shorter than 10 min rheological properties tend to improve and phase formation processes to accelerate at normal curing temperatures which result in the enhancement of heat engineering and mechanical properties of the intumescent coatings.

Abstract: The planar flow of a Newtonian incompressible fluid in a T-shaped channel is investigated. Three fluid interaction models with solid walls are considered: no slip boundary condition, Navier slip boundary condition and slip boundary condition with slip yield stress. The fluid flow is provided by uniform pressure profiles at the boundary sections of the channel. The problem is numerically solved using a finite difference method based on the SIMPLE procedure. Characteristic flow regimes have been found for the described models of liquid interaction with solid walls. The estimation of the influence of the Reynolds number, pressure applied to the boundary sections and the parameters of these models on the flow pattern was performed. The criterial dependences describing main characteristics of the flow under conditions of the present work have been demonstrated.

Abstract: Numerical simulation of cooling roller in planar flow melt spinning process was accomplished using CFD software, Get cooling water flow characteristics and the cooling roller wall temperature and pressure distribution with cooling roller rotation speed range 0-50r/s, The results show that: heat transfer coefficient h and Nusselt number between the cooling water and the inner wall surface of a copper roller creases with the increase of the cooling roller rotate speed, but the increase rate is relatively small; Effect of cooling roller rotate speed on inner wall pressure is large, cooling roller inner wall pressure increases with the rotation speed increase. This study provided a theoretical reference of amorphous cooling roller design and optimization.

Abstract: Laser ablation under a flowing water layer can reduce thermal damage in work material and also provide a better machining performance than processing in ambient air. However, there is still a lack of insight into a more complicated process like laser milling operation in water. Besides the laser parameters, the roles of water flow direction on the cut geometries need to be elucidated to realize the viability and reliability of the laser milling process in water. This study is for the first time to reveal the effects of water flow direction on the cavity dimensions and cut surface roughness in the laser milling process performed under a flowing water layer. Titanium alloy was used as a work sample in this study. The experimental results indicated that the laser beam should travel in the same direction of water flow to provide a uniform cavity depth and smooth milled surface.

Abstract: Underwater laser machining process has a high potential over the typical laser ablation to remove materials with less thermal damage occurring along the cut. However, the formations of vapor bubble and cut debris in water can substantially disturb the incident laser beam, thereby reducing the ablation performance. Instead of performing the ablation in still water, the flowing water technique was applied to flush away the cut debris and bubble generated. In this study, the effects of laser pulse energy, traverse speed and water flow rate on the cut surface roughness and heat-affected zone in the laser grooving of silicon were experimentally investigated and analyzed. The findings revealed that the cut surface roughness decreased with the increases in laser pulse energy and laser traverse speed. Though a higher water flow rate resulted in a rougher cut surface, the heat-affected zone can be minimized when the increased flow rate was applied.

Abstract: The performance of blower depends on impeller condition. This paper is to discuss the open face impeller condition related to performance based on performance curve provided by the manufacturer. The impeller condition is observed under three different conditions. The first condition is that the impeller area is covered by 3 mm thick of fouling. The second condition is that there is a 1 mm of rubbing on the vane and the third condition is the impeller after being repaired. The datas are taken by the actual operation condition. The observed data is then calculated and plotted on OEM performance curve. The result shows that the first condition has the lowest performance; the produced head is 47% lower than the OEM’s.

Abstract: Drying is an important way to improve the quality of lignite with high moisture. In this paper, a single-shaft paddle dryer experimental system was built to investigate the drying characteristics of fine-particle lignite with diameter 0-5mm. The experimental results show that with the increasing in shaft rotation speed the flow rate of lignite increases linearly approximately and the residence time decreases correspondingly. Increasing the inclination angle of dryer frame helps increase the flow rate. Both shaft rotation speed and heating source (heat transfer oil) temperature have significant effects on outlet moisture content of lignite. Shaft rotation speed affects the average heat transfer coefficient greatly and heating source temperature affects it weakly for specified conditions. It is found that for 5-12mm coarse-particle lignite, flow is not smooth and the average heat transfer coefficient is much less than that of fine-particle lignite. This research shows that it is feasible technically to dry fine-particle lignite by using paddle dryers, but not suitable to dry coarse-particle lignite.

Abstract: This paper deals with a use of CFD modelling for optimization of supply of secondary combustion air in the two-chamber biomass boiler combusting very wet biomass (capacity ca. 200 kW). Objective of the analyse is to observe the impact of diameter of a secondary air supply pipe and air flow velocity on mixing of the secondary air with flue gas in the combustion chamber. The numerical model of the experimental boiler was build up for subsequent utilizing of CFD computation based on finite element method. The commercial code STAR-CD was used for carried out parametrical studies. Series of calculations were carried out for four different diameters of air distribution pipes and for 3 different air velocities in distribution orifice. Quality of air dispersion in flue gas flow was assessed in the vertical cross section lead in the end of the combustion chamber. The results of calculation were verified on the experimental installation of the boiler. Influence of secondary air mixing on emission production was measured and analysed. Emissions of pollutants for recommended air distribution comply with emission limits stipulated in the most stringent class 5 according to ČSN-EN 303-5 as well as with emission limits under Regulation No. 405/2012 Sb.