Velocity Characteristics of a Confined Highly-Turbulent Swirling Flow Near a Swirl Plate (Data Bank Contribution)

1994 ◽  
Vol 116 (4) ◽  
pp. 685-693 ◽  
Author(s):  
R. X. Shi ◽  
B. Chehroudi
Keyword(s):  
Flow Rate ◽  
Recirculation Zone ◽  
Swirling Flow ◽  
Air Flow ◽  
Tangential Velocity ◽  
Velocity Profiles ◽  
Air Flow Rate ◽  
Reversed Flow ◽  
Swirl Number ◽  
Flow Rates

Axial and tangential components of the velocity vector are measured using a Laser Doppler Velocimeter (LDV) system in a confined highly turbulent isothermal swirling flow near a swirl plate. The flow has essential features of swirl-stabilized flame combustors. Throughout this study, a constant “nominal” swirl number of 0.36 is generated by air jets from a set of slots in a swirl plate. A low-speed coflowing air, referred to as dilution air, is uniformly distributed around the swirling flow by use of an annular-shaped honeycomb. Three different swirling air flow rates with a fixed dilution flow rate are studied and results are discussed. Detailed mean axial and tangential velocity profiles at several axial locations show that the size and the strength of the central recirculation zone are strongly dependent on the swirling air flow rate. Increasing the swirl air flow rate increases both the radial extent and the axial length of the central recirculation zone. Mean total and reversed air flow rates are calculated by integrating the mean axial velocity profiles. In the setup used in this study and up to the axial positions investigated, the reversed flow rate as a percent of the total flow rate seems to be linearly proportional to the reversed-flow zone area, being independent of the swirl air flow rate at a fixed nominal swirl number value. As swirl air flow rate is increased, the root mean square (rms) of the axial and tangential velocity fluctuations increase monotonically at almost all radial positions except sufficiently away from the swirl plate and near the chamber axis. Several velocity biasing correction methods are reviewed. A simple velocity biasing correction scheme is applied in this study to investigate its effect on the conclusions reached in the study.

Experimental Analysis of Simplex Atomizer Spray and Swirling Flow Interactions in Unconfined Conditions

2015 ◽  
Author(s):  
Muthu Selvan ◽  
Muralidhara Suryanarayana Rao ◽  
Indu Kharb ◽  
Sundararajan Thirumalachari ◽  
Vinod Kumar Vyas ◽  
...  
Keyword(s):  
Size Distribution ◽  
Water Flow ◽  
Droplet Size ◽  
Flow Rate ◽  
Swirling Flow ◽  
Air Flow ◽  
Single Mode ◽  
Air Flow Rate ◽  
Volume Percentage ◽  
Flow Rates

An experimental study has been conducted to investigate the interaction between the conical spray produced by simplex atomizer and the swirling flow from an axial swirler. This work has been carried out in an unconfined ambience at isothermal conditions, using water. Malvern spray analyzer with a three dimensional traverse is used to characterize the swirling flow and spray interactions at various axial and radial locations. Images of spray at different conditions of air and water mass flow rates have been analyzed. Increasing the air mass flow through swirler at constant water flow rate, changes the spray structure significantly. These structural changes are sudden and highly dependent on the initial conditions of the spray. At smaller air flow rates, single-mode droplet size distribution at mid-plane changes into a bi-modal distribution at an air flow rate of about 35 kg/hr, with higher contribution of larger droplets. With further increase in air flow rate (90, 110 and 130 kg/hr), the bi-modal size distribution is maintained but with a larger volumetric fraction of small droplets. At different axial distances, the droplet size distributions are similar (single mode and bimodal distributions depending on air flow rate). But volume percentage of larger droplets is less compared to those of smaller droplets, at larger axial distance. At outer radial locations of the spray, volume percentage of larger droplets reduces and that of smaller droplets increases significantly, due to secondary droplet breakup. The interaction between the swirl and spray causes droplets to move radially outwards, resulting in droplet break-up by impact on the dome. Cases with higher air to water flow ratios exhibit significant changes in drop size distribution due to such swirl-spray interactions.

Model-Based Analysis of Transient Behavior of Large Scale CFB Boilers

2003 ◽  
Author(s):  
Ari Kettunen ◽  
Timo Hyppa¨nen ◽  
Ari-Pekka Kirkinen ◽  
Esa Maikkola
Keyword(s):  
Flow Rate ◽  
Large Scale ◽  
Air Flow ◽  
Model Parameters ◽  
Air Flow Rate ◽  
Process Data ◽  
Cfb Boiler ◽  
Flow Rates ◽  
Load Change ◽  
Secondary Air

The main objective of this study was to investigate the load change capability and effect of the individual control variables, such as fuel, primary air and secondary air flow rates, on the dynamics of large-scale CFB boilers. The dynamics of the CFB process were examined by dynamic process tests and by simulation studies. A multi-faceted set of transient process tests were performed at a commercial 235 MWe CFB unit. Fuel reactivity and interaction between gas flow rates, solid concentration profiles and heat transfer were studied by step changes of the following controllable variables: fuel feed rate, primary air flow rate, secondary air flow rate and primary to secondary air flow ratio. Load change performance was tested using two different types of tests: open and closed loop load changes. A tailored dynamic simulator for the CFB boiler was built and fine-tuned by determining the model parameters and by validating the models of each process component against measured process data of the transient test program. The know-how about the boiler dynamics obtained from the model analysis and the developed CFB simulator were utilized in designing the control systems of three new 262 MWe CFB units, which are now under construction. Further, the simulator was applied for the control system development and transient analysis of the supercritical OTU CFB boiler.

Coordinated control of fuel flow rate and air flow rate of a supersonic heat-airflow simulated test system

2020 ◽  
Vol 124 (1278) ◽  
pp. 1170-1189
Author(s):  
C. Cai ◽  
L. Guo ◽  
J. Liu
Keyword(s):  
Flow Rate ◽  
Control Algorithm ◽  
Air Flow ◽  
Coordinated Control ◽  
Test System ◽  
Gas Temperature ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Fuel Flow ◽  
Simulated Test

ABSTRACTThe gas temperature of the supersonic heat airflow simulated test system is mainly determined by the fuel and air flow rates which enter the system combustor. In order to realise a high-quality control of gas temperature, in addition to maintaining the optimum ratio of fuel and air flow rates, the dynamic characteristics of them in the combustion process are also required to be synchronised. Aiming at the coordinated control problem of fuel and air flow rates, the mathematical models of fuel and air supply subsystems are established, and the characteristics of the systems are analysed. According to the characteristics of the systems and the requirements of coordinated control, a fuzzy-PI cross-coupling coordinated control strategy based on neural sliding mode predictive control is proposed. On this basis, the proposed control algorithm is simulated and experimentally studied. The results show that the proposed control algorithm has good control performance. It cannot only realise the accurate control of fuel flow rate and air flow rate, but also realise the coordinated control of the two.

scholarly journals POLYMER WASTES’ FLOTATION SEPARATION RESEARCH RESULTS

2020 ◽  
Vol 6 (444) ◽  
pp. 50-58
Author(s):  
А. Volnenko ◽  
◽  
А. Leudanski ◽  
Y. Apimakh ◽  
B. Korganbayev ◽  
...  
Keyword(s):  
Liquid Layer ◽  
Flow Rate ◽  
Air Flow ◽  
Liquid Temperature ◽  
Air Flow Rate ◽  
Flotation Process ◽  
Flow Rates ◽  
Research Results ◽  
Air Bubble ◽  
Plastic Wastes

For separation of plastic wastes (polyamide (PA), acrylonitrile butadiene styrene (ABS) and polystyrene (PS), a flotation method is proposed. Using this method, the effect of concentration of surface-active substances (surfactants), which were used as polidocanol, sulphanole and a mixture of surfactants containing sodium laureth sulfate and diethanolamide, was studied. The research results analysis of the flotation separation of a mixture of crushed plastic wastes was carried out according to the calculated values of the extraction of a floated component ε and the purity of a concentrate β. It was noted that the maximum extraction of the floated component depends on the polymer and surfactant type. A mixture of surfactants at lower concentrations allows to achieve greater extraction of the floated component with less foaming ability. The research results on the extraction of polystyrene from the air flow rate at various concentrations of surfactants’ mixture show that the extraction has a maximum at a certain air flow rate. At low air flow rates, the working volume of liquid is not saturated enough with gas bubbles. If the optimal value of air flow rates is exceeded, many gas bubbles are formed that are not involved in the flotation process. The research results on the extraction of polystyrene from the aerated liquid layer height at various concentrations of surfactants’ mixture show that, at a low height of the aerated liquid layer, the probability of collision of a plastic particle with an air bubble is low and some potentially floated particles seek the bottom of an apparatus without having time to collide with an air bubble. When assessing the influence of liquid temperature on the flotation process, it was found that increasing the liquid temperature above 20°C leads to a sharp decrease in ABS and PS extraction. This is explained by the fact that the dependence of the surfactants’ foaming ability on the temperature is characterized by solubility curves and for most surfactants they have an extremum.

scholarly journals Evaluation of Izmir Tulum cheese pieces by drying with tray drier at different air flow rates and temperatures

2018 ◽  
Author(s):  
Nurcan Koca ◽  
Gulsah Kizilalp ◽  
Izel Polat ◽  
Müge Urgu
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Sensory Properties ◽  
Water Holding Capacity ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Physical Chemical ◽  
Tulum Cheese ◽  
Water Holding

Izmir tulum cheese pieces were dried using a tray dryer at different air flow rates (1.0 and 1.8 m/s) and temperatures (45oC, 55oC and 65oC). The increase in temperature and air flow rate increased bulk and tapped bulk densityand decreased the water holding capacity. The lowest lightness and highest redness were obtained in samples dried at 65oC. The samples dried at 55°C and 1 m/s had the highest flavor and overall impression scores. As a result, a dried cheese product to benefit from left-over pieces obtained during packaging  was developed, having advantages such as easy to transport, store and package.Keywords: Izmir Tulum cheese; tray dryer; physical, chemical and sensory properties.   

Evaluation of numerical modelling for a compact down-hole subsea gas-liquid separator for high gas content

2009 ◽  
Vol 49 (1) ◽  
pp. 433
Author(s):  
Shakil Ahmed ◽  
Mohamed Nabil Noui-Mehidi ◽  
Jamal Naser's ◽  
Gerardo Sanchez Soto ◽  
Edson Nakagawa
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Volume Fraction ◽  
Air Flow ◽  
Gas Content ◽  
Water Mixture ◽  
Air Flow Rate ◽  
Flow Rates ◽  
High Efficient ◽  
Liquid Separator

This paper describes the computational fluid dynamics (CFD) modelling of a laboratory scale gas-liquid separator designed for high gas content. The separator consists of two concentric pipes with swirl tube in the annular space between the pipes. The gas-liquid mixture comes tangentially from the side inlet and the system works with a combination of gravity and centrifugal forces to achieve a high-efficient gas-liquid separation. Three dimensional transient multi-phase fluid flows were solved to predict the velocity and volume fraction of each phase. The standard k- turbulence model was used for turbulence closure. The performance of the gas-liquid separator was visually established for a range of gas flow rates (271–495 L/min), with volume fraction (VF) =0.874–0.985 by observing the liquid carry over (LCO) regime where liquid was carried out in the gas stream. The liquid and gas flow rates at which the LCO was observed defines the upper operational range of the separator. Air-water mixture was used in the numerical simulations to keep consistent with the experiments. The pressure between the inlet and exit was validated against the experiments for different air-water flow rate combinations. The values were matched reasonably well for high air flow rate (495 L/min, VF=0.985) but were under-predicted for low air flow rate (271 L/min, VF=0.874). The air and water were mixed upstream of the inlet in the experiments and the pressure was measured at the start of the inlet. In case of numerical simulation the air and water were mixed at the inlet. This might cause the deviation of pressure when the air flow rate was low.

Two-Phase Flow Visualization for a Hybrid Heat Sink

2018 ◽  
Author(s):  
Danish Rahman ◽  
Ahmad Almomani ◽  
Ibrahim Hassan ◽  
Yasser Al-Hamidi ◽  
Aziz Rahman
Keyword(s):  
Flow Rate ◽  
Slug Flow ◽  
Air Flow ◽  
Plug Flow ◽  
Cross Flow ◽  
Flow Regimes ◽  
Air Flow Rate ◽  
Two Phase ◽  
Flow Rates ◽  
Impingement Jet

This paper aimed to study two-phase flow under adiabatic conditions through the process of flow visualization. This was done through the use of a test section with a cross flow and a jet impingement (swirl jet). The flow regimes under different air-water flow rates were determined using a high-speed camera that recorded digital videos. For each of the flow rates the pressure differential between the inlet and the outlets were measured. Through the pressure drop it is proposed that the types of flow regimes may later be able to be predicted. Nine air-water flow rates were considered to collect data and generate a flow map for the impingement jet and cross flow. The major observed flow regimes within the crossflow and impingement jet followed the predicted trend with bubbly and plug flow in the former, and slug flow in the latter. It was further observed that increasing the air flow rate increased the likelihood of bubbly and plug flow in both the cross-flow and impingement jet. In the cross flow, a lower air flow rate resulted in bubbly flow while within the impingement jet, a lower air flow rate resulted in slug flow.

scholarly journals Dynamic Permeability of Porous Elastic Fabrics

2012 ◽  
Vol 7 (2_suppl) ◽  
pp. 155892501200702 ◽  
Author(s):  
Phillip W. Gibson ◽  
Kenneth Desabrais ◽  
Thomas Godfrey
Keyword(s):  
Flow Rate ◽  
High Pressures ◽  
Air Flow ◽  
High Strength ◽  
Fluid Structure Interactions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Dimensional Changes ◽  
Permeability Changes ◽  
Dynamic Permeability

This paper describes permeability measurements for porous fabrics as influenced by strain, humidity, air flow rate, and fabric elasticity. The focus is on standard parachute fabrics, where the fabric's porosity and air permeability influence the rate of steady-state descent, and also affect the complicated fluid-structure interactions taking place during parachute opening and deployment. High strength nylon parachute fabrics showed relatively small permeability changes due to strain, humidity, and flow rate. Comparative measurements on elastomeric fabrics showed much larger changes in air flow due to fabric dimensional changes at high pressures and flow rates. Elastomeric fabrics that stretch and change permeability in response to higher pressures and flow rates may be able to reduce the “opening shock” during the parachute deployment phase.

Numerical Investigation of the Nonreacting Swirling Flow Structure Downstream of Industrial Gas Turbine Burner With the Central Body

2015 ◽  
Author(s):  
Ivan A. Zubrilin ◽  
Dmitriy N. Dmitriev ◽  
Sergey S. Matveev ◽  
Sergey G. Matveev
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Flow Structure ◽  
Flow Rate ◽  
Central Body ◽  
Swirling Flow ◽  
Air Flow ◽  
Air Flow Rate ◽  
Piv Measurements ◽  
Good Agreement

This paper will discuss the investigation of the nonreacting swirling flow downstream of the burner with the central body. This burner is designed for burning partially prepared fuel-air mixture. The burner consists of the axial swirler and the central body. The swirler plays the role of the premixer, and the central body is used to stabilize the flame. The simulation was conducted with the commercial software ANSYS Fluent 15.0. At present, the most widespread CFD approaches to the swirling flow investigation are URANS and LES. In this study URANS is used for obtaining flow charts and LES is used for detailed research of swirling flow structures. The influences of the model parameters (turbulence models, geometry simplification) and numerical parameters (the number of grid elements) on the burner pressure drop are shown in the simulation results. The LES results were compared with the experimental data on the flow structure downstream of the burner. The measurements were provided by 2D PIV with the imaging frequency of 500 Hz and 1000 Hz. It was found that in the investigated range of parameters the burner pressure drop changes slightly and is in good agreement with the experimental data. It was shown that the results of the PIV measurements with the different imaging frequency are in good agreement. The results show that flow behavior achieved in simulation is in accordance with the PIV measurements. It is shown that the flow separation from the central body trailing edge results in formation of large eddies and high velocity fluctuations. On the one hand it can contribute to the mixing of pilot fuel with air, but on the other hand it can lead to high amplitude pressure oscillations during combustion. The form and the frequency of the precessing vortex core were discovered. It was found that the maximum air flow rate through the recirculation zone is about 12% of the total air flow rate through the burner.

Thermal analysis on charging and discharging behaviour of a phase change material-based evacuated tube solar air collector

2016 ◽  
Vol 27 (2) ◽  
pp. 156-172 ◽  
Author(s):  
Neeraj Mehla ◽  
Avadhesh Yadav
Keyword(s):  
Phase Change ◽  
Total Energy ◽  
Phase Change Material ◽  
Flow Rate ◽  
Air Flow ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Solar Air Collector ◽  
Evacuated Tube ◽  
Change Material

The performance analysis on the phase change material-based evacuated tube solar air collector was examined under consecutive and simultaneous charging and discharging modes. Acetamide was used as phase change material. The system performance was evaluated on the basis of the phase change material storage system energy efficiency, exergy efficiency, collector efficiency, the instantaneous energy stored in the phase change material and total energy stored by the system at low and high air flow rates of 0.018 kg/s and 0.035 kg/s, respectively. The maximum average efficiency (17.9%) of the collector was obtained at a high air flow rate during simultaneously charging and discharging of the phase change material. The results obtained demonstrate that the system is more effective when it is operated with high air flow rate during simultaneously charging and discharging of the phase change material. The average total energy at high air flow rates is 1.01 to 1.02 times more in comparison to that at low air flow rates. The findings show the feasibility of the phase change material-based evacuated tube solar air collector for producing hot air for space heating during consecutive and simultaneous charging and discharging of the phase change material in northen Indian climatic conditions. This system would be relevant in areas with good sunlight.

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