scholarly journals A study of flow characteristics in a low-pressure ejector installation

2021 ◽  
Vol 274 ◽  
pp. 08006
Author(s):  
Evgenia Varsegova ◽  
Lilia Osipova ◽  
Daniel Bugembe
Keyword(s):  
Flow Characteristics ◽  
Low Pressure ◽  
Hazardous Substances ◽  
Flow Rates ◽  
Pressure Losses ◽  
Ejection Coefficient ◽  
Wide Range ◽  
Calculation Results ◽  
Local Ventilation ◽  
Paint Coatings

Production processes sometimes are accompanied by the release of hazardous substances, the composition and volume of which is determined by the production technology. When designing ventilation systems for paint departments, special attention is paid to safety concerns, since all paint coatings are corrosive and flammable substances. Besides, solvent vapors are explosive. For local ventilation of painting chambers, it is rational to use safe exhaust systems with an ejector, which works sturdily, regardless of the release of flammable and explosive impurities. The ejector is simple in design and can operate in a wide range of changes in the parameters of the state of airflow. The model of the ejection unit is synthesized using the universal modeling package ChemCad, which contains a highly developed database of airflow parameters, which allows for solving various applied problems. Numerical modeling was carried out using the software package - FLUENT. In work, a calculation was carried out and a low-pressure ejector was designed for a typical painting booth. The calculation results are presented in the form of graphs and tables of pressures, velocities, flow rates in characteristic sections, pressure losses in the sections of the ejector installation.The ejection coefficient was also calculated.

Transition Modelling for Vortex Generating Jets on Low-Pressure Turbine Profiles

2011 ◽  
Author(s):  
Florian Herbst ◽  
Dragan Kozˇulovic´ ◽  
Joerg R. Seume
Keyword(s):  
Total Pressure ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Local Transition

Steady blowing vortex generating jets (VGJ) on highly-loaded low-pressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynolds-numbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled γ-ReΘ transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. High-speed cascade wind tunnel experiments for a wide range of Reynolds-numbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is ≤ 100·103 an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modelled by a filtered Q vortex criterion the transition development itself is modelled by a reduction of the local transition-onset momentum-thickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.

Influence of Surface Roughness on the Profile and End-Wall Losses in Low Pressure Turbines

2011 ◽  
Author(s):  
Rau´l Va´zquez ◽  
Diego Torre ◽  
Fernando Partida ◽  
Leyre Arman˜anzas ◽  
Antonio Antoranz
Keyword(s):  
Surface Roughness ◽  
Total Pressure ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Pressure Flow ◽  
Flow Angle ◽  
Pressure Losses ◽  
Wide Range ◽  
Wall Losses ◽  
End Wall

The influence of surface roughness on the profile and end-wall total pressure losses in Low Pressure Turbines was investigated experimentally in a turbine high-speed rig. The rig consisted of a rotor-stator configuration. Both rows of airfoils are high lift, high aspect ratio and high turning blades that are characteristic of state of the art Low Pressure Turbines. The stator airfoils (both vanes and platforms) were casted and afterwards they were barreled to improve their surface finish up to 1.73 μm Ra. Then they were assembled in the rig and tested. The stator was traversed upstream and downstream with miniature pneumatic probes to obtain total pressure, flow angle and static pressure flow fields. Once this test was completed the rig was disassembled and the stator airfoils were polished to achieve a roughness size of 0.72 μm Ra, characteristic of Low Pressure Turbine polished airfoils. Once again, the stators were assembled in the rig and tested to carry out a back-to-back comparison between the two different surface roughnesses. The total pressure profile and end-wall losses were measured for a wide range of Reynolds numbers, extending from 8×104 to 2.4×105, based on suction surface length (Res∼1.5 ReCx) and exit Mach number of 0.61. Experimental results are presented and compared in terms of area average, radial pitchwise average distributions and exit plane contours of total pressure losses, flow angles and helicity. The results agree with previous studies of roughness in Turbines, a beneficial effect of surface roughness was found at very low Reynolds numbers, in stagnation pressure losses.

Numerical Investigation on the Flow Characteristics of a Supercritical CO2 Centrifugal Compressor

2014 ◽  
Author(s):  
Hang Zhao ◽  
Qinghua Deng ◽  
Kuankuan Zheng ◽  
Hanzhen Zhang ◽  
Zhenping Feng
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Flow Characteristics ◽  
Low Pressure ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Compact Size ◽  
Wide Range

Supercritical CO2 closed-loop Brayton cycles offer the potential of better economical and practical efficiency due to its compact size and smaller compression work as compared with some traditional working fluids cycles, in which compressor is the key component. In this paper, the aerodynamic design and impeller aerodynamic optimization were conducted for a single stage centrifugal compressor with a combined vaneless and vaned diffuser, operating with CO2 slightly above the vapor-liquid critical point. The NIST REFPROP database was used for the computation of supercritical CO2 properties in design analysis and numerical investigation. The flow characteristics of the supercritical CO2 compressor were investigated by NUMECA FINE/Turbo. In order to weaken the low pressure regions, a vaneless diffuser was applied in this design, which would control and reduce the distribution differences of fluid thermodynamic states and increase fluid static pressure. The results indicate that there are no obvious low pressure regions occurring close to the leading edge of vaned diffuser. So it is observed in the design process that the vaneless diffuser could improve the aerodynamic performance of supercritical CO2 compressor. Compared with the operating conditions of the compressor only under centrifugal force, the pressure load from the aerodynamic analysis and the centrifugal load due to high speed of rotation were considered in the study of the stress and deformation of the structure of impeller by ANSYS/Mechanical. It can be concluded that supercritical CO2 provides unique properties for the compressor working process, which have a significant influence on finite element modeling in structural analysis. For the present design the maximum von Mises stress and total deformation are shown much smaller than the maximum allowable values, and thus the compressor could work in a wide range of operating conditions.

Transition Modeling for Vortex Generating Jets on Low-Pressure Turbine Profiles

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
Florian Herbst ◽  
Dragan Kožulović ◽  
Joerg R. Seume
Keyword(s):  
Total Pressure ◽  
Reynolds Numbers ◽  
Low Pressure ◽  
Quantitative Prediction ◽  
Design Parameters ◽  
Transition Model ◽  
Pressure Losses ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Local Transition

Steady blowing vortex generating jets (VGJ) on highly-loaded low-pressure turbine profiles have shown to be a promising way to decrease total pressure losses at low Reynolds-numbers by reducing laminar separation. In the present paper, the state of the art turbomachinery design code TRACE with RANS turbulence closure and coupled γ-ReΘ transition model is applied to the prediction of typical aerodynamic design parameters of various VGJ configurations in steady simulations. High-speed cascade wind tunnel experiments for a wide range of Reynolds-numbers, two VGJ positions, and three jet blowing ratios are used for validation. Since the original transition model overpredicts separation and losses at Re2is≤100·103, an extra mode for VGJ induced transition is introduced. Whereas the criterion for transition is modeled by a filtered Q vortex criterion the transition development itself is modeled by a reduction of the local transition-onset momentum-thickness Reynolds number. The new model significantly improves the quality of the computational results by capturing the corresponding local transition process in a physically reasonable way. This is shown to yield an improved quantitative prediction of surface pressure distributions and total pressure losses.

Flow dynamics in lumboperitoneal shunts and their implications in vivo

2009 ◽  
Vol 111 (3) ◽  
pp. 632-637 ◽  
Author(s):  
Nitin Mukerji ◽  
Julian Cahill ◽  
Desiderio Rodrigues ◽  
Savithru Prakash ◽  
Roger Strachan
Keyword(s):  
Standard Treatment ◽  
Flow Characteristics ◽  
Pressure Head ◽  
Low Pressure ◽  
Simple Experiment ◽  
Catheter Position ◽  
Pseudotumour Cerebri ◽  
Flow Rates ◽  
Internal Radius

Object Lumboperitoneal shunting is the standard treatment for pseudotumour cerebri or idiopathic intracranial hypertension. Complications are common, particularly the problem of overdrainage leading to low pressure symptoms. The authors designed a simple experiment using catheters of different lengths that drained at different pressure heads and with different vertical drops to study the flow characteristics in these shunts and determine the optimal catheter placement and length that would reduce the occurrence of low pressure headaches. Methods The flow rates through catheters of 3 different lengths (60, 83, and 100 cm) with the same internal radius, at 3 different pressure heads (15, 25, and 35 cm H2O to simulate 3 different placements in the lumbar theca), and 3 different vertical drops (10, 20, and 30 cm to simulate the possible effect of siphoning) were measured and the results analyzed. Results Application of Poiseuille's law and Bernoulli's principle to the experimental design shows that the volume of flow is directly proportional to the sum of the pressure head and the vertical drop and inversely proportional to the length of the catheter. The flow rate through the standard catheter lengths over the course of 24 hours can be abnormally high. An attempt to predict the optimal catheter length was made. Conclusions Although the catheter position in the theca and abdomen cannot be altered significantly and the internal radius of the tube cannot be reduced further without increasing the risk of blockage, the length of the tube can be increased to combat overdrainage. The authors suggest that currently available catheters are too short.

Automation of Process Control in Chemical Plant

2015 ◽  
Vol 2 (1) ◽  
pp. 6-12
Author(s):  
Agus Sugiarta ◽  
Houtman P. Siregar ◽  
Dedy Loebis
Keyword(s):  
Process Control ◽  
Pid Control ◽  
Control Algorithm ◽  
Chemical Engineering ◽  
Chemical Plant ◽  
Raw Material ◽  
Flow Rates ◽  
Material Supply ◽  
Wide Range ◽  
Inherent Problem

Automation of process control in chemical plant is an inspiring application field of mechatronicengineering. In order to understand the complexity of the automation and its application requireknowledges of chemical engineering, mechatronic and other numerous interconnected studies.The background of this paper is an inherent problem of overheating due to lack of level controlsystem. The objective of this research is to control the dynamic process of desired level more tightlywhich is able to stabilize raw material supply into the chemical plant system.The chemical plant is operated within a wide range of feed compositions and flow rates whichmake the process control become difficult. This research uses modelling for efficiency reason andanalyzes the model by PID control algorithm along with its simulations by using Matlab.

The Politics of Precaution

2012 ◽  
Author(s):  
David Vogel
Keyword(s):  
United States ◽  
Animal Feed ◽  
The United States ◽  
Hazardous Substances ◽  
Risk Regulation ◽  
Scientific Certainty ◽  
European Public ◽  
Wide Range ◽  
Regulatory Controls ◽  
Milk Hormones

This book examines the politics of consumer and environmental risk regulation in the United States and Europe over the last five decades, explaining why America and Europe have often regulated a wide range of similar risks differently. It finds that between 1960 and 1990, American health, safety, and environmental regulations were more stringent, risk averse, comprehensive, and innovative than those adopted in Europe. But since around 1990 global regulatory leadership has shifted to Europe. What explains this striking reversal? This book takes an in-depth, comparative look at European and American policies toward a range of consumer and environmental risks, including vehicle air pollution, ozone depletion, climate change, beef and milk hormones, genetically modified agriculture, antibiotics in animal feed, pesticides, cosmetic safety, and hazardous substances in electronic products. The book traces how concerns over such risks—and pressure on political leaders to do something about them—have risen among the European public but declined among Americans. The book explores how policymakers in Europe have grown supportive of more stringent regulations while those in the United States have become sharply polarized along partisan lines. And as European policymakers have grown more willing to regulate risks on precautionary grounds, increasingly skeptical American policymakers have called for higher levels of scientific certainty before imposing additional regulatory controls on business.

Nitrogen Removal from Anaerobically-Treated Leachate

1984 ◽  
Vol 19 (1) ◽  
pp. 87-100
Author(s):  
D. Prasad ◽  
J.G. Henry ◽  
P. Elefsiniotis
Keyword(s):  
Nitrogen Removal ◽  
Air Flow ◽  
Operating Conditions ◽  
Air Flow Rate ◽  
Flow Rates ◽  
Anaerobic Filter ◽  
Ph Values ◽  
Wide Range ◽  
Ammonia Desorption ◽  
Effects Of Ph

Abstract Laboratory studies were conducted to demonstrate the effectiveness of diffused aeration for the removal of ammonia from the effluent of an anaerobic filter treating leachate. The effects of pH, temperature and air flow on the process were studied. The coefficient of desorption of ammonia, KD for the anaerobic filter effluent (TKN 75 mg/L with NH3-N 88%) was determined at pH values of 9, 10 and 11, temperatures of 10, 15, 20, 30 and 35°C, and air flow rates of 50, 120, and 190 cm3/sec/L. Results indicated that nitrogen removal from the effluent of anaerobic filters by ammonia desorption was feasible. Removals exceeding 90% were obtained with 8 hours aeration at pH of 10, a temperature of 20°C, and an air flow rate of 190 cm3/sec/L. Ammonia desorption coefficients, KD, determined at other temperatures and air flow rates can be used to predict ammonia removals under a wide range of operating conditions.

Hydraulic model of a water cooling system in a chemical plant

1988 ◽  
Vol 53 (4) ◽  
pp. 788-806
Author(s):  
Miloslav Hošťálek ◽  
Jiří Výborný ◽  
František Madron
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Cooling Water ◽  
Graph Algorithm ◽  
Automatic Generation ◽  
Hydraulic Calculation ◽  
Return Flow ◽  
Flow Rates ◽  
Pressure Losses ◽  
Controlled Flow

Steady state hydraulic calculation has been described of an extensive pipeline network based on a new graph algorithm for setting up and decomposition of balance equations of the model. The parameters of the model are characteristics of individual sections of the network (pumps, pipes, and heat exchangers with armatures). In case of sections with controlled flow rate (variable characteristic), or sections with measured flow rate, the flow rates are direct inputs. The interactions of the network with the surroundings are accounted for by appropriate sources and sinks of individual nodes. The result of the calculation is the knowledge of all flow rates and pressure losses in the network. Automatic generation of the model equations utilizes an efficient (vector) fixing of the network topology and predominantly logical, not numerical operations based on the graph theory. The calculation proper utilizes a modification of the model by the method of linearization of characteristics, while the properties of the modified set of equations permit further decrease of the requirements on the computer. The described approach is suitable for the solution of practical problems even on lower category personal computers. The calculations are illustrated on an example of a simple network with uncontrolled and controlled flow rates of cooling water while one of the sections of the network is also a gravitational return flow of the cooling water.

scholarly journals The Role of the Reactive Species Involved in the Photocatalytic Degradation of HDPE Microplastics Using C,N-TiO2 Powders

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 999 ◽  
Author(s):  
Aranza Denisse Vital-Grappin ◽  
Maria Camila Ariza-Tarazona ◽  
Valeria Montserrat Luna-Hernández ◽  
Juan Francisco Villarreal-Chiu ◽  
Juan Manuel Hernández-López ◽  
...  
Keyword(s):  
Wastewater Treatment Plants ◽  
Reaction System ◽  
Terrestrial Ecosystems ◽  
Degradation Process ◽  
Reactive Species ◽  
Hazardous Substances ◽  
Wide Range ◽  
Degradation Behaviors ◽  
Environmentally Friendly Process

Microplastics (MPs) are distributed in a wide range of aquatic and terrestrial ecosystems throughout the planet. They are known to adsorb hazardous substances and can transfer them across the trophic web. To eliminate MPs pollution in an environmentally friendly process, we propose using a photocatalytic process that can easily be implemented in wastewater treatment plants (WWTPs). As photocatalysis involves the formation of reactive species such as holes (h+), electrons (e−), hydroxyl (OH●), and superoxide ion (O2●−) radicals, it is imperative to determine the role of those species in the degradation process to design an effective photocatalytic system. However, for MPs, this information is limited in the literature. Therefore, we present such reactive species’ role in the degradation of high-density polyethylene (HDPE) MPs using C,N-TiO2. Tert-butanol, isopropyl alcohol (IPA), Tiron, and Cu(NO3)2 were confirmed as adequate OH●, h+, O2●− and e− scavengers. These results revealed for the first time that the formation of free OH● through the pathways involving the photogenerated e− plays an essential role in the MPs’ degradation. Furthermore, the degradation behaviors observed when h+ and O2●− were removed from the reaction system suggest that these species can also perform the initiating step of degradation.

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