scholarly journals Numerical Study on Flow and Release Characteristics of Gas Extinguishing Agent under Different Filling Pressure and Amount Conditions

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1683
Author(s):  
Quanwei Li ◽  
Hui Ge ◽  
Renming Pan ◽  
Zhaojun Zhang ◽  
Ruiyu Chen
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Filling Pressure ◽  
Release Time ◽  
Second Phase ◽  
Release Process ◽  
Fire Extinguishing ◽  
Fire Extinguishing System

The fire-extinguishing system is an indispensable fire-protection facility on the aircraft. In order to guide weight reduction of the aircraft’s fixed gas fire-extinguishing system by improving its release efficiency, so as to improve fuel economy and reduce carbon emissions, the influence of filling pressures and filling amounts on the release efficiency of gas extinguishing agent along pipelines were studied based on numerical simulations. The release process of the fire-extinguishing system was analyzed. The effects of the filling pressure and filling amount of Halon 1301 agent on the release characteristics, such as release time, mass flow rate, and gasification ratio, were studied. Results show that the release process can be divided into three major phases, which are firstly the initial rapid filling of the pipeline, secondly the concentrated release of the liquid extinguishing agent, and thirdly the gas ejection along the pipeline. The second phase can also be subdivided into two stages: the outflow of the liquid extinguishing agent from the bottle, and the release of the residual liquid extinguishing agent along the pipeline. The release characteristics of the fire-extinguishing agent were obviously affected by the filling pressures and filling amounts. When the filling pressure was relatively low (2.832 MPa), increasing the filling pressure can significantly increase the mass flow rate, shorten the release time, and reduce the gasification ratio of the extinguishing agent during the release processes. Under the same filling pressure, with the increase of the filling amount of the extinguishing agent, the release times and the gasification ratio showed a linear increase trend, while the average mass flow rates showed a linear decrease trend.

scholarly journals Numerical Study on Effects of Pipeline Geometric Parameters on Release Characteristics of Gas Extinguishing Agent

Symmetry ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1766
Author(s):  
Quanwei Li ◽  
Zongyu Li ◽  
Ruiyu Chen ◽  
Zhaojun Zhang ◽  
Hui Ge ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Release Time ◽  
Pipeline System ◽  
Average Pressure ◽  
Fire Extinguishing ◽  
Drop Rate ◽  
Peak Value

In order to guide the optimization design of the pipeline network of the aircraft-fixed gas fire extinguishing system and improve its fire extinguishing performance, FLUENT software was used to simulate the influence of pipeline parameters such as diameter, length, and roughness on the release characteristics of the fire extinguishing agent. It can be found that the extinguishing agent can be divided into liquid and vapor extinguishing agents in the fire extinguishing pipeline system during the release. The spatial distribution and proportion of the liquid and vapor extinguishing agents are asymmetric. Results show that the peak value of the pressure drop rate (dPmax) has a good quadratic function relationship with the pipeline diameter (D) and the functional relationship is dPmax=−22.224+2.782D+0.089D2, which means that the peak value increased significantly with the increase in the pipeline diameter. Moreover, when the pipeline diameter is 25 mm, the average pressure drop rate of the vessel is about 35.02 MPa/s, which is 5.97 times the value of the average pressure drop rate when the pipeline diameter is 10 mm. With the increase in the pipeline diameter, the release time decreases significantly, the mass flow rate increases obviously, while the gasification ratio decreases rapidly at first and then increases slightly. The pipeline length also has a significant influence on the release characteristics of the extinguishing agent. With the increase in the pipeline length, the release time and the gasification ratio increase linearly, while the mass flow rate decreases linearly. Compared with the pipeline diameter and pipeline length, the influence of the pipeline roughness on the release characteristics of the extinguishing agent is weak. With the increase in the pipeline roughness, the release time and the gasification ratio of the extinguishing agent increases slowly, while the mass flow rate decreases slowly.

Numerical Performance and Flow Field Study of Centrifugal Compressor With Supercritical Carbon-Dioxide (SCO2)

2019 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Properties ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Compressor Inlet

Abstract The Supercritical carbon-dioxide Brayton cycle main attraction is due to the Supercritical characteristic of the working fluid, carbon-dioxide (SCO2). Some of the advantages of using SCO2 are relatively low turbine inlet temperature, the compression work will be low, and the system will be compact due to the variation of thermodynamic properties (like density, and specific heat ratio) of SCO2 near the critical point. SCO2 behave more like liquid when its state is near the critical point (Total Pressure = 7.39 MPa, Total Temperature = 305 K), operating compressor inlet near critical point can minimize compression work. For present study the centrifugal compressor was designed to operate at 75,000 rpm with pressure ratio (P.R) = 1.8 and mass flow rate = 3.53 kg/s as available from Sandai report. Meanline design for centrifugal compressor with SCO2 properties was done. The blade geometry was developed using commercial CAD Ansys Bladegen. The flow domain was meshed using Ansys TurboGrid. ANSYS CFX was used as a solver for present numerical study. The thermodynamic properties of SCO2 were imported from the ANSYS flow material library using SCO2.RPG [NIST thermal physics properties of fluid system]. In order to ensure the change in flow physics the mesh independence study was also conducted. The present paper discuss about the performance and flow field study targeting different mass flow rates as exit boundary condition. The comparison of overall performance (Pressure Ratio, the Blade loading, Stage efficiency and Density variation) was done with three different mass flow rates. The designed and simulated centrifugal compressor meets the designed pressure rise requirement. The variation of mass flow rate on performance of centrifugal compressor was tend to be similar to conventional centrifugal compressor. The paper discusses about the effect of variation in density, specific heat ratio and pressure of SCO2 with different mass flow outlet condition. The performance map of numerical study were validated with experiment results and found in good agreement with experimental results. The change in flow properties within the rotor flow passage are found to be interesting and very informative for future such centrifugal compressor design for special application of SCO2 Brayton cycle. 80% mass flow rate has given better results in terms of aerodynamic performance. Abrupt change in thermodynamic properties was observed near impeller inlet region. Strong density variations are observed at compressor inlet.

Numerical Study on the Main Coolant Pump of Sodium-Cooled Fast Reactor

2015 ◽  
Author(s):  
Sungho Ko ◽  
Yeon-tae Kim
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fast Reactor ◽  
Numerical Study ◽  
Pressure Rise ◽  
Head Loss ◽  
Computational Domain ◽  
Coolant Pump ◽  
Pump Head

A numerical study was conducted to predict the performance curve of a downscaled model of the main coolant pump for a sodium-cooled fast reactor and to reduce the head loss by the optimization of the diffuser blade. The ANSYS CFX program was utilized to obtain flow characteristics inside the pump as well as the overall pressure rise across the pump operating on- and off-design points. Computational domain was divided into several blocks to achieve high grid quality effectively and 7.5 million nodes were used totally to resolve small leakage flows as well as the flow inside the rotating impeller. The corresponding experiment was conducted to validate CFD computed results. The comparison between the CFD and experimental data shows excellent agreement in terms of mass flow rate and head rise on and near design operating points. The DOE (design of experiments) and RSM (response surface method)[1] were utilized to reduce the head loss by the diffuser blade in the pump. The diffuser blade was defined as four geometric parameters for DOE. The analysis of 25 cases was made to solve the output parameters for all design points which are defined by the DOE. RSM was fitting the output parameter as a function of the input parameters using regression analysis techniques. The optimized model increased the total pump head on the design point and the low mass flow rate point, but total pump head on 130% of operating mass flow rate was reduced than the initial model.

Applying CFD for Studying the Dynamic and Thermal Behavior of Solar Chimney Drying System with Reversed Absorber

2017 ◽  
Vol 13 (11) ◽  
Author(s):  
Souheyla Khaldi ◽  
A. Nabil Korti ◽  
Said Abboudi
Keyword(s):  
Thermal Behavior ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Packed Bed ◽  
Maximum Temperature ◽  
Storage Material ◽  
Solar Chimney ◽  
Solar Dryer

AbstractThis article provides numerical study of the solar chimney (SC) assembled with a reversed absorber and packed bed for the indirect-mode solar dryer. The present study was designed to determine the effects of using the SC in three configuration and physical proprieties of the packed (thickness and porosity) on the dynamic and thermal behavior of airflow. The results reveal that (1) using SC without storage material can increase the maximum mass flow rate up to 5%. However, integrating a storage material in the SC can improve the mass flow rate up to 32% during nighttime; (2) the use of a packed bed can decrease the crops temperature fluctuation until about 76% and increase the operating time of the solar dryer up to 12.5 hours rather than 10 hours in the case without packed bed; (3) increasing the porosity from 0.1 to 0.8 can increase the maximum temperature by about 10°C.

scholarly journals Emissions Reduction by Varying the Swirler Airflow Split in Advanced Gas Turbine Combustors

1992 ◽  
Author(s):  
Gerald J. Micklow ◽  
Subir Roychoudhury ◽  
H. Lee Nguyen ◽  
Michael C. Cline
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Pollutant Emissions ◽  
Nasa Lewis Research ◽  
Fuel Injector ◽  
Lean Burn ◽  
Lean Combustion ◽  
Fuel Nozzle

A rich burn/quick mix/lean burn (RQL) combustor concept for reducing pollutant emissions is currently under investigation at the NASA Lewis Research Center (LeRC). A numerical study was performed to investigate the chemically reactive flow with liquid spray injection for the RQL combustor. The RQL combustor consists of an airblast atomizer fuel injector, a rich burn section, a converging connecting pipe, a quick mix zone, a diverging connecting pipe and a lean combustion zone. For computational efficiency, the combustor was split into two sub systems, i.e. the fuel nozzle/rich burn section and the quick mix/lean burn section. The current study investigates the effect of varying the mass flow rate split between the swirler passages for an equivalence ratio of 2.0 on fuel distribution, temperature distribution, and emissions for the fuel nozzle/rich burn section of an RQL combustor. The input conditions used in the study were chosen based on tests completed at LeRC. It is seen that optimizing these parameters can substantially improve combustor performance and reduce combustor emissions. The optimal mass flow rate split for reducing NOx emissions based on the numerical study was the same as found by experiment at LeRC.

Numerical Study of Laminar Mixed Convection of a Nanofluid in a Horizontal Curved Tube with Constant Heat Flux and Mass Flow Rate

2011 ◽  
Vol 110-116 ◽  
pp. 3657-3662
Author(s):  
S. Alikhani ◽  
A. Behzadmehr ◽  
S. Mirmasoumi
Keyword(s):  
Heat Flux ◽  
Mixed Convection ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Volume Fraction ◽  
Numerical Study ◽  
Two Phase ◽  
Curved Tube ◽  
Laminar Mixed Convection

Fully developed laminar mixed convection of a nanofluid (water/Al2O3) in a horizontal curved tube is numerically investigated. Three-dimensional elliptic governing equations have been solved to show how nanoparticle concentration affects on thermal and hydrodynamic parameters while these parameters are impressed by centrifugal and buoyancy forces under constant mass flow rate and heat flux. Comparisons with previously published experimental works on horizontal curved tubes show good agreements between the results. Results which are obtained using the two – phase mixture model indicate that adding the nanoparticles causes changes in the properties of nanofluid and finally increases the temperature of the flow. Furthermore, increasing nanoparticles volume fraction at first augments the heat transfer coefficient of nanofluid and then, for higher concentration of particles, decreases this thermal parameter of nanofluid.

Numerical Simulation of Distribution of Discharged Gas Fire Extinguishing Agent in High Velocity Flow Field

2013 ◽  
Vol 718-720 ◽  
pp. 1786-1791
Author(s):  
Xing Ming Ma ◽  
Lan Ming Zhao ◽  
Yu Nong Li ◽  
Di Di Li ◽  
Jia Jia Fu ◽  
...  
Keyword(s):  
Power Plant ◽  
Flow Field ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
High Velocity ◽  
High Velocity Flow ◽  
Fire Extinguishing ◽  
Velocity Flow ◽  
Civil Aircraft ◽  
Fire Extinguishing System

This paper studied the concentration distribution of gas extinguishing agent numerically in high velocity flow field. Civil aircraft power plant compartment has been a difficult area for its high velocity flow field formed after fire happens. Focusing on this issue, certain results, such as mass flow rate of agent gas, total mass of agent and extinguishing efficiency were presented. A typical apparatus of fire extinguishing system was set up, and its fire-fighting efficiency was evaluated. Critical ratio of mass flow rate and flow velocity, gas discharge time and locations of gas sample tubes were recommended. The results and data can provide a practical way in fire extinguishing system evaluation in civil aircraft power plant compartment.

Experimental and Numerical Study of Cavitation in Centrifugal Pumps

2010 ◽  
Author(s):  
Erfan Niazi ◽  
M. J. Mahjoob ◽  
Ardeshir Bangian
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Mass Flow Rate ◽  
Computer Simulations ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Numerical Results ◽  
Centrifugal Pumps ◽  
Cavitation Threshold

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.

scholarly journals Dynamics of the Gas Hydrates Decomposition in a Porous Medium Taking Into Account the Formation of Ice

2017 ◽  
Vol 3 (1) ◽  
pp. 46-57
Author(s):  
Nail G. Musakaev ◽  
Stanislav L. Borodin ◽  
Marat K. Khasanov
Keyword(s):  
Natural Gas ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Numerical Study ◽  
Gas Extraction ◽  
Frontal Surface ◽  
Promising Source

Natural gas is one of the main energy carriers, for example, in 2014 it accounted for about 22% of the world’s electricity production. The main component of natural gas is methane (77-99%). The largest reserves of methane are concentrated in gas hydrates; according to different sources, their total volume twice exceeds the magnitude of the traditional recoverable reserves of methane. Thus, given the increasing demand and the largest amount compared with other fossil fuels, methane, extracted from gas hydrates, is the most promising source of energy. And for the effective extraction of methane from gas hydrate deposits, theoretical studies are needed.<br> In this paper we consider the problem of gas hydrate decomposition to gas and ice during the gas extraction from the hydrate-containing deposit initially saturated with methane and its hydrate. To solve this problem, we constructed the mathematical model of non-isothermal filtration of an imperfect gas with account of the formation or decomposition of this gas’ hydrate. On the basis of this model, the numerical study of the influence of gas mass flow rate on the dynamics of decomposition of the hydrate was made. It shows that in the case of negative initial temperatures of the reservoir, the dissociation of the gas hydrate will always occur to gas and ice. In this case, regimes of dissociation of the hydrate with a frontal surface or a volume region of phase transitions are possible. It is established that an increase in the mass flow rate of gas extraction first leads to the decomposition of the hydrate on a frontal surface, and then in a volume zone. A further increase in the gas mass flow rate leads to an increase in the length of the volume zone and an increase in the amount of the hydrate decomposed therein.

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