Theoretical Model of a Flow in a Tube With a Slit

2019 ◽  
Author(s):  
Yuki Toda ◽  
Masataka Morimatsu ◽  
Yu Nishio ◽  
Takanobu Ogawa
Keyword(s):  
Theoretical Model ◽  
Flow Field ◽  
Pressure Loss ◽  
Longitudinal Direction ◽  
Gas Mixture ◽  
Straight Tube ◽  
One Dimensional ◽  
Tube Type ◽  
Gas Burner

Abstract A tube-type gas burner consists of a straight tube with a slit along it and discharges an air-gas mixture through the slit to produce a flame. The flow velocity from the slit depends on the pressure in the tube and the pressure loss at the slit, and it varies in the longitudinal direction of the tube. The resulting uneven flame degrades the quality of the burner. In this study, we develop a one-dimensional theoretical model of the flow in a tube with a slit. To validate the result of the theoretical model, we also conduct experiments and numerical simulations for the same flow field. We applied this theoretical model to a flow in a tube, 1 m length, 40 mm in diameter, with a slit 2.5 mm wide. The end of the tube is closed. We also discuss the effect of the length of the burner on the unevenness.

Blowing Control in Serpentine Inlet and its Effect on Fan-Stage Performance

2020 ◽  
Author(s):  
Yubo He ◽  
Qingzhen Yang ◽  
Huicheng Yang ◽  
Saile Zhang ◽  
Haoqi Yang
Keyword(s):  
Flow Field ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Energy ◽  
Aerodynamic Performance ◽  
Blowing Ratio ◽  
Total Pressure Recovery

Abstract Serpentine inlet is widely used in military and civil aircraft due to its good stealth performance. However, it generates a high total pressure loss and swirl distortion which significantly affects the performance and the stability of the compressor. In order to improve the quality of the flow field at the aerodynamic interface plane (AIP), a flow control is required inside the serpentine inlet. The objective of this paper was to study the effectiveness of the blowing active flow control on reducing the swirl distortion and on improving the total pressure recovery at the AIP, by reducing the low-momentum flow in the serpentine inlet. The mechanism of the blowing control and the effect of the design parameters (i.e. blowing angle, blowing position and blowing flow rate) on the aerodynamic performance at the AIP were studied. The optimal solution was applied to the full flow path of the serpentine inlet and the fan-stage. The numerical results showed that the quality of the flow field at the AIP were effectively improved by blowing high-energy airflow into the boundary layer of the serpentine inlet. The blowing position had a high influence on the blowing effect, and upper wall blowing scheme obtained greater benefits than lower wall blowing scheme and combination blowing scheme. In addition, the blowing angle should be selected to avoid the high-energy air from pipes mixing with mainstream in the serpentine inlet which will result in an additional total pressure loss. When the ratio of the blowing mass flow rate to the designed mass flow rate of the serpentine inlet was about 1.5%, the swirl distortion on the AIP reached a minimum value, which then did not show a significant difference in performance with blowing ratio increased. When the upper wall blowing scheme was adopted with a blowing angle of 6 degrees and a blowing ratio of 1.5%, the AIP aerodynamic performance achieved the highest improvement, with an increase of the total pressure recovery factor by about 1%, and a decrease of the circumferential total pressure distortion and the swirling distortion by 60% and 61%, respectively. With the optimal control scheme, the area of the low-pressure region near the upper wall was remarkably reduced, and the performance of fan-stage was improved, with an increase of the pressure ratio by about 1.5%, and the efficiency of the single-stage compressor by about 3.1%, respectively.

Analysis of flow field characteristics and structure optimization of the split-stream rushing muffler for diesel engine

2020 ◽  
Vol 68 (1) ◽  
pp. 101-111 ◽  
Author(s):  
He Su ◽  
Pei Wu ◽  
Jing Xue ◽  
Yongan Zhang ◽  
Haijun Zhang
Keyword(s):  
Theoretical Model ◽  
Diesel Engine ◽  
Flow Field ◽  
Pressure Loss ◽  
Transmission Loss ◽  
Engineering Application ◽  
Structure Optimization ◽  
Resistance Coefficient ◽  
Tracer Test ◽  
Flow Field Characteristics

In order to analyze the flow field characteristics of the split-stream rushing muffler, a theoretical model describing the velocity of the split streams is established and verified by the tracer test. For this new-principle muffler, the acoustic performance and the relationship between the velocity drop of the airflow and the pressure field are analyzed, also the structure optimization of the muffler is carried out based on the orthogonal test. Finally, a new muffler is fabricated based on the designing theory of this type of muffler for a prototype of diesel engine, and the comparative analyses are conducted compared with its original muffler. The results show that the establishment and analysis of the theoretical model for velocity during the split-streams rushing process are correct. In the frequency range of 0â–“1000 Hz, the average transmission loss of split-stream rushing muffler is better than that of the original muffler. While the speed of airflow is reduced by split-streams rushing, a certain pressure loss is caused at the same time, which is about 50% of total pressure loss of the muffler, and the average fluid resistance coefficient of the split-stream rushing process is 0.91. Compared to the original muffler of the sample engine, the average insertion loss of the optimized new muffler is increased by 61.2%. At inlet air velocity of 30 m/s, the pressure loss is reduced by 16.8%. The results provide a potential for practical engineering application of this new split-stream rushing muffler in future.

Theoretical Model of a Flow in a Tube-type Gas Burner

2018 ◽  
Vol 2018 (0) ◽  
pp. G0500403
Author(s):  
Masataka MORIMATSU ◽  
Kengo HARA ◽  
Takanobu OGAWA
Keyword(s):  
Theoretical Model ◽  
Tube Type ◽  
Gas Burner

Investment climate and government turnover in russian regions

2014 ◽  
pp. 88-117 ◽  
Author(s):  
G. Syunyaev ◽  
L. Polishchuk
Keyword(s):  
Economic Development ◽  
Theoretical Model ◽  
Private Sector ◽  
Authoritarian Regimes ◽  
Russian Regions ◽  
Investment Climate ◽  
Regional Data ◽  
Endogenous Property Rights ◽  
The Impact

We study the impact of Russian regional governors’ rotation and their affiliation with private sector firms for the quality of investment climate in Russian regions. A theoretical model presented in the paper predicts that these factors taken together improve “endogenous” property rights under authoritarian regimes. This conclusion is confirmed empirically by using Russian regional data for 2002—2010; early in that period gubernatorial elections had been canceled and replaced by federal government’s appointments. This is an indication that under certain conditions government rotation is beneficial for economic development even when democracy is suppressed.

ANALYSIS OF SOUND SPEED IN LONGITUDINAL DIRECTION AT REFERENCE MOISTURE CONTENT (w = 12 %) IN SAWMILL ASSORTMENTS (FAGUS SYLVATICA, L.)

Akustika ◽  
2020 ◽  
pp. 45-50
Author(s):  
Alena Rohanová
Keyword(s):  
Moisture Content ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Sound Speed ◽  
Longitudinal Direction ◽  
Structural Timber ◽  
Sound Speeds ◽  
Dynamic Modulus Of Elasticity ◽  
Round Timber

This paper explores the analysis of sound speeds in the longitudinal direction and their reduction to the reference moisture content w = 12 %. The sound speed cw was determined with Sylvatest Duo device. Moisture content of beech sawmill assortments (round timber: N = 16, logs: N = 2 × 16, structural boards: N = 54) in the range of 12 – 72 % was measured. For the analysis purposes, the sound speed was converted to reference conditions (c12, uref = 12%). A second-degree polynomial (parabola) with a regression equation of the form: c// = 5649 - 27,371 × w + 0.0735 × w2 was used to convert cw to c12, and correction of measured and calculated values was used as well. The sound speeds c12 in sawmill assortments (c12,round, c12,log, c12,board) were evaluated by linear dependences. Dependence was not confirmed for c12,round and c12,board1 (r = 0.168), in contrast for c12,round and c12,log2 the dependence is statistically very significant (r = 0.634). The results of testing showed that the most suitable procedure for predicting quality of structural timber is the first step round timber – log2, the second step: log2 - board2. More exact results of the construction boards were obtained from log2 than from log1. The sound speed is used in the calculation of dynamic modulus of elasticity (Edyn). EN 408 mentions the possibility of using dynamic modulus of elasticity as an alternative method in predicting the quality of structural timber.

Effect of mechanical restraint on the rate of corrosion in concrete

1998 ◽  
Vol 25 (1) ◽  
pp. 81-86 ◽  
Author(s):  
N Hearn ◽  
J Aiello
Keyword(s):  
Mix Design ◽  
Concrete Repair ◽  
Accelerated Corrosion ◽  
One Dimensional ◽  
Mechanical Restraint ◽  
Corrosion Rates ◽  
Accelerated Corrosion Tests ◽  
The Matrix ◽  
The Relationship

Experimental work on prismatic concrete specimens was conducted to determine the relationship between mechanical restraint and the rate of corrosion. The current together with the changes in strain of the confining frame were monitored during the accelerated corrosion tests. The effect of mix design and cracking on the corrosion rates was also investigated. The results show that one-dimensional mechanical restraint retards the corrosion process, as indicated by the reduction in the steel loss. Improved quality of the matrix, with and without cracking, reduces the rate of steel loss. In the inferior quality concrete, the effect of cracking on the corrosion rate is minimal.Key words: corrosion, concrete, repair.

Effects of U-Shape Inner Cooler on Flow and Solidification of Molten Steel in Slab Continuous Casting Mold

2011 ◽  
Vol 291-294 ◽  
pp. 423-427
Author(s):  
Yan Juan Jin ◽  
Xiao Chao Cui ◽  
Zhu Zhang
Keyword(s):  
Fluid Dynamics ◽  
Temperature Field ◽  
Flow Field ◽  
Continuous Casting ◽  
Molten Steel ◽  
Continuous Casting Mold ◽  
Slab Continuous Casting ◽  
Cooling Technology ◽  
Steel Flow

An inner-outer coupled cooling technology of molten steel for 1240×200mm slab continuous casting, that is to set an inner cooler—U shape pipes in the mold, is put forward in order to enhance the efficiency of transmitting heat and improve inner structure of billet. The flow status and solidification status of molten steel under coupling flow field and temperature field in inner-outer coupled cooling mold are simulated by using fluid dynamics software, and compare with those in traditional mold. It is found that setting inner cooler in the mold can make molten steel flow status even, which is favorable to floating up of the inclusion, quickening the solidification of steel liquid and improving the quality of billet.

Thermal Mapping, via Liquid Crystals, of the Temperature Field near a Heated Surgical Probe

1973 ◽  
Vol 95 (2) ◽  
pp. 250-256 ◽  
Author(s):  
T. E. Cooper ◽  
J. P. Groff
Keyword(s):  
Blood Flow ◽  
Temperature Field ◽  
Liquid Crystals ◽  
Theoretical Model ◽  
Wheatstone Bridge ◽  
Visual Display ◽  
Two Dimensional ◽  
Test Medium ◽  
One Dimensional ◽  
Water Test

This paper discusses the use of heat for producing clinical lesions in tissue and presents the design and analysis of a resistively heated surgical probe. The probe surface temperature is accurately maintained and controlled by using a Wheatstone bridge. The probe was embedded in a clear agar–water test medium, and the temperature field generated by the probe was measured with liquid crystals, a material that provides a visual display of certain isotherms. Experimental results compare within approximately 10 percent of a two-dimensional numerical solution. A one-dimensional theoretical model is also developed which examines the influence of blood flow on the temperature field.

Theoretical Modeling of Thermoelectricity in Bi Nanowires

1998 ◽  
Vol 545 ◽  
Author(s):  
X. Sun ◽  
Z. Zhang ◽  
G. Dresselhaus ◽  
M. S. Dresselhaus ◽  
J. Y. Ying ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Theoretical Model ◽  
Quantum Confinement ◽  
Figure Of Merit ◽  
Wire Diameter ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Crystalline Orientation ◽  
One Dimensional ◽  
Bismuth Nanowires

AbstractBismuth as a semimetal is not a good thermoelectric material in bulk form because of the approximate cancellation between the electron and hole contributions. However, quantum confinement can be introduced by making Bi nanowires to move the lowest conduction subband edge up and the highest valence subband edge down to get a one-dimensional (1D) semiconductor at some critical wire diameter dc. A theoretical model based on the basic band structure of bulk Bi is developed to predict the dependence of these quantities on wire diameter and on the crystalline orientation of the bismuth nanowires. Numerical modeling is performed for trigonal, binary and bisectrix crystal orientations. By carefully tailoring the Bi wire diameter and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire diameters.

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