Advance Modelling and Simulation of Industrial Boilers
K. A.
Khazaee
author
M.
SadrAmeli
, Tarbiat Modarres University
author
text
article
1998
eng
This paper presents some of the results of the simulation in the radiation section of an industrial boiler using an advanced mathematical model. Calculations are described for the flow, heat transfer, and chemical reaction processes occurring within a gas-fired cylindrical furnace. The calculation procedure is a two dimensional one in which the main hydrodynamic variables are the velocity and stream functions. The turbulence formulae are used for this purpose. Mass transfer and chemical reactions are calculated from the model which assumes a single-step chemical reaction. Heat transfer is determined hy the solution of differential equations for the specific enthalpy, and for the radiative fluxes for each of the co-ordinate directions. The resulting system of coupled. non linear, elliptic, partial differential equations gives the velocity and temperature gradients inside the furnace. The results are compared with those reported in the literature and good agreements between them were found.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
61
72
https://www.ije.ir/article_71198_d2dc999aefa3fb303dd0722b9c734ac4.pdf
Adaptive Line Enhancement Using a Parallel IIR Filter with A Step-By-step Algorithm
M.
Ghavami
Electerical Engineering, University of Science and Defense Technology
author
text
article
1998
eng
A step-by-step algorithm for enhancement of periodic signals that are highly corrupted by additive uncorrelated white gausian noise is proposed. In each adaptation step a new parallel second-order section is added to the previous filters. Every section has only one adjustable parameter, i.e., the center frequency of the self-tuning filter. The bandwidth and the convergence factor of each section is adjusted nonadaptively by a deterministic simple method which results in a stable and accurate regulation of the adaptive parameters. The step-by-step detection of sinusoidal signals prevents the convergence difficulties encountered in adaptive parallel IIR filters. Computer simulation results are presented to show the noise canceling performance of the proposed algorithm. Some comparisons with a new adaptive lattice notch filter for detection of multiple sinusoids are also provided.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
73
82
https://www.ije.ir/article_71199_0fac49719c1cae68bb830f052b1c16c2.pdf
Combined Radiation and Natural Convection in Participating Laminar Flow Over a Vertical Circular Pin
G.
Soleimani
Mechanical Engineering, University of Tabriz
author
Esmaeil
Khoshravan-Azar
Mechanical Engineering, University of Tabriz
author
text
article
1998
eng
The interaction of thermal radiation with conduction and laminar natural convection in a vertical circular pin, situated at participating gas, is numerically investigated. An absorbing and emitting gas is considered, and treated to be a gray participating media. Under the idealizing of gray gas, the Rosselan4 approximation is employed to describe the radiative heat flux in the energy equation. The modified box method with unequal grid spacing is used to perform the numerical computation of the coupled boundary layer conservation equations and pin conduction equation. The effects of buoyancy and radiation on the temperature, velocity, heat flux, and Nusselt number are examined in detail. The Nusselt number variation shows that heat transfer is enhanced by thermal radiation. Also, the local Nusselt number is found to be strongly dependent on the temperature ratio YT, radiation-conduction parameter YR, and conventional Gr and Pr numbers. Furthermore, the results are comparable with the available data in the literature for pure natural convection.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
83
92
https://www.ije.ir/article_71200_c77619e95f1ceffe166709a1404ae820.pdf
Experimental Investigation of Friction Coefficient in Ribleted Pipes and the Effect of Fine Particles
B.
Firoozabadi
Mechanical Engineering, Sharif University of Technology
author
M.
Rad
Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran
author
text
article
1998
eng
The effect of fine particles on turbulence damping and reduction of flow friction coefficient in ribleted pipes, have been investigated experimentally. Tests have been conducted in a ribleted pipe with hydraulic diameter of 18.6 mm, and 20 stream wise riblets of 1.8 mm depth, along the pipe. Flows of water tap with Reynolds number from 5000 to 30000 were compared with flows containing silt-clay particles and stone powder of less than 63 micron sizes. In the flows containing 1.6 kg/in3 of stone powder, the pressure drop along the pipe reduced by 25 percent, and with flows containing silt-clay particles, the pressure drop reduction was about 15 percent. Reduction of friction, in flows containing fine particles, may be due to the interaction of particles and turbulence generated at pipe boundary, and damping of this turbulence.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
93
100
https://www.ije.ir/article_71201_d9cda4623c46e6956d76c9e0dcde2f33.pdf
Structure and Properties of a Natural Celulosic Hollow Fiber
S.
Shaikhzadeh Najar
, Amirkabir University of Technology
author
Mohammad
Haghighat- Kish
Textile Engineering, Amirkabir University of Technology
author
text
article
1998
eng
The interaction of thermal radiation with conduction and laminar natural convection in a vertical circular pin, situated at participating gas, is numerically investigated. An absorbing and emitting gas is considered, and treated to be a gray participating media. Under the idealizing of gray gas, the Rosselan4 approximation is employed to describe the radiative heat flux in the energy equation. The modified box method with unequal grid spacing is used to perform the numerical computation of the coupled boundary layer conservation equations and pin conduction equation. The effects of buoyancy and radiation on the temperature, velocity, heat flux, and Nusselt number are examined in detail. The Nusselt number variation shows that heat transfer is enhanced by thermal radiation. Also, the local Nusselt number is found to be strongly dependent on the temperature ratio YT, radiation-conduction parameter YR, and conventional Gr and Pr numbers. Furthermore, the results are comparable with the available data in the literature for pure natural convection.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
101
108
https://www.ije.ir/article_71202_e4074623ce27ecbb77f0e132964d0de6.pdf
Prediction a of Tribocorrosion Wear Rate (RESEARCH NOTE)
A. N.
Sakharov
, Russian Academy of Sciences
author
text
article
1998
eng
Basic properties of the suggested phenomenological model of tribocorrosion wear are considered. Using a friction pair austenitic stainless steel-ceramic in acid electrolytes as an example, a good agreement between predicted data and experimental evidence was obtained.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
109
114
https://www.ije.ir/article_71203_8020133bb006f049a68aa55520bf6e54.pdf
Investigation of the Effect of Exhaust Gas Recirculation (EGR) on pollutants Emission From Si Engine Exhaust Gasese (RESEARCH NOTES)
Y.
Ajabshirchy
, University of Tabriz
author
V. S.
Efendiev
Mechanical Engineering, University of Tabriz
author
text
article
1998
eng
This paper reports the results of an experimental investigation on the effect of the EGR on the pollutants emission, especially on oxides of nitrogen, from the exhaust gases and performance of the spark ignition engine. Also along with experimental work, a mathematical model for the determination of the effect of EGR on the peak cycle temperature and for the prediction of its effect on the NOx emission is constructed. The results of theoretical calculation show how peak temperature of theoretical cycle decreased with increasing of the recycling gas percentage. Tests were conducted on a four stroke petrol engine used in passenger cars. The experimental investigations show that NOx emission decreases with increasing of the percentage of the recycling gas. At 9% recycling, 73% of NOx emissions decreased at EGR valve opening 360 degrees. Brake specific fuel consumption and brake power are changed negligibly.
International Journal of Engineering
Materials and Energy Research Center
1025-2495
11
v.
2
no.
1998
115
120
https://www.ije.ir/article_71204_709dc6aea3a8e7e0eef1624531e22079.pdf