Effect of Aft-deck Length on the Performance of Serpentine Nozzle

Hamada Mohamed(하마다 모하메드),Changwook Lee(이창욱),Heeju Choi(최희주),Jeekeun Lee(이지근) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8

Serpentine nozzle has been widely utilized in many types of aircraft to minimize the infrared radiation emitted by high temperature parts and exhaust systems. Annular mixer was used in the infrared suppressor of exhaust system to mix the cold outside air with hot gases from the engine. The most important parameters can evaluate the performance of the nozzle with lobed mixer include mixing effectiveness, pressure loss, and pumping performance. A central plug is used at the exit of the lobed nozzle to penetrate the primary stream in the nozzle. In this study a numerical investigation of flow characteristics of the serpentine nozzle with lobed mixer was conducted. The flow characteristics such as velocity, temperature, pressure of the lobed mixer were studied. The three-dimensional model of the serpentine nozzle was used in the simulations that carried out using Star CCM software. The grid system com-posed of 8,364,993 polyhedral cells. Hot gases enter the nozzle through the core that treated as stagnation inlet at a pressure and temperature of 45023 Pa and 811.8 K, respectively. While, the cold air at pressure and temperature of 48963 Pa and 334.8 K, respectively enters via the bypass that considered as stagnation inlet. The outlet of the nozzle was treated as a pressure outlet subjected to atmospheric pressure and temperature. The nozzle body was considered as adiabatic walls with no-slip boundary conditions. The results showed that the increasing aft-deck decreased the temperature inside the nozzle and at exhausted gases that reduced the infrared temperature.

A study on the particle temperature in a conical fluidized bed using infrared thermography

Hamada Mohamed Abdelmotalib,임익태 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

Of the three main modes of heat transfer in fluidized bed reactors, surface-to-bed heat transfer has been more thoroughly studied compared to gas-to-particle or solid-to-solid heat transfer. The difficulty in studying both gas-to-solid and solid-to-solid heat transfer processes is due to a limited ability to measure the temperature of the particles. The traditional method to measure temperature, such as inserting temperature probes into the bed, do not provide accurate results because these measure the temperature of the bed and not the solid particles. The present study introduces a technique using infrared thermography to measure the particle temperature. The particle temperature was measured using an IR camera, and a type-K thermocouple was used to measure the bed temperature. Glass beads with different sizes were used as bed material fluidized by air to study the effect that the inlet gas velocity and particle size had on the particle temperature. An increase in the inlet gas velocity resulted in a decrease in the particle temperature without a noticeable effect on the bed temperature, and an increase in the particle size resulted in an increase in the temperature of both the particles and the bed.

Numerical Study on the Wall to Bed Heat Transfer in a Conical Fluidized Bed Combustor

Hamada Mohamed Abdelmotalib,Mahmoud Abdelftah Youssef,Ali Ahmed Hassan,윤석범,임익태 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

In this work a numerical investigation of wall to bed heat transfer, and the related flow characteristics, was conducted along a conical fluidized bed combustor with a height of 0.8 m and a cone angle of 30o. A two-fluid Eulerian-Eulerian model was used while applying Kinetic Theory for Granular Flow (KTGF) to a wall-to-bed FB reactor. The heat transfer coefficient and hydrodynamics are discussed for two different drag models, namely the Gidaspow and Syamlal-O’Brien models. Furthermore, computational calculations were carried out for a variety of inlet velocities(1.4Umf~4 Umf) and different particle sizes. The heat transfer coefficient in the bed region was evaluated and compared with that calculated by penetration theory. The bed expansion for the two models was compared with that calculated using correlations from literature in order to validate the numerical calculations. The heat transfer coefficient was found to be increasing with increasing gas velocity and decreasing with increasing particle diameter.

Computational study of serpentine nozzle performance with annular mixer

Hamada Mohamed(하마다 모하메드),Changwook Lee(이창욱),Heeju Choi(최희주),Jeekeun Lee(이지근) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.8

The suppression of the infrared radiation emitted from the exhaust system and high temperature walls can increase the survivability of fighter aircraft. Anon-symmetric nozzle such as serpentine nozzle is one method can be used to minimize the infrared radiation. A serpentine nozzle can reduce infrared radiation by 70%. Utilization of aft-deck decreases the external jet length and helps in shielding the high temperature sections of the turbine and engine exhaust nozzle that can reduce the IR radiation by 90%. The appropriate understanding of flow characteristics of a nozzle with aft-deck is important for the design process of the engine exhaust nozzle. To study the effect of aft-deck the flow characteristics were compared to those of nozzle without aft-deck. The simulations were carried out using the STAR CCM+ software. The grid system consists of 8,364,993 polyhedral cells was used in simulations. The bypass where cold air enters was treated as stagnation inlet subjected to pressure and temperature of 48963 Pa and 334.8 K, respectively. Core where hot gases enter, was also considered as stagnation inlet with temperature and pressure of 45023 Pa and 811.8 K, respectively. The outlet of the nozzle was treated as a pressure outlet suspected to the atmospheric temperature of 288 K. The results showed that the presence of aft-deck resulted in a slight increase of pressure along the nozzle length, decreasing the temperature of upper and lower nozzle walls, and reduce the size and length of the external jet that can reduce the infrared radiation. Moreover, the velocity at aft-deck decreased that lead to the reduction of the nozzle noise.

A numerical study on gas-to-particle and particle-to-particle heat transfer in a conical fluidized bed reactor

Mohamed Y. Hashim,Hamada M. Abdelmotalib,김종석,Dong Guk Ko,Ik-Tae Im 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6

In this present study, the particle behavior and heat transfer coefficients for particle-gas and particle-particle are found by using a computational model in a fluidization process. A conical shape is selected as a reactor due to its wide range of applications. The equations describing gas and particle motions and heat transfer are solved by using the Eulerian two-fluid approach. Glass bead particles of two different sizes (2 mm and 4 mm) are used as bed materials, and the air is used as a fluidized gas. The velocity of the gas inlet is varied from 1.3 m/s to 2.6 m/s. The results demonstrate that the particle-gas heat transfer coefficient according to the velocity of the air inlet reaches its maximum value around 2.1 m/s, then decreases thereafter. Besides, at the same velocity, the particle-particle heat transfer coefficient reaches its maximum value, then decrease thereafter with increasing the velocity of the inlet air.

Antioxidative effects of the acetone fraction and vanillic acid from Chenopodium murale on tomato plants

Ghareib, Hamada Ragab Abdo,Abdelhamed, Mohamed Sayed,Ibrahim, Ola Hammouda The Korean Society of Weed Science and The Turfgra 2010 Weed Biology and Management Vol.10 No.1

From the active acetone fraction of Chenopodium murale, vanillic acid was isolated and identified, based on $^1H$ and $^{13}C$ nuclear magnetic resonance spectral analyses. Free phenolic compounds inside the active acetone were qualified and quantified by using high performance liquid chromatography analysis, which revealed the presence of seven compounds with an abundance of vanillic and p-hydroxybenzoic acids. The allelopathic potential of the acetone fraction and vanillic acid was evaluated through laboratory bioassays against tomato plants. Our results showed that the allelopathic potential induced by low concentrations of the acetone fraction and vanillic acid stimulated the germination and growth of tomato and had stimulating effects on the activity of some antioxidant enzymes. We observed an enhancement in the activity of catalase, peroxidase, superoxide dismutase, and polyphenol oxidase, as well as the content of soluble protein and phenolic glycoside. Meanwhile, the levels of free phenolic compounds, $H_2O_2$, and lipid peroxidation decreased. The highest stimulations were recorded at 50 p.p.m. of acetone fraction and 0.5 p.p.m. of vanillic acid. In contrast, the highest concentrations exerted negative effects on all the measured parameters to record the maximum value of inhibition at 400 p.p.m. of acetone fraction and 4 p.p.m. of vanillic acid. These results proved the antioxidative effects of active acetone and vanillic acid at low concentrations and their potent use as a stimulator for tomato germination and growth.

COOLING EFFICIENCY ACCORDING TO SHAPE CHANGES TO THE STRAIGHT VENTILATION HOLE IN CARBON-CERAMIC BRAKE DISKS

고동국,Hamada Mohamed Abdelmotalib,Ik-Tae Im,Dong Won Im,Suck Ju Yoon 한국자동차공학회 2018 International journal of automotive technology Vol.19 No.6

In this study, in order to examine the cooling efficiency of a carbon-ceramic brake disk, the temperature distribution of the disk, depending on the AMS (Auto-Motor-Sport) Fade mode, was analyzed using a numerical method. Two brake disks with different straight ventilation hole shapes were considered. The ventilation holes configuration was changed from base models in order to find a higher cooling efficiency disk design. In the Model A disk, the mean temperatures of the mid-plane and the entire disk, at the AMS Fade mode end time decreased 1.9 oC and 3 oC, hole length respectively. This was done by decreasing the length of the a2 hole from 94 mm to 59 mm. When a2 hole length was increased from 94 mm to 128 mm, the mean temperature of the entire disk and the disk mid-plane increased 3.7 oC and 16.2 oC, respectively. This was due to the increased affined air stagnation in the disk. In the Model B disk, after removing stagnation region of the b2 hole, the hole diameter expanded from 13 mm to 17.6 mm. As a result, the mean temperature of the entre disk and the mid-plane decreased 2.8 oC and 18.7 oC, respectively, (compared to the base model). As a result, increasing the surface area of the ventilation holes gave a higher cooling efficiency.

Computational study on heat transfer and bed flow according to different regimes of fluidized beds

소병문,Hamada Mohamed Abdelmotalib,Mohamed Y. Hashim,임익태 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12

This work presents a computational study to compare heat transfer processes and flow behavior of the bed among different regimes of fluidized bed reactors with fixed, bubbling, and slugging flow regimes. Sand particles with a mean diameter of 550 μm were used as a bed material fluidized by air. Wall-to-bed heat transfer and fluidization behavior were studied at different inlet velocities to represent different flow regimes. A two-phase model with kinetic theory of granular flow was used to simulate both heat transfer and flow characteristics. Simulation findings were validated by comparing them with available experimental results, in which there was good agreement. The obtained results demonstrated that the gas-solid heat transfer and wall-to-bed heat transfer processes strongly depend on the bed flow structure, especially void and solid volume fractions. Slugging beds related to the highest inlet velocity achieved the best conditions of a heat transfer process, as indicated by the highest gas-solid and wall-to-bed heat transfer coefficients. Simulation results also showed that slugging behavior had no negative effect on the heat transfer process despite problems such as obstruction and entrainment.

Field Study on the Mycotoxin Binding Effects of Clay in Oreochromis niloticus Feeds and Their Impacts on the Performance as Well as the Health Status throughout the Culture Season

Abdelaziz, Mohamed,Anwer, Wael,Abdelrazek, Abeer Hamada Korean Society for Bioinformatics 2010 Interdisciplinary Bio Central (IBC) Vol.2 No.4

Total aflatoxin and ochratoxin were detected in 3 naturally contaminated fish feed samples using immune-affinity method. The results revealed that the average levels of aflatoxins in the 3 examined samples were (15, 22 and $12\;{\mu}g/kg$) respectively while the average levels of ochratoxins were (15, 6 and $6\;{\mu}g/kg$). The results of determination of the effects of clay as a mycotoxin binder on the health status and performance of Oreochromis niloticus in comparing with a control group revealed that the survival rate in control group was 81% after the end of the culture season. The results also revealed that the survival rate in group 2 which received clay treated feed was 86%. The results of regular parasitological examination revealed the identification of trichodina as external protozoa in Oreochromis niloticus from both ponds but without manifestation of disease signs. The results of bacteriological examination revealed the isolation and identification of Pseudomonas flouresence from some moribund Oreochromis niloticus. Higher performance parameters were recorded in group 2 that received feeds treated with clay which reflected in the total production which reaches 1646.47 kg while in the control pond, the total production was1308.36 kg.

The effect of different tornado wind fields on the response of transmission line structures

Nima Ezami,Nima Ezami,Ahmed Hamada,Mohamed Hamada 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.34 No.2

Majority of transmission line system failures at many locations worldwide have been caused by severe localized wind events in the form of tornadoes and downbursts. This study evaluates the structural response of two different transmission line systems under equivalent F2 tornadoes obtained from real incidents. Two multi-span self-supported transmission line systems are considered in the study. Nonlinear three-dimensional finite element models are developed for both systems. The finite element models simulate six spans and five towers. Computational Fluid Dynamics (CFD) simulations are used to develop the tornado wind fields. Using a proper scaling method for geometry and velocity, full-scale tornado flow fields for the Stockton, KS, 2005 and Goshen County WY, 2009 are developed and considered together with a previously developed tornado wind field. The tornado wind profiles are obtained in terms of tangential, radial, and axial velocities. The simulated tornadoes are then normalized to the maximum velocity value for F2 tornadoes in order to compare the effect of different tornadoes having an equal magnitude. The tornado wind fields are incorporated into a three-dimensional finite element model. By varying the location of the tornado relative to the transmission line systems, base shears of the tower of interest and peak internal forces in the tower members are evaluated. Sensitivity analysis is conducted to assess the variation of the structural behaviour of the studied transmission lines associated with the location of the tornado relative to the tower of interest. The tornado-induced forces in both lines due to the three different normalized tornadoes are compared with corresponding values evaluated using the simplified load case method recently incorporated in the ASCE-74 (2020) guidelines, which was previously developed based on the research conducted at Western University