Primary air entrainment characteristics for a self-aspirating burner: Model and experiments

AbstractTotal dissolved gas (TDG) supersaturation, which occurs during dam spilling, may result in fish bubble disease and mortality. Many studies have been conducted to identify the factors pertaining to TDG generation, such as the spilling discharge and tailwater depth. Additionally, the energy dissipation efficiency should be considered due to its effect on the air entrainment, which influences the TDG generation process. According to the TDG field observations of 49 cases at Dagangshan and Xiluodu hydropower stations, the TDG was positively related to the energy dissipation efficiency, tailwater depth and discharge per unit width. A correlation between the generated TDG level and these factors was established. The empirical equations proposed by the USACE were calibrated, and the TDG level estimation performance was compared with the established correlation for 25 spillage cases at seven other dams. Among the considered cases, the standard error of the TDG estimation considering the energy dissipation efficiency was 5.7%, and those for the correlations obtained using the USACE equations were 13.0% and 10.0%. The findings indicated that the energy dissipation efficiency considerably influenced the TDG level, and its consideration helped enhance the precision of the TDG estimation. Finally, the generality of this approach and future work were discussed.

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Design and Fabrication of a Novel Window-Type Convection Device

Applied Sciences ◽

10.3390/app11010267 ◽

2020 ◽

Vol 11 (1) ◽

pp. 267

Author(s):

Han-Tang Lin ◽

Yunn-Horng Guu ◽

Wei-Hsuan Hsu

Keyword(s):

Energy Consumption ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Energy Demand ◽

Air Entrainment ◽

Wind Speeds ◽

Digit Series ◽

Slit Size ◽

Deflector Plate

Global warming, climate change, and ever-increasing energy demand are among the pressing challenges currently facing humanity. Particularly, indoor air conditioning, a major source of energy consumption, requires immediate improvement to prevent energy crises. In this study, various airfoil profiles were applied to create a window-type convection device that entrains air to improve convection between indoor and outdoor airflows and adjust the indoor temperature. How the geometric structure of the convection device affects its air entrainment performance was investigated on the basis of various airfoil profiles and outlet slit sizes of the airflow multiplier. The airfoil profiles were designed according to the 4-digit series developed by the National Advisory Committee for Aeronautics. The results revealed that airfoil thickness, airfoil camber, and air outlet slit size affected the mass flow rate of the convection device. Overall, the mass flow rate at the outlet of the convection device was more than 10 times greater than at the inlet, demonstrating the potential of the device to improve air convection. To validate these simulated results, the wind-deflector plate was processed using the NACA4424 airfoil with a 1.2 mm slit, and various operating voltages were applied to the convection device to measure the resulting wind speeds and calculate the corresponding mass flow rates. The experimental and simulated results were similar, with a mean error of <7%, indicating that the airfoil-shaped wind-deflector plate substantially improved air entrainment of the convection device to the goal of reduced energy consumption and carbon emissions.

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Evaluation of a Humidified Nasal High-Flow Oxygen System, Using Oxygraphy, Capnography and Measurement of Upper Airway Pressures

Anaesthesia and Intensive Care ◽

10.1177/0310057x1103900620 ◽

2011 ◽

Vol 39 (6) ◽

pp. 1103-1110 ◽

Cited By ~ 121

Author(s):

J. E. Ritchie ◽

A. B. Williams ◽

C. Gerard ◽

H. Hockey

Keyword(s):

Healthy Volunteers ◽

Airway Pressure ◽

Gas Flow ◽

Air Entrainment ◽

High Flow ◽

Positive Pressure ◽

Mean Airway Pressure ◽

Flow Rates ◽

Oxygen Fraction ◽

Airway Pressures

In this study, we evaluated the performance of a humidified nasal high-flow system (Optiflow™, Fisher and Paykel Healthcare) by measuring delivered FiO2 and airway pressures. Oxygraphy, capnography and measurement of airway pressures were performed through a hypopharyngeal catheter in healthy volunteers receiving Optiflow™ humidified nasal high flow therapy at rest and with exercise. The study was conducted in a non-clinical experimental setting. Ten healthy volunteers completed the study after giving informed written consent. Participants received a delivered oxygen fraction of 0.60 with gas flow rates of 10, 20, 30, 40 and 50 l/minute in random order. FiO2, FEO2, FECO2 and airway pressures were measured. Calculation of FiO2 from FEO2 and FECO2 was later performed. Calculated FiO2 approached 0.60 as gas flow rates increased above 30 l/minute during nose breathing at rest. High peak inspiratory flow rates with exercise were associated with increased air entrainment. Hypopharyngeal pressure increased with increasing delivered gas flow rate. At 50 l/minute the system delivered a mean airway pressure of up to 7.1 cmH2O. We believe that the high gas flow rates delivered by this system enable an accurate inspired oxygen fraction to be delivered. The positive mean airway pressure created by the high flow increases the efficacy of this system and may serve as a bridge to formal positive pressure systems.

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Fire-induced temperature distribution beneath ceiling and air entrainment coefficient characteristics in a tunnel with point extraction system

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2018.08.023 ◽

2018 ◽

Vol 134 ◽

pp. 363-369 ◽

Cited By ~ 17

Author(s):

Fei Tang ◽

Qing He ◽

Fengzhu Mei ◽

Qin Shi ◽

Lei Chen ◽

...

Keyword(s):

Temperature Distribution ◽

Air Entrainment ◽

Extraction System ◽

Entrainment Coefficient

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Development of Laminar Plasma Shielded HF-ERW Process: Advanced Welding Process of HF-ERW 3

Volume 3: Materials and Joining ◽

10.1115/ipc2012-90214 ◽

2012 ◽

Cited By ~ 4

Author(s):

Hideki Hamatani ◽

Funinori Watanabe ◽

Nobuo Mizuhashi ◽

Sunao Takeuchi ◽

Yoshiaki Hirota ◽

...

Keyword(s):

High Temperature ◽

Welding Process ◽

Air Entrainment ◽

Plasma Jets ◽

Control Technique ◽

Monitoring Methods ◽

Line Pipe ◽

Temperature State ◽

Weld Area ◽

Cold Gas

High frequency - electric resistance welded (HF-ERW) pipe has been successfully used for many years for a number of applications. The benefits of HF-ERW pipe are considerable, including a higher dimensional tolerance and lower prices than seamless pipe and UO pipe. The conventional weld seam produced by HF-ERW, however, often has a relatively low toughness. We have developed an automatic heat input control technique based on ERW phenomena that relies on optical and electrical monitoring methods and has been shown to result in a significant improvement in the toughness. Shielding of the weld area must also be considered as a key factor in the formation of a sound weld. It has been shown that an inert cold gas (e.g., at room temperature) shielding technique is effective for maintaining a stable low oxygen state in the weld area that inhibits the formation of penetrator, a pancake oxide inclusions. Compared to the cold gas shielding technique, high temperature gas shielding, due to its higher kinetic viscosity coefficient, should make it easier to sustain a higher laminar flow, thus leading to a rather low air entrainment in the shielding gas. In addition, plasma is a much higher temperature state (∼6000 K), and the dissociated gases can react with the entrained oxygen; plasma jets should, therefore, enhance the overall shielding effects. Moreover, oxides on the strip edges can be expected to melt and/or be reduced by the high temperature plasma jets. Nippon Steel has developed a plasma torch that can generate a long and wide laminar argon – nitrogen – (hydrogen) jet. This paper describes the results obtained from our investigation of the effects of a plasma jet shield on the weld area of high strength line pipe with a yield strength grade of X65. Preliminary attempts in applying this novel shielding technique has been found, as expected, to demonstrate extremely low numbers of weld defects and a good low temperature toughness of the HF-ERW seam.

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