The influence of wall roughness on detonation limits in hydrogen–oxygen mixture

2016 ◽  
Vol 169 ◽  
pp. 333-339 ◽  
Author(s):  
Bo Zhang
Author(s):  
Chan-Yu Wang ◽  
Jun-Kai Wang ◽  
Ming-Hsun Wu

Reaction propagation of ethylene/oxygen and methane/oxygen mixtures in capillary tubes of 1 and 2 mm in diameters with initial pressure and temperature at ambient condition were experimentally visualized and analysed using high speed cinematography. Deflagrative flame was initiated in middle of the smooth tube, and the reaction fronts accelerated as they propagated towards the exits in the opposite directions. Lengths of the tubes investigated ranged from 0.4 to 1 m (one side), and deflagration-to-detonation transitions were observed for equivalence ratios between 0.5 and 3. The visible reaction front propagates at speeds approach Chapman-Jouguet speed for ethylene/oxygen mixture in the 1 mm and 2 mm tubes. An overshoot in propagation velocity was found during transition process. For leaner and richer mixtures beyond the detonation limits, steady deflagration wave propagation was observed. Reaction propagation in methane/oxygen mixture was also investigated. Several near-limit propagation modes were found.


2019 ◽  
Vol 37 (3) ◽  
pp. 3609-3616 ◽  
Author(s):  
Shinichi Maeda ◽  
Masashi Fujisawa ◽  
Shogo Ienaga ◽  
Keisuke Hirahara ◽  
Tetsuro Obara

Detonation parameters have been determined for fuel+ oxygen mixtures for ambient pressure and temperature in a 1 in (2.54 cm) diameter tube, with initiating impact from a detonating stochiometric hydrogen + oxygen mixture. Detonation limits in mole percent fuel are : methane 8.25 and 55.80 n -propane 2.50 and 42.50 n -butane 2.05 and 37.95 neopentane 1.50 and 33.00 propylene 2.50 and 50.00 These data have been matched with comparable results for the systems oxygen + ethane and oxygen + ethylene, obtained in other researches, in order to establish behaviour in homologous series of com pounds. For all compositions, propagation of detonation can usefully be correlated to the Mach product v M 2 . Far-reaching correlations are found for different hydrocarbon molecules, when the data are transformed on a homology basis. This suggests that the structure of the fuel molecules has only a secondary influence. At the fuel-lean limits, marginal behaviour can be interpreted in terms of a critical tem­perature rise which may be related to a critical rate of an initial cracking mechanism . Near the fuel-rich limits it seems more likely that stability depends on the condensation of (carbonaceous) solids from a mixture of cracking products.


2019 ◽  
Vol 2 (31) ◽  
pp. 46-51
Author(s):  
D. A. Temerov ◽  
L. V. Vorobyova ◽  
S. V. Vyzhevsky ◽  
S. B. Savchenkov ◽  
Yu. V. Marchenkov

The article presents a clinical case of successful treatment of a patient with prolonged asthmatic status. The pathogenesis of purulent-septic and other life-threatening complications developing as a result of the above critical condition is described. The positive effect of a differentiated approach in conducting respiratory support depending on the stage of the disease is justified: at the beginning, when airway obstruction is in the foreground, and in the future, when restrictive respiratory disorders develop. When conducting respiratory support, the most reasonable methods for ensuring airway patency were selected. The necessity of neurovegetative blockade and myoplegia for the prevention of pulmonary barotrauma during respiratory support by aggressive ventilation modes and with the goal of antihypoxic protection of the brain is emphasized. During the treatment of the patient, it was confirmed that the optimal regime for obstruction of the bronchi is forced volume-cyclic ventilation of the lungs to provide the necessary minute volume of breathing, and in severe pneumonia, in the case of relief of bronchial obstruction, respiratory support is carried out in pressure control mode for better air-oxygen mixture distribution in the airways. The need for early tracheostomy and daily therapeutic fibrobronchoscopy to ensure airway patency and treat pneumonia has been confirmed.


2008 ◽  
Vol 128 (8) ◽  
pp. 325-330 ◽  
Author(s):  
Hiroaki Kawata ◽  
Junya Ishihara ◽  
Masayo Kayama ◽  
Masaaki Yasuda ◽  
Yoshihiko Hirai
Keyword(s):  

2016 ◽  
Vol 48 (6) ◽  
pp. 9-21
Author(s):  
Andrey V. Kipenskiy ◽  
Evgeniy I. Nazarov ◽  
Tatyana А. Glukhenkaya

2021 ◽  
Vol 37 (1) ◽  
pp. 151-166
Author(s):  
Guillaume Pelletier ◽  
Marc Ferrier ◽  
Axel Vincent-Randonnier ◽  
Vladimir Sabelnikov ◽  
Arnaud Mura

Author(s):  
V. S. Teslenko ◽  
◽  
A. P. Drozhzhin ◽  
R. N. Medvedev ◽  
◽  
...  
Keyword(s):  

The results of experiments on measurements of pulses of thrust force and bubble pulsations generated on a flat thrust wall due to combustion of a stoichiometric propane-oxygen mixture are presented.


Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.


2021 ◽  
Author(s):  
D. V. Dukhopelnikov ◽  
V. A. Riazanov ◽  
S. O. Shilov ◽  
D. S. Manegin ◽  
R. A. Sokolov

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