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Air Entrainment (air + entrainment)
Selected AbstractsNumerical simulation of gaseous fuel injection: A new methodology for multi-dimensional modellingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2010Luca Andreassi Abstract The use of natural gas (instead of liquid or solid fuels) is nowadays drawing an increasing interest in many applications (gas turbines, boilers, internal combustion engines), because of the greater attention to environmental issues. To facilitate the development of these applications, computer models are being developed to simulate gaseous injection, air entrainment and the ensuing combustion. This paper introduces a new method for modelling the injection process of gaseous fuels that aims to hold down grid requirements in order to allow the simulation also of other phenomena, like combustion or valve and piston motion, in reciprocating internal combustion engines. After a short overview of existing models, the transient jet model and the evaluation of inflow conditions are described in detail. Then a basic study of the grid effects on the jet evolution is presented. The model is updated and validated by comparing numerical results with available experimental data for two different operating conditions: a subsonic and a supersonic under-expanded case. The model demonstrates to be fast enough to be used in a multi-dimensional code and accurate enough to follow the real gas jet evolution. Copyright © 2009 John Wiley & Sons, Ltd. [source] Operating windows of slot die coating: Comparison of theoretical predictions with experimental observationsADVANCES IN POLYMER TECHNOLOGY, Issue 1 2010Chi-Feng Lin Abstract The objective of the present study is to examine the validity of the theoretical predictions on the operating windows of slot die coating. The operating window is defined as a domain inside which stable and uniform coating is possible; different types of coating defects are found outside the window. A flow visualization technique was applied to observe the coating bead, particularly the positions and shapes of the downstream and upstream menisci, just before and after coating defects appear at high coating speeds. Special features of coating bead shapes, which lead to onsets of ribbing and air entrainment, were identified. The two-dimensional flow in the coating bead region was computed by the commercial software package FLOW-3D®. Critical features observed experimentally for the onset of coating defects were used to judge whether the coating flow was within the operating window. The theoretically evaluated operating windows were found to be much larger than those determined experimentally in terms of coating speeds. However, the qualitative trends of theoretical predictions agree with experimental observations. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:31,44, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20173 [source] The role of volatile semiochemicals in mediating host location and selection by nuisance and disease-transmitting cattle fliesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2004M. A. Birkett Abstract., The role of volatile semiochemicals in mediating the location and selection within herds of Holstein-Friesian heifers by nuisance and disease-transmitting cattle flies was investigated using coupled gas chromatography,electrophysiology (GC,EAG), coupled gas chromatography,mass spectrometry (GC,MS), electrophysiology (EAG), laboratory behaviour and field studies. Using volatile extracts collected by air entrainment from heifers in the Netherlands, a number of active peaks were located by coupled GC,EAG for Musca autumnalis (de Geer) (Diptera: Muscidae) and Haematobia irritans (L.) (Diptera: Muscidae). Volatile samples were also collected from two heifers in Denmark shown in previous counting experiments to differ significantly in their fly loads. Coupled GC,EAG using Ha. irritans antennae revealed differences in the EAG response to the samples, with additional EAG activity in the sample collected from the heifer with the lower fly load. To identify more EAG active compounds, volatiles were also collected from 48-h-old urine by air entrainment. In total, 23 compounds were located and identified by coupled GC,EAG and GC,MS. Further electrophysiological testing of these compounds with five fly species [M. autumnalis, Ha. irritans, Hydrotaea irritans (L.) (Diptera: Muscidae), Stomoxys calcitrans (L.) (Diptera: Musicidae) and Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae)] showed that only some of the compounds were physiologically active across the range of flies tested. These included 1-octen-3-ol, 6-methyl-5-hepten-2-one, (Z)-3-hexen-1-ol, naphthalene, and all EAG active compounds identified from urine. Compounds showing significant EAG activity were tested for behavioural activity using a wind-tunnel designed for measuring upwind flight behaviour. At certain concentrations, 1-octen-3-ol, 6-methyl-5-hepten-2-one and 3-octanol increased upwind flight, whereas naphthalene, propyl butanoate and linalool reduced upwind flight. In field studies using small herds of heifers ranked according to their fly load, individual slow-release formulations of 1-octen-3-ol and 6-methyl-5-hepten-2-one, when applied to low and high fly loading heifers, reduced fly loads on these individuals. This study provides evidence for the hypothesis that the natural differential attractiveness within herds of Holstein-Freisian heifers, i.e. a single host species, for cattle flies is partly due to differences in volatile semiochemicals emitted from the host. It is suggested that this phenomenon applies to other vertebrate host species and their associated insect pests. [source] The effects of polymer additives on the operating windows of slot coatingPOLYMER ENGINEERING & SCIENCE, Issue 10 2004C. K. Yang An experimental study was carried out to investigate the effects of polymer additives on the operating windows of slot coating. Two polymer additives,carboxylmethylcellolose (CMC) and polyacrylamide (PAA),were added to Newtonian glycerin solutions as test fluids. The flow experiment was performed on a lab coater. A flow visualization technique was employed to observe the shapes of coating beads. It was found that three types of defects appear at the lower bound of the operating window, i.e., ribbing, air entrainment, and break lines coupled with dripping. Adding a small amount of polymer additives has little effect on the operating window if the defect is ribbing, but it will expand the air entrainment region. The coating speed can be increased significantly if the defect is break lines coupled with dripping. Polym. Eng. Sci. 44:1970,1976, 2004. © 2004 Society of Plastics Engineers. [source] ,Continuous saline flow technique' prevents air entrainment during intrapleural blockANAESTHESIA, Issue 1 2003P Nalwaya No abstract is available for this article. [source] Slot die coating of dilute suspensionsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009Yi-Tsun Lin Abstract An experimental study was carried out to investigate slot die coating of dilute suspensions. Polymethyl methacrylate (PMMA) particles of different sizes were added to glycerol solutions as test fluids. The coating flow experiment was performed on a lab coater. The operating window, which is a domain in which only a stable and uniform coating solution is possible, was determined experimentally. It was found that adding particles has little effect on the physical properties of glycerol solutions, as only the fluid viscosity increases slightly. Two coating defects are commonly observed; ribbing which is caused by flow instability refers to lateral waves on the coated surface, and air entrainment which implies that air bubbles are trapped in the coating solution. Adding particles has little effect on the operating window if the coating defect is ribbing. However, the operating window can be expanded substantially if the coating defect is air entrainment. Higher the particle concentration, or the smaller the particle size, more significant is the expansion of the operating window. The maximum coating speed may increase to 80% for high suspension particle density number. A previous study reported that there exists an optimal particle size which has the largest operating window for a given pure solution; this was not found in the present work. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||