scholarly journals An Experimental Study on the Effects of Atomized Rain of a High Velocity Waterjet to Downstream Area in Low Ambient Pressure Environment

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 397
Author(s):  
Dan Liu ◽  
Jijian Lian ◽  
Fang Liu ◽  
Dongming Liu ◽  
Bin Ma ◽  
...  
Keyword(s):  
High Altitude ◽  
Ambient Pressure ◽  
Enhancement Effect ◽  
Rain Intensity ◽  
Contributing Factors ◽  
Flood Discharge ◽  
Resistance Reduction ◽  
Dimensional Distribution ◽  
Inflow Discharge ◽  
Average Rain

A better understanding of the atomized rain characteristics in low ambient pressure areas is beneficial in reducing the jeopardizing effect of flood discharge atomization on high-altitude hydropower stations. A random splash experiment is designed with two measurement planes to investigate the effects of low ambient pressure on downstream atomized rain under the complicated conditions of low ambient pressure (within 0.60P0~1.00P0) and high waterjet velocity (at a magnitude of 10 m/s). The results demonstrate that the atomized rain (rain intensity ≥ 2 mm/h) downstream, characterized by two-dimensional distribution, can be enhanced by decreasing the ambient pressure and by increasing the inflow discharge. When the ambient pressure decreases at the same inflow discharge, both the distance of the rain intensity lines (40 mm/h, 10 mm/h, 2 mm/h) in the horizontal plane from the constricted nozzle outlet and the average rain amount in the inclined plane within the atomized source ratio of ((0~30) × 10−3)% appear as “linear” growth. With the ambient pressure decreasing by 0.10P0, the range of those characteristic rain intensity lines is expanded by 0.68%~1.37%, and the average rain amount is enlarged by 11.06%~20.48%. When keeping the low ambient pressure unchanged, both the point average rain intensity reduction along the releasing centerline and the surface average rain amount growth with increased inflow discharge all follow an exponential function. The aeration reduction in the waterjet boundary and the resistance reduction in atomized water-droplets are contributing factors for the enhancement effect of low ambient pressure. This study can enable the establishment of a foundation to further predict flood discharge atomization in a high-altitude environment.

scholarly journals Occurrence of high altitude cerebral edema (hace) and high altitude pulmonary edema (HAPO) simultaneously at 12000 ft: a rare phenomen

2018 ◽  
Vol 5 (4) ◽  
pp. 1075
Author(s):  
Dharmendra Kumar ◽  
T. K. Rath ◽  
L. C. Verma
Keyword(s):  
Pulmonary Edema ◽  
High Altitude ◽  
Cerebral Edema ◽  
Standard Protocol ◽  
Contributing Factors ◽  
Lower Altitude ◽  
High Altitude Pulmonary Edema ◽  
High Altitude Cerebral Edema ◽  
Rapid Ascent ◽  
Male Sex

High altitude cerebral edema (HACE) and High altitude pulmonary edema (HAPO) are the most dreaded complications related to high altitude. Authors managed a case of HACE and HAPO simultaneously set at unusually low height (1200 ft) in a patient. The altitude was not too much to develop these comorbidities as studied earlier. Relationship with altitude was immaterial in our case. However, rapid ascent without proper acclimatisation, young and tender age, male sex and smoking were associated contributing factors. He was managed with standard protocol and descent to lower altitude.

Numerical Analysis of the Primary Breakup Under High-Altitude Relight Conditions Applying the Embedded DNS Approach to a Generic Prefilming Airblast Atomizer

2013 ◽  
Author(s):  
Benjamin Sauer ◽  
Nikolaos Spyrou ◽  
Amsini Sadiki ◽  
Johannes Janicka
Keyword(s):  
Surface Tension ◽  
Boundary Conditions ◽  
High Altitude ◽  
Ambient Pressure ◽  
Planar Geometry ◽  
Slight Variation ◽  
Strong Impact ◽  
Wall Film ◽  
Primary Breakup ◽  
Liquid Wall

The primary breakup under high-altitude relight conditions is investigated in this study where ambient pressure is as low as 0.4 bar and air, fuel and engine parts are as cold as 265 K. The primary breakup is crucial for the fuel atomization. As of today, the phenomena dictating the primary breakup are not fully understood. Direct Numerical Simulations (DNS) of liquid breakup under realistic conditions and geometries are hardly possible. The embedded DNS (eDNS) approach represents a reliable numerical tool to fill this gap. The concept consists of three steps: a geometry simplification, the generation of realistic boundary conditions for the DNS and the DNS of the breakup region. The realistic annular airblast atomizer geometry is simplified to a Y-shaped channel representing a planar geometry. Inside this domain the eDNS is located. The eDNS domain requires the generation of boundary conditions. A Large Eddy Simulation (LES) of the entire Y-shaped channel and a Reynolds-Averaged Navier-Stokes Simulation (RANS) of the liquid wall film are performed prior to the DNS. All parameters are stored transiently on all virtual DNS planes. These variables are then mapped to the DNS. Thus, high-quality boundary conditions are generated. The Volume-of-Fluid (VOF) method is used to solve for the two-phase flow. The results provide a qualitative insight into the primary breakup under realistic high-altitude relight conditions. Instantaneous snapshots in time illustrate the behavior of the liquid wall film along the prefilmer lip and illustrate the breakup process. It is seen that a slight variation of the surface tension force has a strong impact on the appearance of the primary breakup. Case 1 with the surface tension corresponding to kerosene at 293 K indicates large flow structures that are separated from the liquid sheet. By lowering the surface tension related to kerosene at 363 K, the breakup is dominated by numerous small structures and droplets. This study proves the applicability of the eDNS concept for investigating breakup processes as the transient nature of the phase interface behavior can be captured. At this time, the authors only present a qualitative insight which can be explained by the lack of quantitative data. The approach offers the potential of simulating realistic annular highly-swirled airblast atomizer geometries under realistic conditions.

scholarly journals Analysis of Diesel Knock for High-Altitude Heavy-Duty Engines Using Optical Rapid Compression Machines

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3080
Author(s):  
Xiangting Wang ◽  
Haiqiao Wei ◽  
Jiaying Pan ◽  
Zhen Hu ◽  
Zeyuan Zheng ◽  
...  
Keyword(s):  
High Altitude ◽  
High Speed ◽  
Ambient Pressure ◽  
Critical Conditions ◽  
Heavy Duty ◽  
Pressure Oscillations ◽  
Spray Impingement ◽  
Rapid Compression ◽  
The Given ◽  
Injection Pressures

In high altitude regions, affected by the low-pressure and low-temperature atmosphere, diesel knock is likely to be encountered in heavy-duty engines operating at low-speed and high-load conditions. Pressure oscillations during diesel knock are commonly captured by pressure transducers, while there is a lack of direct evidence and visualization images, such that its fundamental formation mechanism is still unclear. In this study, optical experiments on diesel knock with destructive pressure oscillations were investigated in an optical rapid compression machine. High-speed direct photography and simultaneous pressure acquisition were synchronically performed, and different injection pressures and ambient pressures were considered. The results show that for the given ambient temperature and pressure, diesel knock becomes prevalent at higher injection pressures where fuel spray impingement becomes enhanced. Higher ambient pressure can reduce the tendency to diesel knock under critical conditions. For the given injection pressure satisfying knocking combustion, knock intensity is decreased as ambient pressure is increased. Further analysis of visualization images shows diesel knock is closely associated with the prolonged ignition delay time due to diesel spray impingement. High-frequency pressure oscillation is caused by the propagation of supersonic reaction-front originating from the second-stage autoignition of mixture. In addition, the oscillation frequencies are obtained through the fast Fourier transform (FFT) analysis.

scholarly journals Oxygen Saturation of Hemoglobin in Healthy Children of 2- 14 Years at High Altitude in Nepal

2012 ◽  
Vol 10 (1) ◽  
pp. 30-33
Author(s):  
S Shrestha ◽  
S Shrestha ◽  
L Shrestha ◽  
N Bhandary
Keyword(s):  
Oxygen Saturation ◽  
High Altitude ◽  
Healthy Children ◽  
Older Children ◽  
Contributing Factors ◽  
Lower Altitude ◽  
Value Of Children ◽  
The Mean ◽  
The Difference ◽  
Different Altitudes

Background Individuals residing at higher altitude may have oxygen saturation of hemoglobin different to those living at lower altitude. # Objectives To find out the baseline value of SpO2 in healthy Nepali children (2-14 years) living permanently at high altitude using pulse oximeter and also to study the relation of SpO2 with age, sex and ethnicity. Methods A descriptive observational study was conducted at 4 different altitudes ranging from 2700 to 3800 m in Mustang district. The mean pulse oximery values at different altitudes were calculated and compared. Results One hundred six children were enrolled with the median age of 10 years. The mean SpO2 value of children permanently residing at altitude 2700m was 95.18%, at 2800m was 94.82%, at 3550m was 94.1% and 3800m was 93.1%.The difference in the SpO2 values at different altitude was statistically significant. No sex or age wise differences were noted on the mean SpO2 values in the study group. Conclusions The mean SpO2 values were higher than several other studies done in the altitude above 2500 meters. Enrollment of older children and the different ethnic background could be the contributing factors for the differences. KATHMANDU UNIVERSITY MEDICAL JOURNAL  VOL.10 | NO. 1 | ISSUE 37 | JAN - MAR 2012 | 40-43 DOI: http://dx.doi.org/10.3126/kumj.v10i1.6912

Inflammability and Electrical Studies of Foams Which may Occur at Altitude by De-Aeration of Aviation Turbine Fuels

1959 ◽  
Vol 63 (586) ◽  
pp. 581-588 ◽  
Author(s):  
B. V. Poulston ◽  
A. Thomas
Keyword(s):  
High Altitude ◽  
Sea Level ◽  
Atmospheric Pressure ◽  
Ambient Pressure ◽  
Electrical Charge ◽  
Air Bubbles ◽  
Electrical Studies ◽  
To Come ◽  
Short Time

Air dissolves in aircraft fuels to an extent directly proportional to the ambient pressure, so that when fuel which has been stored at sea-level atmospheric pressure is taken up to a high altitude, there is a tendency for air to come out of solution. In certain circumstances, which are later described in detail, air bubbles can be liberated very violently from fuels in aircraft tanks at high altitude and a thick foam can form on the surface for a short time.The production of fuel foams by degassing has posed a certain problem; foams, being intimate mixtures of air and fuel, may well be inflammable; furthermore, the rising of air bubbles through fuel can result in the accumulation of electrical charge in the foam giving rise to the possibility of a source of ignition.

Problems related to the tests of resistance and strength of military equipment in reduced atmospheric pressure conditions

2019 ◽  
Vol 124 ◽  
pp. 151-159
Author(s):  
Patryk Płochocki ◽  
Mateusz Makarewicz ◽  
Przemysław Simiński
Keyword(s):  
High Altitude ◽  
Working Conditions ◽  
Atmospheric Pressure ◽  
Ambient Pressure ◽  
Air Transport ◽  
Normative Documents ◽  
Military Equipment ◽  
The Subject

This article is about military equipment research in conditions of reduced atmospheric pressure. Reported cases of equipment damage during work at high altitude or air transport show the need to perform research on phenomena occurring during storage, transport and operation of equipment at a reduced ambient pressure. One of the fragments of the article is devoted to the records contained in normative documents regarding the subject of the study. In addition, an exemplary experiment was made, the purpose of which was to illustrate some of the effects associated with the use of the equipment in the above-mentioned working conditions.

Fouling propensity of forward osmosis: investigation of the slower flux decline phenomenon

2010 ◽  
Vol 61 (4) ◽  
pp. 927-936 ◽  
Author(s):  
Winson C. L. Lay ◽  
Tzyy Haur Chong ◽  
Chuyang Y. Tang ◽  
Anthony G. Fane ◽  
Jinsong Zhang ◽  
...  
Keyword(s):  
Membrane Fouling ◽  
Ambient Pressure ◽  
Pure Water ◽  
Forward Osmosis ◽  
Hydraulic Pressure ◽  
Contributing Factors ◽  
Draw Solution ◽  
Flux Decline ◽  
Internal Concentration ◽  
Quality Water

Forward Osmosis (FO) is a membrane process that uses the natural osmotic pressure of a concentrated draw solution to extract pure water from a feed stream. The attraction of the FO process is that it uses dense membranes, while operating at ambient pressure. This means that the FO process could potentially produce high quality water with lower energy consumption, as compared to the other desalination or reclamation processes. As FO does not entail the use of hydraulic pressure, FO has been hypothesized to have lower fouling propensity than pressure driven membrane processes. Membrane fouling has significant impact on the operational sustainability and economics of the process. This study examines the possible contributing factors to the slower flux decline observed in FO experiments based on a combined experimental and modelling approach. It was found that these factors could include low water fluxes, use of hydrophilic and smooth membranes, and the effect of internal concentration polarisation that is inherent of FO. It was also found that the transmission of draw solutes from the draw solution into the feed can have significant effect on FO performance.

scholarly journals Experimental characterization of the COndensation PArticle counting System for high altitude aircraft-borne application

2008 ◽  
Vol 1 (1) ◽  
pp. 321-374 ◽  
Author(s):  
R. Weigel ◽  
M. Hermann ◽  
J. Curtius ◽  
C. Voigt ◽  
S. Walter ◽  
...  
Keyword(s):  
High Altitude ◽  
Ambient Pressure ◽  
Particle Diameter ◽  
The Arctic ◽  
Working Fluid ◽  
Counting System ◽  
Dual Channel ◽  
Particle Counting ◽  
Condensation Particle Counting

Abstract. This study aims at a detailed characterization of an ultra-fine aerosol particle counting system for operation on board the Russian high altitude research aircraft M-55 "Geophysica" (maximum ceiling of 21 km). The COndensation PArticle counting Systems (COPAS) consists of an aerosol inlet and two dual-channel continuous flow Condensation Particle Counters (CPCs). The aerosol inlet, adapted for COPAS measurements on board the M-55 "Geophysica", is described concerning aspiration, transmission, and transport losses. The counting efficiencies of the CPCs using the chlorofluorocarbon FC-43 as the working fluid are studied experimentally at two pressure conditions, 300 hPa and 70 hPa. Three COPAS channels are operated with different temperature differences between the saturator and the condenser block yielding smallest detectable particle sizes (dp50 – as 50% detection "cut off" diameters) of 6 nm, 11 nm, and 15 nm, respectively, at ambient pressure of 70 hPa. The fourth COPAS channel is operated with an aerosol heating line (250°C) for a determination of the non-volatile number of particles. The heating line is experimentally proven to volatilize pure H2SO4-H2O particles for a particle diameter (dp) range of 11 nm<dp<200 nm. Additionally this study includes investigation to exclude auto-nucleation of the working fluid inside the CPCs. An instrumental inter-comparison (cross-correlation) has been performed for several measurement flights and mission flights in the Arctic and the Tropics are discussed. Finally, COPAS measurements are used for an aircraft plume crossing analysis.

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