HIGH ALTITUDE AND HIGH SPEED STUDY

1954 ◽  
Author(s):  
DEANE N. MORRIS
Keyword(s):  
High Altitude ◽  
High Speed

A 2 × 20 Gbps hybrid MDM-OFDM–based high-altitude platform-to-satellite FSO transmission system

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Vel Murugan Gomathy ◽  
T. V. Paramasivam Sundararajan ◽  
C. Sengodan Boopathi ◽  
Pandiyan Venkatesh Kumar ◽  
Krishnamoorthy Vinoth Kumar ◽  
...  
Keyword(s):  
High Altitude ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Satellite Communication ◽  
Input Power ◽  
Transmission System ◽  
Communication Link ◽  
Space Optics ◽  
High Altitude Platform ◽  
Mode Division Multiplexing

AbstractIn the present study, the application of free space optics (FSO) transmission system to realize a long-reach high-altitude platform (HAP)-to-satellite communication link has been exploited. High-speed information transmission without interference is accomplished using orthogonal frequency division multiplexing (OFDM). Further, the information capacity of the proposed system is increased by employing mode division multiplexing (MDM). We have investigated the proposed MDM-OFDM-HAP-to-satellite FSO transmission system performance over varying FSO range, diameter of the receiver, pointing errors, and input power. Also, an improved transmission performance of the proposed system using a square root module is reported.

Experimental Investigation Into the High Altitude Relight of a Three-Cup Combustor Sector

2018 ◽  
Author(s):  
Michael J. Denton ◽  
Samir B. Tambe ◽  
San-Mou Jeng
Keyword(s):  
Pressure Drop ◽  
High Altitude ◽  
High Speed ◽  
Development Process ◽  
Recirculation Zone ◽  
Operating Conditions ◽  
Pressure Drops ◽  
High Speed Video ◽  
Air Jet ◽  
Flame Development

The altitude relight of a gas turbine combustor is an FAA and EASA regulation which dictates the successful re-ignition of an engine and its proper spool-up after an in-flight shutdown. Combustor pressure loss, ambient pressure, ambient temperature, and equivalence ratio were all studied on a full-scale, 3-cup, single-annular aviation combustor sector to create an ignition map. The flame development process was studied through the implementation of high-speed video. Testing was conducted by placing the sector horizontally upstream of an air jet ejector in a high altitude relight testing facility. Air was maintained at room temperature for varying pressure, and then the cryogenic heat exchanger was fed with liquid nitrogen to chill the air down to a limit of −50 deg F, corresponding with an altitude of 30,000 feet. Fuel was injected at constant equivalence ratios across multiple operating conditions, giving insight into the ignition map of the combustor sector. Results of testing indicated difficulty in achieving ignition at high altitudes for pressure drops greater than 2%, while low pressure drops show adequate performance. Introducing low temperatures to simulate the ambient conditions yielded a worse outcome, with all conditions having poor results except for 1%. High-speed video of the flame development process during the relight conditions across all altitudes yielded a substantial effect of the pressure drop on ignitability of the combustor. An increase in pressure drop was associated with a decrease in the likelihood of ignition success, especially at increasing altitudes. The introduction of the reduced temperature effect exacerbated this effect, further hurting ignition. High velocity regions in the combustor were detrimental to the ignition, and high area, low velocity regions aided greatly. The flame tended to settle into the corner recirculation zone and recirculate back into the center-toroidal recirculation zone (CTRZ), spreading downstream and likewise into adjacent swirl cups. These tests demonstrate the need for new combustor designs to consider adding large recirculation zones for combustor flame stability that will aid in relight requirements.

Problems of High Speed Flight as Affected by Compressibility

1938 ◽  
Vol 42 (327) ◽  
pp. 193-228 ◽  
Author(s):  
C. N. H. Lock
Keyword(s):  
Shock Waves ◽  
Drag Coefficient ◽  
High Altitude ◽  
Lower Limit ◽  
High Speed ◽  
Velocity Of Sound ◽  
Upper Limit

My lecture deals with the effect of the compressibility of air on bodies moving through it at speeds ranging from the velocity of sound (710 m.p.h. at high altitude) as an upper limit to a lower limit ranging roughly from half to threequarters the velocity of sound. Somewhere within this range will commence a very rapid increase of the drag coefficient of an aircraft as a result of the formation of local shock waves.

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.

Delamination frost heave in embankment of high speed railway in high altitude and seasonal frozen region

2018 ◽  
Vol 153 ◽  
pp. 25-32 ◽  
Author(s):  
X.Y. Wu ◽  
F.J. Niu ◽  
Z.J. Lin ◽  
J. Luo ◽  
H. Zheng ◽  
...  
Keyword(s):  
High Altitude ◽  
High Speed ◽  
Frost Heave ◽  
High Speed Railway
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