Study of Base DRAG Prediction With Chamber Pressure at Super-Sonic Flow

This paper introduces an attempt to enhance the accuracy of panel methods. A low-order panel method is selected and coupled with semi-empirical methods to enhance the accuracy of drag prediction of flying bodies at supersonic speeds. The semi-empirical methods are used to improve the accuracy of drag prediction by mathematical modelling of viscosity, base drag, and drag due to wing-body interference. Both methods were implemented by a computer program and validated against experimental and analytical results. The comparisons show that a considerable improvement has been achieved for the selected panel method for prediction of drag coefficients. In general, accuracy within an average value of -4.4% was obtained for the enhanced panel method. Such accuracy could be considered acceptable for the preliminary design stages of supersonic flying bodies such as projectiles and missiles. The developed computer program gives satisfactory results as long as the considered configurations are slender and the angles of attack are small (below stall angle). ABSTRAK: Kertas kerja ini memperkenalkan percubaan untuk mempertingkatkan ketepatan kaedah panel. Kaedah panel tertib rendah telah dipilih dan digabungkan dengan kaedah separa empirik untuk mempertingkatkan ketepatan ramalan seret objek terbang pada kelajuan supersonik. Kaedah semi empirikal yang digunakan untuk meningkatkan ketepatan jangkaan seret menggunakan model matematik bagi kelikatan, seretan dasar, dan seretan disebabkan oleh badan sayap interferens. Kedua-dua kaedah dijalankan menggunakan program komputer dan disah berdasarkan keputusan uji kaji dan analisis. Perbandingan keputusan menunjukkan peningkatan yang mendadak diperolehi melalui kaedah panel yang telah dipilih sebagai jangkaan pekali seret. Secara umumnya, ketepatan yang melingkungi nilai purata sebanyak -4.4% telah diperolehi daripada kaedah peningkatan panel. Keputusan sebegini boleh diterima untuk peringkat reka bentuk permulaan bagi objek terbang supersonik seperti projektil dan misil. Program komputer yang direka memberikan keputusan yang memuaskan selagi konfigurasi yang dipilih adalah kecil dan sudut serangan adalah rendah (di bawah sudut tegun).

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Experimental Study on Internal Mixing Sonic Flow Air Assist Atomizer for Heavy Oils

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/90-gt-006 ◽

1990 ◽

Author(s):

Ju Shan Chin ◽

Li Xing Wang

Keyword(s):

Experimental Study ◽

Flame Length ◽

Chamber Pressure ◽

Heavy Oils ◽

Air Supply ◽

Air Stream ◽

Internal Mixing ◽

Mixing Chamber ◽

Fine Spray ◽

Sonic Flow

Based on the experiences previously obtained from the experimental study of plain jet atomization under cross flowing air stream and under supersonic air flow, the authors designed and studied a serious of internal mixing sonic flow air assist atomizers for heavy oil application. The contradiction between the requirements for fine spray (for high combustion completeness) and for long flame (for flame rigidity) often existing in industrial furnace has been solved. Good data were obtained which can be used for the design of such kind atomizers. By properly choosing the configuration and geometrical dimensions of the atomizer, also by choosing suitable values for mixing chamber pressure, air–liquid ratio, it is possible to have very fine spray and desirable flame length. The results showed that the ratio of mixing chamber pressure to air supply pressure should be in the range of 0.6 to 0.7. For atmospheric pressure combustion furnace, such air assist atomizer needs 0.4 MPa compressed air to have sonic flow at nozzle exit. This type of air assist atomizer has already been put into industrial operation.

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Base drag prediction on missile configurations

10.2514/6.1993-3629 ◽

1993 ◽

Cited By ~ 2

Author(s):

F. MOORE ◽

T. HYMER ◽

F. WILCOX

Keyword(s):

Drag Prediction ◽

Base Drag

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Plume-On Base Drag Prediction Including Three-Dimensional and Real-Gas Effects

Journal of Spacecraft and Rockets ◽

10.2514/2.3680 ◽

2001 ◽

Vol 38 (2) ◽

pp. 136-142 ◽

Cited By ~ 2

Author(s):

G. Rubio ◽

A. Matesanz ◽

A. Velazquez

Keyword(s):

Three Dimensional ◽

Real Gas ◽

Real Gas Effects ◽

Drag Prediction ◽

Base Drag

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Improved Semi-Empirical Method for Power-On Base-Drag Prediction

Journal of Spacecraft and Rockets ◽

10.2514/2.3782 ◽

2002 ◽

Vol 39 (1) ◽

pp. 56-65 ◽

Cited By ~ 4

Author(s):

F. G. Moore ◽

T. C. Hymer

Keyword(s):

Empirical Method ◽

Drag Prediction ◽

Semi Empirical ◽

Base Drag

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Residual Gas Reaction in the Electron Microscope: II The Design of a Gas-Control Chamber for Quantitative Observations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100062324 ◽

1969 ◽

Vol 27 ◽

pp. 82-83

Author(s):

Chester J. Calbick ◽

Richard E. Hartman

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Local Environment ◽

Chamber Pressure ◽

Objective Lens ◽

Ion Pump ◽

Quantitative Studies ◽

Precise Knowledge ◽

Differential Pumping ◽

And Control

Quantitative studies of the phenomenon associated with reactions induced by the electron beam between specimens and gases present in the electron microscope require precise knowledge and control of the local environment experienced by the portion of the specimen in the electron beam. Because of outgassing phenomena, the environment at the irradiated portion of the specimen is very different from that in any place where gas pressures and compositions can be measured. We have found that differential pumping of the specimen chamber by a 4" Orb-Ion pump, following roughing by a zeolite sorption pump, can produce a specimen-chamber pressure 100- to 1000-fold less than that in the region below the objective lens.

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Studies of the scanning ion beam sputter-cleaned MgO crystal surface by scanning reflection electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125658 ◽

1987 ◽

Vol 45 ◽

pp. 144-145

Author(s):

H.-J. Ou ◽

J. M. Cowley ◽

A. A. Higgs

Keyword(s):

Crystal Surface ◽

Ion Beam ◽

Carbon Film ◽

Surface Region ◽

Bulk Sample ◽

Chamber Pressure ◽

Specimen Preparation ◽

Detailed Surface ◽

Gate Control ◽

Reflection Electron Microscopy

A scanning ion gun system has been installed on the specimen preparation chamber (pressure ∼5xl0-8 torr) of the VG-HB5 STEM microscope. By using the specimen current imaging technique, it is possible to use an ion beam to sputter-clean the preferred surface region on a bulk sample. As shown in figure 1, the X-Y raster-gate control of the scanning unit for the Krato Mini-Beam I is used to minimize the beam raster area down to a 800μm x800μm square region. With beam energy of 2.5KeV, the MgO cleavage surface has been ion sputter-cleaned for less than 1 minute. The carbon film or other contaminant, introduced during the cleavage process in air, is mostly removed from the MgO crystal surfaces.The immediate SREM inspection of this as-cleaned MgO surface, within the adjacent STEM microscope, has revealed the detailed surface structures of atomic steps, which were difficult to observe on the as-cleaved MgO surfaces in the previous studies.

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Electron behavior in the gaseous environment of the ESEM chamber

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166658 ◽

1996 ◽

Vol 54 ◽

pp. 838-839 ◽

Cited By ~ 2

Author(s):

S.A. Wight

Keyword(s):

Secondary Electron ◽

High Vacuum ◽

Beam Current ◽

Chamber Pressure ◽

Environmental Scanning ◽

Carbon Block ◽

Faraday Cup ◽

X Ray ◽

Gaseous Environment ◽

Working Distance

Measurements of electrons striking the sample in the Environmental Scanning Electron Microscope (ESEM) are needed to begin to understand the effect of the presence of the gas on analytical measurements. Accurate beam current is important to x-ray microanalysis and it is typically measured with a faraday cup. A faraday cup (Figure 1) was constructed from a carbon block embedded in non-conductive epoxy with a 45 micrometer bore platinum aperture over the hole. Currents were measured with an electrometer and recorded as instrument parameters were varied.Instrument parameters investigated included working distance, chamber pressure, condenser percentage, and accelerating voltage. The conditions studied were low vacuum with gaseous secondary electron detector (GSED) voltage on; low vacuum with GSED voltage off; and high vacuum (GSED off). The base conditions were 30 kV, 667 Pa (5 Torr) water vapor, 100,000x magnification with the beam centered inside aperture, GSED voltage at 370 VDC, condenser at 50%, and working distance at 19.5 mm. All modifications of instrument parameters were made from these conditions.

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