Driving Air Pressure Research Articles

Air-Jet Driven Open-End Spinning Frame

Air jet driving and supporting devices were tested for a high speed open-end spinning frame . Two types of rotors were prepared : the upper fluting rotor and the under fluting rotor. Each rotor was driven by air jet impinging upon the fluting directly from the nozzles prepared on the inner surfaces of a stator. The rotor was supported on its under conical surface by the dynamic pressure of air thrown down by the upper flutings or of the air jet itself on the under flutings. Series of tests were made for both types of the rotors, changing their conical angles, number and angle of the flutings, and driving air pressure. The results were as follows.(1) The speed of rotor increased with increasing driving air pressure and reached the limit of speed quickly.(2) The rotor conical angle 108°was suitable for the upper fluting mechanism, and 102°was suitable for the under fluting mechanism, with a fixed stator conical angle 92°.(3) The number of flutings was suitable around 40 for the upper fluting mechanism, and 20 for the under fluting mechanism.(4) The fluting angle influenced considerably to the driving torque, the fluting angle 45° and 25°was suitable respectively for the upper fluting and the under fluting mechanism.

Vibratory Compaction of Uranium Dioxide, (II) Compaction of Sol-Gel UO2Powder with a Pneumatic Vibrator

Vibratory compaction was studied making use of a pneumatic vibrator to pack sol-gel UO2 powder in a thermal reactor type fuel canning tube. It is shown that the pneumatic vibrator utilized is superior to the commonly used electrodynamic vibrator from the view point of easy operation and high attainable density. Compared with the latter type, the pneumatic vibrator is less restrictive in the range of mesh size composing each fraction of the starting powder, and good results could be obtained with a powder with coarse, medium and fine fractions respectively having mesh ranges of 4–6 (60%), 20–65 (20%) and −200 (20%). The selected operational conditions are: vibration frequency; 300 cpm, driving air pressure; 3 kg/cm2 and duration of operation; 10 min. Fuel rods of 100cm length compacted in these conditions with sol-gel UO2 (particle density: 96%T.D.) attained a bulk density of 88.2±0.2% T.D. with an axial density distribution as uniform as ±3% T.D.

Vibratory Compaction of Uranium Dioxide, (II)

Vibratory compaction was studied making use of a pneumatic vibrator to pack sol-gel UO2 powder in a thermal reactor type fuel canning tube. It is shown that the pneumatic vibrator utilized is superior to the commonly used electrodynamic vibrator from the view point of easy operation and high attainable density. Compared with the latter type, the pneumatic vibrator is less restrictive in the range of mesh size composing each fraction of the starting powder, and good results could be obtained with a powder with coarse, medium and fine fractions respectively having mesh ranges of 4–6 (60%), 20–65 (20%) and −200 (20%). The selected operational conditions are: vibration frequency; 300 cpm, driving air pressure; 3 kg/cm2 and duration of operation; 10 min. Fuel rods of 100cm length compacted in these conditions with sol-gel UO2 (particle density: 96%T.D.) attained a bulk density of 88.2±0.2% T.D. with an axial density distribution as uniform as ±3% T.D.

Speed Control for the Air-Driven Centrifuge

A method based on some work of Thomas Davis is described for controlling the rotor speed of an air-driven ultracentrifuge. A permanent magnet mounted on the shaft of the centrifuge induces an e.m.f. in a series inductance, capacity resistance circuit which has the same frequency as the rotor. When the rotor speed approaches the resonance frequency of the circuit, energy is absorbed, and the driving air pressure versus rotor speed relation increases abruptly. By regulating the driving air pressure at a few lbs./in.2 above that necessary to maintain the speed of the centrifuge where resonance begins, the rotor speed is held constant to roughly 0.1 percent over the range of speeds employed.

AN IMPROVED AIR-DRIVEN TYPE OF ULTRACENTRIFUGE FOR MOLECULAR SEDIMENTATION

1. A description is given of the construction details and operation characteristics of an improved type of air-driven ultracentrifuge operating in vacuum and suitable for the determination of sedimentation constants of protein molecules. 2. The rotor of the centrifuge is made of a forged aluminum alloy; it is oval in shape, measures 185 mm. at its greatest diameter, and weighs 3,430 gm. It carries a transparent cell located at a distance of 65 mm. from the axis of rotation and designed to accommodate a fluid column 15 mm. high. 3. The rotor has been run repeatedly over long periods at a speed of 60,000 R.P.M., which corresponds to a centrifugal force of 260,000 times gravity in the center of the cell. At this speed no deformation of the rotor nor leakage of the cell has been observed. 4. The sharp definition of sedimentation photographs taken at high speed serves to indicate the absence of detectable vibrations in the centrifuge. 5. When a vacuum of less than 1 micron of mercury is maintained in the centrifuge chamber, the rise in the rotor temperature amounts to only 1 or 2 degrees C. after several hours' run at high speed. 6. There has been no evidence of convection currents interfering with normal sedimentation of protein molecules in the centrifugal field. 7. A driving air pressure of about 18 pounds per square inch is sufficient to maintain the centrifuge at a steady speed of 60,000 R.P.M. With a driving pressure of 80 pounds per square inch, it can be accelerated to this speed in less than 20 minutes, and also brought to rest in about the same length of time by the application of the braking system. 8. The adaptation of Svedberg's optical systems to this centrifuge for photographically recording the movement of sedimentation boundaries is described.