Hirotaka Kameya

Calculation of Two-Phase Flows in an Oil Separator by Using a Cubic Interpolated Propagation Code on Unstructured Grid Spaces

We have developed a cubic interpolated propagation (CIP) code combined with a finite volume method using unstructured grid spaces. The CIP code, which can solve both compressible and incompressible flows simultaneously, was used to calculate gas-liquid flows — in this case, waterspouts — in an oil separator. We found that waterspouts raise the oil at the bottom of the separator’s chamber and lower the efficiency of oil separation remarkably. We also found that the waterspouts can be classified as circulatory or non-circulatory and that they are caused by a low-pressure core in the discharge pipe. Furthermore, we predicted the critical conditions under which the waterspouts occur, and these predictions agree with measurements taken with a test separator.Copyright

Variational Analysis of Screw-Rotor Profiles with the Shortest Seal Line between Rotors.

Screw-rotor profiles with the shortest seal line between male and female rotors of screw compressors were analyzed by calculus of variation. Additionally, a three-dimensional seal line was directly analyzed, and the rotor profiles and the conjugate law were derived by using the seal line coordinates. The calculus of variation was applied to the seal line connecting the top point of the male rotor with the pitch point. Consequently, it was found that (1) the rotor profiles have the shortest seal line when the pressure angle is zero at the pitch point, (2) the curvature radius of each profile has a maximum along the profile, and (3) different seal lines and rotor profiles exist according to the ratio of the pitch-circle diameter to the lead of the rotor.

Development of Torque Fluctuation Reducer made of Permanent Magnets for Screw Compressors

We developed a torque-fluctuation reducer, which can almost completely cancel a screw compressors torque-fluctuation and reduce its vibration and noise. The device consists of inner and outer rings. Each ring has eight pairs of permanent-magnets arranged in a circle-one S-and-N pole pair for each of the male rotors lobes. The inner ring is fixed to the male rotor shaft, and the outer ring is fixed to the casing. Turning of the inner ring, produces magnetic forces, which in turn cause sinusoidal torque fluctuations. We tuned the reducer for a 7.5 kW oil-injected air screw compressor. With the best match, the male rotors rotational vibration decreases to less than 10% of its original. The level of noise due to meshing frequency decreases to 5 dB (A) at 1 m from the front of the compressor package.