During the explosive operation of a MFCG, the air between the armature and stator will be shocked and compressed. The resulting plasma could cause an electrical breakdown either between neighboring helix turns or between helix and armature, even before mechanical contacting occurs. When this happens, magnetic flux will be lost and the electrical efficiency of the MFCG will decrease. Therefore, the knowledge of gas temperature and pressure during the explosion phase of the MFCG's operation is vital for the assessment of the severity of energy loss due to electrical breakdown in the MFCG gas-plasma. The area with the highest temperature and pressure is expected to be close to the armature-stator contact. This makes it difficult to measure the gas temperature and pressure in the MFCG. The objective of this work was to calculate the air temperature and pressure history by combining experimental and numerical simulation results. The methodology was to first calibrate the finite element simulation model by matching the deformed armature contour obtained from actual experiments with contours obtained from numerical simulations. Then, the air temperature in a template generator (6061-T6-aluminum armature/stator) was calculated using the pressure history data obtained from numerical simulations assuming adiabatic process conditions and utilizing ideal gas equation of state, it was found that during the explosion process, the air is shocked and compressed, resulting in a moderate rise in its temperature within 2 microseconds. Following this initial stage, the air temperature remains roughly constant until immediately prior to impact of the armature with the stator when the temperature gradient rises rapidly. For a MFCG with an expansion ratio of 1.8, the pressure rise in the shocked air reached as high as 30 MPa resulting in temperature rise in the range of 2500 to 4000 degrees Kelvin.
|Journal||IEEE International Conference on Plasma Science|
|State||Published - 2001|
|Event||28th IEEE International Conference on Plasma Science/ 13th IEEE International Pulsed Power Conference - Las Vegas, NV, United States|
Duration: Jun 17 2001 → Jun 22 2001