Abstract: As the background of a new inline full flow visual ferrograph, the magnetic circuit of the static magnetic field is designed, which is axial magnetized and is dual-rings nested assembly with different pole and is filled with non-magnetic materials as the bush between the rings. Starting from the magnetic charge model, combined with the scalar magnetic potential method and the generalized binomial theorem, the magnetic induction of the concentric nested dual-rings, and the eccentric nested dual-rings is respectively analytically calculated. Comparing the theoretical value of magnetic induction with the actual measured value shows that the analytical expression well reflects the rules of magnetic induction in the static magnetic field, as well as the error is discussed. At meanwhile, compared the distribution of magnetic inductions of the magnets mentioned above, the most appropriate static magnetic field is chosen to meet the need of effectively adsorbent ferromagnetic particles in the inline full-flow under the condition of the high volume of lubricant oil flow. On this basis, the designed static magnetic field is used in monitoring the performance of a new turbojet aero-engine, and then the collected debris is analyzed. The analytical result indirectly verifies that the static magnetic field can effectively adsorb ferromagnetic particles under the condition of the high volume of lubricant oil flow.

Key words: Magnetic circuit design　Analytical calculation　Monitoring performance, Static magnetic field