The backflow region length in sudden-reduction oil tube is not only closely associated with its energy loss, but is also closely related to the partition between orifice plate and plug. In this paper, the characteristics of backflow region length in sudden-reduction oil tube are researched. The results illustrated that backflow region length decreases with the increase in the contraction ratio. Moreover, when Reynolds number is more than 105, Reynolds number has little impact on backflow region length. Empirical expression about backflow region length in sudden-reduction oil tube is also discussed in this paper.

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Through the intelligent control of single chip microcomputer and Hall sensor detection technology and signal transmission technology, the frequency, voltage and voltage phase of the shore power and the ship power are detected to form the lowest point of voltage difference envelope, and the seamless connection of the shore power and the ship power is controlled. The load transfer control between the shore power and the ship power realizes the ideal synchronous control of grid-connected closing and load transfer by establishing the ratio control of frequency difference between the shore power and the ship power and power change during load transfer.

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