试题与答案

离心泵平衡管的作用是什么?

题型:问答题 简答题

题目:

离心泵平衡管的作用是什么?

答案:

参考答案:

从泵的出口密封环处,引一外接管至泵的入口端,这根管叫平衡管。其主要作用是平衡水泵的轴向推力,减小转子的轴向窜动,防止叶轮与外壳发生摩擦。

泵在工作时,叶轮出口排出高压水,一部分流向叶轮背后,使叶轮背后压力与出口处基本一样,而叶传输线前侧是吸入端,压力很低。这样,叶轮两侧有较大的压力差,会产生一个指向泵入口并与轴平行的轴向推力,使整个转子压向吸入侧,严重时会使叶轮与泵壳发生摩擦或撞击,影响泵的安全运行,故必须设法予以平衡。

平衡轴向推力的方法很多,如采用双吸叶轮或对称排列叶轮(多级泵),采用平衡孔、平衡盘、平衡鼓等。平衡管只是平衡轴向推力的一种方式,它是将叶轮背后的压力水,用平衡管引向入口侧,使叶轮两侧压力相平衡。这种方法结构简单,但不能完全平衡轴向推力,剩余的轴向推力,需要由专门设置的推力轴承来承担。

试题推荐
题型:单项选择题

Phyllis Wheatley is regarded as America’’s first black poet. She was born in Senegal, Africa, about 1753 and brought to America aboard a slave ship at about the age of seven. John and Susannah Wheatley bought her for three pounds at a slave auction in Boston in 1761 to be a personal servant of Mrs. Wheatley. The family had three other slaves, and all were treated with respect. Phyllis was soon accepted as one of the family, which included being raised and educated with the Wheatley’’s twin 15-year-old children, Mary and Nathaniel. At that time, most females, even from better families, could not read and write, but Mary was probably one of the best educated young women in Boston. Mary wanted to become a teacher, and in fact, it was Mary who decided to take charge of Phyllis’’s education. Phyllis soon displayed her remarkable talents. At the age of twelve she was reading the Greek and Latin classics and passages from the Bible. And eventually, Mrs. Wheatley decided Phyllis should become a Christian.At the age of thirteen Phyllis wrote her first poem. She became a Boston sensation after she wrote a poem on the death of the evangelical preacher George Whitfield in 1770. It became common practice in Boston to have "Mrs. Wheatley’’s Phyllis" read poetry in polite society. Mary married in 1771, and Phyllis later moved to the country because of poor health, as a teacher and caretaker to a farmer’’s three children. Mary had tried to interest publishers in Phyllis’’s poems but once they heard she was a Negro they weren’’t interested.Then in 1773 Phyllis went with Nathaniel, who was now a businessman, to London. It was thought that a sea voyage might improve her health. Thirty-nine of her poems were published in London as Poems on Various Subjects, Religious and Moral. It was the first book published by a black American. In 1775 Phyllis wrote a poem extolling the accomplishments of George Washington and sent it to him. He responded by praising her talents and inviting her to visit his headquarters. After both of her benefactors died in 1777, and Mary died in 1778, Phyllis was freed as a slave. She married in 1778, moved away from Boston, and had three children. But after the unhappy marriage, she moved back to Boston, and died in poverty at the age of thirty.

The word "they" in the last sentence Paragraph 2 refers to________.

A.publishers

B.poems

C.children

D.black people

查看答案
微信公众账号搜索答案