16. Thermoacoustic Engine 热声发动机

A piston placed in the open end of a horizontal test tube which has its other end partially filled with steel wool may oscillate when the closed end is heated up. Investigate the phe­no­menon and determine the efficiency of this engine.

一根水平放置的试管，开口端有一活塞，封闭端塞入钢丝绒。当试管封闭端被加热时，活塞可能会振动。研究该现象并确定该发动机的效率。

Wikipedia Rijek管 and Sondhauss管

简单解释就是：加热使气体膨胀，往另一边冲，而后遇冷收缩，往反方向跑，又被加热，如此往复

如果没有活塞，会产生波长等于4倍试管长度的声音，很响，可以震楼