One way to increase the efficiency of a high-bypass jet engine is to turn the fan into an open rotor, a bit like returning to propellers, but using two rings of stubby counter-rotating blades.

提高高旁通飞机引擎的方法之一就是把风扇变成开放式旋翼，有点回归于螺旋桨的味道，但要使用两圈粗短的反旋桨叶。

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There is inevitable unbalance in the dual-rotor system of the aero-engine, the beat vibration will occur to engine when two rotors are operating at approximately the same speed.

在双转子航空发动机中，由于转子系统不可避免地存在不平衡量，当两个转子的转速比较接近时，发动机会出现拍振现象，拍振将引起振动强度过大问题。

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Number 8. BELL UH-1 IROQUOIS (HUEY) is a military helicopter powered by a single turboshaft engine, with a two-bladed main rotor and tail rotor.

第八名：贝尔uh - 1 IROQUOIS(惠)是一种军用直升机搭载单涡轮轴发动机，具有双桨叶主旋翼和尾桨。

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Its Radmax engine uses two wave-shaped cams that rotate above and below a stationary rotor.

FORBES: How to get 51mpg from an engine the size of a large turkey.