The engines used by Ark Angel are electric motors driving counter-rotating propellers, mounted in pods below the hull.

方舟天使使用的引擎是反向旋转的螺旋桨驱动的电动马达，安装在船体下的分离舱中。

youdao

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。

youdao

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.

ECONOMIST: A new way to build a greener jet engine