发动机原理及详解之二

?A rotary engine is an internal combustion engine, but it works in a completely different way than the conventional piston engine.

In a piston engine, the same volume of space (the cylinder) alternately does four different jobs -- intake, compression, combustion and exhaust. A rotary engine does these same four jobs, but each one happens in its own part of the housing. It's kind of like having a dedicated cylinder for each of the four jobs, with the piston moving continually from one to the next.

As the rotor moves through the housing, the three chambers created by the rotor change size. This size change produces a pumping action. Let's go through each of the four strokes of the engine looking at one face of the rotor.

Intake

The intake phase of the cycle starts when the tip of the rotor passes the intake port. At the moment when the intake port is exposed to the chamber, the volume of that chamber is close to its minimum. As the rotor moves past the intake port, the volume of the chamber expands, drawing air/fuel mixture into the chamber.

When the peak of the rotor passes the intake port, that chamber is sealed off and compression begins.

Compression

As the rotor continues its motion around the housing, the volume of the chamber gets smaller and the air/fuel mixture gets compressed. By the time the face of the rotor has made it around to the spark plugs, the volume of the chamber is again close to its minimum. This is when combustion starts.

Combustion

Most rotary engines have two spark plugs. The combustion chamber is long, so the flame would spread too slowly if there were only one plug. When the spark plugs ignite the air/fuel mixture, pressure quickly builds, forcing the rotor to move.

The pressure of combustion forces the rotor to move in the direction that makes the chamber grow in volume. The combustion gases continue to expand, moving the rotor and creating power, until the peak of the rotor passes the exhaust port.

Exhaust

Once the peak of the rotor passes the exhaust port, the high-pressure combustion gases are free to flow out the exhaust. As the rotor continues to move, the chamber starts to contract, forcing the remaining exhaust out of the port. By the time the volume of the chamber is nearing its minimum, the peak of the rotor passes the intake port and the whole cycle starts again.

The neat thing about the rotary engine is that each of the three faces of the rotor is always working on one part of the cycle -- in one complete revolution of the rotor, there will be three combustion strokes. But remember, the output shaft spins three times for every complete revolution of the rotor, which means that there is one combustion stroke for each revolution of the output shaft.

【中文注解】

旋转式发动机是一种内燃型发动机，但是它与传统的活塞式发动机完全不同。

对于活塞式发动机来说，它的气缸内部空间本身承担着四个不同的工作——进气、压缩、燃烧与排气。不过旋转式发动机也有这四大工作，但是这些工作是在发动机内不同的空间内进行的。

旋转式发动机的转子在气缸室内转动时，转子与缸壁之间开成的气室的大小可以随着转子转动改变。气室的大小转变可以产生泵吸作用。

进气

当转子的边缘经过进气口始，整个做功循环的吸气环节就开始了。此时，进气口与气缸内室连通，此时这个气室的容积最小，当转子转过进气口时，气室的体积开始扩大，吸入空气燃汽混和气。当转子的最顶点转过进气口时，这个气室开始封闭，并进入压缩状态。

压缩

转子继续在气缸内运动，该气室的体积变小，里面的混和气体开始进行压缩，当转子的面快转到火花塞时，气室的体积再次接近最小值，这时燃烧环节就要开始。

燃烧

大部分旋转式发动机都有两个火花塞。如果只有一个火花塞，而燃烧室比较狭长，燃烧就会会延缓进行。事实上，火花塞一旦引燃混和气体，燃烧室内压力迅速加大，迫使转子转动。

气室内压力增大，迫使转子向使气室里体积增大的方面转动。燃烧的气体继续增大，使得转子移动，并生产能量。直到转子的顶点经过排气口。

排气

当转子顶端通过排气口时，高压的燃气会从排气口排出。气室的体积继续减小，迫使剩余的气体排出气室。当气室的体积达到最小时，转子的顶点经过进气口，整个循环重新开始了。

【延伸阅读】

* 汽车的心脏——发动机

* 发动机原理及详解之一

* 发动机原理及详解之二

* 发动机原理及详解之三

* 发动机原理及详解之四
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