a 、 a 分别为气门开启和关闭时的曲轴转角（的翻译：A, a, namely when valve opening and closing of crankshaft rotation ( 什么意思？中文翻译英文，英文翻译中文，怎么说？

青云英语翻译

a, a valve opening and closing, respectively, when the crank angle (

A, a, namely when valve opening and closing of crankshaft rotation (

正在翻译，请等待...

A respectively, a valve opening and closing the crankshaft at corners (

A, a, namely when valve opening and closing of crankshaft rotation (