secondary filter的用法和样例：
例句
- The flow field around the secondary filter was vividly characterized with a porous medium model, so that the flow pattern around this kind of filter was readily obtained.
多孔介质模型形象地描绘出了二次滤网的内部流场，获得了该型号滤网的内部流动规律。 - By replacing your air filter annually, or biannually if you live in a dusty area, you'll ensure the engine can breathe freely.
每年换一次过滤器或者在沙尘多的地方每半年更换一次能保证你的爱车引擎自由呼吸。
