preheating time

例句：

1. 1. The oven needsto preheat for at least 30 minutes before cooking.
   烤箱在烹饪前需要至少预热30分钟。
2. 2. The machinerequires a preheating time of15 minutes before it can be used.
   这台机器在使用前需要预热15分钟。
3. 3. Before starting the project, weneed to preheat the furnace for safetyreasons.
   为了安全起见，我们在开始这个项目之前需要预热炉子。