before top dead center

简明释义

在上死点前在上止点前

英英释义

例句

1.The engine timing needs to be adjusted to ensure the ignition occurs just before top dead center.

发动机的时机需要调整，以确保点火发生在上死点之前。

2.To prevent knocking, the spark plug should fire before top dead center.

为了防止爆震，火花塞应在上死点之前点火。

3.The technician explained that the piston must reach its highest point before top dead center for proper compression.

技术员解释说，活塞必须在适当的压缩之前达到其最高点，即上死点之前。

4.When tuning the carburetor, make sure the fuel mixture is optimal before top dead center.

调节化油器时，确保燃油混合物在上死点之前是最佳的。

5.The manual states that the valve timing should be set before top dead center to enhance performance.

手册说明阀门时机应设置在上死点之前以提高性能。

作文

In the world of internal combustion engines, understanding the various phases of the engine cycle is crucial for both engineers and enthusiasts alike. One term that often comes up in discussions about engine timing and performance is before top dead center. This phrase refers to a specific point in the engine's cycle where the piston is close to its highest position within the cylinder, but has not yet reached it. To fully grasp the significance of this term, we must delve deeper into the mechanics of an engine and the implications of timing in relation to fuel combustion.The internal combustion engine operates on a four-stroke cycle: intake, compression, power, and exhaust. During the compression stroke, the piston moves upward in the cylinder, compressing the air-fuel mixture. It is at this point, just before the piston reaches its peak position, that the timing of the ignition becomes critical. When we refer to the moment before top dead center (即“上死点之前”), we are discussing the precise timing needed to ignite the fuel-air mixture for optimal performance.If the ignition occurs too late, after the piston has passed the top dead center, the combustion will be less efficient, leading to a loss of power and increased emissions. Conversely, if the ignition occurs too early, it can cause knocking or pinging, which can damage the engine over time. Therefore, tuning the ignition timing to occur at the right moment before top dead center (即“上死点之前”) is essential for achieving the desired performance and efficiency from the engine.Engineers often use advanced tools and techniques to measure and adjust the timing of ignition. They might utilize an oscilloscope to visualize the electrical signals from the ignition system, ensuring that the spark plug fires at the optimal moment before top dead center (即“上死点之前”). This meticulous attention to detail can have significant effects on the engine's power output, throttle response, and overall drivability.Moreover, the concept of before top dead center (即“上死点之前”) is not limited to gasoline engines alone; it is equally important in diesel engines, although the principles may differ slightly due to the nature of diesel combustion. In diesel engines, the fuel is injected into the cylinder under high pressure, and the timing of this injection relative to the piston’s position is also critical. The injection must occur at the right moment before top dead center (即“上死点之前”) to ensure complete combustion and optimal efficiency.In conclusion, the term before top dead center (即“上死点之前”) encapsulates a vital aspect of engine performance and efficiency. Understanding this concept allows engineers and mechanics to optimize engine timing, improve performance, and reduce emissions. Whether one is tuning a race car or simply trying to maintain a daily driver, paying attention to the timing related to before top dead center (即“上死点之前”) can make all the difference in achieving a well-functioning engine. As technology continues to evolve, the methods of measuring and adjusting these timings become more sophisticated, but the fundamental importance of this concept remains unchanged.