Name: fire extinguisher nozzle flow and pressure
Uploaded: 2025-02-13T15:43:18.000Z
Duration: 1 min 12 s
Channel: JoVE

灭火器利用加压水通过喷嘴产生一股强大的水流。
内部的水被储存在远高于周围大气压的压力下，因此当灭火器启动时，水会被迫流出。
应用流体动力学方程来确定水从喷嘴射出的速度以及随时间排出的水量。
第一步是了解灭火器内部与喷嘴外部之间的压力差。
这种压力差驱动水的流动。通过应用伯努利方程（该方程描述了压力与流速之间的关系），可计算出水流从喷嘴射出时的速度。
较小的喷嘴直径会使水流在流出时加速，将压力转化为流速。
计算出射流速度后，即可确定流量。流量通过连续性方程计算，该方程确保流经喷嘴的水量保持恒定。
通过将水的流速乘以喷嘴的横截面积来计算流量。

设计示例：通过灭火器的流动

Design Example: Flow Through a Fire Extinguisher

使用加压水的灭火器依靠流体动力学原理产生能够抑制火焰的高速水流。灭火器内部的水压比周围大气高得多。这种压力差迫使水在灭火器启动时快速流动，可以使用流体动力学的基本方程来理解水流出喷嘴时的行为。 理解水如何加速的关键在于灭火器内部和外部环境之间的压力差。伯努利方程联系了压力和速度之间的关系，可计算水流出喷嘴的速度。 <img alt="Equation 1" src="/files/ftp_upload/18047/18047_Equation_1.svg" style="text-align: center; height: 45px;"> 根据这一原理，压力降低，速度增加。这意味着灭火器内部的高压转化为水流出的速度。当水接近喷嘴时，喷嘴直径的减小进一步加速了流动，将压力能转化为动能。 确定水的出口速度后，计算出流量，即随时间排出的水量。计算使用连续性方程，确保流经系统的水量保持不变。流量是水的速度与喷嘴横截面积的乘积。 <img alt="Equation 2" src="/files/ftp_upload/18047/18047_Equation_2.svg" style="text-align: center; height: 40px;"> 由于喷嘴直径较小，因此水的速度很快，提供灭火所需的稳定而强劲的水流。通过应用这些原理，可以优化灭火器的性能，确保有效运行。

灭火器利用加压水通过喷嘴产生一股强大的水流。  
内部的水被储存在远高于……的压力下。

design-example-flow-through-a-fire-extinguisher

Education

教育

JoVE Core

Civil Engineering

土木工程

Unit 1

第一单元

Fluid Kinematics

流体运动学

KEY TERMS AND CONCEPTS

关键术语与概念

fire extinguisher nozzle flow and pressure

A pressurized water fire extinguisher uses fluid dynamics to create a fast stream of water. The water is stored at a much higher pressure inside the extinguisher than the surrounding air. When the extinguisher is activated, that pressure difference forces water to flow out quickly.

Bernoulli's equation helps predict the exit speed of the water. This equation links pressure and velocity. As pressure drops, velocity increases. In the extinguisher, the high internal pressure is converted into the water's speed as it leaves the nozzle.

The nozzle also plays an important role because its diameter becomes smaller near the exit. A smaller opening increases the flow speed even more. This turns pressure energy into kinetic energy, which is the energy of motion.

After the exit velocity is found, the flow rate can be calculated. Flow rate is the volume of water expelled each second. The continuity equation is used to keep track of how much water moves through the system, and the flow rate equals the water speed times the nozzle's cross-sectional area. Because the nozzle is small, the water comes out at high velocity and forms a strong, steady stream for fire suppression.

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design example: flow through a fire extinguisher

A pressurized water fire extinguisher uses fluid dynamics to create a fast stream of water. The water is stored at a much higher pressure inside the extinguisher than the surrounding air. When the extinguisher is activated, that pressure difference forces water to flow out quickly. Bernoulli's equation helps predict the exit speed of the water. This equation links pressure and velocity. As pressure drops, velocity increases. In the extinguisher, the high internal pressure is converted into the...

key terms and concepts

Explore how pressure, Bernoulli's equation, and nozzle size control the water speed and flow rate in a pressurized fire extinguisher.

Fire Extinguisher Nozzle Flow and Pressure | JoVE K12

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Fire Extinguisher Nozzle Flow and Pressure

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