The measurement of gas pressure in Jinan ventilation pipe should be carried out in the pipe section with stable air flow. The static pressure, dynamic pressure and total pressure of the gas should be measured in the test. The orifice for measuring the total pressure of the gas should face the direction of the air flow in the air duct, and the orifice for measuring the static pressure should be perpendicular to the direction of the air flow.

用U形压力计测全压和静压时，另一端应与大气相通(用倾斜微压计在正压管段测压时，管的一端应与大气相通，在负压管段测压时，容器开口端应与大气相通)。因此压力计上读出的压力，实际上是风道内气体压力与大气压力之间的压差(即气体相对压力)。大气压力一般用大气压力表测定。由于全压等于动压与静压的代数和，可只测其中两个值，另一值通过计算求得。

When U-shaped manometer is used to measure the total pressure and static pressure, the other end should be connected with the atmosphere (when inclining micro manometer is used to measure the pressure in positive pressure pipe section, one end of the pipe should be connected with the atmosphere; when measuring the pressure in negative pressure pipe section, the open end of the container should be connected with the atmosphere). Therefore, the pressure read on the pressure gauge is actually the pressure difference between the gas pressure in the air duct and the atmospheric pressure (i.e. the relative gas pressure). Atmospheric pressure is generally measured with an atmospheric pressure gauge. Since the total pressure is equal to the algebraic sum of dynamic pressure and static pressure, only two values can be measured, and the other value can be obtained by calculation.

济南通风管道

Jinan ventilation pipe

测定仪器

Measuring instrument

气体压力(静压、动压和全压)的测量通常是用插入风道中的测压管将压力信号取出，在与之连接的压力计上读出，常用的仪器有毕托管和压力计。

Gas pressure (static pressure, dynamic pressure and total pressure) is usually measured by taking out the pressure signal from the pressure measuring tube inserted into the air duct and reading it on the pressure gauge connected with it. The commonly used instruments are pitot tube and pressure gauge.

1 毕托管

1. Trusteeship

(1)标准毕托管

(1) Standard pitot

它是一个弯成90°的双层同心圆管，其开口端同内管相通，用来测定全压;在靠近管头的外壁上开有一圈小孔，用来测定静压，按标准尺寸加工的毕托管校正系数近似等于1。标准毕托管测孔很小，济南通风管道内易被粉尘堵塞，因此这种毕托管只适用于比较清洁的管道中测定。

It is a double-layer concentric tube bent into 90 ° and its open end is connected with the inner tube to measure the total pressure; a circle of small holes are opened on the outer wall near the tube head to measure the static pressure, and the pitot tube correction coefficient processed according to the standard size is approximately equal to 1. The measuring hole of standard pitot tube is very small, and it is easy to be blocked by dust in Jinan ventilation pipe. Therefore, this kind of pitot tube is only suitable for measuring in relatively clean pipe.

(2)S型毕托管

(2) S-type pitot tube

它是由两根相同的金属管并联组成，测量时有方向相反的两个开口，测定时，面向气流的开口测得的相当于全压，背向气流的开口测得的相当于静压。由于测头对气流的影响，测得的压力与实际值有较大误差，特别是静压。因此，S型毕托管在使用前须用标准毕托管进行校正，S型毕托管的动压校正系数一般在0.82～0.85之间。S型毕托管测孔较大，济南通风管道内不易被粉尘堵塞，这种毕托管在含尘污染源监测中得到广泛应用。

It is composed of two identical metal tubes in parallel. When measuring, there are two openings in opposite directions. When measuring, the opening facing the air flow is equivalent to the total pressure, and the opening facing the air flow is equivalent to the static pressure. Due to the influence of the probe on the air flow, there is a big error between the measured pressure and the actual value, especially the static pressure. Therefore, S-type pitot tube must be calibrated with standard pitot tube before use, and the dynamic pressure correction coefficient of S-type pitot tube is generally between 0.82 and 0.85. The S-type pitot tube has a large measuring hole, and it is not easy to be blocked by dust in Jinan ventilation pipeline. This kind of pitot tube is widely used in the monitoring of dust pollution sources.