To simplify determination of the constant C, Table 2 may also be used, which shows the constant for various Pitot tube geometric variations (for a standard round junction tube). Thus by inspection, for this tube, C = 0.997. The correct dynamic pressure and speed is then: Thus the indicated dynamic pressure will be too high. 2, the tip error is –1.4% and the stem error is +0.8%. What is the correction constant C? From Fig. Example:Ī standard round nose Pitot Static tube has static orifices located 2D from the base of the tip and 10D from the stem’s center-line. 2 to find the constant C for a given Pitot Static tube will be illustrated with an example. The upper line presents the static pressure error due to the distance of the static ports (expressed in diameters) from the stem center-line. The lower line gives the static pressure error associated with the distance of the static ports from the base of the tip, expressed in diameters. 2 Effect of static pressure hole location from Pitot Static Tube stem or tip Figure 2 shows the effect and error of the location of the static pressure tappings on the static pressure error.įig. Prandtl type Pitot tubes typically have constants C close to 1. 1) from the base of the Pitot tube’s tip and the stem’s center line. This constant is dependent on the spacing of the Pitot tubes’ static pressure ports (see Fig. If data for a particular Pitot tube is not available, the constant C may be estimated. Meter, it is necessary to select a tube with a constant close to unity, if errors in speed are to be avoided. When selecting a Pitot Static tube to be used in conjunction with a speed Speed error due to compressibility V,m/s (ft/s) High speeds (V) will lead to increasing errors as shown in Table 1. NOTE: This equation is typically valid for incompressible (constant density) flow. Where ρ is the gas density and C is a correction constant dependent on the design of the Pitot Static tube. the dynamic or speed pressure (Pdynamic) varies with the square of the gas speed.
The Pitot Static tube measures the total pressure (or impact pressure) at the nose of the Pitot tube and the static pressure of the gas stream at side ports. 1 Generic Pitot-Static Pitot Configuration
0 kommentar(er)
