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What is the principle of anemometer measuring wind speed

by:HoldPeak     2020-05-26

the definition and principle of anemometer technique of casting mold mold base plate and positioning of sand box

anemometer its basic principle is a thin metal wire in a fluid, the flow of electricity heating wire, make its temperature is higher than the temperature of the fluid, so will the wire.

anemometer is called the hotline. When the fluid flows through the wire along the vertical direction, will take away part of the metal wire heat, temperature drops make wire. Been derived according to the actual forced convection heat transfer, the hotline disappear heat Q and that there is a connection between fluid velocity v type. Two supporting tension scale hotline probe by a short, thin metal wire. Wire normally with platinum, rhodium, high melting point, good ductility, such as tungsten metal. The commonly used wire diameter of 5 & mu; M, to 2 mm long; The smallest probe diameter only 1 & mu; M, length is zero. 2毫米。 According to different purposes, hotline probe is made double wire, three wire, wire and V, X, etc. In order to increase the strength, sometimes with a metal film instead of metal wire, usually on a thermal insulating substrate coating a layer of thin metal film, called the hot film probe. Hotline sensor must be calibrated before use. Static calibration was conducted in the specialized standard wind tunnel, measuring the velocity and the relationship between the output voltage and drawing standard curve; Dynamic calibration is done in pulsating flow field known, or in the anemometer heated circuit and a pulse signal, check the frequency response of hot wire anemometer, if poor frequency response available corresponding supplement line is improved.

the velocity measurement range of 0 to 100 m/s may be divided into three sections: the low speed: 0 to 5 m/s; Medium: 5 to 40 m/s; High speed: 40 to 100 m/s. Anemometer thermal probe is used for accurate measurement of 0 to 5 m/s; Anemometer turn wheel probe measurement 5 to 40 m/s velocity results the dream; While using pitot tube can be within the scope of the high speed to get the best results. Correct decision of the anemometer velocity of the probe is an additional standard temperature, usually the thermal anemometer sensor application temperature of about + - 70C。 Special anemometer wheel probe of up to 350 c. Pitot tube is used for more than + 350 c.

mold base plate with sand box adopts a set of positioning pin and the question of a set of positioning of the positioning of the installation. In order to prevent sand box in the shape or the box when stuck death ( Namely, the set of dowel and positioning, can't go in or cannot separate) , and end with a circular positioning pin and circular set match as positioning terminal, the other end with a flat pins and locating sleeve flat suitable, direction of the length and width direction positioning direction, so often called the flat pin guide pin, flat set called guide sleeve, guide pin with a circular sometimes. Individual mechanical molding machine compete mold base plate are installed locating pin for the height of the sand box positioning pin. Cases of pin on the box the resort in box. But automatic molding line is under the sand box positioning device, and sand box installed on the positioning pin, so the modelling, the template installation positioning pin and the upper die pull positioning sleeve, some of the moulding line, a week per cycle, sand box to a head, so the sand box two positioning pin must be in the same flat pin. When circular arc surface and round set match fit role positioning. When the flat surface and set of suitable flat directional role.

because flat pins with the orientation of flat set in the width direction plays a role, so flat pins and locating sleeve flat in the manufacturing of parallelism of two flat surface and pleaded with high symmetry, the individual is 0. 025 mm, the installation at the same time request flat surface must be even with two locating hole center in parallel.

work part of the locating pin, divided into two local, positioning and orientation. Pin and set the effective length of positioning with 10 ~ 20 mm advisable. Guide portion of the slope should be less than or equal to the shape of die Angle, usually take 1-3. Guide the length of the part is divided into two kinds of situations: (1) when to crane or manual casting mould, lOmm guidance department should look higher. (2) mechanical stripping and mechanical automatic line box, because of the equipment has the accurate positioning, guiding parts greater than 30 mm.

dowel with positioning set ( Including flat pin sets of flat) For dynamic coordination, cooperate with properties of its q gap is too small affects the precision casting. However deformity mechanical model with the aid of tanks on pin type, and can be supplemented by manual adjustment, its nature of the proposal chooses H9 / d9, type and shape automatic line is active, advocate choose H8 / d8, also can choose H8 / d8.

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