March 24, 2022

The working principle and characteristics of Venturi nozzle

Venturi nozzles, also known as critical flow venturi nozzles, are mainly used in the transfer of flow standards, gas flow measurement and the limitation of the maximum flow of flow systems. Originally used by the aerospace industry, critical flow venturi nozzles are widely used in different industries such as automotive, energy and metering.

Venturi nozzle

Working principle:

The main difference between the critical flow nozzle and the critical flow venturi nozzle is that the critical flow nozzle does not have a conical diffusion section, as shown in Figure 2-1, so the pressure loss is large, about 50% of the inlet pressure. The critical flow Venturi nozzle is a flow channel with a gradually enlarged aperture behind the throat, as shown in Figure 2-2, the outlet pressure is related to the size of the diffuser section of the throat, which is about 80% of the inlet pressure. 95%, the pressure loss is small, and in the best case, only about 5% of the inlet pressure is lost. Except for the difference in pressure loss, the principle and calculation formula of the flow rate measurement are the same. Due to the large pressure loss of critical flow nozzles, critical flow Venturi nozzles are generally widely used in China.

The basic principle of the critical flow Venturi nozzle is mainly because the nozzle is a measuring tube used to measure the gas flow whose inlet aperture gradually decreases to the throat, and then gradually expands through the throat. The part with the smallest pore size is called the throat of the nozzle, and behind the throat there is a flow passage with a gradually enlarged pore size. The nozzle can obtain different critical pressure ratios with the length of its downstream expanding pipe. When the upstream stagnation pressure P0 remains unchanged, the nozzle outlet pressure P2 is gradually reduced, that is, the back pressure ratio (P2/P0) is reduced. The gas flow is first increased continuously. When the critical pressure ratio is reached, the gas reaches the critical velocity at the throat, which is equal to the local speed of sound, and the gas mass flow through the critical flow venturi nozzle of the nozzle reaches the maximum. Further reducing the back pressure ratio, the flow rate will remain the same. At this time, the Mach number is equal to 1, the flow is only related to the upstream pressure (not related to the downstream pressure), and the outflow coefficient is only related to the Reynolds number.

Physical and chemical properties:

The venturi nozzle is designed according to the principle of Berboulli’s gravitational force, and is designed with reasonable geometric surface parameters, which can form a large flow circulation and has a nozzle hole that prevents clogging. When the high-speed liquid passes through the nozzle, it drives the surrounding liquid into the spray to form a cycle. This part of the liquid is mixed with the pumped solution to increase the total amount of the circulating solution. The nozzle can produce a 4:1 flow rate ratio, so it is equipped with Small pumps with mixed flow nozzles can be used for large-capacity fluid circulation, saving energy in all aspects. . Arrangement of mixed flow nozzles: In large solution tanks, annular arrangement has higher mixing efficiency than single arrangement. The nozzles should be placed as far as possible at the bottom of the container for maximum flow rate. Choice of connection size and material: Mixed-flow nozzles are made of glass fiber-reinforced polypropylene and 316 stainless steel, with good chemical resistance and corrosion resistance, durability, and are often used for cleaning, painting and mixing. Polypropylene is available in 1/4″, 3/8″, 3/4″, 1-1/2 or male connection sizes and stainless steel is available in 3/8″, 3/4″, 1-1/2 or male Connection size. PVDF material is often used in the electroplating process to remove the negative film layer, and the electroplating solution is continuously circulated on the surface of the circuit board by the nozzles arranged in the electroplating tank to improve the electroplating effect.

Calibration of gas flow meters
Gas flow measurement
Engine flow performance calibration
Auto parts flow performance calibration
Vehicle emission system flow test
Positive displacement compressor flow performance test
Valve Flow Performance Calibration
Pipeline Fluid Flow Restriction
Protection of high-speed gas flow meters
Delivery of traffic standards

Design Features

Venturi nozzle At type solid cone nozzle can be used in various fields such as exhaust gas desulfurization, dust removal and gas cooling. Piping sizes can be as large as 4 inches.
These higher-flow nozzles effectively achieve maximum liquid flow over a given size of pipe, and the unobstructed channel design prevents clogging. At 0.07Mpa pressure, the flow rate is 333 to 2612 liters/min. These solid cone spray nozzles are available in 2-, 3-, and 4-inch piping sizes with a jet angle of 60-120°.
These nozzles feature precise influence vane angles for even spray droplet distribution for excellent coverage. The nozzle can also be customized according to the customer’s installation needs, and there are several wear-resistant materials (silicon carbide, silicon nitride, toughened ceramics, polyurethane rubber, etc.) for options.

Venturi nozzle

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