Critical Flow Venturi Nozzle Based on Mechanical Choke Principle

Abstract

The present invention discloses a critical flow venturi nozzle based on the mechanical choking principle, comprising a zooming-type venturi nozzle body consisting of the following sections connected in sequence: a head contracting section, a throat straight section, and a tail diffusion section. The inlet end of the venturi nozzle body located in the head contracting section is provided with an upstream mounting hole plate; and the outlet end of the venturi nozzle body located in the tail diffusion section is provided with an downstream mounting hole plate. The inner cavity of the venturi nozzle body is provided with a guide rod, and the central axis of the guide rod is coincident with the central axis of the venturi nozzle body. The guide rod is sleeved with a float spanning the throat straight section and used to control the fluid body flow, wherein the float is driven by the fluid body to slide along the guide rod sleeve to form a fluid channel with the throat straight section and the size of the fluid channel is variable. The nozzle of the invention can realize the critical flow of incompressible fluid with lower flow rate and smaller resistance loss, and can simultaneously shield the influence of the upstream and downstream pressure disturbances on the flow.

Description

Technical field [0001] The invention relates to the technical field of fluid control and measurement, in particular to a critical flow venturi nozzle based on the principle of mechanical choke. Background technique [0002] Critical flow is widely used in scientific research and engineering technology. Under certain inlet parameters, when the downstream pressure reaches a certain critical value, the mass flow through the throttling device will reach a maximum value. If the downstream pressure is further reduced, the flow rate will remain constant. At this time, the flow state is called Critical flow, also called choked flow. Using the flow characteristics of the critical flow, accurate flow control and measurement can be achieved. [0003] For the flow of compressible fluid in the venturi nozzle, when the downstream pressure drops to a certain critical value, the flow rate of the airflow at the throat first reaches the local speed of sound. Due to the action of the downstream dif...

AI Technical Summary

Problems solved by technology

Due to the short working time of the liquid rocket engine and the use of high hardness materials, cavitation is not a serious problem for it, but in other fields, due to such working conditions are difficult to meet, although there are good The idea has not been well applied

[0007] (2) The pressure drop and resistance loss of the cavitation Venturi nozzle are very large

For Venturi nozzles, nearly 20% of the upstream stagnation pressure will be permanently lost, which will result in a huge waste of energy

For example, in water injection wells in oil fields, the average water injection pressure is about 30MPa. If cavitation Venturi nozzles are used in distribution pipe strings, the minimum resistance loss will reach 6MPa, which is much larger than ordinary resistance parts, and it is difficult for general engineering. accepted

[0008] (3) In the case of low inlet subcooling (such as low fluid pressure at the inlet, or high fluid temperature), especially for small flow and small size cavitation Venturi nozzles, due to The fluid in the throat of the Venturi nozzle is prone to overheating, that is, there is a thermodynamic imbalance, and the phenomenon of "overflow" will occur, resulting in a flow rate greater than the theoretically calculated maximum flow rate, which affects the accuracy of flow control

For fluids with low inlet subcooling, even if the outlet pressure is lower than the critical pressure, there may still exist two states of "critical flow" and "overflow", and the flow rate cannot be uniquely determined, which causes a large flow control process. deviation

[0009] (4) Since the cavitation phenomenon is a quasi-steady state process, the pressure fluctuations caused by the generation and rupture of bubbles in the cavitation area will cause the flow rate to fluctuate accordingly, affecting the accuracy of flow control

[0010] To sum up, the incompressible fluid critical flow Venturi nozzle based on cavitation congestion has defects such as high flow velocity, large resistance loss, unstable flow control, and high requirements for material strength, so it is subject to more restrictions in application.

Images