CN107479585B - Critical flow venturi nozzle based on mechanical choking principle - Google Patents
Critical flow venturi nozzle based on mechanical choking principle Download PDFInfo
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Abstract
The invention discloses a critical flow venturi nozzle based on a mechanical choking principle, which comprises a convergent-divergent venturi nozzle body, wherein the venturi nozzle body consists of a head contraction section, a throat straight pipe section and a tail diffusion section which are sequentially connected; an upstream mounting pore plate is arranged at the inlet end of the venturi nozzle body positioned at the head contraction section, and a downstream mounting pore plate is arranged at the outlet end of the venturi nozzle body positioned at the tail diffusion section; a guide rod penetrates through the inner cavity of the Venturi nozzle body, and the central axis of the guide rod is superposed with the central axis of the Venturi nozzle body; the guide rod is sleeved with a floater which crosses over the straight throat pipe section and is used for controlling the flow of fluid, and the floater can axially slide along the guide rod under the driving of the fluid to form a flow passage with a variable area with the straight throat pipe section. The invention can realize the critical flow of the incompressible fluid under the conditions of lower flow speed and smaller resistance loss, and can simultaneously shield the influence of upstream and downstream pressure disturbance on the flow.
Description
Technical Field
The invention relates to the technical field of fluid control and measurement, in particular to a critical flow venturi nozzle based on a mechanical choking principle.
Background
Critical flows are widely used in scientific research and engineering. At a certain inlet parameter, when the downstream pressure reaches a certain critical value, the mass flow through the restriction will reach a maximum value, and if the downstream pressure is further reduced, the flow will remain constant, with the flow regime being called critical flow, also called choked flow. By using the flow characteristics of the critical flow, precise control and measurement of the flow rate can be achieved.
For the flow of compressible fluid in the Venturi nozzle, when the downstream pressure is reduced to a certain critical value, the flow velocity of airflow at the throat part reaches the local sound velocity first, and due to the action of the downstream diffusion section of the throat part, the fluid is decelerated and pressurized in the diffusion section until the outlet section is balanced with the back pressure of the external environment. At which point the flow reaches a maximum, critical flow. If the pressure in the downstream is reduced continuously, shock waves are formed on a certain section in the downstream of the throat, although the shock waves are thin in thickness, the resistance is large, the shock wave front can be regarded as a barrier layer with a dense gas composition, an extra 'additional resistance' is generated when the gas flows through, a large amount of kinetic energy is consumed, and the 'additional resistance' can automatically adjust the value and maintain the critical flow constant. For example, when the downstream pressure is reduced, the pressure difference between the inlet and the outlet is increased, and the flow rate tends to be increased, but at this time, the shock wave moves downstream, the shock wave strength is increased, and at this time, the thickness of the shock wave becomes thinner, but the shock wave is denser, so that the "wave resistance" is increased, that is, the additional resistance is increased, the reduction of the downstream pressure is compensated, the increase of the flow rate is prevented, and the flow rate is maintained unchanged. Similarly, when the downstream pressure rises, the pressure difference between the inlet and the outlet is reduced, the flow rate tends to be reduced, at the moment, the shock wave moves to the position which is more upstream, the mach number of the incoming flow in front of the shock wave front is reduced, the shock wave intensity is reduced, the thickness of the shock wave becomes thicker and relatively sparse, the additional resistance when the fluid flows through is reduced, the flow rate is prevented from being reduced, and the constant flow rate is kept.
For incompressible fluid flowing in a venturi nozzle, when the downstream pressure drops to a certain threshold, the fluid will begin to vaporize at the throat or a portion of the fluid further downstream from the throat as the pressure reaches a saturated vapor pressure. When vaporization occurs, a rapid local phase change from liquid to gas will occur near the throat, and although the mass fraction of the vapor is small, its volume is very large, resulting in a sudden increase in flow resistance. The cavitation zone is thus a "cavitation barrier" consisting of bubbles of high resistance, creating an additional resistance to the passage of fluid. If the downstream pressure is further reduced, the flow rate tends to be increased, but the cavitation intensity is increased at the moment, so that the cavitation barrier layer expands and elongates, the additional resistance of the fluid flowing through the cavitation barrier layer is increased, the influence of the downstream pressure reduction on the flow rate is compensated, the fluid is balanced with the back pressure of the external environment when flowing to the outlet section, and the flow rate is kept constant. Similarly, if the downstream pressure increases, the cavitation intensity decreases, resulting in a decrease in the contraction of the cavitation barrier, reducing the additional resistance of the fluid flowing through the area, preventing a decrease in flow, and maintaining a constant flow.
However, the critical flow venturi nozzle structure based on cavitation choking is mainly applied to liquid fuel rocket engines, and is less applied to other engineering fields. The main problems limiting its wide application are the following:
(1) like other cavitation phenomena, when cavitation occurs inside the venturi tube, a gas core in liquid can rapidly expand to form obvious visible bubbles in a low-pressure area, the bubbles can collapse when flowing through the high-pressure area to release energy, a high-energy density state is achieved in a short time and a small volume, a local relatively high-temperature high-pressure area is formed, strong shock waves and high-speed micro-jet flows can be generated, a strong erosion effect can be generated on most fluid equipment or the tube wall, and meanwhile, huge noise and strong vibration can be accompanied, and potential safety hazards are caused. This places severe requirements on the device materials and operating conditions. Since the operating time of the liquid rocket engine is short and the material with high hardness is adopted, the cavitation is not a serious problem for the liquid rocket engine, but in other fields, the operating conditions are difficult to meet, and although good assumption is made, the liquid rocket engine cannot be well applied.
(2) The pressure drop and drag losses of a cavitation venturi nozzle are very large. For example, the saturation vapor pressure of water at 25 ℃ is only 3.17kPa, which is almost negligible compared to the inlet pressure, meaning that the upstream static pressure energy is converted into kinetic energy at the throat to reach the critical flow state. For a venturi nozzle, pressures approaching 20% of the upstream stagnation pressure will be permanently lost, which will result in a significant waste of energy. For example, in an oil field water injection well, the average water injection pressure is about 30MPa, if a cavitation Venturi nozzle is adopted in a distribution pipe column, the lowest resistance loss reaches 6MPa, and the loss is far greater than that of a common resistance part, so that the average water injection pressure is unacceptable in common engineering.
(3) Under the condition of low inlet supercooling degree (such as the condition that the fluid pressure at the inlet is low or the fluid temperature is high), especially for a small-flow and small-size cavitation Venturi nozzle, as the fluid is easily overheated at the throat part of the Venturi nozzle, namely thermodynamic imbalance exists, an overflowing phenomenon can occur, the flow is larger than the maximum flow calculated theoretically, and the flow control precision is influenced. For a fluid with low inlet subcooling, even if the outlet pressure is lower than the critical pressure, two states of critical flow and overflowing can still exist, and the flow rate cannot be determined uniquely, so that a large deviation occurs in the flow control process.
(4) Since cavitation is a quasi-steady state process, the pressure fluctuation caused by the generation and the rupture of bubbles in the cavitation area can cause the flow to fluctuate along with the cavitation, and the flow control precision is influenced. At the same time, the flow rate fluctuates with changes in the morphology of the cavitation zone, since the bubbles collapse requiring surrounding liquid to fill the cavity. Research results show that the flow control errors of the cavitation Venturi nozzle in a choked state are about 10 percent and even higher.
In summary, the incompressible fluid critical flow venturi nozzle based on cavitation choking has the defects of high flow velocity, large resistance loss, unstable flow control, high requirement on material strength and the like, and is limited in application.
Disclosure of Invention
The invention aims to overcome the defects of the background technology, and provides a critical flow venturi nozzle based on the mechanical choking principle, which can realize the critical flow of incompressible fluid under the conditions of low flow speed and small resistance loss, and can simultaneously shield the influence of upstream and downstream pressure disturbance on the flow.
In order to achieve the aim, the critical flow venturi nozzle based on the mechanical choking principle comprises a convergent-divergent venturi nozzle body, wherein the venturi nozzle body consists of a head contraction section, a throat straight pipe section and a tail diffusion section which are sequentially connected; an upstream mounting pore plate is arranged at the inlet end of the venturi nozzle body positioned at the head contraction section, and a downstream mounting pore plate is arranged at the outlet end of the venturi nozzle body positioned at the tail diffusion section; a guide rod penetrates through the inner cavity of the Venturi nozzle body, and the central axis of the guide rod is superposed with the central axis of the Venturi nozzle body; one end of the guide rod is in threaded connection with a central hole of the upstream mounting pore plate, and the other end of the guide rod is in threaded connection with a central hole of the downstream mounting pore plate;
the guide rod is sleeved with a floater which crosses over the straight pipe section of the throat and is used for controlling the flow of fluid, and two ends of the floater respectively extend towards the upstream mounting pore plate and the downstream mounting pore plate to form a streamline structure; the end, facing the upstream mounting pore plate, of the floater is a free end, the end, facing the downstream mounting pore plate, of the floater is connected with the downstream mounting pore plate through a spring sleeved on the guide rod, and the floater can axially slide along the guide rod under the driving of fluid to form a flow passage with a variable area with the straight pipe section of the throat.
In the technical scheme, the upstream mounting orifice plate and the downstream mounting orifice plate have the same structure, and the upstream mounting orifice plate comprises an outer ring, an inner ring which is arranged in the middle of the outer ring and provided with a central hole, and a support rod which is arranged between the inner wall of the outer ring and the outer wall of the inner ring; the number of the supporting rods is three, the supporting rods are evenly arranged along the circumferential direction of the inner wall of the outer ring at intervals, and a fan-shaped channel for liquid circulation is reserved between every two adjacent supporting rods. The both ends of guide arm all are provided with the external screw thread, the centre bore inner wall of inner ring is provided with the internal thread with external screw thread assorted.
Among the above-mentioned technical scheme, the float comprises float initial segment, effective control section and the float tail section that the order is connected, the float initial segment is arranged towards upstream installation orifice plate, the float tail section is arranged towards downstream installation orifice plate, the central axis of float and the central axis coincidence of venturi spray tube body.
In the above technical solution, the shape line equation of the profile generatrix of the effective control section of the float along the axial direction thereof is determined by the following formula:
in the formula, x and y are respectively an abscissa and an ordinate corresponding to any point on the shape bus, Q is critical mass flow, theta is a choking characteristic coefficient, R is the radius of the straight pipe section of the throat part, rho is fluid density, k is the elastic coefficient of the spring, b is the precompression amount of the spring, R is the radius of the guide rod, and L is the length of the effective control section.
In the above technical solution, the congestion characteristic coefficient θ is related to a structural parameter and a flow parameter, and a CFD numerical simulation method is adopted to determine the congestion characteristic coefficient θ in a specific expression form θ (x), and the specific steps are as follows:
1) let θ be 1;
2) calculating the shape line equation y ═ f (x) of the floater according to the value theta in the step 1);
3) determining the structure of the floater according to the shape line equation obtained in the step 2), establishing a corresponding numerical calculation model of the critical flow Venturi nozzle based on the mechanical choking principle, and then obtaining corresponding flow Q flowing through the nozzle under different inlet and outlet pressure differences by using Fluent softwarenum；
4) If it is not
Calculating the theta value of the floater under different displacements by using the numerical simulation result in the step 3), fitting a new expression form theta (x) of the choking characteristic coefficient theta, replacing the theta value in the step 1) with the new expression, and repeating the step 2) and the step 3);
5) when in use
When the iteration program is ended, the obtained float shape line equation y ═ f (x) meets the designed critical flow requirement.
In the above technical solution, the length L of the effective control section is according to the maximum allowable working pressure difference Δ PmaxIs determined by the following formula,
in the formula: r is the radius of the straight pipe section of the throat, R is the radius of the guide rod, Q is the critical mass flow, theta is the choking characteristic coefficient, rho is the fluid density, k is the elastic coefficient of the spring, and delta PmaxThe maximum pressure difference between the inlet and the outlet when cavitation does not occur in the Venturi nozzle body.
In the above technical solution, the maximum stroke of the float is less than or equal to L.
Compared with the prior art, the invention has the following advantages:
the invention utilizes a mechanical component consisting of a spring and a floater arranged at the orifice of the Venturi tube as a 'choking body', the 'choking body' forms an 'additional resistance piece' similar to a 'shock wave resistance' or an 'air pocket barrier layer', an additional resistance is formed for the flow of fluid, and the mechanical component can automatically generate mechanical movement along with the change of downstream pressure to adjust the size of the additional resistance, accurately block the influence of the downstream parameter fluctuation on the flow, and finally keep the flow constant. The novel critical flow venturi nozzle structure based on mechanical choking neither requires the flow velocity to reach the sonic velocity, nor needs liquid to reduce the pressure to generate cavitation, namely, the fluid realizes the function of critical flow under the working condition of subcritical flow, thereby having the characteristics of low flow velocity, small resistance loss, no noise and no vibration, and being an effective and practical method for solving the problem of the critical flow of incompressible fluid.
Detailed Description
Fig. 1 is a schematic structural diagram of a critical flow venturi nozzle based on the mechanical choking principle of the present invention.
Fig. 2 is a schematic view of the structure of the float of fig. 1.
FIG. 3 is a schematic cross-sectional view of the upstream mounting orifice plate of FIG. 1.
FIG. 4 is a schematic side view of the upstream mounting orifice plate of FIG. 1.
Fig. 5 is a schematic diagram of an optimized flow of the effective control segment line of the floater.
In the figure: 1-venturi nozzle body, 1.1-head contraction section, 1.2-throat straight pipe section, 1.3-tail diffusion section, 2-upstream installation pore plate, 2.1-outer ring, 2.2-inner ring, 2.3-strut, 3-downstream installation pore plate, 4-guide rod, 5-floater, 5.1-floater first section, 5.2-effective control section, 5.3-floater tail section and 6-spring.
Detailed Description
The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. While the advantages of the invention will be apparent and readily appreciated by the description.
The critical flow venturi nozzle based on the mechanical choking principle as shown in fig. 1 comprises a convergent-divergent venturi nozzle body 1, wherein the venturi nozzle body 1 consists of a head contraction section 1.1, a throat straight pipe section 1.2 and a tail diffusion section 1.3 which are sequentially connected; an upstream mounting pore plate 2 is arranged at the inlet end of the venturi nozzle body 1 positioned at the head contraction section 1.1, and a downstream mounting pore plate 3 is arranged at the outlet end of the venturi nozzle body 1 positioned at the tail diffusion section 1.3; a guide rod 4 penetrates through the inner cavity of the Venturi nozzle body 1, and the central axis of the guide rod 4 is superposed with the central axis of the Venturi nozzle body 1; one end of the guide rod 4 is in threaded connection with a central hole of the upstream mounting pore plate 2, and the other end of the guide rod 4 is in threaded connection with a central hole of the downstream mounting pore plate 3;
the guide rod 4 is sleeved with a floater 5 which crosses the throat straight pipe section 1.2 and is used for controlling fluid flow, two ends of the floater 5 respectively extend towards the upstream mounting pore plate 2 and the downstream mounting pore plate 3 to form a streamline structure, and the central axis of the floater 5 is superposed with the central axis of the guide rod 4. The end, facing the upstream mounting pore plate 2, of the floater 5 is a free end, the end, facing the downstream mounting pore plate 3, of the floater 5 is connected with the downstream mounting pore plate 3 through a spring 6 sleeved on the guide rod 4, and the floater 5 can axially slide along the guide rod 4 under the driving of fluid to form a flow passage with a variable area with the throat straight pipe section 1.2. When the float 5 is in the initial position, the spring 6 has a certain pre-compression, so that the spring 6 is always kept in compression. The floater 5 with a special shape line crosses the straight throat pipe section 1.2 of the Venturi nozzle body 1 and forms an annular flow passage with variable area with the straight throat pipe section 1.2 of the Venturi nozzle body 1. The minimum flow cross section of the critical flow venturi nozzle based on the mechanical choking principle is equal to the lateral area of the truncated cone ABCD, the size of which varies with the movement of the float 5. The displacement of the float 5 is determined according to the interaction of both the driving force of the fluid and the elastic force of the spring 6.
As shown in fig. 2, the float 5 consists of a float head section 5.1, an active control section 5.2 and a float tail section 5.3 which are connected in series, and the geometry of the float is designed according to the principle of fluid mechanics, so that the flow separation and the resistance to the fluid are reduced as much as possible. The float head section 5.1 is arranged towards the upstream mounting orifice plate 2, and the float tail section 5.3 is arranged towards the downstream mounting orifice plate 3. The first section 5.1 of the floater can reduce resistance loss and improve the motion stability of the floater 5, and the tail section 5.3 of the floater can also improve the motion stability of the floater.
In the above technical solution, the shape line equation of the outer shape generatrix 5.21 of the effective control section 5.2 of the float 5 along the axial direction thereof is determined by the following formula:
in the formula, x and y are respectively an abscissa and an ordinate corresponding to any point on an outline bus, Q is critical mass flow, theta is a choking characteristic coefficient, R is the radius of a straight pipe section 1.2 of a throat part, rho is fluid density, k is the elastic coefficient of a spring 6, b is the precompression amount of the spring 6, R is the radius of a guide rod 4, and L is the length of an effective control section 5.2.
In the above technical solution, the choke characteristic coefficient θ reflects the influence of the flow coefficient and the pressure distribution inside the device on the float structure, the choke characteristic coefficient θ is related to the structural parameter and the flow parameter, the specific expression form θ (x) thereof needs to be determined by an experiment or a CFD numerical simulation method, the CFD numerical simulation method is used to determine the choke characteristic coefficient θ, and the specific steps are as follows:
1) let θ be 1;
2) calculating the shape line equation y ═ f (x) of the floater according to the value theta in the step 1);
3) determining the structure of the floater according to the shape line equation obtained in the step 2), establishing a corresponding numerical calculation model of the critical flow Venturi nozzle based on the mechanical choking principle, and then obtaining corresponding flow Q flowing through the nozzle under different inlet and outlet pressure differences by using Fluent softwarenum；
4) If it is not
Calculating the theta value of the floater under different displacements by using the numerical simulation result in the step 3), fitting a new expression form theta (x) of the choking characteristic coefficient theta, replacing the theta value in the step 1) with the new expression, and repeating the step 2) and the step 3);
5) when in use
When the iteration program is ended, the obtained float shape line equation y ═ f (x) meets the designed critical flow requirement.
In the above solution, the length L of the active control segment 5.2 is determined according to the maximum allowable working pressure difference Δ PmaxIs determined by the following formula,
in the formula: r is the radius of the straight pipe section 1.2 of the throat, R is the radius of the guide rod 4, Q is the critical mass flow, theta is the choking characteristic coefficient, rho is the fluid density, k is the elastic coefficient of the spring 6, and delta PmaxThe maximum travel of the float 5 is less than or equal to L, which is the maximum pressure differential between the inlet and outlet when cavitation does not occur within the venturi nozzle body 1.
As shown in fig. 3 and 4, the upstream mounting orifice plate 2 and the downstream mounting orifice plate 3 have the same structure, and the upstream mounting orifice plate 2 comprises an outer ring 2.1, an inner ring 2.2 with a central hole arranged in the middle of the outer ring 2.1, and struts 2.3 arranged between the inner wall of the outer ring 2.1 and the outer wall of the inner ring 2.2; the number of the supporting rods 2.3 is three, the supporting rods are evenly arranged along the circumferential direction of the inner wall of the outer ring 2.1 at intervals, and a fan-shaped channel for liquid circulation is reserved between every two adjacent supporting rods 2.3. Both ends of the guide rod 4 are provided with external threads, and the inner wall of the central hole of the inner ring 2.2 is provided with internal threads matched with the external threads. The upstream mounting orifice plate 2 and the downstream mounting orifice plate 3 can keep the float at the central position of the flow passage, the mounting position of the upstream mounting orifice plate 2 ensures that the interface of the effective control section 22 and the float tail section 5.3 is superposed with the upstream end surface of the venturi nozzle throat straight pipe section 1.2 when the float is at the initial position, and the relative position between the downstream mounting orifice plate 3 and the guide rod is adjusted, so that the precompression amount of the spring 6 can be adjusted.
The working principle of the critical flow venturi nozzle based on the mechanical choking principle is as follows: the float is a body of revolution with a smooth surface, the active control section of which approximates a cone and gradually decreases in diameter from upstream to downstream. Thus, the spring-float choking body is added in the Venturi nozzle body to form an additional throttling element similar to an air pocket blocking layer in the traditional cavitation Venturi nozzle, and the additional throttling element can automatically extend and contract along with the fluctuation of downstream pressure to maintain the critical flow state. When the downstream pressure is reduced, the pressure difference at the two ends of the floater is increased, the compression spring moves downstream, the area of an annular flow passage formed by the floater and the throat part of the Venturi nozzle is reduced, and the throttling degree is increased, so that the additional resistance is increased, the flow is prevented from being increased, and the flow is kept constant. On the contrary, when the downstream pressure rises, the pressure difference at the two ends of the floater is reduced, the spring stretches, the area of the annular channel is increased, the throttling degree of the fluid is reduced, the additional resistance is reduced, and the flow is maintained unchanged. Therefore, the 'additional throttling element' formed by the spring-floater 'choking body' can effectively block the influence of downstream pressure disturbance on the flow and realize the critical flow. In addition, the critical flow device formed based on mechanical action can block the influence of upstream pressure disturbance on the flow. For example, when the upstream pressure increases, the pressure difference between the two ends of the float increases, and the spring is driven to move downwards together, so that the flow area is reduced, the throttling degree is increased, the additional resistance is increased, and the flow is maintained unchanged. Also when the upstream pressure decreases, the float moves upstream, reducing the additional resistance, preventing the flow from increasing, maintaining the flow constant.
According to the previous analysis, the critical flow of compressible fluid or incompressible fluid is realized by means of automatic adjustment of an additional resistance formed by the fluid during the flow process to counteract the influence of the pressure difference change on the flow. The compressible fluid is automatically regulated by additional resistance formed by 'shock wave resistance' to balance the change of downstream back pressure and maintain critical flow; the incompressible fluid depends on the 'expansion deformation' of the 'cavitation barrier layer' formed by the bubbles, and the magnitude of the additional resistance when the fluid flows through is changed, so that the influence of the downstream pressure change on the flow is counteracted, and the critical flow is realized. Although the "shock wave drag" or "cavitation barrier" behavior is extremely complex, the net effect is to create an additional drag that can be automatically adjusted, just like an "additional drag" installed in the pipeline, to adjust and control the flow rate variations. It is inspired by the above that the spring-floater choking body of the invention is adopted to replace or simulate the action of additional resistance to fluid generated by the shock wave resistance or the cavitation barrier layer, so that the critical flow can be realized under the easier condition, partial defects of the cavitation Venturi nozzle can be overcome, and the application range of the incompressible fluid critical flow device is enlarged.
Details not described in this specification are within the skill of the art that are well known to those skilled in the art.
Claims (4)
1. The utility model provides a critical flow venturi nozzle based on machinery chokes principle, includes the venturi nozzle body (1) of pantographic formula, venturi nozzle body (1) comprises head convergent section (1.1), throat straight tube section (1.2) and afterbody divergent section (1.3) that connect gradually, its characterized in that:
an upstream mounting pore plate (2) is arranged at the inlet end of the venturi nozzle body (1) positioned at the head contraction section (1.1), and a downstream mounting pore plate (3) is arranged at the outlet end of the venturi nozzle body (1) positioned at the tail diffusion section (1.3); a guide rod (4) penetrates through the inner cavity of the Venturi nozzle body (1), and the central axis of the guide rod (4) is superposed with the central axis of the Venturi nozzle body (1); one end of the guide rod (4) is in threaded connection with a central hole of the upstream mounting pore plate (2), and the other end of the guide rod (4) is in threaded connection with a central hole of the downstream mounting pore plate (3);
a floater (5) crossing the throat straight pipe section (1.2) and used for controlling the fluid flow is sleeved on the guide rod (4), and two ends of the floater (5) respectively extend towards the upstream installation pore plate (2) and the downstream installation pore plate (3) to form a streamline structure; one end of the floater (5) facing the upstream installation pore plate (2) is a free end, one end of the floater (5) facing the downstream installation pore plate (3) is connected with the downstream installation pore plate (3) through a spring (6) sleeved on the guide rod (4), and the floater (5) can axially slide along the guide rod (4) under the driving of fluid to form a flow passage with variable area with the throat straight pipe section (1.2);
the floater (5) consists of a floater first section (5.1), an effective control section (5.2) and a floater tail section (5.3) which are sequentially connected, wherein the floater first section (5.1) is arranged towards an upstream installation pore plate (2), the floater tail section (5.3) is arranged towards a downstream installation pore plate (3), and the central axis of the floater (5) is coincided with the central axis of the Venturi nozzle body (1);
the shape line equation of the contour generatrix of the effective control section (5.2) of the float (5) in its axial direction is determined by the following equation:
in the formula, x and y are respectively an abscissa and an ordinate corresponding to any point on an outline bus, Q is critical mass flow, theta is a choking characteristic coefficient, R is the radius of a straight pipe section (1.2) of a throat part, rho is fluid density, k is the elastic coefficient of a spring (6), b is the precompression amount of the spring (6), R is the radius of a guide rod (4), and L is the length of an effective control section (5.2);
the method is characterized in that the congestion characteristic coefficient theta is related to structural parameters and flow parameters, the specific expression form theta is theta (x), and the congestion characteristic coefficient theta is determined by adopting a CFD numerical simulation method, and the method comprises the following specific steps:
1) let θ be 1;
2) calculating the shape line equation y ═ f (x) of the floater according to the value theta in the step 1);
3) determining the structure of the floater according to the shape line equation obtained in the step 2), establishing a corresponding numerical calculation model of the critical flow Venturi nozzle based on the mechanical choking principle, and then obtaining corresponding flow Q flowing through the nozzle under different inlet and outlet pressure differences by using Fluent softwarenum；
4) If it is not
Calculating the theta value of the floater under different displacements by using the numerical simulation result in the step 3), fitting a new expression form theta (x) of the choking characteristic coefficient theta, replacing the theta value in the step 1) with the new expression, and repeating the step 2) and the step 3);
5) when in use
When the iteration program is ended, the obtained float-shaped line equation y ═ f (x) meets the designed critical flow requirement;
the length L of the active control section (5.2) is dependent on the maximum permissible operating pressure difference Δ PmaxIs determined by the following formula:
in the formula: r is the radius of the straight pipe section (1.2) of the throat, R is the radius of the guide rod (4), Q is the critical mass flow, theta is the choking characteristic coefficient, rho is the fluid density, k is the elastic coefficient of the spring (6), and delta PmaxIs the maximum pressure difference between the inlet and the outlet when cavitation does not occur in the Venturi nozzle body (1).
2. The critical flow venturi nozzle based on the mechanical choking principle of claim 1, wherein: the upstream mounting pore plate (2) and the downstream mounting pore plate (3) have the same structure, and the upstream mounting pore plate (2) comprises an outer ring (2.1), an inner ring (2.2) which is arranged in the middle of the outer ring (2.1) and is provided with a central hole, and a support rod (2.3) which is arranged between the inner wall of the outer ring (2.1) and the outer wall of the inner ring (2.2); the number of the supporting rods (2.3) is three, the supporting rods are evenly arranged along the circumferential direction of the inner wall of the outer ring (2.1) at intervals, and a fan-shaped channel for liquid circulation is reserved between every two adjacent supporting rods (2.3).
3. The critical flow venturi nozzle based on the mechanical choking principle of claim 2, wherein: the two ends of the guide rod (4) are provided with external threads, and the inner wall of the center hole of the inner ring (2.2) is provided with internal threads matched with the external threads.
4. The critical flow venturi nozzle based on the mechanical choking principle according to claim 1, characterized in that the maximum travel of the float (5) is less than or equal to L.
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| CN113741557A (en) * | 2020-05-27 | 2021-12-03 | 中国石油化工股份有限公司 | Method and device for controlling critical flow of ground wet steam |
| CN114427409B (en) * | 2020-09-09 | 2024-07-19 | 中国石油化工股份有限公司 | Adjustable steam critical flow Venturi nozzle and critical flow regulating and controlling method |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4139581A (en) * | 1976-09-16 | 1979-02-13 | Swanson Wilbur M | Carburetor |
| JPH0875621A (en) * | 1994-08-31 | 1996-03-22 | Tsukasa Sotsuken:Kk | Constant flow rate sampling apparatus using variable cross section critical flow venturi tube using movable venturi tube |
| DE69521643D1 (en) * | 1994-04-30 | 2001-08-16 | Horiba Ltd | Changeable venturi section for critical flows |
| CN103111212A (en) * | 2013-02-04 | 2013-05-22 | 西安交通大学 | Multi-point introduction structure and flow control mode of venturi mixer |
| CN103573760A (en) * | 2013-10-15 | 2014-02-12 | 西安交通大学 | Device for realizing incompressible fluid critical flow by applying mechanical choking principle |
| CN103851041A (en) * | 2014-03-10 | 2014-06-11 | 西安交通大学 | Critical incompressible fluid flow device with adjustable flow |
| CN105626020A (en) * | 2014-11-07 | 2016-06-01 | 中国石油化工股份有限公司 | Adjustable type steam flow control device |
-
2017
- 2017-07-31 CN CN201710641683.2A patent/CN107479585B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4139581A (en) * | 1976-09-16 | 1979-02-13 | Swanson Wilbur M | Carburetor |
| DE69521643D1 (en) * | 1994-04-30 | 2001-08-16 | Horiba Ltd | Changeable venturi section for critical flows |
| JPH0875621A (en) * | 1994-08-31 | 1996-03-22 | Tsukasa Sotsuken:Kk | Constant flow rate sampling apparatus using variable cross section critical flow venturi tube using movable venturi tube |
| CN103111212A (en) * | 2013-02-04 | 2013-05-22 | 西安交通大学 | Multi-point introduction structure and flow control mode of venturi mixer |
| CN103573760A (en) * | 2013-10-15 | 2014-02-12 | 西安交通大学 | Device for realizing incompressible fluid critical flow by applying mechanical choking principle |
| CN103851041A (en) * | 2014-03-10 | 2014-06-11 | 西安交通大学 | Critical incompressible fluid flow device with adjustable flow |
| CN105626020A (en) * | 2014-11-07 | 2016-06-01 | 中国石油化工股份有限公司 | Adjustable type steam flow control device |
Non-Patent Citations (3)
| Title |
|---|
| Development of Cavitation in Refrigerant (R-123) Flow Inside Rudimentary Microfluidic Systems;C. Mishra 等;《Journal of Microelectromechanical Systems》;20061030;第1319-1329段 * |
| The research of diesel multi-variable venturi intake pipes system;Zheng Wei;《2011 International Conference on Materials for Renewable Energy & Environment》;20110627;第830-835段 * |
| 文丘里喷管临界流动函数的研究;谢启明 等;《华东理工大学学报》;19960229;第22卷(第1期);第85-90段 * |
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