Optimal design method of cavity guide vane system with right-angle turning

Abstract

The application discloses an optimal design method of a right-angle turning cavity flow guide vane system, and belongs to the technical field of construction and energy loss measurement. The method is used for a square hollow floor slab, air inlets and air outlets are formed on two adjacent edges of the floor slab respectively, right-angle turning air ducts are formed between the air inlets and the air outlets to increase gas flow, the parameter relationship between total pressure loss of the air ducts and opening angles and azimuth angles of the flow guide vanes is calculated, and the optimal values of the opening angles and the azimuth angles of the flow guide vanes are determined through the parameter relationship under the premise that the total pressure loss is as small as possible. The relationship between the total pressure loss in the right-angle turning cavity and the number, position and size of the flow guide vanes is derived through the coupling thought of calculus and fluid mechanics, and the position of fluid and pipe wall separation is determined by introducing a boundary layer theory, so that the optimal size of the flow guide vanes is determined. The method has simple steps, strong theoretical basis and good design effect.

Description

Technical Field

[0001] This invention belongs to the field of construction and energy loss measurement technology, and particularly relates to an optimal design method for a right-angle turning cavity guide vane system. Background Technology

[0002] In practical engineering, right-angle turning cavities are widely used in cavity floor slab smoke exhaust, cavity floor slab ventilation, and other fire protection and fluid engineering fields. During operation, fluid flows into the cavity from the inlet end, undergoes complex fluid motion within the cavity, and then flows out from the outlet, with the inlet and outlet axes perpendicular to each other. Guide vanes are widely used as an effective structure to mitigate pressure loss within right-angle turning cavities. Their main function is to guide the fluid to turn, thereby reducing the number of vortices within the cavity and thus reducing pressure loss caused by vortices.

[0003] Currently, the computational approach of coupling fluid mechanics and calculus is a common method for determining the energy loss of a right-angle turning cavity with guide vanes. However, to date, the analysis of the effect of guide vanes in right-angle turning cavities is limited to numerical software simulations and experimental measurements, with no relevant research on theoretical formulas. Furthermore, the cumbersome numerical simulation steps and complex experimental designs affect the results, and distortions in numerical experiments and inaccuracies in measuring instruments can also lead to errors. Therefore, both of these methods exhibit significant instability and have obvious drawbacks. Summary of the Invention

[0004] To address the shortcomings of existing technologies, an optimal design method for a right-angle turning cavity guide vane system is provided. This method can calculate the pressure loss of the right-angle turning cavity under the action of the guide vane and fill theoretical gaps, thereby enabling precise design of the guide vane system and reducing construction difficulties.

[0005] To achieve the above objectives, the present invention provides an optimal design method for a right-angle turning hollow cavity guide vane system, used in a square hollow floor slab. The square hollow floor slab has an air inlet and an air outlet on two adjacent sides, respectively. Guide vanes are installed within the hollow floor slab to form a right-angle turning air duct between the air inlet and outlet, thereby increasing the gas flow rate. By calculating the parameter relationship between the total pressure loss of the air duct and the opening angle and azimuth angle of the guide vanes, the optimal values ​​of the opening angle and azimuth angle of the guide vanes are determined based on the above parameter relationship, while minimizing the total pressure loss. The optimal length and optimal position of the guide vanes can be determined from the opening angle and azimuth angle, respectively. The upper limit of the opening angle of the guide vanes is constrained by the relationship between the opening angle of the guide vanes and the deflection angle during fluid-wall separation, avoiding an infinite value.

[0006] The specific steps are as follows:

[0007] The air duct between the air inlet and outlet of the hollow floor slab is equivalent to a quarter-circle arc structure. The width of the duct is equal to the width of the air inlet and outlet. The center of the quarter-circle arc is taken as the origin. The angle between the two ends of the guide vane at the origin O is defined as the guide vane opening angle α, and the angle between one end of the guide vane and the horizontal plane is defined as the guide vane azimuth angle θ. The number of guide vanes in the cavity formed by the quarter-circle arc structure is n. Since the volumetric flow rate is constant, the average inlet velocity, average outlet velocity, and initial inlet velocity of the fluid are equal, all denoted by v. The distance from the origin O to the left side of the air inlet is R1, and the distance from the origin O to the right side of the air inlet is R2. The equivalent diameter of the constant velocity section of the air inlet is D. The distance between adjacent guide vanes is D. i The distance from the right side of the air inlet to the right boundary of the cavity is R3; the thickness of the hollow floor slab cavity and the thickness of the air duct are b.

[0008] The air duct is divided into three regions: region A is the part with an angle of 0-θ°, region B is the part with an angle of θ°-α°, and region C is the part with an angle of α°-90°.

[0009] By dividing regions A and C into multiple micro-arcs, the trend of fluid shear stress on each micro-arc with the fluid velocity on that micro-arc is calculated, and then the viscous pressure loss of the fluid in regions A and C is calculated.

[0010] By dividing regions A and C into infinitesimal arcs, calculating the turning energy loss of each infinitesimal arc, and then integrating the results, the right-angle turning energy loss of regions A and C can be calculated.

[0011] The total pressure loss of regions A and C is calculated by summing the viscous pressure loss and the energy loss during right-angle turns in each region A and C.

[0012] By dividing region B into multiple micro-arcs, the turning loss and the pressure loss of the pressurized pipe flow when the guide vanes are present on each micro-arc are calculated. Then, integration is performed to calculate the right-angle turning loss and the pipe flow loss in region B. The total pressure loss of region B is calculated by using the relationship that the total pressure loss of region B is equal to the sum of the right-angle turning loss and the pipe flow pressure loss.

[0013] The total pressure loss inside the quarter-circular arc-shaped air duct is calculated by adding the total losses of regions A, B, and C.

[0014] This confirms the existence of a boundary layer formed between the blades of the guide vanes due to the bend in the air duct between the air inlet and the air outlet, and at the same time obtains the actual flow field information of the quarter-circular arc air duct.

[0015] By analyzing the relationship between the boundary layer formation area inside a right-angle bend pipe and the pipe diameter, bend angle, and wind speed, the distance D between the guide vane opening angle α and the adjacent guide vane is calculated based on the total pressure loss within the cavity. i The constraint relationship between the cavity inlet velocity v and the cavity inlet velocity v

[0016] Finally, the optimal position of the guide vanes is determined by the angle θ between the lower right sidewall of the guide vane and the bottom edge; the optimal length of the guide vanes is obtained by multiplying the guide vane opening angle by the guide vane radius α; in addition, the optimal length of the guide vanes is determined by the distance D between the guide vane opening angle α and the adjacent guide vanes. i The constraints between them can determine the optimal distance D between adjacent guide vanes. ad Meanwhile, since the distance between the uppermost and lowermost blades of the guide vane is always equal to the fluid width R2-R1 at the inlet, the optimal number of guide vanes is determined to be...

[0017] Furthermore, the specific steps for determining the viscous pressure loss in regions A and C are as follows:

[0018] In regions A and C, the fluid, under pressure, undergoes a turn towards the outlet direction. During the turn, due to the lack of constraint, the fluid moves into various parts of the cavity, forming vortices of varying sizes near the four corners of the cavity under the action of viscous forces. These vortices are products of fluid energy dissipation, and the work done by the viscous forces between them and the main flow of the quarter-circle duct is equal to the magnitude of the viscous energy loss. Region A2 is defined as the area within the included angle of the main flow of the quarter-circle duct in region A, and region A1 is defined as the area outside. Region C2 is defined as the area within the included angle of the main flow of the quarter-circle duct in region C, and region C1 is defined as the area outside.

[0019] According to Newton's law of internal friction, the shear stress at any point within the fluid in region A1 of the right-angled cavity is related to the velocity gradient as follows:

[0020]

[0021] v Ar1 =ω Ar1 ·r ρ

[0022]

[0023] In the formula: τ A1 This represents the shear stress between fluid particles in a fluid. μ For dynamic viscosity, v Ar1 Let ω represent the velocity at any point in the vortex generated in region A1. Ar1 The angular velocity r represents the rotational velocity of the vortex around its center. ρThe distance from the vortex center to any point in the vortex;

[0024] By dividing region A1 into multiple infinitesimal rings, calculating the viscous force energy loss of each individual ring, and then integrating, we obtain:

[0025]

[0026] In the formula: W 黏A1 This represents the energy loss in region A1 caused by viscous forces; where b represents the thickness of the cavity, and R2 represents the distance from the origin O to the right side of the inlet. Similarly, the viscous force loss in region A2 can be obtained as follows:

[0027]

[0028] v Ar2 =ω Ar2 ·r ρ

[0029]

[0030]

[0031] In the formula: τ A2 v represents the shear stress between the fluid layers in region A2. Ax2 Let ω represent the velocity at any point in the vortex. Ar2 W represents the angular velocity of rotation of the vortex around its center. 黏A2 This represents the energy loss in region A2 caused by viscous forces;

[0032] Therefore, the total energy loss in region A caused by viscous forces is:

[0033] W 黏A =W 黏A1 +W 黏A2

[0034] Similarly, the total energy loss in region C caused by viscous forces is:

[0035] W 黏C =W 黏C1 +W 黏C2

[0036] in:

[0037]

[0038] v Cr1 =ω Cr1 ·r ρ

[0039]

[0040]

[0041] v Cr2 =ω Cr2 ·r ρ

[0042]

[0043]

[0044] In the formula: τ C1 τ C2 V represents the shear stress between different fluid layers in regions C1 and C2, respectively. Cr1 v Cr2 Let ω represent the velocity at any point in the vortex in regions C1 and C2, respectively. Cr1 ω Cr2 τ represents the rotational angular velocity of the vortex around the vortex center in regions C1 and C2, respectively. C1 τ C2 W represents the shear stress between the flow layers in regions C1 and C2, respectively. 黏C1 W 黏C2 These represent the energy losses caused by viscous forces in regions C1 and C2, respectively.

[0045] Furthermore, the calculation process for the energy loss during right-angle turns in regions A and C is as follows:

[0046] The energy losses in regions A and C include not only energy losses caused by viscous forces, but also energy losses caused by airflow turning. The pressure loss caused by airflow turning is:

[0047]

[0048]

[0049]

[0050] Where: ΔP dA h represents the pressure loss in area A caused by the right-angle turn. dA α represents the energy loss caused by the right-angle turn in the airflow in region A; dA d is the pressure loss coefficient for right-angle turns in area A; 入 Let be the isovelocity equivalent diameter of the inlet area of ​​region A;

[0051]

[0052]

[0053]

[0054] Where: ΔP dC h represents the pressure loss caused by the right-angle turn in area C. dC α represents the energy loss caused by the right-angle turn of the airflow in region C; dC The pressure loss coefficient for right-angle turns in region C; d 出 The isovelocity equivalent diameter of the outlet area of ​​region C is numerically equal to d. 入 .

[0055] Furthermore, the calculation of the total pressure loss in regions A and C includes:

[0056] ΔP A =ρg·W 黏A +ΔP dA

[0057] ΔP C =ρg·W 黏C +ΔP dC

[0058] Where: ΔP A ΔP C These represent the total pressure losses in regions A and C, respectively.

[0059] Furthermore, based on the theory of pressurized pipe head loss, the right-angle bend loss and friction loss along the pipe in region B are calculated, thereby calculating the total pressure loss in region B, including:

[0060] The total pressure loss in region B includes friction loss and turning loss, where friction loss is expressed as:

[0061]

[0062]

[0063] Where: ΔP Ba Let l be the friction loss along region B, and λ be the friction coefficient, which can be obtained from classical fluid mechanics formulas. B Let d be the average length of the guide tube in region B. B Let be the isovelocity equivalent area of ​​the flow tube in region B, which is numerically equivalent to d_out.

[0064] In addition, the turning loss within the air duct of Region B is:

[0065]

[0066]

[0067]

[0068] Where: ΔP dBh is the pressure loss caused by the bend in duct area B. dB The energy loss caused by the right-angle turn of the airflow in region B; α dB The pressure loss coefficient for right-angle turns in region C.

[0069] Therefore, the total pressure loss in region B can be calculated as follows:

[0070] ΔP B =ΔP Ba +ΔP dB

[0071] Where: ΔP B This represents the total pressure loss in region B.

[0072] Furthermore, the calculation of the total pressure loss within the cavity includes:

[0073] ΔP=ΔP A +ΔP B +ΔP C

[0074] In the formula: ΔP represents the total pressure loss inside the cavity, ΔP A ΔP represents the pressure loss within the air duct of region A. B ΔP represents the pressure loss within the air duct of region B. C This indicates the pressure loss within the air duct of area A.

[0075] Furthermore, the constraint relationship between the opening angle of the guide vane and its dimensions is as follows:

[0076] The fluid separates from the lower wall of the guide vane, and the resulting separation boundary layer generates a huge pressure loss. It also causes extremely high pressure on the upper wall of the guide vane, leading to the collapse of the upper wall structure of the guide vane.

[0077] In a right-angle duct bend cavity, to extend the cavity life and reduce the wear of the guide vanes, the spacing of each guide vane is constrained. The azimuth angle and opening angle that minimize the total pressure loss within the duct cavity are then determined.

[0078] Let β represent the deflection angle at which fluid-wall separation occurs, D i This represents the distance between adjacent guide vanes. For a fluid entering the duct with an average initial velocity v, the higher the fluid velocity, the more pronounced the fluid-wall separation phenomenon. In this case, the fluid separation deflection angle within the duct will decrease; therefore, the deflection angle β is negatively correlated with the average initial velocity v. Similarly, the larger the duct inlet diameter, the more severe the separation phenomenon. The deflection angle β is related to the distance D between adjacent guide vanes. i They are also negatively correlated. From the above analysis, the relationship between the three parameters is as follows:

[0079]

[0080] In the formula: K is a constant, determined by experimental data and boundary conditions; a and m are quantitative parameters for liquid wall separation, obtained by experimental testing.

[0081] Given a fixed average inlet velocity v, to avoid fluid-wall separation inside the guide vanes, the maximum opening angle α of the guide vanes is... max Should meet:

[0082] α max ≤β

[0083] By combining the above equations, the optimal deflector opening angle α can be determined. ad With the optimal guide vane azimuth angle θ ad Here, the deflection angle β is taken to be numerically equal to α. ad The optimal spacing D between adjacent guide vanes can be obtained. ad The calculation formula is as follows:

[0084]

[0085] Since the distance between each guide vane is consistent, and the fluid width at the inlet end is equal to the cavity inlet width R2-R1, the optimal number of guide vanes can be determined as follows:

[0086]

[0087] Beneficial effects: This method determines the basic layout pattern of the right-angle bend cavity and divides the cavity into three analysis regions A, B, and C; it determines the viscous pressure loss in analysis regions A and C based on calculus and Newton's law of internal friction in fluid mechanics; it determines the right-angle bend energy loss in regions A and C based on calculus and fundamental fluid mechanics theory; it calculates the total pressure loss in regions A and C respectively; it calculates the right-angle bend loss and pipe friction loss in region B based on the theory of pressurized pipe head loss, thereby calculating the total pressure loss in region B; it calculates the total pressure loss within the cavity; and it determines the constraint relationship between the opening angle and size of the guide vanes based on the fluid-boundary separation theory of right-angle pipes. This invention uses the calculus-fluid mechanics coupling concept to derive the relationship between the total pressure loss in the right-angle bend cavity and the number, position, and size of the guide vanes, and introduces boundary layer theory to determine the position where the fluid separates from the pipe wall, thus determining the optimal size of the guide vanes. Compared to the limitations of traditional calculation methods that only involve numerical software simulation and experiments, this method can predict and analyze the optimal placement of guide vanes at the theoretical level. It can directly reflect the relationship between various parameters through formulas, thus avoiding time-consuming numerical simulations and tedious experiments. It has good innovative ideas and is a simple calculation suitable for engineering design.

[0088] By calculating the optimal guide vane opening angle, optimal guide vane azimuth angle, and optimal number of guide vanes, the energy loss of fluid in right-angle turning cavities can be significantly reduced. If the guide vanes are designed arbitrarily, the energy loss reduction is small, while the design method described in this invention can maximize the energy loss reduction of the guide vanes in the cavity, thereby significantly reducing fluid energy loss. Attached Figure Description

[0089] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0090] Figure 1 This is a schematic diagram of the right-angle turning cavity in an embodiment of the present invention.

[0091] Figure 2 This is a three-dimensional schematic diagram of a right-angle turning cavity according to an embodiment of the present invention;

[0092] Figure 3 This is a schematic diagram of the cavity region division according to an embodiment of the present invention;

[0093] Figure 4 This is a diagram showing the vortex distribution within the cavity in an embodiment of the present invention;

[0094] Figure 5 This is a schematic diagram of fluid-wall separation between adjacent guide vanes in an embodiment of the present invention;

[0095] Figure 6 This is a flowchart of an embodiment of the present invention.

[0096] In the diagram: α is the deflector opening angle, θ is the deflector azimuth angle, and α is the deflector azimuth angle. ad Optimal guide vane opening angle, θ ad Optimal guide vane azimuth angle, n number of blades, n ad Optimal number of blades, distance of R1O from the left end of the air inlet, distance of R2O from the left end of the air inlet, distance of R3 from the right end of the air inlet to the right boundary of the cavity, b cavity thickness, D i The distance between adjacent guide vanes, D ad Optimal distance between adjacent guide vanes, D (equivalent diameter of the air inlet), v (average velocity of the fluid inlet and outlet), K (constant), a, m (quantitative parameters for liquid wall separation), α max Maximum opening angle. Detailed implementation method:

[0097] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0098] like Figure 1 and Figure 2As shown, the present invention discloses an optimal design method for a right-angle turning hollow cavity guide vane system, used in a square hollow floor slab. The square hollow floor slab has an air inlet and an air outlet on two adjacent sides, respectively. Guide vanes are installed inside the hollow floor slab to form a right-angle turning air duct between the air inlet and the air outlet, thereby increasing the gas flow rate. By calculating the parameter relationship between the total pressure loss of the air duct and the opening angle and azimuth angle of the guide vanes, the optimal values ​​of the opening angle and azimuth angle of the guide vanes are determined based on the above parameter relationship, while minimizing the total pressure loss. The optimal length and optimal position of the guide vanes can be determined from the opening angle and azimuth angle, respectively. The upper limit of the opening angle of the guide vanes is constrained by the relationship between the opening angle of the guide vanes and the deflection angle during fluid-wall separation, avoiding an infinite value.

[0099] The specific steps are as follows:

[0100] like Figure 3 and Figure 4 As shown, the air duct between the air inlet and outlet of the hollow floor slab is equivalent to a quarter-circle arc structure. The width of the air duct is equal to the width of the air inlet and outlet. The origin of the quarter-circle arc structure is taken as the center of the arc. The angle between the two ends of the guide vane at the origin O is defined as the guide vane opening angle α, and the angle between one end of the guide vane and the horizontal plane is defined as the guide vane azimuth angle θ. The number of guide vanes in the air duct cavity formed by the quarter-circle arc structure is n. Since the volumetric flow rate is constant, the average inlet velocity, average outlet velocity, and initial inlet velocity of the fluid are equal, all denoted by v. The distance from the origin O to the left side of the air inlet is R1, and the distance from the origin O to the right side of the air inlet is R2. The equivalent diameter of the constant velocity section of the air inlet is D. The distance between adjacent guide vanes is D_0. i The distance from the right side of the air inlet to the right boundary of the cavity is R3; the thickness of the hollow floor slab cavity and the thickness of the air duct are b.

[0101] The air duct is divided into three regions: region A is the part with an angle of 0-θ°, region B is the part with an angle of θ°-α°, and region C is the part with an angle of α°-90°.

[0102] By dividing regions A and C into multiple micro-arcs, the trend of fluid shear stress on each micro-arc with the fluid velocity on that micro-arc is calculated, and then the viscous pressure loss of the fluid in regions A and C is calculated.

[0103] The specific steps for determining the viscous pressure loss in regions A and C are as follows:

[0104] In regions A and C, the fluid, under pressure, undergoes a turn towards the outlet direction. During the turn, due to the lack of constraint, the fluid moves into various parts of the cavity, forming vortices of varying sizes near the four corners of the cavity under the action of viscous forces. These vortices are products of fluid energy dissipation, and the work done by the viscous forces between them and the main flow of the quarter-circle duct is equal to the magnitude of the viscous energy loss. Region A2 is defined as the area within the included angle of the main flow of the quarter-circle duct in region A, and region A1 is defined as the area outside. Region C2 is defined as the area within the included angle of the main flow of the quarter-circle duct in region C, and region C1 is defined as the area outside.

[0105] According to Newton's law of internal friction, the shear stress at any point within the fluid in region A1 of the right-angled cavity is related to the velocity gradient as follows:

[0106]

[0107] v Ar1 =ω Ar1 ·r ρ

[0108]

[0109] In the formula: τ A1 This represents the shear stress between fluid particles in a fluid. μ For dynamic viscosity, v Ar1 Let ω represent the velocity at any point in the vortex generated in region A1. Ar1 The angular velocity r represents the rotational velocity of the vortex around its center. ρ The distance from the vortex center to any point in the vortex;

[0110] By dividing region A1 into multiple infinitesimal rings, calculating the viscous force energy loss of each individual ring, and then integrating, we obtain:

[0111]

[0112] In the formula: W 黏A1 This represents the energy loss in region A1 caused by viscous forces; where b represents the thickness of the cavity, and R2 represents the distance from the origin O to the right side of the inlet. Similarly, the viscous force loss in region A2 can be obtained as follows:

[0113]

[0114] v Ar2 =ω Ar2 ·r ρ

[0115]

[0116]

[0117] In the formula: τ A2 v represents the shear stress between the fluid layers in region A2. Ax2 Let ω represent the velocity at any point in the vortex. Ar2 W represents the angular velocity of rotation of the vortex around its center. 黏A2 This represents the energy loss in region A2 caused by viscous forces;

[0118] Therefore, the total energy loss in region A caused by viscous forces is:

[0119] W 黏A =W 黏A1 +W 黏A2

[0120] Similarly, the total energy loss in region C caused by viscous forces is:

[0121] W 黏C =W 黏C1 +W 黏C2

[0122] in:

[0123]

[0124] v Cr1 =ω Cr1 ·r ρ

[0125]

[0126]

[0127] v Cr2 =ω Cr2 ·r ρ

[0128]

[0129]

[0130] In the formula: τ C1 τ C2 V represents the shear stress between different fluid layers in regions C1 and C2, respectively. Cr1 v Cr2 Let ω represent the velocity at any point in the vortex in regions C1 and C2, respectively. Cr1 ω Cr2 τ represents the rotational angular velocity of the vortex around the vortex center in regions C1 and C2, respectively. C1 τ C2 W represents the shear stress between the flow layers in regions C1 and C2, respectively.黏C1 W 黏C2 These represent the energy losses caused by viscous forces in regions C1 and C2, respectively.

[0131] By dividing regions A and C into infinitesimal arcs, calculating the turning energy loss of each infinitesimal arc, and then integrating the results, the right-angle turning energy loss of regions A and C can be calculated.

[0132] The calculation process for energy loss during right-angle turns in regions A and C is as follows:

[0133] The energy losses in regions A and C include not only energy losses caused by viscous forces, but also energy losses caused by airflow turning. The pressure loss caused by airflow turning is:

[0134]

[0135]

[0136]

[0137] Where: ΔP dA h represents the pressure loss in area A caused by the right-angle turn. dA α represents the energy loss caused by the right-angle turn in the airflow in region A; dA d is the pressure loss coefficient for right-angle turns in area A; 入 Let be the isovelocity equivalent diameter of the inlet area of ​​region A;

[0138]

[0139]

[0140]

[0141] Where: ΔP dC h represents the pressure loss caused by the right-angle turn in area C. dC α represents the energy loss caused by the right-angle turn of the airflow in region C; dC The pressure loss coefficient for right-angle turns in region C; d 出 The isovelocity equivalent diameter of the outlet area of ​​region C is numerically equal to d. 入 ;

[0142] The total pressure loss of regions A and C is calculated by summing the viscous pressure loss and the energy loss during right-angle turns in each region A and C.

[0143] The total pressure loss in regions A and C is calculated as follows:

[0144] ΔP A=ρg·W 黏A +ΔP dA

[0145] ΔP C =ρg·W 黏C +ΔP dC

[0146] Where: ΔP A ΔP C These represent the total pressure losses in regions A and C, respectively.

[0147] By dividing region B into multiple micro-arcs, the turning loss and the pressure loss of the pressurized pipe flow when the guide vanes are present on each micro-arc are calculated. Then, integration is performed to calculate the right-angle turning loss and the pipe flow loss in region B. The total pressure loss of region B is calculated by using the relationship that the total pressure loss of region B is equal to the sum of the right-angle turning loss and the pipe flow pressure loss.

[0148] Based on the theory of pressurized pipe head loss, the right-angle bend loss and pipe friction loss in region B are calculated, thus the total pressure loss in region B is calculated, including:

[0149] The total pressure loss in region B includes friction loss and turning loss, where friction loss is expressed as:

[0150]

[0151]

[0152] Where: ΔP Ba Let l be the friction loss along region B, and λ be the friction coefficient, which can be obtained from classical fluid mechanics formulas. B Let d be the average length of the guide tube in region B. B The isovelocity equivalent area of ​​the flow tube in region B is numerically equivalent to d. 出 ;

[0153] In addition, the turning loss within the air duct of Region B is:

[0154]

[0155]

[0156]

[0157] Where: ΔP dB h is the pressure loss caused by the bend in duct area B. dB The energy loss caused by the right-angle turn of the airflow in region B; α dB The pressure loss coefficient for right-angle turns in region C.

[0158] Therefore, the total pressure loss in region B can be calculated as follows:

[0159] ΔP B =ΔP Ba +ΔP dB

[0160] Where: ΔP B This represents the total pressure loss in region B.

[0161] The total losses in regions A, B, and C are added together to calculate the total pressure loss within the quarter-circular arc-shaped duct structure. The calculation of the total pressure loss includes:

[0162] ΔP=ΔP A +ΔP B +ΔP C

[0163] In the formula: ΔP represents the total pressure loss inside the cavity, ΔP A ΔP represents the pressure loss within the air duct of region A. B ΔP represents the pressure loss within the air duct of region B. C This indicates the pressure loss within the air duct of area A.

[0164] This confirms the existence of a boundary layer formed between the blades of the guide vanes due to the bend in the air duct between the air inlet and the air outlet, and at the same time obtains the actual flow field information of the quarter-circular arc air duct.

[0165] By analyzing the relationship between the boundary layer formation area inside a right-angle bend pipe and the pipe diameter, bend angle, and wind speed, the distance D between the guide vane opening angle α and the adjacent guide vane is calculated based on the total pressure loss within the cavity. i The constraint relationship between the cavity inlet velocity v and the cavity inlet velocity v

[0166] like Figure 5 As shown, the optimal position of the guide vanes is finally determined by the angle θ between the lower right sidewall of the guide vane and the bottom edge; the optimal length of the guide vanes is obtained by multiplying the guide vane opening angle by the guide vane radius α; in addition, the optimal length of the guide vanes is determined by the distance D between the guide vane opening angle α and the adjacent guide vanes. i The constraints between them can determine the optimal distance D between adjacent guide vanes. ad Meanwhile, since the distance between the uppermost and lowermost blades of the guide vane is always equal to the fluid width R2-R1 at the inlet, the optimal number of guide vanes is determined to be...

[0167] The constraint relationship between the opening angle of the guide vane and its dimensions is as follows:

[0168] The fluid separates from the lower wall of the guide vane, and the resulting separation boundary layer generates a huge pressure loss. It also causes extremely high pressure on the upper wall of the guide vane, leading to the collapse of the upper wall structure of the guide vane.

[0169] In a right-angle duct bend cavity, to extend the cavity life and reduce the wear of the guide vanes, the spacing of each guide vane is constrained. The azimuth angle and opening angle that minimize the total pressure loss within the duct cavity are then determined.

[0170] Let β represent the deflection angle at which fluid-wall separation occurs, D i This represents the distance between adjacent guide vanes. For a fluid entering the duct with an average initial velocity v, the higher the fluid velocity, the more pronounced the fluid-wall separation phenomenon. In this case, the fluid separation deflection angle within the duct will decrease; therefore, the deflection angle β is negatively correlated with the average initial velocity v. Similarly, the larger the duct inlet diameter, the more severe the separation phenomenon. The deflection angle β is related to the distance D between adjacent guide vanes. i They are also negatively correlated. From the above analysis, the relationship between the three parameters is as follows:

[0171]

[0172] In the formula: K is a constant, determined by experimental data and boundary conditions; a and m are quantitative parameters for liquid wall separation, obtained by experimental testing.

[0173] Given a fixed average inlet velocity v, to avoid fluid-wall separation inside the guide vanes, the maximum opening angle α of the guide vanes is... max Should meet:

[0174] α max ≤β

[0175] By combining the above equations, the optimal deflector opening angle α can be determined. ad With the optimal guide vane azimuth angle θ ad Here, the deflection angle β is taken to be numerically equal to α. ad The optimal spacing D between adjacent guide vanes can be obtained. ad The calculation formula is as follows:

[0176]

[0177] Since the distance between each guide vane is consistent, and the fluid width at the inlet end is equal to the cavity inlet width R2-R1, the optimal number of guide vanes can be determined as follows:

[0178]

[0179] The total pressure loss within the cavity, calculated as total pressure loss = total loss of A + total loss of B + total loss of C, is directly related to α and θ. The formula for total pressure loss includes these two unknown parameters. When other measurable parameters (pipe diameter, inlet velocity, etc., which can be measured by instruments) are determined, the total pressure loss is only related to the two parameters mentioned above. To ensure the minimum total pressure loss, these two parameters should be taken with appropriate values. Furthermore, according to boundary layer theory, α is related to β, provided that fluid-wall separation does not occur. β, in turn, is related to two unknown but measurable parameters, D and v. Once these two parameters are determined, the specific values ​​of a, b, and A can be known experimentally. At this point, β is determined, and the constraint α ≤ β constrains the upper limit of α, ensuring that the opening angle of the guide vanes is within a certain range and not excessively large.

[0180] The optimal position is θ, which is the angle between the lower right sidewall of the guide vane and the bottom edge. Since the radius of the guide vane arrangement is equal to the radius of the fluid turning inside the cavity (so that the fluid flow path is semi-circular), knowing θ can completely determine the position of the guide vane arrangement.

[0181] Furthermore, once α is known, the optimal length of the guide vane can be determined. As mentioned above, once the radius of the guide vane is determined, the length of the guide vane = α multiplied by the radius of the guide vane.

[0182] In the design and construction method of guide vanes, the opening angle α of the guide vane is used to represent its length parameter. Therefore, in this patent, it is not necessary to explain the step of multiplying by the radius of the guide vane. The same applies to the azimuth angle θ of the guide vane. The position of the guide vane can be directly represented by this azimuth angle, without further explanation.

Claims

1. An optimal design method for a right-angle turning cavity guide vane system, characterized in that: This design is used for square hollow floor slabs, where air inlets and outlets are located on two adjacent sides. Guide vanes are installed within the hollow floor slab to create a right-angle bend in the airflow between the inlets and outlets, increasing gas flow. The optimal values ​​for the guide vane opening angle and azimuth angle are determined by calculating the relationship between the total pressure loss of the airflow duct and the opening angle and azimuth angle of the guide vanes, minimizing the total pressure loss. The optimal length and position of the guide vanes can be determined from their opening angle and azimuth angle. An upper limit is constrained for the opening angle of the guide vanes by considering the relationship between the opening angle and the deflection angle during fluid-wall separation, preventing it from reaching an infinite value. The specific steps are as follows: The air duct between the air inlet and outlet of the hollow core slab is equivalent to a quarter-circle arc structure, with the duct width equal to the width of the air inlet and outlet. Taking the center of the quarter-circle arc as the origin, the angle formed by the two boundaries of the guide vanes at the origin O is defined as the guide vane opening angle. The angle between one end of the guide vane and the horizontal plane is defined as the guide vane azimuth angle. The number of guide vanes installed in the cavity of the quarter-circular arc structure is n. Since the volumetric flow rate is constant, the average inlet velocity, average outlet velocity, and initial inlet velocity of the fluid are equal, all of which are... This indicates that the distance from the origin O to the left side of the air inlet is... The distance from the origin O to the right side of the air inlet is The equivalent diameter of the constant velocity at the air inlet cross-section is: Distance between adjacent guide vanes ; The distance from the right side of the air inlet to the right boundary of the cavity is The thickness of the hollow core slab cavity and the thickness of the air duct are: ; Arrange the air duct at an angle Partially divided into region A, Partially divided into region B, Part of it is divided into region C; By dividing regions A and C into multiple micro-arcs, the trend of fluid shear stress on each micro-arc with the fluid velocity on that micro-arc is calculated, and then the viscous pressure loss of the fluid in regions A and C is calculated. By dividing regions A and C into infinitesimal arcs, calculating the turning energy loss of each infinitesimal arc, and then integrating the results, the right-angle turning energy loss of regions A and C can be calculated. Calculate the total pressure loss of region A and region C by summing the viscous pressure loss and the energy loss during right-angle turns in region A and region C respectively; By dividing region B into multiple micro-arcs, the turning loss and the pressure loss of the pressurized pipe flow when the guide vanes are present on each micro-arc are calculated. Then, integration is performed to calculate the right-angle turning loss and the pipe flow loss in region B. The total pressure loss of region B is calculated by using the relationship that the total pressure loss of region B is equal to the sum of the right-angle turning loss and the pipe flow pressure loss. The total pressure loss inside the quarter-circular arc-shaped air duct is calculated by adding the total losses of regions A, B, and C. This confirms the existence of a boundary layer formed between the blades of the guide vanes due to the bend in the air duct between the air inlet and the air outlet, and at the same time obtains the actual flow field information of the quarter-circular arc air duct. By analyzing the relationship between the boundary layer formation region inside a right-angle bend duct and the duct diameter, bend angle, and wind speed, the guide vane opening angle is calculated based on the total pressure loss within the cavity. Distance between adjacent guide vanes and cavity inlet velocity The constraints between them Finally, the angle between the lower right sidewall of the guide vane and the bottom edge Determine the optimal position for the guide vanes; by multiplying the guide vane opening angle by the guide vane radius. To obtain the optimal length of the guide vanes, in addition, the guide vane opening angle... Distance between adjacent guide vanes The constraints between them can determine the optimal distance between adjacent guide vanes. Meanwhile, since the distance between the uppermost and lowermost blades of the guide vane is always equal to the width of the fluid at the inlet end... Thus, the optimal number of guide vanes is determined. .

2. The optimal design method for a right-angle turning cavity guide vane system as described in claim 1, characterized in that, The specific steps for determining the viscous pressure loss in regions A and C are as follows: In regions A and C, the fluid undergoes a turn towards the outlet direction under pressure. During the turn, due to the lack of constraint, the fluid moves to various parts of the cavity. Under the action of viscous force, vortices of varying sizes are formed at the four corners near the cavity. These vortices are products of fluid energy dissipation, and the work done by the viscous force between them and the main flow of the quarter-circle duct is equal to the amount of energy lost by the viscous force. Region A2 is defined as the area within the included angle of the main flow of the quarter-circle duct in region A, and region A1 is defined as the area outside. Region C2 is defined as the area within the included angle of the main flow of the quarter-circle duct in region C, and region C1 is defined as the area outside. According to Newton's law of internal friction, the shear stress at any point within the fluid in region A1 of the right-angled cavity is related to the velocity gradient as follows: ， ， ， In the formula: This represents the shear stress between fluid particles in a fluid. For dynamic viscosity, This represents the velocity at any point in the vortex generated in region A1. This represents the angular velocity of rotation of the vortex around its center. The distance from the vortex center to any point in the vortex; By dividing region A1 into multiple infinitesimal rings, calculating the viscous force energy loss of each individual ring, and then integrating, we obtain: ， In the formula: This represents the energy loss in region A1 caused by viscous forces; where... Indicates the thickness of the cavity. This represents the distance from the origin O to the right side of the entrance. Similarly, the viscous force loss in region A2 is: ， In the formula: This represents the shear stress between the fluid layers in region A2. Represents the velocity at any point in the eddy current. This represents the angular velocity of rotation of the vortex around its center. This represents the energy loss in region A2 caused by viscous forces; Therefore, the total energy loss in region A caused by viscous forces is: ， Similarly, the total energy loss in region C caused by viscous forces is: ， in: ， ， In the formula: , These represent the shear stresses between different fluid layers in regions C1 and C2, respectively. , Let C1 and C2 represent the velocities at any point in the eddy currents, respectively. , These represent the rotational angular velocities of the vortex around the vortex core in regions C1 and C2, respectively. , These represent the shear stresses between the flow layers in regions C1 and C2, respectively. , These represent the energy losses caused by viscous forces in regions C1 and C2, respectively.

3. The optimal design method for a right-angle turning cavity guide vane system as described in claim 2, characterized in that, The calculation process for energy loss during right-angle turns in regions A and C is as follows: The energy losses in regions A and C include not only energy losses caused by viscous forces, but also energy losses caused by airflow turning. The pressure loss caused by airflow turning is: ， ， ， In the formula: The pressure loss in area A caused by the right-angle turn; The energy loss caused by the right-angle turn in the airflow in region A; The pressure loss coefficient for right-angle turns in area A; Let be the isovelocity equivalent diameter of the inlet area of ​​region A; ， ， ， In the formula: The pressure loss is caused by the right-angle turn in area C; This refers to the energy loss caused by the right-angle turn of the airflow in region C; The pressure loss coefficient for right-angle turns in region C; The isovelocity equivalent diameter of the outlet area of ​​region C is numerically equal to... .

4. The optimal design method for a right-angle turning cavity guide vane system as described in claim 3, characterized in that, The total pressure loss in regions A and C is calculated as follows: ， ， In the formula: , These represent the total pressure losses in regions A and C, respectively.

5. The optimal design method for a right-angle turning cavity guide vane system as described in claim 4, characterized in that, Based on the theory of pressurized pipe head loss, the right-angle bend loss and pipe friction loss in region B are calculated, thus the total pressure loss in region B is calculated, including: The total pressure loss in region B includes friction loss and turning loss, where friction loss is expressed as: ， In the formula: For pressure loss along the friction path in region B, The friction factor can be obtained from classical fluid mechanics formulas. The average length of the guide tube in region B. The isovelocity equivalent diameter of the flow tube in region B is numerically equivalent to... ; In addition, the turning loss within the air duct of Zone B is: ， ， ， In the formula: This refers to the pressure loss caused by the bend in duct area B; This refers to the energy loss caused by the right-angle turn of the airflow in region B; The pressure loss coefficient for right-angle turns in region C; Therefore, the total pressure loss in region B can be calculated as follows: ， In the formula: This represents the total pressure loss in region B.

6. The optimal design method for a right-angle turning cavity guide vane system as described in claim 5, characterized in that, The calculation of total pressure loss within the cavity includes: ， In the formula: Indicates the total pressure loss within the cavity. This represents the total pressure loss within region A. This represents the total pressure loss within region B. This represents the total pressure loss within region C.

7. The optimal design method for a right-angle turning cavity guide vane system as described in claim 1, characterized in that, The constraint relationship between the opening angle of the guide vane and its dimensions is as follows: The fluid separates from the lower wall of the guide vane, and the resulting separation boundary layer generates a huge pressure loss. It also causes extremely high pressure on the upper wall of the guide vane, leading to the collapse of the upper wall structure of the guide vane. In a right-angle duct bend cavity, to extend the cavity life and reduce the wear of the guide vanes, the spacing of each guide vane is constrained. The azimuth angle and opening angle that minimize the total pressure loss within the duct cavity are then determined. use This indicates the deflection angle at which fluid-wall separation occurs. This represents the distance between adjacent guide vanes, for an average initial velocity of... As the fluid enters the duct, the higher the fluid velocity, the more pronounced the fluid-wall separation phenomenon. At this point, the fluid separation deflection angle within the duct will decrease, therefore the deflection angle... With the average initial velocity of the fluid There is a negative correlation; similarly, the larger the diameter of the duct inlet, the more severe the separation phenomenon and the greater the deflection angle. Distance between adjacent guide vanes They are also negatively correlated. From the above analysis, the relationship between the three parameters is as follows: ， In the formula: It is a constant, determined jointly by experimentally measured data and boundary conditions. All parameters are quantitative parameters for liquid-wall separation, obtained through experimental testing. At an average inlet velocity of Given a fixed premise, to avoid fluid-wall separation inside the guide vanes, the maximum opening angle of the guide vanes is... It should meet the following requirements: ， By combining the above formulas, the optimal deflector opening angle can be determined. With the optimal azimuth angle of the guide vane Take the deflection angle here. Numerically equal to The optimal spacing between adjacent guide vanes can be obtained. The calculation formula is as follows: ， Because the distance between each guide vane is consistent, and the fluid width at the inlet is equal to the width at the cavity inlet. The optimal number of guide vanes can be determined as follows: 。

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