A high-efficiency complex curved surface volute design method

Abstract

The application discloses a high-efficiency complex curved volute design method, which comprises the following steps: carrying out collaborative design on a centrifugal impeller, a vaneless diffuser and a volute; selecting initial design parameters of the volute; selecting a circular cross-section design of the volute according to the principle of momentum conservation; carrying out initial design of the volute according to gas conditions at an outlet of the vaneless diffuser; establishing a flow channel fluid model of the volute from a three-dimensional model of the volute; calculating a flow field of the flow channel fluid model; coupling calculation of the flow channel fluid model of the volute and a fluid model of the centrifugal impeller from the three-dimensional model of the volute; and obtaining comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute; and judging whether the comprehensive aerodynamic efficiency η meets design requirements until the design requirements are met. The design method can make the aerodynamic efficiency between the volute and the centrifugal impeller reach an optimal matching state, improve energy conversion efficiency of an aerodynamic system and reduce energy loss of the volute.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of volute, in particular to a high-efficiency complex curved surface volute design method. BACKGROUND

[0002] As an aerodynamic component of single-stage high-speed centrifugal blower, the volute can slow down the airflow accelerated by the centrifugal impeller in the volute flow passage through the increase of the flow area, and then discharge through the volute outlet. As an energy conversion component, the volute converts the kinetic energy of high-speed airflow into pressure potential energy and internal energy, and the conversion efficiency has a great influence on the overall operation efficiency. For the volute of a high-power centrifugal blower, the sand casting method is generally used, and the roughness of the volute flow passage surface is uncontrollable, which affects the energy conversion efficiency of the volute.

[0003] At present, the aerodynamic design of the volute is basically independent of the aerodynamic design of the centrifugal impeller. Generally, after the aerodynamic design of the centrifugal impeller is completed, the existing volute is selected according to the flow rate and pressure. In addition, the surface roughness of the volute flow passage has a great influence on the aerodynamic performance, which is basically determined by casting and has no effective control measures. Therefore, the following defects will be caused: (1) the aerodynamic performance of the volute does not match the aerodynamic performance of the centrifugal impeller, resulting in low energy conversion efficiency, and the airflow velocity in the volute flow passage has a great influence on the conversion efficiency, (2) the pressure recovery in the volute flow passage is insufficient, the flow velocity is too fast, and the energy loss is large, and (3) the quality of the volute flow passage surface is uncontrollable, and the rough surface has a great influence on the efficiency. SUMMARY

[0004] The purpose of the present application is to provide a high-efficiency complex curved surface volute design method. The present application matches the aerodynamic design of the volute flow passage with the centrifugal impeller, which can fully utilize the aerodynamic efficiency of the centrifugal impeller, improve the energy conversion efficiency of the aerodynamic system, and reduce the energy loss caused by the mismatch of the aerodynamic performance of the volute and the centrifugal impeller. In order to achieve the above purpose, the present application adopts the following technical scheme:

[0005] According to one aspect of the present application, a high-efficiency complex curved surface volute design method is provided, which comprises the following steps:

[0006] The centrifugal impeller, the vaneless diffuser and the volute are designed cooperatively, and the gas parameters at the outlet of the vaneless diffuser are taken as the input conditions for the design of the volute;

[0007] The initial design parameters of the volute are selected, the circular cross-section design of the volute is selected according to the principle of momentum conservation, and a three-dimensional model of the volute is outputted;

[0008] The flow rate control design inside the volute is performed according to the gas condition at the outlet of the vaneless diffuser, a flow channel fluid model of the volute is established based on a three-dimensional model of the volute, and the flow field of the flow channel fluid model is calculated to obtain the velocity field of the fluid;

[0009] The flow channel fluid model of the volute is coupled with the fluid model of the centrifugal impeller to perform calculation, and the velocity field, pressure field and temperature field of the centrifugal impeller and the volute are obtained to obtain the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute;

[0010] The comprehensive aerodynamic efficiency η is judged to meet the design requirements, if the requirements are met, the design is completed, if the requirements are not met, the initial design parameters of the volute are adjusted to continue the design until the design requirements are met.

[0011] According to the principle of momentum conservation, the circular cross section of the volute is selected to meet the following requirements:

[0012]

[0013] In the formula, r c is the cross-sectional radius at the central angle , unit: mm;

[0014] is the central angle, unit: rad;

[0015] R s is the radius from the center of the volute to the maximum outer circle when the central angle is, unit: mm;

[0016] K is a velocity coefficient, and satisfies the following expression:

[0017]

[0018] In the formula, c 4u is the tangential velocity of the gas flow at the outlet of the diffuser, unit: m / s;

[0019] R4 is the radius at the outlet of the diffuser, unit: mm;

[0020] Q4 is the volume flow rate at the inlet of the volute, unit: m 3 / min.

[0021] Further preferably, the comprehensive aerodynamic efficiency η calculation formula satisfies the following:

[0022]

[0023] In the formula, η is the comprehensive aerodynamic efficiency of the centrifugal impeller and the volute; k is the medium adiabatic coefficient, P o is the outlet pressure of the volute; P iis the pressure at the inlet of the centrifugal impeller; T o is the temperature at the outlet of the volute, i is the temperature at the inlet of the centrifugal impeller.

[0024] The judgment process of judging whether the comprehensive aerodynamic efficiency η meets the design requirement is further preferably: if the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute is ≥ 85%, the design of the volute meets the design requirement, and the performance matching of the volute and the centrifugal impeller is good; otherwise, the initial design parameters of the volute or the structural parameters of the centrifugal impeller are returned to or modified, and then the optimization matching improvement is performed, and then the calculation is repeated until the comprehensive aerodynamic efficiency η ≥ 85%.

[0025] The selection of the initial design parameters of the volute includes the length L of the vaneless diffuser, the radius r of the circular section of the volute in each angle direction, c the width b1 of the inlet of the volute, and the taper α of the taper pipe at the outlet of the volute.

[0026] When the surface roughness of the volute does not meet the design requirement, the surface coating is performed on the surface of the volute flow passage to reduce the influence of the surface roughness of the volute flow passage on the aerodynamic efficiency when the surface roughness Ra of the surface of the volute flow passage is greater than 3.2.

[0027] According to the technical scheme, the technical effects of the application are as follows:

[0028] (1) The design of the volute flow passage is matched with the aerodynamic design of the centrifugal impeller, the aerodynamic efficiency of the combined design of the volute and the centrifugal impeller reaches the best state, the aerodynamic efficiency of the centrifugal impeller can be fully utilized, the comprehensive aerodynamic efficiency of the volute and the centrifugal impeller is ≥ 85%, the energy conversion efficiency of the aerodynamic system is improved, and the energy loss caused by the mismatching of the aerodynamic performance of the volute and the centrifugal impeller is reduced.

[0029] (2) According to the pressure and the flow of the centrifugal impeller, the pressure expansion of the volute flow passage is insufficient, and the flow velocity at the outlet is too high, the taper pipe can be used for auxiliary pressure expansion, the kinetic pressure of the airflow is converted into static pressure, the velocity field in the volute flow passage is effectively controlled, the aerodynamic loss of the volute is minimized, and the comprehensive aerodynamic efficiency is further improved.

[0030] (3) The surface roughness of the volute flow passage can be improved by using the surface coating, the surface quality of the volute flow passage is improved by coating the surface of the volute flow passage, the surface quality is improved, the roughness is reduced, the energy loss of the high-speed airflow on the surface of the flow passage is reduced, and the energy conversion loss of the volute is improved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a flowchart of a high-efficiency complex curved volute design method of the application;

[0032] Figure 2 This is a schematic diagram of the matching connection between the centrifugal impeller and the bladeless diffuser of the present invention;

[0033] Figure 3 This is a schematic diagram of the three-dimensional fluid model of the volute flow channel of the present invention;

[0034] Figure 4 This is a schematic diagram of the flow channel fluid model of the volute of the present invention;

[0035] Figure 5 This invention provides a calculation model for the coupled aerodynamic performance of the centrifugal impeller and the fluid in the volute flow channel. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the invention, and these aspects of the invention can be achieved even without these specific details.

[0037] Combination Figure 1 and Figure 2 As shown, this invention provides an efficient method for designing complex curved surface volutes, the method comprising the following steps:

[0038] Step 1: Design the centrifugal impeller, bladeless diffuser, and volute together, using the gas parameters at the outlet of the bladeless diffuser as the input conditions for the volute design, such as... Figure 2 As shown, r3 is the radius at the maximum rim of the centrifugal impeller, i.e., the radius of the centrifugal impeller outlet; r4 is the inlet radius of the bladeless diffuser; r5 is the outlet radius of the bladeless diffuser; r1 is the inlet hub radius of the centrifugal impeller, mm; r2 is the inlet tip radius of the centrifugal impeller, mm; b1 is the width of the transition section between the centrifugal impeller outlet and the inlet of the bladeless diffuser, mm; b2 is the width of the bladeless diffuser, mm; thus, the matching design of the aerodynamic performance of the volute and the centrifugal impeller can be completed.

[0039] Step 2: Select the initial design parameters for the volute, choose the circular cross-section design of the volute based on the principle of conservation of angular momentum, and output the 3D model of the volute, such as... Figure 3 As shown; the outlet pressure of the volute of a high-power-density supersonic centrifugal blower is 30kPa to 200kPa, and a bladeless diffuser is generally used. The outlet pressure and flow rate of the centrifugal impeller, combined with parameters such as gas velocity V, pressure P, flow rate Q, and temperature T at the outlet of the bladeless diffuser, are used as input conditions for the volute design. The initial design parameters for the volute include the length of the bladeless diffuser L = r5 - r4, and the radius r of the circular cross-section in each angular direction of the volute. cThe inlet width b2 of the volute and the taper α of the volute outlet cone (generally α≤16°, in this invention α=12.9°); based on the principle of conservation of angular momentum, the circular cross-section design of the volute is selected to meet the following requirements:

[0040]

[0041] In the formula: r c With the central angle as The radius of the cross section at that location, in mm;

[0042] The central angle, in rad;

[0043] R s central angle When, the radius from the center of the volute to the maximum outer circle, in mm;

[0044] K is the velocity coefficient, and it satisfies the following expression:

[0045]

[0046] In the formula: c 4u denoted as the tangential velocity of the airflow at the diffuser outlet, in m / s;

[0047] R4 is the radius at the diffuser outlet, in mm;

[0048] Q4 is the volumetric flow rate at the inlet of the volute, in cubic meters per second (m³). 3 / min

[0049] Step 3: Based on the gas conditions at the outlet of the bladeless diffuser, perform the initial design of the volute. Establish the flow channel fluid model of the volute from the 3D model of the volute, and calculate the flow field of the flow channel fluid model to obtain the fluid velocity field, such as... Figure 3 and Figure 4 As shown, the three-dimensional fluid model of the volute is to supplement the internal flow channels of the volute with solid models, delete the solid models of the volute, retain only the fluid models of the internal flow channels, and mesh them. The material properties are set to air fluid, thus completing the establishment of the fluid finite element calculation model, thereby completing the design of the internal flow velocity control of the volute.

[0050] To establish a fluid model of the volute casing, firstly, the radius of the circular cross-section is calculated based on the central angle; then, the three-dimensional flow channel of the volute casing is determined based on the outlet radius r5 and Rs of the bladeless diffuser; the diameter of the volute casing outlet is determined by the outlet gas velocity. When the outlet velocity is 50–80 m / s, the fluid model of the volute casing can be established. Figure 3 As shown. In the flow field calculation, based on the finite element model of the volute fluid, the boundary conditions at the volute inlet and outlet are set, and finite element calculations are performed to obtain the velocity field of the fluid within the volute.

[0051] Step 4: A fluid model of the volute flow channel is established from the 3D model of the volute and coupled (jointly calculated) with the fluid model of the centrifugal impeller to obtain the velocity, pressure, and temperature fields of the centrifugal impeller and volute, thus obtaining the combined aerodynamic efficiency η of the centrifugal impeller and volute; For example... Figure 5 As shown, the joint calculation steps involve coupling and assembling the fluid model of the centrifugal impeller and the fluid model of the volute flow channel together to perform joint calculations of comprehensive aerodynamic performance. This involves setting the inlet conditions of the centrifugal impeller and the outlet conditions of the volute, as well as the interaction section conditions between the centrifugal impeller and the volute. Calculations are then performed to obtain the velocity, pressure, and temperature fields of the centrifugal impeller and the volute, leading to the comprehensive aerodynamic efficiency η. The comprehensive aerodynamic efficiency η is calculated by considering the continuity of losses during gas compression, using the inlet and outlet temperatures and pressures. The formula for calculating the comprehensive aerodynamic efficiency η satisfies the following:

[0052]

[0053] In the formula: η is the combined aerodynamic efficiency of the centrifugal impeller and volute; k is the adiabatic coefficient of the medium, which can be taken as 1.4 for air and is dimensionless; P o P is the outlet pressure of the volute, expressed in Pascals (Pa). i T represents the inlet pressure of the centrifugal impeller, expressed in Pascals (Pa); o T is the outlet temperature of the volute, in Kelvin (K); i The inlet temperature of the centrifugal impeller can be taken as the ambient temperature, and the unit is K (K).

[0054] Step 5: Determine if the overall aerodynamic efficiency η meets the design requirements. If it does, the design is complete; otherwise, adjust the initial design parameters of the volute and continue designing until the requirements are met. In this embodiment of the invention, the initial design of the volute is performed based on the gas conditions at the outlet of the bladeless diffuser. Flow field calculations are performed on the volute flow channel fluid model to obtain the velocity field of the fluid. Since the volute is a key component for achieving high-speed airflow deceleration and pressurization, its velocity has a significant impact on the energy conversion efficiency of the volute. Based on the pressure Pvi and temperature Tvi of the gas at the volute inlet and the pressure Po and temperature To of the gas at the volute outlet, the operating efficiency η of the volute is calculated. v = f(Pvi, Tvi, Po, To), when η v If η ≥ 95%, the velocity field distribution within the volute flow channel is reasonable, and energy loss is minimal; otherwise, repeat the iterative calculations from steps 2 to 4 until the optimal aerodynamic performance matching between the centrifugal impeller and the volute is satisfied, i.e., η ≥ 85%, η v ≥95%.

[0055] In the embodiment of the present application, the operation efficiency η is directly determined by the inlet pressure Pi, temperature Ti of the centrifugal impeller and the pressure Po, temperature To of the volute outlet, when the inlet conditions are unchanged, that is, Pi, Ti are unchanged, and Po / Pi is constant, the smaller To / Ti is, the higher the aerodynamic efficiency η is; the judgment process of judging whether the comprehensive aerodynamic efficiency η meets the design requirements is as follows: if the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute is ≥ 85%, the design of the volute meets the design requirements, and the performance matching of the volute and the centrifugal impeller is good; otherwise, the initial design parameters of the volute or the structural parameters of the centrifugal impeller need to be returned or modified, and after optimization and matching improvement, the above calculation steps are repeated until the comprehensive aerodynamic efficiency η is ≥ 85%.

[0056] In the embodiment of the present application, if the roughness of the volute does not meet the design requirements, in order to reduce the influence of the roughness of the volute flow passage surface on energy loss, when the roughness Ra of the volute flow passage surface is greater than 3.2, the flow passage surface of the volute is coated with a coating; the roughness of the flow passage surface has a great influence on the aerodynamic performance of the volute, because sand casting is mostly used, the quality of the flow passage surface is poor, the roughness Ra is greater than 6.3, and the energy conversion efficiency of the volute is affected by about 1-3%. Therefore, the coating material is applied to the flow passage surface of the volute, which can change the physical properties of the base material, improve the corrosion resistance of the volute, greatly improve the quality of the flow passage surface, and further improve the energy conversion efficiency of the volute; the heat resistance temperature Tc of the coating is ≥ 300℃, the thickness of the coating is 0.1-0.3mm, and the roughness Ra of the coating is ≤ 1.6.

[0057] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for designing a high-efficiency complex curved volute, characterized in that: The complex curved volute design method comprises the following steps: The centrifugal impeller, the vaneless diffuser and the volute are designed cooperatively, and the gas parameters at the outlet of the vaneless diffuser are taken as the input conditions for the volute design; Selecting initial design parameters of the volute, selecting a circular cross-section design of the volute according to the principle of conservation of angular momentum, and outputting a three-dimensional model of the volute; the initial design parameters of the volute include the length L of the vaneless diffuser, the radius r of the circular cross-section of the volute in each angle direction, the width b1 of the volute inlet, and the taper α of the taper pipe of the volute gas outlet c . The volute internal flow velocity control design is performed, the initial design of the volute is performed according to the gas conditions at the outlet of the vaneless diffuser, the flow channel fluid model of the volute is established from the three-dimensional model of the volute, and the flow field of the flow channel fluid model is calculated to obtain the velocity field of the fluid; The flow channel fluid model of the volute is coupled with the fluid model of the centrifugal impeller to perform calculation, the velocity field, the pressure field and the temperature field of the centrifugal impeller and the volute are obtained, and the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute is obtained; The judgment process that the comprehensive aerodynamic efficiency η meets the design requirement is as follows: if the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute is greater than or equal to 85%, the design of the volute meets the design requirement, and the performance matching of the volute and the centrifugal impeller is good; otherwise, the initial design parameters of the volute or the structural parameters of the centrifugal impeller need to be adjusted, and the optimization matching improvement is performed, and then the calculation is repeated until the comprehensive aerodynamic efficiency η is greater than or equal to 85%. If the surface roughness of the volute does not meet the design requirement, in order to reduce the influence of the surface roughness of the volute flow channel on the aerodynamic efficiency, when the surface roughness Ra of the volute flow channel is greater than 3.2, the surface of the volute flow channel is coated. In the formula: r c R is the radius of the cross section at the central angle of φ, in mm; for the central angle, in rad; R s R is the radius from the center of the volute to the maximum outer circle for a central angle of φ, in mm; K is a speed coefficient, and satisfies the following expression: wherein: Vt is the tangential velocity of the gas flow at the diffuser outlet, in m / s; R is the radius at the diffuser exit, in mm; Qvol is the volume flow at the inlet of the volute, in m3 / min.

2. The method of designing a high-efficiency complex curved volute according to claim 1, wherein: ​ wherein: is the overall aerodynamic efficiency of the centrifugal impeller and volute; is the medium adiabatic coefficient, is the volute outlet pressure; is the centrifugal impeller inlet pressure; is the volute outlet temperature, is the centrifugal impeller inlet temperature.

3. The method of designing a high-efficiency complex curved volute according to claim 1 or 2, characterized in that: ​ 4. The method of designing a high-efficiency complex curved volute according to claim 3, wherein: ​

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