Efficient complex curved surface volute design method

Abstract

The invention discloses an efficient complex curved surface volute design method. The method comprises the steps that a centrifugal impeller, a vaneless diffuser and a volute are cooperatively designed; the method comprises the following steps: selecting initial design parameters of a volute, selecting circular section design of the volute according to a momentum moment conservation principle, performing 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 according to a three-dimensional model of the volute, and calculating a flow field of the flow channel fluid model. A fluid model of a volute flow channel is established through the three-dimensional model of the volute, the fluid model and the fluid model of the centrifugal impeller are subjected to coupling calculation, and the comprehensive aerodynamic efficiency eta of the centrifugal impeller and the volute is obtained; and judging that the comprehensive aerodynamic efficiency eta meets the design requirement until the design requirement is met. According to the design method, the aerodynamic efficiency between the volute and the centrifugal impeller can reach the optimal matching state, the energy conversion efficiency of a pneumatic system is improved, and energy loss caused by the volute is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of volutes, and in particular relates to a method for designing a highly efficient volute with a complex curved surface. Background Art

[0002] As a pneumatic component of a single-stage high-speed centrifugal blower, the volute can decelerate and increase the pressure of the airflow accelerated by the centrifugal impeller in the volute flow channel by increasing the flow area, and then discharge it through the volute outlet. As an energy conversion component, the volute converts the kinetic energy of the high-speed airflow into pressure potential energy and internal energy, and its conversion efficiency has a great influence on the operating efficiency of the whole machine; for the volute of a high-power centrifugal blower, sand casting is generally used, and the roughness of the volute flow channel 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 its flow rate and pressure. In addition, the surface roughness of the volute flow channel has a great influence on the aerodynamic performance. At present, it is basically determined by casting and there is no effective control measure. This will lead to the following defects: (1) The aerodynamic performance of the volute does not match the aerodynamic performance of the centrifugal impeller, resulting in low energy conversion efficiency. The air flow velocity in the volute flow channel has a great influence on the conversion efficiency. (2) The expansion pressure in the volute flow channel is insufficient, the flow rate is too fast, and the energy loss is large; (3) The quality of the volute flow channel surface is uncontrollable, and the surface with large roughness has a great influence on the efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide an efficient and complex curved volute design method, which matches the volute flow channel with the aerodynamic design of the centrifugal impeller, can give full play to the aerodynamic efficiency of the centrifugal impeller, improve the energy conversion efficiency of the pneumatic system, and reduce the energy loss caused by the mismatch between the aerodynamic performance of the volute and the centrifugal impeller. In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0005] According to one aspect of the present invention, the present invention provides an efficient complex curved surface volute design method, the complex curved surface volute design method comprising the following steps:

[0006] The centrifugal impeller, bladeless diffuser and volute are designed in coordination, and the gas parameters at the outlet of the bladeless diffuser are used as the input conditions for the volute design.

[0007] Select the initial design parameters of the volute, select the circular cross-section design of the volute according to the principle of conservation of momentum, and output the three-dimensional model of the volute;

[0008] The flow velocity control design inside the volute is to perform the initial design of the volute according to the gas conditions at the outlet of the vaneless diffuser. The flow channel fluid model of the volute is established based on the 3D 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 fluid model of the volute flow channel is established based on the three-dimensional model of the volute, and the coupling calculation is performed with the fluid model of the centrifugal impeller to obtain the velocity field, pressure field and temperature field of the centrifugal impeller and the volute, and the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute;

[0010] Determine whether the comprehensive aerodynamic efficiency η meets the design requirements. If so, complete the design. If not, adjust the initial design parameters of the volute and continue the design until it meets the design requirements.

[0011] According to the principle of conservation of angular momentum, the circular cross-section design of the volute meets the following requirements:

[0012]

[0013] Where: r c The central angle is The cross-sectional radius at , in mm;

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

[0015] R s The center angle When , the radius from the center of the volute to the maximum outer circle, in mm;

[0016] K is the speed coefficient and satisfies the following expression:

[0017]

[0018] Where: c 4u is the tangential velocity of the airflow at the diffuser outlet, in m / s;

[0019] R4 is the radius at the diffuser outlet, in mm;

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

[0021] In the above scheme, the calculation formula of the comprehensive aerodynamic efficiency η satisfies the following:

[0022]

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

[0024] The above scheme is further preferred, and the judgment process for determining whether the comprehensive aerodynamic efficiency η meets the design requirements is: if the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute ≥ 85%, the design of the volute meets the design requirements, and the performance of the volute and the centrifugal impeller are well matched; otherwise, it is necessary to return to the initial design parameters of the volute or modify the structural parameters of the centrifugal impeller, optimize the matching and improve, and then repeat the calculation until the comprehensive aerodynamic efficiency η ≥ 85% is achieved.

[0025] The above scheme is further preferred, the initial design parameters of the volute include the length L of the vaneless diffuser, the radius r of the circular section of the volute at each angular direction, c , volute inlet width b1 and volute outlet cone taper α.

[0026] The above scheme is further preferred. If the surface roughness of the volute does not meet the design requirements, in order to reduce the influence of the surface roughness of the volute flow channel on the aerodynamic efficiency, when the roughness Ra of the volute flow channel surface is greater than 3.2, the volute flow channel surface is coated.

[0027] In summary, the invention adopts the above technical solution, and the invention has the following technical effects:

[0028] (1) The present invention matches the design of the volute flow channel with the aerodynamic design of the centrifugal impeller, so that the aerodynamic efficiency of the combined design of the volute and the centrifugal impeller reaches the best state, and the aerodynamic efficiency of the centrifugal impeller can be fully utilized, so that the comprehensive aerodynamic efficiency of the centrifugal impeller and the volute is ≥85%, thereby improving the energy conversion efficiency of the pneumatic system and reducing the energy loss caused by the mismatch between the aerodynamic performance of the volute and the centrifugal impeller;

[0029] (2) According to the pressure and flow rate of the centrifugal impeller, the volute flow passage is not sufficiently expanded and the outlet flow velocity is too high. The cone tube can be used for auxiliary expansion to convert the air flow pressure into static pressure, thereby effectively controlling the velocity field in the volute flow passage, minimizing the aerodynamic loss of the volute and further improving the overall aerodynamic efficiency.

[0030] (3) The surface roughness of the volute flow channel can be improved by surface coating. From the manufacturing process, the surface of the volute flow channel is coated to improve the surface quality, reduce the roughness, reduce the energy loss of high-speed airflow on the flow channel surface, and improve the energy conversion loss of the volute. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic flow chart of an efficient and complex curved surface volute design method of the present invention;

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

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

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

[0035] Figure 5 It is a coupling aerodynamic performance calculation model of the centrifugal impeller and the volute flow channel fluid of the present invention; DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the invention more clearly understood, the invention is 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 only for the purpose of enabling the reader to have a thorough understanding of one or more aspects of the invention, and these aspects of the invention can be realized even without these specific details.

[0037] Combination Figure 1 and Figure 2 As shown, the present invention provides an efficient complex curved surface volute design method, the curved surface volute design method comprising the following steps:

[0038] Step 1: Co-design the centrifugal impeller, bladeless diffuser and volute, and use 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 of the maximum wheel rim of the centrifugal impeller, that is, 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 from the centrifugal impeller outlet to the bladeless diffuser inlet, mm; b2 is the width of the bladeless diffuser, mm; thus, the matching design of the volute aerodynamic performance and the centrifugal impeller aerodynamic performance can be completed:

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

[0040]

[0041] Where: r c The central angle is The cross-sectional radius at , in mm;

[0042] is the central angle, unit is rad;

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

[0044] K is the speed coefficient and satisfies the following expression:

[0045]

[0046] Where: c 4u is 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 volume flow rate at the volute inlet, unit: m 3 / min

[0049] Step 3, 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 based on 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, such as Figure 3 and Figure 4 As shown in the figure, the three-dimensional model of the flow channel fluid of the volute is to supplement the internal flow channel of the volute with a solid model, delete the solid model of the volute, retain only the fluid model of the internal flow channel, divide the grid, and set the material property to air fluid, that is, complete the establishment of the fluid finite element calculation model, thereby completing the design of the flow velocity control inside the volute;

[0050] To establish the flow channel fluid model of the volute, first of all, the radius of the circular section must be calculated based on the size of the central angle; then the three-dimensional flow channel of the volute is determined based on the outlet radius r5 and Rs of the bladeless diffuser; the diameter of the volute outlet is determined by the outlet gas flow rate. When the outlet flow rate is 50-80m / s, the volute fluid model can be established, such as Figure 3 When calculating the flow field, according to the finite element calculation model of the volute fluid, the boundary conditions of the volute inlet and outlet are set, and the finite element calculation is performed to obtain the velocity field of the volute fluid;

[0051] Step 4, the fluid model of the volute flow channel is established based on the three-dimensional model of the volute, and the fluid model of the centrifugal impeller is coupled (combined) for calculation to obtain the velocity field, pressure field and temperature field of the centrifugal impeller and the volute, and the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute; Figure 5 As shown in FIG. 1 , the steps of the joint calculation are to couple and assemble the fluid model of the centrifugal impeller with the fluid model of the volute flow channel, perform a joint calculation of the comprehensive aerodynamic performance, set the inlet conditions of the centrifugal impeller and the conditions of the volute outlet, and set the interactive section conditions of the centrifugal impeller and the volute, and then perform the calculation to obtain the velocity field, pressure field and temperature field of the centrifugal impeller and the volute, and obtain the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute; the comprehensive aerodynamic efficiency η can be obtained by comprehensively considering the continuity of the loss during the gas compression process, and can be calculated by the inlet and outlet temperatures and the inlet and outlet pressures. The calculation formula of the comprehensive aerodynamic efficiency η satisfies the following:

[0052]

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

[0054] Step 5, determine whether the comprehensive aerodynamic efficiency η meets the design requirements. If it meets the requirements, the design is completed. If it does not meet the requirements, the initial design parameters of the volute are adjusted to continue the design until it meets the design requirements. In the embodiment of the present invention, the initial design of the volute is performed according to the gas conditions at the outlet of the bladeless diffuser, and the flow field calculation of the volute flow channel fluid model is established 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 great influence on the energy conversion efficiency of the volute. According to the pressure Pvi and temperature Tvi of the volute inlet gas and the pressure Po and temperature To of the volute outlet gas, the operating efficiency η of the volute is calculated. v =f(Pvi,Tvi,Po,To), when η v ≥95%, the velocity field distribution in the volute flow channel is reasonable and the energy loss is not large; otherwise, repeat the iterative calculation from step 2 to step 4 until the centrifugal impeller and the volute meet the optimal aerodynamic performance matching, that is, η ≥ 85%, η v ≥95%.

[0055] In the embodiment of the present invention, the operating efficiency η is directly determined by the inlet pressure Pi and temperature Ti of the centrifugal impeller and the pressure Po and temperature To of the volute outlet. When the inlet conditions remain unchanged, that is, Pi and Ti remain unchanged, and Po / Pi is constant, the smaller To / Ti is, the higher the aerodynamic efficiency η is. The judgment process for judging whether the comprehensive aerodynamic efficiency η meets the design requirements is: 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 of the volute and the centrifugal impeller is well matched; otherwise, it is necessary to return to the initial design parameters of the volute or modify the structural parameters of the centrifugal impeller, optimize the matching and improve, and then repeat the above calculation steps until the comprehensive aerodynamic efficiency η is ≥85%.

[0056] In the embodiment of the present invention, if the roughness of the volute does not meet the design requirements, in order to reduce the impact of the roughness of the volute flow channel surface on energy loss, when the roughness Ra of the volute flow channel surface is greater than 3.2, the volute flow channel surface is coated; the roughness of the volute flow channel surface has a greater impact on its aerodynamic performance. Since most of them use sand casting, the flow channel surface quality is poor, and the roughness Ra is above 6.3, which affects the energy conversion efficiency of the volute by about 1-3%. For this reason, the application of coating materials on the surface of the volute flow channel can not only change the physical properties of the base material and improve the anti-corrosion ability of the volute, but also greatly improve the flow channel surface quality, further improve the energy conversion efficiency of the volute, the heat resistance temperature of the coating Tc ≥ 300 ° C, the coating thickness 0.1-0.3mm, and the coating roughness Ra ≤ 1.6.

[0057] The above is only a preferred embodiment of the invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the invention. These improvements and modifications should also be regarded as the scope of protection of the invention.

Claims

1. An efficient and complex curved volute design method, characterized by: The complex curved surface volute design method comprises the following steps: The centrifugal impeller, bladeless diffuser and volute are designed in coordination, and the gas parameters at the outlet of the bladeless diffuser are used as the input conditions for the volute design. Select the initial design parameters of the volute, select the circular cross-section design of the volute according to the principle of conservation of momentum, and output the three-dimensional model of the volute; The flow velocity control design inside the volute is to perform the initial design of the volute according to the gas conditions at the outlet of the vaneless diffuser. The flow channel fluid model of the volute is established based on the 3D 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 fluid model of the volute flow channel is established based on the three-dimensional model of the volute, and the coupling calculation is performed with the fluid model of the centrifugal impeller to obtain the velocity field, pressure field and temperature field of the centrifugal impeller and the volute, and the comprehensive aerodynamic efficiency η of the centrifugal impeller and the volute; Determine whether the comprehensive aerodynamic efficiency η meets the design requirements. If so, complete the design. If not, adjust the initial design parameters of the volute and continue the design until it meets the design requirements.

2. The method for designing a highly efficient and complex curved volute according to claim 1, characterized in that: According to the principle of conservation of angular momentum, the circular cross-section design of the volute meets the following requirements: Where: r c The central angle is The cross-sectional radius at , in mm; is the central angle, unit is rad; R s The center angle When , the radius from the center of the volute to the maximum outer circle, in mm; K is the speed coefficient and satisfies the following expression: Where: c 4u is the tangential velocity of the airflow at the diffuser outlet, in m / s; R4 is the radius at the diffuser outlet, in mm; Q4 is the volume flow rate at the volute inlet, unit: m 3 / min.

3. The method for designing a highly efficient and complex curved volute according to claim 1, characterized in that: The calculation formula of the comprehensive aerodynamic efficiency η satisfies the following: Where: η is the comprehensive aerodynamic efficiency of the centrifugal impeller and volute; k is the medium insulation coefficient, P o is the volute outlet pressure; P i is the centrifugal impeller inlet pressure; T o is the volute outlet temperature, T i is the centrifugal impeller inlet temperature.

4. A highly efficient complex curved volute design method according to claim 1 or 3, characterized in that: The judgment process for determining 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 ≥ 85%, the design of the volute meets the design requirements, and the performance of the volute and the centrifugal impeller is well matched; otherwise, it is necessary to return to the initial design parameters of the volute or modify the structural parameters of the centrifugal impeller, optimize the matching and improve, and then repeat the calculation until the comprehensive aerodynamic efficiency η ≥ 85% is achieved.

5. The method for designing a highly efficient and complex curved volute according to claim 1, characterized in that: The initial design parameters for the volute include the length L of the vaneless diffuser, the radius r of the circular section at each angle of the volute, and the length L of the vaneless diffuser. c , volute inlet width b1 and volute outlet cone taper α.

6. The method for designing a highly efficient and complex curved volute according to claim 4, characterized in that: If the surface roughness of the volute does not meet the design requirements, in order to reduce the impact of the surface roughness of the volute flow channel on the aerodynamic efficiency, when the roughness Ra of the volute flow channel surface is greater than 3.2, the volute flow channel surface is coated.

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