Aluminum alloy impeller of Roots blower, extrusion die and extrusion process
阅读说明：本技术 罗茨鼓风机铝合金叶轮和挤压模具及挤压工艺 (Aluminum alloy impeller of Roots blower, extrusion die and extrusion process ) 是由 刘厚根 黄元春 李辉 黄艺龙 薛江涛 王诚 黄龙林 陆地华 夏政军 张昭强 于 2020-05-25 设计创作，主要内容包括：本发明公开了一种罗茨鼓风机铝合金叶轮和挤压模具及挤压工艺,其中罗茨鼓风机铝合金叶轮包括叶轮本体,叶轮本体中心位置开设轴孔,叶轮本体具有至少两个叶轮齿组成的叶轮型线；叶轮本体为铝合金材质；各叶轮齿上均开设减重孔。罗茨鼓风机铝合金叶轮的挤压模具包括分流模上模和分流模下模；分流模下模中心位置开设与叶轮本体叶轮型线对应的模孔；分流模上模中心位置设有模芯,模芯包括与轴孔位置对应的第一圆柱件、与减重孔位置对应的第二柱件。经实际试验,本发明挤压成形的鼓风机铝合金叶轮的型面的粗糙度优于(尺寸精度接近或达到)传统数控刨削(铣削)铸铁叶轮,降低了制造成本；并且铝合金叶轮重量轻,减少了罗茨鼓风运行的能耗。(The invention discloses a Roots blower aluminum alloy impeller, an extrusion die and an extrusion process, wherein the Roots blower aluminum alloy impeller comprises an impeller body, the center of the impeller body is provided with a shaft hole, and the impeller body is provided with an impeller molded line consisting of at least two impeller teeth; the impeller body is made of aluminum alloy; each impeller tooth is provided with a lightening hole. The extrusion die of the Roots blower aluminum alloy impeller comprises a split-flow die upper die and a split-flow die lower die; a die hole corresponding to the impeller molded line of the impeller body is formed in the center of the lower die of the split-flow die; and a mold core is arranged at the center of the upper mold of the split-flow mold, and the mold core comprises a first cylindrical part corresponding to the position of the shaft hole and a second cylindrical part corresponding to the position of the lightening hole. Through practical tests, the roughness of the molded surface of the aluminum alloy impeller of the air blower formed by extrusion is superior to (the size precision is close to or reaches) that of the traditional numerical control planing (milling) cast iron impeller, so that the manufacturing cost is reduced; and the aluminum alloy impeller is light in weight, and reduces the energy consumption of Roots blast operation.)
1. An aluminum alloy impeller of a Roots blower comprises an impeller body (1), wherein a shaft hole (101) is formed in the center of the impeller body (1) along the length direction, and the impeller body (1) is provided with at least two impeller teeth (102); the impeller is characterized in that the impeller body (1) is made of aluminum alloy.
2. The aluminum alloy impeller for roots blower as set forth in claim 1, wherein each of the impeller teeth (102) is formed with a lightening hole (1021) parallel to the axial line of the axial hole (101).
3. An extrusion die for an aluminum alloy impeller of a roots blower as set forth in claim 1 or 2, comprising a split die upper die (2) and a split die lower die (3);
a die hole (301) corresponding to the shape of the outer contour of the impeller body (1) is formed in the center of the lower splitting die (3), and the lower splitting die (3) is further provided with a plurality of welding chambers (302) arranged on the periphery of the die hole (301);
mould (2) central point puts and is equipped with mold core (201) on the reposition of redundant personnel mould, mold core (201) include first cylinder (2011) that correspond with shaft hole (101) position, and mould (2) still are equipped with reposition of redundant personnel hole (202) with seam room (302) one-to-one on the reposition of redundant personnel mould, are equipped with reposition of redundant personnel bridge (203) between adjacent reposition of redundant personnel hole (202).
4. The extrusion die for the aluminum alloy impeller of the Roots blower according to claim 3, wherein each impeller tooth (102) is provided with a weight reduction hole (1021) parallel to the axis of the shaft hole (101); the mold core (201) further comprises a second cylindrical piece (2012) corresponding to the position of the lightening hole (1021).
5. The extrusion die for aluminum alloy impeller of Roots blower according to claim 3 or 4, wherein the die bore bearing (3011) inside the die bore (301) has a height that decreases from the top of the impeller to the root of the impeller.
6. The extrusion process of the Roots blower aluminum alloy impeller is characterized by comprising the following steps of:
step A, three-dimensional modeling is carried out on the extrusion die of any one of claims 3 to 5 by using software A;
step B, importing the three-dimensional model established in the step A into software B, and establishing a finite element model of the impeller section aluminum alloy extrusion process;
step C, setting extrusion process parameters, the height of a die hole sizing belt (3011) on the inner side of a die hole (301) and the height of a die core sizing belt (2013) on the outer side of a die core (201) for the finite element model;
d, processing and manufacturing the extrusion die by using the finite element model obtained in the step C;
and E, selecting an aluminum blank, and executing an aluminum alloy extrusion forming process by using the extrusion die obtained in the step D to obtain the aluminum alloy impeller of the Roots blower.
7. The extrusion process for an aluminum alloy impeller of a Roots blower according to claim 6, wherein in step C, the die hole sizing bands (3011) are arranged in a height that decreases from the top of the impeller to the root of the impeller.
8. The extrusion process for an aluminum alloy impeller for a Roots blower as set forth in claim 6, wherein in step C, the core bearing (2013) has a uniform height throughout.
Technical Field
The invention belongs to the technical field of Roots blowers (vacuum pumps), and particularly relates to an aluminum alloy impeller of a Roots blower, an extrusion die and an extrusion process.
Background
The Roots blower belongs to a positive displacement fan, is widely applied to various departments of the national economy, and mainly has the following advantages: the device has the characteristic of forced gas transmission; secondly, the device belongs to a rotary machine, has no reciprocating mechanism and no air valve, has few easily-damaged parts and has longer service life; moreover, the device has the characteristics of simple structure, convenient use and maintenance, no need of internal lubrication, almost constant air exhaust amount in a use pressure range, high volume efficiency and no oil contained in a conveying medium.
The impeller is a key part of the Roots blower, and the manufacturing quality and the processing precision of the impeller directly influence the working efficiency of the Roots blower. The existing impeller is made of cast iron, an impeller blank is realized through a casting process, and the molded surface of the impeller is machined by numerical control planing (milling). In the casting production process of the impeller, the casting has the defects of shrinkage cavity, shrinkage porosity and the like, so that the yield of the impeller blank is low, and the numerical control machining of the molded surface of the impeller is one of the main machining costs of the Roots blower.
Disclosure of Invention
Drawings
FIG. 1 is a schematic structural diagram of the cross section of an aluminum alloy impeller of a Roots blower.
Fig. 2 is a schematic view of the structure of the upper die of the splitting die.
Fig. 3 is a schematic view of the lower die structure of the split die.
Fig. 4 is a three-dimensional model diagram of an aluminum alloy impeller extrusion die of a roots blower, wherein fig. 4(a) is a three-dimensional model diagram of an upper die, and fig. 4(b) is a three-dimensional model diagram of a lower die.
FIG. 5 is a diagram of a finite element model of hollow impeller profile extrusion.
FIG. 6 is a graph of the die initial sizing height profile.
Fig. 7 is a flow velocity profile at the die exit.
Fig. 8 is a velocity distribution diagram of the distribution holes in different directions, in which fig. 8(a) shows a velocity distribution of the distribution holes in the X direction, fig. 8(b) shows a velocity distribution of the distribution holes in the Y direction, and fig. 8(c) shows a velocity distribution of the distribution holes in the Z direction.
FIG. 9 is a graph of the temperature profile from the orifice region to the profile exit during extrusion.
FIG. 10 is a graph of the optimized die bearing height profile.
Fig. 11 is a velocity profile at the die exit after optimization of the bearing height.
The impeller comprises an
Detailed Description
Embodiments of the present invention are described below with reference to the accompanying drawings.
As shown in fig. 1, the aluminum alloy impeller for the roots blower of the invention comprises an
Each impeller tooth 102 is provided with a lightening hole 1021 parallel to the axial line of the shaft hole 101.
The roots blower wheel has three wheel teeth 102.
The extrusion die for the aluminum alloy impeller of the Roots blower comprises a split die
The center of the lower splitting die 3 is provided with a die hole 301 corresponding to the outside of the
The mold core 201 is arranged at the center of the
The invention also provides an extrusion process of the Roots blower aluminum alloy impeller, which comprises the following steps:
step A, performing three-dimensional modeling on the extrusion die by using software A (such as UG software) to obtain a three-dimensional model diagram shown in fig. 4, wherein fig. 4(a) is a three-dimensional model diagram of an upper die, and fig. 4(b) is a three-dimensional model diagram of a lower die.
And step B, importing the three-dimensional model established in the step A into software B (such as Hyperxtruded software), and establishing a finite element model of the impeller section aluminum alloy extrusion process, as shown in FIG. 5.
Step C, setting extrusion process parameters, the height of a die hole sizing belt 3011 on the inner side of a die hole 301 and the height of a die core sizing belt 2013 on the outer side of a die core 201 for the finite element model; the height of the die hole sizing band 3011 is set according to the rule that the height decreases from the top of the impeller to the root of the impeller, and the heights of the die core sizing bands 2013 are consistent.
And D, processing and manufacturing the extrusion die by using the finite element model obtained in the step C.
And E, selecting an aluminum blank, and executing an aluminum alloy extrusion forming process by using the extrusion die obtained in the step D to obtain the aluminum alloy impeller of the Roots blower.
The aluminum alloy impeller of the Roots blower is obtained by utilizing an aluminum alloy extrusion forming process, the extruded aluminum alloy can obtain a stronger and more uniform three-dimensional compressive stress state in a deformation zone in the extrusion process, the section with a complex section shape can be realized, the precision of an extruded product is relatively high, the surface quality is good, the utilization rate and the yield of materials can be greatly improved, the extrusion process flow is short, and the production is convenient.
The principles of the present invention are described in detail below:
the aluminum alloy extrusion process can be used for manufacturing solid and hollow sections with various purposes, and has wide application fields. In the hot extrusion process, the aluminum alloy is preheated to a certain temperature, pressure is applied to cause the aluminum alloy to flow out of a specific die hole 301, and a desired cross-sectional shape is obtained after cooling. It is a three-dimensional non-linear flow that is often accompanied by high temperatures, high pressures, complex friction conditions, and complex thermal coupling problems. The numerical technology such as finite element analysis is helpful to obtain information such as temperature and speed in the extrusion process, potential defects of the section can be found in advance through virtual die trial, and then structural parameters of the die are optimized so as to process high-quality sections meeting requirements.
The Hyperxtrude software is based on any Lagrange-Euler (ALE) method, the grid points and the object points have flexible mutual movement modes, the grid can move independently of the object, and grid distortion possibly caused by grid repartitioning in the simulation process is effectively avoided. In the hot aluminum extrusion forming process, the contact surface of the aluminum billet and the die is in a high friction and bonding state, the extruded section surface is in a free motion state, and the ALE method can adopt a flexible description mode for different states, so that the accuracy and efficiency of numerical simulation are improved.
The Roots blower impeller adopts an aluminum alloy extrusion process, has high material utilization rate, replaces the numerical control planing (milling) processing process of the traditional Roots blower cast iron impeller, and reduces the manufacturing cost.
Taking a Roots blower aluminum alloy impeller as an example, numerical simulation is carried out by using Hyperxtrude software, the flow speed and the temperature distribution rule of the aluminum alloy in the extrusion process are analyzed, and the height of a sizing belt is optimized to obtain the impeller profile determined by design parameters.
1. Simulation of aluminum alloy impeller extrusion process
1.1 three-dimensional model of extrusion die
The cross section of the aluminum alloy extrusion impeller is as shown in fig. 1, the outer contour of the impeller is a molded line, the top of the lightening hole 1021 is an outer contour line which is inwardly deviated by 12mm along the normal direction, the bottom of the lightening hole 1021 is an arc line which takes the mass center of the section bar as the center of circle, and the sharp corner part is in rounded transition by R10.
The extrusion die is the reposition of redundant personnel mould (including reposition of
1.2 establishment of finite element model of extrusion die
And converting the three-dimensional model of the extrusion die into an stp format, introducing the stp format into Hyperxtrude software, trimming the existing geometric defects and properly simplifying non-critical parts. The aluminum blank area, the shunt hole area, the welding chamber area, the working belt area and the section area are sequentially arranged along the extrusion direction, the size of the grid unit is reduced progressively, the working belt area and the section area adopt triangular prism units, and the rest areas adopt tetrahedral units. And in view of the fact that the impeller section is of a symmetrical structure, a half model is taken for reducing calculation, simulation analysis is carried out, and a symmetrical plane condition is established for identification. The grid unit quality satisfies: an aspect ratio < 8; the unit minimum internal angle is >10 DEG, and the maximum internal angle is <170 DEG; jacobian > 0.22. Finite element modeling as shown in fig. 5, the number of meshes is approximately 38 ten thousand.
1.3 initial sizing height of the extrusion die
The initial die bearing height is shown in fig. 6. The extrusion area of the die core sizing belt 2013 is 5mm, and the extrusion area of the die hole sizing belt 3011 is 15 mm.
2. Analysis of numerical simulation results of extrusion die
2.1 flow velocity distribution at the outlet of the extrusion die and at the porthole
Fig. 7 is a flow velocity distribution of the aluminum billet in the Z direction (extrusion direction) at the die outlet section under steady state extrusion. The impeller profile at the die exit exhibits a generally decreasing stepped velocity profile in the radial direction from the impeller tip to the impeller root. The maximum velocity is at
And (3) calculating the mean square error of the velocity of the selected node by adopting the formula (2) to represent the uniformity of the velocity of the flow at the outlet section in view of the difference of the velocity of the flow at each position of the outlet section of the die. And selecting 8 nodes distributed in the stepped speed zone, wherein black dots in the figure 7 indicate positions of the selected nodes, and calculating to obtain a speed mean square deviation value of 0.356 at the position of the outlet section of the die. It can be seen that this value is small, which is related to the large thickness of the hollow impeller profile, which is still 12mm at the thinnest. The purpose of hollow impeller extrusion is to reduce or eliminate the amount of subsequent processing, and therefore it is necessary to balance the die exit velocities.
Wherein, SDV-flow mean square error;
vi-exit cross-section nodal flow velocities (mm/s);
n-number of selected nodes.
Fig. 8a, 8b and 8c respectively show the flow velocity distribution of the aluminum billet at the section of a flow dividing hole along the direction X, Y, Z. The 6 shunt holes 202 and the 3 hollow impellers are uniformly distributed, so that 2 shunt holes 202 and 1 hollow impeller are taken for analysis. The shunting holes 1 have obvious flowing trend along the X direction, the highest speed can reach 7mm/s (figure 8a), the shunting holes 2 have obvious flowing trend along the Y negative direction, and the highest speed can reach 5.7mm/s (figure 8 b). In the Z direction, the diversion holes 1 and 2 exhibit the same flow tendency, and the speed at the center of the diversion hole 202 can reach 13mm/s, while the speed at the edge of the diversion hole 202 is 0mm/s (fig. 8c), which is due to the severe friction adhesion phenomenon between the aluminum billet and the hole wall. The impeller I is formed mainly by the feed from the distribution holes 1, 2, and the root thickness is significantly thicker than other parts of the impeller, so the impeller is formed with a feed tendency from the top to the root, which is also one of the reasons for the stepped velocity distribution at the die outlet. Due to the existence of the stepped speed distribution at the outlet of the die, the defects of convex top and concave root of the impeller can be caused, and the speed distribution is improved by optimizing the bearing belt subsequently.
2.2 temperature field distribution during extrusion
Fig. 9 is a temperature profile from the area of the tap hole to the profile outlet. It can be seen that the temperature shows a tendency to rise first and then fall in the area of the tap hole, and the internal temperature is higher than the external temperature. This is because the outside of the tap hole 202 is in contact with the mold, and heat exchange occurs. A large amount of heat of deformation is generated upon splitting into strands of metal flow and flows relatively smoothly before welding, where the heat generated by friction is less than the heat dissipated by contact with the mold. The temperature from the weld chamber area to the profile exit shows a gradual rise and reaches a maximum temperature of 515.1 ℃ at the impeller root. The metal deformation of the bearing zone on the one hand generates heat and the impeller root on the other hand may rub more intensely, which is evidenced by the slowest velocity flow velocity at the impeller root at the exit cross-section.
3. Extrusion die bearing height optimization
Aiming at the stepped distribution of the flow velocity of the sectional material at the outlet of the die, the height of the sizing band 3011 of the die hole is gradually reduced from the top of the impeller to the root of the impeller. The height of the working belt at the top of the impeller is 15mm, and the height of the working belt at the root of the impeller is 5 mm. The heights of the die core sizing belts 2013 are consistent and are 5 mm. The specific values are shown in fig. 10.
Fig. 11 is the flow velocity distribution in the Z direction (extrusion direction) at the die exit cross section after optimization of the bearing height. It can be seen that the highest speed is at
4. Trial extrusion of aluminum alloy impeller
The die model shown in fig. 4 was machined from H13 die steel and the optimized bearing height distribution shown in fig. 10 was taken. The extrusion experiment is carried out at the extrusion speed of 5mm/s, the preheating temperature of the aluminum billet of 480 ℃ and the temperature of the die of 450 ℃, and the obtained aluminum alloy impeller section bar has smooth surface and does not have the defects of concave, warping and the like.
5. Conclusion
(1) By establishing a Roots blower impeller extrusion model, a stepped speed distribution with the speed decreasing from the top of the impeller to the root at the outlet of the mold is found; optimizing the bearing height reduces the velocity difference at the outlet, but does not change the trend of the stepped velocity profile.
(2) The roughness of the molded surface of the aluminum alloy impeller of the blower formed by extrusion is superior to (the size precision is close to or reaches) the traditional numerical control planing (milling) cast iron impeller, and the aluminum alloy impeller of the blower formed by extrusion can replace the traditional numerical control planing (milling) processing technology of the cast iron impeller of the Roots blower.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and those skilled in the art can make various modifications without departing from the spirit and scope of the present invention.
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