1 selection of characteristic parameters
The shape of the scroll compressor is complex and it requires three independent parameters. In order to make the representation image intuitive and easy to detect, the height h, the pitch p and the thickness t of the profile line are generally selected as independent parameters. Considering the correlation between the pitch p and the wall thickness t, the groove width B is used instead of the pitch p, and h, B, and t are selected as independent parameters.
Since each compressor is associated with a certain stroke volume, in order to find a uniform reference amount in relation to the stroke volume, the concept of the equivalent cylinder bore of the scroll compressor is introduced here. The equivalent cylinder diameter of the scroll compressor is defined as the cylinder diameter of the reciprocating compressor with the stroke volume of the scroll compressor as the volume and the stroke height of the scroll compressor.
D v = 4 V h 1 2
Where: D v is the equivalent cylinder diameter; V h is the stroke volume.
This can introduce the following three coefficients: the tooth height coefficient h = h / D v
Groove width factor
B = B/ D v = (p - t ) / D v
Tooth thickness coefficient
t = t/ D v
2 relationship between characteristic parameters and structural parameters
Under the condition that the stroke volume V h of the scroll compressor and the three characteristic parameters h, B, t are known, all the structural parameters of the profile can be determined (see the literature for the specific derivation process): equivalent bore diameter
Profile height
Profile thickness
Line groove width
Compression chamber logarithm N = 1/ 8 type line pitch
Radius of gyration
Base circle radius
Involute start angle
When the tooth thickness coefficients are 0 04, 0 05, and 0 06, the relationship between the logarithm of the compression cavity and the groove width coefficient. It can be seen that the groove width coefficient plays a decisive role in the logarithm of the compression cavity. As the groove width coefficient increases, the logarithm of the compression cavity decreases. The tooth thickness coefficient has less influence on the logarithm of the compression cavity, with the tooth thickness coefficient. Increase, the compression chamber logarithm increases slightly.
3The influence of characteristic parameters on the dynamic performance of the compressor
In the moving parts of the scroll compressor, we are more concerned about the force of the moving scroll and the crankshaft. Wherein: the force acting on the movable scroll mainly includes the axial gas force Fa, the tangential gas force Ft and the rotational inertia force Fc of the movable scroll; the force acting on the crankshaft is mainly the driving force Fp and the main bearing force Fm and auxiliary bearing force Fs. See the literature for a kinetic model of a scroll compressor.
3. 1 tooth height coefficient
As the tooth height factor increases, the profile height increases and the profile quality increases. Since the stroke volume is constant, the maximum radius of the profile is reduced, and the outer diameter of the orbiting scroll and the quality of the moving plate bottom plate are also reduced. Since the outer diameter of the moving plate is large and the quality of the profile line is linearly related to the increase of the profile height, the mass of the moving plate bottom plate is quadratic with the decrease of the outer diameter of the movable scroll, so the rotation of the movable scroll The inertial force is reduced.
Similarly, as the tooth height coefficient increases, it is known that the groove width and the wall thickness of the profile line are reduced, so that the high pressure gas action area is reduced, and thus the axial gas force is also reduced.
Since the height of the profile is proportional to 23h, and the groove width and wall thickness are both proportional to 13h, the gas action area increases, so the tangential gas force increases slightly as the tooth height coefficient increases.
The tooth height coefficient is increased from 0 3 to 0 6, the driving bearing force is reduced by about 25%, the main bearing force is increased by 17%, and the auxiliary bearing force is kept substantially unchanged.
3. 2 slot width factor
As the groove width coefficient increases, the groove width increases, and the compression chamber logarithm decreases, so that the outer diameter of the movable scroll changes little, and thus the rotational inertia force of the movable scroll is substantially unchanged.
When the groove width factor is increased from 0 21 to 0 23, the logarithm of the compression cavity is reduced from 3 5 to 30, and the length of the profile line is reduced faster. Although the groove width is increased, the axial gas action area is still Reduced, and thus the axial gas force is decreasing. When the groove width coefficient increases from 0 23 to 0 25, the groove width increases, the compression chamber logarithm decreases from 30 to 25. The profile length decreases relatively slowly, and the axial gas action area does not change much. Therefore, the axial gas force is substantially unchanged.
As the linearity of the groove width coefficient increases, the tangential gas action area increases linearly, so the tangential gas force also increases linearly and the slope is large. When the groove width factor increases from 0 21 to 0 25 , the tangential gas force increases by about 115%.
When the tooth height coefficient increases from 0 21 to 0 25, the driving bearing force increases by about 27%, the main bearing force increases by about 102%, and the auxiliary bearing force increases by about 80%.
3. 3 tooth thickness coefficient
With the increase of the tooth thickness coefficient, the thickness of the profile increases, and the logarithm of the compression cavity increases slightly, which makes the outer diameter of the movable scroll and the quality of the profile increase, which greatly increases the area of ​​the bearing gas and increases the area of ​​the tangential gas. Not large, so the rotational inertia force and axial gas force of the orbiting scroll grows rapidly and the tangential gas force grows slowly.
The tooth thickness coefficient increases from 0 03 to 0 07, the drive bearing force increases by about 23%, the main bearing force increases by about 42%, and the auxiliary bearing force increases by about 40%.
In summary, the following points are obtained.
(1) The axial gas force and the rotational inertia force of the moving disk have similar trends with the characteristic parameters. They decrease rapidly as the tooth height factor increases, and are less affected by the groove width factor.
(2) The tangential gas force increases with the increase of the characteristic parameters and has a linear relationship, which is most affected by the groove width coefficient, the tooth height coefficient is second, and the tooth thickness coefficient is the smallest.
(3) The influence of the tooth height coefficient on the bearing force is mainly achieved by changing the rotational inertia force and the tangential gas force of the moving disk, and the size of their force arms. When the tooth height coefficient is too large, the overturning moment acting on the moving plate is too large, the dynamic plate will be unstable, and the spindle bearing force is too large, the friction power consumption is large; when the tooth height coefficient is too small, the compressor volume Too big. Therefore, the tooth height coefficient should generally be selected within the range of 0 42 0 52.
(4) The groove width factor has the greatest influence on the bearing force. Considering that the pressure of the general compressor is relatively high, it is necessary to have a sufficient number of compression chambers.
When the groove width coefficient is too large, the bearing force is too large, and the frictional power consumption is large; if the groove width coefficient is too small, the number of compression chamber pairs is too large, resulting in a compressor volume being too large. Therefore, the groove width factor should generally be selected within the range of 0 21 0 24 .
(5) The tooth thickness coefficient has a great influence on the bearing force. As the tooth thickness coefficient increases, the forces increase. Generally, in the range of the guaranteed line strength, the tooth thickness coefficient should be taken as small as possible, and should generally be selected within the range of 0 04 0 6 .
4 preferred strategies for characteristic parameters
In engineering design, the suction and exhaust pressures and stroke volume of the working fluid are generally given or calculated by simple calculation. If there is no special requirement, the speed is synchronous. Thus, under different design conditions, the feature parameters should be selected within a given range. Generally speaking, the sensitivity of the three coefficients to the pressure ratio is B, h, and t, and the sensitivity to the displacement is h, B, and t. As the pressure increases, B should decrease, h also Decrease, t should be increased appropriately; as the displacement increases, h should increase, B also increases, and t should be appropriately reduced.
In the specific choice, the choice of h is mainly determined by the amount of exhaust, the choice of B is mainly determined by the pressure ratio, and the choice of t is to take a small value as much as possible under the condition of the strength of the guaranteed line. A preferred strategy for the variation of characteristic parameters with pressure ratio and displacement.
5 Conclusion
(1) The concept of equivalent cylinder bore of scroll compressor is proposed. The height, groove width and thickness of the profile are transformed into three independent dimensionless characteristic parameters by using the equivalent bore diameter. The characteristic parameters and profile structure are given. The mathematical relationship of the parameters.
(2) The influence of characteristic parameters on the dynamic performance of the compressor is analyzed in detail. The preferred range of characteristic parameters is 0 42 h 0 52 0 21 B 0 24 0 04 t 0 06(3) The pressure ratio and displacement are analyzed. For the influence of characteristic parameters, the preferred strategy of characteristic parameters under different design conditions is given.
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