Study on the disengagement angle and exhaust angle of the symmetrical arc plus linear correction type scroll compressor. Wu Wei Liu Xiangnong Wang Tiejun Liu Zhengshi (Hefei University of Technology, School of Mechanical and Automotive Engineering, Hefei 230009) is completely different. For the spindle angles in these two situations, due to the lack of complete and clear explanation, it is easy to generate large errors when calculating the volume of each compression chamber of the scroll compressor. In this regard, by studying the geometrical characteristics of the starting line of the scroll of the scroll compressor using the symmetrical arc plus straight line, the disengagement angle and the actual exhaust angle are defined, and the difference between the two is clarified, and the disengagement is deduced in detail. The angle calculation formula analyzes the factors affecting the disengagement angle, and according to the essential feature of the reduction of the volume of the central compression chamber after the correction of the thickness of the starting end of the scroll, provides the corrected volume of the initial thickness of the scroll and the actual exhaust angle. Calculation method. The calculation example proves that the disengagement angle differs greatly from the actual exhaust angle, and points out that the actual exhaust angle will affect the design of the vent hole.

The closed scroll compressor for the traditional automotive air conditioner and the closed scroll compressor for the electric vehicle air conditioner use a symmetrical arc plus straight line (EA-SAL) to correct the beginning of the scroll, increasing the exhaust angle and improving the compression. The internal volume ratio and compression ratio of the machine improve the cutting force characteristics at the beginning of the scroll to meet the special requirements of automotive air conditioning conditions, working fluid requirements and installation space restrictions. The venting process of the symmetrical arc plus linear correction type scroll compressor, especially the determination of the exhaust angle, is particularly important in the correction design calculation of the scroll compressor. The main manufacturer of foreign automotive air-conditioning compressors, Japan's Sanpower and Denso Co., Ltd., have produced such a tooth-shaped scroll compressor, but the relevant research results have not been publicly published so far. Domestic scholars have also studied the exhaust process and exhaust angle of the modified line scroll compressor. Liu Tao et al. analyzed the starting exhaust angle when the double arc was corrected. Gao Xiufeng et al. simply analyzed the determination of the exhaust angle of the scroll compressor with the exhaust valve, and pointed out that the calculation formula of the volume after the correction of the starting end of the scroll is more complicated; when calculating the working volume of the compressor, the exhaust process is divided. It is the involute engagement phase and the modified partial engagement phase. By studying the exhaust process of the modified line compressor, Yan Linfang proposed the principle that the vent design should follow, and pointed out that it is necessary to correct the current exhaust and power calculation angles. In the case of the symmetrical circular arc plus straight line correction, the exhaust angle is equivalent to the angle at which the main shaft rotates when the dynamic and fixed scrolls are disengaged from each other, which does not truly reflect the exhaust condition, resulting in a larger calculation when calculating the volume of each compression chamber. Error; in particular, there is no calculation method for the volume of the central compression chamber, and this is related to the symmetry arc plus linear correction type of the scroll compressor. The disengagement angle and the exhaust angle are studied. 2 The disengagement angle 2.1 The spindle rotation angle bookmark2 will be relatively static. When the scroll is installed at 180°, the spindle rotation angle is defined as 0=0, that is, the positive angle of the base line of the static scroll is 0, and then the positive scroll is centered at the center of the rotor. The angle at which the center of the scroll base is rotated is the spindle angle 0 as shown.

Dynamic analysis and calculation of scroll compressors. Here, the geometric characteristics of the starting end of the vortex disk of the symmetrical arc plus linear correction type scroll compressor are deeply analyzed, and the angle of the spindle rotation when the central compression chamber is formed and the angle of the spindle rotation when the compressor is exhausted are strictly defined. The disengagement angle and the actual exhaust angle are derived. The calculation formula of the disengagement angle is deduced in detail, and the factors affecting the size of the disengagement angle are analyzed. The reduction of the volume of the central compression chamber after correction is actually due to the essential characteristics of the increase of the wall thickness at the beginning of the scroll. The calculation method of the volume of the increased thickness of the starting end of the scroll is proposed to calculate the volume of the central compression chamber and the actual exhaust. Angle size. These are important for accurately calculating the volume of each compression chamber, especially the central compression chamber volume, dynamic analysis and design calculations.

1 Symmetrical arc plus straight line correction parameters As shown, the scroll body adopts an involute profile, and the basic geometric parameters are: the base circle radius is rb, and the scroll pitch is the wall thickness of the eight scrolls (from the involute line) The starting angle is the involute angle. The starting end of the scroll adopts the symmetrical arc plus the straight line correction, the correction angle is the point of the heart d is the intersection point of the modified arc and the involute of the inner wall of the scroll, and the 6 points are the connecting arc and the outer wall of the scroll. The line intersection point is the correction line, and the correction arc and the connection arc 5々 are respectively tangent to the M and N points. The connection arc radius is r, and the correction arc radius is a few correction arc center 2' and the base circle is cut. The point C distance is 2.2. The angle between the arc and the straight line correction method is generally defined. When the secondary compression chamber is connected to the central cavity, the spindle rotation angle is defined as the exhaust angle. In fact, due to the compression, the internal volume is relatively small, and the internal pressure is The ratio is also small, and the external pressure ratio has not been reached (the external pressure ratio is close to 6 in the case of automobile air conditioning, and the internal pressure ratio is only 34). Obviously, although the secondary compression chamber is connected to the central cavity, However, it is not possible to discharge the refrigerant gas. The exhaust angle does not reflect the actual exhaust condition inside the scroll compressor, so this definition is not reasonable. It is also proposed that the main shaft angle is defined as the disengagement angle when the secondary compression chamber is connected to the central compression chamber, and the vortex is defined. When the outermost part of the rotating body is closed, the spindle rotation angle is 0=0, which is not convenient for calculating the volume of each compression chamber. Here, when the central compression chamber is connected with the secondary compression chamber, the moving scroll and the straight portion of the fixed scroll tooth end are disengaged from each other. The angle at which the disk rotates relative to the fixed scroll (ie, the angle at which the spindle rotates) is defined as the angle of disengagement, denoted as 0, and the spindle is defined as 0=0 when the movable scroll is mounted at 180° with respect to the fixed scroll. The positive scroll center line 00' and the X-axis positive angle are 0, as shown.

Then, from the initial position, the center of the base of the movable scroll is located on the horizontal line of the center of the base of the over-spindle, and '=P (slewing radius). When the position is turned to this position, since the straight stomach is the correction arc and the connecting arc The public cut is straight line 0//stomach, then A:actg―-MV is the corrected straight line length.

Substituting the formulas (2), (3), and (4) into the formula (1), it can be seen that r, R, and d are related to the basic geometric parameters, the correction angle, and the offset Ar of the involute scroll.

The length is also related to the basic geometric parameters of the involute scroll, the correction angle A, and the offset Ar.

Therefore, when the geometric parameters of the involute vortex are determined, it is obtained by the formula (5) that the detachment angle 0 is related to the correction angle and the offset amount Ar, and the subsequent change relationship is as shown.

3 The actual exhaust angle center compression chamber communicates with the secondary compression chamber. Since the pressure does not reach the exhaust pressure, the refrigerant gas continues to be compressed in the central compression chamber until the exhaust pressure is reached. At this time, the rotation angle of the spindle is defined as actual. The exhaust angle is recorded as chemical.

3.1 After the central compression chamber volume is corrected by the symmetrical arc plus the straight line, the calculation of the central compression chamber volume of the scroll compressor is cumbersome, and has not been clarified. Gao Xiufeng et al. gave a calculation method for the closed working chamber volume in the correction part of the exhaust process. However, when the actual exhaust starts, the projected area S of the central compression chamber is as shown, and the correction parts fail to mesh with each other. Therefore, the formula cannot be applied to the calculation of the central cavity volume during actual exhaust. In view of the fact that the volume of the central compression chamber is formed by the involute scroll wall and the end face of the dynamic and fixed scroll when uncorrected, and is easy to calculate, if the volume of the increased thickness of the starting end of the scroll is compared with the uncorrected, the center compression is calculated. The cavity volume is also symmetrical circular arc plus linear correction type linear scroll compressor disengagement angle and exhaust angle study is easy to calculate.

After the correction, the volume of the increase in the wall thickness at the beginning is studied through the geometrical characteristics of the central compression chamber. It is found that the corrected projection area increases due to the increase of the wall thickness at the beginning of the correction. The increase can be used in the sense (smart representation: enclosure area, sector 2 'like area, triangle like D' area, sectoral ODF area, triangle DOD' area, triangle 0C02' area, sector area.

The area enclosed, the fan-shaped i'NS area, the triangle Oi'ND' area, the triangle C'i' area, the sector OC'D' area, and the area of ​​the involute inner wall from the starting point £ to the G surrounding.

The volume that increases after the correction due to the increase in wall thickness: v'=s'(e)xh(17) The increased volume of this portion directly results in a decrease in the volume of the central compression chamber.

Compared with the projected area of ​​the central compression cavity when uncorrected, after the symmetrical arc plus the straight line correction, the projected area S of the central compression cavity can be calculated by the following formula:

According to the derived linear equation, the above areas can be solved. Therefore, it is known that the basic parameters of the scroll are eight walls thick, the height A, and the number of vortex m, the central compression chamber volume: 3.2 the actual exhaust angle is calculated by calculating the actual exhaust angle, and the external pressure ratio can be utilized. Push it. According to the air conditioning conditions of the car, it is easy to know the compressor discharge pressure and the suction pressure 夂. Then, the volumetric ratio of the suction volume of the scroll compressor v = ("h / ie: let 0 =, substituted (22), can be solved by the numerical solution.

3.3 Calculation example height 14mm, three pairs of compression chamber, symmetrical arc plus straight line correction, correction angle is 1.908rad, under the condition of automobile air conditioning, refrigerant R134a, exhaust pressure 1804kPa, suction pressure 293kPa, the calculation result is: inner volume The ratio is V1=2.744, the internal pressure ratio is e1=3.035, the disengagement angle 俨=4.744rad, and the actual exhaust angle is 0d=6.368rad. That is, when the main shaft rotates through 272°, the straight line of the fixed and fixed scrolls is disengaged from each other, and the secondary compression chamber is The central compression chamber is connected; when the main shaft rotates 365°, the pressure of the refrigerant gas in the central compression chamber reaches the external pressure ratio (e=6.16), and the exhaust starts. Obviously, there is a considerable difference between the disengagement angle and the actual vent angle.

4 Conclusions In the EA-SAL modified wrap method, the disengagement angle is the key parameter for calculating the volume of each compression chamber. Here, the disengagement angle is defined and the calculation formula of the disengagement angle is deduced in detail, and the influence of the disengagement angle is analyzed. factor.

The calculation method of the volume increase at the beginning of the scroll after the EA-SAL correction is proposed, which provides a basis for the calculation and dynamic analysis of the central compression chamber volume.

The actual exhaust angle is accurately defined, and the actual exhaust angle is derived using the external pressure ratio. The calculation of the difference between the disengagement angle and the actual exhaust angle is very large.

Due to the delay of the actual exhaust process, the volume of the central compression chamber continues to decrease, which not only increases the internal volume ratio, but also affects the leakage caused by the pressure difference between two adjacent compression chambers, and the central compression chamber after the dynamic and static scroll disengagement The heat transfer characteristics in the actual capacity reduction compression process, the flow resistance and the work loss of the working fluid at the beginning and end of the exhaust, these factors affect the design of the exhaust orifice, and the relevant content needs further discussion.

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