Scroll compressor was created at the beginning of 1900s. Due to the limitation of processing technology, there are no product before the 1970s. Now the scroll compressor is the major compressor used by air conditioning. However, there are still many technology shortages of oil-free scroll compressor. I find it hard to get the right equations for calculation of oil free scroll compressor during me trial on designing a oil-free scroll compressor as my graduation thesis. Here, I want to share my experiences on oil-free scroll compressor. This result is a combination of books and research papers. I reconfigured each step in order to get a right result in shorter time.
This calculation method is suit for designing a compressor that you know the compressor displacement Qd (V3/min) and suction pressure ps as well as the exhaust pressure pd (MPa). And according to a Chinese paper “Choice of Bask Geometric Parameters and Structure Parameter,λ=h/Pt , on a Scroll Compressor” by Gu Zhaolin, published on “Compressor Technology”, 1996, we choose Pt、t and h as bask geometric parameters. So I modified the calculate steps to this method:
1. Calculate the indicated power of electromotor. Pi (Kw)
You can find this equation in document  at page 62. In this book, it use kgf/cm2 as unit of pressure. So I made a small change in order to change the pressure unit to IU MPa.
2. Compute motor power Pe (Kw)
The leakage and friction factors concerned, shaft power Pz can be counted through this equation:
Make sure there are about 5%～15% power reserve, the motor power Pe should be:
3. Select motor speed nw, it should be between 1000 and 4000r/min
4. Calculate the exhaust volume Vd (m3/r)
‘i’ in this equation is a parameter defined by the amount of compression chamber. If there is just one orbiting scroll and one fixed scroll, i should be 2. For compressor with Z orbiting scrolls and fixed scrolls, i should be 2*Z.
5. Calculate the suction volume Vs (m3/r)
Use a ideal gas model to simplify the calculation and assume the cycle as adiabatic. So:
k is the adiabatic exponent of working medium or refrigerant. The adiabatic exponent is 1.4. The suction volume can be defined:
6. Geometric interior volume specific ratio εv
7. Select scroll pitch Pt(mm), scroll width t (mm). t should be 2～6mm
8. The angle that the involute beginning α (rad)
9. The maximum angle of involute Φe(rad) and the exhaust angle θd(rad)
You will get the answer by combine the three equation. You may need tools like Matlab to get the result. https://www.zhangpeng.info/
10. Scroll height h (mm)
You should adjust your parameters to use unit of ‘m’ other than ‘mm’. But I defined all the distance use the unit of ‘mm’, so I plus a 1000000 to make the change.
11. Check λ=h/Pt if it appropriate
Some paper said λ should between 1.5 and 2.5. If the λ you gained exceed the limit, duplicate step 7-11.
12. Radius of basic circle Rb (mm)
13. Radius of shaft circle Ror (mm)
14. Balanced design of orbiting scroll.
15. Choose a oil-free format and the self-lubricatingmaterial
3、Gu Zhaolin, Yu Yongzhang. 涡旋压缩机设计计算研究[J].流体机械. 1996.2
4、Gu Zhaolin. Investigation of Scroll Compressor Design[J].低温工程. 1996.1
All these references are written in Chinese, you ask me if you have any question during reading these references.