Calculation of oil free scroll compressor

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)

Scroll 1

You can find this equation in document [2] 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:Scroll 2

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)


pi=3.1415926535 897932

9. The maximum angle of involute Φe(rad) and the exhaust angle θd(rad)


Scroll 3

Scroll 4

You will get the answer by combine the three equation. You may need tools like Matlab to get the  result. http://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


1、刘振国.涡旋式流体机械与涡旋压缩机[M].机械工业出版社. 2009

2、编写组.活塞式压缩机设计[M].机械工业出版社. 1974

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.

8 thoughts
  1. 有没有各种无油压缩机的比较之类的论文,

    1. @long: 这样吧,我做论文时用到的论文我电脑里面都删除了,都传到这了 http://www.docin.com/mydoc-362835-1.html&folderId=48718 可以免费查看,看中哪篇之后再告诉我,我传给你吧。。

  2. Dear sir,
    I am Ajay from India working in auto airconditioning. I have to design a Scroll Compressor. So i need your help in designiong the Scroll compressor. If u have any information regading the Scroll Compressor design pls, send me to my email. Also i want to purchase Scroll Compressor book and papers. I am ready to pay the money for book and the design related papers. First time i am designing the Scroll Compressor.So please help me from the starting of Scroll Compressor design.Sir its very urgent.

    From – India

    1. Hello Ajay
      Glad to see your comments on my blog. This article is a part of my Graduation Thesis. However, you know I’m a Chinese man, I did most of my job in Chinese. As I did this project more than a half year ago, I just find three English Scroll Compressor papers. I’ll send them to you later.
      I’m now working in SGM(General Motors China Branch) as a compressor engineering. So, you can ask me for some questions.I’ll try to help you anyway. I also have some confidential documents from my company. So, some information in those documents may help you on some degree.

  3. Hi Aaron
    thanks for reply of my comments. I am working in Subros Ltd, India. Pls, you send me those English Scroll Compressor papers to my email. pls give me your email id so that i can asked you to some questions related to scroll Compressor design.
    My email id: ajaychoudhary8@gmail.com


  4. @Ajay Kumar Choudhary: Didn’t you receive my email? I have send three English thesis to you.I can re-sent it to you if you didn’t get it.

    You can contact me via zp1214@gmail.com

    I’ll carefully check some of my company’s documents in order to decide if I can sent them to you.


  5. Hello,

    I’m working in my thesis too about a new compressor and I’ve found this website and I think it is really helpfully, do you have more information about it?
    I read you are working on it and you have more information, could you share it with me?

    And also I would like to find a job in China, country which I love and perhaps you also can give me some advices about it.

    Thank you so much for everything.

    Grettings from Denmark 🙂

  6. @Bego: Thanks for your reply.
    I don’t know how to help you as I don’t know exactly what you want. You can ask me everything and I’ll try my best to answer you.
    I’m also glad you like China. I’m now working for GM China as a compressor engineer. I can recommend you to our company if you like. Or have you get any idea about job in China?

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