中文用户可以查看中文版：无油润滑涡旋压缩机设计计算步骤

Disclaimer:

This calculation method is suit for designing a compressor that you know the compressor displacement Q_d (V³/min) and suction pressure p_s as well as the exhaust pressure p_d (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. P_i (Kw)

equation for calculating the indicated power of electromotor

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 P_e (Kw)

The leakage and friction factors concerned, shaft power Pz can be counted through this equation:

P_z=1.12P_e

Make sure there are about 5%～15% power reserve, the motor power Pe should be:

P_e=(1.05～1.15)P_z

3. Select motor speed n_w, it should be between 1000 and 4000r/min

4. Calculate the exhaust volume V_d (m³/r)

V_d=Q_d/(i*nw)

‘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 V_s (m³/r)

Use a ideal gas model to simplify the calculation and assume the cycle as adiabatic. So:

pV^k=C

k is the adiabatic exponent of working medium or refrigerant. The adiabatic exponent is 1.4. The suction volume can be defined:

equation for calculating the suction volume of scroll compressor

6. Geometric interior volume specific ratio ε_v

ε_v=V_s/V_d

7. Select  scroll pitch P_t(mm), scroll width t (mm). t should be 2～6mm

8. The angle that the involute beginning α (rad)

α=pi*t/P_t

pi=3.1415926535 897932

9. The maximum angle of involute Φ_e(rad) and the exhaust angle θ_d(rad)

ε_v=(2*Φ_e-3pi)/[2(Φ_e-θ_d)-3pi]

equation 1 for calculating the maximum angle of involute Φe and the exhaust angle θd

equation 2 for calculating the maximum angle of involute Φe and the exhaust angle θd

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)

V_s*1000000=P_t(P_t/2-t)h(2Φ_e-3pi)

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/P_t 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 R_b (mm)

R_b=P_t/2pi

13. Radius of shaft circle R_or (mm)

R_or=(P_t-2t)/2

14. Balanced design of orbiting scroll.

15. Choose a oil-free format and the self-lubricatingmaterial

References:

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.

This is just a simple example of thermocouple:

In this figure, A and B are two different metal. When the temperature is different between 1 and 2, there will appear electric current. www.zhangpeng.info

Now we offten use sheathed thermocouple in industry field. These thermocouples is just put two kinds of metal in one pipe.

Zhangpeng have a idea to make new type of thermocouple. We just use the pipe to act as one metal and put the other metal in it then fill out the gap with MgO to insulate. If this idea come true, the thermocouple can be smaller.

This is my idea to make new type of themocouple. There are some problems. I think how to make it stable and live long it most important.