An experimental procedure was designed to measure the dynamic axial clearance in a scroll air compressor with water injection by using a eddy current displacement sensor. To protect the eddy current sensor probe

the sensor was mounted with an offset installation method. The data acquisition system was programmed to record and save the experimental data. The experimental results show that the axial clearance varies with the rotational speed of the compressor and the typical value of axial clearance at low and high speed is 75 μm and 49 μm

respectively. The axial clearance in the scroll air compressor is larger than that in the refrigeration scroll compressor. In addition

the frequencies of signal pulse can reflect the change of rotational speed on the basis of the output voltage signals. A new method that could accurately measure the rotary speed of scroll compressors was proposed.