Measured reed valve dynamics of diaphragm pumps with laser Doppler vibrometer

Pressure controlled reed valves are widely used in compressor technology to control the in- and outflow of the compression chamber. The valves significantly influence efficiency, performance and reliability of a compressor. While the dynamic behavior of reed valves is well investigated in some disciplines such as compressors for domestic refrigeration, little is known about the reed valve dynamics of small vacuum pumps like diaphragm pumps. In this work, a novel test-rig for high-resolution valve motion measurements of small oil-free diaphragm pumps is developed, providing for the first time a detailed insight into the suction and discharge valve dynamics of this type of vacuum pumps. The valve motion is measured using a laser Doppler vibrometer (LDV), which has already proven to be a very efficient method in the field of compressors for domestic refrigeration. In addition to the valve motion, the measurement concept also includes measurement of the motor shaft position and speed, as well as flow rate, pressure and temperature measurements for complete recording of the operating conditions. Measurements were performed at three different motor speeds and various operating conditions in vacuum and pressure application. The obtained results allow a detailed comparison of valve behavior over a wide range of operating conditions and can be used to derive measures to further improve the vacuum pump performance.