Study On Phase Characteristics And Measuring Methods Of Inertance Tube In Pulse Tube Cryocooler

The pulse tube cryocooler(PTC)is a kind of cryogenic refrigerator which is widely used in many fields with features such as absence of moving parts at the cold end,high reliability at low temperature,strong ability in resisting electromagnetic interference,low vibration,and long life-time.The development history of PTC has experienced different phases from the basic-type,the small orifice-type,the double-inlet type and the inertance-type,which is essentially the development of phase adjustment component.At present,the inertance tube has become the major method in high-frequency PTC for it's simple structure and strong ability in adjusting phase angle.However,there is a coupling relationship between the phase angle and the acoustic power at the inlet of the inertance tube that should be considered.The phase angle of the inertance tube is quite different under different acoustic power.At the same time,the real-time measurement of the phase adjustment characteristics is quite lacking.Therefore,based on a high-power Stirling PTC,the phase characteristics of the inertance tube has been studied theoretically and experimentally.The major work is as follows,1.The inertance tubes are classified according to the different acoustic powers and different phase angles.Based on the simulation results of characteristics of different lengths and inner diameters of inertance tube,the classification criterion for high acoustic power inertance tube and low acoustic power inertance tube is given in this paper.It's found that the phase adjustment capability of high-power inertance tube is significantly higher than that of the low-power inertance tube,and it needs to be weakened.In addition,the simulation results and the measured data of the high power inertance tube are more accurate.2.The parallel inertance tubes structure is adopted to simplify the matching between phase angle and inlet acoustic power.It is usually difficult for the single inertance tube to meet the requirements of the acoustic power and the phase angle at the inlet of the inertance tube at the same time.When two inertance tubes with different phase adjustment capability are connected in parallel,the phasing ability of the phase adjustment structure can be dynamically adjusted by changing the opening of the valve.The structure of parallel inertance tubes can ease the excessive phase adjustment in the high-power inertance tube and reduce the temperature rise of the inertance tube.3.A method using the data measured by the pressure sensors is proposed to calculate the phase angle and the acoustic power at the inlet of the inertance tube.The phase difference of the pressure wave between the inlet and the outlet of the inertance tube and pressure amplitude in the reservoir are directly measured by pressure sensors,then the phase difference of the mass flow is calibrated.Finally,the phase angle and the acoustic power at the inlet of the inertance tube are obtained.This method doesn't need to measure the mass flow and can reduce the impact of the measurement system on the flow field.4.The high power Stirling-type PTC is used as the experimental platform to study the phase characteristics of the inertance tube.The simulation results of the DeltaEC on the phase angle and the acoustic power at the inlet of the inertance tube are verified by the experiments.The parallel inertance tubes were built in this paper and their performance were tested and compared with the single inertance tube.Experiments show that the PTC with parallel inertance tubes can achieve better performance than the single inertance tube with the same cross-sectional area.