| Pulse tube refrigerator(PTR)has the advantages of long life,high reliability,small vibration and high efficiency,so it has become the most promising and most representative of a new generation of space cooling technology.The new generation PTR use the inertance tube and the reservoir as the phase shifter,the inertance tube and reservoir can use the resistance,inertia and capacitance of the oscillating flow to adjust the phase relationship between the pressure wave and velocity flow,which can meet the requirement of phase relationship at the warm end of the pulse tube and improve the efficiency of the PTR.Based on the thermoacoustic theory and the phase shift theory,this paper thesis studied the mechanism and system optimization method of the inertance tube of the Stirling pulse tube refrigerator,and the research work involved are as follow:1)Based on the thermoacoustic theory,a 1-D numerical model is established to compare the phase shift ability of single-segment and double-segment inertance tubeThe analyzation of energy flow and phase shift of the PTR shows the phase relationship of the inertance tube has an important effect on the performance of the PTR.In this thesis,a 1-D numerical model based on thermoacoustic theory is established,and the influence of inertance tube size and operating parameters on phase shift ability is obtained,the accuracy of the model is verified experimentally.According to the comparative study of single-segment inertance tubes and double-segment inertance tubes,the results showed that the double-segment inertance tubes can be used to increase the phase angle in the same conditions.2)The effect of the coiled type inertance tube and the high temperature inertance tube on the PTR is studied for the first time.Due to the limitation of 1-D design software can only be used to straighten the inertance tube for calculation,and considering the losses of the resistance caused by the coiled type inertance tube,so a 1-D DeltaEC and 3-D CFD coupling model of the inertance tube PTR is constructed.For the same structure parameter of the inertance tube,with the increase in the number of coiling turns,the cooling performance gradually decreased.The straight-line type inertance tube provides a 59.9 degree phase shift,which is larger than 56.5 degree,provided by the coiled type inertance tube,and the required PV power increase from 114.7 W to 123.5 W for the same 4 W@60 K.When considering the coiled resistance of the inertance tube,the input power is reduced by 4.6%by optimizing the inertance tube length,which is important for space efficient applications.A study of the operating characteristics of high temperature inertance tube is carried out.It shows that with the high cooling temperature and the large cooling capacity,the high temperature inertance tube can be used as the phase shifter,and the heat dissipation system can be simplified at the same time.When the temperature of the inertance tube increases from 293 K to 393 K,the phase angle of the inertance tube is slightly weakened and the PV power is increased.The total PV power increases from 85.2 W to 107.9 W for the setup with a cooling power of 30 W at 193 K,and the total PV power increases from90.3 W to 109.1 W for the setup with a cooling power of 40 W at 233 K.After optimizing the length of the inertance tube,the total input PV power can be reduced by approximately11.2%and 9.4%respectively.3)The effect of reservoir volume is studied,and a structure of a double cold-finger PTR with a common reservoir is proposedThe reservoir is conducive to the improvement of the performance of the PTR,but the larger reservoir volume is not conducive to the use of space-constrained applications.For single-stage PTR,when the operating parameters and structural dimensions of the inertance tube are settled,the phase angle of the inertance tube will be increased by increasing the reservoir volume,and the PV power first increases and then decreases.When the reservoir volume is too big,despite the increase of phase angle,the cooling performance is reduced due to the reduction of pressure ratio.By optimizing the inertance tube and reservoirs,a cooling power of 10 W at 70 K can be obtained with the input electric power of 216 W.The relative Carnot efficiency of IPTR is 14.75%.The double cold-finger PTR driving by a compressor can reduce the structure size and achieve the cooling effect at the two temperature zones at the same time.A common reservoir can further reduce the layout space of the PTR.After optimizing the inertance tubes of the two cold fingers,the effects of four kinds of common reservoir volumes(180cm~3,140 cm~3,100 cm~3 and 60 cm~3)on performance of the PTR are studied.It has been found that the cooling capacity can be improved by selecting different reservoir volumes when the cooling temperature and cooling capacity of the two cold fingers are different.4)The optimization of the phase shifters of different PTRs is carried outThe length of the two-segment inertance tube and reservoir volume of a PTR with a higher temperature zone and larger cooling capacity(50 W@170 K)is optimized,so that the total PV power is reduced from 204.8 W to 196.1 W and the performance of the refrigerator is improved while reducing the size of the structure of the phase shifter.For PTR operating at a high frequency(120 Hz),the inertance tube parameters are optimized as?1.5 mm×0.29 m+?2 mm×1.1 m with the reservoir volume of 50 cm~3.A cooling power of 1 W at 80 K can be obtained with input electric power of 40 W and the study on the coiled type inertance tube and the inertance tube with different materials is improved.The results show that the error of the input power at the same cooling capacity is small,which indicates that the effect of the resistance is decreased and the effect of frequency is enhanced after increasing the operating frequency.The optimal design of a two-stage PTR is improved.When the second stage input power is 70 W,a no load minimum cooling temperature of 22.04 K can be reached.When the input PV power of the first stage and the second stage is 140.2 W and 99.16 W,respectively,a cooling power of 10 W at 80 K and 1 W at 30 K can be achieved. |
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