Theoretical And Experimental Investigations On The Drive And Control And Cooling Capacity Distribution Of The Two Stage Pulse Tube Cryocooler

The two-stage Stirling-type pulse tube cryocooler(SPTC), which can simultaneously provide two cooling temperature levels and cooling capacities, is in urgent need in the aerospace field for a wide range of applications. However, the research on the two-stage SPTC in our country is still inadequate, especially about the aspects of the cooling capacity distributions in the stages. Moreover, the drive under the DC power supply and the active temperature control of the two-stage SPTC also need the in-depth studies. The main contents and conclusions of this dissertation are given as follows.(1) The theoretical investigation is conducted on the drive and control of the two-stage SPTC under DC power supply. The mathematical control model is established, the expert PID control strategy is proposed and the corresponding simulation program is also developed. With the developed control circuit and algorithm, the simultaneous temperature control of two points can be achieved.(2) The relevant experiments are carried out to verify the above theoretical investigation. The printed circuit boards of the temperature signal collection and amplifier module, the H bridge power amplifier module and the signal process module are all designed, fabricated and tested. According to the modulation method of SPWM waveform and the proposed expert PID control method, the corresponding control programs are designed based on C language.(3) Theoretical and experimental investigations are conducted to study the effects of the drive voltage waveform on the cooling performance of SPTC. In the test range, the cooling performances under both trapezoid waveform and SWCTH waveform are better than that under the sine waveform. In addition, the test results of linear drive under DC power supply show that, the average energy converting efficiency of the developed drive and control system reaches 96.21%, and the cooling performance under the DC power supply is comparable with that under the AC power supply. Moreover, in the automatic temperature control test, the temperature stabilities achieve ±0.2 K@2 h without disturbance and ±0.3 K with disturbance, respectively.(4) Theoretical studies are conducted on the analysis and optimization model for the SPTC. A new ECA model including all the components is proposed to quantitatively analyze and optimize each component as well as the whole SPTC. In addition, theoretical investigations on the connecting position of the two cold fingers of the two-stgage SPTC are conducted, and the optimized connecting positions to achieve the highest cooling efficiency and the lowest cooling temperature are achieved, respectively.(5) Theoretical and experimental investigations are carried out on the optimal match between the linear compressor and pulse tube cold finger. The relations between them are systematically analyzed. The design method to achieve the optimal cold finger for the given linear compressor and the counterpart to achieve the optimal linear compressor for the given cold finger are proposed, respectively. A new in-line pulse tube cold finger and a new linear compressor are designed to match the given ones, respectively, and the experimental results agree well with the simulated ones. For the matched in-line cooler, at 80 K, the average motor efficiency reaches 81.5% and the cooling efficiency of Carnot achieves 17.2%. For the matched coaxial cooler, at 60 K, the corresponding values of 83% and 9.6% are achieved, respectively.(6) Both theoretical analyses and experimental verifications on the two-stage SPTC are conducted, and influences of key dimensional and operating parameters on the cooling performance and PV power distribution of each cold finger are also carried out. The motor efficiency achieves 82% by the optimization of the linear compressor to match with the two stage pulse tube cold finger. The experimental results indicate that, with the input electric power of 300 W, the cooling capacities of 2.5 W@85 K and 0.64 W@30 K can be achieved simultaneously, which verify the theoretical analyses about the distribution of PV power as well as the cooling capacity.