Principle Study And Experimental Investigation Of Gas Waves Refrigeration By Aggregated Thermal Dissipation

There is a huge waste of pressure energy in natural gas processing and transport area by using throttling refrigeration process. Based on the unsteady flow theory, high efficiency wave equipments such as gas wave machines have huge advance in such processes. Many practical applications of gas wave machines in domestic oilfield show that when operating under high pressure and large expansion ratio conditions these machines have the problems of vibration induced by pulsing gases and refrigeration performance reduction by liquid accumulation, which adversely affect the operation stability and reliability. The main reason is that the rest gases in the unilateral closed pulse tubes cannot empty intirely, and the long pulse tubes vibrate with small stiffness. Bilateral opened pulse tube rotors used for superchargers and gas engines formerly has double sided open structures, which has no problem of vibration or liquid accumulation. At the time being, how to use wave rotor in expansion refrigeration area is a novel project.A study on the flows and refrigeration principles of bilateral opened pulse tube has made in this dissertation. It is of great importance for enrichment and improvement of gaswave refrigeration theory. This research has presented a detailed implementation of technology of gaswave refrigeration from aspects of gas dynamics analysis, thermodynamic analysis and experimental evaluation and validation.(1) The unsteady flow and gasdynamic wave's propergation properties has studied in detail. In addition, the thermal separation effects in rotor passages have explored. Used for processing of high-pressure natural gases, wave refrigerators often operate in the nonideal thermodynamic regions. A real gas dynamic computational fluid dynamic (CFD) model coupled with equations of state like AGA8, BWRS, etc has established for discussing the flow patterns of of unsteady flows, which can calculate the flow of low heat capacity natural gases located in vicinites of gas-liquid equilibrium line. Based on this, the origination, reflection and refraction rules of various arbitrary gasdynamic waves in rotor passages have explored. The influence of real gas effect on offset-design of the refrigerators has acquired. A corrected wave diagram based on real gas models has ascertained which has laid a theoretical foundation of performance assessments and designs of wave rotor refrigerator.Based on the above studies, a novel novel refrigerator named Aggregated Thermal Dissipation Gas Wave Refrigerator (AWR) has proposed. The AWR now has the Chinese Patent (CN200810011257.1). Design scheme based on method of characteristics for key structure parameters matching condition like port timing layout has worked out.Taking real gas effect into account, area design method of high-pressure port has realized.(2) A novel thermodynamic analytical model for AWR has established based on the following assumptions:there is no mass transfer across contact face, which separates the inner whole process into expansion process of driving gases with compression one of driven gases; the two streams directly exchanger energy though volume work. This performance assessment model shows the main contributing factors of inner thermal processes. Studies on main factors of expansion and compression processes have indicates that when expansion ratio bellows 10, the inner non-isentropic characteristics of shockwaves are nonsignificant while other factors such as non-uniform mixing in ports and leakages (including mass transfers of driving and driven streams) are of concernment.(3)Comparison evaluations of numerical discrete schemes for control equations show that the density based model with AUSM series schemes and appropriate limiters to discrete advection items, center difference schemes to discrete vicious items and dual-time step scheme to discrete unsteady items is applicable to full speed interior flows of real gases in wave rotors. Mono-pipe and multi-pipe numerical model and initial-boundary conditions have been set up to simulate the flows and port timing analysis of AWR. Particular reasons and solutions of shockwave and contact face distortions has indicated that short opening time and wide high pressure port will get higher refrigeration performance. Moreover, experimental results have verified that wide high-pressure (HP) port and appropriate incidence angle can improve about five percents of expansion efficiency relatively, with higher compression efficiency at the same time.(4)A dry-air refrigeration test rig of AWR with expansion ratio less than 10 and a fluidic test rig less than 3 have built. A number of experiments on axial-flow AWR prototypes by adjusting temperature and pressure of high temperature (HT) port and pressure of low temperature (LT) port has performed to get thermal states of other ports. Relations of exchanging work, supercharging and refrigerating performances and circulation flux ratio show that expansion efficiency are affected by mass transfer (mainly gas mixing and leakages) and energy exchange (losses from mass transfer and non-uniformity flows in ports) between driving and driven flows. The following conclusions from laboratory studies are fruitful: location of HT port has important influence on the refrigeration performance, and a reflected shockwave compression process may not feasible for rotors used for refrigeration.In lab, the isentropic efficiency of AWR now can get 69%. Actual liquid experiments show that AWRs have excellent fluidic operation performance:the refrigeration properity remains almost unchanged even if AWR operates with 7% liquid ratio.