| In supercritical compressed air energy storage(SC-CAES)system,LNG liquefaction and air separation system,traditional throttle valves are widly used in the depression process of high-pressure cryogenic liquid.Due to the isoenthalphy process,mass of energy is lost accompanied with fierce vaporization.The liquid expander can recover some of the wasted energy,reduce the gas precipitation,and suppress the temperature rise.If throttle valves are repalced with liquid epxpander,the efficency of original system could be improved.The liquid expander is a kind of highly customized machinery,which has high performance test cost and is faced with cryogenic cavitation.At present,there are few research on liquid expanders and high performance.The demand of high performance liquid expanders in SC-CAES is increasingly urgent,therefore it is of critical importance to carry out detailed research on the liquid expander.In this paper,principles and research progresses of various liquid expanders are reviewed,and the design and experiment of turbo liquid expander are studied in several aspects.The main research contents are as follows.1.Research on the design and modeling of the liquid expander.The flow process of liquid expander is analyzed,the design model of liquid expander was established,and the influence of design parameters on the liquid expander was studied.A liquid expander was designed according to the SC-CAES system.Then,in order to simplify the experiment,the model test method of liquid expanders was proposed,and model liquid expanders were given.Finally,performance curves of the design and model liquid expanders were obtained by numerical simulation,and the reliability of the design method and the modeling method was verified by comparing with simuation results with design values.2.Research experimentally on the liquid expander.An experiment scheme for testing liquid expanders was put forward,and valutes of operation parameters were verified by numerical simulation.The experimental platform for testing liquid expanders was built based on the scheme and parameters.Based on the designed liquid expander,a liquid expander was manufactured and the full performance test of the designed liquid expander was carried out by using the experimental platform.Under the rated condition,the efficiency is 75.16%and the output power is 30.44 kW.3.Research on internal flow of liquid expanders.Three kinds of computational domains of liquid expanders were numerically calculated,including CASE1(containing single passages of the nozzle and the rotor),CASE2(containing full passages of the nozzle and the rotor,volute),and CASE3(containing all flow passages of the liquid expander).Flow losses of different flow passages in the thress cases were calculated,and the flow inhomogeneity in volute,nozzle and rotor was analyzed.Flow losses were compared between the rated operating condition and the operating condition at 50%rated rotaional speed and the 50%rated flow rate,and the steady and unsteady flow in the rotors was discussed.Based on the analysis,six improved liquid expander were designed and their full performance tests were carried out.4.Research on cryogenic cavitation of the liquid expander.The cavitation model was analyzed and the cryogenic cavitation model was given.The numerical simulation method was validated by comparing simualtion resutls with experimental results of cryogenic hydrofoil.Performances of the liquid expander with cryogenic cavitation were studied with different inlet temperature and outlet pressure.The research of this paper has a guiding effect on the development and operation of the liquid expander for SC-CAES,and it can also verify the research of liquid expansion machine in LNG liquefaction and air separation. |
PDF Full Text Request