Reserch And Development Of Large Capacity Atomization Nozzle For Small Space With High Pressure And Its Verification In Engineering

The atomization nozzle of large capacity in a small space with high pressure is required by industry practice. The classical theories about liquid atomization and various atomization nozzles as well as their working principle were investigated in this thesis. The nozzle with twin(multi-) jets of same liquid aimed at one point for atomization(T/MJAO) was suggested. Its feasibility and performance were numerically and experimentally studied, and then the nozzles were applied in the industrial equipments, by which the atomization performance was verified.It was found by experiment and numerical simulation that increasing the liquid supply pressure or reducing the mass flux ratio of gas to liquid can increase the capacity of the inner-mixed gas assisting nozzle(IGAN),however, the atomization performance becomes worse. Referring to the principle of outer-mixed gas assisting nozzle(OGAN) as well as solid baffle hitting nozzle(SBHN), the T/MJAO nozzle was suggested, of which the feasibility was confirmed by the simulation with the simplified model. Then its atomization principle was analyzed while its structure was suggested. The T/MJAO nozzle atomization performance of different structure is systemically tested in a cold experimental rig, which is very satisfied. It is found that the flow coefficient of 8 kinds of nozzle ranges from 0.55 to 0.8 that is mainly influenced by the ratio of length to hole diameter of the nozzle. Atomization angle100? becomes larger slightly with in a small variation range when liquid flow rate increases, while it is slightly and positively related to the angle between jets. The100? decreases with the jet number increasing in tendency. The average droplet diameter dsmd increases with the decreasing of the angle between jets of T/MJAO nozzle, while the uniformity coefficient m decreases. When the jet number aimed one point increases, the average droplet diameter dsmd increases, and the uniformity coefficient m decreases. Theincreasing of nozzle hole diameter increases the average droplet diameter dsmd in tendency but the effect is very light. An atomization process physical model of the T/MJAO nozzle is presented by which the atomization performance of the T/MJAO nozzle was predicted, and a good agreement between the prediction and measurement was achieved. The large capacity atomization for a small space with high pressure can be arranged appropriately by parallel T/MJAO nozzles. And the design code for the T/MJAO nozzle was pointed out.The effect of the preesure environment on the atomization was analized, and the performance of high preesure of the nozzle was indicated. The demonstration for T/MJAO nozzle was conducted to verify its structure and atomization performance by application to an industrial mixer with high pressure of20 MPa for a methylamine condenser and a reactor of the complete circulation of aqueous solution for urea. The practical operations indicated the execellent performance of T/MJAO nozzle. In order to understand clearly the effect of the premixing and the atomization performance, a phase map for NH3- CO2 under 20MPa was presented, and a comprehensive model of the urea synthesis in the complete circulation of aqueous solution reactor was established. The model prediction agrees well with the operation dada.