Influence of Self-excited Vibrating Cavity Structure on Droplet Diameter Characteristics of Twin-fluid Nozzle

It is a great challenge to find effective atomizing technology for reducing industrial pollution; the twin-fluid atomizing nozzle has drawn great attention in this field recently. Current studies on twin-fluid nozzles mainly focus on droplet breakup and single droplet characteristics. Research relating to the influences of structural parameters on the droplet diameter characteristics in the flow field is scarcely available. In this paper, the influence of a self-excited vibrating cavity structure on droplet diameter characteristics was investigated. Twin-fluid atomizing tests were performed by a self-built open atomizing test bench, which was based on a phase Doppler particle analyzer(PDPA). The atomizing flow field of the twin-fluid nozzle with a self-excited vibrating cavity and its absence were tested and analyzed. Then the atomizing flow field of the twin-fluid nozzle with different self-excited vibrating cavity structures was investigated.The experimental results show that the structural parameters of the self-excited vibrating cavity had a great effect on the breakup of large droplets. The Sauter mean diameter(SMD) increased with the increase of orifice diameter or orifice depth. Moreover, a smaller orifice diameter or orifice depth was beneficial to enhancing the turbulence around the outlet of nozzle and decreasing the SMD. The atomizing performance was better when the orifice diameter was2.0 mm or the orifice depth was 1.5 mm. Furthermore, the SMD increased first and then decreased with the increase of the distance between the nozzle outlet and self-excited vibrating cavity, and the SMD of more than half the atomizing flow field was under 35 μm when the distance was 5.0 mm. In addition, with the increase of axial and radial distance from the nozzle outlet, the SMD and arithmetic mean diameter(AMD) tend to increase. The research results provide some design parameters for the twin-fluid nozzle, and the experimental results could serve as a beneficial supplement to the twin-fluid nozzle study.

Micro-interface enhanced mass transfer sodium carbonate absorption carbon dioxide reaction

Micro-interface intensified reactor(MIR)can be applied in series/parallel in the absorption of CO_(2)in industrial gases by Na_(2)CO_(3)due to the ability to produce large numbers of stable microbubbles.This work focuses on the variation pattern of mass transfer characteristics parameters of the reaction gas in Na_(2)CO_(3) solution under the influence of different solution properties and operating parameters in the reaction of CO_(2)absorption by Na2CO3.The mass transfer characteristics parameters include bubble Sauter mean diameter,gas holdup,interfacial area,liquid side mass transfer coefficient,and liquid side volume mass transfer coefficient kLa.The solution properties and operating parameters include Na2CO3 concentration(0.05–2.0 mol·L^(-1)),superficial gas velocity(0.00221–0.01989 m·s^(-1)),superficial liquid velocity(0.00332–0.02984 m·s^(-1)),and ionic strength(1.42456–1.59588 mol·kg^(-1)).And volumetric mass transfer coeffi-cients kLa and superficial reaction rates r of the MIR and the bubble column reactor are compared in the reaction of sodium carbonate absorption of carbon dioxide,and the former shows a greater improvement under different solution properties and operating parameters.The enhanced role of MIR in mass transfer in non-homogeneous reactions is verified and the feasibility of industrial practical applications of MIR is demonstrated.

Dispersion Performance of Methanol-Diesel Emulsified Fuel Prepared by High Gravity Technology

A new continuous process for preparing methanol-diesel emulsified fuel with an Impinging Stream-Rotating Packed Bed is proposed. The droplet size of dispersed phase(methanol) of the emulsified fuel has a significant effect on the combustion of methanol-diesel emulsified fuel. In this paper, the methanol-diesel emulsified fuel uses diesel as the continuous phase and methanol as the dispersed phase. The Sauter mean diameter of the dispersed phase of methanol-diesel emulsified fuel was characterized with microphotography and arithmetic method. The experimental result showed that the Sauter mean diameter of the dispersed phase, which was decreased with the augmentation of the high gravity factor, liquid flow rate and emulsifier dosage, was inversely proportional to the methanol content. The Sauter mean diameter of the dispersed phase can be controlled and adjusted in the range of 12—40 μm through the change of operating conditions. The correlative expressions of the Sauter mean diameter of emulsified fuel were obtained and the calculated values agreed well with the experimental values.

Predictive models for characterizing the atomization process in pyrolysis of methyl ricinoleate

Pyrolysis of methyl ricinoleate(MR)can produce undecylenic acid methyl ester and heptanal which are important chemicals.Atomization feeding favors the heat exchange in the pyrolysis process and hence increases the product yield.Herein,predictive models to characterize the atomization process were developed.The effect of spray distance on Sauter mean diameter(SMD)of atomized MR droplets was examined,with the optimal spray distance to be 40-50 mm.Temperature mainly affected the physical properties of feedstock,with smaller droplet size obtained at increasing temperature.In addition,pressure had significant influence on SMD and higher pressure resulted in smaller atomized droplets.Then,a model for SMD prediction,combining temperature,pressure,spray distance,and structural parameters of nozzle,was developed through dimensionless analysis.The results showed that SMD was a power function of Reynolds number(Re),Ohnesorge number(Oh),and the ratio of spray distance to diameter of swirl chamber in the nozzle(H/dsc),with the exponents of-1.6618,-1.3205 and 0.1038,respectively.The experimental measured SMD was in good agreement with the calculated values,with the error within±15%.Moreover,the droplet size distribution was studied by establishing the relationship between the standard deviation of droplet size and SMD.This study could provide reference to the regulation and optimization of the atomization process in MR pyrolysis.

Analysis of Bubble Behavior in a Horizontal Rectangular Channel under Subcooled Flow Boiling Conditions

Experiments on subcooled flow boiling have been conducted using water in a rectangular flow channel.Similar to the coolant channel in internal combustion engines(IC engines),the flow channel in this experiment was asymmetrically heated.Bubble images were captured using a high speed camera from the side view of the channel.The experimental conditions in terms of bulk temperature,bulk velocity,pressure and heat flux ranged from 65°C–75°C,0.25 m/s–0.75 m/s,1–1.7 bar and 490 kW/m2–700 kW/m2,respectively.On the basis of these tests,a statistical analysis of the bubble size has been conducted considering a population of 1400 samples.It has been found that the mean Sauter bubble diameter increases with the decrease of subcooling,bulk velocity,pressure and increased heat flux.A modified correlation has been finally proposed to predict the mean Sauter bubble diameter under subcooled flow boiling conditions upstream of the onset of significant void,which shows good accuracy with the experimental results.