Mechanism and Performance of a Novel Atomizer with Supersonic Configuration

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Theodore Cummings
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1 Mechanism and Performance of a Novel Atomizer with Supersonic Configuration Muh-Rong Wang and Pin-Jen Chen Department of Aeronautics and Astronautics National Cheng Kung University, Taiwan

2 1. Introduction Metal powder production Literature review Outline 2. Experimental setup Atomizer design Experimental setup 3. Results and discussion Atomization mechanism Atomization performance 4. Conclusions

3 Metal powder production Metal powders are used widely in powder metallurgy (P/M), metal injection molding (MIM), heat pipe and thermal spray etc. Powder fabrication techniques 1. Chemical 2. Electrolytic 3. Mechanical 4. Atomization Water Gas

4 Types of gas atomizer (a) Free fall (b) Confined Internal-mixing External-mixing

External mixing-1 2002, Anderson Developed high pressure gas atomization (HPGA) nozzles

5 External mixing , Anderson Developed high pressure gas atomization (HPGA) nozzles and 316L stainless steel was atomized. N 2 gas operating pressure: 2.76 and 5.52 MPa N 2

6 2007, Ünal ISTP-23 External mixing-2 Melt: Tin

7 Internal mixing Wang et al. Melt: Sn63Pb37 P Melt P Gas 400 kpa 430, 450, 480, 500, 520 kpa

8 Internal mixing Wang et al. Melt: Sn63Pb Median particle size, d 50 ( m) T m =400 o C T m =450 o C Gas atomization pressure (kg/cm 2 )

9 2009,Planche et al. De Laval nozzle ISTP-23 Studied liquid metal atomization using a De Laval nozzle by both experimental and modelling approaches.

10 Objectives ISTP-23 To develop an internal-mixing atomizer with supersonic configuration with low gas pressure for metal powder production. To investigate the atomization mechanism at initial state and stable state. To investigate the performance of the atomizer Cold model experiments (water) Melt experiments (copper)

11 2. Experimental setup Atomizer design Experimental setup

12 Atomizer design Liquid Delivery tube Gas Gas Throat area A*=46.7 mm 2 Exit area A e =88.9 mm 2 Convergence Divergence P g : Gas pressure (air, 1~5.5 bar) D : Inner diameter of delivery tube (2~4 mm) AR: 1.9

13 Experimental setup water Malvern INSITEC Real-time measurement

14 3. Results and discussion Atomization mechanism Atomization performance - Atomization of water - Atomization of melt

15 Atomization mechanism-1 Test condition P g = 5.5 bar D = 2 mm Sample rate: 5 khz 10 fps

16 Atomization mechanism-2 t= 2.2 ms t= 4.6 ms t= 9.2 ms t= 15.0 ms t= 21.8 ms t= 33.8 ms

17 Atomization mechanism-3 Gas pressure increasing No Shock exists Shock exists at the divergent section Shock Recirculation zone

18 Atomization behavior at different gas pressure D= 2 mm P g = 1 bar Pg= 2 bar Pg= 3 bar Pg= 4 bar Pg= 5 bar Pg= 5.5 bar

19 Atomization behavior at different inner diameter of delivery tube P g = 3 bar P g = 5.5 bar D= 2 mm D= 3 mm D= 4 mm D= 2 mm D= 3 mm D= 4 mm

20 Atomization Characteristics D= 2 mm P g = 5.5 bar 2005, Mates and Settles

21 3. Results and discussion Atomization mechanism Atomization performance - Atomization of water - Atomization of melt

22 Effect of gas pressure on aspiration at delivery tube tip Delivery tube tip pressure (bar) Liquid was forced to flow through the delivery tube by gravity and aspiration at the tube tip. Tube tip pressure is negative at all gas pressure Gas Pressure (bar)

23 Effect of gas pressure on median particle size Median particle size, d 50 ( m) D=2.0 mm D=3.0 mm D=4.0 mm Median particle size (d 50 ) decreases as gas pressure increases. Better atomization performance is achieved by reducing the inner diameter of delivery tube Gas Pressure (bar)

24 3. Results and discussion Atomization mechanism Atomization performance - Atomization of water - Atomization of melt

25 Results of atomization of copper Test condition Melt: Cu P g = 4 bar D 0 = 2 mm d 50 = m

26 Conclusions A novel internal-mixing atomizer has been designed and the mechanism and performance of the atomizer has been characterized. A recirculation zone inside the nozzle was found due to the downward movement of internal shock at the divergent section as the gas pressure is increased. Particle size of 8.22 m at P g =4 bar is achieved with 2.0 mm diameter of delivery tube. In experiments with melt, the median mean particle size of m is achieved at a relatively low pressure of 4 bar.

27 Thanks for your attention!

IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 11, 2016 ISSN (online):

IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 11, 2016 ISSN (online): 2321-0613 Effect of Aspiration Pressure on Convergent Nozzle Employed for Gas Atomization of Liquid