Experimental and Numerical Simulation of New Aluminum and Steam

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Experimental and Numerical Simulation of New Aluminum and Steam Vortex Combustor Xianhe Chen, Zhixun Xia, Liya Huang, Xudong Na, and Hu Jian Xin Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03412 • Publication Date (Web): 25 Jan 2018 Downloaded from http://pubs.acs.org on January 26, 2018

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Experimental and Numerical Simulation of New Aluminum and Steam Vortex Combustor Xianhe Chen a, Zhixun Xiaa, Liya Huang*,a , Xudong Naa, Jianxin Hub a Department of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China b College of Aerospace Engineering, Chongqing University, chongqing 400044, China

Abstract: In this paper, we report an experimental research on a vortex combustor for aluminum and steam combustion. High-temperature and high-pressure steam is obtained by combining alcohol with the combustion of oxygen and water, powder from a conventional piston drive, and nitrogen as fluidizing gas. The experimental results show that the vortex combustor can maintain aluminum-steam combustion. However, combustion product deposition is a challenge to the experiment. A new vortex combustor configuration, in which aluminum particles enter the combustor from the end face, is hence proposed, and a numerical simulation is conducted. Results suggest that three vortexing zones exist in the vortex combustor, namely, outer, intermediate, and internal vortex zones. Besides, influencing factors such as the inlet position of aluminum particles and particle size are also studied. And the results show that the combustion efficiency was prone to decrease as the aluminum particle inlet position and particle diameter increased. 1. Introduction The combustion of aluminum and water produces hydrogen and heat of up to 15.2 MJ/kg, thus allowing aluminum to be widely used in propellants and other energy field 1,2. Water is obtained outside as an oxidant, thereby saving oxidant space and improving specific impulse in underwater engine. In underwater power system applications 3-7, the hybrid aluminum combustor (HAC)6 or HAC-solid oxide fuel cell (HAC-SOFC)7 were proposed by Daniel, and the results showed that the energy density of this system is much higher than that of Lithium battery. Meanwhile, hydrogen produced by the combustion of aluminum and water has broad prospects 8-12. The above research shows that aluminum water combustion has a broad application prospect in the utilization of aluminum fuels. However, continuous and stable combustion of aluminum and water is the key technology of aluminum fuel application. Aluminum-water ignition combustion is difficult to obtain because of the presence of an aluminum oxide layer and high ignition temperature. This issue led to the proposition of the vortex combustor concept by Miller13,14, and experimental studies were conducted, but no detailed experimental data were published. The principle of the model revolves around the use of high-temperature steam in the combustor to form a whirlpool while aluminum powder is tangentially injected into the combustor. The residence time of aluminum in the combustor is increased to allow the aluminum particles to achieve self-sustaining combustion and improve combustion efficiency. Moreover, numerous works have been completed on the vortex combustor, such as the numerical simulation and aluminum particle combustion model15. So far, the vortex combustor is the only device that can maintains the continuous and steady combustion of aluminum and water. The purpose of this study is to verify the vortex combustor can achieve stable combustion of aluminum-steam and improve combustion efficiency. Producing high-temperature steam from the combustion of alcohol and oxygen

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is proposed on the basis of previous research, thus leading to the design of the aluminum-steam vortex combustor. Meanwhile, a stable aluminum-steam combustion is realized. A new vortex combustor configuration with aluminum particles entering the combustor from the end face is also proposed. A numerical simulation is conducted according to existing research results and the established aluminum particle ignition combustion model. Furthermore, the influence of the incident position and angle of the aluminum particles and particle size on the aluminum-steam vortex combustor performance are discussed.

2. Theory 2.1 Physical model A vortex combustor with four circumferential steam and aluminum particle inlets is proposed according to the concept of Miller (C-1)13, as shown in Figure 1. A vortex combustor experiment with aluminum-steam

combustion is conducted according to the C-1 configuration. The experimental results show that the C-1 configuration can achieve aluminum-steam combustion but with a large product within the alumina deposition, which reduces combustor performance. Another vortex combustor configuration (C-2) is therefore proposed, as also shown in Figure 2. The C-2 configuration also uses four cycles of high-temperature steam to form a vortex flow within the combustor while the aluminum and fluidized gas nitrogen pass through the four inlet ports from the end face into the combustor. In the C-2 configuration, the direction in which the aluminum powder passes into the combustion chamber is parallel to the outlet direction and away from the wall. Therefore, the C-2 configuration can theoretically reduce product deposition.

Figure 1. Schematic of the vortex combustor C-1

Figure 2. Schematic of the vortex combustor C-2

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2.2 Gas flow computation All numerical simulation results are based on FLUENT software in this paper. A quarter of the combustor is simulated with periodic boundary conditions with the purpose of reducing computational cost. Turbulence effects are demonstrated using the Reynolds stress model with linear pressure-strain approach while considering the strong vortex flow field in the vortex combustor15. Moreover, the simulations are conducted under the steady-state conditions. Besides, the eddy dissipation model is used to simulate gas phase combustion15. 2.3 Aluminum particle combustion model A simplified combustion model of aluminum particles is obtained from reference 15,16, which can be used for the calculation of the two-phase flow of aluminum particles and its distribution for the complete combustion process. The results of this model are verified using an experiment15. A diffusion control of the continuum regime is used in this model, and the model equations is given by 15,17 ρ Dox m& (1) = ln (1 + iYO ,∞ ) , 2 r 4π r where m& is the mass consumption rate of particle in kg/s, ρ is the gas density, Dox is the diffusivity of

the oxidizer, r is the particle radius, YO, ∞ is the mass fraction, and i is the stoichiometric fuel–oxidizer mass ratio. Considering the influence of alumina on the combustion of aluminum particles, the particle mass change can be obtained in the flow field15. dm p

=

dt

ρ S Al Dox r

ln (1 + iYO ,∞ ) ,

(2)

where S Al is the particle surface area15 exposed in the environment and m p is the particle mass. In the case of various oxidants, the mass change in the aluminum particles is calculated using the cumulative method. The energy conservation equation18 between the particles and the flow field can be expressed as mpcp

dTp

dt where Q&

= Q& conv + Q& rad + Q& comb + Q& phase + Q& cond ,

conv

(3)

is the convection heat, Q& rad is the radiation heat, Q& cond is the condensation heat, Q& phase is the

latent heat, and Q& comb is the heat of combustion. The collision process of the aluminum particle is driven by the relative velocity between the particle and the surrounding alumina and the alumina deposition model is given by15,19 dmdep

π

r 2 u p − u g Csηc , (4) 16 where mdep is the oxide deposition mass, u p is the particle velocity, u g is the gas velocity，Cs is the local dt

=

oxide concentration, and ηc is the collision efficiency, which is equal to 0.25. Most aluminum particle ignition theories20-22 suggest that a particle ignites successfully when its temperature reaches the rupture temperature of the oxide layer. The ignition temperature15,23 is obtained by fitting the experimental data under different particle sizes. 2.4 Particle distribution computation The aluminum particles are tracked using the Lagrangian method and the stochastic model is used to the 15

trajectory of the aluminum particles in the flow field . The aluminum particle combustion model is realized by using the discrete phase model’s UDF function of the FLUENT. After the aluminum particles enter the combustor,

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their motion is dominated by the drag force resulting from the velocity difference between the gas and the particle. The governing equations for the particle are as follows15,24: dx p dt du p dt Fp =

= up ,

(5)

= Fp ,

(6)

3 CD ρ (u g − u p ) u g − u p , 4 ρpd

(7)

15,24 Where CD is the drag coefficient of particles ,

24 (1 + Re 2/3 p / 6 ) / Re p CD =  0.424 

for Re p ≤ 1000 for Re p > 1000

.

(8)

3. Experiment apparatus In the experiment system shown in Figure 3, high-temperature steam is obtained by adding the proper amount of water to the combustion of alcohol and oxygen. The steam obtained by this method contains part of a carbon dioxide component. The carbon dioxide content is low at approximately 16%. This test is not completely aluminum-steam combustion because carbon dioxide is also involved in the aluminum combustion process. The aluminum particle is supplied by a conventional piston drive, and nitrogen is used as the fluidizing gas. The experimental parameters are obtained using a pressure sensor, camera, and other equipment. Figure 4 shows the vortex combustor under the experimental C-1 configuration.

Figure 3. Schematic of experiment system Figure 4. The experiment vortex combustor The combustion efficiency of the combustor ηc* is defined by * ηc = cexp / cth* *

, * where cth* and cexp are the theoretical and experimental characteristic exhaust velocities, respectively.

(9)

The theoretical characteristic exhaust velocity is determined by the thermal chemical condition in the * combustor, whereas the experimental characteristic exhaust velocity cexp is given by * cexp =

po At m& 0

, (10) & where po is the combustor pressure, At is the nozzle throat area, and m0 is the total mass flow rate in the combustor expressed as m& 0 = m& Al + m& N 2 + m& H 2 O + m& CO2 − m& cond , (11)

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& Al , m& N 2 , m& H 2O , and m& CO2 is the mass flow rate of aluminum, nitrogen, steam, and carbon dioxide, where m & cond is the deposition rate of products. m& cond = mcond / t , where mcond is the total mass of the respectively, and m deposition product in the combustor and t is the running time. The total mass flow rate is used as the numerical simulation value under the same conditions because the amount of deposited alumina and the running time cannot be obtained accurately during this test. The numerical simulation of aluminum particle combustion efficiency can be expressed as

η=

∆mAl × 100% . mAl

(12)

where ∆mAl is the aluminum consumption and mAl is the inlet aluminum mass. The combustion efficiency of the aluminum particles obtained by numerical simulation is thermal efficiency, which is proportional to the characteristic velocity efficiency η = ηc2∗ .

Figure 5 shows the experimental configuration of the vortex combustor test, and the experimental results show that the C-1 configuration can achieve aluminum-steam combustion. The temperature of the high-temperature steam is determined by thermodynamic calculation as 817 K and the experiment measured temperature is 750K. The temperature of the steam and carbon dioxide temperature of 750 K is used as the calculated temperature in the numerical calculation to consider the heat loss in the experiment. According to the parameters of the aluminum particles provided by the manufacturer, the particle size is 10 µm and the aluminum content is 99%. The temperature field obtained by numerical simulation in the C-1 configuration is shown in Figure 6. The comparison between the experiment and numerical simulation results is shown in Table 1.

Figure 5. Experimental scene of the vortex

Figure 6. Temperature distribution of the vortex

combustor test

combustor

Table 1. Experiment and numerical simulation parameter comparison Experiment

& Al , g/s m m& N , g/s

Numerical

16.11

16.11

17.68

17.68

particle diameter, µm Pressure, MPa At , mm2 Out mass flow rate, g/s cth* , m/s

19.46 10 0.893 41.85 34.8 1380.1

19.46 10 0.893 41.85 34.8 -

* , m/s cexp

1073.9

-

77.81 60.54

65.82

2

m& H 2 O + m& CO2 , g/s

ηc , % *

η,%

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Table 1 shows that the thermal efficiency of the experiment is 60.54%, which is less than the combustion efficiency of the numerical simulation at 65.82%. This result is explained in the following section. Firstly, numerical simulation using the adiabatic wall boundary condition and aluminum particle combustion as a response to a single-step process results in higher combustion chamber temperature and greater combustion efficiency than the experimental value. Secondly, the aluminum average particle size used in the experiment is 10µm, which is not strictly a single particle size of 10µm. The numerical simulation uses a single particle size of 10µm, which may also result in inconsistencies with the laboratory data. Thirdly, the alumina product deposit in the combustor during the test process, and causes changement of the internal combustor configuration and thus make aluminum particle deposit more easily, and thus eventually decreasing combustion efficiency. Finally, the aluminum particles undergo oxidation in the storage and experiment process, which means that the actual active aluminum content provided by the manufacturer is lower than 99%. Therefore, the experimental value is lower than that of the numerical simulation. The numerical simulation results generally agree with the experimental values. The numerical simulation method can be used to characterize the combustion rules of the aluminum and steam vortex combustor. Since the combustor pressure is only 0.893MPa, the combustion efficiency is low. In addition, the experiment shows that combustion product deposition in the combustor is serious and can even cause nozzle clogging due to the sizes of the combustion products and the nozzle throat. The next section discusses the C-2 configuration, which is designed for solving the problem of combustor deposition and aluminum particle combustion as much as possible. 4. Results and discussion 4.1 C-2 configuration study The combustion efficiency of C-1 configuration is low, mainly because the flow rate, configuration design, et al. does not reach the optimal value. Therefore, in the study of C-2 configuration, all inlet parameters are selected referencing to the HAC system5,6. In this configuration, the flow rate of the aluminum powder is 16 g/s, aluminum particle size is 10µm, flow rate of fluidized gas is 8 g/s, inlet position of aluminum particles is H=0.6 R, steam flow rate is 20 g/s, and steam temperature is 750 K. Table 2. Grid independent verification Cells 300,000 350,000 400,000 Combustion efficiency, % 95.15 95.71 95.31 Table 2 is the result of grid independent verification. When the cells is more than 350, 000, the change of the combustion efficiency is less than 0.5%. Thus a number of 350,000 grids are applied to our numerical simulation finally. As shown in Figure 7, the steam entering the combustor forms a vortex flow. The vortex region is divided into three parts. The first part is the outer vortex region (radius: 0.8R-R), which forms a vortex flow outside the combustor. The second part and main vortex region is the intermediate vortex region (radius: 0.3-0.8 R), which forms the vortex flow in the direction of the combustor outlet. The third part is the internal vortex region (radius: 0-0.3 R), which forms a vortex flow toward the exit direction and the middle vortex region, but the proportion is smaller than that in the intermediate vortex region. The aluminum particles and fluidized gas enter the vortex region and form a vortex flow. Particles in the intermediate vortex region (i.e., H=0.3-0.8 R) can easily form a vortex flow and export it to the combustion chamber while reducing particle wall deposition. When H is less than 0.3 R, the majority of particles may be discharged directly from the combustor outlet, thus possibly causing the aluminum particles to burn incompletely or fail to ignite successfully. However, when H is greater than 0.8 R, the majority of particles may hit the wall and cause deposition. Figure 8 shows the trajectory of the aluminum particles in the combustor when H=0.6 R and we only show the trajectory of the particle before it burns completely. In this configuration, the aluminum particles enter the combustor and concentrate in its central region, thereby helping reduce the deposition of combustion products. In the flow field, the aluminum particles swirl due to the combined action of fluidized gas and high-temperature steam, thus increasing the residence time of the aluminum particles in the combustor, which is conducive to aluminum particle combustion.

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Figure 7. Streamline of the steam Figure 8. Trajectories of aluminum particles Figure 9 shows the temperature cloud diagram of the C-2 configuration, whereas Figure 10 shows a hydrogen mass source cloud map that represents the combustion zone of the aluminum particles. Figure 9 shows that the high-temperature zone is concentrated in the combustion center area, whereas the temperature near the wall of the combustor is relatively low. The closer to the wall, the lower the temperature. This pattern reduces the wall temperature and the thermal protection demand of the combustor. Figure 10 shows that the aluminum particles combust in the internal vortex region and mainly in the intermediate vortex region. The aluminum particles are burned in the intermediate vortex region to generate heat and form a high-temperature region, thereby enabling the aluminum particles to ignite and continue to burn. The calculation results show that the combustion efficiency of the aluminum particles is 95.71%, thereby showing that the aluminum particles have high combustion efficiency under the C-2 configuration.

Figure 9. The diagram of temperature cloud

Figure 10. The diagram of hydrogen mass source

4.2 Effect of aluminum particle inlet position According to the distribution of the vortex region in the flow field, different aluminum particle inlet positions lead to different motions of the aluminum particles in the combustor, thus generating different combustion effects. Considering the distribution range of each vortex region, the inlet position H is equal to 0.2, 0.4, 0.6, 0.8, and 0.9 R. The calculation shows that the aluminum particles cannot maintain ignition combustion when H is 0.2 and 0.9 R. Therefore, the 4/15 and 13/15 R positions are calculated to describe the influence of the particle inlet position. Table 3. Burning efficiency statistics H

Combustion efficiency, %

≤0.2 R 0

4/15 R 90.83

0.4 R 95.49

0.6 R 95.71

0.8 R 96.55

13/15 R 89.19

≥0.9 R 0

Table 3 shows the combustion efficiency of the aluminum particles obtained under different inlet positions. Figure 11 shows the particle trajectory distribution. Table 3 shows that in the outer vortex region, the combustion efficiency of the aluminum particles gradually decreases with the increase in H. When the

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aluminum particles reach a certain position, they cannot self-sustain combustion because the aluminum particles become more likely to collide with the wall under aerodynamic action as H increases. The residence time of the aluminum particles in the flow field is reduced as H increases; therefore, the aluminum particles are deposited on the wall when they are not completely burned, and the combustion efficiency is reduced. In addition, combustion efficiency of the aluminum particles in the intermediate vortex region is relatively high compared with that in other regions, reaching more than 95%. The combustion efficiency of aluminum particles is higher in this region than in others because of their movement. On the one hand, long residence time is convenient for the aluminum particles to be completely burned; on the other hand, high temperature in the region is conducive to the ignition of aluminum particles. Furthermore, in the internal vortex region, the combustion efficiency of aluminum particles decreases with the decrease in H. When the aluminum particles are smaller than a certain position, they do not undergo self-sustaining combustion. In the internal vortex region, movement of the aluminum particles is depicted by two trends: one is driven by the airflow into the intermediate vortex region and even the outer vortex region; the other trend is directly discharging the combustor. The smaller the H, the larger the proportion of the directly discharged aluminum particles and the lower the combustion efficiency of the aluminum particles. Eventually, the aluminum particles cannot sustain burning. Therefore, the optimal value of the particle inlet position H is between 0.4R and 0.8 R.

Figure 11. Effect of H on distribution of particle diameter (µm) in chamber 4.3 Effect of aluminum particle diameter Table 4. Burning efficiency statistics 10 15 19 20 Diameter, µm Combustion efficiency, %

95.71

97.34

92.84

88.92

≥21 0

In this section, we discuss the combustion rules of the different aluminum particle diameters in the combustor. Table 4 shows that the combustion efficiency increased slightly when the particle size increased from 10um to 15µm. As the aluminum particle size continues to increase, combustion efficiency gradually decreases. When the particle size is larger than 21µm, the aluminum particles can no longer maintain combustion. According to the analysis of particle force, the larger the particle size, the greater the centrifugal force and the easier to the particle to move outside and deposit on the wall. Therefore, with increased particle size, the combustion efficiency of the aluminum particles decreases gradually. When the particle size is large, the particle ignition delay time increases. Under the influence of centrifugal force and resistance factors, successfully ignited particles are trapped before burning completely. When most of these particles do not complete combustion, combustion efficiency decreases, thus leading to a reduction in combustion chamber temperature. Consequently, ignition delay time continues to increase and combustion efficiency continues to decline, thereby resulting in non-ignition of the aluminum particles. The aluminum particles therefore cannot maintain combustion. The combustion efficiency increased slightly when the particle size increased from 10um to 15µm. The reason is that 10µm particles flow with the gas easily than 15µm particles for its lighter mass, which makes 10µm particles more likely to be deposited on the front wall. However, their combustion efficiency is very close, and both of the particle sizes combustion efficiency is high. Figure 12 and Figure 13 show the distribution of temperature under different particle diameter, where Figure 13 shows the temperature

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along a radial line. From Figure 12 we can see that the temperature of the flow field decreases gradually with the increase of particle size, and the high-temperature zone gradually moves towards the exit direction of the vortex combustor. The reason is that with the increase of particle size, the combustion time increased, the particles movement distances increases, so that the aluminum particles are still burning when they are near the combustor exit. In addition, Figure 13 shows that when the particle size is 20µm, the temperature of the intermediate vortex region is as low as 2100K, which is extremely close to the ignition temperature of the aluminum particles. When the particle size continues to increase, the particles will fail to ignite. Therefore, 10-15 micron aluminum particles makes the vortex combustor has the best performance.

Figure 12. Temperature distribution clouds at different particle diameter

Figure 13. Temperature distribution at different particle diameter along a radial line

4.4 Effect of aluminum particles incident angle Table 5. Burning efficiency statistics 30 15 0 Incident angle, ° Combustion efficiency, %

92.56

96.64

95.71

−15 92.84

Figure 14. Temperature distribution clouds at different incident angles The incident angle of the aluminum particles directly influences their state of motion in the combustor. Taking a certain incident angle may be beneficial to the combustion of the aluminum particles. Positive incident angle is defined toward the center of the combustor, and we use 30°, 15°, 0°, and -15° for this study(as show in Figure 14). Table 5 shows the combustion efficiency of the aluminum particles at each incident angle. Figure 14 shows the temperature distribution cloud diagram. According to Table 5, the proper positive incident angle is beneficial to the combustion of the aluminum particles. When the incident angle is too large, combustion efficiency decreases because aluminum particles enter the inner vortex region to discharge the combustor directly. However, small incident angles make the aluminum particles remain in the

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intermediate vortex region, thus increasing their residence time. Meanwhile, a negative incident angle decreases the combustion efficiency of aluminum particles because the initial radial velocity of the aluminum particles is negative, thus making them susceptible to wall deposition. Figure 14 shows that the temperature of the wall surface is relatively low, which is beneficial to the thermal protection of the combustor. Therefore, the optimal value of aluminum particles incident Angle is between 0° to 15°. 5. Conclusions An aluminum and steam vortex combustor experiment is designed and operated. High-temperature and high-pressure steam is generated using alcohol and the combustion of oxygen and water. Powder is supplied with a conventional piston drive, and the system uses nitrogen as the fluidizing gas. The experimental results show that the vortex combustor can maintain aluminum-steam combustion. However, the internal deposition of the

combustor is serious and can occasionally cause nozzle blockage. The numerical simulation results agree with the experimental values, and the numerical simulation method can be used to characterize the combustion rules of the aluminum and steam vortex combustor. A new type of vortex combustion chamber is designed, and a numerical simulation is conducted. The vortex region is divided into three parts, namely, the outer, intermediate, and inner vortex regions. The vortex regions can increase the residence time of the aluminum particles in the combustor, which is beneficial to aluminum particle combustion. The influences of the different eccentric distances of the aluminum particle inlet position, aluminum particle diameter, and aluminum incident angle are analyzed. The combustion efficiency of the aluminum particles gradually decreases with increased H. When the particles reach a certain position, they cannot self-sustain combustion. In the intermediate vortex region, the combustion efficiency of aluminum particles is relatively high (reaching more than 95%), thereby indicating that aluminum particle combustion efficiency is higher in this region than in the others. In the internal vortex region, the combustion efficiency of aluminum particles decreases with H. The optimal value of H is between 0.4R and 0.8R. As particle size increases, the combustion efficiency gradually decreases. When the particle size is large enough, combustion efficiency reaches a critical value. When the combustion efficiency is lower than the critical value, the aluminum particles cannot sustain combustion. The correct positive incident angle is beneficial to the combustion of aluminum particles and the optimal value of incident angle is between 0° and 15°. 6. Acknowledges This work was supported by the National Defense Science and Technology Innovation Zone (grant No.1716313ZT00802701) and the National Natural Science Foundation of China (grant No. 51406231). 7. References (1) Mercati S, Milani M, Montorsi L, Paltrinieri F. Applied Energy 2012, 97(0), 686-694. (2) Jeffrey M. Bergthorson, Yinon Yavor, Jan Palecka. Applied Energy 2017, 186, 13-27. (3) Jonathan A. Peters. Summary of recent hybrid torpedo powerplant studies. 2007. (4) Dominic Barone. AIAA 2011-5904. (5) Xianhe Chen, Zhixun Xia, Liya Huang and Jianxin Hu. 2017 international conference on environment and energy engineering, 2017. (6) Daniel F. W. , Christopher P.C. , W. Ethan Eagle. J. propulsion and power 2013, 29(3), 675-685. (7) Daniel F. W. ,Christopher P. C. J. Power Sources 2013, 221, 272-283. (8) Baozhong Zhu, Fan Li, Yunlan Sun, Yuxin Wu, Qichang Wang, Qi Wang, and Weikang Han. Energy & Fuels, 2017, 31(8), 8674-8684. (9) Federica Franzoni, Stefano Mercati, Massimo Milani, Luca Montorsi. Int J Hydrogen Energy 2011, 36, 2803-2816. (10) Vladimir Shmelev, Vladimir Nikolaev, Ji Hyung Lee, Chungsik Yim. Int J Hydrogen Energy 2016, 41, 16664-16673. (11) Yang Weijuan, Zhang Tianyou, Liu Jianzhong, Wang Zhihua, Zhou Junhu, Cen Kefa. Energy 2015, 93(1), 451-457. (12) Tianhua Yang, Wenqi Zhang, Rundong Li, Bingshuo Li, Xingping Kai, and Yang Sun. Energy &

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Fuels 2017, 31(9), 9605-9612. (13) T.F.Miller, J.L.Walter, D.H.Kiely. Proceedings of 2002 Workshop on Autonomous Underwater Vehicles, San Antonio, 2002. (14) Timothy F. Miller, John D. Herr. 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, American Institute of Aeronautics and Astronautics, 2004. (15) Xianhe Chen, Zhixun Xia, Liya Huang and Likun Ma. Energies 2016, 9(12), 1072. (16) Salil Mohan, Mikhaylo A. Trunov, Edward L. Dreizin. Combustion and Flame 2009 156, 2213-2216. (17) Richard A. Yetter, Grant A. Risha, Steven F. Son. Proceedings of the Combustion Institute 2009, 32, 1819-1838. (18) Heesung Yang, Jihyung Lee, Kyungmoo Kim and Woongsup Yoon. 47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition, Orlando, Florida, January 2009. (19) F.M.Najjar, J.P.Ferry, A.Haselbacher, and S. Balachander. J Spacecraft And Rockets 2006, 43, 1258-1270. (20) Jihwan Lim, Heesung Yang, Woongsup Yoon. 46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2010. (21) Mirko Schoenitz, Salil Mohan, Chi-Mon Chen, and Edward L. Dreizin. 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2009. (22) V. Rosenband. Combustion and Flame 2004, 137, 366-375. (23) D. S. Sundaram, V.Yang, V.E.Zarko. Combustion, Explosion, and Shock Waves 2015, 51(2), 173-196. (24) Prasanth George, Paul E. DesJardin. 42nd AIAA Aerospace Sciences Meeting and Exhibit. AIAA 2004-790.

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Energy & Fuels 1 2 Motor 3 4 5 N2 6 7 8 9 10 H2O 11 12 13 O2 14 15 16 C2H5OH/H2O 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

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Al Data Processing

Combustor H2O/CO2 ACS Paragon Plus Environment

Camera

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Energy & Fuels

ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

ACS Paragon Plus Environment

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Energy & Fuels

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

ACS Paragon Plus Environment

Page 18 of 25

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Energy & Fuels

ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

ACS Paragon Plus Environment

Page 20 of 25

Page 21 of 25 1H2 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Energy & Fuels

Mass Source, kg/s 1.5E-08 1.4E-08 1.4E-08 1.3E-08 1.3E-08 1.2巳08 1.2E-08 1.1E-08 1.1E-08 1.0E-08 9.5E-09 9.0E-09 8.5E-09 8.0E-09 7.5E-09 7.0E-09 6.5E-09 6.0E-09 5.5E-09 5.0E-09 4.5E-09 4.0E-09 3.5E-09 3.0E-09 2.5E-09 2.0E-09 1.5E-09 1.0E-09 5.0E-10

z-0.025

Angle-45 ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54

ACS Paragon Plus Environment

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Energy & Fuels

ACS Paragon Plus Environment

Energy & Fuels 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

ACS Paragon Plus Environment

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Energy & Fuels

ACS Paragon Plus Environment