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Combustion Enhancement of Liquid Fuels via Nanoparticle Additions

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OBJECTIVE: Demonstrate and quantify the impact of nanoenergetic particle addition to propulsion-system fuels. Optimize particle size, passivation and loading with a focus on engine performance and initial transients. DESCRIPTION: Changing from micron-sized to nanosized energetic particles increases the reaction times and decreases the ignition delay times of the particles. In some cases improvements of several orders of magnitude can be achieved. These unique properties of nanoenergetic particles could be used to enhance the energy density of fuels used in propulsion systems. When mixed with traditional fuels such as JP-8 or RP-1 it is hypothesized that performance of turbine (fuel consumption / time on target) and rocket (ISP) engines could be improved as could the start-up transients. To date, however, such improvements have not been demonstrated and quantitative predictions have not been validated. Recent improvements in understanding the ignition and reaction mechanisms of dry nanoparticles (i.e., particles on their own without fuel added) as well as use in solid rocket motors have continued to highlight potential engine improvements and are enabling more in-depth studies at ever-more-realistic conditions. Yet, investigations of the behavior of wet nanoparticles is lacking, and the effect of the liquid on the energy release, burning rate and energy transfer speed of fuel-nanoparticle mixtures is not understood. These must be quantified to assess the efficacy of this approach to increasing the performance and start-up transients of engines. Beyond the general question of efficacy, implementation of nanoenergetic particles in combustion systems will involve optimization of particle type, size and loading; a mixing technique or demonstration that the particles remain in suspension; and perhaps alterations to current injectors to accommodate and atomize the multi-phase flow. Demonstrate the feasibility of nanoparticle additions to increase the energy density of propulsion fuels. Quantify change in combustion energy, reaction time, and/or ignition of baseline propulsion fuel (e.g., JP-8 or RP-1) versus improved fuel. The effect of particle size, droplet size, particle type, and any passivation layers should be considered along with enhancement as a function of particle loading, particle lifetime, changes in injector lifetime due to erosion and ability to maintain well-mixed conditions. Assessing all optimization parameters may be beyond the scope of this work, and emphasis will be placed on the enhancement as a function of particle size, type and loading, the impact and need for passivation layers and particle lifetime within an engine. Although aluminum nanoparticles have been extensively studied, this topic is not limited to the investigation of this single particle type. In addition to improving rocket and turbine engines, this work may be important for developing fuel additives to alter combustion products (potential reduction in harmful emissions). PHASE I: Demonstrate the feasibility of nanoparticle additives to improve the performance of propulsion system fuels. Quantify change in combustion energy and/or reaction time of typical propulsion fuels (e.g., JP-8 or RP-1) with the addition of nanoenergetic particles. The effect of nanoparticle size, droplet size and any passivation layers should be considered. Particle type may also be considered. PHASE II: Fully develop and optimize the improved fuel additive and demonstrate/quantify the enhanced performance for propulsion applications within a laboratory environment. Optimization parameters should include performance improvement and initial transients. Initial analysis for future operational transition should be considered such as engine lifetime effects, ensuring well mixed fuel, environmental/safety considerations, storage, and other such issues. PHASE III: Quantification, optimization and modeling of the effects of nanoparticles addition to fuels will enable improvements in rocket and air-breathing engines. Improvements may include increased performance or improved ignition and start-up transients. Improvements may be made in civilian jet engines. REFERENCES: 1. Jones, M., Li, C.H., Afjeh, A. and Peterson, G.P.,"Experimental study of combustion characteristics of nanoscale metal and metal oxide additives in biofuel (ethanol)", Nanoscale Research Letters, Volume 6, Number 246, 2001. Doi: 10.1189/1556-276X-6-246. 2. Levitas, V.I., Dikici, B. and Pantoya, M. L.,"Towards design of the pre-stressed nano- and microscale aluminum particles covered by oxide shell", Combustion and Flame, Volume 158, Issue 7, July 2011, Pages 14131417. http://dx.doi.org/10.1016/j.combustflame.2010.12.002. 3. Lynch, P., Krier, H. and Glumac, N.,"Micro-alumina particle volatilization temperature measurements in a heterogeneous shock tube", Combustion and Flame, Volume 159, Issue 2, February 2012, Pages 793-801. doi: http://dx.doi.org/10.1016/j.combustflame.2011.07.023. 4. Tyagi, H., Phelan, P.E., Prasher, R. Peck, R., Lee, T., Pacheco, J.R. and Arentzen, P.,"Increased Hot-Plate Ignition Probability for Nanoparticle-Laden Diesel Fuel", Nano Letters, Volume 8, Number 5, 2008, Pages 1410-1416. doi: 10.1021/nl080277d. 5. Yetter, R.A., Risha, G.A., Son, S.F.,"Metal particle combustion and nanotechnology", Proceedings of the Combustion Institute, Volume 32, Issue 2, 2009, Pages 1819-1838. doi: http://dx.doi.org/10.1016/j.proci.2008.08.013.
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