Theoretical and Computational Studies of Nucleation in Supercritical Fuels
Abstract
The principal objective of this research is to improve basic understanding of the deposit of pyrolytic products from thermally-stressed endothermic fuels. The precipitation of picene from supercritical methylcyclohexane was investigated numerically. The calculations indicated that a negligible amount of deposits were formed as a result of friction-driven depressurization in tubular flow. However, the presence of small amounts of particulate impurities dramatically enhanced the rate of deposit formation. Mathematical models were also developed for mass transfer between droplets and a partially-miscible supercritical solvent, and for particle formation during the rapid expansion of supercritical solutions. The evolution of isolated droplets exposed to a supercritical solvent was investigated at mixture sub-critical pressures. Over a wide range of conditions the calculations showed appreciable initial droplet swelling, followed by evaporation. Aerosol dynamics equations were combined with mass, momentum, energy balances and an equation of state to yield a mathematical model for the evolution of the particle size during steady, one-dimensional friction-driven expansions of a supercritical fluid containing a dissolved solute. The calculations showed that only sub-micron particles are formed inside the tube where choked flow conditions are attained. Inter-particle coagulation in the free-jet following the expansion device is responsible for subsequent particle growth.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 28, 1999
- Accession Number
- ADA366814
Entities
People
- Pablo G. Debenedetti
Organizations
- Princeton University