Joseph F. Merklin

Application of photon correlation spectroscopy to flowing Brownian motion systems

In this paper we study the application of photon correlation spectroscopy to a system of randomly diffusing particles suspended in a fluid undergoing uniform translational motion relative to the optical scattering volume. To do so we derive theoretical expressions for both the homodyne and heterodyne correlation functions in both the dilute and nondilute particle limits. We then test these results with experiments on a flowing system and find good agreement. We discuss a useful method of analysis and define limits to particle sizing in such a system using this light-scattering technique.

Soot particle size distribution measurements in a premixed flame using photon correlation spectroscopy

We have measured the first two moments of the soot particle size distribution in premixed methane/oxygen flames using the dynamic light scattering technique, photon correlation spectroscopy. Measurements were performed in a flat flame burner as a function of fuel-oxidizer equivalence ratio and height above burner. We demonstrated the ability of photon correlation spectroscopy to extract two moments, the most probable radius r0, and the geometric width σ of an assumed zeroth-order lognormal distribution. We found that the geometric width σ decreased with increasing height above the burner. Values for number density and total soot volume were also obtained. We discuss benefits of and problems with the measurement technique.

Photon correlation spectroscopy used as a particle size diagnostic in sooting flames.

The feasibility of using photon correlation spectroscopy for the determination of particulate size in flames is demonstrated. The advantages of PCS include negligible perturbation of the system, real time analysis, and in situ measurements of particle sizes. (AIP)

Chemical and Optical Probing of Premixed Methane/Oxygen Flames

Abstract We have measured the concentration profiles of the major products in fuel-rich pre mixed CH4/O2 flames. Optical measurements were performed to measure soot number densities, volume fraction and particle size distributions. We have shown that the increase in the soot volume fraction is due to surface growth and that acetylene is the source of the carbon involved in this process. We have also been able to determine the importance of coagulation versus surface growth in the increase of soot particle radius with time in these flames.

The radiolysis of dodecane-tributylphosphate solutions

Abstract Tributylphosphate (TBP), dodecane, and mixtures of TBP and dodecane were irradiated at an absorbed dose rate of about 5.0×10 16 eV/g · min with absorbed doses of 6.1×10 18 eV/g to 1.75 × 10 20 eV/g. The irradiated samples were analyzed for gaseous products noncondensible at 161 K and acid products from TBP. The gaseous products observed were hydrogen and methane and the acid products were dibutyl phosphate (DBP) and monobutyl phosphate (MBP). The average yield of hydrogen from dodecane was, G (H 2 ) = 6.71, G (H 2 ) from TBP was 2.02, and G (acid) from TBP was 3.71. Deviation from mixture law was observed for the yields of hydrogen and acid products for the mixtures of TBP and dodecane. Sensitized decomposition of TBP is indicated.

Determination of the relative number distribution of particle sizes using photon correlation spectroscopy

We investigate the determination of relative number distributions of particle sizes using photon correlation spectroscopy (PCS). To distinguish our work from earlier results, we have studied the extraction of the number distribution, relative number as a function of size, from the intensity distribution, relative scattered intensity vs size, and set limits on its usefulness. Expressions relating the scattered intensity distribution to the number distribution are presented. These results are connected to the output of two common PCS analysis techniques, the method of cumulants, and the inverse Laplace transform. These results are tested, and limits are set by generating a synthetic intensity autocorrelation function from a known number distribution and comparing the recovered number distribution to the input. We find good agreement for distributions narrower than a geometric width of 1.40.

The influence of oxygen and total pressure on the surface oxidation rate of bituminous coal

The intrinsic reaction rates of several bituminous coals and a carbon black have been studied over a range of particle temperatures (1700–2200 K), total gas pressures (5.5–10 atm) and oxygen mole fractions (0.1–0.5) in a conventional shock tube. The surface reaction rates (based on external surface area) of the coals were observed to vary inversely with total pressure while no such dependence was noted for the carbon black. In conjunction with observations of reducing diameter burnout mode and large surface reaction rate Arrhenius activation energies, these results suggest the existence of a roughsphere kinetics regime. The true reaction order with respect to oxygen partial pressure measured at constant gas temperature is observed to be nearly 1/2; however, correction for the accompanying increase in particle temperature reduces the overall order to about 1/5. The true activation energies for both coals are about 34 kcal/mole over the temperature range studied. When corrected for pore penetration, the intrinsic reaction rates of the coals are observed to be greater than those measured for the carbon black and those predicted by a recent correlation in the temperature range of 1500 to 2100 K.

Design of an in-core fast neutron generator

Abstract A device is described to convert thermal reactor neutrons to 14 MeV neutrons, via the reaction sequence 6 Li(n,α)T-D(T,n) 4 He, in a solution of LiOD in D 2 O. The devices conversion efficiency was 1.93 × 10 −4 , i.e., for every 5200 thermal neutrons absorbed, one 14 MeV neutron was produced. Flux profiles above various threshold energies are given for the device when located in an outer ring fuel element position of the KSU TRIGA Mark II nuclear reactor. Use of the LiOD converter in fast neutron-activation analysis and CTR-materials damage studies is suggested.

The radiolysis of decalin-TBP solutions

Abstract We have investigated the radiolysis of decalin-tributylphosphate (TBP) solution and found a sensitized decomposition of the TBP.

Formation and destruction of H2S in the short residence time pyrolysis of pulverized coal and model compounds

Abstract The evolution of sulphur as H2S from three US bituminous coals, L-cystine, and thianthrene has been studied in the reflected shock region of a chemical shock tube. With heating rates of approximately 3 × 106Ks−1, to temperatures in the range 1000–2000K, ultimate yields of sulphur from 7 to 70% as H2S are observed in as little as 1.5 ms. The most important influence on ultimate yields may be the H/S molar ratio in the fuel which corresponds in the hydrocarbons studied with the H2S yields. Inherent mineral matter may also influence the evolution, as H2S formation precedes light hydrocarbon formation from the two model compounds, but occurs nearly simultaneously from the coals. The overall rate of H2S formation for the three coals is adequately described by a reaction, first order with respect to remaining sulphur, with a rate constant k=8.1 × 10 7 exp (− 15 960 T ) s −1 . In the pyrolysis of all five solids, the H2S yields are decreased to below detectable limits at temperatures >1500K. The path for destruction of the H2S appears to be by reaction with hydrocarbons such as C2H2, the concentration of which becomes similar to the H2S concentration in the temperature range 1500–1600K.