Thermal stability and decomposition of diesel fuel under subcritical and supercritical conditions

A novel concept of clean diesel combustion using supercritical fluids is proposed and being investigated to address some key challenges encountered in the fuel and transportation sector. The core of this concept is to inject diesel fuel (DF) in the supercritical state to achieve clean, high-efficient combustion in diesel engines. Among other challenging issues that must be addressed for the implementation of this new concept is the thermal stability of DF and the potential decomposition and solid deposit formation under engine conditions. In this work, thermal stability of DF was experimentally evaluated under subcritical and supercritical conditions in both static (batch system) and dynamic (continuous flow system) thermal stressing systems. The effects of thermal stressing temperature (200-440 oC) and duration (10-600 min) and CO2 concentration (~10 wt%) were examined. DF decomposition is characterized by the average absolute deviation (AAD) of GC peak area percentages of all individual components. A temperature-time window (400-420 2 oC, 0-60 min) where supercritical DF combustion in diesel engines may be possible was determined. CO2 as a diluent could prevent or reduce accumulation of solid deposits inside fuel pipes mainly due to an increased solubilization capacity of DF. Finally, different structures and morphologies of solid deposits observed under different batch thermal stressing conditions were discussed

Determination of Particle Size Distributions from Acoustic Wave Propagation Measurements

The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley @J. Acoust. Soc. Am. 51, 1545 ~1972!# for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations

Tritium Specific Adsorption Simulation Utilizing the OSPREY Model

During the processing of used nuclear fuel, volatile radionuclides will be discharged to the atmosphere if no recovery processes are in place to limit their release. The volatile radionuclides of concern are 3H, 14C, 85Kr, and 129I. Methods are being developed, via adsorption and absorption unit operations, to capture these radionuclides. It is necessary to model these unit operations to aid in the evaluation of technologies and in the future development of an advanced used nuclear fuel processing plant. A collaboration between Fuel Cycle Research and Development Offgas Sigma Team member INL and a NEUP grant including ORNL, Syracuse University, and Georgia Institute of Technology has been formed to develop off gas models and support off gas research. This report is discusses the development of a tritium specific adsorption model. Using the OSPREY model and integrating it with a fundamental level isotherm model developed under and experimental data provided by the NEUP grant, the tritium specific adsorption model was developed

Acoustic Monitor for Solids and Gas Measurements at Low Volume Fractions

This presentation was given at the DOE Office of Science-Environmental Management Science Program (EMSP) High-Level Waste Workshop held on January 19-20, 2005 at the Savannah River Site

Acoustic Probe for Solid-Gas-Liquid Suspensions

The proposed research will develop an acoustic probe for monitoring particle size and volume fraction in slurries in the absence and presence of gas. The goals are to commission and verify the probe components and system operation, develop theory for the forward and inverse problems for acoustic wave propagation through a three phase medium, and experimentally verify the theoretical analysis. The acoustic probe will permit measurement of solid content in gas-solid-liquid waste slurries in tanks across the DOE complex