Engineering topics
Publications and source records attributed to Bellan, J..
A model is presented for the electrostatic dispersion fo a polydisperse cluster of evaporating drops embedded into an inviscid vortex.
A detailed mathematical model is presented for the temporal and spatial accurate modeling of solid-fluid reactions in porous particles for which volumetric reaction rate data is known a priori and both the porosity and the permeability of the particle are large enough to allow for continuous gas flow.
A method is presented for an accurate noniterative, computationally efficient calculation of high pressure fluid mixture equations of state, especially targeted to gas turbines and rocket engines. Pressures above 1 bar and temperatures above 100 K are addressed. The method is based on curve fitting an effective reference state relative to departure funcitons formed using the Peng-Robinson cubic state equation. Fit parameters for H(sub 2), O(sub 2), N(sub 2), propane, n-heptane and methanol are given.
A numerical study is performed in order to assess the performance of biomass pyrolysis reactors which utilize direct particle-wall thermal conduction heating. An idealized reactor configuration consisting of a flat-plate turbulent boundary layer flow with particle convection along the heated wall and incorporating particle re-entrainment is considered.
A model describing external sheet combustion of a cluster of drops has been developed for clusters of binary-fuel drops.
Tar yield and collection from the pyrolysis of relatively larg eparticles of biomass are investigated using the model of Miller and Bellan (199b). A variety of feedstocks are considered by varying the ratios of cellulose, hemicellulose and lignin within the biomass. Effects of secondary tar reactions, quenching, temperature, particle size and carrier gas are assessed.
The pyrolysis of general biomass materials is modeled via a superposition of cellulose, hemicellulose an lingnin kinetics. All three of the primary biomass components are modeled with multi-step kinetics involving both competetive primary pyrolysis and secodary tar decomposition reactions. Only typical (untreated) feedstocks are considered at atmospheric pyrolysis pressures.
A review is presented of modeling work relevant to evaporation and combustion in liquid rocket engine chamber. Highlights of models describing evaporation, ignition, and combustion of clusters of binary-fuel drops are discussed along with strategies for using these models to construct a model of a liquid rocket combustion chamber.
Concern regarding the efficiency, stability and safety margins of bi-propellant combustion in rocket engines has prompted the investigation of many specific aspects of spray evaporation, ignition and combustion previously not studied. The phenomenology of bi- propellant spray evaporation, ignition and combustion in a highly turbulent environment at elevated pressure is discussed.
Most fuels used in practical combustion liquid-fuel sprays devices are blends of several components. In many cases, the composition of the fuel is considered critical for the operation of the device due to efficiency and pollution production considerations. This investiga- tion focuses on cluster flames for binary-fuel drops. Studied are spherical clusters of relatively cold drops exposed to an axial flow.
Evaporation and ignition of a binary-fuel cluster of drops is described by models under the.
Collective drop behavior is encountered in sprays produced for a variety of applications. The existence of clusters of drops indicates that the interaction among the drops is important in determining the dynamics of the drops because the drop proximity changes the flow around the individual drops in a way that affects the drag on each drop. Additionally, if there is a phase change between the liquid drops and the gaseous surroundings (either evaporation or condensation), this will also influence the flow around the individual drops; and phase change is also affected by the drop proximity. What will be discussed are studies of collections of drops where the dynamics and thermodynamics of the drops are coupled. This means the modification of the drag force due to the drop number density, the evaporation rate and the slip velocity are all taken into account. In turn, the enhancement in the evaporation rate due to the slip velocity , and the hindering of evaporation due to the drop proximity are also part of the models.
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A formulation has been developed which combines the simplicity of an experimentally-derived well-established correclation for describing the development of a mixing layer, and a rigorous approach for the description of the dynamics and evaporation of dense or dilute clusters of drops in large coherent vortices.
A model has been developed to describe the dynamics and evaporation of polydisperse collections of liquid drops in an axisymmetric, infinite, cylindrical vortex. This formulation is valid both in the dense regime, where interactions between particles are important, and in the dilute regime, where interactions between particles are not important. In contrast to the standard way of discretizing polydisperse collections of particles, where the initial size distribution is partitioned into a finite number of bins and these bins are fixed during the calculation, here it is only the initial size distribution which is partitioned into a finite number of sizes. Each initial size class thus defined is followed dynamically and thermodynamically in its own system of coordinates which moves with the drops. Therefore, each initial size class develops a continuum of sizes as the drops are centrifuged towards the hotter ambient and evaporate. The gas phase is followed in its own system of coordinates.
A model has been developed, which describes the evaporation, ignition, combustion of a drop cluster embedded in a large vortex. The purpose of this model is to simulate the behavior of drops in large coherent vortices produced in the shear layer of a jet.
A model is formulated in order to simulate the development of a sheer layer between a flow of air and a flow of fuel drops in a carrier gas. A characteristic feature of this type of flow is the interaction between the drop and the large-scale vortices produced the shear layer.
A model has been developed which describes the evaporation, ignition and combustion of a drop cluster embedded in a large vortex. The purpose of this model is to simulate the behavior of drops in large coherent vortices produced in the shear layer of a jet. The model treats the dynamic interactions between the drops and the vortex, and also takes into account the drop proximity to calculate the heat and mass transfers between drops and ambient gas. The gas phase outside the cluster is treated as an unsteady, reacting phase, whereas quasi-steadiness is assumed between the drops and surrounding gas inside the cluster. The results show a very complex interaction between the dynamics of the drop-loaded vortex, the flame, and the evaporation process.