Kumar Ramohalli

A Theoretical Heterogeneous Model of Wood Pyrolysis

Abstract A model is developed for the pyrolysis and combustion of wood, explicitly including the fibrous heterogeneity of the substance. The heterogeneity enters the equations through the fiber diameter and the interfiber material treated as undergoing charring. The emphasis is on the condensed phase. The vapor phase details are not included in this paper. The energy flux needed to drive the pyrolysis is externally prescribed; an externally heated slab or a slab burning under its own flame resulting from the products of pyrolysis mixing with an oxidizer (air) provide two examples. The method of matched asymptotic expansions is used to analytically derive a closed form expression for the time independent rate of regression of the charring plane, including the nonlinear Arrhenius degradation term for the pyrolysis. The differences between predictions from previous homogeneous models and this heterogeneous model are discussed. Some remarks concerning the apparent negative temperature rate region indicated by...

Experimental Augmentation of Turbulent Flames Through Free Radicals Delivered In Situ

Abstract Experiments are conducted with the aim of augmenting turbulent flames with specific applications to high-speed combustion (for example, Scramjets). Augmentation includes extension of rich and lean limits, extension of aerodynamic limits, and augmentations in efficiency (also, signature minimization). While the concept of free radicals use for these purposes is NOT new, the method of delivery is. Free radicals are very short lived and highly reactive; they are needed in small concentrations at specific sites at requisite times. We use stable compounds that are known to decompose at specific temperatures; their decomposition products are rich in specific free radicals that are delivered in situ. The method thus obviates the problems of storage, delivery, and loss. A methane/enriched-air turbulent flame system is used. The apparatus and flame studies have been extensively reported in the open literature. Dilute hydrogen peroxide is used as the free radicals source. The flame blow-off limit is determ...

Economical in-situ processing for orbital debris removal

Abstract This paper proposes and develops the first description of a novel concept for the removal of large pieces of orbital debris; removing the large ones prevents the future formation of innumerable smaller ones. After a brief discussion of the growing importance of the general problem of orbital debris, the idea of utilizing local resources for clearing the debris is introduced. The fundamental concept revolves around the collection of solar energy via high-tech, light-weight, thermally stable reflectors; concentrating the radiation into highly focused beams; and carefully cutting the debris into accurate pieces that can be further used by the processing craft itself. The unusable parts are stowed behind the reflecting surfaces. At the end of these operations, the craft, with the collected debris, can process itself into a specific “shape” depending on the final disposal mode-either retrieval by the shuttle, splashdown into the ocean, or re-entry for burnup. The propulstion requirements are shown to be reasonable, through three very specific examples, using a quantitative computer animation. A description of the initial (manual, at this stage) terrestrially working hardware and future projections for this Autonomous Space Processor for Orbital Debris conclude this paper.

Thermochemical Response of Honeycomb Sandwich Panels

A simple study aimed at predicting the Thermochemical Response of honey comb sandwich panels is presented. The overall thermal conductivity coefficient for the panel is obtained through a consideration of the convective gas move ment within the cell spaces. The earlier correlations of Catton and Edwards are used. The analytical solution for the one-dimensional approximation is quoted from an earlier study.