AbstractA simple dynamical system that models the competitive thermokinetics and chemistry of cellulose decomposition is examined, with reference to evidence from experimental studies indicating char formation a low activation energy exothermal process volatilization high endothermal process. The thermohydrolysis at core primary competition described. Essentially, between two nucleophiles, molecule water an −OH group on C6 end glucosyl cation, form either reducing chain fragment propensity...

Abstract The theory of large activation energy asymptotics is used to model the interaction pressure disturbances characterised by different length scales with conventional flames. Byconventional flames it understood that deflagration Mach number low and order where 0 non dimensional s a positive power arising from detail (global) kinetic scheme. By denoting paper explores coupling exists between for medium short wavelengths. N in range M −l 1. work complements which has mainly been achieved...

Two-dimensional burner-flame stability is discussed with arbitrary gas expansion. Density variations are allowed for by fully coupling the continuity and momentum equations. The flame assumed to be close a porous-plug-type flameholder so that conventional hydrodynamic zone upstream of cannot included. Instead, flow obey Darcy-type law within holder, relating pressure gradient velocity. It shown influence holder acceleration due gravity important factors governing onset cellularity in...

A simple model for the thermal decomposition of amorphous cellulose is proposed that rationalizes effect water in promoting charring process at expense volatilization. Simulations mass-loss histories and product evolution are shown to be consistent with various experimental observations literature. Under char-promoting conditions where heat transfer limited, anomalous effects predicted which indicate char formation may not always desirable fire-inhibiting treatments or strategies cellulosic...

We present an analysis of instability to transverse perturbations laminar premixed plane spray flames. To this end, a thermal‐diffusional model flame front propagating through overall fuel‐rich or fuel‐lean droplet‐vapour‐air mixture is presented. The fuel droplets are permitted vaporize at finite rate so that their interaction with, and possible traversal of, the accounted for. After establishing steady‐state solutions by means high activation energy asymptotics, detailed linear stability...

ABSTRACT An investigation is made into the response of mass burning rate a premixed flame to small but sharp changes in pressure. In this paper fast time scale considered such that (K1 = thermal diffusivity, u01 1 initial velocity, l1 typical acoustic length, a01 frozen sound speed, θ nondimensional activation energy). Previous studies by author (Mclntosh 1990)and other researchers (e.g. Ledder and Kapila 1991) have case r which usual value corresponding audible resonance flames tubes,...

Abstract The stability of burner flames for arbitrary Lewis number is considered on the basis large activation energy modelling. Previous leading-order-only approaches are now extended to second order in Math (the inverse energy). assumption that unsteady perturbations small (order ε) means one must discuss distinguished limit implicit product Math. lt demonstrated here different governing equations (and particular inner zone equation) obtained two cases, θ1ε → 0 and ∞. It shown there...

We consider travelling wave solutions of a reaction–diffusion system corresponding to single-step homogeneous premixed combustion scheme competitively coupled with an endothermic reaction. Properties the reaction fronts, such as speed and burnt temperature are derived numerically over range different parameter values, those describing relative enthalpies, rates activation energies exothermic reactions. Unique shown exist for each distinct combination values. Stability analyses using both...

In this paper the combustion chamber of bombardier beetle is considered and recent findings are presented which demonstrate that certain parts anatomy in fact inlet outlet valves. particular, authors show intake exhaust valve mechanism involves a repeated (pulsating) steam explosion, principle was up till now unclear. New research here has shown characteristics ejections role important numerical simulations two-phase flow ejection cyclic water injection followed by decompression explosions...

Abstract Abstract-Three theoretical models of plane flames burning on a cooled porous-plug type flame-holder are reviewed and compared with experimentally observed relationships between stand-off distance, flame speed temperature. It is shown that for most practical burners their conductance large near adiabatic conditions, the order non-dimensional distance ceases to be 0(1), but O(ln θ) where θ activation energy.

The plane pre-mixed flame adjacent to a coplanar porous-plug type of burner is analysed with the aid large-activation energy asymptotics. It shown th at there unique relation between mass flux reactants through holder and burnt-gas temperature for given value mixture equivalence ratio. A simple linear heat-flux-temperature model flameholder introduces constant proportionality called conductance holder. has strong influence on details behaviour; in particular heat from preheat regions into...

A biomimetic study of the bombardier beetle’s explosive discharge apparatus was undertaken using numerical (CFD) modelling, first, combustion chamber, and then a scaled-up chamber with view to its application devices such as gas turbine relighters. The new findings about existence pressure release valve at exit yield clearer understanding physics mass ejection mechanism. (about 1 cm in length) is modelled by considering be filled liquid hexane which undergoes vapour explosion through exit....

This paper seeks to bring together a number of results pertaining the interaction pressure waves with premixed combustion fronts. Some earlier concerning low–speed flames and acoustics are set in context some later work, which is still being developed takes compressibility into account much greater extent. The steep drops shows possible mechanism for flame extinction, rises indicates conditions rapid acceleration fast convection–reaction driven deflagrations. work demonstrates that transient...

An original physical model of self-ignition in a combustible gas mixture containing liquid fuel droplets is developed. The are small enough for the gas-droplet to be considered as fine mist such that individual droplet burning subsumed into well-stirred, spatially invariant approximation. A classical Semenov-type analysis used describe exothermic reaction, and endothermic terms involve use quasi-steady mass transfer/heat balance Clausius-Clapeyron evaporative law. resulting predicts ignition...

The importance of vorticity production in combustion systems has been highlighted previously by several authors (Markstein 1964; Picone et al. 1984). consequent distortion and enlargement flame surfaces can lead to substantial enhancement the burning rate which may be beneficial or disastrous depending on physical context. We describe results numerical simulations an experimental configuration similar that described Scarinci & Thomas (1992), who examined effect initially planar pressure...

We consider the propagation of a combustion front resulting from gasless condensed state fuel. The front, essentially premixed laminar flame, is supported by an exothermic reaction subject to possible heat loss through competitive endothermic reaction. dynamics process inducing strongly depend on temperature and local fuel concentration. Through analysis based high activation energy, steady-state values final burnt as well burning velocity are obtained, control parameters identified. Using...

Abstract This paper addresses the effect of general Lewis number and heat losses on calculation combustion wave speeds using an asymptotic technique based ratio activation energy to release being considered large. As loss is increased twin flame emerge (as in classical large analysis) with extinction loss. Formulae for non-adiabatic speed are found which apply over a wider range energies (because nature asymptotics) these explored moderate cases—the latter representing progress solid. Some...