الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
An experimental work was carried out to address the combustion performance of eccentrically
rotated flames via a cam shaft mechanism. The favorable effect of the severe temporal velocity
gradient stimulated around the jet boundaries on the turbulence development for both the
premixed and the non-premixed flame modes was characterized by a variable speed of rotation
and different jet cross-sections. The use of an eccentric mechanism attached to an electrical
motor running with a variable speed continuously changes the jet exit cross-section shape such
that between the successive moments there is a shear stress generated between the different jet
velocity profiles at each instant.The shapes investigated include circular, elliptical, triangular and
rectangular cross-sections as well as a straight triple blade eccentric rotor. The latter design was
further developed to involve simultaneous rotation of both the eccentric rotor and the triple blade
around its axis via a planetary gear assembly to duplicate the stimulated vortical structure.
While non-premixed flames responded to such cyclic action by acquiring a combustion
efficiency enhancement of 21% at higher fuel burning capacities, the performance of the
premixed flames pronounced an extension of 35% in the flame stability limits under the
conditions of a non-cooled combustion chamber. Increasing the speed of rotation up to 4500 rpm
consistently enhances the mixing and the burning capacity up to a certain limit which becomes
shifted to the higher speeds at the higher firing capacities. Upon circulating a water jacket around
the combustion chamber, there was an enhancement in the convective heat transfer coefficient as
high as 28% by reaching the speed of 4500 rpm.
As computationally supported, while decreasing the jet cross-section for various eccentric shapes
led to favorable flow shearing effects, the star shape pronounced the most effective one. This
was substantiated by a reduction in the HC and CO emissions to 0.5% and 56 ppm, respectively.
Due to the reduced peak flame temperatures via the increased turbulence intensity, the NOx exhaust concentrations were greatly reduced to a peak of 17 ppm At the same perimeter/diameter ratio for the solid shapes investigated, the shapes (with sharp
corners which aerodynamically have higher drag coefficients) stimulate stronger recirculation
zones and hence better combustion. The square shape has higher drag coefficient and more
corners in comparison with the triangular shape. Both shapes acquired better combustion than the
smooth surface elliptical shape. However, as the elliptical shape is guided such that its major
diameter faces the flow, it is better than the circular one. If it is oriented such that its minor
diameter faces the flow the drag coefficient decreases and the elliptical become worse than the
circular. The increase in the difference in CO emissions between the four shapes at higher speeds
thus confirms the continuous effect of the drag coefficient at high Reynolds number.
The planetary gear design was then commissioned as a potential prototype for tuning themixing
and reaction time scales in the diffusion flame modefor industrial furnaces. A reduction of 42%
in the flame length was recorded at the maximum fuel loading conditions.In the premixed flame
mode, an extension in the lean operation equivalence ratio to 0.7was found to involve NOx
emission reduction. Much higher firing rates were obtained with the stoichiometric fuel/air
mixtures which were accompanied by a simultaneous reduction in the NOx emissions
particularly upon employing the water jacket cooling.
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