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The vegetable oil, as a biofuel,
may be used in
vegetable oil fuel
combustors integrated in
portable bioenergy technologies for home-heating, in
large scale
bioenergy steam generators, and even used directly as auto-fuel.
However, the
viscosity of vegetable oil is relatively higher than suitable for most
combustion operations.
Biodiesel produced from vegetable oils tend to have much lower
viscosity and as such also better flow properties. Therefore, the use of
biodiesel in combustion technologies in substitution
for pure
vegetable oils is preferable; and the development of combustion
technologies specifically for biodiesel also taking advantage of the
fluid and thermodynamic properties of the biodiesel is also
preferable, as is performed.
Although the combustion of
biodiesel can be effected within a
vegetable oil fuel
burner, or the
alcohols fuel burner in consistence with the base
biofuels
combustion technology design, the combustion technology
of analysis takes advantage of the salient property of biodiesel:
the property of detonation under pressure - a property that also
characterizes diesel fuel as well. Such as combustor has clear
advantages over the other combustor technologies in that the issue
of flame outs are eliminated, as the combustion does not depend on a
flame. All the same, the technology is still derivative of the base
biofuel combustion technology design-rationale.
A reference technology of
compressive combustion from which thermodynamic conditions of
detonation can be abstracted is the compressive detonation of
diesel in engine cylinders. In such designs diesel and even
biodiesel are injected into the cylinder, mixed with air and then
subjected to rapid compression with a piston that simply ultimately
causes detonative combustion of the fuel vapour- air mixture, when
the pressure reaches the Compressive Detonation Pressure, CDP.
As with the base
technology, effectively, the primary
equipment for the biodiesel fuel combustor consists of three
integrated components:
- Fuel Combustion Detonator
- Fuel Burner Base (or
Enclosure)
- Combustion Chamber
but with modification of the
burner into a detonator, and which are interfaced with secondary
accessorial equipment, a Biodiesel Delivery System, consisting of
Storage Tank, a small pump. The Storage Tank should have a
well-regulated heating
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system that supports
real-time temperature measurement control system, and allows
functionality for variable temperature setting. The pump should also
be fitted with real-time control to initiate pumping only with
biodiesel available in the Storage Tank. Of course, presuming the
biodiesel as being well-filtered, or made from
algal oil, the biodiesel is pumped into the Fuel Burner Base.
The Fuel Combustion
Detonator is a use-specific customized variant of the
fuel combustion
burner technology of the base combustion technology. The salient
customizations is that the fuel handling should address injection of
biodiesel into the Combustion Chamber; and to that end the otherwise liquid atomizer
fuel-feed line-tube is now fitted with a Impulse Pressure Injector: A
mechanical cylindrical device that axially shoots liquid from one end to the
other when subjected to axial pressure, and that allows fluid to
only flow only in the direction to the atomizer. Further, under this state
design the atomizer
is replaced with a pin-hole nozzle. The time interval between
injections controls the size of the liquid droplet. The higher the
frequency the smaller the size. Further the larger the size of the
droplet the higher the injection shooting velocity.
Drawing from that cylinder-piston
technology but absent of a piston in the base combustion technology
on which the biodiesel combustor is based, the basic object
then is to bring the fuel droplet(s) discharged into the combustion
chamber to become subjected at some point after being discharged to
pressure that equals the CDP, Compressive Detonation Pressure.
Clearly within the context of the architecture of the base
combustion technology, the task is most effectively accomplished
with the implosive pressure attending impulse energy dissipation.
The dynamics is simple, upon
rapid injection the fuel droplet comes to a quick stop thereby
converting all the impulse energy into static pressure which in
combination with the [carefully pre-calculated and established -
this condition should be fairly difficult to support without a
computation-intensive system for pre-analysis] chamber pressure
initiates an implosive compressive detonation.
The Fuel Burner Base (or
Enclosure) has two inlet
ports: fuel inlet port, and air-inlet port, as with the vegetable
oil fuel burner, and nothing else. However, the casing of the Fuel
Burner Base must be such as to support high pressure operation: The
use of the pressure to control the Impulse Pressure Injector makes it necessary to operate the Fuel Burner at
relatively higher pressure.
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The Combustion Chamber for a
simple Burner suffers very little customization from the chamber for
the vegetable oil fuel burner. A reasonable customization may simply
aim to have the chamber constructed as to withstand the implosive
detonation force of the fuel droplets.
This particular design also
adapts very well for use in turbine-based impulse detonation
combustors of biodiesel.
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