The push toward the miniaturization of electromechanical devices and the resulting
need for micro-power generation (milliwatts to watts) with low-weight, long-life devices
has led to the recent development of the field of micro-scale combustion. Since batteries
have low specific energy (~200 kJ/kg) and liquid hydrocarbon fuels have a very high
specific energy (~50000 kJ/kg), a miniaturized power-generating device, even with a
relatively inefficient conversion of hydrocarbon fuels to power, would result in increased
lifetime and/or reduced weight of an electronic or mechanical system that currently
requires batteries for power.
Energy conversion from chemical energy to electrical energy without any moving
parts can be achieved by a thermophotovoltaic (TPV) system. The TPV system requires
a radiation source which is provided by a micro-combustor. Because of the high surface
area to volume ratio for micro-combustor, there is high heat loss (proportional to area)
compared to heat generation (proportional to volume). Thus the quenching and
flammability problems are more critical in a micro-scale combustor. Hence innovative
schemes are required to improve the performance of micro-combustion.
In the current study, a micro-scale counter flow combustor with heat recirculation is
adapted to improve the flame stability in combustion modeled for possible application to a TPV system. The micro-combustor consists of two annular tubes with an inner tube of
diameter 3 mm and 30 mm long and an outer tube of 4.2 mm diameter and 30 mm long.
The inner tube is supplied with a cold premixed combustible mixture, ignited and burnt.
The hot produced gases are then allowed to flow through outer tube which supplies heat
to inner tube via convection and conduction. The hot outer tube radiates heat to the TPV
system. Methane is selected as the fuel. The model parameters include the following:
diameter d , inlet velocity u , equivalence ratio àand heat recirculation efficiency ÷
between the hot outer flow and cold inner flow. The predicted performance results are as
followings: the lean flammability limit increased from 7.69% to 7.86% and the
quenching diameter decreased from 1.3 mm to 0.9 mm when heat recirculation was
employed. The overall energy conversion efficiency of current configuration is about
2.56.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4311 |
| Date | 30 October 2006 |
| Creators | Lei, Yafeng |
| Contributors | Annamalai, Kalyan |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 635041 bytes, electronic, application/pdf, born digital |
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