Lean Blowout Detection Techniques for Partially Premixed Flames in a Dump Combustor - Novel Combustion Concepts for Sustainable Energy Development - page 199

fl flame dynamics observed prior to blowout. So the second objective of this study

was to characterize the combustion dynamics near LBO limit, quantify the ame

characteristics preceding to blowout in terms of LBO precursor, and further use
those precursors for LBO detection.

fl

2 Experimental Details

In the present scheme, a swirl-stabilized dump combustor has been designed and
fabricated to investigate the outlined objectives of the present study. The combustor
simulates a laboratory-scale model of a generic gas turbine combustor.
All the experiments carried out in the present study are at atmospheric pressure
condition, air is supplied at ambient temperature, the fuel primarily used is lique

ed
petroleum gas (i.e., LPG, 60 % propane, 40 % butane), and some tests carried with
fuel methane.
A swirl-stabilized dump combustor was designed as a laboratory-scale model of
a generic gas turbine combustor. The assembled view of the combustor is shown in
Fig. 2 . The combustor consists of a premixing section, the combustor, and an
exhaust chamber. All metal parts made of type SS316 stainless steel enable the
device to withstand high temperatures. All three sections are aligned coaxially.
A swirler is provided at the end of the premixing section to stabilize the reacting
mixture. The combustor design with a swirling injection of reactants and a dump
plane with rear-facing step produces a swirling fl ow field with large recirculation

zones. The global flow structure for this class of geometry is qualitatively similar,

irrespective of combustor dimensions (Williams et al. 2007 ). The combustor section
has an inner diameter of 60 mm and a length of 200 mm. This compares favorably
with an actual gas turbine combustor, the

fl

of the Rolls Royce Trent
60 DLE (a 58-MWe aeroderivative gas turbine), which is approximately 200 mm in
diameter and 700 mm long (Tomas 2005 ).
The premixing section consists of a 375-mm-long SS pipe of outer diameter
43 mm and inner diameter 23 mm. At one end of the pipe, a SS plate of 65 mm
diameter and 15 mm thickness has been welded. A 15-mm-diameter internally
threaded hole tapped into the plate serves as the air inlet. Five 6-mm-diameter holes
have been drilled on the wall of the pipe at intervals of 50 mm. The

“ combustor can ”

first hole is at a
distance of 20 mm from the upstream end of the premixing tube where plate is
welded for air inlet. These holes act as alternative positions for fuel inlet. We name
this fuel inlet ports as port 1 to port 5. Variation in the position of the fuel
inlet alters the length available for the premixing of fuel and air (characterized by
the premixing length L fuel ). This allows one to investigate the effects of extent of
fuel/air premixing on the combustion characteristics.
The swirler was constructed by placing 15-mm-long and 1-mm-thick blades on a
solid rod of diameter 8 mm at an angle of 60 ° to the axial direction. The blade

heights were such that the swirler fits snugly in the 29-mm-diameter slots in the

premixing section just prior to dump plane. The swirler is provided to add swirl in