About the SLICE Logo
Measured and computed temperature profiles of coflow laminar diffusion flames of 65% methane and 35% nitrogen in both normal gravity and microgravity.See large image for a side-by-side comparison. (Yale University)
October 2011 – The Capillary Channel Flow (CCF) experiment
has been completed and the Microgravity Science Glovebox (MSG) is now
being used for investigations using the Selectable Optical Diagnostics
Instrument (SODI). SLICE operations will follow both SODI and the
launch of astronaut Don Pettit and are still expected to occur in January-February
2012 (during Increment 30).
September 2011 – SLICE operations are approaching, and will follow (in order) the CCF, SODI-Colloid, and SODI-DSC experiments in the Microgravity Science Glovebox (MSG). It is currently anticipated that SLICE will begin in January 2012, in which case the experiment will be conducted by astronaut Don Pettit. Final SLICE operations (tentatively in February 2012) will include some tests for the Smoke Point In Coflow Experiment (SPICE).
July 2011 - The SLICE
hardware launched in February 2011 on STS-133/ULF-5 and is currently
on board the International Space Station (ISS). Astronauts Joe
Acaba, Mike Fossum, Ron Garan, Don Pettit, and Suni Williams have been
trained for the experiment. Although Garan and Fossum are both
now on the ISS, the facility in which SLICE will be conducted, i.e.,
the Microgravity Science Glovebox (MSG), is being used for other experiments. It
is currently expected that SLICE operations will begin in early 2012
(or perhaps late 2011) where that timing will determine which astronaut(s)
conduct the experiment. SLICE operations should last approximately
two months, after which the MSG will be used for the Burning
And Suppression of Solids (BASS) experiment.
Coflow laminar diffusion flames are especially valuable for studies of combustion because of the availability of accurate numerical modeling with that flame configuration. In particular, excellent agreement can be achieved when the flow conditions are such that the flame detaches and lifts above (i.e., moves downstream of) the nozzle. A coupled experimental and numerical investigation can enable validation and improvements to combustion modeling. For example, the image to the right is not a photo, but a numerical simulation of a 40% ethylene flame. Enhanced modeling capability is important because it can reduce time and cost in the design of practical combustion devices. Furthermore, flame attachment to (or detachment from) a burner or condensed-fuel surface is of essential importance in both combustion systems and fire safety. The flame attachment point controls the stability of the entire trailing diffusion flame.
Microgravity testing allows for greater temporal and spatial scales and a broader range of flame characteristics than can be achieved in normal gravity. As one example of the NASA-recognized value of such studies, the Coflow Laminar Diffusion Flame (CLD Flame) experiment of Marshall B. Long and Mitchell D. Smooke (both of Yale U.) is currently in development for conduct in the Combustion Integrated Rack (CIR) on the International Space Station, as part of the Advanced Combustion via Microgravity Experiments (ACME) project.
The overall goal of the proposed study is to improve
our understanding of the physical and chemical processes controlling
diffusion (i.e., non-premixed) flame structure and lifting phenomena
(i.e., stabilization) and to provide for rigorous testing of numerical
models, including thermal radiation, soot formation, and detailed chemical
kinetics. As part of this aim, an important purpose of the SLICE
investigation is to conduct preliminary microgravity studies that will
maximize the scientific return of the subsequent CLD Flame experiment
and mitigate associated risks. In other words, SLICE is
a precursor to the CLD Flame experiment.
For diffusion flames of methane, ethylene, and selected
nitrogen dilutions of each fuel burning in a coflow of air:
(1) Characterize the structure of the flame, especially its base (i.e., stabilizing region), from attached through lifted conditions as a function of the fuel, burner diameter, and flow conditions.
(2) Identify the liftoff velocity limits as a function of the fuel and burner diameter.
The experimental hardware for the Smoke Points In Co-flow Experiment (SPICE), of David L. Urban (NASA Glenn) and Peter B. Sunderland (U. Maryland), which is currently onboard the International Space Station, was built to allow studies of coflow laminar diffusion flames. The SPICE hardware is within the ISS MSG in the image to the right. While the SPICE investigation has been specifically focused on a study of soot production and oxidation within flames, the hardware can be used without modification to conduct the SLICE experiment. In terms of the experimental hardware, the only additional requirements for SLICE are more fuel (i.e., gas bottles), recording media, and minor hardware elements such as new nozzle(s). The three existing SPICE nozzles are all smaller than the nozzle planned for the CLD Flame experiment. Of course, the SLICE testing could most benefit the CLD Flame experiment by bracketing and/or including the same nozzle size. It is also possible that screen(s) would be flown to alter the velocity profile of the coflow.
The SLICE operating procedures will have some differences
to the standard SPICE procedures given the differing objectives. However,
those changes are fully within the capabilities of the SPICE hardware,
as demonstrated by exploratory testing that has already been conducted
on orbit. As a simple example, the standard SPICE procedure calls
for a fixed air velocity and an increase of the fuel flow until the
smoke point is reached. In contrast, SLICE will include testing
where the fuel flow is fixed and the air velocity is incrementally
increased until the diffusion flame detaches and lifts off from the
nozzle. In all cases, still and video measurements of the flame
structure will be made for comparison with detailed numerical computations. Given
that the capture of the lifting processes in normal gravity is extremely
difficult, SLICE will provide valuable photographic observations on
the transient flame behavior.
Principal Investigator (PI): Prof.
Marshall B. Long, Yale University
Co-Investigators (Co-Is): Prof. Mitchell D. Smooke, Yale University
Dennis P. Stocker, NASA Glenn
Dr. Fumiaki Takahashi, NCSER @ NASA Glenn
NASA Technical Contact: Dennis P. Stocker, NASA Glenn