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Experiment/Payload Overview

Brief Summary

Structure and Liftoff In Combustion Experiment (SLICE) investigates the nature of flames in microgravity. The results from these experiments could lead to improved fuel efficiency and reduce pollutant emissions in practical combustion on Earth.

Principal Investigator

Marshall B. Long, Ph.D., Yale University, New Haven, CT, United States

Co-Investigator(s)/Collaborator(s)

Mitchell D. Smooke, Ph.D., Yale University, New Haven, CT, United States

Fumiaki Takahashi, Ph.D., National Center for Space Exploration Research, Cleveland, OH, United States

Dennis P. Stocker, , Glenn Research Center, Cleveland, OH, United States

Payload Developer

ZIN Technologies Incorporated, Cleveland, OH, United States

Sponsoring Space Agency

National Aeronautics and Space Administration (NASA)

Sponsoring Organization:

Human Exploration and Operations Missions Directorate (HEOMD)

ISS Expedition Duration:

March 2011 - May 2012

Expeditions Assigned

27/28, 29/30

Previous ISS Missions

ISS Expedition 29/30 is the first mission for the SLICE experiment which utilizes the existing SPICE hardware on orbit aboard the ISS.

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Experiment/Payload Description

Research Summary

• Predicting the shape and temperature of burning gases is complicated on earth by buoyancy effects. Observations of the temperature and shape of flames from burning gases in microgravity will help scientists and engineers improve fuel efficiency and reduce pollutant emissions inof practical combustion on Earth.



• The goal of the Structure and Liftoff In Combustion Experiment (SLICE) is to improve computer models of flames using the unique data that can be obtained in a microgravity environment.

Description

The SLICE experiment investigates the structure of lifting and lifted flames, where flow conditions and the combustion chemistry cause the flame to detach from the burner and stabilize at a downstream position. It is a precursor to the Coflow Laminar Diffusion Flame (CLD Flame) experiment, where the SLICE results will be used to maximize the scientific return of that upcoming space station experiment.

The SLICE objectives are to 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. SLICE also identifies the liftoff velocity limits as a function of the fuel and burner diameter, for diffusion flames of methane, nitrogen-diluted methane, and nitrogen-diluted ethylene burning in a coflow of air.

A flame of gaseous fuel is ignited within a low-speed flow duct and photographed. The fuel flow or air velocity is adjusted to assess its effect on the flame structure and liftoff. Other experimental parameters include the gaseous fuel (including nitrogen dilution) and the diameter of the circular burner tube. Flame measurements include the structure (e.g., size and shape), soot temperature, soot volume fraction, and thermal radiation. The results will be used to refine computational models of the flames.

The goal of the SLICE experiment is to improve our understanding of the physical and chemical processes controlling diffusion (i.e., nonpremixed) 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. Good agreement between experimental and computational results has been demonstrated for lifted flames at moderate flame conditions, but that agreement breaks down when the fuel is highly diluted or the soot production is high. SLICE is a precursor for the CLD Flame experiment, which is one of five experiments in the Advanced Combustion via Microgravity Experiments (ACME) project that are currently in development for conduct in the Combustion Integrated Rack (CIR). A common goal of the two experiments is to improve computational techniques such that a broader range of flame conditions can be effectively modeled than is currently possible.

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Applications

Space Applications

SLICE is not being conducted to serve any space applications, but it is possible that its findings could aid the development of future space-based combustion devices (e.g., for solid waste processing).

Earth Applications

SLICE enables improvements in the design of practical combustion devices such as engines and furnaces. The improved design capability leads to reduced time and cost for the development of new products.

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Operations

Operational Requirements

SLICE testing sessions must be conducted during periods when no reboost or docking procedures are underway on the International Space Station. If possible, the following measurements are to be made of the environment during testing: acceleration, pressure (i.e., in the MSG work volume), and oxygen concentration.

Operational Protocols

SLICE is a crew-operated experiment, where the crew first installs the SPICE hardware in the MSG work volume. The SPICE hardware consists of a small fan-driven flow duct equipped with an exchangeable burner tube and igniter. Outside of the flow duct are two cameras, the fuel supply bottle, and supporting electronics boxes. Before each test, the crewmember installs the specified burner tube and a supply bottle with the selected fuel. The astronaut then sets the fuel flow and air velocity as indicated in the test matrix and ignites the flame. A small number of flame conditions are studied in each test; the crewmember will adjust either the fuel flow or airflow to achieve different flame conditions. At each flow condition, the crewmember will photograph the flame with a high-resolution digital still camera that has been calibrated with a blackbody source, enabling determination of the soot temperature and soot volume fraction via pyrometry. The fuel flow is shut off upon completion of a test. Throughout the SLICE operations, the science team on the ground will monitor video downlink, which includes overlaid sensor data, to guide the crewmember in lifting the flame and selecting flow conditions that will yield the most useful results. The still images and data will be downlinked to the ground for analysis following each session of operations.

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Results/More Information

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Related Web Sites

SLICE

Yale

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Publications

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Ground Based Results Publications

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ISS Patent Publications

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Related Publications

• A comparison of computational and experimental lift-off heights of co-flow laminar diffusion flames Proceedings of the Combustion Institute 2005 30 357-365
• Walsh K T,Fielding J ,Long M B,Experimental and computational study of temperature, species, and soot in buoyant and non-buoyant coflow laminar diffusion flames Proceedings of the Combustion Institute 2000 28 1973-1979
• Effect of light-collection geometry on reconstruction errors in Abel inversions Optics Letters 2000 25 457-459
• Walsh K T,Long M B,Tanoff M A,Smooke M D,Experimental and computational study of CH, CH*, and OH* in an axisymmetric laminar diffusion flame Proceedings of the Combustion Institute 1998 27 615-623
• Luque J ,Jeffries J B,Smith G P,Crosley D R,Walsh K T,Long M B,Smooke M D,CH(A-X) and OH(A-X) optical emission in an axisymmetric laminar diffusion flame Combustion and Flame 2000 122 172-175
• Walsh K T,Quantitative Characterizations of Coflow Laminar Diffusion Flames in a Normal Gravity and Microgravity Environment PhD Thesis - Yale University 2000
• Smooke M D,Hall R J,Colket M B,Fielding J ,Long M B,McEnally C S,Pfefferle L D,Investigation of the transition from lightly sooting towards heavily sooting coflow ethylene diffusion flames Combustion Theory and Modeling 2004 8 593-606
• Takahashi F ,Schmoll W J,Katta V R,Attachment Mechanisms of Diffusion Flames Proceedings of the Combustion Institute 1998 27 675-684
• Brooker J E,Stocker D P,Chen L D,The Influence of Buoyant Convection on the Stability of Enclosed Laminar Flames Proceedings of the Central States Section Meeting - The Combustion Institute 1998
• Takahashi F ,Katta V R,A Reaction Kernel Hypothesis for the Stability Limit of Methane Jet Diffusion Flames Proceedings of the Combustion Institute 2000 28 2071-2078
• Takahashi F ,Katta V R,Reaction Kernel Structure and Stabilizing Mechanisms of Jet Diffusion Flames in Microgravity Proceedings of the Combustion Institute 2002 29 2509-2518
• Takahashi F ,Katta V R,Further Studies of the Reaction Kernel Structure and Stabilization of Jet Diffusion Flames Proceedings of the Combustion Institute 2005 30 383-390
• Takahashi F ,Linteris G ,Katta V R,Extinguishment of Methane Diffusion Flames by Carbon Dioxide in Coflow Air and Oxygen-Enriched Microgravity Environments Combustion and Flame 2008 155 37-53
• Venutrumilli R ,Chen L D,Comparison of Four-Step Reduced Mechanism and Starting Mechanism for Methane Diffusion Flames Fuel 2009 88 1435-1443

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Images

The lifted nature of the flames can be discerned from the outward flare of the flame base in the example images below (which are not at the same scale) and the distance from the nozzle tip (which is not visible). Picture courtesy of NASA Glenn Research Center.

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At high fuel dilutions, there is a significant discrepancy between computational results and experimental results both in microgravity and on Earth. Note that CH4 is the chemical formula for methane and N2 is the chemical formula for nitrogen (these substances are both gases at room temperature and pressure). Picture courtesy of Yale University.

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