In early 2012, the Structure and Liftoff In Combustion Experiment (SLICE) was conducted in the Microgravity Science Glovebox (MSG) aboard the International Space Station . A gaseous hydrocarbon fuel (methane, ethylene, or a selected nitrogen dilution of each fuel) issuing from a small burner tube in coflowing air was ignited to form a laminar diffusion flame. As the fuel or air velocity was increased gradually, the flame base detached and lifted off the burner rim, stabilized at a new position downstream, and blew out eventually due to the finite rate of chemical reactions. In this study, the stabilizing mechanism of laminar diffusion flames has been examined further in normal Earth gravity (1g).
During the reporting period 12/13/2018 to 12/12/2019, we have performed the following tasks:
(1) By using the engineering model of the Smoke Point in Co-flow Experiment (SPICE) experiment assembly, loaned from the NASA Glenn Research Center (GRC), the stability limits (lift-off and blow-off) of laminar diffusion flames have been measured in 1g [2, 3]. The fuels are methane, ethane, ethene, propane, butane, 1-butene, 70% methane in nitrogen, and 20% ethane in nitrogen. The fuel tube inner diameters are 0.4 mm and 0.8 mm. In general, the critical fuel jet velocities at the flame stability limits are larger for a larger fuel tube diameter, for alkenes than alkanes (due to the higher reactivity), and for a lower number of carbon atoms (due to the lower fuel density).
(2) Furthermore, by using a newly fabricated experimental apparatus, the stability limits have been measured over much larger ranges of the fuel and air velocities as well as the fuel tube diameter than those of the SPICE rig. The apparatus consists of a stainless-steel fuel tube (0.4 – 3.2 mm i.d.) coaxially installed in a glass chimney (95 mm i.d.). In addition to the pure C1 – C4 hydrocarbons mentioned above, acetylene is also used as the fuel.
(3) The computation with detailed chemistry to reveal the diffusion flame structure and flame-flow interactions leading to the flame stability-limit conditions has been initiated. A chemical reaction mechanism for butane has newly been incorporated in the in-house numerical code, especially capable of simulating unsteady flame-flow interaction phenomena such as the flame stabilizing process.
1. Takahashi, F., Kulakhmetov, R., Stocker, D.P., Ma, B., and Long, M.B., Microgravity Enhances the Stability of Gas-Jet Diffusion Flames, 28th Annual Meeting of the American Society for Gravitational and Space Research, New Orleans, LA, November 28-December 2, 2012.
2. Smith, L., Souza, D., and Takahashi, F., Stabilization of Laminar Jet Diffusion Flames, 34th Annual Meeting of the American Society for Gravitational and Space Research, Bethesda, Rockville, MD, October 31-November 3, 2018.
3. Smith, L., Souza, D., and Takahashi, F., Stabilization of Laminar Hydrocarbon Jet Diffusion Flames in Earth Gravity and Microgravity, 27th International Colloquium on the Dynamics of Explosions and Reactive Systems, Beijing, China, July 28th - August 2nd, 2019.
Abstracts for Journals and Proceedings
Smith L, Souza D, Takahashi F. "Stabilization of Laminar Hydrocarbon Jet Diffusion Flames in Earth Gravity and Microgravity." 27th International Colloquium on the Dynamics of Explosions and Reactive Systems, Beijing, China, July 28-August 2, 2019.
Abstracts. 27th International Colloquium on the Dynamics of Explosions and Reactive Systems, Beijing, China, July 28-August 2, 2019. , Jul-2019