A numerical study of ignition in the supersonic hydrogen/air laminar mixing layer

M. Nishioka, C. K. Law

Research output: Contribution to conferencePaper

4 Scopus citations

Abstract

The ignition evolution in the supersonic nonpremixed hydrogen/air laminar mixing layer, consisting of a relatively hot, fast air stream next to a cold, slower hydrogen stream, was computationally simulated using detailed transport and chemical reaction mechanisms, and compared with results from asymptotic analysis with reduced mechanisms. The study emphasizes on identifying the controlling chemical mechanisms in effecting ignition, on the relative importance of external versus viscous heating as the dominant ignition source, on the roles of thermal versus kinetic-induced ignition in which heat release and hence nonlinear thermal feedback are not needed in initiating system runaway, and on the consequences of imposing the conventional constant property assumptions in analytical studies. Results show that the state of the hydrogen/oxygen second explosion limit has the dominant influence in the system response in that, for all practical purposes ignition is not possible when the air stream temperature is lower than the crossover temperature, even allowing for viscous heating. On the other hand, when the air stream temperature is higher than the crossover temperature, the predicted ignition distance indicates that ignition is feasible within practical supersonic combustion engines. Furthermore, for the latter situations, the ignition event is initiated by radical proliferation and hence runaway instead of thermal runaway. Finally, it is shown that, while the present computed results qualitatively agree well with those from the asymptotic analysis with reduced mechanisms, the analytically-predicted ignition distances are much shorter than the computed values because the analysis has overemphasized the viscous effect through the constant pμ and unity Prandu number assumptions.

Original languageEnglish (US)
StatePublished - 1995
Event33rd Aerospace Sciences Meeting and Exhibit, 1995 - Reno, United States
Duration: Jan 9 1995Jan 12 1995

Other

Other33rd Aerospace Sciences Meeting and Exhibit, 1995
CountryUnited States
CityReno
Period1/9/951/12/95

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Aerospace Engineering

Fingerprint Dive into the research topics of 'A numerical study of ignition in the supersonic hydrogen/air laminar mixing layer'. Together they form a unique fingerprint.

  • Cite this

    Nishioka, M., & Law, C. K. (1995). A numerical study of ignition in the supersonic hydrogen/air laminar mixing layer. Paper presented at 33rd Aerospace Sciences Meeting and Exhibit, 1995, Reno, United States.