Simplified computational model of a single hydrogen injector used with the NCC.
Long description of figure 1.
Hydrogen, in the gas state, has been proposed to replace Jet-A (the fuel used for commercial jet engines) as a fuel for gas turbine combustion. For the combustion of hydrogen and oxygen only, water is the only product and the main greenhouse gas, carbon dioxide, is not produced. This is an obvious benefit of using hydrogen as a fuel. The situation is not as simple when air replaces oxygen in the combustion process. (Air is mainly a mixture of oxygen, nitrogen, and argon. Other components comprise a very small part of air and will not be mentioned.) At the high temperatures found in the combustion process, oxygen reacts with nitrogen, and this produces nitrogen oxide compounds, or NOx--the main component of atmospheric smog. The production of NOx depends mainly on two variables: the temperature at which combustion occurs, and the length of time that the products of combustion stay, or reside, in the combustor. Starting from a lean (excess air) air-to-fuel ratio, the goal of this research was to minimize hot zones caused by incomplete premixing and to keep the residence time short while producing a stable flame. The minimization of these two parameters will result in low-NOx hydrogen combustion.
Temperature contours of the single injector model computed with the NCC. Top: Symmetry plane x. Bottom: Symmetry plane y.
Long description of figure 2.
Computational grid of the multi-injector model used with the NCC.
Long description of figure 3.
The hardware that actually creates the low-NOx combustion process is the injector. The National Combustion Code (NCC, ref. 1) was used to conduct numerical studies of hydrogen combustion. The code was enhanced to include a generalized wall function (ref. 2), which represented the underlying injector flow physics better than the original wall function. This research was conducted in three stages: a validation stage (ref. 3), a detailed study of the mixing inside a single injector element (ref. 4), and the study of an array of injector elements. Detailed results were presented about the mixing of fuel and air, flame structures, and combustion species. This numerical information has assisted an ongoing experimental study of hydrogen/air injection concepts. This research effort was an in-house effort of NASA Glenn Research Centerís Combustion Branch and the Ohio Aerospace Institute (OAI).
Temperature and NOx contours computed with the NCC.
Long description of figure 4.
Find out more about this research.
Glenn contact: Anthony C. Iannetti, 216-433-5586, Anthony.C.Iannetti@nasa.gov
Ohio Aerospace Institute (OAI) contact: Andrew T. Norris, 440-962-3071, Andrew.T.Norris@grc.nasa.gov
Authors: Anthony C. Iannetti, Tsan-Hsing Shih, and Andrew T. Norris
Headquarters program office: Aeronautics Research
Last updated: July 19, 2005 9:42 AM
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