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In this paper we will describe the development of new plasma-flame facility for investigating the effects of high-voltage, nanosecond-duration plasma discharges on moderate-to-high temperature fuel oxidation and reaction chemistry present under combusting conditions. The plasma-flame facility has two operating configurations including (1) “upstream plasma generation”, where the discharge is initiated upstream of the higher temperature regions and the newly formed excited-state species and radical convect upwards towards the flame. (2) “directly-coupled” configuration, where the entire flame, including the preheat zone, reaction zone, and product zone, are encapsulated within the plasma discharge. We describe the system performance to date, including plasma uniformity, minimal Joule heating, and an initial characterization of the effects of the plasma discharges on the reaction chemistry.

We are applying Reaction Mechanism Generator (RMG) to detailed and comprehensive characterization of JP-10 combustion chemistry. JP-10 is a large synthetic fuel with complex high temperature decomposition chemistry for which detailed characterization has been considered intractable; and RMG is a computer program that we developed for automatic construction of predictive kinetic models. In this paper, we present initial results from applying RMG to JP-10 combustion. After considering over 25,000 possible species and more than 1 million possible reactions, we have developed a highly detailed JP-10 combustion mechanism that currently consists of 317 chemical species and 7,715 elementary reactions. Comparisons against existing mechanisms and experimental data in published literature reveal that this RMG-constructed mechanism establishes a new state of the art in JP-10 combustion modeling: ignition delay predictions accurately reproduce experimental observations (to our knowledge, the first detailed mechanism to accomplish this); and our mechanism provides the first detailed insight into the high temperature initial decomposition chemistry of JP-10 in the presence of oxygen, particularly down to C5 hydrocarbons. We are also developing transport property estimates for all species in the mechanism. The final result of this effort will be an experimentally validated comprehensive JP-10 combustion mechanism containing all parameters necessary for application in reacting flow simulations.

Reduced chemical kinetic mechanisms for combustion of ethylene and n-heptane have been implemented into the VULCAN CFD code and used for simulations of a 3-D scramjet flameholder. A reduced mechanism for JP-8 has been created, implemented into VULCAN and used to model a 2-D supersonic flame. The reduced mechanisms have been created using the CARM (Computer Aided Reduction Method) software. These reduced mechanisms were tested against measurements and detailed chemistry for their ability to predict ignition delay over a range of conditions and found to give good agreement. 3-D high speed CFD simulations using a reduced mechanism for hydrocarbon/air combustion demonstrate the ability of reduced mechanisms to implement realistic hydrocarbon combustion chemistry models into CFD.

While optical diagnostic techniques have been applied with great success to the fundamental study of combustion chemistry and physics in the laboratory, the challenges afforded by real-world propulsion systems demand continuing innovation if such techniques are to be adapted and transitioned for use in engineering tests and on-board monitoring and control applications. This paper documents continuing efforts to transition aerodynamic measurement technologies from diagnostics-development laboratories to combustor test- and-evaluation facilities in the Propulsion Directorate's Combustion Science Branch (Turbine Engine Division). Applications of various optical diagnostic techniques for visualizing flowfields and quantifying temperatures and key species concentrations in several advanced combustors are described. A number of next- generation diagnostics targeted for laboratory-to-facility transition in the near future are highlighted as well.

While optical diagnostic techniques have been applied with great success to the fundamental study of combustion chemistry and physics in the laboratory, the challenges afforded by real-world propulsion systems demand continuing innovation if such techniques are to be adapted and transitioned for use in engineering test and on-board monitoring and control applications. A desire to achieve measurement tools in new spectral territory that exploit limited available optical access and provide high data-acquisition bandwidth has motivated the development efforts described in this paper. An ultranarrowband, mid-infrared optical parametric oscillator, terahertz transmitters and receivers for studies in the far-infrared, and high-speed imaging systems based on modelocked lasers and high-framingrate cameras represent just a few of the potential solutions now under development for current and future combustion and propulsion applications.