Numerical study of a micro flow reactor at engine pressures: Flames with repetitive extinction and ignition and simulations with a reduced chemical model

Combustion in a narrow channel with an imposed temperature gradient is studied numerically at elevated pressure with engine-relevant fuels. The focus is placed on unsteady flames with repetitive extinction and ignition (FREI) to determine the potential of this regime for fuel testing and calibration...

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Bibliographic Details
Published in:Combustion and flame 2018-11, Vol.197 (C), p.102-110
Main Authors: Lapointe, Simon, Druzgalski, Clara L., McNenly, Matthew J.
Format: Article
Language:English
Subjects:
ADVANCED PROPULSION SYSTEMS
Airplane engines
Computer simulation
Delay time
Ethanol
Extinction
Flame retardants
Flames
Flames with repetitive extinction and ignition (FREI)
Fuels
Gasoline fuel surrogates
Heptanes
Ignition
Low-temperature oxidation
Mathematical models
Micro flow reactor
Nuclear fuels
Organic chemistry
Quantum theory
Reduced chemical mechanism
Temperature gradients
Toluene
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Summary:Combustion in a narrow channel with an imposed temperature gradient is studied numerically at elevated pressure with engine-relevant fuels. The focus is placed on unsteady flames with repetitive extinction and ignition (FREI) to determine the potential of this regime for fuel testing and calibration of reduced chemical mechanisms. First, it is shown that the FREI regime does occur at elevated pressures for sufficiently small tube diameters. The sensitivity of the extinction and ignition temperatures to low-temperature chemistry is found to be significantly enhanced at 25 bar compared to atmospheric conditions. The ignition and extinction temperatures differ by up to 100 K between PRF mixtures with varying octane numbers. Ternary mixtures of iso-octane/n-heptane/toluene and iso-octane/n-heptane/ethanol at similar research and motor octane numbers are also studied. Second, the potential of using data from the micro flow reactor to infer reaction rates is assessed. A reduced chemical mechanism combining a small fuel-dependent submechanism with a detailed fuel-independent submechanism for the core species chemistry is used for that purpose. Only the most sensitive fuel-dependent reactions are inferred. the calibrated reduced model is compared to a detailed model and good agreement in ignition delay times and laminar flame speeds is observed. This illustrates the potential of a micro flow reactor with a controlled temperature profile to test fuels and infer kinetic data.
ISSN:0010-2180
1556-2921
DOI:10.1016/j.combustflame.2018.07.020