Numerical Studies of the Response of Flamelets to Unsteadiness in the Near-Field of Jets Under Diesel Conditions

Turbulent time records of scalar dissipation rates are numerically generated in the near-field of a high Reynolds number turbulent jet. The response of one-dimensional unsteady diffusion flamelets to these records were studied under pressure and temperature conditions representative of those in dies...

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Bibliographic Details
Published in:Combustion science and technology 2010-06, Vol.182 (7), p.717-738
Main Authors: Venugopal, Rishikesh, Abraham, John
Format: Article
Language:English
Subjects:
Applied sciences
Combustion. Flame
Diesel fuels
Diesel jets
Energy
Energy dissipation
Energy. Thermal use of fuels
Exact sciences and technology
Extinction/reignition
Jet engines
Laminar flamelets
Oxidation
Pressure
Reynolds number
Temperature
Theoretical studies. Data and constants. Metering
Turbulence models
Unsteady effects
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Summary:Turbulent time records of scalar dissipation rates are numerically generated in the near-field of a high Reynolds number turbulent jet. The response of one-dimensional unsteady diffusion flamelets to these records were studied under pressure and temperature conditions representative of those in diesel engines. n-Heptane was chosen as the diesel fuel surrogate, its oxidation chemistry modeled by a 1,540-step mechanism comprising 159 species. Unsteadiness in the scalar dissipation rates was observed to impact autoignition, extinction, and reignition in the near-field. Possible linkages between these observations and flame liftoff, as well as its prediction, in diesel engines are discussed. Steady flamelet models were shown to not capture unsteady extinction-reignition events and associated chemical phase-lag effects. Unsteady flamelet-progress variable (UFPV) models in which the progress variable uniquely identifies all the flame states corresponding to a given value of χ are more suitable for representing the physics.
ISSN:0010-2202
1563-521X
DOI:10.1080/00102200903415761