Correlations of high-pressure lean methane and syngas turbulent burning velocities: Effects of turbulent Reynolds, Damköhler, and Karlovitz numbers
Artikel i vetenskaplig tidskrift, 2015

This paper investigates correlations of high-pressure turbulent burning velocities (ST) using our recent ST measurements of lean methane and syngas spherical flames at constant elevated pressures (p) and constant turbulent Reynolds numbers (ReT ≡ u′LI/ν), where u′, LI, and ν are the r.m.s. turbulent fluctuation velocity, the integral length scale of turbulence, and the kinematic viscosity of reactants, respectively. Such constant constraints are achieved by applying a very large high-pressure, dual-chamber explosion facility that is capable of controlling the product of u′LI in proportion to the decreasing ν due to the increase of p. We have found that, contrary to popular scenario for ST enhancement with increasing p at any fixed u′, ST actually decreases similarly as laminar burning velocities (SL) with increasing p in minus exponential manners when values of ReT are kept constant. Moreover, ST increases noticeably with increasing ReT varying from 6700 to 14,200 at any constant p ranging from 1 atm to 10 atm. It is found that a better correlation for the normalization of ST is a power-law relation of ST/u′ = aDab, where Da = (LI/u′)(SL/δF) is the turbulent Damköhler number, δF ≈ α/SL is the laminar flame thickness, and α is the thermal diffusivity of unburned mixture. Thus, the very scattering ST data for each of lean methane and syngas mixtures can be merged on their ST/u′ vs. Da curves with very small data fluctuations. For lean methane flames with the Lewis number (Le) ≈ 1, ST/u′ ≈ 0.12Da0.5 supporting a distributed reaction zone model anticipated by Ronney (1995), while for lean syngas flames with Le ≈ 0.76 ≪ 1, ST/u′ ≈ 0.52Da0.25 supporting a theory predicted by Zimont (1979). A simple physical mechanism is proposed in attempt to explain what causes the aforesaid discrepancy on the power-law constants.


Shenqyang Shy

National Central University

C.C. Liu

Okinawa Institute of Science and Technology Graduate University

National Central University

J.Y. Lin

National Central University

L.L. Chen

National Central University

Andrei Lipatnikov

Chalmers, Tillämpad mekanik, Förbränning och framdrivningssystem

S.I. Yang

National Formosa University Taiwan

Proceedings of the Combustion Institute

15407489 (ISSN)

Vol. 35 2 1509-1516





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