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The Effect of Lateral Venting on Deflagration-to-Detonation Transition in Hydrogen-Air-Steam Mixtures at Various Initial Temperatures (NUREG/CR-6524)

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Publication Information
Abstract

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NUREG/CR-6524 (PDF - 3.64 MB)

Publication Information

Manuscript Completed: July 1998
Date Published: November 1998

Prepared by
G. Ciccarelli, J. L. Boccio, T. Ginsberg, C. Finfrock, L. Gerlach/BNL
H. Tagawa/NUPEC
A. Malliakos/NRC

Brookhaven National Laboratory

Upton, NY 11973-5000

A. Malliakos, NRC Project Manager

Prepared for
Division of Systems Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
NRC Job Code L1924/A3991

and

Nuclear Power Engineering Corporation
5F Fujita Kanko Toranomon Building
3-17-1, Toranomon, Minato-Ku
Tokyo 105
Japan

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Abstract

The influence of gas venting on flame acceleration in an obstacle-laden tube has been investigated in the High-Temperature Combustion Facility (HTCF) at BNL. The main component of the HTCF is a 27.3-cm- inner diameter heated detonation tube. In the present experiments, five 3.1-meter-long tube sections were used with a vent section placed in between each tube section. The total vent area per vent section is four times the tube's cross-sectional area. The entire length of the vessel is filled with 20.6-cm-inner diameter orifice plates, with 27.3-cm spacing, to promote flame acceleration. Hydrogen-air-steam mixtures were tested at initial temperatures up to 650K and at an initial pressure of 0.1 MPa.

In these venting experiments, the flame was observed to accelerate very quickly in the first tube section before the first vent section. For lean hydrogen mixtures, after the first vent section, the flame velocity decayed to a velocity on the order of the laminar burning velocity. For more sensitive mixtures, the flame reached a quasi-steady flame velocity similar to flame propagation in the choking regime observed in tests without venting. For all initial temperatures, the lean limit for significant flame acceleration (i.e., choking regime limit) with venting increased over the nonventing case by an average of 2 percent hydrogen. In the choking regime, the flame was observed to accelerate in the tube section to a maximum velocity close to the speed of sound in the products and then decelerate across the vent section. There was little evidence of any variation in the global average velocity (i.e., average over the length of one vent and tube section) once the flame entered this mode of propagation. Pressure measurements taken before the last vent section, near the end of the tube, were similar to overpressures measured in tests without venting. At the limited temperatures tested where DDT was observed, the minimum hydrogen concentration required for transition to detonation increased with venting present as compared to without venting. In all cases, after a certain propagation distance, the detonation wave failed due to local venting effects and continued to propagate at a velocity characteristic of the choking regime.