Propagation of Turbulent Natural Gas/Air Flames in Tubing With 90° Bends

Anytime flammable gas mixtures are handled, there is a risk of combustion. This is particularly true in many industrial applications where space is limited and equipment is located near sources of ignition. Unfortunately, there is a lack of understanding of combustion phenomena within process equipment such as mufflers, rotating blowout preventers, liquid traps, and dry gas seal assemblies. These vessels have small internal volumes, complex internal geometries, and are connected using small diameter piping. This paper discusses the results of a parametric study which was carried out to establish the nature of combustion within such vessels and tubing. The test vessel had an internal volume of 7 in3 (115 ml) and the tubing had a nominal diameter of 0.5 in (1.27 mm). Flowing, turbulent, pre-mixed natural gas/air mixtures were used. The study did not attempt to increase turbulence using devices such as mesh screens or attempt to stabilize the flame. The results from a representative sample of 76 tests, from the 5,000+ tests that have been completed, are discussed herein. Typical pressure and temperature responses are presented and analyzed. It is demonstrated that flames can be remotely detected using only high speed pressure data. Turbulent flames were formed whose velocity was found to be linearly dependant on Reynolds number.