Study of Turbulent Spherical Flames in a Reconfigurable Fan-Stirred Flame Bomb

Abstract

Turbulent combustion is a very active and challenging research topic. A spherically expanding flame immersed in a turbulent field is one way to gain fundamental insight on the effect of turbulence in combustion. This kind of experiment is conducted inside a fan-stirred flame bomb, but there is only a handful of these devices around the globe. The list is even shorter if demanding conditions are to be tested, i.e. high pressure, high temperature and intense turbulence. A new fan-stirred flame bomb was designed and built to address this shortage.

Existing fan-stirred flame bombs were studied first to learn their salient characteristics. This literature review was then used as guidance in the design of turbulence generation elements. A few options of impellers were explored. The flow field produced by the chosen impeller was measured with Laser Doppler Velocimetry (LDV). A detailed exposition of the vessel engineering ensued.

Before turbulent experiments were attempted, a validation of the rig accuracy and worthiness was made. The setup demonstrated excellent repeatability and agreement with benchmarks. Finally, a demonstration of the new apparatus was made by testing a lean mixture of syngas. The experiment matrix using hydrogen and H₂/CO mixtures included three levels of pressure (1, 5, and 10 bar) and three levels of turbulence fluctuation rms (1.4, 2.8, and 5.5 m/s). General trends of the effect of turbulence were in line with expectation, but not enough information was obtained to gain insight on the role of pressure.