An experimental study of ignition in 40kW co-axial turbulent diffusion oxy-coal jet flames

摘要

This paper is directed towards understanding how composition of the coal transport medium (primaryCO_2 and O_2) affects the ignition standoff distance in 40kW co-axial turbulent diffusion, oxy-coal flames,supported in a specially designed combustion test rig, rated at 100kW. First, a methodology to define andquantify the ignition behavior of laboratory-combustor-scale turbulent pulverized coal jets was developed and isdescribed in detail. Results are presented in the form of probability density profiles of the measured standoffdistance, as obtained from replicate runs each consisting of six thousand photo images. The results show thatflame stability is affected by primary P_(O2), secondary preheat temperature, secondary P_(O2), and transport medium.Increasing secondary P_(O2) can stabilize the flame with zero P_(O2) in transport stream. It also shows that thecontrolling mechanism of co-axial pulverized coal jet ignition is molecular diffusion (O_2 through N_2 or CO_2).Not only do these results provide qualitative insight into ignition of coal in turbulent oxy-coal flames ofpractical relevance, but they can also provide a basis for validation of future detailed simulations of this process.