The ignition parameters of the coal-water slurry droplets at the different methods of injection into the hot oxidant flow

Abstract

Two different experimental approaches were realized for investigations of integral characteristics of single droplet ignition of coal-water slurry containing petrochemicals (CWSP) inside the hot flow of the gas oxidant. At first, the droplet was fixed inside the flow by special holder and the second way is free injection of the soaring droplet into the volume of combustion chamber. Research reports an experimental estimation of influence of material holder on ignition characteristics for typical CWSP. This is important, since many researchers use various holders (the ceramic rod, thermocouple junction, metal wire) when inserting droplets of coal-water slurry (CWS) and CWSP into the combustion chamber. There were three types of the droplet holders: the junction of the high-speed thermocouple, metallic wire and the ceramic rod. The basic components of the CWSP were filter-cake (the coal processing waste), the used turbine oil, the plasticizer (wetting agent) and water. Initial droplet radius was 0.5–1mm, and the temperature and the oxidant flow velocity were 400–1000K and 0.5–5m/s correspondingly. The ignition delays and the combustion times for the fuel droplets together with minimal temperatures of the stable ignition (with further combustion) were defined. Comparison of parameters of the flying droplet ignition with corresponding values for droplets that were fixed by holder was done. Soaring droplets have smaller ignition delay times (for 7–25%) relative to the case of droplet fixed inside the oxidant flow by holder (when the all rest parameters are similar). Influence of the holder material onto the values of times of ignition delay and combustion become essentially weaker with oxidant temperature growth. The obtained numerical results show the limitations and advances of the two approaches for laboratory investigations of the CWSP ignition and combustion.