Counter Current Burner for an ND-TLUD 02 скачать в хорошем качестве

Counter Current Burner for an ND-TLUD 02

Counter-Current Woodgas Burner and Riser Height This is a demonstration of an experimental burner for a simple TLUD biomass cookstove. The prototype presented is not a complete stove. The purpose of this video is to demonstrate the importance of riser height on the function of a natural draft, top-lit updraft gasifier using the “Counter-Current Woodgas Burner” (CCWB). Riser height affects the flow rate of both primary and secondary air, and the degree of turbulent mixing of woodgas with secondary air. Increasing riser height creates greater buoyancy forces that can improve the efficiency of stove combustion, and stove responsiveness for the operator, but it can lead to excessive secondary air, and excessive turbulence under some conditions. With a true counter-current burner, the fuel gas and oxidizer gas collide head-on. This is more-or-less what happens with the CCWB, because a downward laminar flow of secondary air is sent against the upward flow of woodgas. However, it is not a perfect counter-current burner, because a lot of the secondary air is pulled sideways by the buoyancy force created in the gas flame. The main objective of the CCWB is to get as much turbulent mixing of secondary air and woodgas at the base of the gas flame as possible. We are trying to approach an ideal of a pre-mixed flame at somewhat above (to be determined) the stoichiometric requirement for oxygen. The second objective of the CCWB is to locate the base of the flame over the fuel bed char. Some secondary air supports glowing char, and sustains a higher temperature in the fuel bed, from the ignition front up to the top of the char, than would be obtained if the secondary air and the gas flame were located at some distance above the fuel bed. Glowing char can help with cracking of tars, and provide heat to assist in the piloting of gas ignition. This helps maintain woodgas flame stability at low gasification rates. Some modifications of the CCWB have been tried, but did not show much benefit. (1) A ring of small air holes (of various numbers and diameters) in the sidewall of the reactor were positioned just below the inner riser. It was thought that these holes would provide small flamelets that would keep the gas flame from extinguishing at very low gasification rates. It was found that these holes didn’t help, and functioned more to diminish the role of the counter-current air flow. (2) Various fins were made at the bottom of the internal riser to see if they would increase turbulence. Fins were found to be unnecessary. The stoves in this video are prototypes. They are working hypotheses that need scientific stove testing to optimize their geometry, and validate the counter-current approach. To become working stoves, they need a regulator for primary air, an insulated external riser, and mechanism to transfer the heat to the pot or other object of work. If the CCWB can be shown to improve combustion efficiency on diverse biomass fuels, and over a wide range of gasification rates, that would be good, because it is a very easy burner to build.