Performance Analysis of an Improved Natural Drift Sawdust Stove Incorporated with Air-varying Butterfly Valve

Abstract

Natural Drift Sawdust Stoves operate on the rocket theorem; the theory is that air is drawn into the stove by the partial vacuum created by the rising burnt gases in the combustion chamber. The study aims to evaluate the performance of an improved natural drift sawdust stove with an air-varying butterfly valve in enhancing combustion efficiency and overall thermal performance. However, there are notable design limitations in most sawdust stove designs, the inability for the stove to be ‘switched off’ once it gets ignited enhances the stove to deplete the loaded fuel-feed stock even when the cooking task is done. The study investigated the performance of an improved double chambered side-feed novel sawdust stove prototype with added design features such as the air-varying butterfly valve, for air regulation into the stove in order to mitigate this challenge, in addition good insulation materials pressed in between inner and out chambers to help reduce heat loss and improved user’s safety. Rocket Stove Technology on which the sawdust stove’s design is based has been identified and used as one of the many biomass technologies suitable for use in low-income households mostly in third world countries because they offer cheaper alternative solutions to energy poverty and are more environmental friendly. Carbon steel (2 mm AISI 1040 sheet metal) was chosen to be the main material for the construction of both the combustion chamber and the main outer body of the stove. In order to evaluate the prototype’s performance, Water Boiling Test (WBT) and Controlled Cooking Test (CCT) were employed in testing the stove’s water boiling ability, real-food cooking ability as well as usability. The study focused on thermal efficiency, fuel consumption and combustion chamber temperatures verses ambient temperature. These tests were also used to compare stove’s performance against Zambia’s common traditional cooking stoves, such charcoal brazier and the rudimentary traditional three stone stove. The prototype showed better fuel economy (20.6% stove efficiency achieved, 0.55 SFC) for the sawdust stove compared to (19% stove efficiency, 0.62 SFC) for charcoal brazier and (10.3% efficiency, 0.77 SFC) for the stone fire stove. Further research and dissemination of information about the stove need to be encouraged for greater application of this resource.