Application of multi-response robust parameter design for performance optimization of a hybrid draft biomass cook stove

A novel design of a hybrid draft biomass cook stove was proposed, constructed and tested for 54 combinations of five important parameters viz. Inlet area ratio, Fuel surface to volume ratio, Pot diameter, Secondary air flow rate, and Pot gap. The combined effects of these factors on the stove performance parameters such as overall efficiency (ηo), CO emissions and PM2.5 emissions were estimated. The data obtained by executing designed experiments (CCD) on the stove prototype was fitted to independent second-order models using RSM. The fitted models were further used to predict the stove performance for different combinations of the five factors. The analysis revealed that the prototype cannot achieve energy performance better than Tier 2 level and ηo greater than 30%. However, the hybrid draft enabled the prototype to achieve Tier 4 level performance in CO and PM2.5 emissions. Desirability function coupled with the fitted RSM models was used for robust parameter optimization of the stove performance to maximize efficiency, minimize emissions and propagation of error. The robust parameter optimization resulted in the best possible overall stove performance of ηo = 26.54%, CO/MJd = 2.249 g/MJ and PM/MJd = 34.67 mg/MJd obtained at the control factor levels of Ms = 1.74 g/s and Pg = 14 mm.