RSM based optimization of lambda and mixed fuel concentration parameters of an LTC mode engine

In this study, the effects of lambda and premixed ratio (PR) parameters on the response parameters of an engine operating in LTC (low temperature combusiton) mode is investigated and optimized using a hybrid method. RSM (response surface method), which is a combination of experimental and statistical method, is used as hybrid method. Depending on the variable parameters of lambda and PR, an experimental set was created with CCD (central composite design) and experiments were performed. The effects of the variable parameters on the response parameters were investigated and evaluated in detail on the generated counter graphs, optimization of the variable parameters was carried out. As lambda increased, a decrease in engine torque and thermal efficiency values, and improvements in CO2 and NOx emissions were observed. As PR increased, thermal efficiency and specific fuel consumption values worsened. The optimum premixed ratio was determined as 33.619 % and lambda value as 2.576. At these conditions, the values of response parameter were obtained as torque 12.115 Nm, BSFC 346.764 g/kWh, ITE 21.447 %, CA10 3.503, CA50 8.005, CO 0.169 %, HC 191.467 ppm, CO2 5.301 %, NOx 404.564 ppm and soot 12.687 %. The optimization desirability value was determined as 0.665 and strengthened the goodness of the optimization. •Optimization of mixture fuel concentration and lambda with RSM.•As Lambda increases, engine torque increases, BSFC decreases, while ITE increases.•Performance, efficiency and emission parameters improve with decreasing isopropanol ratio.•The optimum isopropanol premixed ratio was determined as 33.619 % and lambda ratio as 2.576.