prediction of emission and performance of a variable compression ratio engine with gasoline/ethanol blend using response surface methodology

In this study, the effects of ethanol-butanol/gasoline blends (eb0%, eb10%, and eb20%) on spark ignition engine performance and emissions were investigated for the different compression ratios (6.0:1, 8.0:1, and 10.0:1), and different load conditions (2kw, 4kw, and 6kw). based on the experimental results, the response surface methodology has been used to develop a model and to estimate the outputs of brake thermal efficiency, brake-specific energy consumption, carbon monoxide, hydrocarbon, and oxides of nitrogen. the optimum operating conditions, 9.970% of the ethanol-butanol blend, 10.0:1 compression ratio, and 6 kw of engine load were obtained through the desirability approach of response surface methodology. brake thermal efficiency, brake-specific energy consumption, carbon monoxide, hydrocarbon, and oxides of nitrogen at optimum conditions are 35.041 %, 0.493 kg/kwh, 0.217 %, 213.575 ppm, and 1263.787 ppm, respectively. moreover, the developed models have higher r2 values near 1, and the optimum responses are obtained with a higher desirability value of 0.768. ethanol-butanol/gasoline blends improved the brake thermal efficiency, carbon monoxide, and hydrocarbons. whereas it increased the brake-specific energy consumption and oxides of nitrogen.  in addition, the validation test results illustrate that the acceptable error rate between optimized values obtained through the desirability approach of response surface methodology and experimental values is below 7%.