SOME STUDIES ON ENGINE PERFORMANCE AND EMISSION CHARACTERISTICS OF A SI ENGINE FUELLED WITH OXYGENATED BIO-ADDITIVE (TRIACETIN)

Abstract

Rapid exhaustion of the petroleum products has led to increase in levels of pollution up to peak levels. However, stricter emission norms and depletion of natural reserves of fossil fuels would lead the researchers to find the renewable and cleaner alternatives. Unburnt hydrocarbon and carbon monoxide are the two most hazardous emissions of the gasoline engine. These emissions are responsible for various respiratory diseases such as, asthma, lung cancer, bronchitis, emphysema and failure of reproductive organs, etc. So, in order to mitigate these emissions, many researches have been done in the past in the form of fuel modifications by introducing biofuels, varying the design of combustion chamber, and after treatments of the exhaust gas. In the present scenario, to control the emissions and fuel reserves, researchers are conducting many experiments by using the biofuels. In the global market, the demand of biofuels is increasing exponentially leading into generation of glycerol in high amount. So, to control the economy of biodiesel, a proper valorisation of the waste glycerol is needed. One of the prominent ways for the utilization of crude glycerol is acetylation of glycerol which produces triacetin. Because of extra oxygen content, and high-octane rating, the triacetin is made to be used as a fuel additive for spark ignition engine. The present study has been carried out in two phases. The first phase covers the investigation on engine performance and emission parameters using gasoline-methanol blended fuels in four stoke spark ignition engine. By enhancing the methanol content, BTE of an engine has been increased gradually as compared to the neat gasoline operation. On the other hand, engine exhaust emissions such as: Carbon monoxide (CO), Hydrocarbon (HC), Nitrogen oxides (NOx) has been studied and found that on increasing the dosages of methanol in the fuel blends would led to decrease in the vi aforementioned exhaust emissions due to extra oxygen content and high latent heat of vaporization of the methanol. In addition to this, by increasing the methanol concentration up to 5% in the fuel blend, a significant reduction in the exhaust emissions is noticed. However, the efficiency of the engine is improved largely at this concentration of methanol in the fuel blends. In the second phase of this study, the effect of addition of triacetin in the gasolinemethanol blended fuels on the engine performance and emission parameters has been carried out. A multivariate optimisation technique i.e. Response Surface Methodology (RSM) using a full factorial experimental design is employed for finding out the optimal parameters of fuel blend ratio and engine load for maximizing the engine efficiency and minimizing the exhaust emissions. Various surface plots and contour plots of engine performance and emission parameters are showed which helps to identify the effects of input factors (i.e. Dosages of methanol and triacetin, engine load) on responses (i.e. CO, HC, NOx, BTE, EGT). With the help of response surface optimizer, optimum value of input factors can be determined for maximizing the engine performance parameters and minimizing the various exhaust emissions. A confirmatory validation test is also conducted with an error nearly about 6%. With reference to gasoline-methanol blended fuels, by adding the triacetin fuel additive showed a significant improvement in engine efficiency, exhaust gas temperature by reducing the various exhaust emissions.