Effects of Intake Components on Combustion and Emission Characteristics in an n-Butanol/Diesel Blend Fueled Engine.

To assess the effects of intake components and n-butanol application on compression-ignition engines, an experiment was carried out based on a single-cylinder engine fueled with n-butanol/diesel-blended fuel. The results show that with the increased n-butanol fraction of the blended fuel, the emissions of particulate mass (PM) decrease significantly, but the NO x and hydrocarbon (HC) emissions deteriorate. For B15 and B30, the PM emissions are 66.2% and 74.4% lower than B0, respectively. Furthermore, exhaust gas recirculation (EGR) was introduced to reduce the NO x emissions. However, a large EGR rate significantly reduces the indicated thermal efficiency (ITE) of the engine. Compared with the non-EGR condition, the ITE of B15 and B30 decrease by 3.1% and 3.8%, respectively, when the EGR rate is 18%. At the same time, the PM and HC emissions are found to be increased greatly. The PM emission of B15 and B30 increases by 69% and 46% and the HC emission increase by 150% and 71%, respectively. To restrain the engine emissions caused by the EGR, pure oxygen is further introduced into the intake charge. It is found that both the PM and HC emissions are significantly reduced with the introduction of extra oxygen. Under the condition of the 18% EGR rate, increasing oxygen addition to 4% can reduce HC emissions by more than 50% and the total particle mass of B15 and B30 is reduced by 60.6% and 47.7%, respectively. Moreover, the ITE reduction and combustion deterioration caused by the large EGR are found to be alleviated. By adjusting the n-butanol ratio, EGR rate, and oxygen addition, the excellent performance of combustion and emission can be achieved in an n-butanol/diesel blend fueled engine.