Effects of fuel composite additives on the vibration, wear and emission performances of diesel engines under hot engine tests

Abstract

Diesel engines applied for ships are currently facing an escalating demand for energy conservation and emission reduction, which has driven the application of fuel composite additives. Nevertheless, adverse phenomena affecting engine reliability have been observed in practical engine applications with unclear mechanisms. The present study investigated the vibration, wear, and emission performances of three types of composite additives with detergent and synergist function in a diesel engine. Vibration acceleration, cylinder temperature, NOx emission quantity, as well as the wear characteristics of cylinder liner-piston ring (CLPR) friction pairs were selected as characterization parameters. The results revealed that components of additives have a certain impact on vibration, wear, combustion, and emission performance. Specifically, additives of Type Ⅰ containing aviation kerosene and Type Ⅱ containing 2-Ethyl 1-hexanol and 2-Ethylhexyl nitrate compound in diesel were susceptible to cause aggravated engine vibration and thus lead to excessive wear. Furthermore, Type I exacerbates the thermal stress and worsens combustion stability, resulting in increased mechanical vibrations, cylinder temperature, and NOx emission. In contrast, addition of Type Ⅲ containing 2-nitro-propane and toluene results in improved reliability, demonstrating a 7.6% reduction in mechanical vibration energy and a 27.4% decrease in wear mass losses of piston rings, while effectively mitigating abnormal wear on the liner surface. Likewise, it also it also facilitates a mild combustion process and achieves better emission reduction results by reducing the NOx emission by 11.5% while slightly lowering the cylinder temperature by 0.74%.