ASSESSING POTENTIAL DIFFERENCES OF DIESEL FUEL EFFECTS ON COMBUSTION AND ENGINE BEHAVIOR BETWEEN DIFFERENTLY-SIZED ENGINES

Fuel properties impact the combustion and emissions behavior of diesel engines through their influence on the physical process associated with fuel injection, entrainment and fuel-air mixing, as well as by changes to the combustion chemistry associated with fuel properties. In addition, these influences are also impacted strongly by various engine sizes. Thus, to find fuel effects on engine behavior between two engines, the research is conducted through a series of experimental tests at 1500 rev/min and two loads for commercial diesel and Fuels for Advanced Combustion Engines fuels between two engines. First, baseline testing and simulation was aimed at using experiment and a simulation model of two differently sized engines to identify the effects of engine size on combustion characteristics and emissions. The results are compared for the same brake mean effective pressure and show that engine size has a significant impact on indicated efficiency, with the larger displaced engine having a higher indicated efficiency than the smaller displaced engine. Second, the effects of cetane number (CN) on combustion and emissions between differently sized engines were investigated using a fuel matrix with each variable having a base value as well as a lower and higher level. The results show that CN significantly affects combustion phasing and emissions of the two engines in similar ways. As CN increases, the magnitude of heat release rate (HRR) increases and its peak location advances as CN increases. Moreover, the effects of distillation temperature (T90) on engine efficiency and emissions are performed. The results show comparing with medium-duty (MD) engine performance, increasing T90 shows relative stronger effects on HRR for light-duty (LD) engine, especially for the low-load condition. Finally, the effects of aromatic content on engine efficiency and emissions are discussed. The results show increasing aromatic content increases the magnitude of the peak HRR, and delays its location for both engines at the low-load condition. At the medium-load condition, increasing aromatic content has similar effect on LD engine, but does not show obvious effect on MD engines

Nonradiating sources of the biharmonic wave equation

This paper offers an extensive exploration of nonradiating sources for the two- and three-dimensional biharmonic wave equations. Various equivalent characterizations are derived to reveal the nature of a nonradiating source. Additionally, we establish the connection between nonradiating sources in the biharmonic wave equation and those in the Helmholtz equation as well as the modified Helmholtz equation. Several illustrative examples are explicitly constructed to showcase the existence of nonradiating sources. One significant implication of the existence of nonradiating sources is that it undermines the uniqueness of the inverse source problem when utilizing boundary data at a fixed frequency