Optical analysis of spray behavior with a modern common rail injector in canola oil operation

Using straight vegetable oil, such as canola oil, in agricultural diesel engines is one way to reduce dependence on petroleum fuel. However, canola oil has different physical properties from petroleum diesel. These properties can lead to several problems, such as poor spray atomization, incomplete combustion, crankcase dilution, combustion chamber deposits, and deposits at injectors and valves. Even new types of engines, which are equipped with modified tanks and injection systems, cannot completely compensate for the disadvantages of canola oil. In this study, macroscopic spray behavior was investigated under unfired conditions in a pressure chamber. The rail pressure was set to 112 and 200 MPa, and the chamber pressure was adjusted to 1.8 and 3.5 MPa, which correspond to 20 and 35 kg/m³ of ambient density, respectively. The temperature of petroleum diesel was fixed to 20°C, and the temperature of canola oil was adjusted to vary between 50°C and 70°C. The first step of the experimental investigation was a comparison between spray patterns of petroleum diesel and canola oil, which demonstrates the influence of fuels. Afterward, a comparison of spray patterns between an unused injector and an injector after 700 hours of engine operation with canola oil was carried out to show the influence of deposits. Finally, a sensitivity analysis of the Mie-scattering technique was conducted to explore the potential of this technique for different viscosities of fuel.