VIEWS ON THE STRUCTURE OF TRANSIENT DIESEL SPRAYS

There has been tremendous change over the last few decades in the operating conditions of diesel fuel injection systems and engines, and in the diagnostic tools and numerical models available to evaluate them. Improvements in the diagnostic techniques coinciding with changes in diesel injector technology have brought about an entirely different view of the breakup of liquid in current diesel sprays. A detailed examination of the history and current understanding of the structure of the dense core region in transient diesel sprays is presented. Diagnostic methods are reviewed, and the appropriate uses are discussed. Of the techniques currently available, tomography is the most appropriate for determining the structure of the dense core region. Conductivity is not recommended. Line-of-sight techniques are recommended only for studying the preiphery of the spray. Due to its greater contrast, high-intensity Mie scattering is preferred over line-of-sight methods for liquid spray penetration distance measurements. Advances in phase-Doppler interferometry are required to provide drop size and velocity measurements in the near-nozzle region.