X-ray diagnostics of dodecane jet in spray A conditions using the new one shot engine (NOSE)

Abstract

Quantifying liquid mass distribution data in the dense near nozzle area to develop and optimize diesel spray by optical diagnostic is challenging. Optical methods, while providing valuable information, have intrinsic limitations due to the strong scattering of visible light at gas-liquid boundaries. Because of the high density of the droplets near the nozzle, most optical methods are ineffective in this area and prevent the acquisition of reliable quantitative data. X-ray diagnostics offer a solution to this issue, since the main interaction between the fuel and the X-rays is absorption, rather than scattering, thus X-ray technique offers an appealing alternative to optical techniques for studying fuel sprays. Over the last decade, x-ray radiography experiments have demonstrated the ability to perform quantitative measurements in complex sprays. In the present work, an X-ray technique based on X-ray absorption has been conducted to perform measurements in dodecane fuel spray injected from a single-hole nozzle at high injection pressure and high temperature. The working fluid has been doped with DPX 9 containing a Cerium additive, which acts as a contrast agent. The first step of this work was to address the effect of this dopant, which increases the sensitivity of X-ray diagnostics due its strong photon absorption, on the behavior and the physical characteristics of n-dodecane spray. Comparisons of the diffused back illumination images acquired from ndodecane spray with and without DPX 9 under similar operating conditions show several significant differences. The current data show clearly that the liquid penetration length is different when DPX 9 is mixed with dodecane. To address this problem, the dodecane was doped with a several quantities of DPX containing 25% ± 0.5 of Cerium. Experiments show that 1.25% of Ce doesn't affect the behaviour of spray. Radiography and density measurements at ambient pressure and 60 bars are presented. Spray cone angle around 5° is obtained. The obtained data shows that the result is a compromise between the concentration of dopant for which the physical characteristics of the spray do not change and the visualization of the jet by X-ray for this concentration. KeywordsDiesel Spray, Engine, X-ray radiography, high pressure high temperature chamber, dodecane, Cerium, spray diagnostics Introduction New One Shot Engine (NOSE) has been designed to simulate the thermodynamic conditions at High PressureHigh Temperature (HPHT) like an actual common-rail diesel engine to study the diesel spray and combustion. The first objective was to share the experimental results required by Engine Combustion Network (https://ecn.sandia.gov). In a first step, the penetration lengths for the vapor and liquid spray at the non-reactive standard Spray-A condition (900 K, 60 bar, and 22.8 kg/m 3 with pure nitrogen) were achieved from focused shadowgraphy and diffused-back illumination (DBI) [1]. A detailed understanding of the mixing between fuel and air can lead to more efficient combustion. This ...