Engine Combustion Network (ECN): Characterization and comparison of Diesel spray combustion in new high-pressure and high-temperature chamber = Engine Combustion Network (ECN): Characterization and comparison of Diesel spray combustion in new high-pressure and high-temperature chamber

다국어 초록 (Multilingual Abstract)

New One Shot Engine (NOSE) has been designed to simulate the thermodynamic conditions at High Pressure-High Temperature like an actual common-rail diesel engine to study the diesel spray and combustion. The advantage of this kind of set-up in comparison to pre-bum chamber or flue chamber is that the initial gas mixture can be well controlled in terms of species and mole fraction. Indeed, as example, the combustion of spray in more realistic environment can be done by adding species which represent burnt gas recirculation (EGR) or in an environment without H₂O and CO₂. Therefore, our first objective was to share the experimental results required by Engine Combustion Network (https://ecn.sandia.gov) which represents the international reference in the establishment of high-quality and quantitative data sets for engine spray combustion to develop and improve models.
The purpose of this work is to present experimental results from different classical data already available by ECN and to discuss about the limitations of NOSE. For that, first the non-reactive standard Spray-A condition (900 K, 60 bar, and 22.8 kg/m3 with pure Nitrogen) was reached to evaluate the accuracy of the set-up in terms of liquid and vapor penetration lengths, respectively characterized by Schlieren and Diffused-Back Illumination. Then the NOSE set-up was improved to provide conditions for different ambient temperatures as 800 K and 850 K. Second, in reactive conditions, the Lift-Off Length (LOL) was measured by OH^* chemiluminescence images. Different techniques as the Schlieren, OH^* chemiluminescence and cylinder pressure rise were used to measure Ignition Delay (ID) and compared.
The consistency of the data obtained from liquid length and spray penetration indicates a good level of repeatability between the test rigs employed. The results outline a global agreement with the ECN dataset. Mainly the differences are observed for ID and LOL, due to variations and inhomogeneities of the temperature field, especially in the case of 800 K. To provide a temperature field more homogeneous, different compression ratios have been tested and the chamber temperature characterized by using 4 fine wire thermocouples of 25 ㎛ diameter. Results show that homogeneous temperature inside chamber lead to higher ignition delay than inhomogeneous conditions. The future work will be focused on the presence of different species to evaluate their impact on the combustion development and soot production/oxidation.