Abstract
One of the objective of Engine Combustion Network (ECN), (https://ecn.sandia.gov/) is to provide experimental results with high accuracy in order to validate model and reach new steps in scientific understanding of spray combustion at conditions specific to engines. The ECN community defines different target conditions, experimental diagnostics and post processing methods to facilitate the comparison of experimental and simulations studies performed in different facilities or models. In this context two French laboratories propose two new facilities, based on Rapid Compression Machines to reach the ECN spray A conditions. In this paper, the results of liquid and vapour spray penetration as well as Ignition Delay (ID) and Lift-Off Length (LOL) obtained with these Rapid Compression Machines are compared to the results obtained in the Constant Volume Preburn (CVP) vessel of IFPEN. The specificities of each experimental apparatus allow to bring complementary elements of understanding like confinement effects. In non-reactive condition, the liquid and vapour sprays were characterized by Diffused-Back Illumination and Schlieren technique, and in reactive conditions, the LOL and the ID by OH* chemiluminescence. The analysis of the results with regard to the boundary conditions (temperature, velocity, confinement) make it possible to validate these two new facilities and contribute to enhance the database of ECN, highlighting the confinement effect typical of piston engine operation.
Highlights
Since 20 years, due to increasingly drastic emission standards, many studies have been focused on spray and combustion for Internal Combustion Engines to improve the efficiency and reduce the pollutant emissions
The results of liquid and vapour spray penetration as well as Ignition Delay (ID) and Lift-Off Length (LOL) obtained with these Rapid Compression Machines are compared to the results obtained in the Constant Volume Preburn (CVP) vessel of IFPEN
By using the Global Sensitivity Analysis (GSA) method [10, 12] to investigate the influence of the different boundary conditions on the combustion parameters between the two kinds of chamber CVP and Constant-Pressure Flow (CPF), the most sensitive variables outside nozzle diameter are the fuel temperature for the liquid length, the initial turbulence intensity for the vapour penetration, the composition of the initial ambient gases (O2, major and minor species) and their temperature for the ignition delay and the flame lift-off length
Summary
Since 20 years, due to increasingly drastic emission standards, many studies have been focused on spray and combustion for Internal Combustion Engines to improve the efficiency and reduce the pollutant emissions. In [3] the original cylinder head was modified to support optical windows from different sides of combustion chamber As it continuously operates and scavenges the injected fuel and combustion products every cycle (near Top Dead Center (TDC)), a high repetition rate can be reached and the ambient gases are those introduced with a controlled composition. By using the Global Sensitivity Analysis (GSA) method [10, 12] to investigate the influence of the different boundary conditions on the combustion parameters between the two kinds of chamber CVP and CPF, the most sensitive variables outside nozzle diameter are the fuel temperature for the liquid length, the initial turbulence intensity for the vapour penetration, the composition of the initial ambient gases (O2, major and minor species) and their temperature for the ignition delay and the flame lift-off length. The effects of confinement, highlighted by the smaller ambient gas volume of RCYM compared to CVP and CPF, will be discussed with regard to the ambient gas composition
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