ENGINE COMBUSTION NETWORK (ECN): CHARACTERIZATION AND COMPARISON OF BOUNDARY CONDITIONS FOR DIFFERENT COMBUSTION VESSELS

Abstract

The Engine Combustion Network (ECN) is a worldwide group of institutions using combustion vessels
\nand/or performing computational fluid dynamics (CFD) simulation, whose aim is to advance the state of
\nspray and combustion knowledge at engine-relevant conditions. A key activity is the use of spray chamber
\nfacilities that operate at high-temperature, high-pressure conditions typical of diesel combustion, which are
\noperated at specific target conditions in order to leverage research capabilities and advanced diagnostics of
\nall ECN participants. The first target condition, called ¿Spray A,¿ has been defined with detailed ambient
\n(900 K, 60 bar, 22.8 kg/m3, 15% oxygen) and injector (common rail, 1500 bar, KS1.5/86 nozzle, 0.090-mm
\norifice diameter, n-dodecane, 363 K) conditions. Establishing and improving these experimental boundary
\nconditions in unique facilities throughout the world represents a major step forward in the establishment of
\nhigh-quality, quantitative data sets for engine spray combustion. This paper is a review of the methodology
\nto characterize and control the ambient and fuel-injector boundary conditions (e.g., temperature, pressure,
\ncomposition) as offered by six different participating institutions of the ECN, each targeting the Spray A
\nconditions and quantifying experimental uncertainty. Constant-pressure flow (CPF) and constant-volume
\npreburn (CVP) chambers with various ambient gas composition are compared for the first time. Experimental
\ndiagnostics include the use of fast-response, radiation-corrected thermocouples for spatially resolved gas and
\nfuel-injector temperature, laser-induced phosphorescence for surface temperature, and high-speed transducers
\nfor pressure. With guidance about the uncertainty and variation that exists between facilities, simplified
\nmodels are then employed to understand how these boundary condition variations may affect aspects of spray
\ncombustion. Ambient gas and fuel temperature effects on liquid- and vapor-phase penetration are examined
\nwith established one-dimensional models. Chemical kinetics modeling in single- or multi-zone reactors is used
\nto predict the influence of different preburn environments on the major and minor species present in the ambient
\ngas at the start of injection, and their subsequent effect on spray ignition. This review article provides
\nrecognition of the challenge in creating well-controlled high-temperature, high-pressure environments, and
\nidentifies which boundary condition variations are expected to have the highest impact on spray combustion.