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The transient and quasi-steady flame structure of reacting fuel sprays produced by single-hole injectors has been studied using chemiluminescence imaging and Planar Laser-Induced Fluorescence (PLIF) in various constant-volume facilities at different research institutes participating in the Engine Combustion Network (ECN). The evolution of the high-temperature flame has been followed based on chemiluminescence imaging of the excited-state hydroxyl radical (OH *), and PLIF of ground-state OH. Regions associated with low-temperature chemical reactions are visualized using formaldehyde (CH 2 O) PLIF with 355-nm excitation. We compare the results obtained by different research institutes under nominally identical experimental conditions and fuel injectors. In spite of design differences among the various experimental facilities, the results are consistent. This lends confidence to studies of transient behavior and parameter variations performed by individual research groups. We present results of the transient flame structures at Spray A reference conditions, and include parametric variations around this baseline, involving ambient temperature, oxygen concentration and injection pressure. Key results are the observed influence of an entrainment wave on the transient flame behavior, model-substantiated explanations for the high-intensity OH * lobes at the lift-off length and differences with OH PLIF, and a general analogy of the flame structures with a spray cone along which the flame tends to locate for the applied parametric variations.

The Engine Combustion Network (ECN) is becoming a leading group concerning the experimental and computational analysis of Engine combustion. In order to establish a coherent database for model validation, all the institutions participating to the experimental effort carry out experiments at well-defined standard conditions (in particular at Spray A conditions: 22.8kg/m3, 900K, 0% and 15% O2) and with Diesel injectors having the same specifications. Due to the rising number of ECN participants and also to unavoidable damages, additional injectors are required. This raises the question of injector's characteristics reproducibility and of the appropriate method to introduce such new injectors in the ECN network.In order to investigate this issue, a set of 8 new injectors with identical nominal Spray A specification were purchased and 4 of them were characterized using ECN standard diagnostics. In particular, the measurements include the nozzle hole diameter, the rate of injection, the liquid and vapor penetrations, the auto-ignition delay and the lift-off length. Variations of ambient temperature, oxygen concentration and density have also been performed.In general the results show similar behavior to ECN standard injectors, confirming that this set of new injectors can be integrated into the pool of ECN injectors. However, discrepancies between spray characteristics were observed, although the injector specifications and the boundary conditions were sensibly the same. The sources of variations from injector to injector are analyzed in order to provide new information on the reproducibility of injectors characteristics, and improve the comparison methodology between experimental data and simulation.

Spark-ignition direct-injection engines operating in a stratified, lean-burn regime offer improved engine efficiency; however, seemingly random fluctuations in stratified combustion that result in partial-burn or misfire prevent widespread implementation. Eliminating these poor combustion events requires detailed understanding of engine flow, fuel delivery, and ignition, but knowing the dominant cause is difficult because they occur simultaneously in an engine. This study investigated the variability in fuel–air mixture linked to fuel injection hardware in a near-quiescent pressure vessel at high-temperature conditions representative of late, stratified-charge injection. An eight-hole spark-ignition direct-injection spray was interrogated using high-speed schlieren and Mie-scatter imaging from multiple, simultaneous views to acquire the vapor and liquid envelopes of the spray. The mixture fraction of vaporized sections of the spray was then quantified at a plane between plumes using Rayleigh scattering. Probability contours of the line-of-sight vapor envelope showed little variability between injections, whereas probability contours derived from planar, quantitative mixing measurements exhibit greater amounts of variability for lean-combustion-limit charge. The mixture field between plumes was characterized by multi-hole and end-of-injection dynamics that attract the plumes to each other and toward the injection axis, resulting in a liquid-fuel-droplet-dense merged central jet in the planar measurements. Supplemental long-working distance microscopy imaging showed the existence of fuel droplets far downstream in the region of the planar laser measurements.

Diesel spray experimentation at controlled high-temperature and high-pressure conditions is intended to provide a more fundamental understanding of diesel combustion than can be achieved in engine experiments. This level of understanding is needed to develop the high-fidelity multi-scale CFD models that will be used to optimize future engine designs. Several spray chamber facilities capable of high-temperature, high-pressure conditions typical of engine combustion have been developed, but because of the uniqueness of each facility, there are uncertainties about their operation. The Engine Combustion Network (ECN) is a worldwide group of institutions using combustion vessels, whose aim is to advance the state of spray and combustion knowledge at engine-relevant conditions. A key activity is the use of spray chamber facilities operated at specific target conditions in order to leverage research capabilities and advanced diagnostics of all ECN participants. The first target condition, called "Spray A", has been defined with detailed ambient and injector conditions. For this paper, we describe results from the constant-volume pre-burn vessel at Eindhoven University of Technology. The executed measurements include a wide range of diagnostics to characterize "spray A" in reacting and non-reacting conditions in great detail. Observations of spray penetration, ignition, liquid length and flame lift-off location by using several high-speed imaging diagnostics are discussed and compared with other ECN participating institutes. Comparison Spray A data from the other participating institutes, as it was presented during the 2 nd ECN workshop is gathered from the ECN website database [1]. It can be concluded that the obtained results from the standardized ECN spray diagnostics, show satisfactory similarity, despite of the challenge to reach similar boundary conditions (ambient and injector) in each of the unique facilities. The differences in results are within the measurement deviation and uncertainty or can be explained by the usage of (slightly) different injectors. Combining the results of the different measurement techniques provides an overall (time resolved) overview where the different phases of fuel injection are directly linked and summarized. The presented overview provides a direct input for (CFD) modeling validation.