Analyzing the Cycle-to-Cycle Variations of Pulsing Spray Characteristics by Means of the Proper Orthogonal Decomposition

Abstract

This paper presents a novel approach to analyze the cycle-to-cycle variations of pulsing spray characteristics. The purpose is to quantify the cycle-to-cycle variations of the macroscopic characteristics of spark-ignition direct-injection (SIDI) fuel injector spray, so that improvements of air-fuel mixture formation can be made to enhance the combustion efficiency and reduce emissions of SIDI engines. The experiments were carried out using an eight-hole SIDI fuel injector under a controlled ambient environment with an extended range of test conditions. Using a strobe light as an illumination source, multiple cycles of macroscopic spray structure images at a fixed injection delay time were taken by a CCD camera. The proper orthogonal decomposition (POD) technique was implemented to analyze the cycle-to-cycle characteristics of spray variation. In addition, the effects of injection pressure, ambient pressure, and fuel type on spray variation were also investigated. POD analysis reveals that the mode 1 pattern captured the ensemble-averaged spray shape, the mode 2 pattern provided quantification of spatial fuel distribution variations of different cycles of spray, and higher mode patterns further quantified the finer details of the variations surrounding the well-atomized periphery of the spray structure. POD analysis also quantitatively confirms that better-atomized sprays led to slightly higher variations of finer structures along the spray boundary. Overall, this study demonstrates that POD analysis can be used as a novel approach to quantify the cycle-to-cycle variation of pulsing spray characteristics.

Effect of Boost Pressure on the In-Cylinder Tumble-Motion of GDI Engine under Steady-State Conditions using Stereoscopic-PIV

“…POD analysis can be carried out either on experimental or numerical simulation data sets. POD analytical technique has been extensively adopted by many researchers to study engine cycle-to-cycle variations Chen et al (2011), Liu et al (2013), Chen et al (2013), Tumble motion evolution at different valve lifts under steady-state conditions Mohammed El-Adawy et al (2017a), spray and combustion process Graftieaux et al (2001), Bizon et al (2009), Sick et al (2012.…”

Characterization of the effect of intake air swirl motion on time-resolved in-cylinder flow field using quadruple proper orthogonal decomposition

“…The first POD mode usually contains the most significant characteristic of input flow fields by capturing more than half of the kinetic energy. In addition, the first mode is similar to the ensemble average of the snapshots shown in previous study [18], so the first mode itself is considered as the dominant structure of the flow. After the dominant structure has been determined, the next step to obtain the coherent structure starts by temporally removing the first mode from the dataset.…”

“…POD was first introduced to study large scale eddies in turbulent flows [13], and it was further developed for flow analysis by separating the turbulent fluctuations and unsteady swirl motion [14]. Since this statistical technique was applicable to extract the engine flow characteristics, further research had been implemented by implementing POD to analyze the spray and combustion processes [15][16][17][18]. It is widely accepted that appropriate enhancements of fuel atomization and mixing depend on the understanding of incylinder flow fields obtained from PIV experiments.…”

Large-Eddy Simulations of Spray Variability Effects on Flow Variability in a Direct-Injection Spark-Ignition Engine Under Non-Combusting Operating Conditions

“…For direct-injection engines, the fuel spray plays a significant role in in-cylinder mixing and is a potential source of significant CCVs. Previous research has included work looking at both the isolated spray in a constant volume chamber [26][27][28] and in engines [29][30][31][32][33][34]. However few of these studies focused on the effects of spray variability, and there remains work to increase our understanding of the relative impacts of spray variability on the overall flow and mixing variability in a direct-injection engine.…”