Internal and near nozzle measurements of Engine Combustion Network “Spray G” gasoline direct injectors

Abstract

Gasoline direct injection (GDI) sprays are complex multiphase flows. When compared to multi-hole diesel sprays, the plumes are closely spaced, and the sprays are more likely to interact. The effects of multi-jet interaction on entrainment and spray targeting can be influenced by small variations in the mass fluxes from the holes, which in turn depend on transients in the needle movement and small-scale details of the internal geometry. In this paper, we present a comprehensive overview of a multi-institutional effort to experimentally characterize the internal geometry and near-nozzle flow of the Engine Combustion Network (ECN) Spray G gasoline injector. In order to develop a complete picture of the near-nozzle flow, a standardized setup was shared between facilities. A wide range of techniques were employed, including both x-ray and visible-light diagnostics. The novel aspects of this work include both new experimental measurements, and a comparison of the results across different techniques and facilities. The breadth and depth of the data reveal phenomena which were not apparent from analysis of the individual data sets. We show that plume-to-plume variations in the mass fluxes from the holes can cause large-scale asymmetries in the entrainment field and spray structure.Both internal flow transients and small-scale geometric features can have an effect on the external flow. The sharp turning angle of the flow into the holes also causes an inward vectoring of the plumes relative to the hole drill angle, which increases with time due to entrainment of gas into a low-pressure region between the plumes. These factors increase the likelihood of spray collapse with longer injection durations.

Development of limited-view tomography for measurement of Spray G plume direction and liquid volume fraction

“…Single plumes are distinct 5 mm downstream of the injector. X-ray tomography at Argonne National Lab provides the additional data closer to the nozzle for the same fuel injector (Duke et al 2017). Uncertainties in the liquid volume fraction values are dependent on the utilization of limited views, as well as on droplet size.…”

“…ECN recommends the MiePlot software to calculate C * ext . The droplet size distributions in Spray G and G2 were measured in the ECN community, respectively, with phase Doppler interferometry (PDI) (Duke et al 2017;ECN 2019). The PDI data and the derivation of the pLVF for liquid penetration measurements were published at the ECN6 workshop (Engine Combustion Network 2018).…”

“…By translating the probe volume through the plume, the plume center may be determined. For example, the plume center at a given axial position was defined as the position with highest droplet velocity magnitude for the Engine Combustion Network Spray G injector (Duke et al 2017). Because the nominal injector and operating conditions (Spray G) were identical, the plume center determined by PDI could be compared to that derived from extinction imaging (e.g., Sphicas et al 2017).…”

“…Because the nominal injector and operating conditions (Spray G) were identical, the plume center determined by PDI could be compared to that derived from extinction imaging (e.g., Sphicas et al 2017). Results showed a consistent decrease in plume direction (towards spray collapse) with time after the start of injection for two injectors with the same Spray G specification (Duke et al 2017).…”

“…Although the chamber for X-ray experiments could not be heated to the Spray G ambient gas condition (it was 300 K, rather than 573 K), the Spray G density was set at the correct 3.5 kg/m 3 target. The plume growth and direction derived from fuel density fields measured by X-ray tomography were compared to that of the PDI and extinction imaging (Duke et al 2017). The X-ray tomography showed that the plume direction angles are less than the measured geometric-hole drill angle (36°-38°), indicating already-deflected internal-nozzle flow that could affect plume interaction downstream.…”