Impingement characteristics of an early injection gasoline direct injection engine: A numerical study

Abstract

This paper describes the use of a Lagrangian discrete droplet model to evaluate the liquid fuel impingement characteristics on the internal surfaces of an early injection gasoline direct injection (GDI) engine. The study focuses on fuel impingement on the intake valve and cylinder liner between start of injection (SOI) and 20° after SOI using both a single-and multi-component fuel. The single-component fuel used was isooctane and the multi-component fuel contained fractions of iso-pentane, iso-octane and n-decane to represent the light, medium and heavy fuel fractions of gasoline, respectively. A detailed description of the impingement and liquid film modelling approach is also provided. 2Fuel properties, wall surface temperature and droplet Weber number and Laplace number were used to quantify the impingement regime for different fuel fractions and correlated well with the predicted onset of liquid film formation. Evidence of film stripping was seen from the liquid film formed on the side of the intake valve head with subsequent ejected droplets being a likely source of unburned hydrocarbons and particulate matter emissions. Differences in impingement location and subsequent location of liquid film formation were also observed between single-and multicomponent fuels. A qualitative comparison with experimental cylinder liner impingement data showed the model to well predict the timing and positioning of the liner fuel impingement.

Analysis of Regulated Pollutant Emissions and Aftertreatment Efficiency in a GTDi Engine Using Different SOI Strategies

“…Late SOIs cause a reduction in the time for the preparation of the AF mixture, which can promote a decrease in the degree of evaporation of the fuel and a decrease in the homogenization of the charge, producing an increase in THC emissions. Additionally, since the injectors are placed between the intake valves, a change in the injection timing can lead to a valve impingement, which produces an increase in the THC [57,58]. In this sense, the later the SOI the higher intake valve lift as it is observed in Figure 5.…”

Numerical Evaluation of Combustion Regimes in a GDI Engine

“…Unfortunately, experimental results were not available at the standardised condition of T f =363K and 0.5bar gas pressure but the results suggest that the droplet diameter is within the expected range and the change in droplet diameter over time closely matches the experimental results providing increased confidence in the capability of the droplet breakup model to satisfactorily predict the secondary breakup processes. Further validation results for the fuel injection event can be found in [44,45]. …”

Combined experimental and numerical study on fuel deposition characteristics of an impinging PFI spray with different impingement geometries

“…The effects of wall condition (dry/wet), wall temperature, and liquid film thickness on the droplet-wall interaction regimes were also considered. A critical Weber number was also introduced to distinguish the regime transition under wet wall conditions, which was based on the experimental investigation of Cossali et al 26 Senda model has been adopted in many recent studies, [27][28][29][30] and the improved agreement between the numerical predictions and experimental measurements was reported.…”

“…In the past few years, extensive experimental [31][32][33][34][35] and numerical 28,30,[36][37][38] studies have been focused on the formation of liquid film in GDI systems, due to its significant impact on the PN emission. For instance, Kobashi et al 30 numerically study the formation and vaporization of an impinging GDI spray by using Senda spray impingement model and other advanced physical sub-models.…”