Investigation of the influence of multiple gasoline direct injections on macroscopic spray quantities at different boundary conditions by means of visualization techniques

Abstract

The reduction of combustion emissions and fuel consumption can be achieved by controlling the fuel mixture to be burned and therefore the fuel injection. In this study a gasoline direct injection (GDI) piezo hollow cone injector is investigated by visualization measurements. Both single and double injection events are examined in a pressurized chamber. For the single injection, the influence of the ambient temperature and pressure is analysed in detail. For the double injection, the ambient conditions and the time interval between two injections are varied. For the single injection, the general shape of the spray, the recirculation eddy formed at the spray edge, the stringy structure of the hollow cone, and defined quantities such as the penetration length or the spray width are examined with respect to the influence of the ambient conditions. For the double injection, the same properties are evaluated, with the focus put not only on the influence of the ambient conditions, but also on the mutual interaction of two spray events. The experimental results show a clear impact of both the ambient conditions and the time difference between two injections. In particular, the investigation of the recirculation eddy may be helpful in determining possible positions for the spark plug, since the spark plug is preferably placed in regions where the air-fuel mixture variations are minimal.

Relative Importance of Fuel Properties on Gdi Fuel Spray Tip Penetration

“…4, the increasing P amb translated into a slight decrease of the slope during the momentum-driven part of the injection process and a decrease of maximum fuel-spray-tip penetration. This spray behavior is in accordance with the results reported by Martin et al [2]. The influence of P amb was twofold.…”

“…They showed that increasing P amb simultaneously reduced the fuel spray penetration and cone diameter. Such observations were also reported by Martin et al [2] with a 95% isooctane/5% n-heptane fuel. They also looked at the effect of the ambient temperature (T amb ) on spray penetration, concluding it was small compared to that of P amb .…”

Experimental and theoretical investigation on spray characteristics of bio-ethanol blends using a direct injection system

“…The mentioned CC is designed and fabricated to pressurize till 15 bar. As Martin et al [20] and Liu et el. [21] represented, surrounding pressure a ects the spray properties signi cantly, while surrounding temperature does not have any important e ect on them.…”

In cylinder visualization of stratified combustion of E85 and main sources of soot formation

“…In the single injection experiment the piston was closer to the injector at the same time after the start of injection due to the later start of injection crank angle. Martin et al [41] found that the penetration length of the hollow cone fuel spray from an outward opening piezo injector increased linearly during injection and the penetration rate decrease significantly at the end of injection in pressure chamber measurements at 0.5 [MPa] and 1.0 [MPa]. Based on the shorter duration of fuel spray impingement on the piston crown and the reduction of the penetration length at the cessation of injection it is conjectured that a smaller fuel mass impinged on the piston crown at ∆t SOI = 478 [µs] in the double injection experiment where injection had ceased compared to the single injection experiment where injection continued.…”

“…At ∆t SOI = 978 [µs] the fuel spray penentration length was smaller and the spray was wider compared to the first fuel spray at ∆t SOI = 278 [µs]. Martin et al [41] found that the penetration length and maximum width of the hollow cone fuel spray decreased with increasing pressure. During motored conditions the single injection caused the pressure to decrease by 1 [bar] from 19 [bar] due to vaporization of the fuel.…”