Numerical and experimental study on effect of wall geometry on wall impingement process of hollow-cone fuel spray under various ambient conditions

Shim, Youngsam; Choi, Gyung‐Min; Kim, Duck-Jool

doi:10.1016/j.ijmultiphaseflow.2009.06.004

Cited by 39 publications

(8 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, these DI-type engines suffer from relatively higher particulate matter (PM) and unburnt hydrocarbon (UHC) emissions, primarily from the non-uniform nature of spray process; their emissions become even worse when there are spray-wall interactions, causing cylinder/piston wetting with substantial wall fuel films, especially during cold-start. 4–9 When a flame approaches the film surface, quenching and non-premixed combustion could occur, attributing to PM and UHC emissions. What’s worse, soot particles may deposit on the solid surface (such as piston, liner, cylinder head, injector and spark plug) that can further cause coking, degradation and even pre-ignition.…”

Section: Introductionmentioning

confidence: 99%

Fuel wall film effects on premixed flame propagation, quenching and emission

Tao

VanDerWege

et al. 2018

International Journal of Engine Research

View full text Add to dashboard Cite

The formation of fuel wall film is a primary cause for efficiency loss and emissions of unburnt hydrocarbons and particulate matters in direct injection engines, especially during cold start. When a premixed flame propagates toward a wall film of liquid fuel, flame structure and propagation could be fundamentally affected by the vaporization flux and the induced thermal and concentration stratifications. It is, therefore, of both fundamental and practical significance to investigate the consequent effect of a wall film on flame quenching. In this work, the interaction of a laminar premixed flame and a fuel wall film has been studied based on one-dimensional direct numerical simulation with detailed chemistry and transport. The mass and energy balance at the wall film interface have been implemented as boundary condition to resolve vaporization. Parametric studies are further conducted with various initial temperatures of 600–800 K, pressures of 7–15 atm, fuel film and wall temperatures of 300–400 K. By comparing the cases with an isothermal dry wall, it is found that the existence of a wall film always promotes flame quenching and causes more emissions. Although quenching distance can vary significantly among conditions, the local equivalence ratio at quenching is largely constant, suggesting the dominant effects of rich mixture and rich flammability limit. By further comparing constant volume and constant pressure conditions, it is observed that pressure and boiling point variation dominate the vaporization boundary layer development and flame quenching, which further suggests that increased pressure during compression stroke in engines can significantly suppress film vaporization. Emissions of unburnt hydrocarbon, soot precursor and low-temperature products before and after flame quenching are also investigated in detail. The results lead to useful insights on the interaction of flame propagation and wall film in well-controlled simplified configurations and shed light on the development of wall film models in three-dimensional in-cylinder combustion simulation.

show abstract

Section: Introductionmentioning

confidence: 99%

Fuel wall film effects on premixed flame propagation, quenching and emission

Tao

VanDerWege

et al. 2018

International Journal of Engine Research

View full text Add to dashboard Cite

show abstract

“…The nominal electrical control pulse was 0.4 ms, but due to the ramping of the control voltage for opening and closing, the total time during which fuel was injected was observed to be ~0.8 ms. N-hexane was used as surrogate fuel of gasoline, together with exciplex fluorescence-forming tracersfluorobenzene (FBZ) and diethylmethylamine (DEMA). This is a well-characterized tracer combination [14] with minimal spectral cross-talk and good co-evaporation properties, and has been applied in several studies [15][16][17][18]. The concentrations of tracers used in this work was 3 % FBZ and 7 % DEMA by volume.…”

Section: Experiments Setupmentioning

confidence: 99%

Imaging of gasoline-like sprays with planar laser-induced exciplex fluorescence using a stereoscopic imaging system

Andersson

Yamaguchi²,

Wang

2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

View full text Add to dashboard Cite

The role of the fuel injection systems in direct injected gasoline engines is to achieve a suitable fuel vapor distribution, homogeneous or with some degree of stratification, while avoiding unwanted effects such as wall wetting. Planar laser-induced exciplex fluorescence (PLIEF) is a method suitable for the characterization of such sprays since it enables separate imaging of both vapor and liquid phase of fuel simultaneously. In this study a hollow-cone spray generated with an outwards-opening piezo-actuated injector is investigated, with the injector mounted in a constant volume, constant pressure spray chamber with quartz windows, providing a controlled steady test environment. N-hexane is used as surrogate fuel of gasoline, together with exciplex-forming fluorescence tracers -fluorobenzene and diethylmethylamine. Fluorescence excitation is carried out with a parallel laser sheet from the fourth harmonic light of a Nd:YAG-laser (266 nm) running at 10 Hz. Exciplex fluorescence images from liquid phase and monomer fluorescence spray images from vapor phase can be acquired by a single UV-sensitive CMOS camera equipped with a stereoscope having filters selectively transmitting monomer fluorescence at 295 nm and exciplex fluorescence at 355 nm. Since the fluorescence is strongly quenched by oxygen, most of the experiments were carried out in a nitrogen atmosphere. Images were recorded during the injection and at various time steps after the end of the injection, and typical spray development for this type of injector was observed, i.e. the fuel forms an expanding cone, the sheet breaks up to form a vortex structure and the vortices continue to expand after the end of the injection. Fuel vapor is firstly observed at the same locations as the liquid drops, and is then accumulated into the center of the vortices. In addition, penetration of liquid phase and vapor phase are found to be very similar. Various injection pressures have been tested, which shows that increasing the fuel pressure from 10 to 20 MPa results in a larger vortex structure. The fuel evaporation can be followed by studying the evolution of the monomer and exciplex fluorescence as a function of time. At room temperature the vaporization is found to be very slow, but above 40°C there is a noticeable presence of vapor at the end of the injection, and at higher temperatures, the vaporization goes even faster. Keywords Hollow-cone spray, Exciplex LIF, Phase separation, GDI, LIEF IntroductionThe role of the fuel injection systems in direct injected gasoline engines is to achieve a suitable fuel vapor distribution, homogeneous or with some degree of stratification, while avoiding unwanted effects such as wall wetting. Therefore it is desirable to characterize the fuel injection systems and how the fuel vaporizes and becomes dispersed in the combustion chamber, in order to investigate and improve the combustion process. As an extension technique of planar laser-induced fluorescence (LIF), which is proved to be a powerful imaging technique to visual...

show abstract

“…Direct injection engines are rapidly dominating the engine market due to the higher compression ratio, increased thermal efficiency and fuel economy. For small and medium-sized high-speed direct injection diesel engines, the fuel spray is likely to collide with the wall of the combustion chamber to form a wall-mounted film due to the limitation of the combustion chamber geometry (Brandriss et al, 1998;Zhao et al, 1999;Shim et al, 2009;. In particular, during the engine cold start, or at low speed and high load conditions with a large amount of fuel being injected, under which conditions, the evaporation of fuel spray is reduced, which forms a liquid film on the surface of the piston or cylinder liner, resulting in the "wet wall" phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Modeling Study of Wall Film Effect on Combustion Characteristics of Premixed Flame in a Constant Volume Combustion Bomb

et al. 2022

View full text Add to dashboard Cite

The primary objective of the present study was to investigate the impact of wall film on the combustion characteristics of premixed flames in internal combustion engines through the joint experimental and numerical techniques. The interaction between the premixed methane-air flame and n-dodecane film attached to the wall of a constant volume combustion bomb was experimentally examined. The flame propagation processes, as well as pressure evolution were quantitatively characterized. Then, computational fluid dynamic (CFD) simulation was performed incorporating the combustion chemistry model. To enable efficient simulation of the chemically reacting flow in engine chambers, a simplified modeling approach based on a two-step reaction scheme was developed. A compact reaction model for the selected model fuel n-dodecane was constructed and reduced to include 35 chemical species and 180 reactions. The flame propagation process of the premixed flame and its interaction with dry and wet walls was studied. The results showed that the propagation of the premixed flame could be divided into four stages, and the existence of the slit structure increased the instability of the flame structure in the near-wall region. The wall film tended to promote emissions, producing more unburned hydrocarbons, soot precursors and aldehydes.

show abstract

Numerical and experimental study on effect of wall geometry on wall impingement process of hollow-cone fuel spray under various ambient conditions

Cited by 39 publications

References 12 publications

Fuel wall film effects on premixed flame propagation, quenching and emission

Fuel wall film effects on premixed flame propagation, quenching and emission

Imaging of gasoline-like sprays with planar laser-induced exciplex fluorescence using a stereoscopic imaging system

Experimental and Modeling Study of Wall Film Effect on Combustion Characteristics of Premixed Flame in a Constant Volume Combustion Bomb

Contact Info

Product

Resources

About