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

2022 ◽  
Vol 7 ◽  
Author(s):  
Shijie Bai ◽  
Hongsheng Zhang ◽  
Chang Li ◽  
Chaohui Wu ◽  
Xingyu Liang ◽  
...  
Keyword(s):  
Flame Propagation ◽  
Internal Combustion Engines ◽  
Combustion Characteristics ◽  
Constant Volume ◽  
Premixed Flame ◽  
Wall Region ◽  
Wall Film ◽  
Soot Precursors ◽  
Constant Volume Combustion ◽  
The Impact

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.

scholarly journals Combustion Characteristics of Biodiesel blended Gasoline Fuel in Engine like Condition using Constant Volume Combustion(CVCC)

2018 ◽  
Vol 145 ◽  
pp. 187-192 ◽  
Author(s):  
Shubhra Kanti Das ◽  
Hyun Jo ◽  
Kyung Hoon Jwa ◽  
Ocktaeck Lim ◽  
Youngmin Woo
Keyword(s):  
Combustion Characteristics ◽  
Constant Volume ◽  
Constant Volume Combustion

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

2018 ◽  
Vol 21 (6) ◽  
pp. 1055-1066 ◽  
Author(s):  
Mingyuan Tao ◽  
Haiwen Ge ◽  
Brad VanDerWege ◽  
Peng Zhao
Keyword(s):  
Flame Propagation ◽  
Direct Injection ◽  
Flame Structure ◽  
Three Dimensional ◽  
Premixed Flame ◽  
Practical Significance ◽  
Detailed Chemistry ◽  
Rich Mixture ◽  
Wall Film ◽  
Flame Quenching

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.

Experimental Investigation of Spray and Combustion Characteristics of Soybean Biodiesel in a Constant-Volume Combustion Chamber: The Effects of Fuel and Ambient Gas Temperature

2013 ◽  
Author(s):  
Yifeng Wu ◽  
Ronghua Huang ◽  
Chia-fon F. Lee
Keyword(s):  
Combustion Chamber ◽  
Ignition Delay ◽  
Combustion Characteristics ◽  
Constant Volume ◽  
Gas Temperature ◽  
Soot Mass ◽  
Soybean Biodiesel ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber ◽  
Ambient Gas

Effects of fuel and ambient gas temperature on the spray and combustion characteristics of soybean biodiesel were studied in a constant-volume combustion chamber. Four different fuels or fuel blends including B0, B20, B50 and B100 were investigated experimentally. The soot mass data were obtained via a new technique called forward illumination light extinction (FILE). The ambient gas temperature was varied from 700 K to 1200 K. To simulate the engine operating conditions, the ambient oxygen concentration and its density were kept at 21 % and 15 kg/m3, respectively. A higher peak pressure is found as the biodiesel content decreases. B20, B50 and B100 have a shorter ignition delay than B0 and the ignition delay decreases with increasing biodiesel content. The liquid penetration decreases with decreasing biodiesel content. Moreover, the integrated natural flame luminosity (INFL) increases with decreasing biodiesel content. Shorter flame (i.e., soot luminosity) duration and a longer delay between start of combustion (SOC) and the appearance of flame are found as the biodiesel content increases. The flame duration also increases with increasing ambient gas temperature for all fuels. Soot is lower and appears later at a lower ambient gas temperature, while it is burned out at around the same time. Near-zero soot mass was observed for all tested fuels at 700 K. A shorter soot formation process is observed for biodiesel fuels. The soot reduction using B20 and B50 is not obvious compared to B0 at a low temperature. But under the ordinary diesel engine operating condition at 1000 K, the soot reduction is significant. It is also found that the soot can be reduced by 60% and above when B100 is used in this study.

Dynamics of spray impingement wall film under cold start conditions

2019 ◽  
Vol 21 (2) ◽  
pp. 319-329 ◽  
Author(s):  
Xuesong Li ◽  
Di Xiao ◽  
Scott E Parrish ◽  
Ronald O Grover ◽  
David LS Hung ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Laser Diagnostics ◽  
Numerical Models ◽  
Cold Start ◽  
Mie Scattering ◽  
Optical Measurements ◽  
Fuel Film ◽  
Wall Film ◽  
Spray Impingement ◽  
The Impact

Fuel film that adhered on engine walls from spray impingement is considered a primary source of harmful combustion emissions. However, the physics of the wall film formation, propagation, and breakup is not fully understood yet because of its multiphase nature. Existing literature has revealed that the mass transportation within the fuel film takes a wave propagation form. This article aims to identify the dynamics of the wall film during spray impingement via high-speed laser diagnostics. In this work, a single-hole injector was used and the spray impinged onto a stage made of sapphire glass for diagnostics purposes. Iso-octane was used as the fuel and 10% ethanol was blended to dope rhodamine 6G as the fluorescent species for laser excitation. Simultaneous optical measurements, such as laser-induced fluorescence and Mie scattering, are performed to obtain the characteristics of the wall film quantitatively. Various aspects of the wall film, including the frequency of the wave, wave speed, and wave height, are inspected. The impact of fuel temperature and wall temperature under typical cold-start conditions are also studied to investigate the temperature dependence of the wall film dynamics. The research is also intended to provide quantitative experimental data for numerical models for impingement prediction and thus help the process of emission reduction and combustion optimization of internal combustion engines.

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