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Technical Paper

A Numerical Investigation of the Vaporization Process of Lubricating Oil Droplets under Gas Engine Conditions

2015-09-01
2015-01-1949
The abnormal combustion resulted by the auto-ignition of lubricating oil is a great challenge to the development of Otto-cycle gas engines. In order to investigate the mechanism of lubricating oil droplet vaporization process, a crucial sub-process of auto-ignition process, a new multi-component vaporization model was constructed for high temperature and pressure, and forced gas flow conditions as encountered in practical gas engines. The vaporization model has been conducted with a multi-diffusion sub-model considering the multi-component diffusivity coefficients in the gas phase. The radiation heat flux caused by ambient gas was taken into account in high temperature conditions, and a real gas equation of state was used for high pressure conditions. A correction for mass vaporization rate was used for forced gas flow conditions. Extensive verifications have been realized, and considerable results have been achieved.
Technical Paper

Research on the Characteristics of Enrichment Fuel Injection Process in the Pre-Chamber of a Marine Gas Engine

2015-09-01
2015-01-1961
Fuel injection and fuel-air mixture formation processes have significant influence on the performance of spark ignition gas engines. In order to study the fuel enrichment injection process in the pre-chamber of a marine gas engine, the flow field in the pre-chamber during the gas fuel injection period was investigated by the particle image velocimetry (PIV) method. An organic glass model of pre-chamber was made for optical measurement. The flow fields in the pre-chamber with four different gas injection angles were analyzed, respectively. The measurement results were qualitatively compared to the CFD calculation results as the verification of the calculation. Based on the comparison of the PIV experiment results, an optimal gas fuel injection angle was chosen. Furthermore, 3D CFD calculation models with the baseline and optimal fuel injection angles of a marine spark ignited natural gas engine were generated to calculate the working process.
Technical Paper

Researches of Double-Layer Diverging Combustion System (DLDCS) in a DI Diesel Engine

2015-09-01
2015-01-1833
The new DI diesel engine combustion system named Double-Layer Diverging Combustion System (DLDCS) results in a better Brake Specific Fuel Consumption (BSFC) and lower exhaust emissions. The previous results of numerical simulation and bench test of a single cylinder DI diesel engine showed that more homogeneous fuel distribution, better BSFC and lower emission level were obtained by employing this combustion system. In this research, further numerical simulation are employed to seek the best injection advance angle and investigate the influence of different volume fraction and type lines of upper layer with AVL Fire.
Technical Paper

The Evaporation Characteristics of Cylinder Oil of Low-Speed 2-Stroke Marine Engines

2017-03-28
2017-01-0886
The combustion of cylinder lubricating oil (called as cylinder oil for short) is one of the major sources of PM emissions of low-speed 2-stroke marine diesel engines. For pre-mixed combustion low-speed 2-stroke marine gas engines, the auto-ignition of cylinder oil might result in knock or more hazard abnormal combustion - pre-ignition. Evaporation is a key sub-process of the auto-ignition process of cylinder oil droplets. The evaporation behavior has a profound impact on the auto-ignition and combustion processes of cylinder oil droplets, and a great influence on engine combustion performance and emission characteristics. This paper applied an oil suspending apparatus to investigate the evaporation behavior of cylinder oil droplets and base oil droplets. The effects of ambient temperatures on the evaporation process were measured and analyzed. The results indicate that the evaporation of cylinder oil includes heating, evaporating, pyrolysis, and polymerization.
Technical Paper

Control-Oriented Modeling of Soot Emissions in Gasoline Partially Premixed Combustion with Pilot Injection

2017-03-28
2017-01-0511
In this paper, a control-oriented soot model was developed for real-time soot prediction and combustion condition optimization in a gasoline Partially Premixed Combustion (PPC) Engine. PPC is a promising combustion concept that achieves high efficiency, low soot and NOx emissions simultaneously. However, soot emissions were found to be significantly increased with high EGR and pilot injection, therefore a predictive soot model is needed for PPC engine control. The sensitivity of soot emissions to injection events and late-cycle heat release was investigated on a multi-cylinder heavy duty gasoline PPC engine, which indicated main impact factors during soot formation and oxidation processes. The Hiroyasu empirical model was modified according to the sensitivity results, which indicated main influences during soot formation and oxidation processes. By introducing additional compensation factors, this model can be used to predict soot emissions under pilot injection.
Technical Paper

An Experimental Study of the Combustion, Performance and Emission Characteristics of a CI Engine under Diesel-1-Butanol/CNG Dual Fuel Operation Mode

2016-04-05
2016-01-0788
In order to comply with the stringent emission regulations, many researchers have been focusing on diesel-compressed natural gas (CNG) dual fuel operation in compression ignition (CI) engines. The diesel-CNG dual fuel operation mode has the potential to reduce both the soot and NOx emissions; however, the thermal efficiency is generally lower than that of the pure diesel operation, especially under the low and medium load conditions. The current experimental work investigates the potential of using diesel-1-butanol blends as the pilot fuel to improve the engine performance and emissions. Fuel blends of B0 (pure diesel), B10 (90% diesel and 10% 1-butanol by volume) and B20 (80% diesel and 20% 1-butanol) with 70% CNG substitution were compared based on an equivalent input energy at an engine speed of 1200 RPM. The results indicated that the diesel-1-butanol pilot fuel can lead to a more homogeneous mixture due to the longer ignition delay.
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