Abstract
The purpose of this study is to obtain low-emission and high-efficiency in a hydrogen-LPG engine. An experimental study was carried out to obtain fundamental data for performance and emission characteristics in a LPG engine with various mixing ratios of hydrogen-LPG blends. The results indicated that as the hydrogen mixing ratio in the fuel blend increases, the heating value of mixture decreases. Moreover, compared to the conventional LPG engine, combustion stability and exhaust emission(CO, CO2, NOx and THC) characteristics were improved as well.
Research and /or Engineering Questions/Objective:
Finding alternative fuels for the future internal combustion engines is necessary to solve the problem of environmental pollutions. Thanks to low carbon content, LPG fuel is an alternative fuel that emits lower CO, CO2 and HC compared to conventional fuels such as gasoline and diesel. Hydrogen has higher flame speed, higher heating value, lower ignition energy and outstanding exhaust emission characteristics compared to the conventional fuels. The objective of this study is to investigate possibilities of improving combustion and emission characteristics of a hydrogen-LPG engine.
Methodology:
In hydrogen-LPG engine test, a specially designed hydrogen injection system and a dual-fuel ECU were installed on a conventional LPG engine to provide hydrogen-LPG mixture of various mixing ratios. Ignition timing was set to MBT and air-fuel ratio was set to stoichiometric air-fuel ratio(λ=1.0). According to hydrogen mixing ratios, in-cylinder pressure and combustion stability were measured to analyze combustion characteristics. Also exhaust emissions(CO, CO2, NOX and THC) were measured and analyzed.
Results:
Heating values were lowered and combustion stability was improved as hydrogen mixing ratio increases. In terms of emission characteristics, CO, CO2, and THC emissions were decreased due to low carbon content of mixture and improved combustion stability. In addition, NOX emission decreases as hydrogen mixing ratio increases due to shortened duration of NO formation because of fast combustion speed of hydrogen.
Limitations of this study:
This study is not focused on commercialization of hydrogen-LPG engine. Therefore, application of hydrogen storage and supply system were not considered. Moreover, this study is focused on middle engine speed range, therefore to specify hydrogen-LPG engine characteristics, more experiments need to be done.
What does the paper offer that is new in the field including in comparison to other work by the authors?:
Study of hydrogen-LPG engine is sparse worldwide.
Conclusion:
Hydrogen-LPG engines have possibilities of improving combustion characteristics and reducing exhaust emissions. The results of this study are expected to be useful as reference data for future studies on hydrogen-LPG engines.
KEYWORDS : LPG (Liquefied Petroleum Gas), Hydrogen, Dual-Fuel, Exhaust Emissions, HLPG(H2- LPG)