A review of dual-fuel combustion mode in spark-ignition engines

Because of the potential to reduce NOx and PM emissions simultaneously and the utilization of biofuel, diesel/compressed natural gas (CNG) dual-fuel combustion mode with port injection of CNG and direct injection of diesel has been widely studied. While in comparison with conventional diesel combustion mode, the dual-fuel combustion mode generally leads lower thermal efficiency, especially at low and medium load, and higher carbon monoxide (CO) and total hydrocarbons (THC) emissions. In this work, n-butanol was blended with diesel as the pilot fuel to explore the possibility to improve the performance and emissions of dual-fuel combustion mode with CNG. Various pilot fuels of B0 (pure diesel), B10 (90% diesel/10% n-butanol by volume basis), B20 (80% diesel/20% n-butanol) and B30 (70% diesel/30% n-butanol) were compared at the CNG substitution rate of 70% by energy basis under the engine speeds of 1400 and 1800 rpm. The experiments were carried out by sweeping a wide range of pilot fuel start of injection timings based on the same total input energy including pilot fuel and CNG. As n-butanol was added into the pilot fuel, the pilot fuel/CNG/air mixture tends to be more homogeneous. The results showed that for the engine speed of 1400 rpm, pilot fuel with n-butanol addition leads to a slightly lower indicated thermal efficiency (ITE). B30 reveals much lower NOx emission and slightly higher THC emissions. For the engine speed of 1800 rpm, B20 can improve ITE and decrease the NOx and THC emissions simultaneously relative to B0.

Download Full-text

Combustion and Emission Characteristics of a CI Engine Operating in Diesel-1-Butanol/CNG Dual Fuel Mode With Low and High CNG Substitution Rates in Light Load Operation

ASME 2016 Internal Combustion Engine Fall Technical Conference ◽

10.1115/icef2016-9456 ◽

2016 ◽

Author(s):

Xiangyu Meng ◽

Yuanxu Li ◽

Karthik Nithyanandan ◽

Wuqiang Long ◽

Chia-Fon F. Lee

Keyword(s):

Thermal Efficiency ◽

Substitution Rate ◽

Fuel Combustion ◽

Dual Fuel ◽

Injection Timing ◽

Combustion Mode ◽

Substitution Rates ◽

Low Load ◽

Pilot Fuel ◽

Dual Fuel Combustion

Dual-fuel combustion mode with direct injection of diesel as the pilot fuel and port injection of compressed natural gas (CNG) in compression ignition (CI) engines has been widely investigated to comply with the latest emission regulations. The diesel-CNG dual-fuel combustion mode shows some potential to decrease NOx and soot emissions simultaneously, while it reveals a lower thermal efficiency compared to the pure diesel combustion mode under low load condition. The purpose of the current study is to investigate the possibility of using diesel blended with 1-butanol as the pilot fuel to enhance the engine performance and reduce emissions. Three pilot fuels — B0 (pure diesel), B10 (90% diesel and 10% 1-butanol by volume) and B20 (80% diesel and 20% 1-butanol) with the CNG substitution rates of 50% and 80% were compared at an engine speed of 1200 rpm. The experiments were conducted by sweeping the pilot fuel injection timing from −3 to −18 ° CA ATDC with an equivalent total energy (∼5 bar IMEP). The results illustrated that, for the 50% CNG substitution rate, the dual-fuel operation mode revealed a higher indicated thermal efficiency (ITE) under low load conditions, and B10 can significantly improve the ITE due to the shorter combustion duration. The emission results of B10 showed that it obtained lower THC and CO emissions, but a slightly higher NOx emission. For the 80% CNG substitution rate, the results presented lower ITE, higher THC and lower NOx emissions, comparatively.

Download Full-text