Comparative evaluation of conventional dual fuel, early pilot, and reactivity-controlled compression ignition modes in a natural gas-diesel dual-fuel engine
Hyunwook Park, Euijoon Shim, Junsun Lee, Seungmook Oh, Changup Kim, Yonggyu Lee, Kernyong Kang
Abstract
Conventional dual fuel (CDF), early pilot (E-Pilot), and reactivity-controlled compression-ignition (RCCI) were compared in a natural gas-diesel dual-fuel engine. The CDF mode was the most suitable for high-load operations based on its effective combustion phasing control. Furthermore, a high brake thermal efficiency (BTE) of 42.8% was achieved. However, the BTE deteriorated to 38.8% under low-load condition because of the high combustion loss of 5.1%. This high combustion loss was reduced to 3.5% and 3.3% in the E-Pilot and RCCI modes, respectively. The RCCI mode also had the lowest heat transfer loss, which achieved the highest BTE of 41.4%. However, the direction of combustion phasing control based on the diesel injection showed opposite trends to that of the CDF mode, and the engine operation was limited to the low loads. The E-Pilot mode covered medium-load operations, and its combustion phasing control was similar to that of the CDF mode. The E-Pilot mode resulted in a higher BTE of 43.1% under the medium-load condition than the CDF mode. The following strategy could be a solution considering smooth mode transitions and effective emissions reduction: E-Pilot mode for the low-to-mid load operations and CDF mode for the high load operations.