On the Design and Optimization of a Clean and Efficient Combustion Mode for Internal Combustion Engines through a Computer NSGA-II Algorithm
FDMP-FLUID DYNAMICS & MATERIALS PROCESSING
Authors: Shu, Xiaobin; Ren, Miaomiao
Abstract
In order to address typical problems due to the huge demand of oil for consumption in traditional internal combustion engines, a new more efficient combustion mode is proposed and studied in the framework of Computational Fluid Dynamics (CFD). Moreover, a Non-dominated Sorting Genetic Algorithm (NSGA-II) is applied to optimize the related parameters, namely, the engine methanol ratio, the fuel injection time, the initial temperature, the Exhaust Gas Re-Circulation (EGR) rate, and the initial pressure. The so-called Conventional Diesel Combustion (CDC), Homogeneous Charge Compression Ignition (HCCI) and the Reactivity Controlled Compression Ignition (RCCI) combustion modes are compared. The results show that RCCI has a higher methanol ratio and an earlier injection timing with moderate EGR rate and higher initial pressure. The initial temperature increases as the methanol ratio increases. In comparison, CDC has the lowest hydrocarbon and CO emissions and the highest combustion efficiency. At different crankshaft rotation angles corresponding to 50% of the combustion amount (CA50), the combustion temperature and boundary layer temperature of HCCI change significantly, while those of RCCI undergo limited variations. At the same CA50, the exergy losses of HCCI and RCCI are lower than that of the CDC. On the basis of these findings, it can be concluded that the methanol/diesel RCCI engine can be used to obtain a clean and efficient combustion process, which should be regarded as a promising combustion mode.
Natural Gas for High Load Dual-Fuel Reactivity Controlled Compression Ignition in Heavy-Duty Engines
JOURNAL OF ENERGY RESOURCES TECHNOLOGY-TRANSACTIONS OF THE ASME
Authors: Walker, N. Ryan; Wissink, Martin L.; DelVescovo, Dan A.; Reitz, Rolf D.
Abstract
Reactivity controlled compression ignition (RCCI) has been shown to be capable of providing improved engine efficiencies coupled with the benefit of low emissions via in-cylinder fuel blending. Much of the previous body of work has studied the use of gasoline as the premixed low-reactivity fuel. However, there is interest in exploring the use of alternative fuels in advanced combustion strategies. Due to the strong market growth of natural gas as a fuel in both mobile and stationary applications, a study on the use of methane for RCCI combustion was performed. Single cylinder heavy-duty engine experiments were undertaken to examine the operating range of the RCCI combustion strategy with methane/diesel fueling and were compared against gasoline/diesel RCCI operation. The experimental results show a significant load extension of RCCI engine operation with methane/diesel fueling compared to gasoline/diesel fueling. For gasoline/diesel fueling, a maximum load of 6.9 bar gross indicated mean effective pressure (IMEPg) at CA50 = 0 deg aTDC (after top dead center) and 7.0 bar IMEPg at CA50 = 4 deg aTDC was obtained without use of exhaust gas recirculation (EGR). For methane/diesel fueling, a maximum load of 15.4 bar IMEPg at CA50 = 0 deg aTDC and 17.3 bar IMEPg at CA50 = 4 deg aTDC was achieved, showing the effectiveness of the use of methane in extending the load limit for RCCI engine operation.