Single-cylinder engine evaluation of a multi-component Diesel surrogate fuel at partially-premixed and low-temperature combustion modes

Abstract

To investigate and develop efficient and clean combustion systems, advanced CFD modeling tools need accurate kinetic models capable of predicting the chemical and physical processes that take place in the combustion chamber during and after fuel injection and air mixing. Given the complex composition of market Diesel fuels, simpler surrogate fuels composed of a limited number of pure substances are used to model the physical, chemical, and combustion properties of Diesel fuel. The surrogates must closely reproduce the market Diesel fuel properties and duplicate the real-world engine combustion and emissions behavior. Previous work created a multi-component surrogate fuel that consisted of normal-hexadecane/2,2,4,4,6,8,8-heptamethylnonane/decahydronaphthalene/1-methylnaphthalene. The surrogate fuel properties closely matched the market Diesel fuel. The surrogate fuel was then evaluated under conventional Diesel engine combustion conditions and obtained excellent results replicating the real-world combustion and emissions of the market Diesel fuel. In this work, the surrogate fuel was investigated using a contemporary Diesel engine, operating at a low-load where partially-premixed and low temperature combustion conditions were achieved. For comparison and validation, the original market Diesel fuel was also tested under the same operating conditions. The experimental results from EGR and combustion phasing sweeps under partially-premixed and low temperature combustion showed the surrogate fuel closely duplicated the ignition delay, low temperature and high temperature heat release of the market Diesel fuel. The exhaust CO, NOx and HC emissions along with the particle size distributions were also closely matched. This investigation demonstrates that the four-component surrogate accurately represents the market Diesel fuel under low load, premixed and low temperature combustion regimes. Therefore, the surrogate fuel formulation should be suitable for continued work such as kinetic mechanism development, 3-dimensional spray and combustion simulation, and further exploratory research under premixed and low temperature combustion conditions.