Emission analysis of a compressed natural gas directinjection engine with a homogenous mixture

Abstract

In an era in which environmental pollution and depletion of world oil reserves are of major concern, emissions produced by automotive vehicles need to be controlled and reduced. An ideal solution is to switch to a cleaner fuel such as natural gas, which generates cleaner emissions. In addition, control over the in-cylinder air-fuel mixture can be best achieved through a direct-injection mechanism, which can further improve combustion efficiency. This need for cleaner automobiles provides the motivation for this paper's examination of the use of computational fluid dynamic (CFD) simulations to analyze the concentrations of the exhaust gases produced by a compressed natural gas engine with a direct-fuel-injection system. In this work, a compressed natural gas direct-injection engine has been designed and developed through a numerical simulation using computational fluid dynamics (CFD) to provide an insight into complex in-cylinder behavior. The emissions analyzed in this study were carbon monoxide (CO), nitric oxide (NO) and carbon dioxide (CO 2 ), i.e. the main pollutants produced by natural gas combustion. Based on a stoichiometric mixture, the concentrations of CO and NO were computed using the dissociation of carbon dioxide and the extended Zeldovich mechanism. CO 2 was calculated using a mass balance of the species involved in the combustion process. The simulation results were then compared with the experimental data generated by a single-cylinder research engine test rig. A good agreement was obtained with the experimental data for the engine speeds considered for all emissions concentrations.

Compressed Natural Gas Direct Injection: Comparison Between Homogeneous and Stratified Combustion

“…[1,2,11]. The simulation was performed on a combustion chamber of the engine cylinder speciied in Table 1 for a stoichiometric air-fuel mixture.…”

“…It is understood that coniguring conventional ICEs to improve eiciency while reducing exhaust emissions is diicult where strategies to improve engine eiciency will eventually increase harmful emissions, such as carbon monoxide (CO) and nitrogen oxides (NO x ) [2]. The signiicant advantage that compressed natural gas (CNG) has in antiknock quality is related to the higher auto-ignition temperature and higher octane number compared to that of gasoline.…”

Performance and Emissions of a Methane Fueled V-Twin Four Stroke Spark Ignited Engine

“…Rising oil prices and a global emphasis on the reduction of pollution has prompted the search for an alternative fuel sources [1][2][3][4][5][6]. The development of Compressed Natural Gas (CNG) engines is a solution to help alleviate dependence on oil and reduce emissions caused by the transportation sector.…”

Effects of the ignition timing retard and the compression ratio on the full-load performance and the emissions characteristics of a heavy-duty engine fuelled by hydrogen–natural-gas blends

“…Compressed-natural-gas (CNG) engines and vehicles were developed that can meet the Euro V standard on emissions by employing advanced lean combustion, and their performance and emissions characteristics were significantly improved in comparison with the previous data. 1,2 However, because the level of regulation for nitrogen oxides (NO x ) will become more stringent with the implementation of the Euro VI standard (from 2014), which will require the NO x emissions to be lowered to about 80% of the values in the Euro V standard, commercial natural-gas engines cannot satisfy the NO x requirements of Euro VI using only lean combustion. Thus, an additional after-treatment system for reducing the NO x emissions must be installed.…”