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The influence of fuel aromatics type on the particulate matter (PM) and NOx exhaust emissions of a heavy-duty, single-cylinder, DI diesel engine was investigated. Eight fuels were blended from conventional and oil sands crude oil sources to form five fuel pairs with similar densities but with different poly-aromatic (1.6 to 14.6%) or total aromatic (14.3 to 39.0%) levels. The engine was tuned to meet the U.S. EPA 1994 emission standards. An eight-mode, steady-state simulation of the U.S. EPA heavy-duty transient test procedure was followed. The experimental results show that there were no statistically significant differences in the PM and NOx emissions of the five fuel pairs after removing the fuel sulphur content effect on PM emissions. However, there was a definite trend towards higher NOx emissions as the fuel density, poly-aromatic and total aromatic levels of the test fuels increased.

The CRC Fuels for Advanced Combustion Engines working group has worked to identify a matrix of research diesel fuels for use in advanced combustion research applications. Nine fuels were specified and formulated to investigate the effects of cetane number aromatic content and 90% distillation fraction. Standard ASTM analyses were performed on the fuels as well as GC/MS and1H/13C NMR analyses and thermodynamic characterizations. Details of the actual results of the fuel formulations compared with the design values are presented, as well as results from standard analyses, such as heating value, viscosity and density. Cetane number characterizations were accomplished by using both the engine method and the Ignition Quality Tester (IQT™) apparatus.

The latent heat-of-vaporization (HoV) of blends of biofuel and hydrocarbon components into gasolines has recently experienced expanded interest because of the potential for increased HoV to increase fuel knock resistance in direct-injection (DI) engines. Several studies have been conducted, with some studies identifying an additional anti-knock benefit from HoV and others failing to arrive at the same conclusion. Consideration of these studies holistically shows that they can be grouped according to the level of fuel octane sensitivity variation within their fuel matrices. When comparing fuels of different octane sensitivity significant additional anti-knock benefits associated with HoV are sometimes observed. Studies that fix the octane sensitivity find that HoV does not produce additional anti-knock benefit. New studies were performed at ORNL and NREL to further investigate the relationship between HoV and octane sensitivity.

This paper reports the development of new fuel ignition quality and combustion experiments performed using the Ignition Quality Tester (IQT). Prior SAE papers (961182, 971636, 1999-01-3591, and 2001-01-3527) documented the development of the IQT constant volume combustion chamber experimental apparatus to measure ignition qualities of diesel-type fuels. The ASTM International test method D6890 was developed around the IQT device to allow the rapid determination of derived cetane number (DCN). Interest in chemical kinetic models for the ignition of diesel and biodiesel model compounds is increasing to support the development of advanced engines and fuels. However, rigorous experimental validation of these kinetic models has been limited for a variety of reasons. Shock tubes and rapid compression machines are typically limited to premixed gas-phase studies, for example.

The exhaust emissions from a single-cylinder version of a heavy-duty diesel engine with exhaust gas recirculation (EGR) were studied using 12 diesel fuels derived from oil sands and conventional sources. The test fuels were blended from 22 refinery streams to produce four fuels (two from each source) at three different total aromatic levels (10, 20, and 30% by mass). The cetane numbers were held constant at 43. Exhaust emissions were measured using the AVL eight-mode steady-state test procedure. PM emissions were accurately modeled by a single regression equation with two predictors, total aromatics and sulphur content. Sulphate emissions were found to be independent of the type of sulphur compound in the fuel. NOx emissions were accurately modeled by a single regression equation with total aromatics and density as predictor variables. PM and NOx emissions were significantly significantly affected by fuel properties, but crude oil source did not play a role.

The effects of cetane number, aromatics content and 90% distillation temperature (T90) on HCCI combustion were investigated using a fuel matrix designed by the Fuels for Advanced Combustion Engines (FACE) Working Group of the Coordinating Research Council (CRC). The experiments were conducted in a single-cylinder, variable compression ratio, Cooperative Fuel Research (CFR) engine. The fuels were atomized and partially vaporized in the intake manifold. The engine was operated at a relative air/fuel ratio of 1.2, 60% exhaust gas recirculation (EGR) and 900 rpm. The compression ratio was varied over the range of 9:1 to 15:1 to optimize the combustion phasing for each fuel, keeping other operating parameters constant. The results show that cetane number and T90 distillation temperature significantly affected the combustion phasing. Cetane number was clearly found to have the strongest effect.