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Diesel fuel lubricity has continued to be a topic of interest for the suppliers of diesel engines, diesel fuel injection equipment, diesel fuel and diesel fuel additives. The term “lubricity” has become commonly used to mean the ability of a diesel fuel to prevent or minimize wear in diesel fuel injection equipment systems that rely on the fuel to provide lubrication. Distributor and rotary type injection pumps are examples of systems that rely totally on the fuel for lubrication. These systems are commonly used in light and medium duty diesel engines. Shell Canada has been investigating the lubricity performance of diesel fuels for a number of years. We have continued to evaluate the lubricity performance of various diesel test fuels and additives in a specifically designed distributor type pump rig that has been described previously (1, 2, 3).

The effects of fuel properties of both oil-sands-derived and conventional-crude-oil-derived diesel fuels were investigated on a single-cylinder DI research engine. The engine used in this study incorporated features of contemporary medium- to heavy-duty diesel engines and was tuned to the U.S. EPA 1994 emission standards. The engine experiments were run using the AVL 8-mode steady-state simulation of the U.S. EPA heavy-duty transient test procedure. The experimental fuels included 12 fuels blended using refinery streams to have controlled total aromatic levels and 7 other diesel fuels obtained from different sources. The results showed that at a constant cetane number (44) and sulfur content (150 ppm), oil-sands-derived fuels produced similar NOx emissions as their conventional-crude-oil-derived counterparts and total aromatic content and fuel density could be used in a regression model to predict NOx emissions.

Diesel fuels derived from different types of crude oil can exhibit different chemistry while still meeting market requirements and specifications. Oil sands derived fuels typically contain a larger proportion of cycloparaffinic compounds, which result from the cracking and hydrotreating of bitumens in the crude. In the current study, 17 refinery streams consisting of finished fuels and process streams were obtained from a refinery using 100% oil sands derived crude oil. All samples except one met the ULSD standard of 15 ppm sulfur. The samples were characterized for properties and chemistry and run in a simple premixed HCCI engine using intake heating for combustion phasing control. Results indicate that the streams could be equally well characterized by chemistry or properties, and some simple correlations are presented. Cetane number was found to relate mainly to mono-aromatic content and the cycloparaffins did not appear to possess any unique diesel related chemical effects.

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.

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.

Many modern diesel fuel injection equipment designs rely totally on the fuel to provide lubrication. The ability of a diesel fuel to lubricate diesel fuel injection equipment has become commonly referred to as its “lubricity”. If a diesel fuel has insufficient lubricity then the performance of the fuel injection equipment can be compromised resulting in reduced durability and increased vehicle emissions. We have been studying diesel fuel lubricity since the early 1990s using a test rig. The test rig consists of a motored distributor type fuel injection pump, injectors and a fuel handling/circulation system. This paper reviews test rig results on a total of twenty three different base fuels. The pump test rig results are compared to the inspection properties of the test fuels and conclusions derived.

A study was conducted to investigate the effects of diesel fuel lubricity on diesel engine fuel injection equipment (FIE) wear and failure rates, for diesel fuels with poor to moderate lubricity characteristics, with and without lubricity additives. Five tests were used to evaluate diesel fuel lubricity characteristics: 1) a modified Falex Corporation Ball-on-Three-Disk (BOTD) lubricity test rig; 2) a high-speed Detroit Diesel Corporation (DDC) 8V71T engine test rig operated at maximum load and speed conditions under elevated fuel, coolant and ambient temperatures; 3) a Wärtsilä VASA 9R32, medium-speed, diesel engine electric power generation unit in Iqaluit, Nunavut, Canada, 4) a fuel pump rig (FPR) and 5) a high frequency reciprocating rig (HFRR).

This paper describes a test program where up to eighteen diesel fuels of varying qualities were tested for cold performance in sixteen commercial diesel engines. In this study, cold performance was defined as the time to start, intensity and time of white smoke emissions after the cold start and engine knock, if present, after the cold start. Initial tests were run at -20°C with starting aids (such as block heat and/or ether use) and at -5°C with no starting aids. Subsequent tests were only run under the latter conditions, as this was found to be more discriminating regarding fuel quality effects. The diesel engines were chosen to represent the diversity of engine design in North America, Europe and the Far East. Both Direct and In-Direct Injection engines were tested as were naturally aspirated and turbocharged engines. Engine build dates varied from 1980 to 1989. This range covers most of the current diesel powered fleet in North America.

The durability and performance of diesel fuel injection equipment in actual use continues to be a concern for the manufacturers of diesel powered equipment, diesel fuel injection equipment suppliers and diesel fuel suppliers This concern has been caused by recent changes to both the equipment and the diesel fuel driven by environmental legislation The term “lubricity” has become commonly used to describe the ability of a diesel fuel to prevent or minimise wear in diesel fuel injection equipment Of particular interest are distributor and rotary type fuel injection pumps that rely totally on the fuel for lubrication These pump types are commonly used in light and medium duty diesel engines Earlier work has shown that fuels with good low temperature properties have inherently poorer lubricity performance than summer quality diesel fuels (1, 2)* Due to the need for such fuels in Canada we have been investigating the lubricity performance of winter diesel fuels for a number of years Most recently we have studied the lubricity performance of various fuels and additives in rotary type pumps and related these results to the test fuel properties, including lubricity as measured in a number of current lab bench tests

In the last few years there have been sporadic complaints regarding field failures of diesel fuel injection equipment. Upon investigation these complaints have been associated with: i) rotary or distributor type pumps as used in light and medium duty diesel engines, and ii) the use of “winter” grade diesel fuels or diesel fuels that have been altered to meet the requirements of environmental regulations. Rotary and distributor type diesel fuel pumps rely totally on the fuel for lubrication. The fuel's ability to prevent or minimize wear in these types of pumps is important. This ability has recently been referred to as the fuel's “lubricity”. Shell Canada has been investigating this issue for the past few years. Recently we have investigated the “lubricity” performance of various diesel fuels using two diesel fuel pump endurance rigs. One rig consists of two rotary type pumps, the other two distributor type pumps.

A combustion-based analytical method, initially developed by the Southwest Research Institute (SwRI) and referred to as the Constant Volume Combustion Apparatus (CVCA), has been further researched/developed by an SwRI licensee (Advanced Engine Technology Ltd.). This R&D has resulted in a diesel fuel Ignition Quality Tester (IQT) that permits rapid and precise determination of the ignition quality of middle distillate and alternative fuels. Its features, such as low fuel volume requirement, complete test automation, and self-diagnosis, make it highly suitable for commercial oil industry and research applications. A preliminary investigation, reported in SAE paper 961182, has shown that the IQT results are highly correlated to the ASTM D-613 cetane number (CN). The objective of this paper is to report on efforts to further refine the original CN model and report on improvements to the IQT fuel injection system.

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.

Three joint Government/Industry program have been reviewed to evaluate the effect of fuel properties and source on exhaust emissions from three post 1994 model year heavy-duty diesel engines, a single cylinder research engine and a prototype multicylinder engine designed to meet the 2004 model year oxides of nitrogen limit. The three post 1994 engines tested (at Environment Canada's facility) were a Detroit Diesel Series 50, a Caterpillar 3406E and a Cummins N14. Exhaust emissions of NOx, PM, CO, HC, and CO2 were measured using the “hot” US EPA Heavy-duty Transient Test Procedure. The single cylinder Ricardo Proteus research engine (run at the National Research Council of Canada) and the multicylinder Caterpillar 3176 prototype engine (run at the Southwest Research Institute) were tested using the AVL 8 mode test cycle. Fifteen fuels were tested in total: three “reference” Commercial Low Sulphur diesel fuels and twelve experimental fuels.