Terry L. Ullman

Effects of Fuel Aromatics, Cetane Number, and Cetane Improver on Emissions from a 1991 Prototype Heavy-Duty Diesel Engine

Several diesel identified as having significant effects on diesel engine emissions. This paper reports, for heavy-duty diesel engines, fuel properties of aromatics, back end volatility (represented by the 90 percent boiling point), and sulfur examined in a previous CRC VE-1 study in which reductions in all three properties decreased regulated emissions to varying degrees. Aromatic levels and cetane numbers were generally correlated in the previous study, so variation in emissions due to aromatics could not clearly be assigned to variation in aromatic levels alone. To separate the effects of aromatics and cetane number, a fuel set with controlled variation in aromatics and cetane number was developed, including the use of ignition improver to increase the cetane number of selected fuels. The fuel set was used in a 1991 Prototype DDC Series 60 heavy-duty diesel engine to examine regulated emissions over EPA transient cycle operation. Results indicate that cetane number was the key fuel property affecting transient HC and CO emissions. In addition, cetane number was the principal fuel property affecting composite particulate emissions, but aromatic effects were also significant. For emissions of NO{sub x} both cetane number and aromatics were significant for transient emissions.

Investigation of the Effects of Fuel Composition on Heavy-Duty Diesel Engine Emissions

Models for transient composite emissions were obtained using multiple linear regression techniques, and changes to regulated emissions for selected changes in fuel properties were estimated from the models. Decreasing fuel aromatic content, sulfur, and volatility (increasing 90 percent boiling point temperature) were generally associated with reductions to regulated emissions

Simulation of High Altitude Effects on Heavy-Duty Diesel Emissions

Exhaust emissions from heavy-duty diesel engines operating at high altitude are of concern. EPA and Colorado Department of Health sponsored the project to characterize regulated and selected unregulated emissions from a naturally-aspirated Caterpillar 3208 and a turbocharged Cummins NTC-350 diesel engine at both low and simulated high altitude conditions (about 6000 ft). Emissions testing was performed over cold- and hot-start transient cycles as well as selected steady-state modes. Additionally, the turbocharged engine was operated with mechanically variable and fixed retarded fuel injection timing to represent normal and malfunction conditions, respectively. High altitude operation generally reduced NOx emissions approximately 10% for both engines. Average composite transient emissions of HC, CO, particulate matter, and aldehydes measured at high altitude for the naturally-aspirated engine were 2 to 4 times the levels noted for low altitude conditions. The same emission constituents from the turbocharged engine at high altitude with normal timing were 1.2 to 2 times the low altitude levels, but were 2 to 4 times the low altitude levels with malfunction timing.

The Texas diesel fuels project, part 1: Development of TxDOT-specific test cycles with emphasis on a "route" technique for comparing fuel/water emulsions and conventional diesel fuels

The Texas Department of Transportation (TxDOT) began using an emulsified diesel fuel in July 2002. They initiated a simultaneous study of the effectiveness of this fuel in comparison to 2D on-road diesel fuel, which they use in both their on-road and off-road equipment. The study also incorporated analyses for the fleet operated by the Associated General Contractors (AGC) in the Houston area. Some members of AGC use 2D off-road diesel fuel in their equipment. The study included comparisons of fuel economy and emissions for the emulsified fuel relative to the conventional diesel fuels. Cycles that are known to be representative of the typical operations for TxDOT and AGC equipment were required for use in this study. Four test cycles were developed from data logged on equipment during normal service: 1) the TxDOT Telescoping Boom Excavator Cycle, 2) the AGC Wheeled Loader Cycle, 3) the TxDOT Single-Axle Dump Truck Cycle, and 4) the TxDOT Tandem-Axle Dump Truck Cycle. As is conventional for heavy-duty engines, the first two of these cycles are specified in terms of percent torque and percent engine speed versus time for engine dynamometer testing. The latter two cycles are specified in terms of vehicle speed versus time for chassis dynamometer testing. Due to the torque loss associated with the water in the emulsified fuel, there was concern that conventional means for comparing the two fuels would result in less work performed by the engine over the cycle when operating on the emulsified fuel. The inadequacies of traditional speed versus time test cycles, when applied to heavy-duty vehicles where power-to-weight ratio can change greatly, have been recognized for some time (1, 2). Speed versus distance test routes have been developed using icons as simple driver instructions (3), using free accelerations in a traditional speed versus time environment (4), and using sequences of distanced-based phases (5). For this study, a route technique was developed for testing the dump trucks. The route technique assures equal distances traveled for each micro-trip and for the overall cycle independent of the fuel. For engine dynamometer testing, the same command cycle was used to assure the same work was requested over the cycle independent of the fuel.

The Texas Diesel Fuels Project, Part 2: Comparisons of Fuel Consumption and Emissions for a Fuel/Water Emulsion and Conventional Diesel Fuels

The Texas Department of Transportation began using an emulsified diesel fuel in 2002. They initiated a simultaneous study of the effectiveness of this fuel in comparison to 2D on-road diesel fuel and 2D off-road diesel. The study included comparisons of fuel economy and emissions for the emulsion, Lubrizol PuriNOx®, relative to conventional diesel fuels. Two engines and eight trucks, four single-axle dump trucks, and four tandem-axle dump trucks were tested. The equipment tested included both older mechanically-controlled diesels and newer electronically-controlled diesels. The two engines were tested over two different cycles that were developed specifically for this project. The dump trucks were tested using the route technique over one or the other of two chassis dynamometer cycles that were developed for this project In addition to fuel efficiency, emissions of NOx, PM, CO, and HCs were measured. Additionally, second-by-second results were obtained for NOx and HCs. Speciation of the HC emissions was performed for one of the off-road engines operating over two different cycles. On average, over all engines and cycles, PuriNOx provided a NOx benefit of about 16%, a fuel efficiency penalty of about 17%, and a PM benefit of about 20%. In general, the NOx benefit and the fuel efficiency penalty were less pronounced for the electronically-controlled diesels. One truck engine/cycle combination was found for which the effect on NOx was not statistically significant at the 95% confidence level. Similarly, two engine/cycle combinations were found for which the effect on PM was not statistically significant, and there was a statistically significant increase in PM for one dump truck. PuriNOx produced significant increases in the emissions of roughly half of the Toxic Air Contaminants evaluated: formaldehyde, acetaldehyde, acrolien, and MEK. PuriNOx did not yield decreased emissions of any TACs.

Emissions from two methanol-powered buses

Emissions from the two methanol-powered buses used in the California Methanol Bus Demonstration have been characterized. The M.A.N. SU 240 bus is powered by M.A.N.s D2566 FMUH methanol engine, and utilizes catalytic exhaust aftertreatment. The GMC RTS II 04 bus is powered by a first-generation DDAD 6V-92TA methanol engine without exhaust aftertreatment. Emissions of HC, CO, NO/subX/, unburned methanol, aldehydes, total particulates, and the soluble fraction of particulate were determined for both buses over steady-state and transient chassis dynamometer test cycles. Emission levels from the M.A.N. bus were considerably lower than those from the GMC bus, with the exception of NO/subX/. Comparison of emission levels from methanol-and diesel-powered buses indicates that substantial reductions in emissions are possible with careful implementation of methanol fueling.

Emissions Performance of Two Catalyzed Trap Oxidizers on a Bus Engine

Performances antipollution de deux filtres a particules avec oxydation catalytique pour moteurs de bus

HEAVY-DUTY DIESEL EMISSIONS AS A FUNCTION OF ALTERNATE FUELS

Exhaust emissions from a Mack EM6-300 heavy-duty diesel engine were characterized with five different fuels during transient and steady-state operation. A control fuel (Phillips D-2) was used for baseline emissions, and as a base stock in three alternate fuel blends containing EDS or SRC-II middle distillates or used lubricating oil. The fifth fuel tested was neat soybean oil, heated to 145 degrees. Emission measurements included HC, CO, CO2, NOx, visible smoke, particulate, IHC, aldehydes, odor (DOAS), phenols, sulfate, elemental composition, particle sizing, SOF, SOF boiling point distribution, BaP, Ames bioassay and HPLC fractionation. HC, CO, NOx and particulate emissions were similar for this engine on all fuels tested with exception of higher particulates for the soybean oil and higher NOx for the SRC-II blend. Ames response was highest for the EDS and SRC-II blends. The BaP level was highest for the soybean oil.

Heavy-duty diesel emissions from operation on crude and minimally-processed shale oils

Three crude shale oils were chosen from six candidates to investigate their possible use as substitutes for No. 2 diesel fuel. Satisfactory hot engine operation was achieved on the crudes using a fuel heating system, allowing emissions characterization during transient and steady-state operation. Regulated gaseous emissions changed little with the crudes compared to diesel fuel; but total particulate and soluble organics increased, and larger injector tip deposits and piston crown erosion were observed. After engine rebuild, two minimally-processed shale oils were run without the fuel heating system, causing no engine problems. Most emissions were higher than for No. 2 fuel using and 80 percent distillate of crude shale oil, but lower using a hydrotreated form of the distillate.