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As governmental agencies focus on low levels of the oxides of nitrogen (NOx) emissions compliance, new off-road applications are being reviewed for both regulated and unregulated emissions to understand the technological challenges and requirements for improved emissions performance. The California Air Resources Board (CARB) has declared its intention to pursue more stringent NOX standards for the off-road market. As part of this effort, CARB initiated a program to provide a detailed characterization of emissions meeting the current Tier 4 off-road standards [1]. This work focused on understanding the off-road market, establishing a current technology emissions baseline, and performing initial modeling on potential low NOx solutions. This paper discusses a part of this effort, focuses on the emissions characterization from two non-road engine platforms, and compares the emissions species from different approaches designed to meet Tier 4 emissions regulations.

Semi-volatile organic compounds (SVOC) are a group of compounds in engine exhaust that either form during combustion or are part of the fuel and lubricating oil. Since these compounds occur at very low concentrations in diesel engine exhaust, the methods for sampling, handling, and analyzing these compounds are critical to obtaining good results. An improved dilute exhaust sampling method was used for sampling and analyzing SVOC in engine exhaust, and this method was performed during transient engine operation. A total of 22 different SVOC were measured using a 2012 medium-duty diesel engine. This engine was equipped with a stock diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst in series. Exhaust concentrations for SVOC were compared both with and without exhaust aftertreatment. Concentrations for the engine-out SVOC were significantly higher than with the aftertreatment present.

Semi-volatile organic compounds (SVOC) are a group of compounds that may form during combustion and/or are present in the unburned portion of the fuel and lubricating oil which ultimately become part of the exhaust. Many of these compounds are considered toxic or carcinogenic. Since these compounds are present in very low concentrations in diesel engine exhaust, the methods for sampling, handling, and analyzing these compounds are critical to obtaining representative and repeatable results. Engine testing is typically performed using a dilution tunnel. With a dilution tunnel, the collection of a representative sample is important. Experiments were performed with a modified EPA Method TO-9A to determine the equilibration time and other sampling parameters required for the measurement of SVOC in dilute exhaust. The results show that representative results can be obtained with this method.

Newly designed Teflon® O-rings along with XAD-2 resin, stainless steel screens, lock rings, and glass cartridges were used to construct a new semi-volatile organic compounds (SVOC's) sampling device. This new sampling device allows direct and repeated sampling, extraction, and cleaning without ever having to be disassembled or reassembled. This new XAD-2 glass cartridge (X2) was compared with three other sampling methods namely Empore® membrane (EM), hexane impinger (HI), and “Cold Trap” (CT) for SVOC sampling efficiency on diesel engine exhaust emissions. The X2 method showed the highest overall SVOC collection efficiency, followed by the EM and HI methods. The X2 method has higher trapping efficiency for the oxygenates, polycyclic aromatic hydrocarbons (PAH's), alkyl cyclohexanes, and the alkyl aromatics than the other three SVOC sampling methods. The HI method has the highest trapping efficiency for the normal alkanes.

Sulfur and aromatic compounds in diesel fuel impact the emissions profile of current diesel engines. Fuels that do not contain these components can be made from natural gas using Fischer-Tropsch chemistry. Very little data has been presented comparing the emissions characteristics of current low sulfur diesel to fuels with ultra low levels of sulfur and aromatics in passenger car diesel engines. This study reports on an exhaust emission comparison of currently available conventional diesel fuel to Fischer Tropsch diesel fuel free of aromatics and sulfur comparisons included regulated emissions, air toxics, aldehydes and ketones, particle size distribution, and greenhouse gas emissions. Testing was conducted on a current model diesel passenger car using a chassis dynamometer. Regulated emissions were analyzed according to the Code of Federal Regulations (CFR) Title 40 specifications and requirements of the Environmental Protection Agency (EPA) Federal Test Procedure (FTP).

This study compared four different candidate fuels which were prepared by blending different components with a typical No. 2 diesel. Two fuels were blended with a synthetic diesel prepared from natural gas condensate, and all candidate fuels were splash blended with a proprietary additive package from International Fuel Technology Inc. (IFT). These fuels were then compared to the No. 2 diesel and to a California Air Resources Board (CARB) equivalent diesel fuel. The comparisons included fuel properties such as sulfur content, aromatics, cetane, lubricity, distillation; emissions; and fuel consumption. Emission testing was conducted on a 1991 Detroit Diesel Series 60. The Environmental Protection Agency (EPA) transient cycle was utilized for emissions, fuel characterization was performed according to ASTM standards, and fuel consumption was calculated by the carbon balance method.

Results of engine bench tests on a 1998 heavy-duty diesel engine have confirmed the emissions reduction performance of a U.S. Environmental Protection Agency (EPA) registered platinum/cerium bimetallic fuel borne catalyst (FBC) used with several different catalyzed and uncatalyzed diesel particulate filters (DPF's). Performance was evaluated on both a 450ppm sulfur fuel (No.2 D) and a CARB 50ppm low sulfur diesel (LSD) fuel. Particulate emissions of less than 0.02g/bhp-hr were achieved on several combinations of FBC and uncatalyzed filters on 450ppm sulfur fuel while levels of 0.01g/bhp-hr were achieved for both catalyzed and uncatalyzed filters using the FBC with the low sulfur CARB fuel. Eight-mode steady state testing of one filter and FBC combination with engine timing changes produced a 20% nitrogen oxide (NOx) reduction with particulates (PM) maintained at 0.01g/bhp-hr and no increase in measured fuel consumption.