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The most recent 2010 emissions standards for heavy-duty engines have established a tailpipe limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, it is projected that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (CARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions.

The classical approach to prepare engine exhaust emissions control systems for evaluation and certification is to condition the fresh parts by aging the systems on an engine/dynamometer aging stand. For diesel systems this can be a very lengthy process since the estimated service life of the emissions control systems can be several hundred thousand miles. Thus full useful life aging can take thousands of engine bench aging hours, even at elevated temperatures, making aging a considerable cost and time investment. Compared to gasoline engines, diesel engines operate with very low exhaust gas temperatures. One of the major sources of catalyst deactivation is exposure to high temperature [ 1 ].

Increasing fuel costs and the desire for reduced dependence on foreign oil has brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. The main obstacle to the increased use of diesel engines in this platform is the upcoming extremely stringent, Tier 2 emission standard. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies such as common rail fuel injection systems, low sulfur diesel fuel, NOX adsorber catalysts (NAC), and diesel particle filters (DPFs) allow the development of powertrain systems that have the potential to comply with these future requirements. In meeting the Tier 2 emissions standards, the heavy light-duty trucks (HLDTs) and medium-duty passenger vehicles (MDPVs) will face the greatest technological challenges. In support of this, the U.S.

A study was performed to develop optimum design strategies for a production V6 engine to maximize catalyst performance at minimum pressure loss and at minimum cost. Test results for an advanced system, designed to meet future emission limits on a production V6 vehicle, are presented based on FTP testing. The on-line pressure loss and temperature data serves to explain the functioning of the catalyst.

The use of a partial flow sampling system (PFSS) to measure nonroad steady-state diesel engine particulate matter (PM) emissions is a technique for certification approved by a number of regulatory agencies around the world including the US EPA. Recently, there have been proposals to change future nonroad tests to include testing over a nonroad transient cycle. PFSS units that can quantify PM over the transient cycle have also been discussed. The full flow constant volume sampling (CVS) technique has been the standard method for collecting PM under transient engine operation. It is expensive and requires large facilities as compared to a typical PFSS. Despite the need for a cheaper alternative to the CVS, there has been a concern regarding how well the PM measured using a PFSS compared to that measured by the CVS. In this study, three PFSS units, including AVL SPC, Horiba MDLT, and Sierra BG-2 were investigated in parallel with a full flow CVS.

The emission performance of a 1997 Mercedes OM 366 LA medium heavy-duty diesel engine and a 1998 Detroit Diesel Corporation (DDC) Series 60 heavy heavy-duty diesel engine was investigated using the US EPA hot-start transient cycle using different candidate diesel fuels developed by the Empresa Nacional Del Petroleo (ENAP), the state-owned oil production and refining company of Chile. The aim of the work was to identify a clean diesel fuel that can be readily produced and reduces emissions from diesel engines in Chile, particularly in Santiago Metropolitan Area where air pollution is a serious problem. Using a Mercedes engine of the type found in Chile, several candidate fuel formulations were tested in both the Mercedes and DDC engines to identify leading candidate formulations that would effectively reduce emission in both traditional and modern technology engines.

Typically, an engine/dynamometer thermal aging cycle contains combinations of elevated catalyst inlet temperatures, chemical reaction-induced thermal excursions (simulating misfire events), and average air/fuel ratio's (AFR's) to create a condition that accelerates the aging of the test part. In theory, thermal aging is predominantly a function of the time at an exposure temperature. Therefore, if a burner system can be used to simulate the exhaust AFR and catalyst inlet and bed temperature profile generated by an engine running an accelerated aging cycle, then a catalyst should thermally age the same when exposed to either exhaust stream. This paper describes the results of a study that examined the aging difference between six like catalysts aged using the Rapid Aging Test (RAT) cycle (an accelerated thermal aging cycle). Three catalysts were aged using a gasoline-fueled engine aging stand; the other three were aged using a computer controlled burner system.

The influence of catalyst volume, cell density and precious metal loading on the catalyst efficiency were investigated to design a low cost catalyst system. In a first experiment the specific loading was kept constant for a 500cpsi and a 900cpsi substrate. In a second experiment the palladium loading was reduced on the 900cpsi substrate and the same PM loading was applied to a 1200cpsi substrate with lower volume. Finally the loading was further reduced for the 1200cpsi substrate. The following parameters were studied after aging: Catalyst performance of standard cell density compared to high cell density technology Light-off performance and catalyst efficiency as a function of Palladium loading and substrate cell density Catalyst efficiency as a function of AFR biasing The performance of the aged catalysts was investigated in a lambda sweep test and in light-off tests at an engine bench.

In the United States, most school buses are powered by diesel engines. Some have advocated replacing diesel school buses with natural gas school buses, but little research has been conducted to understand the emissions from school bus engines. This work provides a detailed characterization of exhaust emissions from school buses using a diesel engine meeting 1998 emission standards, a low emitting diesel engine with an advanced engine calibration and a catalyzed particulate filter, and a natural gas engine without catalyst. All three bus configurations were tested over the same cycle, test weight, and road load settings. Twenty-one of the 41 “toxic air contaminants” (TACs) listed by the California Air Resources Board (CARB) as being present in diesel exhaust were not found in the exhaust of any of the three bus configurations, even though special sampling provisions were utilized to detect low levels of TACs.

Emissions from existing diesel-powered urban buses are increasingly scrutinized as local, state, and federal governments require enforcement of more stringent emission regulations and expectations. Currently, visual observation of high smoke levels from diesel-powered equipment is a popular indicator of potential emission problems requiring tune-up or engine maintenance. It is important that bus inspection and maintenance (I/M) operations have a quality control “test” to check engine emissions or diagnose the engine state-of-tune before or after maintenance. Ideally, the “emission test” would be correlated to EPA transient emissions standards, be of short duration, and be compatible with garage procedures and equipment. In support of developing a useful “short-test,” equipment was designed to collect samples of raw exhaust over a short time period for gaseous and particulate emissions.

Increasing fuel costs and the desire for reduced dependence on foreign oil have brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. One of the obstacles to the increased use of diesel engines in this platform is the Tier 2 emission standards. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies-such as common rail fuel injection systems, low-sulfur diesel fuel, oxides of nitrogen (NOX) adsorber catalysts or NACs, and diesel particle filters (DPFs)-allows for the development of powertrain systems that have the potential to comply with these future requirements. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity [1, 2, 3, 4, 5].

The use of compressed natural gas as an alternative to conventional fuels has received a great deal of attention as a strategy for reducing air pollution from motor vehicles. In many cases, regulatory action has been taken to displace diesel fuel with natural gas in truck and bus applications. Emissions results of heavy-duty transient FTP testing of two Cummins L10-240G natural gas engines are presented. Regulated emissions of non-methane hydrocarbons, total hydrocarbons, CO, NOx, and particulate were characterized, along with emissions of formaldehyde. The effects of air/fuel ratio adjustments on these emissions were explored, as well as the effectiveness of catalytic aftertreatment in reducing exhaust emissions. Compared to typical heavy-duty diesel engine emissions, CNG-fueled engines using exhaust aftertreatment have great potential for meeting future exhaust emission standards, although in-use durability is unproven.

Concern over emissions from heavy-duty diesel engines at high altitudes prompted an investigation into the effects of increasing altitude on gaseous and particulate emissions. On behalf of the Engine Manufacturers Association, emissions from a Detroit Diesel Corporation Series 60 at local test conditions (barometer 98.9 kPa), and two simulated altitudes, Denver (82.6 kPa) and Mexico City (77.9 kPa) were examined using a special altitude simulation CVS. Transient torque output and full load steady-state torque, for this turbocharged aftercooled engine, decreased slightly with increasing altitude. Although, the DDC Series 60 compensates for variation in barometer, transient composite emissions of HC, CO, CO2, smoke, and particulate matter generally increased with increasing altitude for both transient and steady-state operation.

Several studies have investigated the effects of diesel fuel properties on heavy-duty engine emissions. The objective of this CRC-sponsored test program was to determine the effects of oxygenated diesel fuel, and to further investigate the effects of cetane number and aromatic content on emissions from a heavy-duty engine set to obtain transient NOx emissions below 5 and then 4 g/hp-hr. A fuel set was developed with controlled variations in cetane number, aromatics, and oxygen to superette their effects on emissions. Ignition improver was used to increase cetane number of several fuels. Oxygenated diesel fuel was achieved by adding a “glyme” compound to selected fuels to obtain 2 and 4 mass percent oxygen concentrations. With these fuels, emissions were measured over the EPA transient FTP using a prototype 1994 DDC Series 60 tuned for 5 and then 4 g/hp-hr NOx. No exhaust aftertreatment device was used on this engine.

A Coordinating Research Council sponsored test program was conducted to determine the effects of diesel fuel properties on emissions from two heavy-duty diesel engines designed to meet EPA emission requirements for 1994. Results for a prototype 1994 DDC Series 60 were reported in SAE Paper 941020. This paper reports the results from a prototype 1994 Navistar DTA-466 engine equipped with an exhaust catalyst. A set of ten fuels having specific variations in cetane number, aromatics, and oxygen were used to study effects of these fuel properties on emissions. Using glycol diether compounds as an oxygenated additive, selected diesel fuels were treated to obtain 2 and 4 mass percent oxygen. Cetane number was increased for selected fuels using a cetane improver. Emissions were measured during transient FTP operation of the Navistar engine tuned for a nominal 5 g/hp-hr NOx, then repeated using a 4 g/hp-hr NOx calibration.

As stringent emission regulations further constrain engine manufacturers by tightening both NOx and particulate emission limits, a knowledge of fuel effects becomes more important than ever. Among the fuel properties that affect heavy-duty diesel engine emissions, cetane number can be very important. Part of the CRC-APRAC VE-10 Project was developed to quantify the effects of cetane number on NOx and other emissions from a prototype 1998 Detroit Diesel Series 60. Three fuels with different natural cetane number (41, 45, 52) were treated with several levels and types of cetane improvers to study a range of cetane number from 40 to 60. Statistical analysis was used to define how regulated emissions from this prototype 1998 engine decreased with chemically-induced cetane number increase. Variation of HC, CO, NOx, and PM were modeled using a combination of a fuel's naturally-occurring cetane number and its total cetane number obtained with cetane improver.

Over twenty prototype hybrid buses and other commercial vehicles are currently being completed and deployed. These vehicles are primarily “series” hybrid vehicles which use electric motors for primary traction while internal combustion engines, or high-speed turbine engines connected to generators, supply some portion of the electric propulsion and battery recharge energy. Hybrid-electric vehicles have an electric energy storage system on board that influences the operation of the heat engine. The storage system design and level affect the vehicle emissions, electricity consumption, and fuel economy. Existing heavy-duty emissions test procedures require that the engine be tested over a transient cycle before it can be used in vehicles (over 26,000 lbs GVW). This paper describes current test procedures for assessing engine and vehicle emissions, and proposes techniques for evaluating engines used with hybrid-electric vehicle propulsion systems.

Recent 2010 emissions standards for heavy-duty engines have established a limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, CARB has projected that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (ARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions. This paper details engine and aftertreatment NOX management requirements and model based control considerations for achieving Ultra-Low NOX (ULN) levels with a heavy-duty diesel engine. Data are presented for several Advanced Technology aftertreatment solutions and the integration of these solutions with the engine calibration.

The 2010 emissions standards for heavy-duty engines have established a limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, the California Air Resource Board (ARB) projects that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter (PM) and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (CARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions.

A computer controlled system capable of intercepting and performing closed-loop control of a vehicle subsystem during targeted modes of operation was developed. The system has been given the acronym ERIC, for Emissions Reduction Intercept and Control system. This study was prompted by the need for the ability to modify engine controls through targeted modes of operation, without altering the majority of engine operation, to assist in the integration of exhaust aftertreatment and engine systems. The general concept and approach for applying the ERIC method, and application of the system to perform targeted, mode-activated EGR control intercept on a 1997 Ford Crown Victoria, are described in this paper. Data are presented that demonstrate how the problem mode was identified, targeted, mapped, and modified. FTP-75 test data are presented to show the impact of this particular application.