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The evolution and explanation of an approach to achieving a stated set of very low emissions limits was described in a previous paper (1)*. The method outlined was to use stoichiometric mixture preparation with EGR dilution in order to employ a 3-way catalyst for low emissions, whilst giving an engine power output competitive with a turbocharged diesel engine. This approach has been followed in an engine development programme, which has resulted in a responsive and driveable engine being produced. The engine has demonstrated the achievability of very low emissions over the US heavy duty diesel transient test (FTP) cycle as follows: The lean-burn approach to low emission heavy duty operation has also been considered, using steady-state engine test results. The NOx-HC trade-off has been identified as a key indicator of engines' potential, and is also considered to give an indication of the accuracy of air-fuel ratio control required to achieve proposed emissions standards.

There is a strong request for heavy-duty gas engines in the Nordic countries for environmental reasons. Therefore, several research projects are going on. This paper describes two of them: a Finnish Sisu truck and a MAN bus, both operating in the city of Espoo, the hometown of the Technical Research Centre. The truck is equipped with a 7.4 litre Finnish Valmet 612 engine. The development work has included engine tests and tests with a vehicle in laboratory conditions. A 3,3 litre 3-cylinder engine was used for the engine tests. The engine runs on stoichiometric mixture, and has a three-way catalyst based on metal substrate. The engine was run on both methane (compr. ratio 12:1) and propane (compr. ratio 10:1). Emissions were extremely low with both fuels. In the European 13-mode test 0.4 g CO, 0.1 g HC and 0.1 g NOx per kWh were achieved. Peak thermal efficiency was 35 % for both fuels. Maximum mean effective pressure (BMEP) for a naturally aspirated engine is 9 - 9,5 bar.

Soot accumulation in diesel engine crankcase is the dominant factor which governs engine oil drain interval. So, efficient soot elimination from crankcase oil can be a practical way to achieve drain interval extension. Combination of high performance oil filter and low soot dispersancy oil results in an effective measure to trap soot efficiently. In this paper, the behavior of newly developed high performance diesel engine oil having low soot dispersancy is reported. Prior to oil development, an evaluation method of soot dispersancy in oil was elaborated. Based on relative viscosity defined as ratio of soot containing oil viscosity to soot eliminated oil viscosity, dispersancy parameter was determined. Oil dispersancy evaluated on this parameter agreed with the results obtained from particle size analyzer. Secondly, a method to obtain oil filter soot trap rate to total soot contaminated into crankcase (trap rate) was established.

A GL-5 gear lubricant containing a dispersed solid borate additive and a CD synthetic engine lubricant were evaluated in the overdrive transmissions of 17 new Class 8 trucks in a 500,000-mile per truck, on-highway field test. With 500,000-mile oil drain intervals, both lubricants gave acceptable performance as judged by end-of-test inspections: deposit/sludge formation was minimal, overall wear was low, and seal/yoke performance was good. The borate lubricant gave a statistically significant lower wear rate than the synthetic lubricant based upon oil sample analysis; inspections also showed lower wear on some parts. Additionally, oil sample analysis from the tandem drive axles showed that the forward axle gave a statistically significant higher wear rate than the rear axle. Transmission and drive axle oil temperatures were monitored during a portion of the test.

The effects of diesel fuel properties and composition have been investigated in an advanced, low emissions, Detroit Diesel Corporation (DDC) Series 60 engine. The test results have revealed that particulates emissions in the U.S. transient test are governed mainly by fuel sulphur content and fuel density. The density effect is due to overfuelling of the engine which may result from how the cycle is calibrated and from how heavy-duty engines are governed under transitional operation. The model developed from these data correlates well with other published data and confirms the general case that fuel density, rather than aromatics content, is - with fuel sulphur - the dominant factor affecting exhaust particulates. The analysis of particulates composition supports these findings but reveals an additional fuel parameter, volatility, which has a minor second-order effect on particulates emissions.

MAN and Shell have jointly investigated the effect of fuel properties on exhaust emissions from advanced engine technologies. MAN Nutzfahrzeuge AG, the Austrian subsidiary Steyr Nutzfahrzeuge AG and Deutsche Shell AG started this bilateral cooperation in 1990 with the objective of identifying key fuel properties that influence emissions from a MAN heavy-duty engine meeting the EURO-I legislation. The intention of that investigation was to determine the effect of cetane number, total and poly-aromatics content and backend distillation [T90] on particulates and gaseous emissions. In parallel both companies participated in the EPEFE (European Program on Emissions, Fuels and Engine Technologies) program which provided a broader understanding of fuel effects on emissions with different engine technologies under European test conditions.

The objective of this project, which is supported by the U.S. Department of Energy (DOE) through the National Renewable Energy Laboratory (NREL), is to provide a comprehensive comparison of heavy-duty trucks operating on alternative fuels and diesel fuel. Data collection from up to eight sites is planned. This paper summarizes the design of the project and early results from the first two sites. Data collection is planned for operations, maintenance, truck system descriptions, emissions, duty cycle, safety incidents, and capital costs and operating costs associated with the use of alternative fuels in trucking.

Fuel is the single largest operating expense for a diesel truck fleet. This paper presents data on the many factors which affect consumption, and on the ways in which fuels and additives can contribute to minimizing it. Fuel density is the key fuel parameter affecting consumption, since higher density fuels deliver more energy per litre than those of lower density. Diesel cold flow improver additives can play an important role in the economic production of diesel fuel. In addition, they allow the production of higher density fuels while maintaining good low temperature performance. Dynamometer test data are presented to show the effects of ambient temperature, vehicle speed and fuel density on consumption. The performance of flow improver additives in improving low temperature operability while maximizing density is demonstrated.

A first retrofit conversion of a Cummins NTC335 engine to spark ignition was carried out in New Zealand in 1984. The conversion used widely available technology for stoichiometric control of natural gas fuel - air mixtures. Experience from the on-road application in a 40,000 kg GVW truck contributed much to the later development of a 400 hp gas-fuelled variant of the same engine family, using lean mixture carburettion control. A second engine entered service in a logging application in February 1989. The following paper summarises results arising from laboratory testing of the second engine, and from in-field monitoring. Also presented are preliminary results from testing of a third generation engine, using timed multi-point injection of gas fuel.

Several diesel fuel properties have been identified as having significant effects on diesel engine emissions. For heavy-duty diesel engines, fuel properties of aromatics, back end volatility (represented by the 90 percent boiling point), and sulfur were 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.

A program to explore the effects of natural and additive-derived cetane on various aspects of diesel performance and combustion has been carried out. Procedures have been developed to measure diesel engine fuel consumption and power to a high degree of precision. These methods have been used to measure fuel consumption and power in three heavy-duty direct-injection diesel engines. The fuel matrix consisted of three commercial fuels of cetane number (CN) of 40-42, the same fuels raised to CN 48-50 with a cetane improver additive, and three commercial fuels of base CN 47-50. The engines came from three different U.S. manufacturers and were of three different model years and emissions configurations. Both fuel economy and power were found to be significantly higher for the cetane-improved fuels than for the naturally high cetane fuels. These performance advantages derive mainly from the higher volumetric heat content inherent to the cetane-improved fuels.

Regina Transit has operated two ethanol fuelled buses since March 1991. On-road performance and operator acceptance has been good, with few maintenance problems. Volumetric fuel consumption is close to twice that of similar diesel buses. In comparison to a similar diesel bus, emissions tests on a chassis dynamometer have shown reductions in NOx and Particulate emissions over four typical test cycles. However, in three cases CO emissions were higher. OMHCE emissions were consistently higher, largely due to the level of unburned ethanol in the exhaust. The buses were not fitted with catalytic converters at the time of testing.

A heavy-duty 320 kW diesel engine has been converted to natural gas operation. Conversion technology was selected to minimize costs while reaching NOx emissions goals of less than 3.2 g/kW-hr. Two engines are being converted using quiescent and high swirl combustion systems. The first engine with low swirl cylinder heads of the base diesel engine, and a combustion system developed for it was tested on a steady state cycle that has been shown to simulate the US heavy duty transient test cycle. It shows NOx emissions of 2.9 g/kW-hr and total HC emissions of 5.4 g/kW-hr. It is suspected that the HC emission is high because of high valve overlap. Experience with other similar engines suggests that non-methane HC emission is about 0.4-0.8 g/kW-hr. It is also expected that modified valve events and/or an oxidation catalyst can reduce HC emissions to much lower levels. The efficiency of the low swirl natural gas engine at this NOx level is 36 percent at rated condition.

The Natural Gas Vehicle (NGV) Challenge '92, was organized by Argonne National Laboratory. The main sponsors were the U.S. Department of Energy the Energy, Mines, and Resources - Canada, and the Society of Automotive Engineers. It resulted in 20 varied approaches to the conversion of a gasoline-fueled, spark ignited, internal combustion engine to dedicated natural gas use. Starting with a GMC Sierra 2500 pickup truck donated by General Motors, teams of college and university student engineers worked to optimize Chevrolet V-8 engines operating on natural gas for improved emissions, fuel economy, performance, and advanced design features. This paper focuses on the results of the emission event, and compares engine mechanical configurations, engine management systems, catalyst configurations and locations, and approaches to fuel control and the relationship of these parameters to engine out and tailpipe emissions of regulated exhaust constituents.

Total aromatics have no influence on particulate emissions. This is an unexpected finding from a comprehensive programme to determine the influence of diesel fuel properties on heavy-duty particulate emissions. 30 fuels and five engines representing a variety of manufacture/technology were tested. To reveal causative influences, key fuel properties were intentionally uncorrelated and had a wide range of values. Engine sensitivities to fuel quality were found to differ considerably. Properties that most influenced emissions were sulphur content, density and cetane number. Some engines were totally insensitive to polyaromatics but in others, small influences are possible. The emissions benefits of specific fuel property changes are quantified.

Flow-through diesel oxidation catalysts (DOC's) have been shown to be an effective means of reducing emissions from diesel engines. In this work, the further development of diesel oxidation catalysts for the control of emissions from heavy duty engines is illustrated. Laboratory reactor and engine dynamometer data obtained from engine-based accelerated poisoning and aging studies demonstrate that HC, CO and SO2 oxidation by DOC's can be modified by adjusting platinum and vanadium loadings in alumina-based Pt/V catalyst formulations. The performance and durability of this type of catalyst system are demonstrated with several aging cycles on heavy-duty engines. The fresh performance of two catalyst systems was determined on both US Heavy Duty Transient and ECE-R49 Test cycles with a 1991 calibration Perkins Phaser 6.0 L engine. Gas phase emissions were reduced by a similar amount for both catalysts over both cycles (HC: 60-70%, CO: 45-75%).

Recent global environmental problems which have come to light must be solved for ensuring the survival of the human race. And it is of the utmost importance that we give to our descendants a world full of nature and beauty. In the past years Mitsubishi Motors Corporation (MMC) has long been positive in research and the development activities so as to satisfy the demands for low emission and good fuel economy vehicles. (1) As one example of our research efforts, the technology that will meet the US '94 HDDE exhaust emission regulations, which is one of the most stringent regulations in the world, is described in this paper. The exhaust emissions were reduced by improvement of combustion, using the pre-stroke control type fuel injection pump and optimizing the combustion chamber shape. Efforts were also made to improve the oil consumption, in order to reduce PM (Particulate Matter) emission.

Propane is considered to be a viable fuel alternative for low-emission heavy-duty vehicles in Finland. Natural gas and propane have roughly the same potential for reduced exhaust emissions. Since natural gas and propane are both imported fuels in Finland, there is no preference between these two fuels. Propane, however, is much more easy to distribute, refuel and store onboard the vehicle. This is why propane has received more attention than natural gas as an automotive fuel. Work to develop a low-emission propane fueled truck started back in 1988 with engine tests. The first prototype, a 17-ton SISU truck was built in 1990, and was operated until September 1992. This truck was equipped with a 7.4-liter Valmet-engine, a closed-loop controlled IMPCO-fuel system and a three-way catalytic converter (TWC). The experience with this propane fueled truck was good. The driveability was excellent, and both noise level and exhaust emissions were low.

A heavy-duty, naturally aspirated diesel engine was converted into a turbocharged, aftercooled, compressed natural gas engine. Engine test results show that excess air ratio and ignition timing strongly affect NOx and THC emissions. Leaning the air-fuel mixture reduces NOx emission, but it increases THC emission and combustion becomes unstable above a certain excess air ratio. Retarding the ignition timing reduces both the NOx and THC emissions. Dual-plug ignition improves brake thermal efficiency. The NOx emission level can be reduced to meet the Japanese long-term emission regulation limit for heavy-duty gasoline engines with a sufficient safety margin by appropriately selecting the air-fuel ratio and ignition timing so as to keep the THC emission level below the regulation limit without using any after-treatment. The engine full torque characteristics were almost the same as the base engine throughout the engine speed range, while the maximum exhaust gas temperature was lower.

The West Virginia University (WVU) Transportable Heavy-Duty Vehicle Emissions Testing Laboratory was employed to conduct chassis dynamometer tests in the field to measure the exhaust emissions from heavy-duty buses and trucks. This laboratory began operation in the field in January, 1992. During the period January, 1992 through June, 1993, over 150 city buses, trucks, and tractors operated by 18 different authorities in 11 states were tested by the facility. The tested vehicles were powered by 14 different types of engines fueled with natural gas (CNG or LNG), methanol, ethanol, liquified petroleum gas (LPG), #2 diesel, and low sulfur diesel (#1 diesel or Jet A). Some of the tested vehicles were equipped with exhaust after-treatment systems. In this paper, a total of 12 CNG-fueled and #2 diesel-fueled transit buses equipped with Cummins L-10 engines, were chosen for investigation.