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A 2-D CFD model was developed to describe the heat transfer, and reaction kinetics in a honeycomb structured ceramic diesel particulate trap. This model describes the steady state as well as the transient behavior of the flow and heat transfer during the trap regeneration processes. The trap temperature profile was determined by numerically solving the 2-D unsteady energy equation including the convective, heat conduction and viscous dissipation terms. The convective terms were based on a 2-D analytical flow field solution derived from the conservation of mass and momentum equations (Opris, 1997). The reaction kinetics were described using a discretized first order Arrhenius function. The 2-D term describing the reaction kinetics and particulate matter conservation of mass was added to the energy equation as a source term in order to represent the particulate matter oxidation. The filtration model describes the particulate matter accumulation in the trap.

The prediction of particulate concentrations in dlesel exhaust diluted in a dilution tunnel has been achieved using a computer model. The particulate collection filter temperature, soluble organic fraction (SOF) and solids fraction (SOL) of diesel particulate matter were predicted based on exhaust system and dilution tunnel variables that could be measured on a real-time basis. The SOF was assumed to be formed by adsorption of gaseous hydrocarbons onto the solids fraction. The accuracy of the model was determined by comparison to experimentally measured values. The model was able to predict SOF concentrations within 35%, filter temperatures within 3°G, and particulate (SOF + SOL) concentrations within 25% of measured values. A parametric study was conducted using the developed model; and improved test procedures, dilution tunnel dimensions, and federal testing guidelines were suggested.

Studies have been conducted at Michigan Technological University (MTU) for over twenty years on methods for characterizing and controlling particulate emissions from heavy-duty diesel engines and the resulting effects on regulated and unregulated emissions. During that time, control technologies have developed in response to more stringent EPA standards for diesel emissions. This paper is a review of: 1) modern emission control technologies, 2) emissions sampling and chemical, physical and biological characterization methods and 3) summary results from recent studies conducted at MTU on heavy-duty diesel engines with a trap and an oxidation catalytic converter (OCC) operated on three different fuels. Control technology developments discussed are particulate traps, catalysts, advances in engine design, the application of exhaust gas recirculation (EGR), and modifications of fuel formulations.

A computational lumped parameter model (MTU-Filter-Lumped) was developed to describe the performance of diesel particulate filters (DPFs) during loading and regeneration processes. The model was formulated combining three major sub-models: a filtration model, a pressure drop model, and a mass and an energy balance equation for the total filter volume. The first two sub-models have been widely validated in the literature, while the third sub-model is introduced and combined with the first two sub-models in the present study. The three sub-models combined can give a full description of diesel particulate filter behavior during loading and regeneration processes, which was the objective of the present work. The total combined lumped parameter model was calibrated using experimental data from the literature covering a range of experimental conditions, including different catalytic regeneration means and engine operating conditions.

Various measurement techniques were employed to quantify sulfuric acid deposition levels and concentration of sulfuric acid in the condensate from the recirculated exhaust gas heat exchanger of a 1995 Cummins M11 heavy-duty diesel engine. Methods employed included a modified version of the sulfur species sampling system developed by Kreso et al. (1)*, rinsing the heat exchanger, and experiments employing a condensate collection device (CCD). The modified sampling system was applied to the inlet and outlet of the heat exchanger in order to quantify the changes in various sulfur compounds. Doped sulfur fuel (3300 to 4000 ppm S) was used to increase the concentrations of the various oxides of sulfur (SOx). These tests were performed at mode 9 of the old EPA 13-mode test cycle (1800 RPM, 932N*m) with 17-20% exhaust gas recirculation (EGR) at two EGR outlet temperatures: 160°C and 103°C.

A cooperative test program was conducted by the CRC-APRAC CAPI-1-64 Composition of Diesel Exhaust Program Group to evaluate the technical aspects of a proposed EPA recommended Heavy Duty Diesel Emission Measurement and Test Procedure. The proposed changes affected the sampling configurations and the types of instruments used. Six participants studied the effects of a number of variables on the proposed changes and evaluated some alternative systems that included both CHEMI and NDIR instruments. The tests were conducted at one site using a multi-cylinder engine operating on the 13-Mode Cycle. Equivalency of systems was demonstrated and the best performance was obtained with a special NDIR system.

A thermal management system for heavy duty diesel engines is presented for maintaining acceptable and constant engine temperatures over a wide range of operational conditions. It consists of a computer controlled variable speed coolant pump, a position controlled thermostat, and a model-based control strategy. An experimentally validated, diesel engine cooling system simulation was used to demonstrate the thermal management system's capability to reduce power consumption. The controller was evaluated using a variety of operating scenarios across a wide range of loads, vehicle speeds, and ambient temperatures. Three metrics were used to assess the effects of the computer controlled system: engine temperature, energy savings, and cab temperature. The proposed control system provided very good control over the engine coolant temperatures while maintaining engine metal temperatures within a desired range.

The development of the DDC methanol engine has been an evolutionary process, with each subsequent configuration showing significant durability and/or emission improvement over its predecessor. Sixty demonstration engines are now in service in the field, including fifty-four (54) urban bus engines, five (5) truck engines, and one (1) generator set engine. While nitrogen oxide (NOx) and particulate emissions from the methanol engine are inherently low, a durable solution to the effective control of hydrocarbon (HC) emissions has been an especially challenging area. The 1991 Federal urban bus transient emission standards (including 0.10 gm/bhp-hr particulate) have been met with several combinations of compression ratio, intake port height, exhaust valve cam profile, injector tip design, and electronic control strategies, and without exhaust aftertreatment devices or fuel ignition improvers.

A computer simulation program was developed to simulate the thermal responses of an on-highway, heavy duty diesel powered truck in transient operation for evaluation of cooling system performance. Mathematical models of the engine, heat exchangers, lubricating oil system, thermal control sensors (thermostat and shutterstat), auxiliary components, and the cab were formulated and calibrated to laboratory experimental data. The component models were assembled into the vehicle engine cooling system model and used to predict air-to-boil temperatures. The model has the capability to predict real time coolant, oil and cab temperatures using vehicle simulation input data over various routes.

A wide range of emissions were characterized from a heavy-duty diesel engine operated on conventional low sulfur (∼375 ppm) fuel, equipped with manually controlled EGR and a catalyzed particulate filter (CPF). The effect of the CPF and engine load was studied, along with a comparison of results between the gravimetric and thermal optical methods (TOM) for determining diesel particulate levels. Data were obtained from four of the EPA old 13 mode test cycle steady-state operating conditions, i.e., Modes 11, 10, 9, and 8 using a 1995 Cummins M11-330E engine with a Corning EX-80 cordierite particulate filter, coated with a platinum catalyst (5 g/ft3).

In this study, the effects of an oxidation catalytic converter (OCC) on regulated and unregulated emissions from a 1991 prototype Cummins I.10-310 diesel engine fueled with a 0.01 weight percent sulfur fuel were investigated. The OCC's effects were determined by measuring and comparing selected raw exhaust emissions with and without the platinum-based OCC installed in the exhaust system, with the engine operated at three steady-state modes. It was found that the OCC had no significant effect on oxides of nitrogen (NOX) and nitric oxide (NO) at any mode, but reduced hydrocarbon (HC) emmissions by 60 to 70 percent. The OCC reduced total particulate matter (TPM) levels by 27 to 54 percent, primarily resulting from 53 to 71 percent reductions of the soluble organic fraction (SOF). The OCC increased sulfate (SO42-) levels at two of the three modes (modes 9 and 10), but the overall SO42- contribution to TPM was less than 6 percent at all modes due to the low sulfur level of the fuel.

This paper discusses the evaluation and application of a portable parked-vehicle tailpipe emissions measurement apparatus (EMA). The EMA consists of an exhaust dilution system and a portable instrument package. The EMA instantaneously dilutes and cools a sample of exhaust with compressed nitrogen or air at a known dilution ratio, thereby presenting it to instruments as it is presented to personnel in the surrounding environment. The operating principles and governing equations of the EMA are presented. A computational method is presented to determine the engine operating and performance parameters from the exhaust CO2 concentrations along with an assumed engine overall volumetric efficiency and brake specific fuel consumption. The parameters determined are fuel/air ratio, mass flow rates of fuel, air and exhaust emissions, and engine brake torque and horsepower.

Steady state loading characterization experiments were conducted at three different engine load conditions and rated speed on the cracked catalyzed particulate filter (CPF). The experiments were performed using a 10.8 L 2002 Cummins ISM-330 heavy duty diesel engine. The CPF underwent a ring off failure, commonly seen in particulate filters, due to high radial and axial temperature gradients. The filters were cracked during baking in an oven which was done to regenerate PM collected after every loading characterization experiment. Two different configurations i.e. with and without a diesel oxidation catalyst (DOC) upstream of the CPF were studied. The data were compared with that on an un-cracked CPF at similar engine conditions and configurations. Pressure drop, transient filtration efficiency by particle size and PM mass and gaseous emissions measurements were made during each experiment.

A 2-dimensional numerical model (MTU-FILTER) for a single channel of a honeycomb ceramic diesel particulate trap has been developed. The mathematical modeling of the filtration, flow, heat transfer and regeneration behavior of the particulate trap is described. Numerical results for the pressure drop and particulate mass were compared with existing experimental results. Parametric studies of the diesel particulate trap were carried out. The effects of trap size and inlet temperature on the trap performance are studied using the trap model. An approximate 2-dimensional analytical solution to the simplified Navier-Stokes equations was used to calculate the velocity field of the exhaust flow in the inlet and outlet channels. Assuming a similarity velocity profile in the channels, the 2-dimensional Navier-Stokes equations are approximated by 1-dimenisonal conservation equations, which is similar to those first developed by Bissett.

A study was conducted to assess the effects of a water-diesel fuel emulsion with and without an oxidation catalytic converter (OCC) on steady-state heavy-duty diesel engine emissions. Two OCCs with different metal loading levels were used in this study. A 1988 Cummins L10-300 heavy-duty diesel engine was operated at the rated speed of 1900 rpm and at 75% and 25% load conditions (EPA modes 9 and 11 respectively) of the 13 mode steady-state test as well as at idle. Raw exhaust emissions' measurements included total hydrocarbons (HC), oxides of nitrogen (NOx) and nitric oxide (NO). Diluted exhaust measurements included total particulate matter (TPM) and its primary constituents, the soluble organic (SOF), sulfate (SO42-) and the carbonaceous solids (SOL) fractions. Vapor phase organic compounds (XOC) were also analyzed. The SOF and XOC samples were analyzed for selected polynuclear aromatic hydrocarbons (PAHs).

The effects of an oxidation catalytic converter (OCC), an emulsified fuel, and their combined effects on particle number and volume concentrations compared to those obtained when using a basefuel were studied. Particle size and particulate emission measurements were conducted at three operating conditions; idle (850 rpm, 35 Nm), Mode 11 (1900 rpm, 277 Nm) and Mode 9 (1900 rpm, 831 Nm) of the EPA 13 mode cycle. The individual effects of the emulsified fuel and the OCC as well as their combined effects on particle number and volume concentrations were studied at two different particle size ranges; the nuclei (less than or equal to 50 nm) and accumulation (greater than 50 nm) modes. An OCC loaded with 10 g/ft3 platinum metal (OCC1) and a 20% emulsified fuel were used for this study and a notable influence on the particle size with respect to number and volume distributions was observed.

An analysis of vehicle engine cooling airflow by means of a one-dimensional, transient, compressible flow model was carried out and revealed that similarity theory could be applied to investigate the variation of the airflow with ambient and operating conditions. It was recognized that for a given vehicle engine cooling system, the cooling airflow behavior could be explained using several dimensionless parameters that involve the vehicle speed, fan speed, heat transfer rate through the radiator, ambient temperature and pressure, and the system characteristic dimension. Using the flow resistance and fan characteristics measured from a prototype cooling system and the computer simulation for the one-dimensional compressible flow model, a quantitative correlation of non-dimensional mass flow rate to three dimensionless parameters for a prototype heavy-duty truck was established. The results are presented in charts, tables, and formulas.

The objective of this research was to obtain diesel particle size distributions from a 1988 and a 1991 diesel engine using three different fuels and two exhaust control technologies (a ceramic particle trap and an oxidation catalytic converter). The particle size distributions from both engines were used to develop models to estimate the composition of the individual size particles. Nucleation theory of the H2O and H2SO4 vapor is used to predict when nuclei-mode particles will form in the dilution tunnel. Combining the theory with the experimental data, the conditions necessary in the dilution tunnel for particle formation are predicted. The paper also contains a discussion on the differences between the 1988 and 1991 engine's particle size distributions. The results indicated that nuclei mode particles (0.0075-0.046 μm) are formed in the dilution tunnel and consist of more than 80% H2O-H2SO4 particles when using the 1988 engine and 0.29 wt% sulfur fuel.

The effect of a Johnson Matthey catalyzed continuously regenerating technology™ (CCRT®) filter on the particle size distribution in the raw exhaust from a 2002 Cummins ISM-2002 heavy duty diesel engine (HDDE) is reported at four loads. A CCRT® (henceforth called DOC-CPF) has a diesel oxidation catalyst (DOC) upstream (UP) of a catalyzed particulate filter (CPF). The particle size data were taken at three locations of UP DOC, downstream (DN) DOC and DN CPF in the raw exhaust in order to study the individual effect of the DOC and the CPF of the DOC-CPF on the particle size distribution. The four loads of 20, 40, 60 and 75% loads at rated speed were chosen for this study. Emissions measurements were made in the raw exhaust chosen to study the effect of nitrogen dioxide and temperature on particulate matter (PM) oxidation in the CPF at different engine conditions, exhaust and carbonaceous particulate matter (CPM) flow rates.

The effect of fuel changes on diesel oxidation catalyst performance was studied by comparing the physical, chemical and biological character of the particulate emissions using three different fuels. Baseline (uncatalyzed) emissions were also compared for these same fuels. The fuels used for this study were: a typical No. 2 fuel, a No. 1 fuel, and a shale oil-derived diesel fuel. Comparisons of NOX, NO, NO2, HC and particulate mass emissions using each fuel were made using selected modes from the EPA 13 mode cycle. Changes in the chemical and biological character of the soluble organic fraction (SOF) were also studied. Fuel properties, most notably fuel sulfur content, were found to affect the performance of the oxidation catalyst used. Fuel sulfur content should be kept as low as possible if catalytic converters are used on diesel powered equipment.