Search Results

A first order empirical model relating filter efficiency and internal combustion engine wear (focused on diesel engine wear) was assembled. The model combines the wear mechanisms from an engine's lube oil, fuel, and air induction systems, with ambient, application, and service conditions to predict specific results. This area of study is known as: Total Filtration™. The predictions possible to date using the Total Filtration™ model include: changes in lube oil and fuel consumption, changes in particulate matter (PM) emissions, a profile of PM emissions by source, normalized wear ratings, and engine life. Model case studies are reviewed and specific prediction examples are provided.

An electrically regenerated trap system has been developed based on the use of multiple filter tubes. The design individually isolates a filter tube during regeneration through the use of a newly developed poppet valve. The regeneration process is quickly completed by integrating the heaters and filter tubes together. The need for external combustion air has been eliminated. Also, the trap replaces the function of the muffler. The controller uses a simple algorithm basing regeneration need on easily measured parameters. The trap system operates on 12 volts. A system was installed on a pickup truck for field test purposes. Data collected from the onboard logging system, including electrical system impact and trap performance are reviewed.

An approach has been developed for the design and optimization of combined catalytic converter - mufflers for low emission diesel engines. The development of this optimizing process considered the effects of the substrate and it's properties, the flow distribution through the substrate, the total system backpressure, and it's acoustical behavior. The actual catalyst formulation is not considered in this optimization process, as this development approach focuses on other converter muffler performance issues. For a given engine and vehicle combination this design approach has fostered the determination of the appropriate substrate size, the correct level of flow uniformity, and sufficient exhaust noise attenuation, all within the appropriate back pressure limit. The resulting optimization process has proved to be a valuable tool in the development of converter mufflers for diesel applications.

A diesel generator set was used as a long term durability test for an exhaust particulate trap oxidizer system. The single trap (wall flow monolith) system was exposed to two 3000 hour tests. The tests included 20 minute engine cycles of varying speeds and loads, with complete monitoring of trap performance during loading and regeneration. The two tests differed in the type of lubricating oil and fuel used. The first test used a relatively high ash oil and regular sulfur fuel. The second test used an ashless oil and low sulfur fuel. The affects on the ceramic filter performance over the extended test times were dramatically different. The regular sulfur fuel and high ash of the first test resulted in a trap almost completely filled with ash. The low sulfur fuel and ashless oil of the second test had only 6% by mass of the ash collected in the previous test.

Trap oxidizer systems for the filtration and oxidation of diesel exhaust particulate have been built and tested for a number of heavy-duty diesel applications. System design has been focused on electrically heated bypassed regeneration using wall flow monolith filters, and microprocessor based control for real time determination of particle mass on the trap. The durability of such systems has been demonstrated in the laboratory, in the engine test cell, and on vehicle applications. An accelerated durability test bench was developed for the purpose of assessing the system's (and especially the ceramic core's) ability to withstand a lifetime of thermal regeneration cycles. The results confirm previous projections regarding ceramic core life. A complete trap oxidizer system was manufactured and installed on a generator set test cell designed specifically to expose trap oxidizer systems to actual exhaust conditions for long term durability studies.

Systems have been developed for medium and heavy duty diesel engines, which perform the combined operations of exhaust particle collection, trap regeneration, and exhaust noise attenuation. These systems are microprocessor based and fully automatic requiring no operator intervention. The developmental efforts centered on the use of a vehicle voltage, electrically heated bypassed regeneration technique. One of the keys to achieving successful system operation, reliability and durability was the regeneration control algorithm. This program monitors trap status in a particle accumulation mode and restrains the rate and intensity of the regeneration reaction by limiting the amount of oxygen availability in a regeneration mode, resulting in the avoidance of ceramic filter damage. The design of the systems were enhanced by the use of several analytical tools, including: computational fluid dynamic flow analysis, regeneration thermal profile prediction, and finite element stress analysis.

Several different diesel particulate filter (DPF) structures have been characterized for filtration performance. The physical structures of the DPF ceramic materials considered are dramatically different (i.e. deep foam bed, thin fibrous nonwoven. thin porous extrusion). Due to these differences in structure and the way these DPFs are applied. different filtration mechanisms dominate the collection of diesel exhaust particulates. Laboratory measurements of ceramic DPFs were made including: particle collection efficiency versus particle size and total pressure loss at several velocities. Good correlations between modeled behavior and laboratory experiments have been achieved, indicating that the OPF structures have been accurately characterized. A detailed understanding of a DPF structure leads to an improved knowledge of its filtration behavior and a better DPF system design.