Reducing particulate emissions from diesel engines has become a major challenge for regions of Europe, Japan and the United States. Many mobile applications have been successfully addressed with passively regenerating wall flow filters. However stationary engines, locomotives and other large constant speed engines often require a different approach to particulate filtration. Flow-through filter technologies have merit for these applications due to their low maintenance requirements, tolerance to misfueling and suitability for engines with high specific PM emissions. When considering the application of a particulate filter to any diesel engine the means of regeneration, or combustion of the accumulated soot, is of critical importance. In the case of filters which are regenerated through the use of a catalytic coating the duty cycle of the engine, and characteristics of the exhaust gas itself dictate the potential success or failure of the system. In many cases interruption of operation, whether due to insufficient regeneration rates, or for scheduled service to remove accumulated ash, is relatively more difficult to accept for locomotive and non-mobile engine operations. Locomotives, power generators and the like often accumulate large number of service hours between scheduled maintenance events and perform tasks where interruption of service can have costly consequences. Details of an investigation into the suitability of a flow-through filter for heavy-duty constant speed engines are presented. Aspects of the design, including materials selection, catalyst coating and performance under various conditions are discussed. Results from CFD and micro-dilution tunnel particulate sampling of full-scale devices support the progressive refinement of the design.
Reduction of particulate matter emissions from diesel powered locomotives and stationary engines has become of great interest to regulatory agencies. Regulatory standards for emissions on NOx, hydrocarbons and diesel particulate matter (DPM) have recently been approved [2,3]. A stationary engine is described by the US-EPA as an engine that is not mobile [1,2]. The final rule - New Source Performance Standards (NSPS) will reduce emissions by 90% from 2005 to 2015. Stationary engine emissions are currently handled on a case-by-case basis and are dependent on air quality regulations of the region. In the near future, new stationary engines with less than 10 liters displacement per cylinder in the U.S. will be required to meet the EPAs nonhighway DPM standard (Tables 1 and 2). Pre-2007 engines with less than 10 liters per cylinder will be required to meet the non-road Tier 1 emission standards.