Diesel Particulate Filter (DPF) Testing

Increasingly stringent environmental regulations for diesel engine emissions are driving efforts to develop concepts for reducing emission levels, predominantly for particulate matter (PM). The US federal limit for PM emissions from heavy-duty diesel engines has decreased from 0.1 g/hp-hr to 0.01 g/hp-hr for 2007. The use of diesel particulate filters (DPFs) is considered to be the only feasible diesel aftertreatment technology for achieving the US 2007/2010 and Euro V particulate limits.

Southwest Research Institute® (SwRI®), with more than 50 years of experience in engine, fuel and vehicle research, offers complete facilities for testing diesel engines and their aftertreatment systems.

Thermocouple installation on a diesel particulate filter for performance evaluation

CAPABILITIES

Institute engineers combine state-of-the-art equipment with extensive DPF experience to provide engine manufacturers and component suppliers with comprehensive services, including:

• DPF filtration efficiency measurement
• Catalyst formulation evaluation
• Balance point tests (for catalyzed DPFs)
• Precise on-engine DPF PM loading techniques
• Automated DPF regeneration using supplemental fuel injection (SFI) or in-cylinder post-injection
• Regeneration survivability tests
• Long-term ash accumulation
• DPF hot vibration testing
• On-vehicle DPF durability testing
• Off-engine DPF cleaning techniques
• Application-specific troubleshooting (e.g., solutions for DPF plugging)

Diesel particulate filter (DPF) testing on a light-duty engine

Comparison of DPF inlets with and without a flow diffuser following multiple loading and regeneration cycles

Instrumentation

Engine test benches can include numerous instruments to aid in determining the performance characteristics of DPFs:

• Gaseous emissions analyzers for HC, CO, CO₂, NO_x, and O₂
• PM size and number distributions for accurate filtration efficiency measurements
• PM-soluble organic fraction (SOF) content analysis
• SwRI methodology for measuring real-time temperature distributions in DPFs
• DPF pressure-drop characteristics
• ECU mapping for DPF loading / regeneration performance

Measurement of real-time DPF trapping efficiency as a function of particle size, showing distinction in trapping efficiency between “clean” and “loaded” DPFs

Two thermal-related risks during DPF regeneration

Survivability Tests

Successful regeneration of the DPF under any given engine operating condition has been identified by industry as a major challenge. SwRI can perform DPF survivability evaluations based on three regeneration failure types:

• Type A – Excess exotherm at the start of regeneration due to rapid temperature ramping rate
• Type B – Combination of excessive PM loading, high O₂  concentration, and low exhaust flow rate (“classic runaway regeneration”)
• Type C – Uneven temperature distribution during regeneration causing incomplete regeneration

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