Effects of ash-bridges derived from different lubricant additives on emission characteristics and performance of diesel particulate filter

The Diesel Particulate Filter (DPF) is an essential device for meeting stringent vehicle emission regulations. Ash bridges—sintered ash structures spanning DPF channel walls—represent a critical failure mode that degrades DPF performance by increasing pressure drop, fuel consumption, and particle emissions. While prior studies have characterized ash bridge morphology, but quantitative assessment of their impact under real engine conditions remains limited. This study experimentally evaluates the influence of ash bridges derived from Zn-, Ca-, Mg-, and composite-based lubricant additives on DPF pressure drop, specific fuel consumption (SFC), and filtration efficiency using an engine test bench. Ash-based DPFs were prepared via accelerated loading on a burner bench, verified in our previous work, and tested under three protocols: (1) steady-state cycles (no prior soot, to assess intrinsic resistance), (2) soot accumulation, (3) active regeneration. Results show that even without soot, ash bridges introduce significant basic pressure drop: Mg-bridged > Ca-bridged > composite-bridged > Zn-bridged > fresh DPF, governed by blockage rate and bridge position. During soot loading, Mg- and composite-based DPFs reached > 40 kPa pressure drop within 0.5–0.7 h, with SFC surging to 260–280 g/kWh, due to reduced effective volume and localized soot compaction. Regeneration responses varied: Ca-bridges maintained high resistance (flat pressure profile), Mg and composite bridges induced severe congestion effects leading to thermal run-away and sharp pressure peaks (>40 kPa), and Zn-bridges delayed pressure drop decline due to obstructed convective heat transfer shifting regeneration to a conduction-dominated process. Filtration efficiency degradation was related to load and speed: under high load or high speed, Mg-based DPFs exhibited PN efficiency < 97% due to increased wall velocity and particle blow-off/escape; Zn-based DPFs showed consistently lower efficiency due to wall breakage. Ca-based DPFs maintained high efficiency across conditions. The results provide quantitative benchmarks for optimizing lubricant formulations.