Cost of the new engine relative to gasoline baseline. Source: Cummins. Click to enlarge.

The 4-year project is scheduled to wrap up in September of this year. The technical focus over the last year has been on new engine installation and performance assessments. In 2013, the Cummins-led team demonstrated a Tier 2 Bin 5 version of the engine on the dyno, and then on a vehicle, while development of the Tier 2 Bin 2 engine started.

So far this year, the team has integrated the T2B2 aftertreatment in the dynamometer environment and is in the process of convert the demonstration vehicle to the T2B2 configuration. Demonstration of T2B2 at the tailpipe is slated for later this year.

So far, Ruth noted, the new engine has achieved target engine-out emissions (EOE), performance and fuel economy; aftertreatment catalyst performance has met or exceeded the targeted conversion rates, enabling an increased allowance on engine out HC.

The approach that Cummins and partners have taken features:

• Replacing the aluminium V8 gasoline engine and emission control system with smaller diesel (2.8-liter) and its emission control system (ECS) without a weight penalty. Cummins made extensive use of aluminium as well as space-saving design features for new engine weight control. The aluminum block and head is sandwiched between an iron backbone cam carrier and iron ladder frame base, firmly held with iron-to-iron bolts.

  Lightweight steel pistons provide reduced friction & compression height with increased power density.

  Cummins achieved its weight-neutral goal based on a gasoline engine with emission control system (ECS) weight of 514 lbs (233 kg); the new aluminum 2.8L diesel weighs 362 lbs (164 kg), while the ECS weighs 152 lbs (69 kg).

• Taking learnings from LTD and LDECC programs to utilize PCCI (pre-mixed charge compression ignition) and high charge flow operation.

• Low pressure EGR; Johnson Matthey’s Cold Start Concept (CSC) catalyst for cold start NO_x & HC mitigation; an NH₃ gas system from Amminex (earlier post) for immediate reductant delivery; and a small engine running higher loads resulting in faster warm-up all contribute to reducing the fuel economy penalty for meeting the more stringent emissions target.

  Johnson Matthey’s new CSC stores HC and NO_x at low temperatures with very high storage efficiencies, and also converts a significant portion of the stored HC/NO_x during the warm-up period before the rest of the HC/NO_x is thermally released from the catalyst. The HC/NO_x release temperature in a cold start catalyst is high enough that the released HC/NO_x can be further converted by the downstream catalytic components. In addition, the cold start catalyst also exhibits excellent CO, HC, and NO oxidation activity under normal lean conditions.

Exhaust system configuration. SCR coated on filter (SCR-F) allows for close coupling of an SCR (selective catalytic reduction) function for fast light off. The Amminex direct ammonia delivery system (DADS) can further improve NOx conversion performance by reducing the time delay before NH3 introduction after cold start. DADS also allows for multiple NH3-dosing locations, which allows for the integration of additional under-floor SCR elements to mitigate infrequent regeneration adjustment factors (IRAF). Source: Cummins. Click to enlarge.

The team has achieved T2B5 vehicle engine out emissions as well as T2B2 test cell engine out emissions when running dual loop EGR. Further, the first demo vehicle has demonstrated T2B5 with margin without the aid of the full dCSC and LP EGR, while maintaining fuel economy above the target.

The work remaining will see the full engine move to Johnson Matthey for refinement of the CSC operation, and refinement of the overall aftertreatment control strategy. Purdue University will work with the team on variable valve train options for warm up and HC control, all leading to the final T2B2 demonstration on a complete, street worthy, driveable vehicle.

Resources
(DOE will publish Merit Review presentations on its website.)

• Michael Ruth (2014) “ATP-LD; Cummins Next Generation Tier 2 Bin 2 Diesel Engine” DOE 2014 Annual Merit Review, Project ACE061

• Chen, H., Mulla, S., Weigert, E., Camm, K. et al. (2013) “Cold Start Concept (CSC): A Novel Catalyst for Cold Start Emission Control,” SAE Int. J. Fuels Lubr. 6(2):372-381 doi: 10.4271/2013-01-0535