The impact of Tier 4 interim regulations goes well beyond engines, stretching to the infrastructure needed for new aftertreatment technologies. It also ripples out to the human-machine interface (HMI), which must help operators manage aftertreatment issues.
Building an infrastructure for selective catalytic reduction aftertreatment systems is a task that encompasses many fields, from manufacturing facilities through distribution. Redesigning vehicles so they meet these tight regulations is not as broadly inclusive, but it still involves many fields of expertise.
“This is very much a collaborative effort across the enterprise,” said Chris Myers, Director of Global Tractor Engineering for John Deere. "We added seven system teams." They include aftertreatment, air and exhaust gas recirculation (EGR), sensors, actuators, controls, data collection, and cooling.
Myers was among the panelists who addressed the transition from Tier 3 to Tier 4 during the SAE Commercial Vehicles Engineering Congress held in Rosemont, IL, Oct. 6-8. Engine development was a major focus of the Vehicle Integration, Service, and Aftermarket Impacts panel.
Heat rejection is a key design criterion for engines. Deere has received seven cooling and heat-rejection patents. Efficient air handling is a key aspect that helped yield a 25% improvement in heat rejection without reducing the price per kW of comparable Tier 3 engines, Myers said.
Cooling was also a critical aspect in AGCO’s engine program. The company has focused on using selective catalytic reduction instead of EGR for its Tier 4 interim solution.
“We found that since we implemented SCR this year, we were able to carry over our cooling techniques to Tier 4 interim and possibly to Tier 4 final,” said Matt Rushing, Product Management Director at AGCO. “With SCR, we were able to add horsepower and use the same cooling techniques.”
Reuse was another driving factor behind the decision to use SCR instead of EGR. It doesn’t touch engine design, so equipment can be removed when local regulations don’t require aftertreatment. “With SCR, we can take off the aftertreatment system without altering the engine for countries where compliance is not necessary,” Rushing explained.
As SCR usage expands, building an infrastructure for diesel exhaust fluids such as urea will be an important step. Chemical distributors are gearing up to build production plants and develop distribution techniques.
After the construction of urea production facilities, which cost about $1.5 billion, last-mile delivery is a critical requirement, according to Alan Duane Smith, Business Development Manager at Brenntag, a major chemical supplier. Distribution centers need to set up pumps and create containers that make it easy to get urea to vehicles. The latter is particularly important in off-highway applications.
“Packaging, delivery, and logistics are the largest percentage of the cost,” said Smith. Per gallon pricing currently begins at about $1.30 for bulk packages, rising to about $2.76 for pump delivery, he said, adding that pricing may vary as widely as does diesel fuel pricing.
The operators who buy urea or manage other aftertreatment schemes need to know when to activate them or turn them off. A critical new aspect for Tier 4 aftertreatment systems is that they must include an HMI. SCR systems must be refilled with urea, and diesel particulate filters (DPFs) must be regenerated.
The HMI for SCR is a fairly straightforward gauge. But the systems must also include techniques that will force operators to refill the tanks. Typically, engine output will be reduced when SCR tanks run low.
“On highways, when the tank is empty, the HMI will say you have this many miles before the engine goes into a derated mode,” AGCO's Rushing said. “Off highway, it will say something like you have two hours until derating.”
There are a number of considerations for DPF regeneration. Operators will often want to know when it’s time to regenerate the filter, particularly if a regeneration cycle is set to begin automatically.
Regeneration requires high exhaust temperatures, which can cause problems in some environments. “In logging, there are some concerns about high temperatures, and in a grain elevator you definitely want to eliminate regens,” said David Dunnuck, Chief Engineer for Off Highway Engine Emissions at Cummins.
Tier 4 interim requires a 90% reduction of particulate matter and a 50% decrease of NOx compared to Tier 3 levels. NOx levels decline to 2 g/kW·h, while particulate matter levels cannot exceed 0.02 g/kW·h.