As heavy truck and engine makers continue to plan for EPA\u2019s phase 2 emission reduction and fuel efficiency rules in 2018, some engineers are already thinking beyond that \u2013 specifically how suppliers continue to balance fuel economy and NOx reduction compliance for future benchmarks.<\/p>\n
From CCJ<\/em>:<\/p>\n \u201cAs people get more and more fixated about CO2 or fuel economy standards, it\u2019s also going to raise a question,\u201d Dr. Steve Golden, chief technology officer for Clean Diesel Technologies, Inc., says. \u201cThis beautiful over-engineered emissions system, how\u2019s it going to have to evolve to be consistent with the engine calibration changing, or [to get] better fuel economy, because all kinds of things have to change about engine design to get better fuel economy. How does that impact the next generation after treatment system?\u201d<\/p>\n Jackie Yeager, Cummins\u2019 global energy policy director, says the company is already mulling how it will rise to meet Phase II at benchmarks in 2021, 2024 and 2027.<\/p>\n \u201cWe\u2019ve talked about building on the architecture you see today with our engines,\u201d she says, \u201cwith EGR, DPF and SCR. That all stays, of course, because you have to meet NOx.\u201d<\/p>\n Yeager says making the same kind of base engine improvements \u2013 like combustion optimization, better air handling, reducing friction, reducing parasitic loads and after treatment efficiency improvement \u2013 will be a big part of the strategy, as will looking at the benefits and feasibility of waste heat recovery.<\/p>\n Golden adds fuel efficiency requirements included in Phase II will challenge engine builders seeking to preserve low NOx emissions.<\/p>\n \u201cThere are significant tradeoffs in getting lower NOx,\u201d he says, noting a higher combustion temperature helps drive fuel efficiency while also creating more NOx. \u201cHow can you do that and have better fuel economy? You can\u2019t get the best of both worlds. You have to make compromises.\u201d<\/p>\n Furthermore, there\u2019s also the consideration that once OEMs hit the 2027 benchmark, the EPA is likely to continue its push for further limits.<\/p>\n \u201cI don\u2019t know what\u2019s out there beyond Phase II for sure, but we know [CARB] is talking about a lower NOx standard that they need to be able to meet the federal ambient air quality standards for ozone,\u201d Yeager says. \u201cSo they\u2019re talking about possibly new NOx standards for heavy duty engines, and they\u2019re throwing out numbers as low as .02 compared to the .2 gram NOx that we\u2019re at today. So, another 90 percent reduction.\u201d<\/p>\n The potential of another 90 percent reduction of NOx would pose one of the biggest challenges for engineers to-date, according to Golden.<\/p>\n \u201cIf I have a more efficient engine, it\u2019s hotter and I have more NOx and that increases the cost of my after treatment system for NOx,\u201d he says. \u201cIf I get lower CO2 with a higher combustion temperature, I\u2019m going to have more NOx.\u201d<\/p>\n \u201cWanting to maintain the efficiency gains on the engine that we\u2019ve made over the past years, it would be a challenge to go to a lot lower on NOx,\u201d Yeager adds, \u201cbut we need to do some research and we need to do some work on what those tradeoffs are and what would be the costs associated with a new NOx standard, what the technologies are and that kind of thing.\u201d<\/p>\n