The next best short-term option for meeting ultra-low NOx requirements is diesel.
May 20, 2021 | Diesel Technology Forum
Continued stewardship of ICE technology is paramount to cleaner air and progress on reducing GHG emissions, which is why leaders in technology continue to innovate and improve this workhorse.
Buried somewhere beneath the myriad of coming-soon headlines on the all-electric future, are a few kernels of developments from our old friend the Internal Combustion Engine (ICE for short) of which the diesel is a proud representative. Today’s diesel engine is the prime mover of the global economy, and will be for some time, according to a full range of experts. This makes continued stewardship of ICE technology paramount to cleaner air and progress on reducing greenhouse gas emissions, which is why leaders in technology continue to innovate and improve this workhorse.
First, there is going to be a demand for more ICE, and they must be cleaner. Recent research from Frost and Sullivan notes that “Original equipment manufacturers (OEMs) are exploring advanced internal combustion engine concepts, energy recovery systems, advanced aerodynamics, and cutting-edge driver assistance systems to improve fuel efficiency. Globally, 2.37 million powertrain units are expected to be sold by 2030 that will include 1.8 million units of diesel powertrain, 0.57 million units of xEV (which includes hybrid, plug-in hybrid, battery-electric, and fuel cell electric vehicles), and natural gas powertrains."
Second, while some might think it is an awkward time to introduce a new internal combustion engine, Achates Power has done just that, with its opposed piston engine that can run on a variety of fuels (gas, diesel, or hydrogen). Recent news suggests considerable optimism for the testing - Walmart fleet testing the world's 'cleanest combustion engine' | Commercial Carrier Journal (ccjdigital.com). ”While official fuel efficiency numbers aren’t available yet, Fromm said miles per gallon 'will be at least 7 percent better because that's the kind of CO2 improvement we're seeing on the dyno.'
...the tall 10.6-liter can achieve the California Air Resource’s Board ultra-low NOx standard of 0.02 grams per brake horsepower hour and meet EPA’s 2027 CO2 requirement…” Achates engines utilize Tenneco’s advanced components and systems, specialized coatings and proprietary manufacturing processes help to reduce emissions, improve fuel economy and enable advances in engine design.
Third, ICE innovation for diesel comes in many forms, in this case getting the cleanest combustion possible. Caterpillar, a global leader in advanced diesel engines, teamed up with Argonne’s National Laboratories’ high-performance computing resources, where researchers developed a potential piston design for Caterpillar’s engines that could improve fuel efficiency while reducing harmful emissions. The team first created a framework to optimize combustion system design using a 3D computational fluid dynamics tool called CONVERGE, developed by Convergent Science, Inc. Merging heat transfer and combustion data derived from CONVERGE models with environmental data on soot and nitrogen oxide (NOx) production, they then ran hundreds of high-fidelity simulations to develop promising designs for piston bowls - the combustion chambers in diesel engines.
Another example of ICE innovation is adapting a relatively newer technology from passenger vehicles - cylinder deactivation - for diesel engines. By precisely controlling cylinder combustion and matching it to power demands and emissions and fuel efficiency factors, an 8-cylinder engine can be programmed to run on only 4 cylinders during steady-state highway operation, reducing engine work and fuel consumption during certain operating modes. Leading engine manufacturer Cummins working with Tula, have unveiled the results of their collaborative study on the effectiveness of Tula’s diesel Dynamic Skip Fire (dDSF) in reducing nitrogen oxides (NOx) and carbon dioxide (CO2) emissions on a Cummins X15 HD Efficiency Series diesel engine.
This system showed a 74 percent reduction in NOx and a 5 percent reduction in CO2 compared with today’s clean diesel technologies. In comparison with current engine technologies and modifications to the thermal management techniques, dDSF saved 20 percent in fuel, validating dDSF as a more fuel-efficient means of reducing NOx. “Tula’s dDSF technology provides significant benefits to reducing NOx and CO2 emissions under low-load vehicle operation, which will “aid our efforts to produce more reliable, more powerful engines while meeting our environmental goals,” says Lisa Farrell, director of accelerated technology at Cummins Inc.
Dynamic Skip Fire (DSF) is an advanced cylinder deactivation control strategy that makes decisions for an engine’s cylinders on an individual basis to best meet torque demands while saving fuel and maintaining performance. Tula’s original DSF software has been shown to significantly reduce CO2 emissions in gasoline engines and has been in production since 2018 with more than one million vehicles on the road.
Future engine emissions requirements will dictate that diesel’s low-emissions performance must be assured at all points of vehicle operation, which has proven challenging during some low-speed, low load driving patterns of heavy-duty commercial trucks, where selective catalytic reduction (SCR) NOx treatment systems are operating at less than optimum conversion efficiency.
Tenneco, a global leader in powertrain and complete emissions systems, aims to change this dynamic with it’s Cold Start Thermal Unit (CSTU) that will be combined with Eaton’s TVS® blower technology. The integrated exhaust thermal management system will provide heat directly to the vehicle’s aftertreatment system, which is essential for reducing harmful exhaust emissions. Upon heating the SCR catalyst to approximately 200 – 250 degrees Celsius, the aftertreatment system can efficiently convert NOx into clean emissions (e.g., nitrogen and water particles) upon exiting the SCR catalyst. Eaton’s electrically driven TVS Roots blower allows the airflow to be efficiently and precisely controlled so the CSTU can maintain optimal aftertreatment temperatures.
“CSTU is an active thermal management technology that rapidly heats and maintains the emission control system temperature,” said Nick Morley, director, global advanced engineering, Tenneco’s Clean Air business group. “Since the majority of emissions are generated during the initial start of engine operation and during extended idle conditions, the addition of an integrated exhaust thermal management system in front of the catalyst enables rapid light-off and efficient NOx conversion through the full range of operating conditions.”
Bosch, a leader in a range of vehicle technologies including engine management systems, fuel injectors and aftertreatment systems, also has a focus on fuels. Bosch sees a place for renewable synthetic fuels and hydrogen fuel cells alongside electrification. Renewable synthetic fuels made from hydrogen are a different technology from hydrogen fuel cells. Fuel cells use hydrogen to generate electricity, while hydrogen-derived fuels can be combusted in a modified internal combustion engine (ICE).
“Climate action is not about the end of the internal-combustion engine,” said Denner, in comments reported recently by the Financial Times. “It’s about the end of fossil fuels. And while electromobility and green charging power make road transport carbon neutral, so do renewable fuels. Additionally, Bosch board member Stefan Hartung said that the company “will continue to invest in combustion engine technology for at least another 20-30 years.”
General Motors announced January 2021 that it is aiming at 2035 to stop selling gasoline and diesel vehicles. However, Chris Bonelli, global engines spokesman for GM admits, “we have a product plan to support our core internal combustion [engine] programs through 2035, which includes important updates to our current engines and all-new engine designs yet to be announced. We believe we can strive toward the 2035 aspiration, and ultimately an all-electric future, while continuing to innovate and develop our ICE offerings.”
While we are still relying on internal combustion engines, it is good practice to make them even more efficient and lower emissions, even with the prospect of other fuels and technologies competing in the future. To steal a catch phrase made famous by Convergent Science president Kelly Senecal, a leader in internal combustion engine understanding and improvements, when it comes to powertrains, engines, and fuels… the future is Eclectic.
Policy Insider | 10/12/21
Policy Insider | 09/28/21
The new Carbon Reduction Program created in the IIJA, and funded at $6.4 billion over five years, gives states funding to invest in eligible technology and projects including diesel engine retrofits as well as electrification and electric vehicle charging.
Policy Insider | 09/15/21
Having the right tools and technology that are reliable, available, and proven, that can get the job done during adverse conditions, is a core part of readiness and response.