As part of its effort to reduce greenhouse gas emissions and improve fuel economy for model years 2017 through 2025 light-duty vehicles, the U.S. Environmental Protection Agency (EPA) has begun developing an advanced test engine to demonstrate fuel-saving and emissions-reducing technologies. The test engine is intended to help establish the feasibility of meeting fuel standards through improvements to combustion chamber geometries, fuel injection strategies, fuel composition, valve timing, and intake conditions.
In development of the engine, the EPA is using ANSYS FORTÉ CFD software, giving its engineers the ability to quickly and inexpensively make multiple design iterations. ANSYS acquired FORTÉ as part of its acquisition of Reaction Design earlier this year.
“For the first time, [EPA] is using simulation to help them zero in, reduce the number of iterations they do in prototype engine form so that they can meet that target demonstration date in the midpoint of that time period,” said Bernie Rosenthal, General Manager, Reaction Design, ANSYS. “They went through a pretty exhaustive overview of the different computational fluid dynamics codes available for simulating things like particulate formation inside of the engine and determined that it could best do its work using ANSYS FORTÉ.”
Combined with the previous EPA and National Highway Traffic Safety Administration (NHTSA) standards, the new program is projected to result in model year 2025 vehicles emitting one-half of the greenhouse gas emissions from the 2010 model year.
“The goal of our Clean Automotive Technology program is to research, evaluate, and develop advanced engine and drivetrain technologies that help increase fuel efficiency, reduce regulated criteria emissions such as nitrogen oxides and particulate matter, and cut greenhouse gas emissions,” said Matthew Spears, Heavy-Duty Onroad and Nonroad Center Director of EPA’s Office of Transportation and Air Quality. “To accomplish this, we needed to understand how changes in engine design and hardware can impact the engine combustion processes.”
The FORTÉ CFD package is the result of 30-plus years of investigation, both by Reaction Design and Sandia National Laboratories, as well as the Model Fuels Consortium (MFC), an effort led by Reaction Design from 2005 to 2012 that involved 20 automotive and fuel manufacturers seeking to develop accurate fuel models for use in combustion simulation.
“If you were trying to do this 30 years ago, you’d have an idea of maybe if I change the bowl shape in this way the mixing will be better and therefore I will burn more of that mixture each time that cycle happens and therefore create less pollutants. The only way to really prove that hypothesis was to actually go cut metal and take a bunch of time and money to put together a real engine prototype,” Rosenthal said. “What we allow people to do now 30 years later is look at some of those effects and get a very good understanding of what, if not the exact result of those changes, then certainly the trend that they will expect from making certain changes. If I change a bowl shape, I can look at the effect within a few hours on my missions profile. If I change when I inject, I can see that within a few hours and see if that makes a difference on how much pollutant I generate during that cycle. It’s really a way that you can do much more exploration of a design without having to spend the money to build it.”
In addition to gaining a better understanding of combustion dynamics through CFD modeling, the EPA intends to use ANSYS’ detailed soot modeling capabilities to more accurately predict soot mass and particle size distribution, important metrics in the standards.
“Over the past couple of years there’s been increasing science that shows that the smaller particles that get emitted may be the cause of a lot of the things that we now put under the umbrella of COPD [Chronic Obstructive Pulmonary Disease]. Anything from asthma to lung cancer to a whole bunch of ailments in between may be caused by these smaller particles,” Rosenthal said. “It’s very difficult and challenging for automakers to really figure out how they can manage particles that are nanometer-size particles. It’s really been the challenge of both the regulatory agency and the automakers of how do we address this because it is a public health issue.”