Modeling and simulation continue to help suppliers and OEMs provide systems and vehicles that do more work while conserving fuel, reducing emissions and keeping costs in check. A broad range of tools come into play as engines and aftertreatment systems move through the design cycle.
Tighter regulations are forcing equipment makers to turn to smaller engines and system architectures that maximize efficiency by ensuring that all systems work together at optimal levels. New engines can increase lifetimes while lowering operating costs. In the past, these power plants ran at lighter loads to improve durability. Today’s engines match or exceed the output of their predecessors in smaller form factors.
“The latest modeling techniques enable us to predict with accuracy the hot spots in an engine design that might lead to failure, and then take corrective action,” said Oliver Lythgoe, Product Concept Marketing Manager at Perkins. “This enables us to get more power and torque from smaller engines—and smaller engines help OEMs deliver machines that are lighter, have better turning circles and better operator sight lines.”
All systems on a vehicle are now being designed to continuously interact, which often helps developers improve overall vehicle efficiency. This focus on holistic designs means OEMs and suppliers now work more closely together than in the past.
Simulations of engines are often shared with OEMs, who have broader insight into tight engine compartments that can make cooling difficult. OEMs are also responsible for reducing noise, which is regulated in many regions. Computational fluid dynamics (CFD) is a common tool for understanding cooling and noise movement.
“3D CFD simulation helps engineers understand the under-hood thermal flow field to identify regions of hot air recirculation and flow stagnation,” said Shelley Knust, Executive Director, Engine Business Unit Off-Highway Engineering at Cummins. “Once under-hood thermal management needs are met, we focus on addressing mitigation of any noise issues. Modeling and simulation with OEMs early in the design stage enables both Cummins and OEMs to reduce the number of physical prototypes and subsequent testing to validate while achieving an optimal design.”
Eliminating prototypes and testing steps saves time and money. A range of different products and analytical processes are needed to explore the countless variations that occur as combustion and emissions are studied and tweaked. Advanced design tools let developers change parameters and components in different areas of engines and aftertreatment systems, letting them enhance overall performance and efficiency.
“Running ECU models and high fidelity plant models together in a co-simulation platform allows John Deere to conduct extensive Monte Carlo variation analysis and helps us better understand population distributions with regard to engine performance and tail pipe emissions,” said Jason Schneider, manager of product engineering at John Deere Power Systems. “This, in turn, enables us to develop an optimal calibration and control strategy.”
Underscoring the need for a holistic approach, the nuances of aftertreatment systems can impact fuel consumption. Designing engines and aftertreatment systems together can bring significant size and cost benefits.
“With careful consideration of the performance trade-offs, integrated or combined catalyst designs can reduce the number or volume of catalysts in the system,” said Schneider. “We have used passive regeneration to the greatest extent possible to allow for in-cylinder injection of hydrocarbons on some platforms, allowing elimination of hydrocarbon injection equipment in the exhaust system.”
Design software is also helping engineers shrink the size of aftertreatment systems. Adjusting a vent or pipe can give a vehicle an edge in this critical aspect of ongoing operating costs.
“Doing predictive modeling using computational fluid dynamics helps to design something with good flow and few restrictions,” said Dave Rodgers, Engines Business Unit Director at Ricardo. “Getting uniform flow across the selective catalytic reduction improves efficiency. If backpressure increases, the cost is paid in fuel economy.”
Flow is as critical inside engines as it is in aftertreatment systems. As design tools provide more insight into how gases and liquids move through engines, engineers can more easily pick the correct component. That brings many benefits such as reducing component costs by establishing closer margins.
“CFD modeling is employed at both the component and the engine system and machine supersystem levels to explore system architecture trade-offs,” Knust said. “We utilize 3D and 1D modeling early on in the system design, currently focusing on flow and pressure drop. 3D modeling also helps us predict localized temperatures in components so we can identify and optimize the design before procuring hardware.”