Heavy-duty engine design
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CFD simulation results of coolant-flow field for cylinder head and block. (FPT Industrial)

Insights into heavy-duty engine design

What significant factors are influencing engine developers approaching design cycles? Two experts provide insights from recent programs.

Engine developers face numerous challenges in their work. When building the new clean-sheet design C3.6 engine, Caterpillar Industrial Power Systems considered several factors including customer feedback and lower owning and operating costs. The result of this development process is a compact 134-hp (100-kW) engine that provides a 5% increase in power density and 12% increase in torque compared to its predecessor engine, the C3.4B.

Introduced at a Caterpillar press event in late October in Clayton, North Carolina, the new diesel engine is dual-certified to EU Stage V/U.S. EPA Tier 4 Final nonroad emission standards and generates 406 lb-ft (550 Nm) of torque at 1500 rpm. The company says the new engine’s smaller package features flexible aftertreatment solutions including engine-mounted options that provide OEMs with simplified installation and reduced integration costs.

“Technology features such as electronically controlled turbocharging have made it possible to create a smaller engine with the response that would be expected from a much larger product,” said Alex Eden, Caterpillar product marketing manager. “The torque at low speed, which is critical for machine drivability, is particularly impressive.”

When considering significant and potentially disruptive factors that will influence engine developers as they move into the future, Eden, who is also a chartered engineer, said he considers three main things: machine ownership patterns, political forces (social pressures and regulations), and hybridization/electrification across power nodes and applications.

“Those that used to be owner-operator might go more rental. Larger fleets might also go rental. That’s getting quite big right now,” Eden told Truck & Off-Highway Engineering. “But then what will happen after rental…How are people going to buy machines? Are they going to lease them? How does that interaction work between Caterpillar dealers selling the engines to third-party OEM customers, and then the OEM selling the machine to the end customer? That’s kind of a ‘who knows’ at the moment.”

When designing an engine, diesel engine manufacturers like Cat Industrial Power are bound by government regulations, which have been fairly stable in recent years with Stage V and Tier 4 Final in place. “We don’t necessarily know how those political forces are going to change,” said Eden.

New emissions regulations for CO2 reduction and air quality improvement will drive technical solutions, as well as the increase of zero-emission zones for urban areas, which will boost the development of alternative propulsion, said Pierpaolo Biffali, VP of product engineering at FPT Industrial. Despite an eventual shift to alternative propulsion, he believes that combustion and aftertreatment advances can satisfy global pressure for reduced diesel emissions in the coming years.

“Though the industry is walking towards a zero-emission future, for the mid-term, clean diesel and natural gas engines do represent the concrete solution for CO2 reduction at a lifecycle level,” Biffali told TOHE. “For many years, batteries will be zero CO2 emissions only on-board, since energy production will remain predominantly oil and coal-based.”

Hybridization and electrification will be disruptors influencing engine design at certain power nodes, but they likely won’t happen across the board, all at the same time. “At first, we will use powertrain electrification as a key enabler to enhance ICE performance and fuel economy,” said Biffali. Eden agrees: “We have to consider that back to the machine. We ship parts to our OEM customers and they still are spending a lot of time integrating the last set of emissions regulations into their machines.”

Quieter designs
Noise, vibration and harshness (NVH) is a definite concern for near-term engine design. Noise restrictions in urban areas and for overnight operations are a major driver, as too is the perception of engine quality that tends to increase as the noise from a power source decreases. “If you stand near an engine that rattles or it doesn’t have a nice quality of sound to it, you subconsciously think that that engine is not very well put together. It’s not very well designed. It won’t have good quality and durability,” Eden said. “We work really hard on making sure that the NVH of our engine is as good as it can possibly be.”

The NVH of the engine also affects the in-cab environment and operator comfort. A quieter engine can help to reduce operator fatigue and therefore boost productivity throughout their shift. In agricultural application such as in tractors, quieter engines and machines can even make it less stressful for and easier to maneuver around the livestock, Eden noted. With Cat’s new C3.6 diesel engine, four key elements were redesigned extensively to make the noise as low as possible: stiffened block, advanced composite oil pan (formerly aluminum), composite material for top cover, and gear train moved from the front to rear.

The oil pan often is where quite a bit of radiated noise comes from, according to Eden. By using composite materials and the structure of the oil pan itself, the radiated noise is dramatically reduced from this source. “Those are the physical things that we’ve done on the engine to reduce the noise. And then Caterpillar also did work on the combustion noise. The 3.6 is three decibels quieter than the previous-generation engine, in terms of sound power it’s reduced 50%,” he shared.

FPT’s Biffali also stresses that NVH is “a concern of increasing importance” for all engine designs, noting that the company’s approach consists of further qualifying the sound of engines. “For this reason, we have started an innovative partnership with the Oscar-winning artist Giorgio Moroder,” he said. Details on this project are expected in the next few months.

The digital world
Simulation and digital tools have become a staple in engine developers’ toolboxes. A comprehensive portfolio of simulation tools is available to FPT Industrial engineers, according to Biffali, to cover analysis at different levels of detail: from complete powertrain simulation for the definition of the optimal architecture, to system level for requirements definition, down to component level for single part optimization.

“The capability of virtual analysis has a direct impact on product time to market, contributing to a full understanding of physical phenomena,” Biffali said. “Virtual validation has been at the core of our development processes for many years, enabling us to test components to the limit, to expose virtual models to extreme missions to see how they react, and to benchmark different solutions, even the ones that don’t exist yet.”

Augmented reality also is being employed at FPT Industrial to enhance engine-development capabilities in a more challenging environment that requires engineers to collect and process multiple real-time inputs. “So, we started using augmented reality to combine the virtual powertrain system not only with the vehicle, but also with its operating scenario to enhance power unit control by anticipating vehicle dynamics rather than reacting to situations,” Biffali said.

Caterpillar also uses simulation in all aspects of engine development. Eden explained that the thermal fluids department, for example, simulates the flow from the intake all the way through to the exhaust. They model the entire process virtually and use that to help its rate, speed up the development process, and reduce development costs because not as much testing needs to be conducted.

“They model all of the combustion processes, the fuel sprays, we ensure as clean as combustion as possible and to maximize power from the engine,” he said. “They then create bespoke simulation tools to look at aftertreatment systems…to make sure we’ve got the most amount of knowledge as we possibly can as we go into each phase of prototyping, piloting, and then into production.”

Occasionally something in the physical world does not come through the same as in the virtual world. In that case, the change will go around that loop again, Eden explained. “We do that loop through our prototype phase and then we do it through our pilot phase so that when we get to the product it’s been validated, so it’s perfect for the customer and ready to go,” he said. “We really do put an awful lot into our engineering development through the use of simulation. It’s simulate first, test second.”

3D printing and beyond
Caterpillar has a center of excellence for 3D printing in the U.S. and 3D printers on-site in Peterborough, U.K., where the C3.6 is built. Engine developers actually 3D-printed an entire C3.6 engine in parts from an early prototype to look at how an engine would fit to test cells to reduce development time while waiting for the actual components to arrive from the suppliers. “We assembled the parts together and then trial-rigged the entire engine into the test cell so that when we have the real engine ready to go, everything fitted perfectly and off you go,” Eden said. “We saved huge amounts of time doing that.”

Looking three to five years down the road, a greater understanding of advanced materials and their increased use will play a key role in next-generation engine designs, according to Eden. “Improvements in materials will lead to improvements in engine performance, usually power density, and cost of ownership,” he said, adding that fuel systems also can become more robust with better filtration. “There’s always improvement that we can get out of air systems so we can have better response. Again, back to power density.”

Software integration and controls offer challenges and opportunities for improvement as well, similar to what the automotive industry has experienced with the electronic engine and software controls. “The main message for emergent technology trends is that we want physically smaller engines and physically smaller aftertreatments but with more power,” Eden said. “So, each of those component subsystems have to be better than they were before, lighter than they were before, and give us more performance. And we’ve got to design and integrate them all together with finer tolerances, with less risk to ensure improved reliability and durability every time.”

New combustion concepts and controls also can significantly enhance the efficiency of natural gas engines, noted FPT’s Biffali. He referenced an announcement made at the company’s Capital Markets Day in September that FPT Industrial is working on a disruptive technology capable of repositioning the ICE as the ultimate solution for CO2 reduction for the next decade. More details about this “exciting development” are coming shortly, he added. Stay tuned.

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