Federal-Mogul upgrades simulation and testing to meet engine downsizing

  • 12-Jul-2013 03:53 EDT
Fede Mog 07-13 Elastothermic_Piston_1.jpg

Federal-Mogul's tests have demonstrated that its Elastothermic piston gallery can reduce crown temperature by as much as 25 K to 30 K.

Extensive simulation and highly focused testing facilities are proving vital to enable Federal-Mogul to successfully keep pace with new demands placed by OEMs on engine components’ suppliers. The multiple needs to downsize, extract more power via turbocharging and more advanced injection strategies, plus the enduring need to reduce emissions levels, are bringing new challenges.

To help meet these, the company has developed a new, highly optimized casting simulation process called Slow-Motion Casting Simulation (SMCS), which provides more precise data to facilitate the material flow, pressure, and filling of piston ring casting molds.

It is part of Federal-Mogul’s Powertrain Segment Division’s drive for enhanced quality and stronger, more wear-resistant piston rings. At its Burscheid, Germany, facility, Dr. Steffen Hoppe, Director of Technology for Rings and Liners, says: “The thermal, mechanical, and tribological demands on components around the combustion chamber—particularly piston rings—increases.” Engine friction could be reduced by using thinner piston rings but that meant a stronger material was vital to achieve required bending strength: “To achieve these requirements, we have developed new materials, casting, and simulation processes.”

To overcome the limitations of the long-established traditional stack molding process, Federal-Mogul has developed a highly automated vertical casting process that uses a special mold design to optimize the design of blanks and gating systems. The result is said by the company to be markedly improved material flow with feeding around the complete circumference of the casting. It is described as “significantly” improving the uniformity of the graphite formation of the gray cast iron.

SMCS includes the use of a high-speed camera to overcome the limitations of regular finite-element (FE) modeling. Hoppe explains that FE simulation creates a particular hurdle: “No matter how fine a network is selected, the ‘macro process’ is still simulated. How close the simulation is to reality always depends on how well the simulation parameters are chosen and set.”

But SMCS is described as overcoming the problem, providing a very detailed analysis of filling the molds, so facilitating more precise optimization of the complex gating and feed systems controlling molten flow.

The use of SMCS allows the flow behavior of the melt at different temperatures and casting speeds to be tracked more effectively, explains Hoppe. This allows a better understanding of and control of pressure fluctuations and the explosive reactions of the casting process.

Federal-Mogul has also developed a more highly refined casting material. The cast steel (GOE70) has a martensitic matrix structure with embedded chromium carbides and a strength of “at least 1800 MPa.” When nitrided, high wear resistance is achieved for particular applications, providing a surface hardness of 1300 HV.

Hoppe believes SMCS will see benefits in both light and commercial vehicle applications.

Testing is also a mainstream discipline at Burscheid. Test House Manager Dr. Armin Robota said there is growing demand from OEMs for the facility to help improve the performance and durability of engines via its expertise involving critical engine components and their development.

This includes bore distortion, wear, oil consumption, and joint sealing, and Robota believes Federal-Mogul is alone in offering bore distortion measurement in the clamped, unclamped, cold, and hot conditions with simulated heat flow: “We have also developed state-of-the-art methods for oil-consumption measurement including gravimetric techniques, and apply online radioactive tracer technology.”

The Burscheid site houses 19 dynamometers, metrology laboratories, and specialist capabilities serving subsystem optimization and the resolution of complex technical issues at product level. Its particular areas of expertise include rings and liners, pistons, rod and crankshaft systems, ignition systems, and the distortion and sealing of block, head, and manifold joints.

Special procedures for cylinder head gasket testing have been developed, including dynamic gas leakage measurement. An in-house development has achieved a method for removing escaped gas from the coolant system and measuring it directly over the course of an engine durability test. Further test work at Burscheid has included what Robota described as an “exhaustive study” that established the relationship between bore distortion and oil consumption for an (unnamed) OEM, involving a three-cylinder gasoline engine using several liner arrangements. And a V6 diesel was tested using advanced slip ring technology to capture data from pressure transducers and temperature sensors rotating with the crankshaft.

With regard to advances in production, Federal-Mogul’s Powertrain Segment has developed a process for cylinder bore manufacturing that combines conventional methods of insert liners with a direct bore coating. Says Hoppe: “Established direct bore coating provides advantages in weight, allows reduced bore spacing, has excellent thermal conductivity, and can provide some friction benefits—but it carries significant challenges in process development, quality, and the required investment.”

The company has developed Sprayfit liners to eliminate these problems. An ultrathin sleeve made of sprayed composite material inserted using a regular press fitting process, it is described by Hoppe as providing greater freedom to develop a liner surface “that is best-in-class for tribology and/or corrosion resistance.”

All this is said to add up to spray parameters that can be optimized without geometric constraints and with “practically no limitations” on liner diameter, length, or wall thickness.

Federal-Mogul plans to formally present Sprayfit at the Frankfurt Motor Show in September.

Also new from the company is a piston developed specifically for downsized turbocharged engines. Called the Elastothermic, it has been designed to provide for increases in power density and compression ratio, without refinement or durability penalties. It uses the company’s Elastoval gasoline piston architecture but with a cooling gallery higher in the crown of the piston.

The Elastothermic piston is said to decrease crown temperature, reduce the risk of knocking in hotter, higher pressure power units, while maintaining high structural strength. The gallery cooled piston (tests have shown crown temperatures down by 25 Kelvin (K) to 30 K) enables downsized engines to run at higher power levels and compression ratios with low NVH but still meet required levels of durability.

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