A novel two-dimensional ultrasonic analysis system is being used in order to produce high performance pistons that enable another further substantial step in diesel engine downsizing.
In its first application, the hugely improved cooling capacity of Federal-Mogul’s “raised gallery” piston allows a customer to introduce a series of measures that achieves a CO2 reduction of up to a third compared with the previous generation engine without raised gallery pistons.
The first production application of the company’s raised gallery piston also gives a specific power increase of a quarter keeping the piston at temperatures much than lower than the limit of 400 degrees Celsius.
In the same circumstances, a standard piston’s bowl rim stresses are just over a third higher and its temperatures reaches 440 degrees Celsius, nearing the metal’s melting point.
Gian Maria Olivetti, the vice president for technology and innovation, Powertrain Energy, for Federal-Mogul, said: “Diesel downsizing increases specific power output in order to improve fuel economy and CO2 emissions and also increases the thermal and mechanical loads that diesel pistons must withstand.
“With the development of new highly-loaded engines, the risk of piston failure has increased substantially as past improvements in materials, design and cooling concepts have reached their physical limits. Federal-Mogul’s innovation in advanced testing techniques, materials science and manufacturing processes greatly reduces the limitations placed on diesel downsizing strategies”.
Modern diesel pistons have a cooling gallery which helps oil flow continuously. The position and design of the gallery have a huge impact on the component’s operating temperature and durability.
The closer the gallery is to the piston bowl, the more heat that can be removed letting engine manufacturers increase the combustion temperature and pressures to improve fuel economy and CO2 emissions.
The standard, one-dimensional ultrasonic testing method can identify defects but cannot quantify the size or position.
However, the Federal-Mogul’s 2D ultrasonic process provides 125,000 data points in thirty seconds. This technique enables the company’s engineers to correctly determine the size and position of defects, providing valuable data for casting process development.
Dr. Frank T.H. Doernenburg, the company’s director of technology, pistons and pins, said: “In the past, it was very difficult to cast gallery pistons with such precise control of the size and location of the cooling gallery. Federal-Mogul’s new 2D ultrasonic test has removed that barrier.
“Our process is non-destructive, completely controls casting process quality and aids advanced casting process development, giving engine designers substantially more freedom to increase engine efficiency”.
The company validated its 2D ultrasonic technology by dissecting and sampling hundreds of pistons, correlating the ultrasonic images against destructive testing methods.
The research concluded in the development of software tools as well as a number of key physical parametres such as probe geometry, wave length, beam geometry and focus.
The piston design and subsequent piston performance can be increased significantly through Federal-Mogul’s 2D ultrasonic testing and analysis process, which is quickly becoming an enabling technology for more efficient powertrains.
This breakthrough in inspection technology was developed at the company’s Nuremberg technical centre in Germany and was recently awarded a 2012 Automotive News PACE Award.
