Maha research center leads in pump and motor modeling
Purdue University, a member of the Center for Compact and Efficient Fluid Power, has been tasked with developing a fuel and power efficient excavator, the largest of the CCEFP’s test beds, as well as the virtual prototyping of pumps and motors. Run by mainly graduate-level students, the university’s Maha Fluid Power Research Center also carries out work on hydraulic hybrid transmission technology.
The pride and joy of Maha’s fluid power research, however, is its pump and motor modeling software for piston-powered pumps. This software has been developed to predict the conditions and the load carrying ability of the flow through sealing and bearing gaps while considering non-isothermal gap flow, micro-motion of parts, and fluid-structure interaction. What makes the software stand out is that it is based on capturing fluid structure interaction for all three lubricating intakes of axial piston pumps and motors.
The physical behavior in those interfaces is very complex and requires the combined solution of different domains (fluid mechanics, continuum mechanics and thermodynamics problem) where the time scale between those domains is also very different. Because the interface is so complex Maha had to develop its own integrated FEM solver in order to handle the complex fluid structure interaction problem of those tribological interfaces of pumps and motors.
“There is no other group in the world that has software like this,” Dr. Monika Ivantysynova, director of the Maha Fluid Power Research Center, said. “The consideration of surface deformation due to thermal loading is a very recent accomplishment by my team and we had our first papers published last year.”
Unlike the hydraulic hybrid research going on at UMN, the research conducted at Maha is not affiliated with the CCEFP. Maha worked closely with Parker Hannifin Corp. to develop a hydraulic hybrid system for special truck applications like medium duty delivery trucks. The transmission is based on an output coupled power split hybrid transmission structure. In this structure, the planetary gear sits at the engine and a pump/motor at the output shaft.
“We have also proposed a hydraulic hybrid transmission based on the output coupled structure for the Toyota Prius,” Ivantysynova said. “We have a version tested on our hydraulic dynamometer test rig.”
The excavator test bed was designed to demonstrate the significant improvement in the efficiency of the hydraulic systems of heavy mobile machines that could be achieved by integrating advanced system and component designs. One of these advanced systems is displacement-controlled actuation. The challenge was to demonstrate that pump control could compete with traditional valve controlled systems in the areas of bandwidth and accuracy. A 40% fuel savings over a traditional machine was demonstrated when a four-pump DC system with multiple switching valves was implemented on the eight-actuator mini-excavator test bed.