The engineering of an improved performance PTFE crankshaft (IPPC) seal is a challenge in the pursuit of longer service life and reduced total cost of ownership in the vehicular industry. This paper briefly reviews from the authors’ perspective the evolution of laydown PTFE seal design and details the IPPC seal features along with bench testing performance data.
A new approach has been developed to enhance polytetrafluoroethylene (PTFE) seal performance. To accomplish this, a fundamental need to improve the flexural capabilities of the PTFE seal was required. The new approach involves incorporating elastomeric portions to the seal in regions of the sealing lip that previously have been all PTFE. This new concept PTFE seal has demonstrated improved performance to present day bonded and clamped PTFE seal technologies in three specific areas of bench testing: Dynamic Torque reduction of 45% to 60%, Dynamic Durability life improvement of 1000+ hours at 15% higher geometry, and Thermal cycling performance improvement of 5-30%.
This paper presents the development of surrogate models (metamodels) for evaluating the bearing performance in an internal combustion engine. The metamodels are employed for performing probabilistic analyses for the engine bearings. The metamodels are developed based on results from a simulation solver computed at a limited number of sample points, which sample the design space. An integrated system-level engine simulation model, consisting of a flexible crankshaft dynamics model and a flexible engine block model connected by a detailed hydrodynamic lubrication model, is employed in this paper for generating information necessary to construct the metamodels. An optimal symmetric latin hypercube algorithm is utilized for identifying the sampling points based on the number and the range of the variables that are considered to vary in the design space.
A new concept in thrust washers for gasoline and diesel engines has been developed. Traditionally, thrust washers have been made from the same steel-backed bimetal or trimetal materials that are used for connecting rod bearings and crankshaft main bearings. The new concept is a solid aluminum alloy, specifically formulated for optimum performance as a thrust washer material. This alloy has environmental advantages and performance characteristics superior to currently used materials. The composition, manufacturing process, and microstructure of the new concept thrust washer are briefly explained, and the performance characteristics and environmental advantages are presented.
One of the most successful aluminum-base engine bearing alloys in recent years has been a variation on the SAE 788 alloy that contains 8% tin, 3% silicon and 1.5 to 2% lead. This paper presents two new lead-free aluminum materials derived from this alloy, recently released for general use. These materials are AlSn10Si3 and AlSn6Si4. They have performance characteristics designed for specific applications, the former for lighter loads and higher sliding speeds such as bushings and main bearings, and the latter for higher loaded applications such as rod bearings. Material description and performance data is presented. This paper also presents two additional lead-free alloy developments soon to be released, one alloy designed for even higher loading conditions and one alloy designed for unfavorable geometric conditions such as misalignment.
A fast and accurate journal bearing elastohydrodynamic analysis is presented based on a finite difference formulation. The governing equations for the oil film pressure, stiffness and damping are solved using a finite difference approach. The oil film domain is discretized using a rectangular two-dimensional finite difference mesh. In this new formulation, it is not necessary to generate a global fluidity matrix similar to a finite element based solution. The finite difference equations are solved using a successive over relaxation (SOR) algorithm. The concept of “Influence Zone,” for computing the dynamic characteristics is introduced. The SOR algorithm and the “Influence Zone” concept significantly improve the computational efficiency without loss of accuracy. The new algorithms are validated with numerical results from the literature and their numerical efficiency is demonstrated.
This paper presents the development of surrogate models (metamodels) for evaluating the bearing performance in an internal combustion engine without performing time consuming analyses. The metamodels are developed based on results from actual simulation solvers computed at a limited number of sample points, which sample the design space. A finite difference bearing solver is employed in this paper for generating information necessary to construct the metamodels. An optimal symmetric Latin hypercube algorithm is utilized for identifying the sampling points based on the number and the range of the variables that are considered to vary in the design space. The development of the metamodels is validated by comparing results from the metamodels with results from the actual bearing performance solver over a large number of evaluation points. Once the metamodels are established they are employed for performing probabilistic analyses.
A comprehensive formulation is presented for the dynamics of a rotating flexible crankshaft coupled with the dynamics of an engine block through a finite difference elastohydrodynamic main bearing lubrication algorithm. The coupling is based on detailed equilibrium conditions at the bearings. The component mode synthesis is employed for modeling the crankshaft and block dynamic behavior. A specialized algorithm for coupling the rigid and flexible body dynamics of the crankshaft within the framework of the component mode synthesis has been developed. A finite difference lubrication algorithm is used for computing the oil film elastohydrodynamic characteristics. A computationally accurate and efficient mapping algorithm has been developed for transferring information between a high - density computational grid for the elastohydrodynamic bearing solver and a low - density structural grid utilized in computing the crankshaft and block structural dynamic response.
Gasketed bolted joint analysis tools are gaining importance as the market place demands superior product performance, reduced cycle time, and lower cost. Design analysis tools can be used to predict product performance over the life of the joint. Numerous design concepts under a range of operating conditions can be simulated. The optimal designs can be determined before a prototype is manufactured and tested. The reduction in prototyping and testing results in cost savings and a reduction in design time. The customer is provided with a product with superior sealing performance at a lower cost. This paper presents a design analysis technique which uses a non-linear finite element program in conjunction with a spreadsheet. The spreadsheet functions as a user friendly input and output interface to the finite element program. Parametric models are used to define the geometry of standard sealing system components that include gaskets, flanges, and fasteners.
Heavy duty engine and driveline radial lip seals have numerous applications where severe environmental conditions are known to exist. The most severe conditions are associated with construction, mining, agricultural, military and industrial applications. Under these severe conditions, traditional elastomeric and PTFE dust lips are not capable of providing adequate protection for the oil seal. A new heavy duty excluder sealing system for radial lip seals has been designed and developed as a solution to premature failure due to extreme environmental contamination. Laboratory test equipment, test procedures, and comparative test results, including bench tests and field evaluation are presented as well as some of the design variations required due to various installation schemes.
Bore distortion was measured in a 2.0 liter in-line 4-cylinder gasoline engine, chosen because its siamesed bore design was expected to incur high bore distortion. The method adopted was to install 10 Micro-Epsilon eddy-current transducers in an invar carrier attached to the under crown of the piston. The transducers emerged through apertures in the piston at second ring level where they were in close proximity to the bore surface. A 2-beam linkage system was used to carry miniature co-axial cables to the engine exterior. Measurements were recorded at various speeds and loads up to 6000 rev/min. Maximum bore distortion was 86 microns, arising from clamping loads, thermal effects and combustion pressure. The head bolts spaced around the bore gave rise to fourth order distortion, but the dominant influence was thermal loading which induced second order distortion, attributed directly to the siamesed bore design. The combustion pressure proved to have the least influence.