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The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. A model of the oil seals is developed to calculate internal oil consumption (oil leakage from the crankcase through the oil seals) as a function of engine geometry and operating conditions. The deformation of the oil seals trying to conform to housing distortion is calculated to balance spring force, O-ring and groove friction, and asperity contact and hydrodynamic pressure at the interface. A control volume approach is used to track the oil over a cycle on the seals, the rotor and the housing as the seals are moving following the eccentric rotation of the rotor. The dominant cause of internal oil consumption is the non-conformability of the oil seals to the housing distortion generating net outward scraping, particularly next to the intake and exhaust port where the housing distortion valleys are deep and narrow.

The rotary engine provides high power density compared to piston engine, but one of its downside is higher oil consumption. In order to better understand oil transport, a laser induced fluorescence technique is used to visualize oil motion on the side of the rotor during engine operation. Oil transport from both metered oil and internal oil is observed. Starting from inside, oil accumulates in the rotor land during inward motion of the rotor created by its eccentric motion. Oil seals are then scraping the oil outward due to seal-housing clearance asymmetry between inward and outward motion. Cut-off seal does not provide an additional barrier to internal oil consumption. Internal oil then mixes with metered oil brought to the side of the rotor by gas leakage. Oil is finally pushed outward by centrifugal force, passes the side seals, and is thrown off in the combustion chamber.

FEPM alternating dipolymers of tetrafluoroethylene (TFE) and propylene (P) are well known to exhibit distinguished chemical resistance, especially against various organic and inorganic bases, compared to conventional fluoroelastomers (FKM): e.g., copolymers of vinylidene fluoride (VdF), hexafluoropropylene (HFP), and optionally incorporated tetrafluoroethylene (TFE). These unique characteristics have been finding automotive sealing applications where lubricants formulated with considerable quantity of additives are used. FEPM dipolymers, however, have difficulty in processing - particularly in mold release. There are TFE-P-VdF terpolymers available, which are improved in mold release. TFE-P-VdF terpolymers, however, are often pointed out that the base resistance is lost to some extent, because the minimum quantity of VdF necessary to establish a practical cure speed and physical properties is not very low.

There are many kinds of lubricants such as automatic transmission fluid, brake fluid, bearing grease, etc. used in automotive vehicles. Fluoroelastomers have been used for a long time for oil seals contacting such lubricants. Fluoroelastomers composed of vinylidene fluoride, hexafluoropropylene, and optionally incorporated tetrafluoroethylene are designated as FKM, which have been one of the most popular fluoroelastomers. The latest automotive lubricants tend to contain a large amount of additives to improve the performance along with the demanding driving conditions. Such additives, however, are reactive with FKM at elevated temperatures to raise the hardness of FKM, which results in losing the sealing performance. An elastomer material which does not lose the flexibility in the long-term exposure to the lubricant has been desired.

New material and processing technologies were developed for main components of the rotary engine to establish its reliability and durability. The components discussed in this paper are the rotor housing, side housing, and sealing elements. Also described are the material and processing technologies which resolved problems about their strength, rigidity, wear, etc.

The Wankel rotary engine is more compact than conventional piston engines, but its oil and fuel consumption must be reduced to satisfy emission standards and customer expectations. A key step toward this goal is to develop a better understanding of the apex seal lubrication to reduce oil injection while reducing friction and maintaining adequate wear. This paper presents an apex seal dynamics model capable of estimating relative wear and predicting friction, by modeling the gas and oil flows at the seal interfaces with the rotor housing and groove flanks. Model predictions show that a thin oil film can reduce wear and friction, but to a limited extent as the apex seal running face profile is sharp due to the engine kinematics.