Sealing of a rotor and a stationary sideplate..
Sealing of a rotor and a stationary sideplate..
(OP)
All,
I've been discussing this under the "Mechanical Engineering - Other Topics" but now that I think I have a solution, I thought I'd post it here to see if anyone has any comments or concerns.
I'm building an engine with a rotor of 3.220" radius spinning at 2,626 RPM between stationary side plates. I feed oil into the rotor near its center then route it around cylinders (for cooling), tap off a few points for spot lubrication, feed it through radiators in the rotor periphery (cooling air originating in the blades of a centrifugal fan incorporated into the rotor) then pass the cooled oil to the side plates where it is filtered and routed back into the center of the rotor. The oil flow rate is high, but the pressure is moderate. I have several passages between the side plates and rotor (air in, oil in, oil out, fuel in) crammed into the 3.220" radius, so radial size of the solution is critical. Axial depth of the solution is less critical.
My initial solution was to use simple O-rings. The radial size of the solution is small, but I was unable to find any that were compatible with hot oil and the high surface speeds at the periphery of the rotor where at least one passage is required (oil return). I was unable to find any other seal that met my needs.
The solution below is simple and low cost yet appears to meet all requirements while consuming less space than the O-ring solution.
In this approach, standard seals which are normal stationary and sealing a rotating shaft are instead rotating around stationary circular manifolds extending into the rotor from the stationary side plate. I don't believe the approach violates any of the functional requirements or capabilities of the seals. Though I flip one seal relative to the other, I see no mention of sensitivity to rotation direction in the selected seal's literature.
The center illustration shows the preferred arrangement in which the side plate manifold is most rigid, identical seals are used, and the rotor cavity is simple. This configuration, however, requires additional radial space to route oil between the seals. The arrangement shown in the rightmost illustration is less desirable due to lower rigidity, use of different seals, and complexity of the rotor cavities, but it incorporates space for axial routing of fluid between the seals and is thus the preferred for the outermost oil return seal.
The seals are from Parker's Flexicase CFN Series. The seals are a nice fit to my needs because they're fast (6,000 fpm), operate at high temperature in the presence of oil (up to 600F), and have a small profile (0.250 high x 0.175 wide). The largest risk in this approach is the requirement for 0.005 dynamic run-out on the "shaft." To mitigate this risk, I will switch from the 6202 main bearing in the rotor to a Super-Precision 7202 Bearing and match-bore (stack and clamp the parts then bore all together) the central axis of the rotor and side plates. Another risk is in my interpretation of their specifications in terms of profile height and width and my assumption I can get these seals in any arbitrary bore and shaft diameter insofar as they're under 6.00 diameter and comply with the 0.250 cross-section limit. To address this risk, I'm contacting my local distributor to find out what parts are actually available for folks like me who need only a handful.
Does anyone see any issues with this approach that I've missed?
Thanks for your help!
Rod
I've been discussing this under the "Mechanical Engineering - Other Topics" but now that I think I have a solution, I thought I'd post it here to see if anyone has any comments or concerns.
I'm building an engine with a rotor of 3.220" radius spinning at 2,626 RPM between stationary side plates. I feed oil into the rotor near its center then route it around cylinders (for cooling), tap off a few points for spot lubrication, feed it through radiators in the rotor periphery (cooling air originating in the blades of a centrifugal fan incorporated into the rotor) then pass the cooled oil to the side plates where it is filtered and routed back into the center of the rotor. The oil flow rate is high, but the pressure is moderate. I have several passages between the side plates and rotor (air in, oil in, oil out, fuel in) crammed into the 3.220" radius, so radial size of the solution is critical. Axial depth of the solution is less critical.
My initial solution was to use simple O-rings. The radial size of the solution is small, but I was unable to find any that were compatible with hot oil and the high surface speeds at the periphery of the rotor where at least one passage is required (oil return). I was unable to find any other seal that met my needs.
The solution below is simple and low cost yet appears to meet all requirements while consuming less space than the O-ring solution.
In this approach, standard seals which are normal stationary and sealing a rotating shaft are instead rotating around stationary circular manifolds extending into the rotor from the stationary side plate. I don't believe the approach violates any of the functional requirements or capabilities of the seals. Though I flip one seal relative to the other, I see no mention of sensitivity to rotation direction in the selected seal's literature.
The center illustration shows the preferred arrangement in which the side plate manifold is most rigid, identical seals are used, and the rotor cavity is simple. This configuration, however, requires additional radial space to route oil between the seals. The arrangement shown in the rightmost illustration is less desirable due to lower rigidity, use of different seals, and complexity of the rotor cavities, but it incorporates space for axial routing of fluid between the seals and is thus the preferred for the outermost oil return seal.
The seals are from Parker's Flexicase CFN Series. The seals are a nice fit to my needs because they're fast (6,000 fpm), operate at high temperature in the presence of oil (up to 600F), and have a small profile (0.250 high x 0.175 wide). The largest risk in this approach is the requirement for 0.005 dynamic run-out on the "shaft." To mitigate this risk, I will switch from the 6202 main bearing in the rotor to a Super-Precision 7202 Bearing and match-bore (stack and clamp the parts then bore all together) the central axis of the rotor and side plates. Another risk is in my interpretation of their specifications in terms of profile height and width and my assumption I can get these seals in any arbitrary bore and shaft diameter insofar as they're under 6.00 diameter and comply with the 0.250 cross-section limit. To address this risk, I'm contacting my local distributor to find out what parts are actually available for folks like me who need only a handful.
Does anyone see any issues with this approach that I've missed?
Thanks for your help!
Rod
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