This application is related to U.S. application Ser. No. 11/486,703 filed on Jul. 14, 2006 by Gabriel L. Johnson and entitled VOLUTE WITH CUT-BACK AT TRANSITION, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to fluid turbines, and more specifically to a fluid turbine case.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A turbine casing, such as that used in a turbo-pump for a rocket engine, includes an axial flow turbine positioned between a tangential flow inlet pipe and a tangential flow outlet pipe. Each of the tangential flow inlet and outlet pipes transitions into a volute to take the tangential flow fluid into an axial flow fluid passing into or discharging from the axial flow turbine. The prior art turbine case includes at least two pieces with the inlet volute being one piece and the outlet volute being the other piece, and the axial flow turbine being positioned between the inlet volute and the outlet volute.
In the prior art two piece volute case, the inlet case and the inlet vanes must be assembled either before or after the exit case with the turbine blades trapped in the middle. In order to remove the turbine blades, the two piece volute case of the prior art must be disassembled.
It is another object of the present invention to provide for a turbine case with an inlet volute and an outlet volute in which the turbine rotor disk and blades can be removed without disassembling the volute case.
A one piece axial flow turbine case with an inlet volute and an outlet volute with an axial flow turbine positioned between the inlet and outlet volutes, in which the turbine vanes and blades can be installed or removed from one side of the case without disassembling the two volutes. The one piece turbine case eliminates the mating flange, the flange seal, and the flange bolts required in the two piece turbine volute case. The one piece flow turbine case reduces the part count, reduces the weight of the turbine, improves the reliability of the turbine, and improved the performance of the turbine. The one piece volute case can be used for an axial or a radial flow turbine.
The annular guide vane assembly with an annular outer shroud having guide vanes extending from the shroud is inserted through an opening of the turbine case. The vane outer shroud extends aft to form an outer shroud for the turbine blades.
The present invention is a axial or radial flow turbine with a tangential inlet and a tangential outlet in which the turbine case 10 is formed of a single piece with an inlet volute and an outlet volute positioned on the sides of the axial flow turbine.
In the present invention, the inlet pipe and volute and the outlet pipe and volute are formed as a single cast piece in order to eliminate the mating flange, the flange seal, and the flange bolts of the prior art turbine case. A contoured tongue or cut-back (not shown) is also used to reduce the rotor side loads.
A cut-back is formed in each of the inlet and the outlet volutes at the transition surface between the pipe and the volute to eliminate the abrupt transition in the volute as described in the pending application Ser. No. 11/486,703 filed on Jul. 14, 2006 by Gabriel L. Johnson and entitled VOLUTE WITH CUT-BACK AT TRANSITION. The cut-back increases the fluid dynamic performance of the volute by reducing the loses in the fluid flow and improves the structural durability of the volute by reducing the stress in the transition, and also simplifies the ability to fabricate the volute by allowing for casting due to eliminating the abrupt transition piece. By eliminating the abrupt transition, the thick to thin material gradient is reduced in the part, and therefore the ability of a liquid metal to pore during casting is improved, resulting in the metal to reach all the desired locations completely. This also allows for the cast part to cool more evenly which reduces the chance of defects in the casting.
In both embodiments (axial flow and the radial flow turbines), the guide vanes can be formed as part of the casing 15 that encloses the turbine rotor disk within the one piece turbine case 10, or can be a separate piece secured to the one piece turbine case 10 and separate from the casing 15. It is preferred that the inlet guide vanes are formed as an integral part of the inlet guide vane casing 15 in order to eliminate any gap between the vanes and the inner or outer shrouds in which the vanes extend between in the flow path through the guide vanes. This integral vane and casing assembly will also add structural strength to the guide vane assembly.
When the guide vane case 15 is secured to the turbine case 10 by the plurality of bolts, an annular slot is formed between the turbine case 10 and the vane guide case 15 in which the turbine rotor disk rotates. The annular slot is sized so that a minimal amount of fluid will leak out from the turbine case. Seals are used to form a seal between the rotating turbine disk and the stationary cases to further reduce the flow leakage.
The US Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. FA9300-04-C-0008 awarded by the United States Army.
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