Power plants – Motive fluid energized by externally applied heat – Power system involving change of state
Reexamination Certificate
1999-07-15
2001-05-22
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Power system involving change of state
C415S170100, C415S202000
Reexamination Certificate
active
06233942
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a closed-loop, vapor cycle, turbine systems that generate rotational power by absorbing energy from a high velocity, vaporized, working fluid.
(2) Description of Related Art
Power generation by vapor cycle turbine engines, using steam or other fluid vapors under pressure, has been a common practice for many decades. Systems having such turbine engines are typically comprised of a vapor generator for vaporizing the working fluid, a turbine, responsive to the vaporized working fluid produced by the vapor generator and producing work, and a condenser for condensing the expanded vaporized working fluid exhausted from the turbine and producing condensate that is returned to the vapor generator by a pump.
The turbines in practical use are typically of the impulse or reaction type and are divided into two broad categories, axial and radial flow. Both axial and radial flow turbines require a high quality, high velocity vapor which is distributed to the blades found in the turbine structure. For these bladed turbines, variations of vapor density result in an unbalanced mass flow passing through the rotating turbine which is undesirable for engine operation.
The drag turbine is a less common category of impulse turbine of which there are two general variations. In the first, high velocity vapor is directed, by a nozzle, to flow radially from the outer edge of a series of uniformly spaced, smooth disks compelling them to rotate about a central axis through the action of viscous drag. In a second variation, high velocity vapor is directed, by a nozzle, to flow tangentially against the smooth outer or inner surface of a cylindrical structure compelling it to rotate about a central axis, again, through the action of viscous drag. Both types of drag turbine do not require uniformly distributed flow and are highly tolerant of low quality vapor.
For bladed turbines, variations of vapor density result in an unbalanced mass flow which creates vibration that can lead to catastrophic failure of the turbine and its associated support structure. The variations of vapor density are attributable to variations in vapor quality localized within the vapor flow. Liquid droplets contained within a low quality vapor cause surface erosion of the delicate turbine blades. The erosion shortens the useful life of the blades and results in the turbine becoming statically unbalanced. Therefore, to achieve maximum life from a bladed turbine, the working fluid vapor entering and exiting the turbine must be in a high quality, non-condensing state. In a conventional closed loop power cycle, a condenser must be used to eject the latent heat of vaporization from the working fluid, returning the fluid to the liquid state for reuse in the cycle.
For a closed loop power system employing a bladed turbine, the necessity of a high quality vapor requires that the condenser eject a larger amount of waste heat from the vapor than would be required if the turbine could tolerate a low quality, condensing vapor flow. The requirement of the condenser to eject this larger amount of waste heat, results in a reduction of the overall thermal efficiency of the engine. Furthermore, the physical size and weight of the condenser, along with its associated pumps and plumbing, is a major impediment to the use of the closed loop power system in automotive and aerospace applications. Size, weight and overall thermal efficiency are principal design considerations in power systems developed for these applications.
Therefore, what is needed, and what the present invention provides, is a means such that the working fluid exiting the turbine is in the fully condensed liquid state. Employing such means returns the working fluid vapor to the liquid state within the turbine and entirely eliminates the need for a heat exchange condenser, and its associated pumps and plumbing.
Accordingly, the inventive turbine is able to tolerate a fully condensing working fluid flow while providing a unique mechanism, for returning the working fluid to the vapor generator without the need of a condenser or additional pumps.
BRIEF SUMMARY OF THE INVENTION
The practical application of the closed-loop vapor cycle turbine engine to automotive and aerospace use has long been excluded from consideration due to the inability to package the power plant in a compact form. A principle limiting element to achieving a compact form is the requirement for a condenser. For many vapor cycle power systems in common use, the condenser has a physical size greater than the balance of the whole system. What is needed, and what the present invention provides, is a turbine to smoothly transform the kinetic energy of fully condensing working fluid vapors into rotary power while concurrently acting as a positive displacement pump for returning the working fluid, in the liquid state and under high pressure, to the vapor generator.
In the present invention, a fully condensing working fluid vapor is directed by a nozzle along the inner surface of a cylinder that is free to rotate about its central axis. The working fluid, upon contact with the surface of the cylinder, imparts its kinetic energy to the cylinder through the mechanism of viscous drag and, under the influence of centrifugal force, readily returns to the liquid state.
The outer surface of the cylinder is provided with one or more vane-type seals in contact with an outer housing that encompasses the inventive turbine. The outer housing is provided with one or more stationary vane-type seals acting upon the outer surface of the cylinder. These seals form, in combination, the pumping cavities of a positive displacement rotary vane pump. The necessary flow passages to and from the created pumping cavities are also provided.
This unique combination of an impulse drag turbine and a positive displacement pump, exemplified by the present invention, allow the closed-loop vapor cycle turbine engine to become very compact and, thus, practical for automotive and aerospace use. Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
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Holme Roberts & Owen LLP
Nguyen Hoang
Thermaldyne LLC
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