Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
2001-06-18
2002-04-30
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S727000, C060S039780, C029S889200, C415S198100
Reexamination Certificate
active
06378287
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention is directed to turbo-machines and, more particularly, to multistage axial or radial gas flow compressors and turbines and systems employing such turbo-machines.
It is known that the efficiency of turbo-machines, such as compressors and gas turbines, may be substantially improved by operation in a manner which approaches isothermal conditions. This essentially means that the temperature of the gas as it moves between successive stages of the turbo-machine is adjusted so that the inlet temperature of the gas at each successive stage is maintained at about the same temperature as at the inlet of the preceding stage. This is in contrast to adiabatic operation in which the temperature of the gas changes between the successive stages due to the compression or expansion of the gas as it moves through each successive stage of the turbo-machine.
Maintenance of a constant temperature at the inlet of each successive stage may be accomplished in several different ways. In a purely isothermal gas turbine, fuel injectors and temperature sensors may be positioned in each stage so that the correct amount of fuel is injected into and burned in each stage as is needed to ensure that the temperature of the gas in the gas turbine is re-elevated to substantially the temperature at which it entered that stage prior to discharge from the stage and introduction to the next succeeding stage. This is shown for example in U.S. Pat. No. 4,197,700 (Jahnig). In a purely isothermal compressor, a coolant may be introduced into each stage, for example through the stator blades of an axial compressor, to reduce the temperature of the gas to substantially the same temperature at which it was introduced to that stage to ensure that the temperature of the gas which is discharged from the stage and introduced to the next stage is at substantially the same temperature. Combustion chambers or intercoolers have also been employed between stages to add or remove heat and alter the gas temperature so that the gas entering each of the respective stages is at substantially the same temperature.
Substantial improvements in efficiency may also be achieved in particular in compressors through the use of relatively low temperature coolants, such as sea water which is taken from below the thermocline. Such sea water will typically be about 40° F. which is sufficient to maintain a temperature of about 45° F. to the intake of each stage of an isothermal compressor.
It would also be desirable to design, for example, the first stage of the turbo-machine to achieve the maximum efficiency from a design standpoint when the turbo-machine is in normal operation. Normal operation means that each stage would have a given shaft speed, pressure ratio, temperature ratio, gas density ratio, and the type of operation in each stage would be the same, e.g. isothermal, adiabatic, etc. This optimum efficiency stage could then act as a master stage which would serve as a model for the construction of each of the subsequent stages. In the present invention a formula has been discovered for the sizing of each subsequent stage once an optimum efficiency master stage has been designed which will maximize the optimum efficiency of each subsequent stage so that it has substantially the same optimum efficiency as the optimum efficiency master stage.
It has also been discovered that the sizing formula of the present invention is applicable to all turbo-machines whether they are purely isothermal in operation, purely adiabatic in operation, or a combination of adiabatic/isothermal operation as in turbo-machines employing intercoolers or intercombustion chambers between stages to adjust the temperature of the gas to a given selected temperature prior to introduction of the gas to the next successive stage. And, it has been discovered that the sizing formula of the present invention is also equally applicable to either axial flow or radial flow turbo-machines, and to a wide range of types of turbo-machines including compressors, gas turbines and gas expanders. Significantly, the sizing formula of the present invention may be utilized in the sizing of the turbo-machine stages whether or not a tributary gas flow is introduced to or removed from one or more of the stages. Such tributary flow may be introduced for example to each stage in the form of fuel to provide for isothermal operation.
Gas expanders are quite similar in construction to gas turbines, but each has a somewhat different emphasis and purpose. In both gas turbines and gas expanders the gas expands as it moves through the several successive stages. However, gas turbines generally have the purpose of generating drive shaft power, for example to power an electrical generator, whereas gas expanders have the principal function of permitting a controlled expansion of gases for the purpose of cooling the gas. Because of the similarity of construction of gas turbines and expanders, the term “gas turbine” as employed hereinafter will include both gas turbines as well as gas expanders, unless otherwise stated.
In one principal aspect of the present invention, a multistage gas turbo-machine includes a first stage and a subsequent stage of differing sizes. Each stage has turbo-machine blades which are contacted by the gas, an inlet in each stage for introducing the gas to the turbo-machine blades in the stage, a discharge from each stage for discharging the gas from the turbo-machine blades in the stage, and the discharge from one stage communicates with the inlet of the other stage. The first and subsequent stages are substantially identical to each other in design and geometric shape, but the linear dimensions of the subsequent stage differ from those of the first stage substantially in accordance with the formula
L
T
=
D
T
3
where L
T
is the ratio of the linear dimensions of the subsequent stage to the first stage and D is the gas density ratio of the first stage, and
D
T
=
(
M
A
+
M
B
tot
M
A
)
(
P
I
/
P
O
T
I
/
T
O
)
n
-
1
where:
M
A
=molar volume flow rate to intake of stage 1, moles/sec;
M
B tot
=total tributary volume added to or between all preceding stages, moles/sec;
P
I
=absolute pressure of gas entering stage in question;
P
O
=absolute pressure of gas leaving stage in question;
T
I
=absolute temperature of gas entering stage in question;
T
O
=absolute temperature of gas leaving stage in question; and
n=number of the stage in question.
In another principal aspect of the present invention, the gas turbo-machine includes a power transmission shaft, and at least some of the turbine blades are coupled to the shaft to rotate with the shaft, and the shaft and the rotating turbine blades of the first and subsequent stages rotate at the same speed.
In still another principal aspect of the present invention, the gas turbo-machine is either an axial flow or a radial flow gas turbo-machine.
In still another principal aspect of the present invention, the gas turbo-machine is a compressor, and the linear dimensions of the subsequent stage are smaller than the linear dimensions of the first stage substantially in accordance with the formula.
In still another principal aspect of the present invention, the first and subsequent stages of the compressor are substantially isothermal.
In still another principal aspect of the present invention, the first stage of the compressor also includes stator blades, and the stator blades include an inlet and outlet for passing a coolant through the blades to cool the gas to the substantially isothermal temperature before the gas is discharged from the first stage.
In still another principal aspect of the present invention, at least the first stage of the compressor is substantially adiabatic.
In still another principal aspect of the present invention, the compressor includes an intercooler between the first stage and a next stage to cool the gas discharged from the first stage before the gas enters the inlet of the next stage.
In still anot
Casaregola Louis J.
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
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