IL107530A - Method of and apparatus for augmenting power produced by gas turbines - Google Patents

Description

METHOD OF AND APPARATUS FOR AUGMENTING POWER PRODUCED BY GAS TURBINES .

DESCRIPTION METHOD OF AND APPARATUS FOR AUGMENTING POWER PRODUCED FROM GAS TURBINES Technical Field The present invention relates to a method of and apparatus for augmenting power produced from gas turbines, and more particularly, to a method of and apparatus for augmenting power produced form gas turbines in a combined cycle ground-based power plant.

Background Art A combined cycle power plant is one in which the exhaust gases produced by a gas turbine are used to operate a steam boiler that produces steam supplied to a steam turbine. The power produced by such a combined cycle power plant is the sum of the outputs of the generators driven by the respective turbines. It is conventional to increase the work produced by the gas turbine by reducing the turbine inlet temperature, and by increasing the turbine inlet pressure. In the American Society of Mechanical Engineers Paper No. 65-GTP-8 (1965) by R.W. Foster-Pegg, the author describes supercharging a gas turbine (i.e., increasing the inlet pressure) by using a forced draft fan in order to increase the power output of the turbine. The detrimental effect on the power output of the gas turbine due to the increase in inlet air temperature resulting from the fan operation is compensated for by spraying water into the air leaving the fan and before the air is applied to the turbine to bring about cooling of this air. The ambient air temperature and humidity control the effect this expedient has on the increase in power output of the turbine. Under hot, humid conditions, this technique has not proved to be effective.

In addition, gas turbines produce reduced work at high ambient temperatures due to a reduction in the mass flow of air through the system. Such high ambient temperatures, in a combined cycle utilizing a steam turbine operating on steam generated by the exhaust gases of the turbine, 107530/2 furthermore cause a reduction in the mass flow of exhaust gases thus reducing the work produced by the steam turbine. Even so, the effect on steam turbine performance will be partially compensated for, under high ambient temperature conditions, when water cooled condensers are used, because of the increased exhaust gas temperature. However, when air cooled condensers are utilized, high ambient temperatures will have a detrimental effect. In such case, the work produced by the steam turbine is reduced due to the lower mass flow on the gases exiting the turbine, is recovered somewhat due to the higher temperature of the gases, but is further reduced due to the higher condensing pressure prevailing in the air cooled condenser.

U.S. Patent No. 3,796,045 discloses a gas turbine power plant in which air supplied to the compressor of the gas turbine is first passed through a motor driven fan that pressurizes the supplied air, and then through a deep-chiller which may be a conventional compression-type ref igeration unit. The net power developed as a result of this approach exceeds the net power of a gas turbine power plant without precompression and deep chilling. In another embodiment shown in the '045 patent, a waste heat converter is provided for utilizing the heat in the exhaust gases of the gas turbine to drive the fan and the deep chiller.

U.S. Patent No. 5,321,944, matured from a continuation-in-part application of U.S. patent application Serial No. 07/818,123, filed January 8, 1992 discloses an improved chiller for deep chilling the air supply to a gas turbine. The term "deep chilling" is used in this specification to mean chilling ambient air to a temperature significantly below ambient air temperature. Specifically, deep chilling refers to chilling the air to the minimum temperature considered suitable for inlet chilling in a ground-based gas turbine based power plant of the type conventionally used by utilities for supplying power to an electrical grid. Such temperature is usually about 45°F (10°C) to avoid ice-built up in the blades of the main compressor driven by the gas turbine . taking into account a drop of about 10 °F (5°C) in the static air temperature in the compressor inlet, and a 3°F (2°C) safety margin.

Deep chilling at installations where the relative humidity is high is not cost effective. For example, deep chillers, and evaporative chillers as well, are not used in Florida, or other humid locations on the east coast of the United States, but are very common in dry areas of California.

It is therefore an object of the present invention to provide a new and improved method of and an apparatus for augmenting power produced from gas turbines by providing a new and improved technique for precompressing and cooling hot, precompressed ambient air.

Brief Description of the Invention The invention provides for augmenting the power produced by a gas turbine system of the type having a main compressor for compressing ambient air supplied to the compressor to produce compressed air, a combustor for heating the compressed air and producing hot gases, and a gas turbine responsive to the hot gases for driving the main compressor and supplying a load, and for producing hot exhaust gases. According to the present invention, power augmentation is provided for by utilizing a precompressor device for compressing ambient air, a cooler for indirectly cooling the compressed air and producing cooled compressed air that is supplied to the main compressor, preferably a boiler responsive to hot gases produced by said gas turbine for producing steam, and preferably a steam turbine responsive to steam produced by said boiler for supplying a load. The use of a cooler, usually having a refrigerant cycle, instead of evaporative cooling of. the compressed air, in conjunction with precompression, is advantageous because it renders the apparatus insensitive to humidity conditions of the ambient air. Preferably, the working fluid of the cooler is environmentally safe, e.g., butane.

Chilling, deep chilling, or cooling using evaporative cooling, is not cost effective in locations where the humidity is relatively high because of the high latent heat load imposed on the system. A system using a precompressor and a cooler in accordance with the present invention is just about the best solution under high humidity conditions. In accordance with the present invention, precompression producing a pressure ratio of about 1.15 is used.

The cooling in the present invention is used at temperature ranges different form those used in evaporative coolers and deep chillers. In accordance with the present invention, cooling effects a reduction in temperature of the precompressed air to about that of ambient air, whereas in evaporative cooling and/or deep chilling, the temperature of the air is reduced well below that of ambient air. Consequently, according to the invention, the drying of humid air is not required unlike the the methods employed with evaporative coolers and deep chillers where the cooling load will increase by a factor of three under humid conditions. The present invention not only improves the coefficient of performance, but does so without the penalty of the increased load under humid conditions.

When the relative humidity is high, cooling in the present invention will reduce the air temperature to a level slightly above ambient air temperature. Otherwise, the cooling will reduce the air temperature to a level slightly below ambient temperature if this is cost effective. In a combined cycle power plant, according to the present invention, however, the consequences of reducing the air temperature slightly below ambient temperature must be taken into consideration. Preferably, at locations where the relative humidity is about 80% or more-., and even close to 100%, the precompressed air may be cooled to about 5°C. above ambient temperature, and at locations where the relative humidity is between 50% and 80%, the precompressed air may be cooled to about 10°C. below ambient temperature, depending on the cost effectiveness of the systems.

The present invention is also effective in dry areas where the use of deep chillers or evaporative coolers is not economically feasible (e.g., at locations where the water resources are limited, or are polluted) . Furthermore, in accordance with the present invention, operation at temperatures above ambient temperature permits use of less expensive heat exchangers that operate using ambient air as the cooling medium, rather than refrigerant.

In addition, by cooling to the temperatures in accordance with the present invention, the work produced by the gas turbine, as well as a steam turbine in a combined cycle, will be enhanced. As to the steam turbine, the work produced will be greater than would be the case were deep chilling and/or evaporative cooling utilized because more heat will be available inasmuch as the temperature of the exhaust gases exiting the gas turbine will be higher than they would be were deep chilling and/or evaporative cooling utilized. This is particularly true under conditions of high ambient temperature because the temperature range of cooling according to the present invention will bring about an increase in the temperature of the exhaust gases exiting the gas turbine to a level substantially the same as if no cooling were used.

Furthermore, a combined cycle power plant according to the present invention should be operated such that the heat recovery steam generation (HRSC) of the plant takes place under substantially constant conditions (particularly volume flow rate) in the face of changing ambient conditions. This can be achieved completely by controlling the level of cooling effected by the cooler such that the temperature of the precompressed air at the outlet of the cooler is maintained substantially constant regardless of ambient conditions. Such operation permits the design of the HRSC of a combined cycle ; power plant to be optimized to essentially a single point such that operation of the power plant will be close to its design level under all ambient conditions.

By comparison, a conventional combined cycle power plant is designed to operate over a range of conditions (including, for example, 30% fluctuations in air mass flow) . Consequently, the HRSC in conventional combined cycle power plants is such that consideration is taken of all conditions likely to be met during the course of operation with the result that sizing and optimization is adversely affected. Thus, conventional combined cycle power plants usually will operate at off-design conditions most of the year. By constructing a combined cycle power plant in accordance with the present invention, operation will be at substantially the optimum point all year resulting in a saving of as much as 10% in the capital costs of design and construction as a result of the reduced size of the HRSC, and additional operational savings as well due to the improvement in efficiency.

Additionally, a gas turbine system according to the present invention should be operated at substantially constant conditions (particularly volume mass flow) in the face of changing ambient conditions. This can be achieved completely by controlling the level of cooling effected by the cooler such that the temperature of the precompressed air at the outlet of the cooler is maintained substantially constant regardless of ambient conditions. Such operation permits the gas turbine system to operate at a point substantially close to design conditions such that operation of the power plant will be close to its design level under all ambient conditions.

In a further aspect of the present invention, the exit gases of the gas turbine system of a >power plant having a precompressor device and a cooler, can be used for cogeneration (i.e., for producing steam for use as process heat) . In such case, in accordance with the present invention, it is advantageous to operate the system at substantially constant conditions (particularly its volume flow rate) in the face of changing ambient conditions. This can be achieved completely by controlling the level of cooling effected by the cooler such that the temperature of the precompressed air at the outlet of the cooler is maintained substantially constant regardless of ambient conditions. Such operation is particularly advantageous in cogeneration systems because the heat is part of an industrial process requiring continuous operation under constant conditions.

Use of cooling after precompression in accordance with the present invention is much more cost effective than chilling, deep chilling, or evaporative cooling. A comparison of cooling after precompression with deep chilling (with or without evaporative cooling) when ambient temperature is about 35°C. illustrates this point. By cooling after precompression, the air temperature at the inlet to the main compressor will drop from the range of about 50-60°C. to the range about 25-35 °C.. With deep chilling (with or without evaporative cooling) , the air temperature drops from about 35°C. to the range of about 5-10°C. A system utilizing precompression will be both more efficient and less expensive.

Precompressio and cooling in accordance with the present invention enhances the capacity of a system by up to 20-30%. Moreover, the power output is made insensitive to local weather conditions.

In an additional aspect of the present invention, the precompression can be used as a substitute for a heater which which is normally needed during periods of cold weather. In such case, the precompressor will increase the temperature of the air at the entrance top the main compressor thus inhibiting ice formation therein. Freezing in the precompressor can be avoided, in accordance with the present invention, by including a centrifugal drop remover at the inlet to the precompressor. Alternatively, the entrance to the precompressor can be designed to ensure that drops of water do not significantly influence the performance of the precompressor. Alternatively, or i addition, part of the hot precompressed air can be recirculated in order to heat the air entering the precompressor. Such an arrangement is much simpler than recirculating air extracted from a stage of the main compressor for preheating the air entering the main compressor.

In another aspect of the invention, a filter device is interposed between the precompressor device and the main compressor for filtering air from the precompressor device and introducing a pressure drop in the supplied air. The precompressor device is constructed and arranged so that the pressure rise introduced thereby is at least larger in size than the pressure drop introduced by the filter device. Moreover, the cooler provided for cooling the supplied air by introducing a temperature drop therein preferably can be positioned upstream or downstream of the filter device.

Filters used in the present invention will be more efficient, and have longer lifetimes because they operate closer to design mass flow rate, and other design conditions for longer periods of time.

The relatively modest pressure drop that occurs by reason of the filter ahead of the main compressor of the gas turbine, a component that is absolutely necessary in a ground-based installation for utilities providing power to a grid, is easily accommodated by a fan-like compressor which is simple to operate and maintain and requires only a small amount of energy for operation. Moreover, the relatively modest temperature drop which is effected by the low capacity cooling of the air can be accomplished without a significant expenditure of energy.

The air exiting the precompression stage and the cooler in such an arrangement, will be at substantially ambient air temperature but at a pressure at least high enough to compensate for the pressure drop in the filter associated with the main compressor of the gas turbine. The total energy requirement for the operation can be accommodated easily by a portion of the output of the steam turbine of a combined cycle power plant, for example, responsive to exhaust gases of the gas turbine. As a result, an overall system that is more efficient than the original gas turbine power plant can be achieved without significantly adding to the cost and complexity of the power plant, as well as its maintenance.

Brief Description of the Drawings Embodiments of the present invention are described by ■ way of example and with reference to the accompanying drawings wherein: Fig. 1 is a block diagram, in schematic form, of one embodiment of the present invention showing a combined cycle that utilizes precompression and cooling; Fig. 2 is a block diagram, in schematic form, of another embodiment of the present invention showing low capacity precompressing and cooling utilizing an externally driven power source; Fig. 3 is a schematic block diagram similar to Fig. 1 but showing the precompressor and low capacity cooler being operated by a steam turbine unit responsive to exhaust gases from the gas turbine; Fig. 4 is a modification of the invention showing precompressing and chilling occurring in parallel stages; and Fig. 5 shows an embodiment of a cooler used in the present invention including an embodiment of a controller for controlling the level of cooling achieved by the cooler.

Detailed Description Referring now to the drawings, reference numeral 100 designates the first embodiment of the present invention shown in Fig. 1 comprising a ground based, combined-cycle power plant having main compressor 130 for compressing ambient air supplied to the compressor to produce compressed air, combustor 140 for heating the compressed air and producing hot gases, and gas turbine 150 responsive to the hot gases for driving the main compressor through interconnecting shaft 160, and for supplying load 170 which, typically, is in the form of an electrical generator. Turbine 150 produces hot exhaust gases which are directed to boiler 180 containing water that is evaporated into steam by the exhaust gases which are then vented to the ambient atmosphere, usually through a muffler (not shown) . The steam is applied to steam turbine 181 where expansion takes place producing work that is supplied to load 182. The steam exhausted from the turbine after work has been produced is condensed in condenser 183 producing condensate that is returned to the boiler by pump 184 to repeat the cycle.

Compressed air for main compressor 130 is supplied by precompressor 110 driven by motor 111. The compressed air, having been heated by the compression process, is applied to cooler 112 which cools the air reducing its temperature to about ambient temperature. The cooler can be part of a mechanical refrigeration system (not shown) that provides refrigerant to the cooler. Preferably, the cooled, compressed air is passed through filter 113 before being supplied to main compressor 130. A centrifugal filter is preferred.

Fig. 2 shows a second embodiment of the present invention wherein reference numeral 10 designates a power plant comprising a conventional power plant 11 to which low capacity precompression and cooling is applied by apparatus 12. Power plant 11 represents a large-scale, ground-based, power plant conventionally used to supply power to an electrical grid. Plant 11 comprises main compressor 13 for compressing ambient air supplied to the compressor to produce compressed air, combustor 14 for heating the compressed air and producing hot gases, and gas turbine 15 responsive to the hot gases for driving the main compressor through interconnecting shaft 16, and for driving load 17 which, typically, is in the form of an electrical generator. Turbine 15 produces hot exhaust gases which usually are vented into the ambient air through a muffler system (not shown) .

In large ground-based installations used by utilities for generating power that is supplied to an electrical grid, filter device 18 is an integral part of the air supply system to main compressor 13, and is necessary in order to protect the compressor from entrained particles that could damage the blading of the compressor. Filter device 18 introduces a pressure drop in the air supplied to the main compressor. As a consequence, the pressure of the air at the inlet to compressor 13 will be below the pressure of the air at the inlet to filter device 18.

The pressure developed by precompressor device 20 can be used to at least compensate for the pressure drop through the filter. Device 20 compresses ambient air applied to the main compressor thereby introducing both temperature and pressure rises in the supplied air. The term "supplied air", as used in this specification, refers to air supplied through the main compressor.

As shown in Fig. 2, the temperature and pressure rise in the precompressor device is designated by +del T and +del P. Precompressor device 20 is constructed and arranged such that the pressure rise introduced by the device is at least greater in size than to the pressure drop introduced by filter device 18. However, in accordance with the present invention, pressure of the air applied to main compressor 13 will be greater than ambient sir pressure.

Interposed between precompressor device 20 and inlet air filter 18 is low capacity cooler 21 which introduces a temperature drop of about -del T into the air supplied to the compressor. The design of cooler 21 is such that the temperature introduced by the cooler is substantially comparable in size to the temperature rise introduced by precompressor device 20. As a consequence of cooler 21, the temperature of the air entering main compressor 13 usually is substantially close to ambient temperature.

Instead of an external electrically driven motor to drive the precompressor , the latter can be driven directly from a steam turbine unit operated by exhaust gases from the gas turbine, e.g., when a combined cycle is used wherein the main product produced by the steam turbine is electric power. Referring now to Fig. 3, power plant 30 comprises precompressor device 20A and low capacity cooler 21A similar to the corresponding components shown in Fig. 1. Low capacity cooler 21A as well as other coolers disclosed herein can use a refrigerant cycle for cooling the precompressed air. Preferably, the working fluid of the cooler is environmentally safe, e.g., butane. However, power plant 30 includes steam turbine unit 31 which includes vaporizer 32 containing water as the working fluid, and responsive to exhaust gases produced by gas turbine 15 for producing steam. The steam is applied to turbine 33 via conduit 34, the turbine being responsive to the steam for producing power and also directly driving precompressor device 20A by means of shaft 35 which directly couple the turbine to the precompressor device. The expansion of steam in turbine 33 produces work that also powers precompressor device 20A with the steam exiting the turbine at exhaust 36 after work has been produced. In addition, as shown, cooler 21A can be powered by turbine 33.

The steam exiting the turbine at exhaust 36 is condensed in condenser 37 producing condensate which is directed through conduit 38 o pump 39 which returns the condensate to the vaporizer thus completing the working fluid cycle. Condenser 37 is preferably air cooled, any necessary fan means (not shown) being powered usually by external motors. Directly driving precompressor device 20A, as well as cooler 21A, with turbine 33 using shaft 35, results in a reduction in both the size of a generator (indicated in Fig. 3 by load 22) associated with the turbine, as its losses.

In operation, ambient air is drawn into precompressor device 2 OA, which introduces a temperature and pressure rise. The air leaving precompressor device 20A passes to low capacity cooler 21A which introduces a temperature drop usually substantially close to the temperature rise introduced by precompressor device 2 OA. The air then passes to filter device 18 which introduces a pressure drop. As a result, the temperature of the air supplied to main compressor 13 usually will be substantially close to ambient temperature, and the pressure will be slightly above atmospheric pressure. The main compressor compresses this air, supplies it to combustdr 14 where the air is heated by the combustion of fuel and supplied to turbine 15 which drives load 17. Exhaust gases from the turbine are usually presented to steam turbine unit 31 such that turbine 33 produces power and also drives precompressor device 2 OA and cooler 21A. Alternatively, some of the electric power produced by turbine 33 can be made available to a conventional refrigeration system which supplies coolant to cooler 21A.

Embodiment 40 of the present invention shown in Fig. 4 is similar to that shown in Fig. 2 except that the precompression, and low capacity cooling, are carried out in separate units in parallel. To this end, the precompressor device is in the form of individual precompressors 41, 42, 43 that supply ambient air in parallel to filter device 18A which also comprises a plurality of individual filters 45, 46, 47 which are respectfully associated with the individual compressors. In this embodiment, low capacity cooler 21A comprises individual coolers 48, 49, 50 which are respectfully associated with the individual compressors. An advantage of the arrangement shown in Fig. 4 is that the various air filters and precompressors as well as low capacity coolers can be taken on and off line individually without affecting the operation of the power plant 11A. A further advantage of such an arrangement is that it facilitates construction in that a filter for a complete power plant is a large and costly piece of equipment.

In addition, in accordance with the present invention, the embodiment shown in Fig. 4 can be used such that a combined cycle power plant using the embodiment of Fig. 4 can be included in a manner similar to that shown and described with reference to Figs. 1 and 3.

According to the present invention, the precompression employed produces a pressure ratio of about 1.15, and cooling is performed to reduce the temperature of the precompressed air to a temperature about that of ambient air. In contrast, in evaporative cooling and/or deep chilling, the air temperature is reduced to a level significantly below ambient temperature.

Under conditions of relatively high humidity, a system using a precompressor and a cooler in accordance with the above described embodiments of the present invention is particularly advantageous. According to the present invention, dehumidification of very humid air is not necessary; and in fact, the coefficient of performance is improved under humid conditions. In contrast, in conventional systems employing evaporative coolers and deep chillers, the cooling load may triple under humid conditions unless dehumidification is first carried out.

Under humid conditions, i.e., when the relative humidity is relatively high, cooling in accordance with the present invention will reduce the temperature of the precompressed air to a level slightly above ambient air temperature. If cost effective, however, the air will be cooled to slightly below ambient temperature. However, when a combined cycle power plant having a steam turbine is utilized, the effect of the reduced temperature of the exhaust gases produced by the gas turbine on the power produced by the steam turbine must be taken into consideration. Preferably, at locations where the relative humidity is about 80% or more, and even close to 100%, the precompressed air may be cooled to about 5°C. above ambient temperature, and at locations where the relative humidity is between 50% and 80%, the precompressed air may be cooled to about 10°C. below ambient temperature, depending on the cost effectiveness of the systems.

Furthermore, a combined cycle power plant according to the present invention, for example, as shown and described with reference to Figs. 1 and 3, should be operated such that the heat recovery steam generation (HRSC) of the plant takes place under substantially constant conditions (particularly volume flow rate) in the face of changing ambient conditions. This can be achieved completely by controlling the level of cooling effected by the cooler (an example of means for such controlling being shown in Fig. 5) such that the temperature of the precompressed air at the outlet of the cooler is maintained substantially constant regardless of ambient conditions. Such operation permits the design of the HRSC of a combined cycle power plant to be optimized to essentially a single point such that operation of the power plant will be close to its design level under all ambient conditions. An example- of means for such controlling is shown in Fig. 5 and designated numeral 200, wherein control 202 controls 'eg. the quantity of cooling medium supplied to cooler 204 for cooling precompressed air entering cooler 204 at inlet 206 in order to control the temperature of precompressed air exiting cooler 204 at precompressed air outlet 208.

By comparison, a conventional combined cycle power plant is designed to operate over a range of conditions (including, for example, 30% fluctuations in air mass flow). Consequently, the HRSC in conventional combined cycle power plants is such that consideration is taken of all conditions likely to be met during the course of operation with the result that sizing and optimization is adversely affected. Thus, conventional combined cycle power plants usually will operate at off-design conditions most of the year. By constructing a combined cycle power plant in accordance with the present invention, operation will be at substantially the optimum point all year resulting in a saving of as much as 10% in the capital costs of design and construction as a result of the reduced size of the HRSC, and additional operational savings as well due to the improvement in efficiency.

Additionally, a gas turbine system according to the present invention should be operated at substantially constant conditions (particularly volume mass flow) in the face of changing ambient conditions. This can be achieved completely by controlling the level of cooling effected by the cooler (an example of means for such controlling being shown in Fig. 5) such that the temperature of the precompressed ¾air at the outlet of the cooler is maintained substantially constant regardless of ambient conditions. Such operation permits the gas turbine system to operate at a point substantially close to design conditions such that operation of the power plant will be close to its design level under all ambient conditions.

In a further aspect of the present invention, as described in relation to Figs. 1 and 3, the exit gases of the gas turbine system of a power plant having a precompressor device and a cooler, can be used for cogeneration (i.e., for producing steam for use as process heat) . In such case, in accordance with the present invention, it is advantageous to operate the system at substantially constant conditions (particularly its volume flow rate) in the face of changing ambient conditions. This can be achieved completely by controlling the level of cooling effected by the cooler such that the temperature of the precompressed air at the outlet of the cooler is maintained substantially constant regardless of ambient conditions. Such operation is particularly advantageous in cogeneration systems because the heat is part of an industrial process requiring continuous operation under constant conditions.

When gas turbines or power plants constructed in accordance with the present invention are built near natural resources of water, such as a sea, a river, or a lake, etc. , or near a cooling tower and its source of cooling water, water from such source can be used as the cooling medium in the indirect cooler of the gas turbine for cooling the precompressed gases. In such case, particularly where where cooling involves reducing the temperature of the precompressed gases to a temperature close to ambient temperature, a simple, indirect water-air heat exchanger without a mechanical cooler because the temperature of the water source will be below ambient air temperature.

In a still further aspect of the invention, when a gas turbine or combined cycle power plant is operated according to the present invention in a humid location under the condition that the precompressed gases are cooled to a temperature slightly below ambient temperature, water produced by the condensation of water vapor in the air as the precompressed air is cooled can be used for controlling the oxides of nitrogen in the exhaust gases by adding ^his water to the combustion process that takes place in the combustor of the gas turbine. Thus is made possible because the water produced has a relatively high level of purity.

The embodiments of the present invention are also effective in dry areas where particular limitations lead to a desire to avoid the use of deep chillers or evaporative coolers, e.g., a location where the availability of v/ater resources is limited making the use of evaporative coolers costly, where water resources are polluted, etc. Furthermore, in accordance with the present invention, since often cooling is to temperatures above ambient temperatures, air coolers, i.e., heat exchangers not using a refrigeration cycle but using ambient air instead as the cooling medium can be used as the coolers in the above described embodiments.

Furthermore, in an dditional aspect of the present invention, the precompressi i produced by the precomprassors in the above described em, ^diments can be used as well instead of a heater needed for use in cold weather. Accordingly, the precompressor increases the temperature of air at its exit so as to minimize the chance of ice forming in the main compressor. The occurrence of freezing in the precompressor is substantially avoided in accordance with the present invention by including a mechanical centrifuge drop remover. Alternatively, the entrance of the precompressor is designed to ensure that drops of water do not significantly influence the performance of the precompressor. Furthermore, or in conjunction with both these alternatives, part of the hot precompressed air can be recirculated in order to heat the air entering the precompressor. Such an arrangement is much simpler than recirculating air extracted from a stage in the main compressor for heating air entering the main compressor.

Precompression of a pressure ratio of 1.15 and cooling in combination in accordance with the above described embodiments of the present invention provides enhanced capacity of up to 20% at 35 degrees C ambient temperature. Moreover, the increased capacity is almost totally independent of weather conditions with the result that a power plant based on the present invention is cost effective in most industrialized countries where hot, humid summer conditions are the norm.

The advantages and improved results furnished by the method and apparatus of the present invention are apparent form the foregoing description of the preferred embodiment of the invention. Various changes and modifications may be made without departing from the spirit and scope for the invention as described in the appended claims.

Claims (1)

1. 07530/3 Apparatus for augmenting the power produced by a gas turbine system of the type having a main compressor for compressing air supplied to said compressor to produce compressed air, a combustor for heating the compressed air and producing hot gases, and a gas turbine responsive to said hot gases for directly driving said main compressor and a load, and for producing hot exhaust gases, said apparatus comprising: a) a precompressor for precompressing ambient air thereby introducing temperature and pressure rises in the air supplied to entering the main compressor, said precompressor being driven by a motor separate from said gas turbine; b) a cooler for indirectly cooling the precompressed air by introducing a temperature drop therein comparable to the temperature rise due to the precompressor; and c) said precompressor and cooler being constructed and arranged such that: (1) the temperature of air entering said main compressor is comparable to the 107530/3 temperature of ambient air, and (2) the pressure rise across said precompressor is not greater than about 115% of ambient air . Apparatus for augmenting the power produced by a gas turbine system of the type having a main compressor for compressing air supplied to said compressor to produce compressed air, a combustor for heating the compressed air and producing hot gases, and a gas turbine responsive to said hot gases for directly driving said main compressor and a load, and for producing hot exhaust gases, said apparatus comprising; a) a precompressor for precompressing ambient air thereby introducing temperature and pressure rises in the air supplied to the main compressor, said precompressor being driven by a motor separate from said gas turbine; b) a cooler for indirectly cooling the precompressed air by introducing a temperature drop therein comparable to the temperature rise due to the precompressor; and 107530/2 c) said precompressor having a pressure ratio of about 1:1.15. 3. Apparatus according to claim 2 including a filter device interposed between said precompressor and said main compressor for filtering air from said precompressor and introducing a pressure drop in the air supplied to the main compressor. 4. Apparatus according to any of claims 1-3 including a boiler responsive to said hot exhaust gases produced by said gas turbine for producing steam. 5. Apparatus according to claim 4 including means for using said steam for cogeneration. 6. Apparatus according to claim 4 including a steam turbine responsive to steam produced by said boiler for supplying a load. 7. A method for augmenting the power produced by a gas turbine system of the type having a main compressor for compressing air supplied to said compressor to produce compressed air, a combustor for heating the compressed air and producing hot gases, a gas turbine responsive to said hot gases for driving said main compressor and a load, and for producing hot exhaust gases, said method comprising the steps of : 107530/2 a) precompressing ambient air thereby introducing temperature and pressure rises in the air supplied to entering the main compressor, said device being driven by a motor separate from said gas turbine; b) indirectly cooling the precompressed air by introducing a temperature drop therein comparable to the temperature rise due to the precompressor; and c) carrying out the steps of precompressing ambient air and indirectly cooling the precompressed air to a level where: (1) the temperature of air entering said main compressor is comparable to the temperature of ambient air, and (2) the pressure rise across said precompressor is not greater than about 115% of ambient air. A method according to claim 7 including the step of providing a boiler responsive to said hot exhaust gases produced by said gas turbine for producing steam. A method according to claim 7 including the step of providing means for using said steam for cogeneration. 107530/2 10. A method according to claim 8 including the step of providing a steam turbine responsive to steam produced by said boiler for supplying a load. 11. A method according to any of claims 7-10 including carrying out the said method in dry areas where the availability of water resources is limited. 12. A method according to any of claims 7-11 wherein the step of indirectly cooling is carried out by controlling the cooling level of the cooler such that the temperature of the precompressed air after cooling is substantially independent of changing ambient conditions. 13. A method according to any of claims 7-12 wherein said method of augmenting power is carried out at substantially constant conditions in the face Of changing ambient conditions by reducing the size of the heat recovery steam generation. 14. A method according to any of claims 7-13 wherein the temperature drop introduced by the step of indirectly cooling is slightly larger than the temperature rise introduced by the step of precompressing such that the temperature of the precompressed air obtained by the step of cooling is slightly below ambient temperature, and water is produced by the condensation of water vapor in the precompressed air, and the water so produced 107530 is injected into the combustor of said gas turbine for controlling oxides of nitrogen produced by said combustor. A method according to any of claims 7-14 wherein the step of indirectly cooling is carried out by indirectly cooling the precompressed air using a mechanical refrigeration system. A method according to any of claims 7-14 wherein the step of indirectly cooling is carried out by indirectly cooling the precompressed air using water from a natural resource of water. A method according to any of claims 7-14 wherein the step of indirectly cooling is carried out by indirectly cooling the precompressed air using water from a lake. A method according to any of claims 7-14 wherein the step of indirectly cooling is. carried out by indirectly cooling the precompressed air using water from the sea. A method according to any of claims 7-14 wherein the step of indirectly cooling is carried out by indirectly cooling the precompressed air using water from a river. 107530/: A method according to any of claims 7-14 wherein the step of indirectly cooling is carried out by indirectly cooling the precompressed air using water cooled by a cooling tower. 21. A method according to any of claims 7-14 wherein the step of cooling is carried out by indirectly cooling the precompressed air with ambient air. 22. Apparatus for augmenting the power according to claim 1 substantially as hereinbefore described and with reference to the accompanying drawings . 23. Apparatus for augmenting the power according to claim 2 substantially as hereinbefore described and with reference to the accompanying drawings. 24. A method for augmenting the power according to claim 7 substantially as hereinbefore described and with reference to the accompanying drawings. For the Applicant Y.. VBBeecck - § -