WO2002014664A1

WO2002014664A1 - Gas turbine engine having improved efficiency

Info

Publication number: WO2002014664A1
Application number: PCT/US2001/041714
Authority: WO
Inventors: Paul A. Dellenback
Original assignee: University Of Wyoming
Priority date: 2000-08-15
Filing date: 2001-08-14
Publication date: 2002-02-21
Also published as: AU2001295007A1

Abstract

A gas turbine engine having a compressor (12), a regenerator (14), a combustor (16), a high pressure turbine (18), and a power turbine (20) is arranged for directing gas from the high pressure turbine (18) to the regenerator (14) and than to the power turbine (20). An improved efficiency operating cycle is also provided.

Description

GAS TURBINE ENGINE HAVING IMPROVED EFFICIENCY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to an apparatus and method for improving efficiency in a gas turbine engine and, more particularly, it relates to an apparatus and method for improving efficiency in a gas turbine engine by utilizing an alternative regenerator configuration.

2. Description of the Prior Art In recent years, gas turbine engine (GTE) applications have been appreciably expanded due to significant improvements in cycle efficiency. Simple cycle efficiencies of over forty (40%) percent are now possible from some designs, making gas turbine engines competitive alternatives to Diesel engines and Rankine steam cycles. Most gas turbine engine applications can accommodate the space and mass requirements associated with adding regeneration to a simple cycle, with the goal of even higher cycle efficiencies. Regeneration in gas turbine engines has been described as using a heat exchanger to move heat from one point in a cycle to another point in a cycle. Traditionally, regenerators (heat exchangers) have been used with gas turbine engines to recover heat from high temperature exhaust gases. High temperature and high pressure gases flow across the turbines to extract the maximum possible amount of power before any heat is recovered with the heat exchanger. Numerous applications for the recovered heat have been devised, but on stand- alone gas turbine engine cycles, the most usual of these is the preheating of air passing between compressor and combustor. In this way, a well-known concept of thermodynamics is satisfied by increasing the average temperature at which heat is added to air during combustion, resulting in increased cycle efficiency. Regenerators have traditionally been used downstream of the final turbine stage so that the maximum amount of work is extracted from the high-temperature gas stream before any heat is removed. However, since thermodynamic principles suggest that maximizing cycle efficiency should focus attention on increasing the temperature at which heat is added, and not on maximizing the work output, the overall efficiency of conventional regenerative gas turbine engine cycles can be improved through an alternative regenerator location.

SUMMARY The present invention is a gas turbine engine having a compressor, a regenerator, a combustor, a high pressure turbine and a power turbine. The gas turbine engine comprises a first directing mechanism for directing gases from the high pressure turbine to the regenerator and a second directing mechanism for directing gases from the regenerator to the power turbine. The present invention further includes a method for improving the cycle efficiency in a gas turbine engine. The gas turbine engine has a compressor, a combustor, a regenerator, a high pressure turbine, and a power turbine. The method comprises directing gases from the compressor across the regenerator, directing gases from the regenerator across the combustor, directing gases from the combustor across the high pressure turbine, directing gases from the high pressure turbine across the regenerator, and directing gases from the regenerator across the power turbine.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing illustrating a gas turbine engine, constructed in accordance with the present invention, utilizing an alternative regeneration cycle; and FIG. 1A is a schematic drawing illustrating the gas turbine engine of FIG. 1, constructed in accordance with the present invention, with optimum efficiency scenarios (which are a function of operating parameters) requiring either, (a) the power turbine (PT) provides some compressor work, or (b) the high pressure turbine (HPT) provides all the compressor work in addition to some net shaft work.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in FIGS. 1 and 1A, the present invention is a gas turbine engine, indicated generally at 10, utilizing an alternative regenerator configuration to improve cycle efficiency relative to either simple cycles or conventional regeneration schemes. The improved efficiency occurs due to air entering the combustor at a higher temperature, and hence heat addition in the combustor occurs at a higher average temperature. The regenerator or heat exchanger operating conditions are well within the capability of modern heat exchangers. As illustrated in FIGS. 1 and 1A, the gas turbine engine 10 of the present invention includes a compressor 12, a regenerator or heat exchanger 14, a combustor 16, a high pressure turbine (HPT) 18, and a power turbine (PT) 20. With the alternative regeneration cycle of the gas turbine engine 10, as the gases exit the high pressure turbine 18, the gases are directed to the regenerator 14 prior to entering the power turbine 20. As a result, at least a portion of the power is extracted with the high-pressure turbine 18 and then heat is extracted from the moderate temperature and moderate pressure gases by the regenerator 14. Then, since the gases are still at elevated pressures above atmospheric, more power can be extracted by the power turbine 20. A shaft 22 can be provided between the high-pressure turbine 18 and the power turbine 20 thereby providing more power than the compressor 12 requires so that useful shaft power is available. Considering a gas turbine engine 10 configuration with the high-pressure turbine 18 and the power turbine 20, if a regenerator or heat exchanger 14 is located between the high pressure turbine 18 and the power turbine 20, as illustrated in FIG. 1, then the cycle efficiency of the gas turbine engine 10 can be substantially improved beyond that available from the "conventional regeneration" configuration. The thermodynamic effect is to increase the amount of heat that is delivered to the compressed air beyond what conventional regeneration is able to achieve, resulting in a higher average temperature for the heat addition process in the combustor 14. Although there is less work produced by the power turbine 20 in the "alternative regeneration" configuration due to the pressure and temperature drop of the gas as it passes through the regenerator 14, the cycle efficiency is improved and the lower specific work can be compensated for through larger engine components.

Optimized Configuration. FIG. 1 depicts the high pressure turbine 18 as powering the compressor 12, and the schematic has been illustrated in this way to be consistent with common gas turbine engine configurations consisting of a gas generator (i.e., the compressor 12, the combustor 14, and the high pressure turbine 18) and a power turbine 20. There are certain advantages to this arrangement, including the ability to run the high pressure turbine 18 and the power turbine 20 at different speeds. However, thermodynamically there is no reason why the optimum performance should correspond to this configuration and in fact, the best overall cycle efficiency usually occurs when the gases are not expanded so severely across the high pressure turbine 18. Thus, in most cases, some work from the power turbine 20 would also have to be directed to the compressor 12 utilizing the shaft 22 in the optimum efficiency scenario as illustrated in FIG. 1A. One important concern with the gas turbine engine 10 of the present invention utilizing the alternative regeneration configuration is the temperature experienced by the materials in the regenerator or heat exchanger 14 itself. Since the essence of the scheme is to use higher combustion gas temperatures to heat air to temperatures higher than those normally encountered in conventional regeneration, the regenerator or heat exchanger 14 requirements are more severe.

Conclusion The present invention is a gas turbine engine 10 having an alternative regeneration configuration for a regenerative gas turbine engine cycle with numerous favorable operating characteristics. Throughout practical ranges of operating parameters, the alternative configuration results in a cycle efficiency superior to either a conventional regenerative cycle or a simple cycle. The performance improvement of the present invention is robust and not limited to a narrow range of operating conditions or component efficiencies. Although the demands on the regenerator or heat exchanger are more severe than with conventional regeneration, the inventor of the present application has determined that the regenerator temperatures and pressures are well below the limits of high-technology heat exchanger designs. For example, for a turbine inlet temperature of 1100° C and an optimum pressure ratio of sixteen (16), a regenerator with effectiveness of 0.7 would provide about thirty (30 %) percent of the total heat input to the gas stream while operating at 810° C and about four (4) atmospheres, resulting in a cycle efficiency more than five (5) percentage points higher than a simple cycle. The gas turbine engine 10 with the alternative regeneration configuration of the present invention is also applicable to combined cycle plants. Combined cycle plants use both gas turbine engines and conventional Rankine steam cycles in the same design to offer improved efficiency. For current combined cycle designs, heat is removed from the gas turbine exhaust gases to preheat or boil water that can be used in the steam cycle. The gas turbine and steam turbine together turn an electrical generator. Since combined cycle efficiency is directly related to the efficiencies of the gas turbine and steam cycles, and since the gas turbine engine 10 utilizing the alternative regeneration configuration of the present invention improves the gas turbine cycle efficiency, then the combined cycle efficiency will exhibit an improved efficiency when alternative regeneration is incorporated. The high temperature exhaust gases from the gas turbine engine 10 can be used to heat an object, i.e., to heat a reaction in a chemical plant, to heat hops in a brewery, or to do space heating in a building. These cycles are known as "cogeneration cycles". In fact, any gas turbine engine application will benefit by employing the alternative regeneration cycle of the present invention. The foregoing exemplary descriptions and the illustrative preferred embodiments of the present invention have been explained in the drawings and described in detail, with varying modifications and alternative embodiments being taught. While the invention has been so shown, described and illustrated, it should be understood by those skilled in the art that equivalent changes in form and detail may be made therein without departing from the true spirit and scope of the invention, and that the scope of the present invention is to be limited only to the claims except as precluded by the prior art. Moreover, the invention as disclosed herein, may be suitably practiced in the absence of the specific elements which are disclosed herein.

Claims

CLAIMSWhat is claimed is:

1. A method for improving the cycle efficiency in a gas turbine engine, the gas turbine engine having a compressor, a combustor, a regenerator, a high pressure turbine, and a power turbine, the method comprising: directing gases from the compressor across the regenerator; directing gases from the regenerator across the combustor; directing gases from the combustor across the high pressure turbine; directing gases from the high pressure turbine across the regenerator; and directing gases from the regenerator across the power turbine.

2. The method of claim 1 and further comprising: extracting energy from the gases with the high pressure turbine thereby creating moderate temperature and moderate pressure gases; extracting heat in the regenerator for preheating compressor discharge air; directing the moderate temperature and moderate pressure gases to the power turbine; and extracting additional energy from the gases with the power turbine.

3. The method of claim 1 wherein cycle efficiency of the gas turbine engine relative to either simple cycles or conventional regeneration schemes is improved.

4. The method of claim 1 and further comprising: connecting a shaft between the high pressure turbine and the power turbine.

5. The method of claim 1 and further comprising: utilizing the gas turbine engine in a combined cycle.

6. The method of claim 1 and further comprising: utilizing the gas turbine engine in a cogeneration cycle.

7. A gas turbine engine having a compressor, a regenerator, a combustor, a high pressure turbine and a power turbine, the gas turbine engine comprising: first directing means for directing gases from the high pressure turbine to the regenerator.

8. The gas turbine engine of claim 7 and further comprising: second directing means for directing gases from the regenerator to the power turbine.

9. The gas turbine engine of claim 8 and further comprising: first extracting means associated with the high pressure turbine for extracting energy from the gases with the high pressure turbine thereby creating moderate temperature and moderate pressure gases.

10. The gas turbine engine of claim 8 and further comprising: second extracting means associated with the power turbine for extracting additional energy from the gases with the power turbine.

11. The gas turbine engine of claim 7 and further comprising: a shaft connected between the high pressure turbine and the power turbine.

12. The gas turbine engine of claim 7 wherein the cycle efficiency of the gas turbine engine relative to either simple cycles or conventional regeneration schemes is improved.

13. The gas turbine engine of claim 7 wherein the gas turbine engine is utilized in a combined cycle.

14. The gas turbine engine of claim 7 wherein the gas turbine engine is utilized in a cogeneration cycle.