Exhaust System

Abstract

An exhaust system for a plurality of turbines. An exhaust gas outlet is positioned on each of the plurality of turbines. The exhaust gas outlet provides a way of discharging any exhaust gas produced by a turbine during operation of the turbine. A common exhaust is operatively connected to the exhaust gas outlet of each of the plurality of turbines. The common exhaust is disposed to receive any exhaust gas produced by the plurality of turbines during the operation of at least one of the turbines. A back flow damper is positioned on the exhaust gas outlet for each of the plurality of turbines. An isolation damper is disposed on the back flow damper. The isolation damper is in fluid communication with the common exhaust.

Description

CROSS REFERENCES

This application claims the benefit of provisional patent application No. 61/461,124 filed on Jan. 13, 2011.

BACKGROUND OF THE INVENTION

The present invention is an exhaust system that is used in power generating systems.

In power generating systems there are frequently several power generating devices that are coupled together to proved power for a facility. The power generating devices produce exhaust gases and it is desirable to use the exhaust gases to power other devices. Accordingly, there is a need in the industry for a common exhaust system that can combine the exhaust gases from several power generating devices and use the exhaust gases to operate or power other devices. The invention provides such an exhaust system that combines the exhaust gases to operate other devices to enhance the efficiency of the power generating system.

SUMMARY OF THE INVENTION

The present invention is directed to an exhaust system for a plurality of turbines. An exhaust gas outlet is positioned on each of the plurality of turbines. The exhaust gas outlet provides a way of discharging any exhaust gas produced by a turbine during operation of the turbine. A common exhaust is operatively connected to the exhaust gas outlet of each of the plurality of turbines. The common exhaust is disposed to receive any exhaust gas produced by the plurality of turbines during the operation of at least one of the turbines. A back flow damper is positioned on the exhaust gas outlet for each of the plurality of turbines. The back flow damper allows exhaust gas to exit the turbine and prevents fluids in the common exhaust from entering the turbine. An isolation damper is disposed on the back flow damper. The isolation damper is in fluid communication with the common exhaust. The isolation damper is operable to control fluid flow between the back flow damper and the common exhaust. A drain is positioned adjacent the isolation damper to drain any fluid that maybe present during the time that the isolation damper does not allow fluid flow from the back flow damper to the common exhaust.

The exhaust system allows the turbines to be utilized only as needed and avoids potential damage to turbines that are taken out of service.

Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plane view of the arrangement of several turbines connected to a common exhaust.

FIG. 2 is a side elevation view of the features of the exhaust outlet on a single turbine.

FIG. 3 is a side elevation view of an alternative arrangement on a single turbine for the exhaust outlet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The following describes a method and apparatus to operate a set of heat engines or turbines connected to a common exhaust line in such a way as to securely prevent damage to non-operating units by operating units.

Heat engines that produce electricity, such as turbines, also produce a hot exhaust stream. The hot exhaust stream represents useful energy. It is useful to combine the exhaust of more than one turbine into a combined stream to supply thermal energy in the form of hot exhaust gas to other equipment such as heat exchangers or absorption chillers. This apparatus and method accomplishes that combined exhaust while securely preventing damage to other heat engines connected to the common exhaust duct.

It is difficult to operate heat engines that connect to a common exhaust duct because the exhaust pressurizes the common duct and exhaust from an operating engine can be forced into a non-operating unit resulting in damage. The features of the invention will be described using turbine as the heat engines. It should be understood, however, that other heat engines can be utilized with the invention. FIG. 1 shows several turbines 7, each having an exhaust outlet 9 connected to a common exhaust duct 15. The combined exhaust in this case is used to operate a heat exchanger 19 and an absorption chiller 21.

FIG. 2 show details of the apparatus and method to prevent exhaust from an operating engine from entering a non-operating engine. The exhaust outlet 9 incorporates a back-flow damper 25 that is positioned adjacent the turbine. The back-flow damper is a passive device for preventing flow from a pressurized duct into a non-operating turbine. It consists of a flapper 27 on a hinge 29 and a seating surface 31. The flapper swings on the hinge such that it permits exhaust to exit the engine when it runs, but swings the opposite way preventing flow from a pressurized duct, such as the common exhaust 15, from entering the engine when it is not operating. The back-flow damper 25 has the advantage that it will operate with no outside manipulation when the engine starts and when it shuts down. The back-flow damper has the disadvantage that it must operate freely and closes with only the pressure of the exhaust gases in the common duct to force it closed. In practice, back-flow dampers 25 allow some leakage past the flapper when the damper is in the closed position.

An active isolation damper valve 35 with a powered operator 37 is arranged in series in the exhaust outlet 9 with the back-flow damper 25. The isolation damper valve 35 is positioned on the side of the back-flow damper that is spaced apart from the turbine 7. The active damper valve 35 is operatively connected to the common exhaust duct 15. The active damper valve forms a boundary to prevent flow from the pressurized common exhaust duct into a non-operating engine when the isolation damper valve is closed. This active damper valve has the advantage that it forms a secure boundary to prevent flow from the common exhaust duct. The active damper valve 35 has the disadvantage that it is slow to operate and the operator of the valve must have knowledge of the operating state of the heat engine. The active damper valve 35 cannot be closed if the turbine 7 is being operated as damage to the turbine could result. It also has the disadvantage that although it can seat relatively securely, it may allow slow leakage of exhaust into the exhaust outlet 9 the non-operating heat engine or turbine from a pressurized duct, such as the common exhaust 15.

A vent line 41 is positioned between the back flow damper 25 and the isolation damper 35. The vent line is arranged to allow any exhaust that may leak past the active isolation damper 35 to escape and prevent build-up of pressure in the space between the active damper valve and the passive back-flow damper. A valve 43 is positioned on the vent line 41 to allow the vent line to be open or closed. The vent line is open to the atmosphere unless the valve 43 is closed.

A drain line 45 is positioned on the side of the active damper 35 that is spaced apart from the vent line 41. The vent line is disposed to prevent condensation or rain water that may enter the duct from contact with the active damper valve 35. A valve 47 is positioned on the drain line to allow the drain line to be open or closed. The drain line is open to a floor drain or other suitable drain unless the valve 47 is closed.

In the event that a turbine 7 is off-line and other turbines that are connected to the common exhaust 15 are operating, the potential exists for problems.

In the absence of other measures, exhaust gas from the on-line turbines 7 can leak past the back-flow damper 25 into the off-line turbine. If this happens, water vapor can condense in the turbine causing damage over time. Most manufactures discourage operation in this mode as a matter of practice or require that the off-line turbines be isolated from the common duct 15 by means of inserting a blank flange if a turbine is off-line for more than a day.

The exhaust outlet leading from the off-line turbine will also cool. Moist exhaust gas from the on-line turbines will migrate into the cool exhaust outlet and condense. Over time, water may accumulate in the exhaust outlet.

The block and vent arrangement shown in FIGS. 1 and 2 avoids these problematic conditions. This arrangement consists of a back-flow damper 25 that is installed at the turbine exhaust outlet 9. A butterfly or isolation damper 35 is installed on the back-flow damper outlet. When a turbine 7 is off-line, leakage of exhaust from the common exhaust duct past the isolation damper valve 31 is vented outside through the vent line 41. Accordingly, there is little or no driving pressure to force exhaust gas past the back-flow damper and into the turbine. A drain 45 for the exhaust outlet is located as close as possible to the downstream side of the isolation damper 31. The drain allows any accumulated water to drain. The passive back flow damper 25 will open from the force of the exhaust gases produced by the operating turbine 7. The invention includes a positive interlock to assure the isolation damper 35 is opened prior to turbine start. FIG. 3 shows another embodiment of the invention where a blower 51 or other source of air under pressure is connected to the vent line 41 on the side of the valve 43 that is spaced apart from the isolation damper 35.

When a turbine 7 is off-line or not operating, clean ambient air is supplied to the space between the back flow damper 25 and the isolation damper 35 by the blower 51. The air from the blower pressurizes the space between the dampers in excess of the pressure in the turbine common exhaust duct 15 (to 12 inches of water for example). The air under pressure causes the flapper 27 of the back flow damper 25 to be held against the seating surface 31 and to close the back flow damper. This essentially closes the off-line turbine 7 from the common exhaust 15. At the same time the pressure of the air from the blower keeps exhaust gases from the common exhaust from leaking past the closed isolation damper 35 as the air from the blower is at a higher pressure than the exhaust gases in the common exhaust. Leakage of clean air may occur into the turbine or the exhaust duct, but at a small rate.

The operation of the system shown in FIG. 3 is essentially the same as the operation of the invention described with respect to FIGS. 1 and 2. The blower 51, however, should be turned off before the turbine is started.

The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims.

Claims

1. An exhaust system for a plurality of turbines comprising:

an exhaust gas outlet positioned on each of the plurality of turbines, the exhaust gas outlet providing a way of discharging any exhaust gas produced by a turbine during operation of the turbine;

a common exhaust operatively connected to the exhaust gas outlet of each of the plurality of turbines, the common exhaust disposed to receive any exhaust gas produced by the plurality of turbines during the operation of at least one of the turbines;

a back flow damper position on the exhaust gas outlet for each of the plurality of turbines, the back flow damper allowing exhaust gas to exit the turbine and preventing fluids in the common exhaust from entering the turbine;

an isolation damper disposed on the back flow damper, the isolation damper being in fluid communication with the common exhaust, the isolation damper being operable to control fluid flow between the back flow damper and the common exhaust; and

a drain positioned adjacent the isolation damper to drain any fluid that maybe present.

2. An exhaust system of claim 1 wherein a conduit is connected to the isolation damper and a valve is positioned in the conduit to control the flow of fluid through the conduit.

3. The exhaust system of claim 2 wherein the conduit is open to the atmosphere and the valve can be opened to exhaust any fluids from the common exhaust that are present in the isolation damper.

4. The exhaust system of claim 2 wherein a source of pressurized fluid is connected to the conduit whereby the valve can be opened to admit pressurized fluid to isolation damper to pressurize the isolation damper and back flow damper to a pressure greater than the pressure in the common exhaust.