Patent Application
20130000315
The present invention involves single shaft gas turbine engines. More specifically, the present invention involves low emission single shaft gas turbine engines operable over a range of loads including full (100%) load and part load.
Gas turbine engines requiring low emissions over normal operating ranges between 100% (“full load”) and part load (e.g. about 70% of full load) can achieve this in three basic ways, all by reducing air mass flow into the combustor in order to maintain an acceptable fuel/air radio without producing excessive poisonous CO gas caused by ultra lean combustion.
First, by use of so called two shaft turbine engines having a gas generator module and a power module each with separate, rotatably independent shafts, the gas generator module is purposefully controlled to have a reduced speed and thereby automatically a reduced air mass flow at part load.
Second, single shaft turbine engines can be configured to dump a fraction of the air mass flow from the compressor overboard, upstream of the combustor, at the expense of overall efficiency, or to bypass the combustors with part of the air mass flow and re-inject it in front of the turbine, thereby conserving the energy of the compressed air.
The third way to reduce air mass flow at part load conditions is to throttle the air going into the compressor by using moveable inlet guide vanes, to direct the inlet air into a swirl in the direction of rotation of the inducer position of a centrifugal compressor or the first stage of an axial compressor.
The current invention accomplishes reduced air mass flow into the combustor aerodynamically, without inlet guide vanes by injecting air jets generally tangentially into region adjacent to the compressor inlet in the direction of rotation, see
In accordance with one aspect of the invention, apparatus is provided for reducing air mass flow in a single shaft gas turbine engine having an extended operating range including part load conditions, the gas turbine engine having a rotating air compressor with an axis of rotation, an inlet region, and an outlet region. The apparatus includes at least one nozzle positioned for injecting compressed air into the inlet region. The nozzle is oriented to direct the compressed air tangentially to, and in the same angular direction as, the direction of rotation to create a swirl in an inlet air flow to the compressor. The apparatus also includes a source of compressed air in communication with the one or more nozzles, and one or more valves operatively connected to control the flow of compressed air to the one or more nozzles. The apparatus further includes a controller operatively connected to the one or more valves to cause compressed air flow to the one or more nozzles during operation at specified part load conditions.
In accordance with another aspect of the invention, a method for reducing air mass flow in a single shaft gas turbine engine over an extended operating range including part load conditions includes creating swirl in an inlet air mass flow by controllably injecting compressed air into the compressor inlet region generally tangential to, and in the same angular direction as, the direction of rotation during operation at part load conditions.
Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as defined in the appended claims.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the exemplary embodiments of the invention illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Apparatus and methods of the present invention are intended for use with a single shaft gas turbine engine, that is, where a compressor component is driven at the same speed (RPM) as the driving turbine.
Specifically, compressor 10 shown in
While compressor 10 as depicted in
In accordance with the present invention, the apparatus for reducing air mass flow in a single shaft gas turbine engine having an extended operating range including part load conditions includes at least one nozzle positioned for injecting compressed air into the inlet region. The nozzle is oriented to direct the compressed air tangentially to, and in the same angular direction as, the direction of rotation to create a swirl in the inlet air flow to the compressor. As embodied herein and with reference to
Further in accordance with the present invention, the apparatus includes a source of compressed air in communication with one or more nozzles, one or more valves operatively connected to control the flow of compressed air to the one or more nozzles, and a controller operatively connected to the one or more valves to cause compressed air to flow to the one or more nozzles during engine operation at part load conditions.
In the depicted embodiments, compressed air is taken from compressor outlet region 28, such as from diffuser 30, and is channeled to nozzles 40 through conduits 42, which include a main conduit 44 from diffuser 30 and one or more branching conduits 46 feeding the individual nozzles 40. A single valve 48 is positioned in conduit 44, although multiple valves could be used in conduits 46. Valve 48, which may be an on-off or proportional type valve, is controlled by controller 50 having as an input a signal 52 representative of engine load. Controller 50 may be the engine controller or a separate control device.
It may be preferred to control compressed air to nozzles 40 during all or a fraction of the part load operating regime, such as e.g. in the range of from about 90% to about 70% of full load. It is anticipated that the compressed air flow rate would range from about 10% to about 15% of the compressor air mass flow rate at full load conditions in this range.
The intended effect of the compressed air injection is to create swirl in the inlet air incident on the inducer portion 26 of rotor 16. As the aspect of blades 18 typically is set to receive incoming air at a predetermined angle relative to axis 22 (generally at zero degrees), changing the angle of incidence of the incoming air via the swirl will make the compressor less efficient and thereby act to throttle the air mass flow. Nonetheless, overall operational performance over the engine part load power range is expected to improve through use of the present invention. Moreover, changing the amount of compressed air injected to achieve the desired swirl, such as by the use of a proportional valve for valve 48, may reduce the inefficiencies.
With attention to
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
