Rotary kinetic fluid motors or pumps – Working fluid passage or distributing means associated with... – Vane or deflector
Reexamination Certificate
2000-10-06
2002-09-10
Lopez, F. Daniel (Department: 3745)
Rotary kinetic fluid motors or pumps
Working fluid passage or distributing means associated with...
Vane or deflector
C415S211200, C415S226000
Reexamination Certificate
active
06447247
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a steam turbine with a flow duct, for steam, which extends along an axis of rotation from an inlet region to an evaporation region. The flow duct widens toward an evaporation region to an outlet opening with an outlet diameter.
A steam turbine is generally employed in a power station installation to drive a generator and for the generation of hot steam or in an industrial installation to drive a machine. For this purpose, steam used as a flow medium is supplied to the steam turbine and expands with an output of power. After complete expansion of the steam, the latter can flow via an exhaust steam casing of the steam turbine into a downstream condenser and can condense there. The flow through an appropriate exhaust steam casing can then be axial or radial.
In a power station installation for the generation of electrical power, a steam turbine installation is generally provided which has a high-pressure steam turbine, a medium-pressure steam turbine and a low-pressure steam turbine, which are connected in flow sequence. The steam expanded in the low-pressure steam turbine is supplied to a condenser and is condensed in the latter. The efficiency of such a steam turbine installation is determined by a number of parameters and, in particular, the efficiency is limited by flow resistances occurring in the steam turbine installation.
Published, European Patent Application EP 0 345 700 A1 reveals an outlet casing of a turbomachine, in particular a steam turbine, for reducing energy losses due to vortices and separations of the steam flow. The outlet casing has a circular diffuser with two separate outlet flow ducts connected to its widened end. A rear outlet flow duct, which is bounded by the rear wall of the casing, extends in a straight line and transverse to the longitudinal axis of the machine. The front outlet flow duct is guided by a bend section extending in the diffuser against the flow direction and it extends downward parallel with the rear outlet flow duct. The two flow ducts are separated from one another by a partition. In the rear outlet flow duct, an oblique rear wall extending over the complete width of the duct is disposed at the lower edge of the diffuser, which wall reaches from the diffuser to the partition. In the outlet casing disclosed in the European Patent Application EP 0 345 700 A1, the steam emerging from the steam turbine is divided into two partial steam flows which are separated from one another by a partition and are guided independently of one another into a condenser.
An appliance for removing the working fluid from axial turbines is disclosed in Published, Swiss Patent Application CH-326 301 A. In this configuration, a major part of the velocity energy of the working fluid is converted into pressure energy by an annular diffuser being fitted upstream of the working fluid removal space (exhaust steam struts) in the appliance by which the working fluid emerging from the last rotor blade row is deflected from the axial flow direction into a direction which is, on the average, radial; the working fluid deflected into the radial direction flows through the diffuser. The pressure in the last turbine stage can, therefore, be reduced to below the outlet flow pressure and, in this way, pressure losses in the outlet flow region are reduced.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a steam turbine which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which small flow losses occur.
With the foregoing and other objects in view there is provided, in accordance with the invention, a steam turbine having an axis of rotation; an inlet for receiving steam and is disposed above the axis of rotation; an exhaust steam region for conducting the steam; an outlet flow region; and a flow duct for conducting the steam and extending in a direction of the axis of rotation. The flow duct has an outlet opening with an outlet diameter. The flow duct widens toward the exhaust steam region to the outlet opening. A flow guidance element is associated with the outlet opening for conducting the steam flowing out of the outlet opening. The flow guidance element extends beyond the outlet diameter of the outlet opening and extends along an outlet flow direction into the outlet flow region. The flow guidance element widens along the outlet flow direction or has a substantially constant width, so that the steam can be guided on both sides of the flow guidance element and a thorough mixing of the steam takes place downstream of the flow guidance element.
The steam turbine has a flow duct that extends along an axis of rotation and widens (from a steam inlet region to an exhaust steam region) toward the exhaust steam region and ends with an outlet opening having an outlet diameter. The object is achieved, in accordance with the invention, by the flow guidance element, associated with the outlet opening, for conducting steam emerging from the outlet opening. The flow guidance element extends beyond the outlet diameter and, also along an outlet flow direction into an outlet flow region. The flow guidance element widens along the outlet flow direction or has an essentially constant width, so that steam can be guided on both sides of the flow guidance element and a thorough mixing of the steam takes place downstream of the flow guidance element.
The invention is based on the knowledge that at the outlet opening of the widened flow duct (axial/radial diffuser), an area-dependent static pressure is present which is larger than an area-dependent static pressure further downstream, in particular at an inlet flow plane of a condenser (condenser throat). Because of this, there is a high pressure loss, which occurs in particular due to strong eddying of the flow, which is produced by vortices. Such vortices can occur because steam from the outlet opening is, on the one hand, deflected radially downward and, on the other hand, radially upward, the steam deflected radially upward being further deflected downward and flowing along with the steam which has already been deflected downward originally. The steam initially deflected upward can be divided into two steam flows which flow downward and, in the process, swirl and respectively form a trailing vortex. The origin of these trailing vortices lies above the outer inner casing, which surrounds the flow duct.
The flow guidance element, around which emerging steam flows on both sides, preferably only extends partially in the direction of the outlet flow direction into the outlet flow region so that a mixing region is left downstream of the flow guidance element as far as the inlet flow plane of the condenser, so that an adequately thorough mixing and adequate uniformity of the total steam flow is achieved. There is, therefore, a uniform incident flow at the inlet flow plane of the condenser, which ensures low loading on the condenser.
A more uniform mass flow density distribution and a reduction in the vortex strength is made possible by the flow guidance element associated with the outlet opening, particularly in the region where the steam flowing out directly downward mixes with the steam which has been deflected from above. This configuration causes a reduction in the pressure losses during the outflow of steam from the outlet opening into the exhaust steam region and therefore contributes to an increase in the efficiency of the steam turbine. In the outlet flow region, which is formed for example between the outlet opening and the inlet flow plane of a condenser, therefore, thorough mixing of the steam flow is only achieved downstream of the flow guidance element. This thorough mixing extending to the inlet flow plane of the condenser also produces a more uniform steam flow, which leads to a uniform incident flow and uniform loading on the condenser, in particular on the condenser plates. This reduces the droplet impact loading in the condenser and increased loading due to partial steam flows
Greeneberg Laurence A.
Lopez F. Daniel
Mayback Gregory L.
McCoy Kimya N
Siemens Aktiengesellschaft
LandOfFree
Steam turbine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Steam turbine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Steam turbine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2849308