Leading edge curve for turbo engine components

The invention relates to the leading edge course for turbomachine components such as rotor and guide blades, fan blades or propellers with a partially parabolic, hyperbolic or polynomial design.

The known curved course of the leading edges of the rotor blades and guide vanes of compressors and turbines of turbomachinery, such as a gas turbine engine, is determined - without systematics - using the leading edge sweep on the basis of empirical values. The leading edge course is defined on the basis of the experience of the designer by the several radial coordinates assigned to the blade height in each case by the axial coordinate (direction of the machine axis). The leading edge course is therefore not determined by continuous mathematical functions, so that due to discontinuities (jumps) in the course of the curve, the flow at the leading edge is uneven and boundary layer detachments and flow losses can occur. Although the jumps can be ground away, the formation of the curve formed by the leading edge sweep is then no longer accurate enough. On the other hand, the lifespan of the blades is reduced due to the notch effect caused by the leading edge jumps. A systematically defined leading edge course is also suitable for systematically equalizing the profile load distribution on the rotor and guide vane cuts close to the gap, thereby increasing efficiency and stability. It is also possible to specifically reduce the high number of inflow fans at peak times and thus reduce noise emissions.

Out <patcit id="pcit0001" dnum="WO2005054633A1"><text>WO 2005/054633 A1</text></patcit> and <patcit id="pcit0002" dnum="EP0661413A1"><text>EP 0 661 413 A1</text></patcit> a leading edge course for a guide vane is known as a swept blade leading edge, which consists of a straight and a curved part, the curved part being parabolic, hyperbolic or polynomial. However, the transition from the curved to the straight part, by definition, leads to a curvature jump that has strong negative effects on the flow at the leading edge of the blade. As a mathematical fact, there is no curvature-free transition between a straight line and any polynomial of the xth degree.

The invention has for its object to provide an improved front edge course for impellers and idlers, fans or propellers of turbomachinery.

This object is achieved with the suitable curve functions of the leading edge profile indicated by the features of the characterizing part of patent claim 1.

In contrast to the previously known designs of the leading edge course, the inventive design of the leading edge course represents a shape which, by definition, has no curvature jump in its course and thereby enables a significant improvement in the flow around the blade over its entire definition range. The invention particularly discloses a leading edge course which actually runs without curvature from the blade tip to the blade root, since the courses of the curved and the straight part originate from one definition and the leading edge course is not composed of several definitions.

The invention has for its object to provide a steady, clearly defined and repeatable swept front edge course for impellers and idlers, fans or propellers of turbomachinery.

According to the invention, the object is achieved with a front edge course characterized by the features of patent claim 1.

The leading edge course is determined, on the one hand, starting from the free tip and, on the other hand, from the fixed side or hub of the turbomachine component, by the position of the leading edge in a coordinate system from the axial coordinate running in the direction of the machine axis and the radial coordinate running perpendicular to the blade height and results from the relationship at the tip of the blade <maths id="math0001" num="(Formel 1)"><math display="block"><mi mathvariant="italic">Axial cooxlinates</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo mathvariant="italic">=</mo><mfrac><mn>1</mn><mn>5</mn></mfrac><mo>⁢</mo><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo>⁢</mo><msub><mrow><mi>tan</mi><mi mathvariant="italic">Sweep</mi></mrow><mi mathvariant="italic">top</mi></msub><mo>⁢</mo><mfenced><mn>1</mn><mo mathvariant="italic">-</mo><msup><mi mathvariant="italic">e</mi><mfrac><mrow><mo mathvariant="italic">-</mo><mn>5</mn><mo>⁢</mo><mfenced><mn>100</mn><mo>%</mo><mo>-</mo><mi mathvariant="italic">Bucket height</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo></mfenced></mfenced></mrow><mrow><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced></mrow></mfrac></msup></mfenced></math><img file="EP1985802B1_D0001.tif" /></maths>and on the hub from the relationship <maths id="math0002" num="(Formel 2)"><math display="block"><mi mathvariant="italic">Axial cooxlinates</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo mathvariant="italic">=</mo><mfrac><mn>1</mn><mn>5</mn></mfrac><mo>⁢</mo><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo>⁢</mo><msub><mrow><mi>tan</mi><mi mathvariant="italic">Sweep</mi></mrow><mi mathvariant="italic">hub</mi></msub><mo>⁢</mo><mfenced><mn>1</mn><mo mathvariant="italic">-</mo><msup><mi mathvariant="italic">e</mi><mfrac><mrow><mo mathvariant="italic">-</mo><mn>5</mn><mrow><mi mathvariant="italic">Bucket height</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo></mfenced><mo mathvariant="italic">)</mo></mrow></mrow><mrow><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced></mrow></mfrac></msup></mfenced></math><img file="EP1985802B1_D0002.tif" /></maths>from which, depending on the sweep angle at the tip or hub and the radial extent of the sweep, which are specified on the basis of the operating parameters of the turbomachine, the associated axial coordinate for determining the leading edge profile is calculated in percent for the respective blade height. The extent of the sweep is the area of ​​the bucket height in percent, in which the inclination of the leading edge of 90 ° in relation to the machine axis or the axial coordinate deviates or the sweep angle is greater than 0 °. Formulas 1 and 2 apply to all extensions between 0% and 100% of the blade height and for all arrow angles deviating from 0 ° - based on the radial coordinate. The leading edge is defined clearly and repeatably and is identical for all blades with the same sweep and extension. There are no local discontinuities at the leading edge, which would negatively influence the local flow around the leading edge or would be associated with negative notch effects. A regrinding (smoothing) of the front edge can therefore be omitted. Due to the aerodynamically advantageous steady (smooth) course of the leading edge, a uniform flow without separation of the boundary layer is achieved, so that the losses are reduced and the efficiency is improved.

The invention is explained in more detail using an exemplary embodiment. In the accompanying drawing:<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic representation of the definition of the swept front edge course of a blade in a coordinate system; and</dd><dt>Fig. 2</dt><dd>three exemplary swept front edges at a free blade end with the same sweep angle, but each with a different extension of the sweep.</dd></dl>

<figref idref="f0001">Fig. 1</figref> shows a leading edge of a rotor blade for a turbomachine, which extends over the blade height from the tip to the hub, with a swept leading edge starting from the blade tip in a coordinate system with an axial coordinate (in percent of the blade height) running parallel to the axis of the turbomachine axis and perpendicular to it radial coordinate (as a percentage of the blade height).

The drawing also shows the sweep angle at the tip of the blade, that is to say the sweep, which is set here at 45 ° as an example_top and the radial extension from the blade tip in percent of the blade height. The extent of the sweep is defined as the area above the blade height in which the sweep angle (the sweep) deviates from 0 °, that is to say the inclination of the leading edge with respect to the axis of the turbomachine is not 90 °. Analog parameters are used to determine the leading edge shape starting from the hub, i.e. the sweep angle on the hub (sweep_hub) and the radial extension of the sweep starting from the hub_hub up to the sweep angle 0 °.

To determine the leading edge course, the sweep at the tip or hub is determined on the basis of empirical values, which is aerodynamically advantageous at approximately 40 °, but can also be significantly lower, for example, for reasons of strength, but usually in one area is between 20 and 40 °. Furthermore, the extension of the sweep from the tip or hub of the blade to the sweep angle 0 ° is determined. An arrow from the tip and the hub usually extends to values ​​between 40 and 60% of the blade height.

The axial coordinate (in percent) of a certain blade height (in percent of the blade height) of the leading edge profile starting from the tip results from <maths id="math0003" num="(Formel 1)"><math display="block"><mi mathvariant="italic">Axial cooxlinates</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo mathvariant="italic">=</mo><mfrac><mn>1</mn><mn>5</mn></mfrac><mo>⁢</mo><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo>⁢</mo><msub><mrow><mi>tan</mi><mi mathvariant="italic">Sweep</mi></mrow><mi mathvariant="italic">top</mi></msub><mo>⁢</mo><mfenced><mn>1</mn><mo mathvariant="italic">-</mo><msup><mi mathvariant="italic">e</mi><mfrac><mrow><mo mathvariant="italic">-</mo><mn>5</mn><mo>⁢</mo><mfenced><mn>100</mn><mo>%</mo><mo>-</mo><mi mathvariant="italic">Bucket height</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo></mfenced></mfenced></mrow><mrow><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced></mrow></mfrac></msup></mfenced></math><img file="EP1985802B1_D0003.tif" /></maths>

The front edge course on the hub is determined by <maths id="math0004" num="(Formel 2)"><math display="block"><mi mathvariant="italic">Axial cooxlinates</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo mathvariant="italic">=</mo><mfrac><mn>1</mn><mn>5</mn></mfrac><mo>⁢</mo><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced><mo>⁢</mo><msub><mrow><mi>tan</mi><mi mathvariant="italic">Sweep</mi></mrow><mi mathvariant="italic">top</mi></msub><mo>⁢</mo><mfenced><mn>1</mn><mo mathvariant="italic">-</mo><msup><mi mathvariant="italic">e</mi><mfrac><mrow><mo mathvariant="italic">-</mo><mn>5</mn><mrow><mi mathvariant="italic">Bucket height</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo></mfenced><mo mathvariant="italic">)</mo></mrow></mrow><mrow><mi mathvariant="italic">Extension</mi><mfenced open="[" close="]"><mo mathvariant="italic">%</mo><mi mathvariant="italic">Bucket height</mi></mfenced></mrow></mfrac></msup></mfenced></math><img file="EP1985802B1_D0004.tif" /></maths>

<figref idref="f0002">Fig. 2</figref> shows three different, based on Formula 1 determined - starting from the blade tip of a blade - leading edge profiles with a matching sweep of 45 °, but with a different extension, namely of 100%, 50% and 30%. By specifying these or other parameters, the respective leading edge course is clearly and repeatedly determined. In the same way, the leading edge shape starting from the hub is also determined by Formula 2 and by the arrowing and extension parameters specified on the basis of empirical values. Finally, the leading edges of other turbo machine components such as guide vanes, fan blades or propellers are also designed in this way.

The leading edge course is defined mathematically and not at random depending on the individual experience of the designer and is therefore exactly repeatable. There can be no local discontinuities in the leading edge course, so that the leading edge is aerodynamically optimal without extensive rework.