Axial flow turbine
View Patent ↗An axial flow turbine includes in axial flow series a low pressure turbine section and a turbine exhaust system. The low pressure turbine section includes a final low pressure turbine stage having a circumferential row of static aerofoil blades followed in axial succession by a circumferential row of rotating aerofoil blades. Each aerofoil blade has a radially inner hub region and a radially outer tip region. The K value, being equal to the ratio of the throat dimension (t) to the pitch dimension (p), of each static aerofoil blade of the final low pressure turbine stage varies along the height of the static aerofoil blade, between the hub region and the tip region, according to a substantially W-shaped distribution.
1. An axial flow turbine comprising:
a low pressure turbine section; and
a turbine exhaust system in axial flow series with the low pressure turbine section, the low pressure turbine section comprising:
a final low pressure turbine stage having a circumferential row of static aerofoil blades followed in axial succession by a circumferential row of rotating aerofoil blades, each aerofoil blade having a radially inner hub region and a radially outer tip region, wherein a K value, being equal to a ratio of a throat dimension (t) to a pitch dimension (p), of each static aerofoil blade varies along a height of the static aerofoil blade, between the hub region and the tip region, according to a substantially W-shaped distribution; and
wherein the K value of each static aerofoil blade varies along the height of the static aerofoil blade between values K stat min and K stat max according to the substantially W-shaped distributions as follows:
Fractional
Minimum
Maximum
height of fixed
K value
K value
aerofoil blade
(K stat min )
(K stat max )
0
0.423985906
0.623985906
0.080855998
0.36638664
0.56638664
0.165294716
0.303545296
0.503545296
0.255880075
0.250207381
0.450207381
0.34182611
0.292337117
0.492337117
0.4154889
0.327357863
0.527357863
0.480483625
0.358649554
0.558649554
0.541802843
0.343071191
0.543071191
0.604115243
0.311514359
0.511514359
0.669284849
0.276224263
0.476224263
0.738563225
0.24037955
0.44037955
0.808859552
0.245298199
0.445298199
0.875782568
0.256737999
0.456737999
0.939306658
0.268124553
0.468124553
1
0.27945616
0.47945616.
2. An axial flow turbine comprising:
a low pressure turbine section; and
a turbine exhaust system in axial flow series with the low pressure turbine section, the low pressure turbine section comprising:
a final low pressure turbine stage having a circumferential row of static aerofoil blades followed in axial succession by a circumferential row of rotating aerofoil blades, each aerofoil blade having a radially inner hub region and a radially outer tip region, wherein a K value, being equal to a ratio of a throat dimension (t) to a pitch dimension (p), of each static aerofoil blade varies along a height of the static aerofoil blade, between the hub region and the tip region, according to a substantially W-shaped distribution; and
wherein an optimum K value of each static aerofoil blade K stat opt varies along the height of the static aerofoil blade according to the substantially W-shaped distribution as follows:
Fractional height
of fixed aerofoil
Optimum K value
blade
(K stat opt )
0
0.523985906
0.080855998
0.46638664
0.165294716
0.403545296
0.255880075
0.350207381
0.34182611
0.392337117
0.4154889
0.427357863
0.480483625
0.458649554
0.541802843
0.443071191
0.604115243
0.411514359
0.669284849
0.376224263
0.738563225
0.34037955
0.808859552
0.345298199
0.875782568
0.356737999
0.939306658
0.368124553
1
0.37945616.
3. An axial flow turbine comprising:
a low pressure turbine section; and
a turbine exhaust system in axial flow series with the low pressure turbine section, the low pressure turbine section comprising:
a final low pressure turbine stage having a circumferential row of static aerofoil blades followed in axial succession by a circumferential row of rotating aerofoil blades, each aerofoil blade having a radially inner hub region and a radially outer tip region, wherein a K value, being equal to a ratio of a throat dimension (t) to a pitch dimension (p), of each static aerofoil blade varies along a height of the static aerofoil blade, between the hub region and the tip region, according to a substantially W-shaped distribution; and
wherein the K value of each rotating aerofoil blade varies along the height of the rotating aerofoil blade between values K rot min and K rot max according to the distributions as follows:
Fractional height of
rotating aerofoil
Minimum K value
Maximum K Value
blade
(K rot min )
(K rot max )
0
0.533380873
0.733380873
0.09567811
0.532029303
0.732029303
0.184560236
0.52114778
0.72114778
0.26857315
0.500420225
0.700420225
0.34765811
0.456295616
0.656295616
0.422040472
0.412042865
0.612042865
0.49296063
0.364842046
0.564842046
0.561839055
0.327357863
0.527357863
0.62991252
0.292337117
0.492337117
0.697450866
0.259996808
0.459996808
0.763918976
0.232161132
0.432161132
0.826696063
0.225568154
0.425568154
0.884643622
0.212334919
0.412334919
0.94136252
0.172280247
0.372280247
1
0.130049737
0.330049737.
4. An axial flow turbine comprising:
a low pressure turbine section; and
a turbine exhaust system in axial flow series with the low pressure turbine section, the low pressure turbine section comprising:
a final low pressure turbine stage having a circumferential row of static aerofoil blades followed in axial succession by a circumferential row of rotating aerofoil blades, each aerofoil blade having a radially inner hub region and a radially outer tip region, wherein a K value, being equal to a ratio of a throat dimension (t) to a pitch dimension (p), of each static aerofoil blade varies along a height of the static aerofoil blade, between the hub region and the tip region, according to a substantially W-shaped distribution; and
wherein are optimum K value of each rotating aerofoil blade K rot opt varies along the height of the rotating aerofoil blade according to the substantially W-shaped distribution as follows:
Fractional height of
rotating aerofoil
Optimum K value
blade
(K rot opt )
0
0.633380873
0.09567811
0.632029303
0.184560236
0.62114778
0.26857315
0.600420225
0.34765811
0.556295616
0.422040472
0.512042865
0.49296063
0.464842046
0.561839055
0.427357863
0.62991252
0.392337117
0.697450866
0.359996808
0.763918976
0.332161132
0.826696063
0.325568154
0.884643622
0.312334919
0.94136252
0.272280247
1
0.230049737.
5. The axial flow turbine according to claim 1 , wherein each static aerofoil blade comprises:
a trailing edge lean angle of between 16 degrees and 25 degrees.
6. The axial flow turbine according to claim 2 , wherein each static aerofoil blade comprises:
a trailing edge lean angle of between 16 degrees and 25 degrees.
7. The axial flow turbine according to claim 5 , wherein each static aerofoil blade comprises:
a trailing edge lean angle of about 19 degrees.
8. The axial flow turbine according to claim 6 , wherein each static aerofoil blade comprises:
a trailing edge lean angle of about 19 degrees.
9. The axial flow turbine according to claim 2 , wherein each static aerofoil blade comprises:
a plurality of radially adjacent aerofoil sections stacked on a straight line along a trailing edge of the static aerofoil blade.
10. The axial flow turbine according to claim 1 , wherein the K value of each rotating aerofoil blade varies along the height of the rotating aerofoil blade between values K rot min and K rot max according to the distributions as follows:
Fractional height of
rotating aerofoil
Minimum K value
Maximum K Value
blade
(K rot min )
(K rot max )
0
0.533380873
0.733380873
0.09567811
0.532029303
0.732029303
0.184560236
0.52114778
0.72114778
0.26857315
0.500420225
0.700420225
0.34765811
0.456295616
0.656295616
0.422040472
0.412042865
0.612042865
0.49296063
0.364842046
0.564842046
0.561839055
0.327357863
0.527357863
0.62991252
0.292337117
0.492337117
0.697450866
0.259996808
0.459996808
0.763918976
0.232161132
0.432161132
0.826696063
0.225568154
0.425568154
0.884643622
0.212334919
0.412334919
0.94136252
0.172280247
0.372280247
1
0.130049737
0.330049737.
11. The axial flow turbine according to claim 2 , wherein the K value of each rotating aerofoil blade varies along the height of the rotating aerofoil blade between values K rot min and K rot max according to the distributions as follows:
Fractional height of
rotating aerofoil
Minimum K value
Maximum K Value
blade
(K rot min )
(K rot max )
0
0.533380873
0.733380873
0.09567811
0.532029303
0.732029303
0.184560236
0.52114778
0.72114778
0.26857315
0.500420225
0.700420225
0.34765811
0.456295616
0.656295616
0.422040472
0.412042865
0.612042865
0.49296063
0.364842046
0.564842046
0.561839055
0.327357863
0.527357863
0.62991252
0.292337117
0.492337117
0.697450866
0.259996808
0.459996808
0.763918976
0.232161132
0.432161132
0.826696063
0.225568154
0.425568154
0.884643622
0.212334919
0.412334919
0.94136252
0.172280247
0.372280247
1
0.130049737
0.330049737.
12. The axial flow turbine according to of claim 2 , wherein the optimum K value of each rotating aerofoil blade K rot opt varies along the height of the rotating aerofoil blade according to the distribution as follows:
Fractional height of
rotating aerofoil
Optimum K value
blade
(K rot opt )
0
0.633380873
0.09567811
0.632029303
0.184560236
0.62114778
0.26857315
0.600420225
0.34765811
0.556295616
0.422040472
0.512042865
0.49296063
0.464842046
0.561839055
0.427357863
0.62991252
0.392337117
0.697450866
0.359996808
0.763918976
0.332161132
0.826696063
0.325568154
0.884643622
0.312334919
0.94136252
0.272280247
1
0.230049737.