2008/10/30

GBT 15469-1995 反击式水轮机空蚀评定 英文版

GBT 15469-1995 反击式水轮机空蚀评定 英文版
GBT 15469-1995 反击式水轮机空蚀评定 英文版



1 Subject content and scope of application

This standard specifies evaluation condition, measuring method and evaluation method of hydraulic turbine cavitation pitting, and also offers guaranteed amount of cavitation pitting.

This standard is applicable to reaction hydraulic turbine whose single-machine capacity is larger than 10 MW or whose mixed-flow runner nominal diameter is larger than or equal to 1m, axial flow runner nominal diameter is larger than or equal to 2m. It also can be taken as reference for hydraulic turbine whose capacity or diameter is less than aforesaid values.

For hydraulic turbine whose mixed-flow runner nominal diameter is larger than 6 m and axial flow runner nominal diameter is larger than 8m, its guaranteed amount of cavitation pitting can be determined separately by referring to this standard.

Hydraulic turbine may influence power, efficiency, vibration and noise of assembling unit because of cavitation, and that situation doesn't belong to scope of this evaluation.

2 Terms, signs and unit

2.1 Cavitation ("cavitation corrosion" is used in the past)

It is generic term of the situations when local pressure in flow channel drops down to critical pressure (generally approaches to evaporating pressure), gas nucleus grows into bleb and blebs accumulate, flow, split and collapse.

2.2 Cavitation pitting ("cavitation damage" is used in the past)

It refers to overflowing assembly material damages caused by cavitation

2.3 Cavitation pitting guarantee duration of operation

It refers to useful-life for amount of hydraulic turbine cavitation pitting guaranteed by supply side.

2.4 Reference duration of operation (tr)

It refers to operation duration of guaranteed amount of hydraulic turbine cavitation pitting, and it is specified as 8000 h in this standard.

2.5 Actual duration of operation (ta)

It refers to duration of actual operation from hydraulic turbine being brought into service to inspecting its cavitation pitting.

2.6 Upper turbine power limit for normal continuous operation (Pcu)

It refers to maximum guaranteed power value that hydraulic turbine is allowed to continuously operate at each delivery head and relevant permissible tail water elevation. (Unit: MW).

2.7 Lower turbine power limit for normal continuous operation (Pcl)

It refers to minimum guaranteed power value that hydraulic turbine is allowed to continuously operate at each delivery head and relevant permissible tail water elevation. (Unit: MW).

2.8 Upper turbine power limit for temporary abnormal operation (Ptu)

It refers to maximum power for temporary abnormal operation at each delivery head and relevant permissible tail water elevation when hydraulic turbine works above upper power limit for normal operation (Unit: MW).

2.9 Lower turbine power limit for temporary abnormal operation (Ptl)

It refers to minimum power for temporary abnormal operation at each delivery head and relevant permissible tail water elevation when hydraulic turbine works with power below lower power limit for normal operation. (Unit: MW).

2.10 Turbine normal operating range

It refers to operational area between upper turbine power limit and lower power limit for normal continuous operation. (Refer to figure 1)

2.11 High turbine load abnormal operating range

It refers to operational area between upper turbine power limit for normal continuous operation and maximum power capability. (Refer to figure 1)

2.12 Low turbine load abnormal operating range

Operational area between lower turbine power limit for normal continuous operation and no-load (refer to figure 1).

Figure 1 Sketch map of hydraulic turbine operational areas

2.13 Depth of cavitation pitted area (h)

Depth of cavitation pitting measured from original surface of base material (Unit: mm).

2.14 Cavitation pitting area (A)

Area damaged by cavitation pitting measured according to specification (Unit: cm2).

2.15 Cavitation pitting volume (V)

Volume of material removed by cavitation pitting (Unit: cm3)

2.16 Cavitation pitting mass (m)

Mass of material removed by cavitation pitting (Unit: kg),

2.17 Amount of cavitation pitting (C)

Actually measured cavitation pitting mass, depth or area (Unit: kg, mm, cm2)

2.18 Guaranteed limit of the amount of cavitation pitting (Cr)

It refers to mass, depth, or area of cavitation pitting which shall be guaranteed according to reference duration of operation. (Unit: kg, mm, cm2).

2.19 Corrected guaranteed amount of cavitation pitting (Ca)

It refers to guaranteed amount of cavitation pitting corrected according to actual runtime (Unit: kg, mm, cm2).

2.20 Guaranteed coefficient of material mass loss by cavitation pitting (Km)

It refers to cavitation pitting mass when turbine runner nominal diameter is 1 m and operates for 8000h.

2.21 Guaranteed depth coefficient of cavitation pitting (Kh)

It refers to maximum depth of cavitation pitting when turbine runner nominal diameter is 1 m and operates for 8000h.

2.22 Guaranteed area coefficient of cavitation pitting (KA)

It refers to cavitation pitting area when turbine runner nominal diameter is 1m and operates for 8000h.

2.23 Runner nominal diameter (D)

It refers to exit diameter of runner blade for mixed flow turbine; for axial flow, diagonal flow and straight-flow turbine, it refers to inside diameter of runner chamber which intersects with runner blade axle center (Unit: m).

2.24 Suction head (Hs)

It refers to height difference from cavitation reference plane to tail water elevation, as specified for hydraulic turbine (Unit: m).