Blade Modeling

PRELIMINARY RESUME OF ROOT CAUSE ANALYSIS AT THE

PETROCHINA HITACHI H-25 GAS TURBINE BLADE

A. COMPUTATIONAL FLUID DYNAMIC ANALYSIS 1. Blade and Nozzle Modeling and Meshing

The modeling of the blade and the nozzle is create with data from technical drawing of the turbine, and then using a blade generator feature in Ansys workbench.

Blade Geometry and Dimension

Modeling in Blade Generator

The parameter which inputted to the blade generator are:

- Blade and Nozzle Geometry

- Blade and Nozzle dimension

- Type of the machine

- The cavity space of the fluid

- Type of rotation

- Number blade sets in the machine

The next step of the modeling is defining the fluid zone in the blade and the nozzle: using the blade generator feature and then define the mesh in turbogrid feature to adapt the fluid boundary for the analysis step.

The Blade meshing of the turbogrid result

The Nozzle meshing of the turbogrid result

2. Boundary condition and the setting up the parameter of the analysis 2.1. Scenario

There are four case to modeling the condition at the blade, first is too made and assumption that connection between fluid zone of the blade and the nozzle, the connection assume as stage and a frozen rotor. Then we model it with two different configuration one blade with two nozzles and one blade with one nozzle.

Two nozzle scenario

One nozzle scenario

Scenario 1

In this scenario the blade and a nozzle is paired modeled with one blade and one Nozzle, the stage connection is use for boundary that connect the blade and the nozzle

Scenario 2

In this scenario the blade and a nozzle is paired modeled with one blade and two Nozzle, the stage connection is use for boundary that connect the blade and the nozzle

Scenario 3

In this scenario the blade and a nozzle is paired modeled with one blade and one Nozzle, the frozen rotor connection is use for boundary that connect the blade and the nozzle

Scenario 4In this scenario the blade and a nozzle is paired modeled with one blade and two Nozzle, the frozen rotor connection is use for boundary that connect the blade and the nozzle

2.2. Boundary Condition Assumption at inlet

The condition of fluid in inlet boundary is :

142 Psi

714 oF

2.3. Boundary Condition Assumption at inlet

The condition of fluid in outlet boundary is :

24.7 psi

2.4. Type of analysis

The steady state assumption is use for analysis

2.5. Work Fluid

The fluid that use as an assumption in analysis is Air (Gas Ideal)

3. Analysis result of CFD Analysis 3.1. Scenario 1

In this scenario the result is Velocity Vector

The maximum velocity of the fluid in analysis is 868.078 m/s-1

Temperature around the blade :The maximum temperature around the blade is 474.260 oC

Pressure along the blade :The maximum pressure along the blade is 1.558 MPa

Temperature along the blade :The maximum temperature along the blade is 474.260 oC

3.2. Scenario 2In this scenario the result is Velocity Vector





3.3. Scenario 3In this scenario the result is Velocity Vector



B. STATIC STRUCTURAL ANALYSIS 1. Blade and Nozzle Modeling and Meshing

The modeling of the blade create with data from technical drawing of the turbine,

2. Material Data

Material date use for the bled is Rene 95 supper alloy the physical and chemical properties of the material is listed below :

Mechanical Properties

Metric English Comments

Tensile Strength, Ultimate

240 MPa 34800 psi At Room Temperature

210 MPa @Temperature 650

°C

30500 psi @Temperature 1200

°F

Tensile Strength, Yield

180 MPa 26100 psi At Room Temperature


°C


°F

Elongation at Break 14.0 % 14.0 % At Room Temperature 10.0 %

@Temperature 650 °C

10.0 % @Temperature 1200

°F

Reduction of Area 17.0 % 17.0 % At Room Temperature 13.0 %

@Temperature 650 °C

13.0 % @Temperature 1200

°F

Creep Strength 620 MPa 89900 psi 20 Hours at 705°C; 0.2% Creep

850 MPa 123000 psi 240 Hours at 650°C; 0.2% Creep

Rupture Strength 620 MPa @Temperature 760

°C, Time 36000 sec


°F, Time 10.0 hour


°C, Time 198000 sec


°F, Time 55.0 hour

Component Elements Properties

Metric English Comments

Aluminum, Al 3.30 - 3.70 % 3.30 - 3.70 % Boron, B 0.0060 - 0.015 % 0.0060 - 0.015 % Carbon, C 0.040 - 0.090 % 0.040 - 0.090 % Chromium, Cr 12.0 - 14.0 % 12.0 - 14.0 % Cobalt, Co 7.0 - 9.0 % 7.0 - 9.0 % Molybdenum, Mo 3.30 - 3.70 % 3.30 - 3.70 % Nickel, Ni 59.325 - 65.424 % 59.325 - 65.424 % As Balance Niobium, Nb 3.30 - 3.70 % 3.30 - 3.70 %

3. Meshing Size

Size of mesh that use in this analysis is 1mm, the type of mesh is tetrahedrons.

4. Environmental Temperature

The temperature of environment simulated in Ansys is 476.068 oC

5. Load The loads uses for static analysis are:

a. Pressure; the pressure from the fluid/gas. The magnitude of the pressure is 1.558 MPa. The value is taken from the CFD result

b. Centripetal Force. The force caused from the blade that rotate in 7270 RPM

F=ρA (n2π60 )

2(r12 - r2

2

2 )

F=7783 kgm3 2.2943 × 10-4 mm2(7270rpm 2π

60 )21s2 ( 1.058 m2- 0 .954 m2

2 )F= 141.08 N

6. Restraint The support uses for the analysis is frictionless support the location of the support given in the analysis is shown in the figure below :

7. Result 7.1. Von Misses Stress

The maximum resultant stress occurs in the blade is 52.15 MPa located in the base of the blade.

7.2. Total Deformation The maximum deformation occurs in the blade is 0.073584 mm located in the tip of the blade.

7.3. Safety factor The safety factor of the blade is:

SF=σ yieldσ vm

SF= 160Mpa52.15Mpa

SF=3.07

C. CONCLUSION The preliminary conclusion of the analysis is the operating condition of the turbine is not the cause of the blade crack.

Blade Modeling

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