Experimental Analysis of Film Cooling Effectiveness in Gas Turbines, Slides of Physics

Download Experimental Analysis of Film Cooling Effectiveness in Gas Turbines and more Slides Physics in PDF only on Docsity!

1

Presentation Layout

 Introduction  Film Cooling  Types of Film Cooling  Aims and objectives  Turbulence Intensity  Experimental Test Facility  Measurement Techniques  Experiment Procedure  Experiments  Summary and Conclusion  Future Recommendation

2

Cooling Techniques

 Internal convection channels  Single-crystal fabrication  Thermal barrier coatings  Film Cooling

4

Film Cooling

 Film cooling is accomplished by injecting air, from within the blade.  A thin film of cold air along the blade surface separating the blade from the hot free stream gases.  This insulating layer protects the blade from high temperatures of the hot free stream flow.  A secondary coolant flow (usually cool air from the compressor stage of the engine) is ducted through the interior of the blade and injected into the blade boundary layer through a series of holes.

5

Types of Film Cooling

Film Cooling

Stream-wise Injection Lateral Injection

7

Types of Film Cooling

Injection at an angle Injection at 90^0

8

Turbulence Intensity

 The turbulence intensity, also often referred to as turbulence level, is defined as:

Where S.D is the root-mean-square of the velocity fluctuations and is the mean velocity

10

Estimating the turbulence intensity

 High-turbulence case  High-speed flow  Between 5% and 20%  Medium-turbulence case  Flow in not-so Complex Geometry  Between 1% and 5%  Low-turbulence case  Low flow case  Very low, well below 1%

11

Re-Modeling of Test Facility

The original duct was replaced with newly compact design duct to achieve the required velocity

13

Re-Modeling of Test Facility

Original grid was replaced with new design

14

Measurements

 Thermocouple technique was used to evaluate

thermal variations

 Reasons for selecting this are

_1. Its availability

2. Simplicity in measurements
3. Wide temperature range_

 Problem with this method is that it gives data at

limited number of points

16

Measurements

Temperature at different points Digital Thermometer  MS Temp before the test section  MS Temp at the test section  Surface Temp near the hole  Coolant Temp before the test section  Coolant Temp after the test section when it mix with MS

17

Measurements

Measurement of Turbulence Intensity:

Length of Grid

width

Velocity measurement in front of Turbulence Grid

19

7

8

9

10

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Velocity (Y

- Axis

)

Z-Axis

Velocity Variation

Turbulence Generating Grid

20