Gas Turbine Heat Transfer and Cooling Technology

INTRODUCTION

• Advance gas turbines engine operate at high temperature

(12000c-14000 C) to improve thermal efficiency and power output.

As the turbine inlet temperature increases, the heat transferred to

the blades in the turbine also increased. The temperature are far

above the permissible metal temperature due to which there is a

need to cool the blades to operate without failure.

• For external cooling in in gas turbine blades, the internal coolant

air is ejected out through discrete holes or slots to provide coolant

film to protect the outside surface of the blade from hot

combustion gas for better efficiency. This is also called film

cooling.

METHODOLOGY • Inspired by the unique shape of Barchan Dunes commonly seen in desert to

prevent sand particles on the ground from been blown away by on coming

airflow.

• BDSR concept was prepared to enable the coolant stream exhausted from

coolant injection holes to stay more firmly to the surface of interest for

improved film cooling performance.

• The film cooling effectiveness measurements were performed at an iso-

thermal condition by using a Pressure Sensitive Painting (PSP). Technique

based on mass transfer analogy.

EXPERIMENTAL ANALYSIS • The film cooling effectiveness measurement were performed at an

isothermal condition by using a Pressure Sensitive Painting (PSP) technique

based on mass transfer analogy.

( = Adiabatic film cooling effectiveness

=The temperature of the main-stream

Taw is the adiabatic wall temperature of the surface under inspection, and

Tc is the hole exit temperature of the coolant stream.)

• PSP based cooling effectiveness measurement can easily eliminate the

concern and implication associated with the effects of heat conduction

through the test models on the adiabatic film cooling effectiveness

measurement.

• For PSP experiments, the interested surface is coated with a layer of

oxygen-sensitive paint. This paint consist of luminophores molecule hold

together through gas-permeable polymeric binder.

•The concentration of oxygen over the interested surface can be calculated

based on the record light intensity through a calibration procedure.

Figure 2: . Experimental setup used for film cooling effectiveness

measurements with PSP technique.

CONCLUSION • It is worth noting that the periodicity of the coolant stream were first checked in the present study, and very similar coolant coverages were observed for the all the coolant injection holes. Therefore only the measurement results behind the coolant injection holes in the middle of the test plate are shown here for conciseness. • The centreline cooling effectiveness profiles given in the present study refer to the measured film cooling effectiveness values along the centreline of the coolant injection hole, while the laterally averaged cooling effectiveness is determined by averaging the measured film cooling effectiveness spamise direction under one full period of whole spacing( i.e. in the region of -1.5 =<Z/D =<1.5) behind the coolant injection. • The PSP measurement results clearly revealed that, with the same amount of the cooling streams exhausted from the injection holes, the film cooling effectiveness over the surface of interest can be enhanced greatly by mounting the BDSR’s over the test plate especially for the test cases with relatively high coolant blowing ratios ( i.e. M =>0.85). •In comparison with those of the baseline without BDSR’s, the area emerged film cooling effectiveness over the surface of interest. It was found out to be increased by 50-100 % due to the existence of the BDSR’s (i.e., the test case with H = 0.5D, <= 0.9D) as the coolant blowing ratios being M=>0.85. In addition to the higher overall film cooling effectiveness, the coverage of the coolant streams over the surface of the interest, especially along the spamise direction, was also found to become much more uniform due the existence of BDSR’s.

RAJAT RATHOUR 1 KUNAL MALHOTRA

1 ANSHUMAN SHARMA

2 KARTIK AGARWAL

2

ASME AMITY STUDENT SECTION

(Comparison of the measured film cooling effectiveness of the present study with those of the

previous studies at the test conditions of M = 0.60, DR = 1.53, and P/D = 3.)

Figure 1: . The Sand Dumes Mechanism