Contents ........................................................ v
Nomenclature .................................................. vii
1. Introduction ................................................. 1
2. Scientific background ........................................ 3
2.1. Flow at the over-tip casing ............................. 3
2.2. Previous research into over-tip heat transfer study ..... 8
2.2.1. Work process in the tip gap ..................... 13
3. Experimental setup and measurement techniques ............... 16
3.1. The rotating cascade facility at DLR, Gottingen ........ 16
3.2. The turbine stage and measurement program .............. 17
3.3. Standard RGG instrumentation ........................... 19
3.4. Over-tip casing instrumentation ........................ 20
3.4.1. Thermocouple + array ............................ 20
3.4.2. Pressure measurement system ..................... 27
3.4.3. Hot-films ....................................... 31
3.5. Probes for wake measurements ........................... 41
3.5.1. Kulite probe .................................... 41
4. Experimental results ........................................ 46
4.1. Tip gap width .......................................... 46
4.2. Time-mean results ...................................... 47
4.2.1. Stator results .................................. 47
4.2.2. Time-mean pressure distribution ................. 49
4.2.3. Time-mean adiabatic wall temperature ............ 51
4.2.4. Time-mean heat transfer coefficient ............. 52
4.2.5. Time-mean rotor wake results .................... 55
4.3. Time-resolved results .................................. 57
4.3.1. Normalised pressure distribution ................ 57
4.3.2. Heat transfer distribution ...................... 60
4.3.3. Time-resolved wake results ...................... 61
5. Correlations of heat transfer coefficient at the over-tip
casing ...................................................... 65
5.1. Evaluation of the conventional flat plate heat
transfer correlation ................................... 66
5.1.1. Introduction of Nusselt correlations for the
flat plate ...................................... 66
5.1.2. Averaged flow conditions and axial flow
direction ....................................... 66
5.1.3. Averaged flow conditions along the
streamlines ..................................... 69
5.1.4. Variable flow conditions along the
streamline ...................................... 71
5.1.5. Evaluation of the effect of the upstream
boundary conditions ............................. 73
5.1.6. Effect of stator wake angle deviation ........... 75
5.1.7. Comparison of analytical and experimental
results ......................................... 79
5.2. Influences of time-resolved phenomena .................. 84
5.2.1. Relative fluid flow angle deviation ............. 85
5.3. Tip leakage flow ....................................... 87
5.3.1. Isentropic Mach number distribution ............. 88
5.3.2. Tip leakage model ............................... 91
5.3.3. Relaminarisation of the tip leakage flow ........ 95
5.3.4. Heat transfer in the non-rotating passage
with compressible flow .......................... 96
5.3.5. Heat transfer in the rotating passage with
compressible flow .............................. 101
5.3.6. Absolute velocity components ................... 102
5.3.7. Averaged heat transfer versus tip gap heat
transfer ....................................... 104
5.3.8. Total temperature deviations caused by
the work process ............................... 105
6. Formation of the correlation ............................... 112
6.1. Correlations .......................................... 112
6.2. Basic correlation ..................................... 112
6.3. Enhanced correlation .................................. 123
6.4. Complete enhanced heat transfer correlation for
the over-tip casing ................................... 124
7. Summary and conclusions .................................... 134
References .................................................... 137
List of figures ............................................... 141
List of tables ................................................ 143
APPENDIX A. Tip gap width analysis ............................ 144
APPENDIX В. Pitchwise averaged Adiabatic wall temperature ..... 147
APPENDIX С. Time-resolved static pressure ..................... 149
APPENDIX D. Time-resolved heat transfer ....................... 152
APPENDIX E. Calculation of the streamlines path ............... 154
APPENDIX F. Isentropic fluid properties ....................... 155
|
