Similitude, or similarity concept, is an essential concept in turbomachinery to allow the designer to scale a turbine design to different sizes or different working fluids without repeating the whole design and development process. Similarity concept allows the testing of a turbomachine in a simple air test bench instead of a full-scale organic Rankine cycle (ORC) test bench. The concept can be further applied to adapt an existing gas turbine as an ORC turbine using different working fluids. This paper aims to scale an industrial gas turbine to different working fluids, other than the fluid the turbine was originally designed for. The turbine performance map for air was generated using the 3D computational fluid dynamics (CFD) analysis tools. Three different approaches using the similarity concept were applied to scale the turbine performance map using air and generate the performance map for two refrigerants: R134a and R245fa. The scaled performance curves derived from the air performance data were compared to the performance map generated using CFD analysis tools for R134a and R245fa. The three approaches were compared in terms of the accuracy of the performance estimation, and the most feasible approach was selected. The result shows that complete similarity cannot be achieved for the same turbomachine with two different working fluids, even at the best efficiency point for particular expansion ratio. If the constant pressure ratio is imposed, the location of the optimal velocity ratio and optimal specific speed would be underestimated with calculation error over 20%. Constant Δh0s/a012 was found to provide the highest accuracy in the performance estimation, but the expansion ratio (or pressure ratio) is varying using different working fluids due to the variation of sound speed. The differences in the fluid properties and the expansion ratio lead to the deviation in turbine performance parameters, velocity diagram, turbine's exit swirl angle, and entropy generation. The use of Δh0s/a012 further limits the application of the gas turbine for refrigerants with heavier molecular weight to a pressure ratio less than the designed pressure ratio using air. The specific speed at the best efficiency point was shifted to a higher value if higher expansion ratio was imposed. A correction chart for R245fa was attempted to estimate the turbine's performance at higher expansion ratio as a function of volumetric flow ratio.

References

References
1.
Japikse
,
D.
, and
Baines
,
N. C.
,
1995
,
Introduction to Turbomachinery
,
Concepts ETI
,
Norwich, VT
.
2.
Meher-Homji
,
C. B.
,
2000
, “
The Historical Evolution of Turbomachinery
,”
29th Turbomachinery Symposium
,
Texas A&M University
,
Houston, TX
, pp.
281
321
.
3.
Balje
,
O. E.
,
1981
,
Turbomachines: A Guide to Design Selection and Theory
,
Wiley
,
New York
.
4.
Dixon
,
S. L.
, and
Hall
,
C.
,
2010
,
Fluid Mechanics and Thermodynamics of Turbomachinery
,
Butterworth-Heinemann
,
Burlington, VT
.
5.
Chen
,
H.
, and
Baines
,
N. C.
,
1994
, “
The Aerodynamic Loading of Radial and Mixed-Flow Turbines
,”
Int. J. Mech. Sci.
,
36
(
1
), pp.
63
79
.
6.
Aungier
,
R. H.
,
2006
,
Turbine Aerodynamics: Axial-Flow and Radial-Inflow Turbine Design and Analysis
,
ASME Press
.
7.
Strub
,
R. A.
,
Bonciani
,
L.
,
Borer
,
C. J.
,
Casey
,
M. V.
,
Cole
,
S. L.
,
Cook
,
B. B.
,
Kotzur
,
J.
,
Simon
,
H.
, and
Strite
,
M. A.
,
1987
, “
Influence of the Reynolds Number on the Performance of Centrifugal Compressors
,”
ASME J. Turbomach.
,
109
(
4
), pp.
541
544
.
8.
Casey
,
M. V.
,
1985
, “
The Effects of Reynolds Number on the Efficiency of Centrifugal Compressor Stages
,”
ASME J. Eng. Gas Turbines Power
,
107
(
2
), pp.
541
548
.
9.
Quoilin
,
S.
, and
Lemort
,
V.
,
2009
, “
Technological and Economical Survey of Organic Rankine Cycle Systems
,”
5th European Conference Economis and Management of Energy in Industry
,
Algarve, Portugal
.
10.
Bao
,
J.
, and
Zhao
,
L.
,
2013
, “
A Review of Working Fluid and Expander Selections for Organic Rankine Cycle
,”
Renewable Sustainable Energy Rev.
,
24
(
8
), pp.
325
342
.
11.
Quoilin
,
S.
,
Declaye
,
S.
,
Tchanche
,
B. F.
, and
Lemort
,
V.
,
2011
, “
Thermo-Economic Optimization of Waste Heat Recovery Organic Rankine Cycles
,”
Appl. Therm. Eng.
,
31
(
14–15
), pp.
2885
2893
.
12.
Sauret
,
E.
,
2012
, “
Open Design of High Pressure Ratio Radial-Inflow Turbine for Academic Validation
,”
ASME
Paper No. IMECE2012-88315.
13.
Jones
,
A. C.
,
1996
, “
Design and Test of a Small, High Pressure Ratio Radial Turbine
,”
ASME J. Turbomach.
,
118
(
2
), pp.
362
370
.
14.
Wong
,
C. S.
, and
Krumdieck
,
S.
,
2014
, “
Energy and Exergy Analysis of an Air-Cooled Geothermal Power Plant With Fixed Nozzle Turbine in Subsonic Expansion and Supersonic Expansion Via CFD Analysis
,”
36th New Zealand Geothermal Workshop
,
Auckland University
,
Auckland, New Zealand
.
15.
Lemmon
,
E. W.
,
Huber
,
M. L.
, and
McLinden
,
M. O.
,
2013
, “
NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-refprop, Version 9.1
,”
NIST Standard Reference Database 23, Ver. 9.1, National Institute of Standards and Technology
,
Gaithersburg, MD
.
16.
Lemmon
,
E. W.
, and
Span
,
R.
,
2006
, “
Short Fundamental Equations of State for 20 Industrial Fluids
,”
J. Chem. Eng. Data
,
51
(
3
), pp.
785
850
.
17.
ASME, 1997, “Performance Test Code on Compressors and Exhausters,” PTC 10, American Society of Mechanical Engineers, New York.
18.
Pampreen
,
R.
,
1973
, “
Small Turbomachinery Compressor and Fan Aerodynamics
,”
ASME J. Eng. Gas Turbines Power
,
95
(
3
), pp.
251
256
.
19.
Harinck
,
J.
,
Guardone
,
A.
, and
Colonna
,
P.
,
2009
, “
The Influence of Molecular Complexity on Expanding Flows of Ideal and Dense Gases
,”
Phys. Fluids
,
21
(
8
), p.
086101
.
20.
Macchi
,
E.
, and
Perdichizzi
,
A.
,
1981
, “
Efficiency Prediction for Axial-Flow Turbines Operating With Nonconventional Fluids
,”
ASME J. Eng. Power
,
103
(
4
), pp.
718
724
.
21.
Angelino
,
G.
,
Invernizzi
,
C.
, and
Macchi
,
E.
,
1991
, “
Organic Working Fluid Optimization for Space Power Cycles
,”
Modern Research Topics in Aerospace Propulsion
,
G.
Angelino
,
L.
De Luca
, and
W. A.
Sirignano
, eds.,
Springer
,
New York
, pp.
297
326
.
22.
Moustapha
,
H.
,
Zelesky
,
M. F.
,
Baines
,
N. C.
, and
Japikse
,
D.
,
2003
,
Axial and Radial Turbines Part 3: Radial Turbine Design
, Concepts NREC, White River Junction, VT, pp.
197
326
.
You do not currently have access to this content.