Application of a heat resistant plastic in a high-speed
microturbine designed for the domestic ORC system
Grzegorz Żywica
Tomasz Z. Kaczmarczyk
Eugeniusz Ihnatowicz
Paweł Bagiński
Artur Andrearczyk
ORC 2019
Institute of Fluid Flow Machinery, Polish Academy of Sciences
Centre of Mechanics of Machines
Department of Turbine Dynamics and Diagnostics
9-11 September 2019, Athens, Greece
5th International Seminar on ORC Power Systems
Content of presentation
• Introduction
• Object of investigation
• Selection of plastic materials
• Criteria for material selection
• Thermal resistance
• Numerical analysis
• Experimental investigation
• Mechanical properties & chemical compatibility
• Machining test
• Conclusions
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
ORC turbogenerators developed at IMP PAN
Electric power: 1 kW
Rotational speed: 100,000 rpm
Weight: 8 kg
Turbogenerators are designed as oil-free units!
Maximum temperature of the working medium: 130 - 280 °C
Typical working mediums: ethanol, pentane, SES36, HFE-7100, MDM and many more
Electric power: 30 kW
Rotational speed: 15,000 rpm
Weight: 125 kg
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Domestic CHP ORC system
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Scheme of the ORC system Temperature-entropy diagram
Basic technical parameters of the ORC turbogenerator
Klonowicz et al. (2017)
Criteria for material selection
• Thermal resistance
• Chemical compatibility with the working medium
• Mechanical properties
• Thermal expansion
• Technological properties (e.g. heat treatment or machining possible)
• Resistance to erosion caused by the flow
• Lightness (low specific density)
• Availability and price of the material
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Heat-resistant plastics available on the market
Based on the PROFILEX catalogue
Selected heat-resistant plastics with working temperature above 150 °C
Based on the Ensinger catalogue
Maximum allowable temperature for long-term operation
150 °C
100 °C
300 °C
Tem
pera
ture
[°C
]
Therm
al e
xpansio
n [1
/ K
]
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Symbol Material name Density [g/cm3]Working
temperature [°C]
Temporary
temperature [°C]
PEEK Polyetherketone 1.32 250 310
PEI Polyetherimide 1.27 170 210
PFA Perfluoroalkoxy polymer 2.20 150 240
PPS Polyphenylene sulfide 1.35 240 270
PTFE Teflon 2.18 260 290
PSU Polysulfone 1.24 150 180
PVDF Polyvinylidene fluoride 1.78 150 150
Strength analysis of the rotor disc
CAD 3D model Pressure distribution
Distribution of velocity vectors
Geometry of the microturbine rotor disc
Diameter – 36 mm
Height of the turbine blade – 3 mm
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Stresses in the rotor disc at a maximum speed of 120 krpm
Strength analysis of the rotor disc
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Displacements in the rotor disc at a nominal speed
Strength analysis of the rotor disc
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Dynamic analysis of the rotor disc
Modal analysis and forced vibrations
Rotor disc Rotor with bearings
99,636 Hz
19,628 Hz
3,496 Hz
Test samples were exposed to the working mediums for a long time
Absorption of the working medium
The increase in sample dimensions did not exceed 0.5%
Time [days]
Dim
ensio
n [m
m]
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Test samples were exposed to the working mediums for a long time
Resistance to the working medium - tensile test
Test sample prepared according to the DIN EN ISO 527-2 standard (type B1)
Photo of the broken plastic sample
after the tensile test
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Results of the tensile test carried out on the dry test sample (a) and
the test sample that had been soaked in the working medium (b)
Resistance to the working medium – tensile test
Tensile tests showed that prolonged exposure to the working
medium did not change the tensile strength of the material.
The tensile strength obtained in several tests was 118 MPa.
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Machining test
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Rotor disc made of the heat-resistant plastic
Blades were made using a numerically controlled five-axis milling machine
Prototype of the rotor disc for an ORC microturbine
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece
Complete turbogenerator rotor with the rotor disk made of plastic
Test rig with the ORC microturbine
Conclusions
• The presentation discusses the problems associated with the application of modern
plastics in the production of the rotor disc of the single-stage axial microturbine with
partial admission, which was designed to be used in the domestic ORC system.
• Only a few commercially available plastics can be used for long-term operation at
temperatures above 150°C.
• When selecting the material for the ORC microturbine components, in addition to the
allowable temperature, some other technical parameters are also important, such as
chemical resistance, mechanical properties, thermal expansion.
• Strength analysis of the rotor disc and tensile tests of material samples have shown
that selected plastics can be used in ORC microturbines.
• The conducted tests and analyses have shown that modern plastics can be an
alternative to traditional construction materials – metallic alloys. The selected plastic
enabled to considerably shorten the period of time needed for machining and reduce
wear of cutting tools. As a result, the manufacturing costs were lowered.
The presented research was supported by PARP within project No. POIR.02.03.02-22-0009/15, implemented by SARK company in cooperation with the Institute of Fluid Flow Machinery (IMP PAN).
Acknowledgments
5th International Seminar on ORC Power Systems, 9-11 September 2019, Athens, Greece