5th International Seminar on ORC power Systems - Application of … · 2019-09-24 · 5th...

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


Domestic CHP ORC system


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


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

]


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


Stresses in the rotor disc at a maximum speed of 120 krpm



Displacements in the rotor disc at a nominal speed



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]


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


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.


Machining test


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


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 - Application of … · 2019-09-24 · 5th...

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