Research Papers: Gas Turbines: Microturbines and Small Turbomachinery

Design, Simulation, and Construction of a Test Rig for Organic Vapors

[+] Author and Article Information
Andrea Spinelli

Research Fellow
e-mail: andrea.spinelli@polimi.it

Matteo Pini

e-mail: matteo.pini@mail.polimi.it

Vincenzo Dossena

Associate Professor
e-mail: vincenzo.dossena@polimi.it

Paolo Gaetani

Associate Professor
e-mail: paolo.gaetani@polimi.it
Laboratorio di Fluidodinamica delle Macchine,
Dipartimento di Energia,
Politecnico di Milano,
via Lambruschini, 4,
20156 Milano, Italy

Francesco Casella

Assistant Professor
Dipartimento di Elettronica e Informazione,
Politecnico di Milano,
via Ponzio, 34/5,
20133 Milano, Italy
e-mail: casella@elet.polimi.it

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received February 24, 2012; final manuscript received October 2, 2012; published online March 18, 2013. Assoc. Editor: Piero Colonna.

J. Eng. Gas Turbines Power 135(4), 042304 (Mar 18, 2013) (10 pages) Paper No: GTP-12-1047; doi: 10.1115/1.4023114 History: Received February 24, 2012; Revised October 02, 2012

A blow-down wind tunnel for real-gas applications has been designed, validated by means of dynamic simulation, and then built. The facility is aimed at characterizing an organic vapor stream, representative of the expansion taking place in organic Rankine cycle (ORC) turbines, by independent measurements of pressure, temperature, and velocity. The characterization of such flows and the validation of design tools with experimental data, which are still lacking in the scientific literature, is expected to strongly benefit the performance of future ORC turbines. The investigation of flow fields within industrial ORC turbines has been strongly limited by the unavailability of calibration tunnels for real-gas operating probes, by the limited availability of plants, and by restricted access for instrumentation. As a consequence, it has been decided to design and realize a dedicated facility, in partnership with a major ORC manufacturer. The paper thoroughly discusses the design and the dynamic simulation of the apparatus, presents its final layout, and shows the facility “as built”. A straight-axis planar convergent-divergent nozzle represents the test section for early tests, but the test rig can also accommodate linear blade cascades. The facility implements a blow down operating scheme, due to high fluid density and operating temperature, which prevent continuous operation because of the prohibitive thermal power required. A wide variety of working fluids can be tested, with adjustable operating conditions up to maximum temperature and pressure of 400 °C and 50 bar, respectively. Despite the fact that the test rig operation is unsteady, the inlet nozzle pressure can be kept constant by a control valve. In order to estimate the duration of the setup and experimental phase, and to describe the time evolution of the main process variables, the dynamic plant operation, including the control system, has been simulated. Design and simulation have been performed with both lumped-parameter and 1D models, using siloxane MDM and hydrofluorocarbon R245fa as the reference working fluids, described by state-of-the-art thermodynamic models. Calculations show how experiments may last from 12 seconds up to several minutes (depending on the fluid and test pressure), while reaching the experimental conditions requires few hours, consistently with the performance of daily-based experiments. Moreover, the economic constraints have been met by the technical solutions adopted for the plant, allowing the construction of the facility.

Copyright © 2013 by ASME
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Fig. 1

Reference nozzle expansion processes in the T-s plane. MDM (a) and R245fa (b) cases.

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Fig. 2

Options for test rig continuous cycles. (a) Gas cycle. (b) Phase transition cycle.

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Fig. 3

Final layout of the TROVA

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Fig. 4

Thermodynamic cycle implemented by the TROVA

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Fig. 5

(a) Dynamic simulation model of the test. The model includes the fluid-dynamic components and the control loop. (b) Layout of the throttling and test sections of the TROVA, modeled by the test model.

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Fig. 6

Heating process. (a) Pressure trend within the HPV for cases MDM1 and R245fa; the critical pressure Pc of each fluid is also reported. (b) Wall HPV convective heat transfer coefficient at the top (BH4) and at the bottom (BH1) band heaters for the case MDM1.

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Fig. 7

(a) HPV pressure trends for MDM1 and R245fa tests. (b) Opening trend of the control valve MCV for MDM1 test.

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Fig. 8

Nozzle regimes in time. Pressure thresholds for MDM1 (a) and R245fa (b) tests.

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Fig. 9

Nozzle regimes in space. Nondimensional nozzle profile (top) and nozzle axis trend of static pressure (central) and of Mach number (bottom) for MDM1 (a) and R245fa (b) tests.

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Fig. 10

Condensation process. Temperature trend within the LPV for cases MDM1 and R245fa.

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Fig. 11

TROVA layout “as built” without (a) and with (b) the enclosing room




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