DESIGN AND NUMERICAL ANALYSIS OF THE PROCESSES IN SILOXANE VAPOR DRIVEN TURBINE

A. Sebelev1, R. Scharf2, N. Zabelin1, M. Smirnov1

1Peter the Great St. Petersburg Polytechnic University; 2Leibniz University of Hannover

Aleksandr Sebelev: a.sebelev.turbo@mail.ru, www.spbstu.ru

Roland Scharf: scharf@ikw.uni-hannover.de, www.ikw.uni-hannover.de

Motivation

One of the most important questions in the designing process of a recovery plant

for waste heat recovery is the choosing of a working fluid. Nowadays the aspects of

using of various hydrocarbons, freons and alcohols in ORC are widely researched

by different authors.

Significant peculiarities in details

of the expansion process in the

ORC turbines

No investigations of the fluid flow

highlights in the siloxane vapor

driven turbines

700

1700

120

4300

3220

1030

< 300

0,09

0,03

0,01

0,00 0,00 0,00 0,00 0,00

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,10

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

GW

P

OD

P

GW

P

OD

P

GW

P

OD

P

GW

P

OD

P

GW

P

OD

P

GW

P

OD

P

GW

P

OD

P

R-141b R-22 R-123 R-143a R-227eaR-245fa MM

ODP GWP

Ngyen et al.,

2001, Pentane

Yamamoto et

al.,

2002, R123

Li et al.,

2013, R123

Klonowicz et

al., 2014,

R227ea

Fu et al.,

2015, R245fa

Wang et al.,

2010,

R245+R365mfc

0,30

0,35

0,40

0,45

0,50

0,55

0,60

0,65

0,70

2000 2004 2008 2012 2016

Modern requirements for

environment safety determine

ozone depletion potential

(ODP) and global warming

potential (GWP) as main

criteria for choosing of a

working fluid. In this case the

most promising alternatives

to different hydrocarbons,

freons and alcohols are

zeotropic mixtures and

siloxanes.

Investigation object

Subcritical ORC with

hexametyldisiloxane

320,00

370,00

420,00

470,00

520,00

570,00

0,20 0,40 0,60 0,80 1,00

Turbine

Regenerator

(hot side)

Condenser

Evaporator

s, kJ/kg

T, K

High enthalpy drop supersonic

turbine

Parameter Dimensions Value Parameter Dimensions Value

Dm mm 380 α1 deg. 7,00

n rev/min 12000 ΔLax mm 7,00

H0 kJ/kg 66,26 ΔLtc mm 0,30

G kg/s 6,86 β1 deg. 90,00

Cax/u - 1,52 Z2 - 55

ε - 0,97 l2 mm 24,75

Z1 - 7 β2* deg. 30,00

l1 mm 18,95 Ω deg. 60,00

Numerical model

Numerical model

Results

Real gas model using Aungier Redlich-Kwong equation of state and Rigid Non

Interacting Sphere model:

;)(

)(

b

Ta

cb

RTp

;

5,0

0

cT

Taa c

ccc

c b

b

ap

RTc

)(

0

;45

34

2321

0

TaTaTaTaaR

cp

2)(69,26

T

wT

420

430

439

449

458

468

477,2

0,040,20,360,520,680,841

p, МПа

1,18-1,21

1,15-1,18

1,12-1,15

1,09-1,12

1,06-1,09

1,03-1,06

1-1,03

T, K

k

Inlet, total parameters

Symmetry boundary

Nozzle Blade wheel Tip shroud

Stationary wall Outlet, static parameters

High Re k-ω SST

4 positions with

Frozen rotor interface

Progressive steps of

the initial parameters

0,70

0,75

0,80

0,85

0,90

0,95

1,00

1,05

1,10

1,15

1,20

0,0092 0,0142 0,0192

Mach

nu

mb

er

Coordinate, m

0.5 mm before

critical section

critical section

0.5 mm after

critical section

699,030 0

HG

nM BWt

The flow in the critical section is not fully supersonic. Physically, it means that the

position of real critical section changed to the downstream direction in comparison

with its design position. The velocity profile near the critical section is highly

distorted towards to the straight nozzle wall

The double-vortex structure appears in the nozzle and spreads to the bade wheel.

The hub vortex rotates clockwise and rests against the blade wheel hub. The

shroud vortex has a counterclockwise rotation and rests against the blade wheel

shroud because of the inertial forces

Hub vortex Shroud vortex

Specific shape of the shock wave after the blade wheel. The intensity of the

normal shock wave decreases from hub to shroud. Shroud vortex is

underexpanded and continues its expansion after the blade wheel

Vortices cores Boundary of vortices interaction Shock wave Tip shroud leakage

)(1,30930

kWnM

N BW