STUDIO NUMERICO SPERIMENTALE DI TuRBomacchine di · PDF filevaneless axial flow turbine. ......

Giornata di Studio sulle TURBOMACCHINE

Bergamo – 15 luglio 2016

STUDIO NUMERICO – SPERIMENTALE

DI TuRBomacchine di piccola potenza

Rodolfo Bontempo Marcello Manna Raffaele Tuccillo

Dipartimento di Ingegeria Industriale (D.I.I)Università di Napoli “Federico II”

2

Giornata di Studio sulle Turbomacchine – Bergamo, 15 Luglio 2016

Bontempo, Manna, Tuccillo, D.I.I., Napoli Studio Numerico – Sperimentale di Turbomacchine di Piccola Potenza

AbstractThe presentation deals with theoretical, numerical and experimental analysis of small sized turbomachines

• Ducted Rotors– The classical actuator disk model is improved to take into account all nonlinear flow features. It is

applied to the theoretical analysis and to the preliminary design of innovative devices like small ducted wind turbines.

• Turbochargers– The steady and unsteady behaviour of automotive turbochargers are studied my experimental

means. Some insights on the validity of the adiabatic flow assumption and on the statistical characterisation of the surge are provided.

– The analysis of turbochargers is further detailed showing the conceptual design of an innovative vaneless axial flow turbine.

– Finally, the design of a novel downstream volute for axial flow turbine is presented and discussed

• Radial flow turbine– A similarity criteria approach is used to investigate the actual possibilities of adopting a radial

flow turbine as an ORC expander. The results are validated by CFD.

• Bontempo, R., Manna, M., Solution of the flow over a non-uniform heavily loaded ducted actuator disk, Journal of Fluid Mechanics (728), pp. 163-195, 2013

• Bontempo, R., Manna, M., Performance analysis of open and ducted wind turbines, Applied Energy (136), pp. 405-416, 2014

• Bontempo, R., Manna, M., Effects of the duct thrust on the performance of ducted wind turbines, Energy (99), pp. 274-287, 2016

• Bontempo, R., Cardone, M., Manna, M., Vorraro, G., Steady and unsteady experimental analysis of a turbocharger for automotive applications, Energy Conversion and Management (99), pp. 72-80, 2015

• Cameretti M.C., Ferrara F., Gimelli A., and Tuccillo R., 2015, “Combined MGT – ORC solar –hybrid system. PART B: Component Analysis and Prime Mover Selection”, ENERGY PROCEDIA, vol. 81 (2015), pp. 379-389, doi: 10.1016/j.egypro.2015.12.107

• Cameretti M.C., Ferrara F., Gimelli A., and Tuccillo R., 2015, "Employing Micro-Turbine Components in Integrated Solar – MGT - ORC power plants", ASME paper GT2015-42572

• Conceptual design of an axial flow turbine for advanced variable geometry turbochargers, 2016 (A. Saccomanno Dissertation, Superv. R. Tuccillo, a. Pesiridis)

• Fluid-Dynamic Design of an Innovative Turbine-Volute Layout for Turbochargers, 2016 (A. Ferrara Dissertation, Superv. R. Tuccillo, a. Pesiridis)

3



References

• The nonlinear actuator disk method as applied toducted rotors

• UNINA Turbocharger Test Rig

• Conceptual design and analysis of a vaneless axial-flow turbine for turbochargers

• Design and analysis of axial flow turbine withdownstream volute for turbochargers

• Study of the ORC expander based on similaritycriteria and CFD analysis

4



Summary

The nonlinear actuator disk method as applied to ducted rotors

5

Ducted propellers Ducted Turbines

The duct improves the propulsive efficiencyThe duct prevents the occurrence of the cavitation

The duct improves the power coefficient �� (a ducted turbine can beat the Betz limit)



6

Assumptions• Stationary• Incompressible• Inviscid• Axisymmetric

• The rotor is modelled through an actuator disk

Genesis of the methodNonlinear actuator disk

Vortex Panel method

Exact solution of theflow in an implicit form

for a prescribed load distribution

A semi-analytical and iterative procedurehas been developed



7

Main advantages of the method

• The method naturally takes into account the contraction of the wake (very important for ducted and heavily loaded propellers)

• The method duly accounts for the nonlinear and mutual interaction between the duct and the rotor ⟹ the rotor and duct flow fields are strongly coupled

• Non-uniform load distributions, rotor wake rotation and ducts of general shapes can be dealt with

• Low computational cost ⟹ it is well suited to be integrated in the first stage of design systems based on the repeated analysis scheme of hierarchical type



8

Velocity contoursDuct: NACA 4415; Parabolic Load Distribution; �= �. �

Dimensionless axial velocity��/��

Dimensionless radial velocity��/��



9

Verification against CFDDuct: NACA 4415; Parabolic Load Distribution; �= �. �

SACFD



10

CPU Time evaluationDucted Wind Turbine: NACA 5415



11

Ducted Wind Turbine Versus Open Wind TurbineDuct: NACA 5415; Parabolic Load Distribution

Betz Limit

openducted



12

UNINA Turbocharger Test RigRig Layout



13

UNINA Turbocharger Test RigVI Layout



14

UNINA Turbocharger Test RigVI Layout



15

UNINA Turbocharger Test RigApplications: Steady-State Performance Maps

Compressor Map Turbine Map



16

UNINA Turbocharger Test Rig Applications: Evaluation of the heat transfer effects on the performance



17

UNINA Turbocharger Test RigApplications: Surge Characterisation

Surge N/Nref = 1

Surge N/Nref = 0.6



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Surge N/Nref = 0.6

�

��

Surge N/Nref = 1

�

��



19




• Cooperation with BrunelUniversity, London(Dr. A. Pesiridis)

20

CFD investigation

Engine 1D modelling

Preliminary design

3D design

Off-design and map generation



• Conceptual design and analysis of a vanelessaxial-flow turbine for turbochargers

21

Engine 1D modelling

0

50

100

150

0 1000 2000 3000 4000 5000 6000 7000

Engi

ne P

ower

[kW

]

Engine Speed [rpm]

Load 100%

Axial turbine

GT1548

100

150

200

250

300

0 1000 2000 3000 4000 5000 6000 7000

Engi

ne T

orqu

e [N

m]

Engine Speed [rpm]

Load 100%

Axial turbine

GT1548

Simulation at 100% of load Engine performance

0

50

100

150

0 1000 2000 3000 4000 5000 6000 7000

Engi

ne P

ower

[kW

]

Engine Speed [rpm]

Load 75%

Axial turbine

GT1548

100

150

200

250

300

0 1000 2000 3000 4000 5000 6000 7000

Engi

ne T

orqu

e [N

m]

Engine Speed [rpm]

Load 75%

Axial turbine

GT1548

Simulation at 75% of load



22

Preliminary design

Data from 1D engine simulation of a 1.6l Ford EcoBoost

Engine Speed

(max. load)

rpm 6000 5000 4000 3000 2000

Mass flow rate

kg/s 0,1140 0,1148 0,0926 0,0736 0,0446

Inlet

Total Pressure

bar 2,268 2,377 1,967 1,669 1,324

Outlet

StaticPressure

bar 1,375 1,463 1,283 1,170 1,077

Power kW 8,66 8,11 6,01 4,14 1,51

Speed rpm 137992 146199 132084 115917 87655

Inlet Total

temperature

K 1050,36 1090,40 1066,15 1040,31 1039,06



23

Preliminary design

Balje Diagram for axial turbines



24

Preliminary design

Cordier diagram



25

• Design of the volute – nozzle – axial flowrotor

Rotor: BladeGen Volute: CFturboNozzle: CFturbo

The fluid conditions at rotor inlet must be achieved by the volute – nozzle system



26

• Design of the volute – nozzle – axial flowrotor

Rotor: BladeGen Volute: CFturboNozzle: CFturboq Due to the non-

uniformity of the fluid condition at the nozzle outlet surface, a non-periodic solution iscarried out

q A MRF has beenused for stationarypart – rotorinteraction (FLUENT flow solver)



27

• Grid Size SensitivityGiornata di Studio sulle Turbomacchine – Bergamo, 15 Luglio 2016

Mesh sensitivity analysisNumber of cells CFD resluts

Case#

Stator (*10^3)

1 rotor passage (*10^3)

Total (*10^3)

η T-T[-]

η T-S[-]

Mach Number ex [-]

Tot Pressure ex [Pa]

Mass flow [kg/s]

Computational time [h]

Case 1 50 10 210 0,809 0,697 0,316 156322 0,1144 1Case 2 200 20 520 0,818 0,704 0,322 156639 0,1158 4Case 3 400 60 1360 0,823 0,701 0,327 157030 0,1154 8Case 4 500 80 1780 0,824 0,700 0,328 157128 0,1152 12Case 5 600 100 2200 0,824 0,699 0,329 157137 0,1151 15Case 6 800 160 3360 0,824 0,698 0,330 157182 0,1151 23Case 7 1000 200 4200 0,824 0,698 0,331 157233 0,1151 32

Case 1

Case 2

Case 3

Case 4Case 5 Case 6 Case 7

0,1142

0,1144

0,1146

0,1148

0,115

0,1152

0,1154

0,1156

0,1158

0,116

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Mas

s flo

w ra

te [k

g/s]

Number of cells x 103


28

CFD analysis of the fixed part

Free vortexdistribution


29

CFD analysis of the fixed part

Free vortexdistribution


Rotor CFD investigation

Results Power [W] Mass Flow [kg/s] ηT-S ηT-T

Final Turbine 11340 0,115 70.0% 82,4%

AxStream 12397 0,113 77,0% 86,0%

HUB SECTION MEAN SECTION TIP SECTION

30Bontempo, Manna, Tuccillo, D.I.I., Napoli Studio Numerico – Sperimentale di Turbomacchine di Piccola Potenza

31

0,6

0,62

0,64

0,66

0,68

0,7

0,72

0 1000 2000 3000 4000 5000 6000 7000

Tota

l-to-

stat

ic e

ffici

ency

[-]

Data at engine speed [rpm]

Engine load 75%

0,7

0,72

0,74

0,76

0,78

0,8

0,82

0,84

0 1000 2000 3000 4000 5000 6000 7000

Tota

l-to-

tota

l effi

cien

cy [-

]

Data at engine speed [rpm]

Engine load 75%

OFF DESIGN ANALYSIS

1

1,2

1,4

1,6

1,8

2

2,2

2,4

2,6

2,8

3

0,08 0,09 0,1 0,11 0,12 0,13

βT-S

Corrected mass flow [kg/s] m√(T/Tref)/((p/pref)

Tref=109 7K ; pref=2.35 bar

55008100015145022185028210032

Turbine Operating Map Engine – Turbine Matching

1,00

1,20

1,40

1,60

1,80

2,00

0 1000 2000 3000 4000 5000 6000 7000

Com

pres

sor p

ress

ure

ratio

[-]

Data at Engine Speed [rpm]

Load 75%

Axial turbine

GT1548

0

50000

100000

150000

200000

0 1000 2000 3000 4000 5000 6000 7000

Turb

ine

Spee

d [r

pm]


Load 75%

Axial turbine

GT1548



32

OFF DESIGN ANALYSIS

1

1,2

1,4

1,6

1,8

2

2,2

2,4

2,6

2,8

3

0,08 0,09 0,1 0,11 0,12 0,13

Corrected mass flow [kg/s] m√(T/Tref)/((p/pref)

Tref=109 7K ; pref=2.35 bar

55008100015145022185028210032

Turbine Operating Map

100

120

140

160

180

200

220

240

260

280

0 1000 2000 3000 4000 5000 6000 7000

Engi

ne T

orqu

e [N

m]

Engine Speed [rpm]

Load 75%

Axial turbine GT1548



33


Fluid-Dynamic Design of an Innovative Turbine-Volute Layout for Turbochargers

The solution proposed: Honeywell Axial Flow Turbine®


Cooperation with Brunel University,London (Dr. A. Pesiridis)

34


v Kinetic energy recovery

v Improved efficiency under steady and unsteady conditions due to the largely circumferential uniform flow.

v Improved transient response due the shorter flow path and less exhaust manifold and turbine volute volume between the engine and the rotor.

v Reduction of pulsating flow effects (phase shift) due to the shorter flow passage of the stator than that of a volute


35


Static Pressure Outlet Turbine [bar] 1,45 1,39

Total to Static Efficiency [%] 74,07 73,01

Blade Speed [m/s] 294,1 294,1

Isentropic Velocity [m/s] 534,72 555,17

Blade Speed Ratio [-] 0,55 0,52

Rotor Mean Diameter [mm] 38,56 37,56

Rotor Blade Height [mm] 13,41 13,47

Stator Mean Diameter [mm] 38,56 37,56

Stator Blade Height [mm] 12,05 12

Maximum Rotor Diameter[mm] 51,97 51,03

Inlet Area [mm^2] 1623,6 1588,6

Reduction of the discharge static pressure


Solidworks 3D representation

Stator Annulus

Rotor AnnulusMean Profile Tip Profile

Stator Profile, Mean

Hub Profile

36

Stator Profile, Hub Stator Profile, Tip



3D turbine representation from BladeGen

Solidworks 3D representation

37



Different Configurations

11 Stator Blades/ 12 Rotor Blades/ Increased Thickness 19 Stator Blades/20 Rotor Blades

Configuration Original New Δ%

Total To Static Efficiency [%] 70,9 74 4,18

Total To Total Efficiency [%] 85,2 82,8 2,8

Power [kW] 14,9 13 14,61

Mass Flow Rate [kg/s] 0,134 0,1136 18,58

38



Different Configurations

19 Stator Blades/20 Rotor Blades

39

MEAN



Different Configurations19 Stator Blades/20 Rotor Blades

40

HUB



The design of diffuser and volutev Isentropic Flow v Free Vortex LawvMass conservation

41

Cross Sections Calculation: Free Vortex Law



The concept of a symmetric volute

Use of two «semi-volutes» to reduce the clutter of the last sections and accomodate the radial flow exiting the diffuser

42



Streamlines in the innovative volute

43



76,5

70,73

76,59 77,19 77,38 77,675

80

77

78,7 79,29 78,73 78,73

66

68

70

72

74

76

78

80

82

1 2 3 4 5 6

%

VOLUTES

System Efficiency

Total to Static Efficiency

Different configurations of the innovative volute

44



Mesh Sensitivity of the ultimate systems

Innovative Volute System ElementsStator 105946Rotor 148990Diffuser 155678Volute 524670

Classic Volute System ElementsStator 107140Rotor 156942Diffuser 123270Volute 620345

45



Performance MapsClassic Volute Innovative Volute

��

��,��

�

��,��

��

��,��

�

��,��

�

��

��,��

��

��,��

46



47



020000400006000080000

100000120000140000160000180000

1000 3000 5000 7000

Turb

ine

Spee

d [r

pm]


Turbine with innovativevolute

Turbine with classicvolute

0

2

4

6

8

10

12

14

0 2000 4000 6000 8000

Turb

ine

Pow

er [k

W]

[rpm]Data at Engine Speed

Turbine with innovativevolute

Turbine with classic volute

11,11,21,31,41,51,61,71,81,9

2

0 2000 4000 6000 8000

Com

pres

sorP

ress

ure

Rat

io

[rpm]Data at Engine Speed

Turbine withinnovativevolute

Turbine withclassic volute

Turbine-Engine Matching

0

20

40

60

80

100

120

140

1000 2000 3000 4000 5000 6000 7000

Pow

er [k

W]

Engine speed [rpm]

Engine Power (Maximum Load)

Turbine withinnovativevoluteOriginal Turbine

160170180190200210220230240250260

1000 2000 3000 4000 5000 6000 7000To

rque

[Nm

]

Engine speed [rpm]

Engine Torque (Maximum Load)

Turbine with innovativevoluteOriginal Turbine

48



Effect of Turbine-Engine Matching

THE DOWN-SIZED RADIAL TURBINE AS AN ORC EXPANDER

• The radial flow turbine from the well consolidated technology ofdown-sized turbochargers appears to be worthy of particularattention as an effective ORC expander

• An analysis to investigate the actual possibilities of adapting theradial flow turbine to a different application:

Ø Similarity criteriaØ CFD validation

• Working Fluids considered:• R245fa• (higher molecular mass compared with air and steam) • R134a • Ammonia (lighter working fluid )

49



Reference conditions: Air expansion• Total-to-static pressure ratio

• Rotational speed

• Expected mass flow rate

50

1111

11 −−

+

−⋅

⋅

−−

=ORC

ORC

ref

ref

refref

ORC

ref

ORCORC

γγ

γ

γβ

ηη

γγ

β

ref

ORC

ef

ORC

ORC

refrefORC T

Tmm

SFN

N ⋅⋅=γ

γ)()(

ORC

ref

ORC

ref

ORC

ORC

ref

refORC

pp

refmm

TT

SFmm

γγ

⋅

⋅

=)()(

2&&

The changes in both rotational speed and mass flow rate are mainly governed bythe molecular mass of the new working fluid, while the turbine pressure ratiovaries in accordance with the isentropic exponent and the isentropic efficiency



Reference Conditionsvpressure ratio = 4.1 vangular speed = 20000 rad/s.

Rotor Geometryüexternal diameter = 47.8 mm üaxial displacement = 19.9 mmü 9 swirled blades

The ORC condensing pressure was estimated at 40 °C

The use of ammonia, even if more favourablein terms of cycle efficiency thanks to its higher superheating temperature, would imply an increase in rotor speed

51

Three dimensional views of theradial flow turbine rotor

refmm && /

Operating Conditions and Properties of the several working fluids

Air R245fa R134a Ammonia

P01 (bar) 4.1 6.315 28.64 47.66T01 (K) 473 439 455 699P2 (bar) 1.013 2.52 10.17 15.55

βtt 3.17 2.19 2.39 3.07(expected) 1.0 3.01 12.18 6.84

ω (rad /s) 20000 7850 9500 29600γ 1.392 1.077 1.153 1.234

Inlet Sound Speed (m/s) 435.3 161.3 180.6 635.0

µ (Pa s) 2.62 x 10-5 1.54 x 10-5 1.91 x 10-5 2.56 x 10-5

ν (m2/s) 8.92 x 10-5 6.28 x 10-5 2.16 x 10-5 18.0 x 10-5



• Since the values of the mass flow delivered by the radial turbine shouldmeet those resulting from the energy balance of the heat recovery boilera further transformation has been also considered for this component byapplying an appropriate scaling factor (SF) according to the wellknown relationships:

52

222 ; 1 ; ORCORCORCORCORC

ORC

DHSF

Dm

DrefDSF

ωω ∝∆∝∝

=

&

For the T100-R245fa cases, a scaling factor of 1.525 was established

the C30-R134a case implied a reduction in mass flow rate that was obtained by applying a scaling factor of 0.592



53

• A simultaneous reduction of these parameters can be obtained by meansof an iterative procedure that leads to a decrease in the angular velocity(and, therefore, in the rotor flow capacity) and in the pressure ratio, inaccordance with the additional relationship:

−⋅⋅

−=∆

−γ

γ

βη

γγ

1

111

TRH



CFD analysis of the radial flow

turbine• The CFD analysis of the radial flow

rotor was carried out in a three-dimensional periodic sector of 40°with a tetrahedral mesh of 330000elements (with an average volume of1.89 x 10-2 mm3 and an average edgesize of 0.27 mm).

• Time marching solution of thetransonic flow

• Reynolds stress (7 eqs.) model for theviscous flow

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55

Averaged meridional contours of relative Mach number



• A second step of this investigation was the off-design study that isdiscussed, as an example, for the C30-R245fa case that did not requireany adjustment in terms of scaling factor.

56

Characteristic curves of the radial flow rotor (Working fluid R245fa)

It is worth-noting that the rotor appears to cover a wide range of mass flow rates, even if acceptable values of the efficiency can be found in a more restricted interval



57Relative Mach number contours at mid-span (Working fluid R245fa)



58

The MICRO GAS TURBINE CAPSTONE C30

Ø Fossil and Biogas fuelling

Ø Matching with bottoming ORC



• Micro Gas Turbine Laboratory,• Ce.S.M.A, Napoli, ITaly

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Thanks for your kind attention

Ø [email protected]





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