university of rome “la sapienza” department of mechanics and aeronautics design of a nano-gas...

UNIVERSITY OF ROME “LA SAPIENZA”UNIVERSITY OF ROME “LA SAPIENZA”

Department of Mechanics and Aeronautics

DESIGN OF A NANO-GAS TURBINE

Thermal and Structural Analysis

Pace Francesco

WhyWhy nanoturbinenanoturbine??

Displacement of human activitiesDisplacement of human activities Increased use of mobile and stand alone devicesIncreased use of mobile and stand alone devices

Need to provide energy in discontinuos, efficient and

serviceable wayApplications:

military use (powering of equipment, aeronautic propulsion, etc.)

electro-medical equipment

telecommunication

NanoturbineNanoturbine

DESIGN

Flow,Thermal and Structural Equations

Definition ofPerformance

Tecnologicalknow-how

Hypothesis and Experience

Numerical Simulation and Test

Before my work

Preliminary Design of Impeller and Stator of

Compressor

Explanation of Mechanical, Thermal and Kinematic Characteristics

Before my work

Radial and single-stage Turbine and Compressor to limit size and to exploit the higher stage work

Materials are in primis SiC e Si3N4

The efficiency derating due to low Re are not important

Processing requires precision, simplicity and possibility of industrialization

Before my work

Before my work

Analysis of Flow and

Wing-like Profile

Turbine

(in progress)

Compressor

Software: FLUENT 6.2

Diffuser

Rotor

Shaft

Blade

Design of compressor from Fluid Analysis

Before my work

Silicon Carbide (SiC)

Before my work

Silicon Carbide (SiC)

Before my work

Goals of my work in VUT

1) Preliminary Design

2) Thermal and Structural Analysis

3) Final Design

First Part

My work in VUT

Software

Cad:

Simulation:

Goals of my work in VUT

Second Part

1) Production of model of nanoturbine

2) Mechanical Testing

My work in VUT

Compressor Analysis

1° step: Analysis with traditional methods

2° step: Analysis with FEM (Finite Element Method)

Analysis with traditional methods is important to understand and to evaluate the results of FEM Analysis

My work in VUT

Structural Loads

- Centrifugal Force

- Wing Force

- Torque on the shaft

Thermal Loads

- Heat flux by conduction from turbine

My work in VUT

Structural Loads

Centrifugal Force

Balje

My work in VUT

Wing Force

Structural Loads

My work in VUT

Torque on the shaft

Structural Loads

My work in VUT

Thermal Loads

T=550K (estimated)

My work in VUT

Structural and Thermal Loads- Centrifugal Force

- Wing Forces

- Torque on the shaft

- Heat Flux from turbine

Centrifugal Force

+

Heat flux from turbine

My work in VUT

FEM Analysis

2. Analysis of results

3. Optimization

1. Model construction

My work in VUT

Model construction

- Geometry 2D and 3D

- Material characteristics

- Type of analysis

- Quality assessment

My work in VUT

Model Construction

My work in VUT

Analysis of results

- Thermal Results

- Structural Results

- Thermo-Structural Results

My work in VUTAnalysis of results

Displacements

My work in VUTAnalysis of results

Displacements

Compression:

Differential Thermal Expansion

Traction: Centrifugal

Force

My work in VUTThermal result

Temperature Mapassumption:

300K

assumption :

850K

assumption:

1000K

My work in VUTThermal result

Temperature Map

My work in VUTThermal result

Radial Stress

-50 MPaSharp corner effect

My work in VUT

Thermal result

Tangential Stress

110 MPa

-75 MPa

-220 MPa

-50 MPa

My work in VUTThermal result

Axial Stress

-30 MPa

-90 MPa

My work in VUTStructural result

Radial Stress

-17 MPa

100 MPa

Sharp corner effect

My work in VUTStructural resultTangential Stress

150 MPa

110 MPa

80 MPa

My work in VUTStructural result

Axial Stress

100 MPa

My work in VUTStructural and Thermal

resultRadial Stress

-50 MPa

75 MPa

200 MPa

Sharp corner effect

My work in VUTStructural and Thermal

resultTangential Stress

64115 MPa

200 MPa

My work in VUTStructural and Thermal

resultAxial Stress

90 MPa

-50 MPa

-170 MPa

My work in VUTStructural and Thermal

result

Von Mises Stress (equivalent stress σe)

My work in VUTStructural and Thermal

resultVon Mises Stress

3 MPa

220 MPa

Conclusions

- The relevant loads are the centrifugal force and the differential thermal expansion

- The thermal stress depends on the thickness of the compressor disk (thermal gradient)

- In some parts of compressor the intensity of stress is high but not fatal

- The selected material (SiC) is appropriate for this technology

Possible Improvements

- New model with rounded corner to remove the high stress (in progress)

- Repeat the analysis with a finer mesh to increase resolution

- Join compressor and turbine in the same model to evaluate interactions

Thank you for your attention

Francesco Pace

franz.pace@tin.it