Thiết kế, phân tích và tối ưu hóa ứng suất nhiệt cụm piston – xylanh của động cơ không trục khuỷu

Graduation thesis
Presentation

UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

DESIGN, THERMAL STRESS
ANALYSIS
AND OPTIMIZATION
THE PISTON AND CYLINDER
OF FREE PISTON ENGINE
USING
CATIA
Reporter:
Dang Xuan
Hoa 16145394
Tang Van Sang 16145494
Advisor: Dr. Nguyen Van Trang
1/30/2021

1


Content
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

OVERVIEW
DESIGN THE PISTON
AND CYLINDER
THERMAL STRESS
ANALYSIS
THERMAL STRESS

OPTIMIZATION
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Related Research
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

1. “Design, Analysis and Optimization of Piston using CATIA
and ANSYS” of Ch.Venkata Rajam. Aim of this article is to
Design, Analysis and optimization of piston which is lighter with
minimum cost and with less time.
2. Master’s thesis “Designing and Modeling of piston in
combustion engines” of Jaume Anguera Llort . The purpose is to
design and calculate a piston for a large two-stroke diesel engine,
simulate piston loads and temperatures in ANSYS
3. “Stress Optimization of S.I. Engine Piston” of Rahul D.
Raut, Satish Mishra. The optimization is carried out to reduce the
stress concentration on the head of the piston using Ansys.

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3


Overview of Free Piston Engine Generator
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Illustration of the free-piston engine generator

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Specifications

Parameters

Number of cylinder

2

Type of engine

2 stroke

Bore

33 mm

Stroke

28 mm

Moving mass

0.580 kg

Nominal compression
ratio

7.5/1

Fuel

gasoline

4


Finite Element Analysis (FEA)
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

FEA is a numerical technique used to solve engineering
problems with an array of physics-based calculations
Requiring to define the domain problem, material properties,
geometric properties, mesh model, boundary conditions and
the element types
Types of FEA tests:
• Structural static analysis.
• Thermal engineering analysis
• Modal analysis.
• Engineering seismic calculations.
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Design the Piston
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Parameter of Piston

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Result

6


Design the Cylinder
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Parameter of Cylinder

7/19/21

Result

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Flow chart of determination of stress
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Initial boundary
condition

Input boundary
condition to FEM
software

Modify boundary
condition

FEM thermal
stress analysis

Reference stress
of experiment

Is The error b/t
simulation and experiment
result acceptable or not

No

Yes
End
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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure: Step 1: Open filename.CATpart and apply Material

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Material Properties
 

Thermal conductivity (W/moC)
Density (kg/m3)
Specail heat (J/kgoC)
Poison’s ratio
Thermal expanse (10-6/oC)
Young’s Module (GPa)
Yield Strength (MPa)
Ultimate Tensile Strength (MPa)

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Piston material

Cylinder material

AlSi

GGG40

155

42

2700

7200

960

447

0,28

0,28

21

11

80

168,5

270

250

480

400

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure:
Step 2: Go to start -> analysis & simulation ->
generative structural analysis, choose "static analysis“

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure:
Step 3: Create a

7/19/21

"smooth virtual part“ and

"clamp“

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure: Step 4: Create a

Position
Point 1
Point 2
Point 3
Point 4
Point 5
Point 6
Point 7

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"temperature field“

100% load
122
130
195
250
158
120
108

75% load
115
126

165
196
140
115
103

50% load
110
124
146
155
125
110
100

0% load
109
120
130
125
115
105
100

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure:
Step 5: Create Mesh

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure:
Step 6: Compute the Analysis

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Procedure:
Step 7: click "von mises stress" to show the stress.

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Analysis Result of Piston

100% Load

75% Load

50% Load

0% Load

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Deformation

Deformation of Piston at 100% Load
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Thermal Stress Analysis using FEA

UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Mechanical Stress
Pmax = 4.955 MPa
 

Stress (MPa)
Deformation
(mm)
Safety factor

Thermal

Mechanical

stress

stress

145

239

0.0388

0.0621

1,86

2,01

Mechanical stress acting on piston
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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Analysis result of Cylinder
100% Load

50% Load

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75% Load

0% Load

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Thermal Stress Analysis using FEA
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

D e f o rm a t io n (m m )

Analysis result of Cylinder

0

0

0
0
0

0
0

0
0
0

0

0
0
0
0
100% Load

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75% Load

50% Load

0% Load

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Optimize Piston’s Design
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Aim of this Optimization
The goal is to obtain a piston as light as possible and to
reduce the thermal stress to the desired limit.
Safety factor >= 2
Objects in need of improvement:
 Thickness of Piston’s head
 Thickness and diameter of Piston pin boss
 Piston’s Weight

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Optimize Piston’s Design
T he r m a l St re s s (M P a )

UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Piston pin boss diameter optimization

150

145
140

130

123
120

113
110

100

90

80

8

9

9.8

Piston pin boss diameter (mm)

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Optimize Piston’s Design
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

T h e r m a l S t r e s s (M P a )

Piston pin boss thickness optimization

15 0

145

145

140
13 5
13 0

125

12 5

126

12 0
115

2

2 .5

2 .9

Piston pin boss thickness (mm)

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Optimize Piston’s Design
UNIVERSITY OF TECHNICAL EDUCATION HCMC – Academic Affair Office

Piston head optimization
Recalculation the Piston
Piston head thickness: = 3,35 mm
Radial Thickness of Ring (t1): =1,2 mm
Axial Thickness of Ring (t2): t2 = 0,7t1 t1 . Choose t2 = t1 = 1,2 mm
Width of the top land (b1): b1= tH 1,2tH Choose b1 = tH = 3,35 mm
Width of other ring lands (b2): b2= 0,75t2 t2 Choose b2 = t2 = 1,2 mm

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