Optimization of Reciever Tank Thickness used in Reciprocating Air Compressor

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Optimization of Reciever Tank Thickness used in Reciprocating Air Compressor

Prof. Mihir Patel Prof. Marnish Modi

Department of Mechanical Engineering Department of Mechanical Engineering Indus University, Rancharda, Indus University, Rancharda, Ahmadabad, India Ahmadabad, India

AbstractThis technical paper presents design, and analysis of pressure vessel. High pressure rise is developed in the pressure vessel and pressure vessel has to withstand severe forces. In the design of pressure vessel safety is the primary consideration, due the potential impact of possible accident. There is real problem of industry which using 14 mm thickness plate for designing air receiver in two stage reciprocating air compressor. Thickness is optimized by using analytical method and Ansys software.

Keywords Pressure vessel, ANSYS.

I. INTRODUCTION

Tanks, vessel and pipelines that carry, store or receive flu-ids are called pressure vessel. A pressure vessel is defined as a container with a pressure differential between inside and outside. The inside pressure is usually higher than the out- side. The fluid inside the vessel may undergo a change in state as in the case of steam boiler or may combine with oth- er reagent as in the case of chemical reactor. Pressure vessel often has a combination of high pressure together with high temperature and in some cases flammable fluids or highly radioactive material. Because of such hazards it is impera- tive that the design be such that no leakage can occur. In addition vessel has to be design carefully to cope with the operating temperature and pressure[1]

An air compressor is a device that converts power (usually from an electric mo-tor, a diesel engine or a gasoline engine) into potential energy by forcing air into a smaller volume and thus increasing its pressure. The energy in the compressed air can be stored while the air remains pressurized. The energy can be used for a variety of applications, usually by utilizing the kinetic energy of the air as it is depressurized.

Double stage or two stage reciprocating air compressors consists of two cylinders. One is called low pressure cylinder and another is called high pressure cylinder.

Suction valves of high pressure cylinder opens when air pressure in high pressure side is below to the receiver pressure & air from low pressure cylinder drawn into high pressure cylinder.

  • Thin Walled Pressure Vessels

  • Thick Walled Pressure Vessels

    Design of receiver tank is based on thick walled pressure vessel, so in a Thick Walled Pressure Vessel:

  • Yield strength is a continuous function of radius.

  • Radial stress is present, in addition to hoop stress and longitudinal stress.

  • The thick walled pressure vessel requires very high tensile strength.

  • No Buckling effects which arise in thin walled pressure vessels are countered with pressure vessels having thick walls.

  • Failure points can be foreseen in thick pressure vessels. Nevertheless, the fail-ure would be along the longitudinal direction.

Finally, complete content and organizational editing before formatting. Please take note of the following items when proofreading spelling and grammar:

III. SRESSES IN THICK WALLED CYLINDERD.

Thick-wall theory is developed from the theory of elasticity which yields the state of stress as a continuous function of radius over the pressure vessel wall. The state of stress is defined relative to a convenient cylindrical coordinate system.

– Tangential Stress

– Radial Stress

– Longitudinal Stress

II. RECEIVER TANK

A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Maintaining the Integrity of the Specifications.

Based on wall thickness pressure vessels can be classified as:

Fig.1 Tangential Stress and Radial Stress Stress Equations:

p

d 2

Finite Element Analysis was done in ANSYS software.

i 1

T (K 2 1)

0

4r 2

Fig.2 shows boundary condition of vessel, it is fourth part of total vessel for that symmetric condition has been used to analysis so it can be saved computation time.

p d 2

For mashing quadratic plane element is used. Arrow

i 0

R (K 2 1) 4r2

1

[2]

indicated pressure distribution on entire surface.

In 2D analysis, plain strain condition is use, based on that strain along longitudinal direction remain constant, so instead of taking 3D vessel it can be analyzed based on 2D, so

Specification of Air Compressor:

Air Compressor

Reciprocating Type

Motor

20 HP

No. of Cylinders

2

No. of Stages

2

FAD(cfm)

32

Minimum Pressure

35 Bar

Maximum Pressure

50 Bar

Air Receiver Capacity

500 Ltr.

Air Reservoir Tank Specifications:

Material

Mild Steel

Capacity

500 ltr

Overall Length

1625 mm

Tank Diameter

610 mm

No. of Ports

6

IV MODELING

The design of receiver tank was done. So after designing, modeling of parts has been done in Pro-Engineering software.

Following Fig.1 is assembly of Air receiver.

Fig.2 Modeling of Air Receiver:

V. FEM ANALYSIS:

The finite element method is a numerical method that can be used for the accurate solution of complex engineering problems. The basic idea in the finite element method is to find the solution of a complicated problem by replacing it by a simpler one. Since the actual problem is replaced by a simpler one in finding the solution, we will be able to find only an approximate solution rather than the exact solution.

computational time can be saved.

Fig.3,4 and 5 shows Maximum Principal stress result of different thickness of 12 mm, 10mm and 14 mm.

Fig.3 Mesh Model and Boundary condition [5]

Fig.4 Maximum Principal Stress (12 mm Thickness)

Fig.5 Maximum Principal Stress (10 mm Thickness)

Fig.6 Maximum Principal Stress (14 mm Thickness)

ANSYS software calculations TABLE1:

d0 = outer diameter of vessel

  1. thickness =10 mm, K=1.033,

    T max 149.92MPa

  2. thickness =12 mm, K=1.040,

    T max 127.54MPa

  3. thickness =12 mm, K=1.048

T max 107.06MPa

Theoretical Calculation TABLE 2:

Cylinder Thickness (mm)

Stresses

Max.Principal stress (MPa)

Yield Strength (MPa)

Factor of safety

10

149.92

250

1.66

12

127.54

250

1.96

14

107.06

250

2.33

CONCLUSION:

Comparison TABLE 3

Cylinder Thickness (mm)

Stresses

ax.Principal stress (MPa)

Max.Principal stress (MPa)

Yield Strength

(MPa)

10

150.48

149.92

250

12

124.64

127.54

250

14

106.6

107.06

250

From table we can conclude that software and theoretical result match with each other and it is below yield strength of material.

By taking factor of safety 2 we can select 12 mm thickness plate for making of receiver tank of air compressor, so that we can reduce thickness from 14 mm to 12 mm.

REFERENCES

  1. Dennis Moss, Pressure vessel design manual

  2. Farazdak Haideri, Mechanical System Design, 3rd ed, Nirali Prakashan,2012, pp. 1-126.

    Cylinder Thickness (mm)

    Stresses

    Max.Principal stress (MPa)

    Yield Strength (MPa)

    Factor of safety

    10

    150.48

    250

    1.66

    12

    124.64

    250

    2.01

    14

    106.6

    250

    2.31

  3. M.Madhavi, R Venkat Predicting Structural Brhaviar of filament wound composite pressure vessel using three dimentional shell

    Theoretical Calculation:

    Maximum Principal Stress is given by the following equation:

    analysis Springer 2014, pp. 41-50

  4. S.Ghokhale,S.Deshpande, Practicle Finite Element Analysis, 1st Finite to Infinite, 2008.

  5. ANSYS 15.

ed.

p

d 2

T

T max

i 1 (K 2 1)

K 2 1

pi K 2 1

,

0

4r 2

K d0

di

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