www.semargroup.org, www.ijser.com ISSN 9-8885 Vol.0,Issue.09 May-04, Pages:869-87 Failure Analysis of A Thin-walled CNG Cylindrical Pressure Vessel THIN ZAR THEIN HLAING, DR. HTAY HTAY WIN Dep of Mechanical Engineering, Mandalay Technological Universiy, Mandalay, Myanmar, Email: hinzarzar88@gmail.com. Dep of Mechanical Engineering, Mandalay Technological Universiy, Mandalay, Myanmar, Email: hayhayw@rediffmail.com. Absrac: The purpose of his paper is o analyse he failure of a hin walled pressure vessel subjeced o inernal pressure. The cylinder wih hin walled is assumed i is generally used as pressure vessel wih open end or closed end. The compressed naural gas (CNG)cylinder pressure vessel become imporan in (naural gas vehicle )NGV fuel driving sysem because demand in CNG base as increase. CNG pressure has four ypes made wih fully meal, hoop wrapped wih meal liner, fully wrapped wih meal liner or composie. This paper discusses he case failure analysis in ype I (CNG). The CNG vessel consruced wih AISI 40 Low alloy seel. The vessel capaciy is 50 lier and diameer 9mm and lengh is 55mm. operaing pressure is inernal pressure (0MPa). The hickness of srucure a various par of vessel is calculaed by using design equaion. Based on Hill s crierion and Von-Mises crierion, he operaing and failure pressure of he vessel are prediced. In his paper focus on, o apply hin walled (CNG) vessel wih failure heory and o preven sress relaed vessel rupure and caasrophic failure. Finie elemen analysis of hemispherical head and cylindrical shell posiion is done by using COMSOL Muliphysics. Keywords: (CNG) Pressure Vessel, Design Thickness And Sress, Numerical Simulaion, Failure Analysis, COMSOL Muliphasic. I. INTRODUCTION Pressure vessels are used in a number of indusries; for example, he power generaion indusry for fossil and nuclear power, he perochemical indusry for soring peroleum oil as well as soring gasoline in service saions, and compressed naural gas (CNG) cylinder pressure vessel. Generally speaking, pressurized equipmen is required for a wide range of indusrial plan for sorage and manufacuring purposes. The size and geomeric form of pressure vessels vary grealy from he large cylindrical vessels used for highpressure gas sorage o he small size used as hydraulic unis for aircraf and auomobile. Boh CNG and hydrogen are sored on board in cylindrical pressure vessels. In pracice, CNG pressure vessel is classified as hin wall cylinder. So, he wall hickness, is small in comparison wih he circumferenial radius of curvaure, r. If he raio r/ > 0, he cylinder is consider o be hin shell. Furher,mos shell used in vessel consrucion are hin (membrane)shell in he range0 R 500, whose imporan characerisic is ha bending sress due o exernal loads are of high inensiy only in close proximiy o he area where he load are applied. Approximae soluions of he shell heory can be applied o pressure vessels wih more complex shells. There are four ypes of pressure vessels used in he sorage of fuel gas on auomobiles. CNG cylinder - All meal. CNG cylinder - Hoop Wrapped Composie. CNG cylinder-fully Wrapped Composie wih Meal Liners. CNG4 cylinder-fully Wrapped Composie wih Non-Meallic Liners Types of pressure vessel are shown in figure. Figure. Type of CNG pressure vessel. II. BACKGROUND OF DESIGN CNG pressure vessels normally consis of four componens as shown in figure 5 based on sandards has been follow. These mehods mus be sricly in accordance wih Copyrigh @ 04 SEMAR GROUPS TECHNICAL SOCIETY. All righs reserved.
he provisions of he prevailing code. The mehods described here are in line wih he requiremens of ASME Secion VIII Div () and hence shall mee almos all he requiremens of oher codes for pressure vessel manufacure. Figure.CNG Pressure Vessel:.Shell.Head.Boom 4.Nozzle. This paper presens soluions for a cylindrical vessel wih hemispherical head and ellipsoidal boom. Final mahemaical expressions for calculaing design hickness for each par. By using hose expressions, and by connecing membrane sress heory, a mehod for deermining srengh of pressure vessels wih hemispherical heads and ellipsoidal boom, which is suiable for designing, was developed. A special compuer programmer was creaed for he applicaion of his mehod. Compuer calculaion was done on a seleced numerical example, and he analysis resuls were shown in a diagram. A. Specificaion Daa of CNG Pressure Vessel TABLE I: DESIGN PARAMETER OF CNG PRESSURE B. Design Formula of CNG Pressure Vessel pars TABLE II: RESUME OF PRESSURE FORMULA- ASME SECTION I & ASME SECTION VIII THIN ZAR THEIN HLAING, DR. HTAY HTAY WIN III. MEMBRANE STRESS ANALYSIS OF PRESSURE Sresses in he walls of pressure vessels occur due o differen ypes of loads, depending on he purpose of he vessel and on differen influences ha a vessel is subjeced o during exploiaion. Inernal pressure has he bigges influence on he amoun of sress, so all oher ypes of loads are considered o be less imporan Soluions of he shell heory equaion show ha inernal pressure which occurs in he walls of he vessel can be, under cerain condiions, deermined by principal sress heory, Von-Mises heory and sress inensiy (Trsca s heory).. Firs principal sress heory For cylindrical shell 0.6) () For hemispherical head 0.) () For ellipsoidal boom ( DK 0.) (). Second principal sress heory For cylindrical shell 0.6) (4). Third principal sress heory (5) 4. Von-Mises sress heory Y (6) 5. Sress inensiy heory Y (7) 6. Firs principal srain / E( ) (8) 7. Second principal srain / E( ) (9) 8. Third principal srain / E( ) (0) 9. Equivalen srain heory / [ ( )] () IV. CALCULATION RESULTS OF CNG PRESSURE TABLE III: RESULT TABLE OF THICKNESS FOR PRESSURE PARTS Volume.0, IssueNo.09, May-04, Pages: 869-87
Failure Analysis of A Thin-walled CNG Cylindrical Pressure Vessel TABLE.IV: RESULT TABLE OF STRESSES FOR PRESSURE PARTS To analysis he Von-Mises sress, COMSOL sofware has been used. The pressure vessel for he analysis is used naural gas wih inernal pressure 4MPa. The maerial is low alloy seel AISI 40. Figure 4 show sresses disribued in CNG pressure vessel wih inernal pressure 4MPa VI. RESULTS AND DISCUSSIONS The failure pressure of shell porion is prediced by using finie elemen analysis sofware. The failure of he srucure sars from he pressure of 4 MPa and he complee failure of he srucure occur a 8MPa. The operaing pressure of he srucure should no exceed 0MPa. These resuls are shown in able 5and figure5, and 6. TABLE V: OPERATING AND FAILURE PRESSURE OF THIN- WALLED STRUCTURE V. NUMERICAL ANALYSIS OF PRESSURE To analysis he Von-Mises sress, COMSOL sofware has been used. The pressure vessel for he analysis is used naural gas wih inernal pressure 0MPa. The maerial is low alloy seel AISI 40. Figure show sresses disribued in CNG pressure vessel wih inernal pressure 0MPa. An approximaive analyical soluion can be obained for he cylindrical pressure vessel wih COMSOL Muliphysics. Following Hill s crierion, he yielding eill occur for R0 R0 R0 R0 P [ F( ) G( ) H( ) ] () T0 T0 T0 T0 Using he model consans, F G.470 8 / Pa and 8 H 4.40 / Pa he analyical onse of yielding occurs for p=4.mpa as compared o P=4 MPa which is he resul calculaed by COMSOL. Figure shows he Von-Mises sress conours a he onse of yielding. For low alloy seel wih yield sress a 460 MPa, he yield sress is reached for P=8 MPa. Figure. Von-Mises sress disribuion of pressure vessel. Figure5. Von-Mises sress disribuion of pressure vessel Figure4. Von-Mises sress disribuion of pressure vessel (pressure 8MPa). Volume.0, IssueNo.09, May-04, Pages: 869-87
THIN ZAR THEIN HLAING, DR. HTAY HTAY WIN Figure6. Volume having reached yield sress a various pressures. Figure9.Mesh shape for vessel head. Figure7. Surface Von-Mises sress.gauss poin evaluaion (Pressure 8MPa) Figure8. Surface: Effecive plasic srain.gauss poin evaluaion (Pressure 8MPa). Surface Von-Mises sress (Gauss poin evaluaion) and Surface: Effecive plasic srains (Gauss poin evaluaion) are shown in figure 7nd 8.Mesh shapes are shown in figure 9 and 0. Figure0. Mesh shape for vessel shell VII. CONCLUSION AND RECOMMENDATIONS From his simple analysis, i can be concluded ha his vessel can failure a he inernal pressure a 8MPa. Failure occurs when he maximum sress in he par exceeds he yield srengh. In his paper he maximum sress exceeds he yield srengh a inernal pressure 4MPa. I can be seen in figure 6. Therefore failure of he srucure sars from he pressure of 4 MPa and he complee failure of he srucure occur a 8MPa. In his paper discussed failure analysis for CNG pressure vessel wih COMSOL Muliphysics. These resuls are approximaed o design limis. Nowadays, CNG o CNG4 is used in many auomobiles in many counries. Various scenarios of developmen and manufacure CNG pressure vessels have been discussed and i seems all he CNG pressure vessels (CNG- o CNG-4) had heir own advanages and disadvanages. The cos of manufacured and maerial will increased from ype- o ype-4. New soluion, manufacuring process or maerial should be used o reduce he cos bu mus follow he inernaional sandard characerisics. No only he cos bu reliabiliy and life span of ank also mus be considered o developed economical and reliable anks. In he fuure works, he simulaion works o esimae he failure analysis of various ype CNG pressure vessels by using COMOL Muliphysics or ANSYS sofware. Volume.0, IssueNo.09, May-04, Pages: 869-87
Failure Analysis of A Thin-walled CNG Cylindrical Pressure Vessel NOMENCLATURE PV Elie Sofware Mechanical Engineering Deparmen, = hickness (mm) Faculy of Indusrial Technology, Gunadarma Universiy Jl. R i = inernal radius (mm) Margonda Raya 00 Depok. = inernal pressure (MPa) [0] Farhad Nabhani*, Temilade Ladokun and Vahid Askari, = yield srengh (MPa) Reducion of Sresses in Cylindrical Pressure Vessels Using y Finie Elemen Analysis, Teesside Universiy, School of = Firs principal sress (MPa) Science and Engineering, Middlesbrough, TS BA,UK. = Second principal sress (MPa) [] Pavo Baličević,* - Dražan Kozak - Tomislav Mrčela, = Third principal sress (MPa) Srengh of Pressure Vessels wih Ellipsoidal Heads, Josip = Firs principal srain Juraj Srossmayer Universiy of Osijek, Faculy of Agriculure, Croaia, Josip Juraj Srossmayer Universiy of = Second principal srain Osijek, Mechanical Engineering Faculy in Slavonski Brod, =Third principal srain Croaia, Josip Juraj Srossmayer Universiy of Osijek, = equivalen srain Faculy of Elecrical Engineering, Croaia. = poisson s raio E = Elasic modulus (N/m ) = mass densiy (kg/m ) VIII. ACKNOWLEDGMENT The Firs of all, he auhor wishes o express his deep graiude o Dr. Myin Thein, Recor, Mandalay Technological Universiy, for his kindness and valuable permission o summi he paper for he Maser of Engineering Degree. Moreover, he auhor is paricularly inended o Dr. Ei Ei Hwe, Associae Professor and Head of Mechanical Engineering Deparmen, Mandalay Technological Universiy, for her immeasurable help hroughou his paper. Special appreciaion is exended o her supervisor Dr. Hay Hay Win, Associae Professor, Deparmen of Mandalay Technological Universiy, for her supervision, suppor, guidance and encouragemen hroughou his sudy. IX. REFERENCES [] Nice Academy, NGV Technical Training NGV Cylinders, Malaysia, 006. [] S.T. Peers, Composies Maerials and Processes, Digial Engineering Library By McGrawHill, Mounain View, California, US,004. [] B. Sachindranarayan, Sandard HandBook of Machine Design-Pressure Cylinders, Digial Engineering Library By McGrawHill, Texas, US, 004. [4] R. C. Hibbeler, Mechanics of Maerials, published by Prenice. [5] ISO 49:000: Gas cylinders High pressure cylinders for he on-board sorage of naural gas as a fuel for auomoive vehicles. Firs Ediion, 000. [6] ASME Secion VIII Div () 998 ed: Rules For Consrucion of Unfired Pressure Vessel. [7] ASME Secion VIII Div () 998 ed: Thickness of Shell under Inernal Pressure. [8] Rosli A. Bakar, Mohamad F. Ohman, Semin, Abdul R. Ismail, The Compressed Naural Gas (CNG) Cylinder Pressure Sorage Technology in Naural Gas Vehicles (NGV) Research Trends, Faculy of Mechanical Engineering, Universiy Malaysia Pahang,m_faasya@yahoo.com.my. [9] Cokorda Prapi Mahandari, Miko Sandi, Mechanical Design OPressure Vessel for Three Phase Separaor Using Volume.0, IssueNo.09, May-04, Pages: 869-87