THE CALCULUS OF LPG TOROIDAL FUEL TANK SCREWS

Transcription

1 The 3 rd Inernaional Conference on DIAGNOSIS AND PREDICTION IN MECHANICAL ENGINEERING SYSTEMS DIPRE 1 Consanin ONESCU, Nicolae POPA Universiy of Pieşi, ROMANIA mihai.boan@ugal.ro, consanin.georgescu@ugal.ro ABSTRACT The rising of gasoline price deermines he cars users o adop alernaive fuels sysems as LPG, afer he car puhase. The LPG sysems are implemened afermarke by specialized companies and he screws of he fuel ank mus resis a he fronal and laeral impac given by sandards The paper shows a calculus mehod for he LPG oroidal fuel ank screws and ighening orque in he case of car fronal impac. Keywords: LPG sysem, bol, fronal impac, ighening orque, safey coefficien. 1. INTRODUCTION Using he oroidal fuel ank supposes ha i o be locaed wihin he space ire space. In his paper on considers ha he spare ire is ouside of vehicle under he runk. rench normaive PR/RTI/3.7.1 concerning o liquefied peroleum gas (LPG) equipmen recommends ha calculus for hese sysems o be made wih a fronal acceleraion of g and laeral acceleraion of 8g o avoid he deachmen of fuel ank [1,]. The srucure of LPG sysem on a car is presened in figure 1. On considers he following fuel ank parameers: - Toroidal ank volume 5 l - Exerior diameer D = 63 mm; - Inerior diameer d = 18 mm - Empy fuel ank ma 3 kg (wih mulivalve 1, kg); - Degree of filling 8%, means 41 l - LPG densiy.55kg/l. THE BOLTS TIGHTENING TORQUE OR TOROIDAL UEL TANK The fuel ank fasening on car body is made by following elemens: - fixaion inermediary profiles (are fasening wih wo bols on car body and anoher wo bols for fuel ank) fig. - reaining sraps 3x1,5 (widh x hickne) - lange welded on fuel ank a he boom par wih 17 mm diameer and 3 mm hickne. - ixaion ring beween reaining sraps and cenral bol (fig.3). - 5 bol M1. ig. 1. The LPG sysem wih oroidal fuel ank. 1

2 The srap siffne, considering double leaning, is given by he relaion: rear 5 48EI z 48,1 1 9 k 5,8 N / mm 3 3 x l 5 (4 ) Where: b= 3 mm he srap widh, h=1,5 mm he srap hickne. So, he elasic foe is: 5, N. - fron ig.. The fixaion inermediary profiles. In he case of acceleraion wih g value, o aure ha he LPG fuel ank is correc fixed i mus have a iniial ighening foe which is capable o creae a fricion foe greaer han ineria foe. f f f (5) 1 3 i The fricion foe f1 appears beween bols and inermediary suppors, f appears beween fuel ank and car body and f3 beween fuel ank and reaining srap. To proec he fuel ank and o increase he fricion coefficien beween reaining sraps and fuel ank heses are covered by a rubber fla bel. ig. 3. The exerior LPG fuel ank fasening. The fuel ank s ma wih 8% filling from is capaciy is given by he relaion: mo m gol V GPL 54, 88 kg (1) The graviy foe can be compued as: G m o g 54,88 9, N () Considering he value of acceleraion in he case of impac by g, he ineria foe opposed o ha acceleraion is compued below: i mo a mo g 1767 N (3) The elasic foe for ensioning he reaining srap on compues considering ha he deformaion srap lengh is 5 mm and deformaion is 4 mm. In his case, on can wrie k x, where k is siffne srap and he equivalen siffne is compued for he parallel connecion (fig.4). ig.4. The foes acing on oroidal fuel ank a impac. rom he figure 4 on wries, 4 ( G) (6) i where:. 4 fricion coefficien beween inermediary suppor and rubber bel;. 15

3 fricion coefficien ank-car body;. 4 fricion coefficien ank reaining srap wih rubber bel covering. rom relaion (6) on obains: On decomposes he foe ino wo componens: y by he direcion of reaining srap which acs upon he fasening bols on he suppors and x prees on he fuel ank. i ( G) 65 N (7) 4 min In he case of fronal impac on considers as impac muliplier wih he value of. 5 [4]. Then min N or he meric screw wih d=1 mm exerior diameer, using he iniial foe compued above he ighening orque can be wrien as: M, d 4Nm (8) min 3. THE BOLT CALCULUS In he ABCD quadrilaeral he lenghs are followings (fig.5), AB=365mm; AC=BD=6mm; BC=36mm, so in he ABC riangle on obains: AC AB BC 7mm The riangle DOC is equilaeral because DO=OC=DC=36 mm so he size of he angle DOC=AOB=6. ig.6. Saic equilibrium of foes for exerior ank. On obains: 464 (1) y sin sin N 4 4 The oal ension foe which acs on he reaining srap wihin he verical porion in he saic case is: Ts y G / 4 / 4 88 N rom figure 7 on compues he dynamic reacions ino A poin a he fronal impac wih g acceleraion. ig.5. Ineria foe a fronal impac projeced on runk floor. The ineria foe projeced on AC direcion is given below: i ica 616N cos 3 (9) On considers he reaining srap as an inexensible wire and a par of he foe i ransforms in axial ension. The angle due o elasic deformaion in he cenral area of he ank is 19. ig.7. Dynamic equilibrium of foes for exerior ank. In his case, he bol from A poin is more loaded han he bol from C poin. Adding he momens from C poin on obains: i 13 ( G / / ) 36 VA 1373 N 7 The oal foe which loads he bol is given by wo componens (ighening foe and exerior foe). 3

4 Considering M1x1,75 (SR ISO 74) screw wih d 1 1, 1 mm inerior diameer and knowing he mechanical group as 8.8 on compue he yield sre c 64 N / mm. The screw ensile sre is given by relaion: sa (11) N / mm A On obains: ( G) i sd iac N cos 3 cos 6 (15) Afer he calculus relaion above members on confirms he condiion fulfillmen: 6453 N < 78 In his case, he safey coefficien is higher han he admiible coefficien: c 64 c,9. 5. THE RETAINING STRAP CALCULUS In he case of fronal impac on considers as impac muliplier wih he value of. 5. So, he axial foe which acs on he verical porion of reaining srap can be wrien as: Td VA Ts 37 N (1) The ensile sre wihin he reaining srap: Td a 1MPa for OL 5. A THE LATERAL IMPACT CALCULUS Considering a laeral impac a an acceleraion of 8g, he ineria foe in his case is compued as: i mo a mo 8g 43 N (13) rom he figure 8, wihin DOC isosceles riangle (BO=OC=6 mm) on compues he angles BOC=AOB=1. Then, ineria foe from BD direcion is: i ibd i 43N cos 6 To aure he fuel ank s non-displacemen a he laeral impac wih he 8g acceleraion, he following relaion mus be fulfilled: f f f (14) 1 3 ibd In he case of laeral impac on considers as impac muliplier wih he value of N. ig.8. Ineria foe decomposiion from laeral impac. The normal foe (fig.8) N ibd, gives he normal fricion foe which prevens he fuel ank displacemen. The fricion foes have a grea influence o preload he dynamic foes given by he impac. In he case of laeral impac on considers as impac muliplier wih he value of. rom figure 7 on compues he dynamic reacions ino A poin a he laeral impac wih 8g acceleraion. In his case, he bol from A poin is more loaded han he bol from C poin. Adding he momens from C poin on obains: i 13 ( G / / ) 36 VA 17 N 7 So, he axial foe which acs on he verical porion of reaining srap can be wrien as: T VA Ts N The ensile sre wihin he reaining srap: T a 1MPa for OL 5. A

5 6. CONCLUSIONS In conclusion, he adding of rubber bel over he meallic reaining srap has a decisive influence by increasing he fricion foe o reduce he bol loading a he fronal and laeral impac. In his case, are fulfilled he condiions of safey using of LPG sysem from fasening poin of view. Acknowledgmens The auhors wish o hank o Proecogas Sysems Company (Landi Renzo dealer and service) for i suppor REERENCES 1. Cerao Danilo, 1, The LPG inerior oroidal fuel ank fixaion calculus, Technical Repor.. Onescu C., 1, Checking of he fuel ank fixaion of LPG Sysem, Proecogas Sysems, Technical repor. 3. Gafiţanu M., 1981, Machine elemens, Par 1, Technical Pre, Buchares. 4. Buzdugan Gh., 198, Srengh of maerials, Technical Pre, Buchares. 5. Popa N., 1999, The calculus of flanges joins, Machine building, vol.51, no.4, Iaşi. 6. Popa N., Onescu C., 9, Mechanical ransmiions, Universiy of Pieşi Publishing House. 7. Onescu C., Popa N., 9, Consideraions regarding he preload foe from hreaded faseners, The 3 rd Inernaional Conference ADEMS 9, 4-5 Sepember, Cluj Napoca. 8. Onescu C., Popa N., Coeanu C.A., 11, Aspecs regarding he preloaded foe of he bols from he pipes flanges under preure and emperaure, The 4 rd Inernaional Conference ADEMS 11, 1-3 Sepember, Cluj Napoca.. 5