Motoare rotative

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Transcript of Motoare rotative

  • Huu GabiCMPA

  • Tipuri de motoare rotative

    Motorul Wankel Motorul KauertzMotorul Revetec Motorul Webb

  • Funcionarea motorului WankelMotorul Wankel este un tip de motor cu ardere interna inventat de inginerul german Felix Wankel la care micarea de rotaie se obine nu printr-un mecanism biel-manivel, ci cu ajutorul unui piston rotativ de form triunghiular.Motorul Wankel este un sistem constituit din doua corpuri care se rotesc pe o axa paralela. Pistonul, numit si rotor, al motorului rotativ are forma triunghiulara. Cele trei laturi ale sale, sau fete au lungimi egale si forma convexa. Pistonul rotativ executa o miscare orbitala in interiorul statorului - o carcasa de forma ovala, usor ingustata in partea din mijloc. Cele trei capete, sau varfuri ale rotorului ating laturile peretelui carcasei in timpul miscarii orbitale, in timp ce centrul rotorului formeaza un cerc inchis. Functioneaza pe baza principiului epitrohoid, modele matematice care pot fi create in diferite moduri. Modelele epitrohoide apar atunci cand un cerc executa o miscare orbitala in jurul unui alt cerc avand raza dubla decat a sa. In cercul mai mic, care executa miscarea orbitala, este ales un punct, iar atunci cand cercul se roteste, acest punct traseaza un model. Raza cercului mai mare este egala cu distanta dintre punctul central al pistonului rotativ, in acest caz, si una dintre fetele sale.

  • Motorul Wankel av. /dezav.Avantajele motorului Wankel in comparaie cu motorul cu ardere intern cu piston, sunt compactitatea i vibraiile mai reduse. Dezavantajele acestui motor sunt randamentul mai mic, ceea ce duce la un consum de combustibil mai mare pentru aceeai putere furnizat, emisia sporit de poluai, ceea ce duce la necesitatea instalaiilor de denoxare mai complexe i uzinarea i ntreinerea pretenioase, deci mai scumpe.

  • Motorul Wankel - constructoriPrimul motor Wankel a aprut ns destul de trziu n 1957 mai exact, experimentele sale fiind ngreunate de rzboi. La acea vreme Wankel lucra n cadrul companiei germane NSU Motorenwerk, care producea motociclete. Dup ce primul motor a fost prezentat mai mult de 100 companii s-au artat interesate de achiziia acestui tip de motor. Mazda a fost prima companiei important care a preluat acest motor i au nfiinat chiar un departament dedicat pentru dezvoltarea acestui motor.

    Astfel n 1967 a aprut Mazda Cosmo primul astfel de automobil cu un motor Wankel cu dou rotoare. Acest coupe a fost la acea vreme un succes i ulterior Mazda a pus motoare rotative pe mai multe modele. Motorul Wankel a fost ns preluat i de ali constructori, dintre care amintim Daimler-Benz, Alfa Romeo, Rolls Royce, Porsche, General Motors, Suzuki i Toyota. Dei era mai compact, mai uor i necesita mai puine reparatii dect un motor normal, propulsorul Wankel i-a pierdut din popularitate n anii 1990, datorit consumului mare. Inventatorul su nu a apucat ns s vad asta decednd n 1988.

  • Motorul KauertzThis is a fine example of the scissors or pursuing-piston type of rotary engine, which has resurfaced many times. The primary vane or piston rotates at a steady speed, while the secondary vane rotates at a varying speed, opening and closing the spaces between them. This shows how the gear and crank mechanism moves one vane with respect to another as the whole assembly rotates. I think the central sun gear is fixed to the casing.

  • Motorul RevetecThe REVETEC Engine design consists of two counter-rotating trilobate? (three lobed) cams geared together, so both cams contribute to forward motion. Two bearings run along the profile of both cams (four bearings in all) and stay in contact with the cams at all times. The bearings are mounted on the underside of the two inter-connected pistons, which maintain the desired clearance throughout the stroke. The two cams rotate and raise the piston with a scissor-like action to the bearings. Once at the top of the stroke the air/fuel mixture is fired. The expanded gas then forces the bearings down the ramps of the cams spreading them apart ending the stroke. The point of maximum mechanical advantage or transfer is around 10deg ATDC (the piston moving approximately 5% of its travel) making the most of the high cylinder pressure. This compares to a conventional engine that reaches maximum mechanical advantage around 40deg ATDC. (after the piston has moved through 40% of its travel, losing valuable cylinder pressure). The effective cranking distance is determined by the length from the point of bearing contact to the centre of the output shaft (NOT the stroke). The dual bearings contact the two cams in the opposite side which cancels the side forces out. The piston assembly does not experience any side force which will reduce wear and lubrication requirements at the cylinder contact. This also reduces piston shock to a negligible amount making ceramic technology suitable. One module which comprises of a minimum of five moving components, produces six power strokes per revolution. Increasing the number of lobes on each cam to five produces ten power strokes without increasing the number of components.

  • Motorul Revetec

  • Motorul WebbThis elegant drawing shows what is believed to be the first proposal for a rotary internal-combustion engine. The combustion gases enter through the central port A, passing through stationary valve B via ports C, D, E and thus into the passages F, G in the rotating piston H, and then expanding further into the volumes I, J and K formed between the rotating piston and the swivelling "buttresses" L, M and N. At the end of expansion the gases left through exhaust ports O, P and Q, which appear to be covered by movable flaps; it is not clear how these were actuated- presumably by some sort of cam mechanism. The swivelling buttresses were held in position against the piston by external weights, which would seem to rule out all but the slowest rotational speeds. The piston goes round in a clockwise direction. In the diagram buttresses L and N are making a line "seal" against the piston, which makes leakage inevitable. Ask Felix Wankel.

  • Motorul Webb