Brtvljenje konusnog rastavljivog spoja visokotlačne cijevi i pumpe za izravno ubrizgavanje benzina

Malacko, Matija (2014) Brtvljenje konusnog rastavljivog spoja visokotlačne cijevi i pumpe za izravno ubrizgavanje benzina. = Sealing of conical separable joint between high pressure pipe and gasoline direct injection fuel pump. Master's thesis (Bologna) , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Vučković, Krešimir.

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Abstract (Croatian)

Brtvljenje u cjelokupnom sustavu izravnog ubrizgavanja benzina iznimno je važan aspekt u razvoju benzinskih motora. Glavni razlog tome jest postizanje SULEV (eng. Super Ultra-Low Emission Vehicle) kategorije osobnih vozila. U navedenu kategoriju spadaju vozila s izuzetno malom emisijom koja je do 90 % manja u odnosu na standardno osobno vozilo s benzinskim motorom. Ovo se odnosi i na emisiju goriva kroz rastavljive spojeve kao što je konusni spoj visokotlačne pumpe i jednog kraja te zajedničkog voda (eng. common rail) i drugog kraja visokotlačne cijevi. Dotični spoj sastoji se od: priključka s konusnom brtvenom plohom, cijevi s glavom te preklopne matice koja ih međusobno spaja. Treba istražiti utjecaj promjene materijala priključka na propuštanje spoja, kao i promjenu vrste glave cijevi. Priključak je izveden sa dvije različite vrste materijala, oba od nehrđajućeg čelika, a cijevi s dvije različite vrste glave. Jedna je hladno kovana u ukovnju a druga je tokarena i zatim tvrdo zalemljena na cijev. Prva glava zbog tehnologije izradbe ima povišenu vlačnu čvrstoću a druga upravo suprotno, zbog procesa rekristalizacije, sniženu. Dakle, ukupno postoje četiri različite kombinacije spoja. Dizajn eksperimenata (eng. Design of experiments) je proveden kako bi se ustvrdilo koji su parametri relevantni pri ispitivanju propuštanja. Istraživanjem i iskustvom u tvrtki određeni su sljedeći važni parametri: materijal priključka, glava cijevi, Rpk priključka, Rpk cijevi, kut konusa i aksijalna sila. \Nakon mjerenja propuštanja uočeno je da, općenito, kovane glave brtve, a tokarene ne. Analiza regresije rezultata ispitivanja propuštanja pokazala je da je model sa helijem dao je veću ocjenu prilagodbe od modela sa n-heptanom. U prilog tomu ide analiza distribucije reziduala, korelacija utjecaja kao i Paretov dijagram. Zbog puno niže ocjene prilagodbe, model sa n-heptanom ne može se smatrati relevantnim za ocjenu parametara brtvljenosti sustava. S Paretovog dijagrama za helij, uočeno je da najveći utjecaj na brtvljenje spoja imaju (padajućim redosljedom): vrsta glave, kut konusa, Rpk cijevi, ispitni tlak i aksijalna sila. Vrsta materijala priključka nije imala nikakav utjecaj na količinu propuštanja. Iz tablice koeficijenata regresije, može se izvesti polinom modela, i na taj način kvantificirati količinu propuštanja kao funkciju korištenih parametara.

Abstract

The tightness of fuel-flow components is an important aspect in the development of gasoline engines. In addition to the safety-related fuel leakage there is also the reduction of evaporative emissions (SULEV) in the focus of development activities. Critical in this regard is the screw joint of the high pressure pipe connecting the common rail to the high pressure pump for engines with gasoline direct injection. Named screw joint consists of: fitting, high pressure pipe ending (pipe head) and union nut which holds all components together. Task was to investigate influence of changing two different materials for same type of geometry of fitting, as well as influence of two types of pipe head. One head is produced by cold forging in a die, thus having higher strength than prior to the forging, and second one is produced by fine turning, and then it is hard soldered to the pipe. That means, that turned head pipe has lower strength than prior to the soldering, because material went through recrystallization. With investigation, main influencing factors that influence leakage tightness of the screw joint were determined: axial force, sealing seat geometry, surface quality and material properties of the sealing partners. To properly conduct leakage measurements, Design of Experiments method was used to make test plan which will give how parts need to be sorted so that one varies main influencing parameters, to later get correlation for which combination of them leakage tightness of the joint changes. Main influencing parameters to vary for leakage measurements are: fitting material, pipe head, fitting Rpk, pipe Rpk, cone angle and axial force values. Measurement of the residual clamping force was conducted. Method used was loosening torque, loosening angle with estimation of elastic origin previously done on model joints. Aim was to calculate maximum axial force applied through indent width measurement, i. e. width of plastic deformation of the contact zone. Generally, forged head pipes were mostly leak tight, while turned ones were quite the opposite. Regression of data provided that helium as test medium is better than n-heptane because of higher adjusted R2 value (goodness of fit), better distribution of residuals, as well as correlation of influences and Pareto plot with the experiment results. Most influences on the leakage rate for helium had terms (in ascending order): type of pipe head, cone angle, pipe Rpk, pressure and axial force. Fitting material does not have any influence on leakage rate. Leakage rate can be quantified as a polynomial of parameter coefficients from the regression table.

Item Type: Thesis (Master's thesis (Bologna))
Uncontrolled Keywords: brtvljenje; konusni rastavljivi spoj; visokotlačno ispitivanje propuštanja; izravno ubrizgavanje benzina; vijčani spoj.
Keywords (Croatian): high pressure screw joint; leakage tightness; high pressure pump; gasoline direct injection.
Divisions: 100 Department of Design > 120 Chair of Machine Elements
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 12:47
URI: http://repozitorij.fsb.hr/id/eprint/2769

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