Modeliranje zatvaranja zaklopke i predvišanje pojave hidrauličkog udara

master's thesis

• Title (english): Modeling closing swing check valve and prediction of resulting water hammer
• Author: Gabrijel Levak
• Mentor: Ivo Džijan (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-01-22, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Nepovratni ventili primjenjuju se u raznim granama industrije kako bi spriječili povratno strujanje u cjevovodima i na taj način zaštitile osjetljive komponente kao što su pumpe ili kako bi spriječili nenamjerno pražnjenje spremnika. Idealan nepovratni ventil se zatvara u trenutku kada protok mijenja smjer. Kako se u stvarnim uvjetima često javlja povratno strujanje, pojavljuje se hidraulički udar u trenutku zatvaranja. Amplituda tlačnog vala u hidrauličkom udaru uvjetovana je brzinom povratnog strujanja u trenutku zatvaranja. Nestacionarne pojave često se simuliraju jednodimenzionalnim kodovima koji su brzi, ali imaju ograničenu točnost. CFD analiza u 3 dimenzije koje se danas uobičajeno rade vremenski su i računalno znatno zahtjevnije od klasičnih metoda, ali daju točnije rezultate.

U ovom radu modeliran je proces zatvaranja nepovratnog ventila pri hidrauličkom udaru. Kao referentni model uzet je nepovratni ventil DN 300 tvrtke MIV d.d. tip V2-08. Rezultat takvog numeričkog modela je karakteristika zatvaranja koja pokazuje promjenu kuta otvorenosti u ovisnosti o prosječnoj deceleraciji strujanja. Zatim je model nepovratnog ventila s poznatom karakteristikom zatvaranja ugrađen u dva karakteristična cjevovoda. Proračun nestacionarnog strujanja u cjevovodima napravljen je metodom karakteristika.

Abstract (english)

Check valves are used in various industries to prevent reverse flow in pipelines and thus protect sensitive components such as pumps or to prevent accidental discharge of the container. An ideal non-return valve closes when the flow changes direction. Since reverse flow often occurs in real situations, water hammer occurs at the time of closing. This pressure wave influences the valve and the pipeline equally. The amplitude of such pressure wave speed is determined by the return flow at the time of closing. Unsteady fluid flow is often simulated using one-dimensional codes. These codes are very quick, but, because of simplification, contain inaccuracies that should be taken into account. With the current state of technology, CFD analysis in three dimensions is not a problem, but such simulations are significantly more time consuming and computationally demanding than traditional methods.

In this paper, the closing process of a swing check valve during transient flow is modeled. The reference model is the swing check valve type V2-08, DN 300, from valve manufacturer MIV d.d. The result of such a numerical model is the closing characteristics which shows the change in the angle of openness in relation to the average deceleration of flow. After that the model of the non-return valve, with a known closing characteristics, is placed into two characteristic pipelines. Method of characteristics is then used to calculate pressure transients in these pipelines.

• Keywords: nepovratni ventil; hidraulički udar; nestacionarne pojave; cjevovod; metoda karakteristika
• Keywords (english): non-return valve; water hammer; unsteady fluid flow; pipeline; method of characteristics
• Language: croatian
• URN:NBN: urn:nbn:hr:235:328363
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-27 10:08:11