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Modern högpresterande Ångmotor: Snabba Ventiler
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2007 (Swedish)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesisAlternative title
Modern high efficient Steam engine : Quick Valves (English)
Abstract [sv]

Fördjupningsarbetet har inriktats på analyser av inloppsventilen som ingår i ettutvecklingsarbete av en modern högpresterande ångmotor som företaget RANOTOR driver.Hårda krav ställs då höga temperaturer, extrema tryck och korta öppningstider återfinns isystemet.En studie över befintliga ventilmanövreringstekniker har gjorts där vissa tekniker har varitmer passande för denna applikation, t.ex. den teknik som det svenska företaget CARGINE harutvecklat. Här styrs ventilrörelsen genom att ett pilotsystem reglerar tryckluft och har somfördel att variabla öppningstider lätt kan åstadkommas.Vidare har en utredning om piezoelement gjorts, vilka skulle kunna implementeras iventilmanövreringens pilotsystem. Fördelen med dessa är den extremt snabba rörelse som kanåstadkommas.Bestämning av ventilens egenfrekvenser gjordes och resultatet blev, tillsammans med enanalys av frekvensinnehållet i ventilens rörelsemönster, att man troligen endast kommer attexcitera ventilens första egenfrekvens. Denna egenfrekvens är en transversell svängningsformsom exciteras vid 1500-1600 Hz beroende på val av ventilmaterial.Då osymmetriskt flöde av arbetsmediet kring ventilen troligast kommer uppkomma, gjordesen analys av hur en tvärkraft som angriper ventilen påverkar hålkantstrycket i kontaktenmellan ventil och ventilstyrning. Resultatet blev att när denna kraft närmade sig 10 N börjademan få alltför höga kontakttryck, och detta då ventilskaftet hade en diameter på 2 mm.2CFD är förkortningen av Computational Fluid Dynamics, och används för att numeriskt lösafluiddynamikproblem. Här görs ett försök att få en uppfattning om hur flödet beter sig runtventilen när den har öppnat och luften strömmar in i expansionsrummet. Domänen somanalyserats ficks genom att göra en sammanställning av ventilen och omkringliggandegeometrier i Solid Edge. Denna exporterades sedan till Ansys där analysen utfördes.När det gäller resultatet av den transienta analysen har bedömningen gjorts att resultatet inteär helt tillförlitligt utan endast ger in bild av vilken information, i form av bilder och grafer,en CFD-analys ger. Dom resultaten som fåtts visar att trycket efter 2.5 ms uppgår till ca 220Bar, och att det blir en osymmetrisk tryckfördelning runt ventilen som skapar radiellbelastning, samt att det redan tidigt bildas kraftig turbulens.

Abstract [en]

This project has been specialized upon analysis of the intake valve that is a component in amodern high efficient steam engine that is developed by RANOTOR. A difficult environmentwas specified, such as high temperatures, extreme pressures and short open time.A study of the existing techniques for maneuvering a valve was done where very commonused techniques and more special applications was described and compared. The Swedishcompany CARGINE develops the best fitting technique for the steam engine application. Themovement of the valve is created and controlled by compressed air indirectly by a pilotsystem. Its advantage is in the easy controlled open time of the valve.The world of piezo crystals has also been investigated. Stacks of crystals can be used to createthe motions in the pilot system, from an electrical signal to a mechanical. The advantage inthe piezo technique lies in the extremely fast movements that could be created.The valves lowest eigenfrequencys was calculated and together with the frequency content ofthe valves motion pattern, has it been determined that only the first eigenfrequency is likely tobe set in motion. This eigenfrequency is set in motion at the frequency of 1500-1600 Hzdepending of the valve material.When there’s probably going to be unsymmetrical gas flow around the valve, there going tobe a force crossways the valve. An analysis was made to understand when this force wasgoing to create a problem in the contact between the valve and its surrounding component.The result was that when the magnitude of this force came close to 10 N, problems wasdetected in the contact. The calculations were made with a valveshaft diameter of 2 mm.To solve the fluid dynamic problem, CFD with Ansys has been used. CFD is a shortening ofComputational Fluid Dynamics and is a numerical solution of the flows, pressures and muchmore witch was less interesting for us. What we were after in this analysis was how the flows4and the pressure was acting around the valve when it was at it most open position. Thegeometry that was analyzed was created with Solid Edge and then imported into Ansys.Concerning the result from the CFD analysis did we come to the conclusion that those resultsweren’t completely accurate. However they do give us a hint of what can come as a result in adeeper and more accurate analysis. Our results show that after 2.5 ms has the pressure raisedto 220 Bar, and that an unsymmetrical pressure is affecting the valve, which creates a radialforce. Also has we shown that even early in the analysis there’s strong turbulence in the steamflows.

Place, publisher, year, edition, pages
2007.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-171950OAI: oai:DiVA.org:kth-171950DiVA: diva2:844947
Examiners
Available from: 2017-02-13 Created: 2015-08-10 Last updated: 2017-02-13Bibliographically approved

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