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Design of a rotary valve for pressurisedsteamTalent NyawoMaster of Science Thesis MMK 2016:107 MKN 176KTH Industrial Engineering and ManagementMachine DesignSE-100 44 STOCKHOLM

Examensarbete MMK 2016:107 MKN 176Utveckling av rotationsventil för trycksatt ångaTalent NyawoGodkäntExaminatorHandledare2016-09-15Ulf SellgrenKjell AnderssonUppdragsgivareKontaktpersonRanotor ABPeter PlatellSammanfattningDenna rapport är gjord på ett examensarbete som var utfört på uppdrag av det svenska företaget RanotorAB. Syftet var att utveckla en konceptuell lösning för en rotationsventil som skall fungera i en miljö medhög temperatur och högt tryck. Ventilen skall arbeta under höga rotationshastigheter, vilket kräver kortaöppettider.Tekniska hjälpmedel såsom SolidWorks, ANSYS och MATLAB användes för att modellera ochanalysera de konceptuella lösningarna.Slutlösningen valdes från ett flertal olika koncept, varpå detta vidareutvecklades och optimerades.Betydande material och gastätningslösningar identifierades och utvärderades för att hitta den bästalösningen. Optimering av individuella komponenter och hela anordningen gjordes med avseende påspänning, termisk- och dynamisk analys. De givna specifikationerna uppfylldes och resultaten vartillfredsställande.Resultaten ger en teoretisk bas för vidareutveckling och applicering av en rotationsventil in en miljö medhög temperatur och högt tryck.Nyckelord: roterande ventil , uniflow motor, gastät försegling , rörlig bryttidpunkt ,hög-tryck-hög-temperatur1


Master of Science Thesis MMK 2016:107 MKN 176Design of a rotary valve for pressurized steamTalent NyawoApprovedExaminerSupervisor2016-09-15Ulf SellgrenKjell AnderssonCommissionerContact personRanotor ABPeter PlatellAbstractThis Master thesis is a project commissioned by the Swedish company Ranotor AB. Theobjective of this thesis is to develop a conceptual solution for a rotary valve mechanism that hasto work efficiently in a high-temperature and high-pressure environment. The valve is to operateat high rotational speeds which calls for very short opening time.Modern engineering tools namely Solidworks, Ansys and Matlab, were employed for modellingand analysis of the conceptual solution.The best design solution was selected from three developed concepts, and the selected conceptwas further developed and optimized. Major material candidates and gas-tight sealing solutionwere identified and evaluated and the optimal material and seal design was chosen. Optimizationof the individual components as well as the whole assembly was performed based on stress,thermal and dynamic analysis. The given design specifications and functions were fulfilled andthe results were satisfactory.The obtained results provide a theoretical foundation for the development and application of arotary valve in high-temperature and high-pressure environment.Keywords: rotary valve, uniflow engine, gas-tight sealing, variable cut-off time,high-pressure-high-temperature3


FOREWORDThe author would like to express his gratitude to Ranotor AB for the opportunity to work on thisinteresting and challenging project.Particular thanks goes to Ovel and Peter Platell for their invaluable support and research atRanotor AB.Special appreciation goes to my supervisor Kjell Andersson and my examiner Ulf Sellgren atKTH Royal institute of Technology, for their great knowledge, advise and interestingdiscussions.Talent NyawoStockholm, June 20165


NOMENCLATUREThis section lists the Notations and Abbreviations that are used in this Master thesis.NotationsSymbolDescriptionEYoung s modulus (Pa)FFilling ratio (%)LsStroke length (mm)MbBending moment (Nm)pPressure (Pa)PPower (W)PdDesign power (W)PcorrCorrected power (W)QVolumetric flow rate (m3/s)rRadius (m)tTime (s)TTemperature ( C)vVelocity (m/s)WbSection modulus (m3)ZfOpening length (mm)𝜌Density (m3/kg)𝛥hChange in enthalpy (kJ/kg)𝜑fFilling angle ( )σeEquivalent stress (Pa)σyYield stress (Pa)τShear stress (Pa)AbbreviationsBDCBottom Dead CenterBRVBishop Rotary ValveCADComputer Aided DesignCHPCombined Heat and Power7

CAEComputer Aided EngineeringHTHPHigh-temperature-high-pressureIC engineInternal Combustion enginemsMillisecondsrpmround per minuteSFSafety FactorTDCTop Dead Center8

Table of ContentsSAMMANFATTNING (SWEDISH).1ABSTRACT.3FOREWORD .5NOMENCLATURE .7TABLE OF CONTENTS .91.INTRODUCTION111.1.Project Introduction . 111.2.Thesis Project Aim . 111.3.Deliverables . 121.4.Delimitations . 121.5.Method . 122. STATE OF THE ART132.1.Background Information. 132.2.Overview of the piston expander . 142.3.Rotating valve as part of the piston expander. 153. PRIOR KNOWLEDGE IN VALVE TECHNOLOGY3.1.17Valve overview . 173.1.1.Poppet Valves . 173.1.2.Sleeve valve. 183.1.3.Rotary valve . 193.2.Valve Actuation systems . 193.2.1Pneumatic valve actuation . 203.2.2Hydraulic actuation . 203.2.3Electrical actuation . 213.2.4Mechanical actuation. 213.3.Rotary valve development . 223.3.1The Bishop Rotary valve . 223.3.2Lamberts’ Rotary Valve . 239

4.CONCEPT DEVELOPMENT254.1.Product requirements specification . 254.2.Description of concepts . 274.3.Concept Selection . 314.4.Material selection . 324.5.Concept Analysis . 374.5.1Preliminary Flow Analysis . 374.5.2Dimensioning of the valve outlet port . 384.5.3Variable cut-off timing . 414.5.4Dimensioning of the valve body . 424.5.5Dimensioning of the Transmission system . 424.5.6Shaft dimensioning . 454.5.7Dynamic Analysis . 494.5.8Bearing Selection . 514.5.9Preloaded fasteners in tension . 514.5.10 Thermomechanical analysis . 544.6.Selection of a seal design. 555. RESULTS . 566. DISCUSSION AND CONCLUSION . 597. FUTURE WORK . 618. REFERENCES . 63APPENDIX A: MATLAB CODE . 6510

1. IntroductionThis chapter outlines the project introduction, the targeted goals, limitations and the methodused in this project.1.1.Project IntroductionThis Master thesis is based on the subject of designing and modelling a valve concept which ispart of a modern steam expander. The project is in collaboration with KTH Royal Institute ofTechnology, and the Swedish company Ranotor AB. The rotary valve is a critical component ofa modern steam expander. The other part of the overall project involves the designing of thecylinder package, which has to be assembled together with the rotary valve mechanism andprototype the whole engine.1.2.Thesis Project AimThe objective of this project is to generate and analyse a conceptual solution of a valve systemthat can work efficiently in the conditions of high-temperature and high-pressure as well asmeeting the given specifications.This thesis project is a subproject of a ‘big project’ which has the overall aim of having a fullCAD model of the whole engine which is going to be prototyped in order to test the feasibilityand compactness of the engine. Several projects have been conducted before, working ondifferent components of the engine. The research and skills from different engineers togetherwith the vast experience gathered by Ranotor AB were used as input in these projects. A PhDthesis has also been carried out with the aim of developing an analytical rigid body kinematicsand inverse dynamics model of the steam expander. The results from these projects are to beused as the foundation on which this Master thesis is based on.Ranotor AB is aiming at putting all the accumulated experience in visualising the technologythrough prototyping of a new multi-cylinder axial piston steam engine. The engine involvesseveral new components such as a single rotating valve, novel sealing in the crankshaft and onthe piston.Ranotor has investigated several concepts for the modern steam engine. During the years aconcept that involves a multi-cylinder axial reciprocating piston engine has been developed thatseems to offer the best overall qualities.Ranotor has carried out substantial analysis work on thermodynamics and fluid mechanics forthis modern steam engine. The company has also carried out kinematic analysis of the axialpiston engine that is laying the foundation to this thesis work.11

1.3.DeliverablesThe following are the expected outcome of this project A complete conceptual solution of the rotary valve including the housing and sealing CAD model of the proposed solution (3D and 2D in Solidworks) Design concept description (working principle) Analysis of the concept (dynamics, mechanical stresses and thermal effects) Selected material1.4.DelimitationsIn order to achieve the aimed goals within the given timeframe, the project was limited to theabove expected outcomes and the following aspects are beyond the scope of this thesis project: Tribological and wear analysis Computational fluid dynamics1.5.MethodThe project starts with background research where prior art in the engine technology and valvesystems is reviewed. Information is gathered from different sources like scientific articles andpatents. After information gathering, at least two concepts are to be generated where the bestsolution will be selected using the Pugh Matrix. Each component of the selected mechanism is tobe allocated a material before modelling for optimal functionality and strength. Conceptmodelling include stress, thermal and dynamic analysis of individual components and theassembly as a whole is to be performed. A number of modern engineering tools are to beemployed for analysis. This include modern CAE tools like Matlab, Ansys, and SolidWorks.12

2. State of the artThis chapter gives the details of the overall project and the technology behind it. This is the baseon which this thesis is established.2.1.Background informationDuring the oil crisis in the 70s the Swedish car manufacturer SAAB launched an ambitiousprogram to develop a modern and compact steam engine. This seemingly promising technologywas later abandoned due to inefficient, bulky and insufficient performing solutions. (J. P Norbye,December 1974). The emergency of new materials and technology, increasing demand for lowfuel consumption and lower harmful emissions has justified the ‘rebirth’ of a steam engine.A modern steam engine is full of potential and is promising in developing alternative fuels andmaking use of natural resources which are more friendly to the environment and can be helpfulin future as oil resources are running out.Recent research has proved the possibility of a modern high efficiency, powerful and compactsteam engine. (P. Platell, 1993). A modern steam engine has several key advantages over theconventional internal combustion engine. These advantages include the following; Fuel flexibility: this include different forms of biomass, waste products from the petrolindustry, by-products from industries, as well as waste products from agricultural andforestry industries.Full torque at low rpm and maximum efficiency at part load. This is contrary to theinternal combustion engine which gradually offers a maximum torque and reaches itsbest efficiency close to full load. Free NOx emissionsHigh power density: contrary to popular belief, a modern high performance steam enginehas inherent possibility to offer high power density. With a thermal battery, a modern steam engine can offer regenerative engine braking andstoring cheap and green electricity in the same way as electric propulsion.With the support of the US military, the Florida based company Cyclone Power has developedand built a modern steam engine. On the other side, the Swedish based company Ranotor AB hascontinued SAAB’s program in developing a high performance modern steam engine. Thesemodern research and findings have proved beyond doubt that a compact modern steam engine ispractically possible.Ranotor AB has also patented a number of key technologies that would allow its technology tobe employed in the automotive industry. Another possible application of the steam engine is inCHP (combined heat and power), and the recovery of waste heat from industrial process and tosave as a range extender in an electric vehicle.Steam engine: A steam engine is a heat engine that performs mechanical work using steam asits working fluid. (Wikipedia) Heat is received from a high temperature source and steam isformed in the steam generator. The generated heat is then converted to mechanical work, throughthe utilisation of a piston expander. There are different piston expanders as well as thermalcycles which can be used depending on the required power, fuel supply, and other restrictions.The Rankine cycle and the Sterling cycle are some of the examples of the cycles that areemployed in a modern steam engine.13

2.2.Overview of the piston expanderBasing on the conventional concept of a steam engine, Ranotor has investigated and developedseveral concepts of a modern steam engine. A multi-cylinder axial reciprocating piston enginehas been developed and it seem to offer the best overall qualities in terms of cost/performance.The engine involves several new components such as a single rotating valve, novel sealing in thecrankshaft (wobble plate) and on the pistons.The configuration of the engine is shown in Figure 1:Figure 1: Representation of an axial piston expander with the wobble plate. (R S. Löfstrand, 2009)The main components of the axial piston expander are the cylinder head, the piston, the pistonrod, wobble plate, crank shaft, and the engine block.Figure 2 gives the schematic representation of the engine.Figure 2: Schematic representation of the piston expander14

The main concept of the steam engine consists of a five-cylinder axial piston expander with awobble plate. The wobble mechanism connects the pistons and the crankshaft. In-between thewobble plate and the pistons are the piston rods.There are different configurations of the axial piston expander depending on how the tilted plateis connected. Depending on the engine configuration, the tilted plate has different names like theswash plate, the bent axis or the wobble plate. (T. C. Dickenson, 1999)In the wobble plate configuration, the reciprocating motion of the pistons is transformed to therotational motion of the engine shaft by the use of the piston rods and the wobble plate. A fullcycle of each piston gives a complete revolution of the engine shaft. The engine shaft (also calledthe Z-shaft) delivers out the mechanical energy performed by the pistons. Pure nutation isachieved through the synchronisation of the wobble plate which is connected to the engine blockvia a gear.The pistons are disposed around the crankshaft in a concentric circle, the wobble plate isresponsible for controlling the axial position of the pistons in the piston head. The steam will befilled and emptied as the crankshaft rotates.2.3.Rotating valve as part of the piston expanderThe valve system on the expander is responsible for controlling the flow of the steam in and outof the cylinders. The rotating single valve is part of the new components introduced in themodern steam expander.The valve has been proposed many times before in engine history due to its many inherentadvantageous features over poppet valves. It was claimed that improved breathing and burningcharacteristic with the rotating valve gave higher specific power and higher efficiency thanconventional poppet valves.These features were satisfactorily demonstrated but there were problems that prevented theconcept to be commercially viable. The problem was to realize a design that offer both reliabilityand low oil co

Tekniska hjälpmedel såsom SolidWorks, ANSYS och MATLAB användes för att modellera och analysera de konceptuella lösningarna. Slutlösningen valdes från ett flertal olika koncept, varpå detta vidareutvecklades och optimerades. Betydande material och gastätningslösningar identifierades och utvärderades för att hitta den bästa .

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