Development of a magnetic gear for dry-cooling power plant applications

Mathee, Alexander (2017-03)

Thesis (MEng)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Due to excessive mechanical gear failure in air cooled condenser (ACC) for dry cooling applications there is a need to investigates possible alternatives. In this study research is conducted into magnet gear (MG) technologies which could potentially replace mechanical gears for dry cooling applications. Three promising magnetic gear topologies are identified which include the magnetic harmonic gear (MHG), the magnetic planetary gear (MPG) and the flux modulated magnetic gear (FMMG). Of the three identified MG topologies the MPG and the FMMG are deemed more viable from a manufacturing perspective. Two small prototypes are constructed and tested to gain further knowledge on the potential advantages and disadvantages of each topology. The PMG achieved the highest torque density of 139kNm/m3 compared to the FMMG with 87kNm/m3. Although the PMG achieved the highest stall torque output it also suffered from the highest losses with efficiency of 70% at full load compared to the FMMG prototype with 95% efficiency. These losses were caused by frictional losses in the PMG due to mechanical complexity. The relatively simple mechanical design of the FMMG topology makes it a suitable candidate for this study. To have a more objective comparison between the FMMG and the mechanical gear, a new FMMG prototype is optimally designed using 2D finite element method (FEM) according to the same specifications of an existing single-stage helical mechanical gear. The design is further refined to achieve higher efficiency after which the performance is verified by 3D FEM calculation. The mechanical design is also checked by performing mechanical stress analysis on all the critical sections of the design. Experimental tests of both the FMMG and the equivalent mechanical gear are conducted for performance comparison. The mechanical gear achieved a maximum efficiency of 95% under rated conditions of 132Nm torque and 160 rpm on the output shaft. The gear is also tested at 1.5 pu condition (198 Nm) and obtained an efficiency of 96%. The magnetic gear achieved results trailing within 2% of the mechanical gear's efficiency. The measured maximum efficiency of the FMMG are 93.5% and 95% at rated and 1.5 pu conditions, respectively. The power rating of the gears at 1.5 pu conditions is about 3.3 kW. The magnetic gear performed reasonably well in comparison with the mechanical counterpart. Both gears achieved efficiency in the mid 90% range. With the added advantage of over load protection and reduced noise transfer the magnetic gear appears to be a valid replacement for the mechanical gear in this specific application.

AFRIKAANSE OPSOMMING: As gevolg van oormatige meganiese rat falings in lug verkoelde kondensators vir droë lug verkoeling toepassings is daar 'n groot nood vir ondersoek in moontlike alternatiewe. Navorsing word in hierdie studie voltooi in die magnetiese rat veld om 'n moontlike plaasvevanger vir meganiese rat to verkry. Drie belowende magnetiese rat topologieë is geïdentifiseer naamlik die harmoniek magnetiese rat (HMR), die magnetiese planetêre rat (MPR) en die vloed modulerende magnetiese rat (VMMR). Uit hierdie drie keuses is die MPR en die VMMR beskou as die mees belowend van 'n vervaardigings oorpunt. Twee klein skaal prototiepes is gebou en getoets om verdere kennis op te bou oor die potensiale voordele en nadele van elke topologie. Die PMR het die hoogste wringkrag digtheid van 139kNm/m3 bereik in vergelyking met die VMMR van 87kNm/m3. Alhoewel die PMR die hoogste wringkrag digtheid bereik het dit ook die meeste verliese ervaar met 'n effektiewiteit van 70% teen vollas in vergelyking met die VMMR met 'n effektiewiteit van 95%. Die verliese in die PMR is veroorsaak deur wrywing as gevolg van meganiese kompleksiteit. Die relatiewe eenvoudige meganiese ontwerp van die VMMR maak die hierdie rat topologie 'n aanvaarbare kandidaat vir hierdie studie. Om 'n meer objektiewe vergelyking tussen die VMMR en die meganiese rat te bereik is 'n nuwe VMMR prototiepe optimaal ontwerp, deur middel van 2D eindige element metode (EEM), volgens dieselfde spesifikasies as 'n bestaande enkel fase heliese meganiese rat. Die ontwerp is verder verfyn om 'n hoër effektiewiteit te bereik wat daarna bevestig is deur 3D EEM simulasies. Die meganiese ontwerp van die VMMR prototiepe is ook nagegaan deur middel van 'n meganiese stress analiese op kritiese dele van die ontwerp. Toetse van beide die VMMR en die ekwivalente meganiese rat word uitgevoer vir prestasie vegelyking. Die meganiese rat het 'n maksimum e ektiewiteit bereik van 95% onder gegradeerde omstandighede van 132Nm wringkrag en 160 rpm spoed op die uittree as. Die rat het ook 'n effektiewiteit van 96% bereik onder 1.5 maal toets omstandighede van (198 Nm). Die magnetiese rat het kort op die hakke van die meganiese rat presteer en binne 2% van die meganiese rat se effektiewiteit bereik. Die gemete maksimum effektiewiteit van die VMMR is 93.5% and 95% by gegradeerde en 1.5 maal gegradeerde omstandigehede. Die krag uittree by 1.5 maal gegradeerde omstandighede is 3.3 kW. Die magnetiese rat het redelik goed presteer in vergelyking met die meganiese eweknie. Altwee ratte het effektiewiteit bereik van rondomby 95%. Met die begevoegde voordeel van oorlading beskerming en verminderde geraas oordrag betoon die magnetiese rat waarde as 'n moontlike plaasvervanger die 'n meganiese rat vir hierdie toepassing.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100933
This item appears in the following collections: