A thesis, submitted to the Faculty of Engineering, University of the Witwa,t(m~~ rand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. -;;., Johannf,'"~l)Urg,. April'25, 1994 / A numerical' and experiruental. investig~tion ~£free~cylinder Stirling engines is repbited. Tllis work evolved from an attempt to de~,elop a palt.icular freecylinder Stirlingengineif::oncept, such that commerci~~lmanufa<:ture and application as .tll~power source for a wateP pu.mp could be. coosidered. Available desigI(~QoIs' 'were not. dirittly applicable .to the engine being ~onsi<:lered. .The linea'f altalysis technique (coupled ~ith segond orderheat tra~sferj,thermody: gamic and "loss ,analysis), dey-eloped and implernented as 18 computer, program~ e by nM Bercho~i~,z was therefore ext~nded to allow the simulation of free-cylinder engines. .The ,s~lut.ipn procedure (follows ~ more, gen~raHzed fqrm than that adopted by Betr~hovvttz.. As a ]."esrutsymbolic manipulation ..and solution of the equations was impracticaL However numericalroot map gen~rat!oIl and ,the simple pr?~uction of force vector ~iagrams q,llr,)ws useful design mformatlon babe obtained: ~0 n .. _ '. '.' .r, ' _ . ". ,' ' _ ' " -'~-::~_, ,; Experimentah~orkwas carried out .on-two very diff,~rent machines. 'A Sufi;' p,ower free-cylinder Stirling ,',engni,e,pr,ototype Jb,Q.elded,disapopi,,ntlllg.•res,u,lts, a~ ,.' '. _'!7.. . ,the engine did, not run: satisfactorily. However the. data gathered provides a useful check of the general applicability of t11-ecouple4 analysis, method. The second engine, a modified S,1lnpowerModel B-lO,Demonstra.~T 'yielded motion and pressure data .over a wide l'al1ge bf operating conditions} The effects o£" \I changes in parameters such as,thl:fcase-ground spring stiffness, di~placer spring stiffness, case mass, charge pressure, Qot-end temperature and load. were explored. Agreement between experlmentalreeults arid simula,tio\l:r~s41ts uS~flg the coupled analysis is reasonable, particularly when one consicI'ersoi;hewid~ range of operatin;g conditions over which the compari§on is made. " , , /.(""" ,0 ,

A resonantly-coupled ��-Stirling (RCAS) cooler was designed and constructed. Tests on air and helium were performed with constant driving displacement over a range of frequencies. The effects of changing driving amplitude and charged pressure were studied. The use of stainless steel bellows in place of pistons eliminated the problem of piston seals and relaxed the construction tolerances. The fatigue life of the bellow is, however, a problem. The experimental optimization based on Taguchi methods was performed on regenerator mass, regenerator wire diameter, vibrating mass, and damping coefficient. Driven by a voice coil actuator, the characteristic phase shift of the Stirling cycle cooler was demonstrated where the hot-end displacement led the cold-end displacement. The 90�� phase shift was selected as the natural frequency. The pressure-volume diagrams for each working space were plotted and the indicated powers were determined. The compression powers in the hot and cold-ends show maximum values near the natural frequency. The mechanisms are different. At the hot-end where the displacement was kept constant, operation near the natural frequency gave a maximum pressure ratio and also maximized the compression power. The phase shifts in the cold-end were, however, relatively constant. The maximum pressure ratio and amplitude gave the maximum expansion power near the natural frequency. The expansion powers in the cold-end as indicators of cooling potential were approximately 2-4 watts for the air case, and 3-7 watts for the helium case. In both air and helium tests, the value of the parasitic losses reached 12 watts. The temperature difference developed across the regenerator is considered an indication of the cooling capacity. Good correlations were found between the indicated cooling capacity in the expansion space and the temperature difference. For a given size of cooler, the use of helium offered higher cooling capacity due to smaller pressure drop loss and smaller amplitude ratio. Higher cooling performance was also attained from helium at elevated pressures. / Graduation date: 1998

Thesis (M.S.)--Ohio University, November, 1991. / Title from PDF t.p.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 113-114). Also available via the Internet.

MSc, Faculty of Engineering, University of the Witwatersrand, 1978

Thesis (M.S.)--Ohio University, November, 1992. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, August, 1993. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, June, 1998. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, August, 1992. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, June, 1993. / Title from PDF t.p.