The development, construction and testing of a piston-expander for small-scale solar-thermal power plants.

Da Silva, Bradley (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.


ENGLISH ABSTRACT: The development of a prototype variable valve duration reciprocating steam expander was undertaken. A variable valve duration system was developed which could vary the cut-off ratio from 15 % to 90 %. An existing internal combustion engine was converted into the prototype reciprocating steam engine. Thermodynamic models were developed to determine the theoretical power output and working fluid consumption of the manufactured prototype engine. Proof of concept tests were performed on the engine. The engine was operated at 500 rpm where the output power and air consumption were measured. Tests were performed for various cut-off ratios to determine the influence on output power and air consumption. The experimental results showed a strong correlation to the theoretical effect of cut-off ratio on power output and air consumption. The maximum experimental output achieved was 1.396 kW at an 80 % cut-off ratio. The experimental power output was lower than the theoretical results which neglected mechanical losses in the system. The thermodynamic model over predicted the air consumption due to the assumption of instantaneous valve events.

AFRIKAANSE OPSOMMING: Die ontwikkeling van 'n prototipe veranderlike klep duur wederkerige stoom uitsitter is onderneem. 'n Veranderlike klep-duurstelsel is ontwikkel wat die afsnyverhouding van 15% tot 90% kan wissel. 'n Bestaande verbrandingsmotor was omskep as die bewys van konsep wederkerige stoom-enjin. Termodinamiese modelle was ontwikkel om die teoretiese kraguitset en werkvloeistofverbruik van die vervaardigde prototipe-enjin te bepaal. Bewys van konseptoetse is op die enjin uitgevoer. Die enjin is teen 500 rpm bedryf en die uitlaatkrag en lugverbruik was gemeet. Toetse is uitgevoer vir verskillende afsnyverhoudings om die invloed op die uitsetkrag en lugverbruik te bepaal. Die eksperimentele resultate het 'n sterk verband getoon met die teoretiese effek van afsnyverhouding op kraguitset en lugverbruik. Die maksimum eksperimentele uitset was 1.396 kW teen 'n afsnyverhouding van 80%. Die eksperimentele kraguitset was laer as die teoretiese resultate wat meganiese verliese in die stelsel nie in ag geneem het nie. Die termodinamiese model het die lugverbruik hoër voorspel in vergelyking met die eksperiment, weens die aanname van oombliklike klepgebeure.

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