Computational and experimental investigation of chamber design and combustion process interaction in a spark ignition engine

Van der Westhuizen, H. J. (2003-12)

Thesis (MScEng)--University of Stellenbosch, 2003.

Thesis

ENGLISH ABSTRACT: The automotive industry in South Africa is expanding as a result of pressure on the world economy that forces vehicle manufacturers to outsouree work to developing countries. In order to add value to automotive engine development, the capability to perform state-of-the-art engineering must be developed in this country. Threedimensional fluid flow simulation is one such area and is being developed in this study in order to enhance the ability to develop combustion systems. Another capability being developed at the University of Stellenbosch is the simulation of valve train dynamics. It was realised that there is a lack of research results of in-cylinder flow characteristics and how they influence combustion chamber processes. This project focuses on the investigation of two different combustion chamber geometries and how they influence the flow and combustion processes in two different combustion chambers. The aim is to gain a better understanding of combustion chamber flow as an indirect result from comparing the flow in two fundamentally different engines under similar operating conditions. The difference in the engines is that one was developed for reduced exhaust gas emissions while the other was developed to achieve high performance. The numerical simulation capability is developed in the process of achieving this goal. To achieve the above-mentioned aim, a literature study was performed on the different combustion chamber flow characteristics and how they are influenced by different configurations. An experimental method of measuring combustion characteristics is studied in order to establish the ability to perform the latter. Theory of numerical flow simulation is also studied with this same goal in mind. Experimental testing is performed and combustion analysis is done on the results. In conjunction to the experimental work, numerical flow simulations are performed on the two different combustion chambers. The results from experimental testing and numerical simulations have shown that obstructions in the flow into the combustion chamber, together with a port configuration that cause flow around the longitudinal axis of the cylinder, increases the rate at which fuel burns in the combustion chamber and thereby reduce the production of toxic emissions from the engine. The study also proved that reducing resistance to flow increases the amount of air that is breathed by the engine and thereby results in increased torque generation. Through this study, opportunities for further research are identified. The results of the study can be used when new combustion systems are developed, especially in the light of ongoing tightening of emission regulations. The contribution to numerical flow simulation capabilities developed in this study add value to the ability to develop new combustion systems in the future, especially when complimented by some of the further research topics identified.

AFRIKAANSE OPSOMMING: Die motorbedryf in Suid-Afrika is besig om vinnig te ontwikkel as direkte gevolg van druk op die wêreldekonomie wat internasionale motorvervaardigers forseer om werk na ontwikkelende lande uit te kontrakteer. Hoogs gesofistikeerde ingenieurstegnieke moet ontwikkel word in Suid-Afrika met die doelom waarde toe te voeg aan enjin ontwikkeling. Drie-dimensionele vloei simulasie is een van hierdie vermoëns en word tydens hierdie studie ontwikkelom die verbrandingstelsel ontwikkelings-vaardighede te bevorder. Nog 'n vaardigheid wat tans ontwikkel word aan die Universiteit van Stellenbosch is die vermoë om nok-en-klepstelsel dinamika te simuleer. Daar bestaan egter 'n leemte in navorsingsresultate van vloei eienskappe binne in die verbrandingsruim en hoe dit verbrandingsruim prosesse beïnvloed. Die projek fokus dus op 'n ondersoek van twee verskillende geometriese konfigurasies van die verbrandingsruim en hoe dit die vloei- en verbrandingsprosesse in die twee konfigurasies beïnvloed. Die doel is om 'n beter begrip te ontwikkel van verbrandingsruim prosesse as 'n indirekte gevolg van die vergelyking tussen twee fundamenteel verskillende enjins onder eenderse bedryfstoestande. Die verkil tussen die twee enjins is dat een ontwikkel is met die doelop verlaagde uitlaatgas emmissies en die ander ontwikkel is om verbeterde werkverrigting. Die numeriese simulasie vermoë is ontwikkel in die proses om die doel te bereik. Om bogenoemde doel te bereik is 'n literatuurstudie gedoen wat verskillende vloeieienskappe in die verbrandingsruim ondersoek, asook hoe dit deur verskillende konfigurasies beïnvloed word. 'n Eksperimentele metode III die bepaling van verbrandingseienskappe is ook bestudeer met die doelom laasgenoemde uit te voer. Teorie aangaande numeriese vloei simulasie is ook bestudeer met bogenoemde doel. Eksperimentele toetse is gedoen en verbrandingsanalise uitgevoer op die resultate. In kombinasie met die eksperimentale werk is numeriese simulasies van die prosesse in die twee verbrandingsruim konfigurasies uitgevoer. Die resultate van die eksperimentele toetse en numeriese simulasies toon dat obstruksies in die vloei na die verbrandingsruim, gesamentlik met die poort konfigurasie wat veroorsaak dat lug om die longitudinale as van die silinder vloei, die tempo waarteen die lug-brandstof mengsel verbrand verhoog en sodoende die vrystelling van skadelike uitlaatgasse na die atmosfeer verminder. Die studie het ook getoon dat die vermindering van weerstand teen vloei, die hoeveelheid lug wat in die verbrandingsruim invloei vermeerder en sodoende die wringkrag wat deur die enjin gelewer word verhoog. Deur die studie is verdere navorsingsgeleenthede uitgewys. Die resultate van die studie kan gebruik word in die ontwikkeling van nuwe verbrandingstelsels, veral in die lig van verstrengende regulasies rakende uitlaatgas emmissies. Die bydrae tot numeriese vloei simulasie vermoëns ontwikkel in hierdie studie voeg waarde toe tot die vermoë om nuwe verbrandingstelsels te ontwikkel, veral wanneer dit gekomplimenteer word met van die verdere navorsingsonderwerpe wat geïdentifiseer is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/53334
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