ASPECTS OF MEASUREMENT AND CONTROL OF AIR/GAS RATIO FOR GAS FIRED PLANT Geçen sayıdan devam . . . Marcus GRANT Morcus GRANI is currenty o reseorch student fundec by Bıitish Gos plc and is registerec for o PhD reseorch degree in 'Alr/Gos Rotı ocontrd forContrd forNozzle Mix Burners' ot Coventry University. Applying the concepts of eıectronic ond physics connbinedwith ınvestigoting proctlcoble solutions to o fundomentoı lndustrk:ıl probl em. Dr. Keith BURNHAM Dr. Ke i th BLl'lNHAM is Co-Director of the Control Theory ond Appticotions Centre ond a Sen l er Lecturer in the Schoo of E ngineer l ng ot Coventry University. Acentral theme within fhe Centre's octi vi ties is that of apply i ng mathemaficol modelling computer�mulotionond advancec control k:ıw design techn i ques to the soıution of lndustrial problems. Dr, BURNHAM's main interest İS thct ofdeveloplng odoptive/self-tuning control strotegies tor nonlineor systems. Dr.Peter LOCKETT Dr.Peter LOCKEET İS o Senior lecturer in the Schoo l of Mothemot i coı ond tnformction,Sclences ot Covenlry Universily. Wilh o bockground in pure mclhemotics he i s presenty oct l vely lnvdvec with o wide renge of projects invdving moth· emoticoı madelling ond opt i moı controı ıow desİgn tehniques. ronglng fronn energy systems to intelligent outonomcus cruise controı. GAZ YAKAN ENDÜSTRİYEL TESİSLERDE HAVA/ GAZ ORANININ ÖLÇÜMÜ VE KONTROLÜ özet: Endüstriyel sistem/erde ve tesis/erde, kullanılan tesislerin verlmlillğive momülün kalitesiyle 1/gllenilmekfedir. Üretim tesislerinde, fırınlar yaygın şekilde kullonılmokfodır. Doğal gaz kullanılan bir sistemde ise, hava ve gaz akış, yaklaşık 10:1 oranında korıştrrıhr ve brülöre daha az veya daha çok gaz gönderir ve oran kontrol sistemi, brülöre hava akış oranını, gaz akışındaki değişime göre, bir valf vosrtosıylaoyorlor. Hava/gaz oranınınyanlışolması, mamül kolitesindebozulmayoııeayrrcozororhgozlorınemis)'Onuno neden o/ocokfrr. Kullonıımokto olan hava/gaz oranı kontrol sistemleri, mekanik ve elektramekonik teknolojiye dayanırlar ve çoğunlukla modem sistem/erde istenen performansı soğloyomazlor. Çalışmada, bahsi geçen sorunlaraneden olduğu düşünülen valf/erle ilgi// yapılan Joborotuor testlerinden elde edilen sonuçlar üzerinde durulmuştur. Va/tin dovronrşın, inceleyen modelleme metodları ve korekferlze edenporometreleredeğinllmlştır. Ayrıcahava/ gaz oranını kesin performansla kontrol eden çeşit// seçenekler üzerinde durulmuştur. Bunun drşrndo, geniş kapsamı, incelendiğinde bilgisayar kontrollü sistemler geliştirilebilmektedir. Abstract: By investigating the performance of three ge• neric lypes of air/gas ratio control systems. the paper highlights the problems currently facing the industry in terms of maintaining accurate controı of air/gas ratio wtıilst. at the same time. satisfying increased demands tor greater turn down ratio. it is concluded that, since the air/ gas valves are fundamental components ¼ithin any air/ gas ratio control system. futher investigative studies should be aimed at adopting an on-line systems modelling approach in orderto identifythesalientnon-linearfeatures ofeach vaivetype. The overall objectlve in the ıongerterm being to develop an integrated computer controlled system. 3.2.RESULTS The results of Test 1 corresponding to the rnechanical, electro-rnechanical and electronic systerns are given in Figures 3a, 36 and 3c OO/;iAL GAZ DERGİSİ SAYI. 28 138 respectively and those for Test 2 are given in Figures 4a, 46 and 4c. Noce that ehe scales used in these Figures differ. In each of these Figures ehe lower trace illustrates the actual AGR achieved; with the two rernaining traces representing ehe air and gas flows (denoted 'a' and 'g' respectively) It is clear frorn Figures 3a and 36, which illustrate typical results for the rnechanical and electro-rnechanical systern, chat each has its own distinctive behaviour. The eleccronic sysrern, Figure 3c, is founcl consiscenly ro produce ehe rnore favourable resules. However in cerrns ofehe resulting AGR characcerisrics, ehe rnechanical and elecrro-rnechanical systerns, of Figure 3a and 36, are found ro produce cornparable perforrnances in rerms of overall accuracy yet produce discinctively clifferent perforrnances in cerrns ofeheprofileof theAGR. I n ehecaseofehernechanicalsysrern,duringehe rransitionary period ehe ratio is consiscently fuel rich, whereas in ehe sceady-srace period of operation ehe ratio is consrantly found co be rnarginally lean. The perforrnance ofehe electro-mechanical sysrern is found ro be characterised by an altemacing rich-lean ratio during ehe cransicion period, again producing a rnarginally lean ratio in steadysrate. However, ehe eleccronic syscern is found to produce a perforrnance which consrantly seeks the correcr balance. Ir should be noced ebat a rnarginally rich operation is found in ehe transitionary periods. By cornparing Figures 4a-4c corresponding ro
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