Experimental research of mixing nozzle for ejectors

7 EXPERIMENTAL RESEARCH OF MIXING NOZZLE FOR EJECTORS Pe Dolejš Technical Uni e si y o Libe ec Facul y o Mechanical Enginee ing S uden ská 2, 461 17, Libe ec 1, Czech Republic [email p o ec ed] Abs ac In his a icle, wo posi ions o a lobe-shaped nozzle in ended o he ejec o mixing p ocess a e compa ed. The objec i e o he expe imen s was he iden i ica ion o he c oss-shaped nozzle low pa e n. The measu emen s o nozzle eloci y p o iles we e conduc ed a a p essu e o 2 kPa. Sepa a e nozzle eloci y p o iles we e measu ed om he nozzle mou h up o he dis ance o 90 mm and 180 mm, in 15 mm o 30 mm in e als espec i ely. In his way, 10 eloci y p o iles we e measu ed pe each nozzle posi ion and consequen ly used o he inal diag am. An impo an p inciple o he ecommenda ion o a nozzle o he mixing p ocess was he cha ac e is ics o c oss-shaped nozzle eloci y p o iles measu ed a di e en posi ions, using he mode n con ac less measu emen me hod - Lase Dopple Anemome y (LDA). Based on he measu ed da a, he c oss-shaped nozzle eloci y p o iles we e desc ibed in de ail. De ec s o he c oss-shaped nozzle we e iden i ied by he expe imen s and hus i s unsui abili y o he ejec o mixing p ocess. In oduc ion Despi e an ex ensi e boom o so wa e modeling echniques he expe imen al app oach o he esea ch handling he a ea o luid mechanics is s ill an i eplaceable sou ce o in o ma ion. E en he bes ma hema ical-physical model deals wi h simpli ied o idealized condi ions. Fo ha eason, i is necessa y o adjus he model and e i y i by compa ing he esul s wi h a p o en me hod. In ecen yea s, luid mechanics has exploi ed mo e and mo e measu ing me hods ha a e based on op oelec onic p inciples, using ligh . These me hods include, o example, LDA (Lase Dopple Anemome y), PDA (Phase Dopple Anemome y), PIV (Pa icle Image Velocime y) e c. Lase anemome y seems o be an ex emely exac ool o measu ing eal objec s. I s bene i is ha i is con ac less. I measu es a medium speed using mic oscopic pa icles ha a e di used in he medium. The measu emen is linea wi hin he whole ange. The esul s do no depend on he su ounding condi ions, such as p essu e, empe a u e, humidi y e c. P e iously, he labo a o ies o he TUL ha e al eady deal wi h expe imen al esea ch o mixing nozzles o ejec o s. The i s measu emen aced a big p oblem. A Pi o ube was used o a ec signi ican ly he ejec o unc ionali y. In addi ion, his a ec was no cons an , bu depended on he ube inse ion in o he mixing chambe . The esul ecalcula ion was necessa y. The nex expe imen al me hod o he low pa e n examina ion was he me hod o ho wi e (CTA me hod). Howe e , he CTA me hod did no allow o he measu ing o he low pa e n wi hou any objec in luence – he CTA p obe o he anemome e . The in e up ion o he low by he p obe led o a measu emen e o . 8 1 Lase Dopple Anemome y The LDA me hod is he mos commonly used mode n con ac less measu emen echnique o he esea ch o liquid low. I is bes sui ed o s udies o s a iona y low. Due o a small measu ing p obe i allows an ex ao dina y spa ial esolu ion. We ha e chosen his me hod o he a o emen ioned bene i s. 1.1 The LDA me hod p inciple LDA is a con ac less measu ing me hod ha exploi s he Dopple ’s e ec . LDA measu es a di e ence in equency o lase ligh di used on a pa icle ha is ca ied by he examined liquid. To measu e he equency change (Dopple ’s shi ) he he e odyne de ec ion is used, as shown in Fig. 1 Two lase beams in e sec a an angle o , hei in e sec ion c ea es an op ical p obe. On a pa icle, passing h ough he op ical p obe, wo ligh wa es all wi h a equency o , in he di ec ions o uni ec o s ei1 and ei2. [1] F ig. 1 He e odyne de ec ion scheme A de ec o de ec s he ligh , di used by a pa icle. This de ec o egis e s he di e en ial equency, so called Dopple ’s equency D. The Dopple ’s equency is p opo ional o he eloci y componen u. The eloci y componen u lies in he plane o he in e sec ed lase beams and i is pe pendicula o he cen al line o he angle , closed by he wo beams. The eloci y componen o he low is possible o e alua e om he Dopple ’s equency: , )2/sin(2 D u    (1) whe e  is anangle o he wo in e sec ed lase beams, u is a componen o a pa icle eloci y p ojec ed in o a di ec ion (ei2-ei1),λ is a wa eleng h o lase ligh . 9 1.1.1 Lase Dopple anemome e A basic a angemen o a lase Dopple anemome e in he di e en ial mode is shown in Fig. 2. The lase beam is led om a lase owa ds a di ide , which di ides he beam in o wo iden ical beams ha a e pa allel wi h he cen al line o he sys em. The ansmi ing/ ecei inglens ocalize hese beams in o a ocus poin . Wi hin he ocus poin an op ical p obe consis ing o he in e sec ion o he wo beams is c ea ed. A pa icle passing h ough his p obe di uses ligh . This ligh is led h ough op ics o a de ec o . Two wa es di used by he pa icle a e examined by he pho o-de ec o using he e odyne de ec ion. The pho o-de ec o is posi ioned in a so-called backsca e . This a angemen has conside able bene i s, o example, only one adjus men o he op ical ansmi ing and de ec ing pa is needed. The disad an age o his me hod is he low in ensi y o he di used ligh ; he e o e i is necessa y o use a su icien ly powe ul lase . The main ask o he pho o-de ec o is o ans e an op ical Dopple ’s signal o an elec ic signal and i s consecu i e ampli ica ion. The ou pu signal o he pho omul iplie is a cu en ha con ains in o ma ion o he measu ed eloci y. The aim o he e alua ing p ocesso o he LDA is o measu e he equency o he Dopple ’s peak. F ig. 2 Scheme o lase Dopple anemome e 1.1.2 Analysis o measu ed da a The ou pu o he measu emen a he posi ion o he op ical p obe is a se o Dopple ’s signals. These a e u he mo e con e ed o speed acco ding o o mula (1); he speed alues a e hen e alua ed by s a is ical analysis. In he LDA, hese s a is ics no mally p o ide o example a e age speed, s anda d de ia ion and u bulence in ensi y. 10 ,100*,)( 1 1 , 1 1 22 1u Tuuu N u N u N i i N i i        (2) whe e u is a e age speed,  is a iance and u T is u bulence in ensi y. 1.1.3 Limi s and impe ec ion o he LDA me hod Mos possibly, exac cu en measu emen , e enness o he measu ed medium sa u a ion wi h ace pa icles and hei p ope ies belong among he basic condi ions o co ec unc ionali y o he LDA. The limi ing condi ion o he LDA applicabili y is he de ia ion o cu en di ec ion om he measu ed eloci y componen . The band e o , “ idge bias”, is possible o elimina e success ully i using a B ag’s cell. The eloci y e o , “ eloci y bias”, is possible o elimina e i in oducing a weigh ing unc ion in e sely p opo ional o eloci y [1]. 2 Expe imen The expe imen was ca ied ou wi h a c oss nozzle (Fig. 3). F ig. 3 C oss nozzle [2] 2.1 Condi ions o measu emen The measu emen o he eloci y p o iles on he nozzle was pe o med a a p essu e o 2 kPa. A his p essu e o he lowing ai , we can expec a maximum eloci y o abou 60m/s om he nozzle. In conside a ion o his speed such ansmi ing/ ecei ing objec i es we e selec ed, so ha he maximum Dopple ’s equency would no exceed he maximum equency o app oxima ely 150MHz, which was possible o measu e wi h he used coun e (Dan ec company) . An objec i e wi h a ocal dis ance o 250mm was selec ed which ul illed he de ined condi ion. 2.2 Measu emen A lase Dopple ’s anemome e in ope a ion is shown in Fig. 4. The de ail displays he nozzle and objec i e, ocusing he lase beamson he ocal poin . The c ea ed ocal poin c ea es he op ical p obe. 11 F ig. 4 Op ical p obe wi h he nozzle 3 Resul s o he measu emen Indi idual eloci y p o iles o he nozzle we e measu ed using lase Dopple ’s anemome y om he nozzle ape u e up o 90mm/15mm, and om 90 mm up o 180mm/30mm. This means ha o one nozzle posi ion, en eloci y p o iles we e gained, based on hese p o iles he inal cha was d a ed. 3.1 C oss nozzle The c oss nozzle was measu ed using he LDA me hod in he basic posi ion (Fig. 5) and hen o a ed by 45° (Fig. 6). F ig. 5 The c oss nozzle wi h an indica ed posi ion o he measu ed eloci y p o ile F ig. 6 The c oss nozzle wi h an indica ed posi ion o he measu ed eloci y p o ile a e o a ing by 45° 1 2 Indi id u measu e F ig. 7 F ig. 8 u al posi io n e men esul Veloci y p Veloci y p n s o he n o s a e docu m p o iles o p o iles o o zzle show m en ed in h he c oss n o he c oss n o e d di e e n h e cha s i n o zzle in hei o zzle o a e d cha ac e i Fig. 7 and basic pos i d 45°. i s ics o h e Fig. 8. i ion. e low pa e e n. The 13 Conclusion The expe imen al esul s o he c oss nozzle in i s basic posi ion a e shown in he cha in Fig. 7. De o ma ion o he eloci y pa e n o one side was no ed. This de o ma ion was p obably caused by a de ec in manu ac u ing, o by wea . The nozzle de o ma ion caused ha he symme y o he low was dis u bed and he eloci y d opped om he poin o i s maximum. Wi h inc easing dis ance om he nozzle’s ape u e he eloci y was slowly dec easing, he low pa e n decayed, and he e o e he e was less and less de o ma ion o he eloci y p o ile o he nozzle. The de o ma ion had he bigges impac on he eloci y pa e n up o he dis ance o app oxima ely 2.5 imes he diame e o he nozzle. In he case o he measu emen o he c oss nozzle o a ed by 45°,no de o ma ion in luence on he examined ai low was de ec ed. The esul s o he measu emen a e shown in Fig. 8. No o he possible de o ma ion o he low pa e n was no iced. The measu ed low was, in his case, di e en especially in he shape o he co e, which was na owe han in he p e ious case. The ai low eloci ies we e almos iden ical in bo h measu ed cases. Li e a u e [1] KOPECKÝ, V.: Me ody Lase o é anemome ie mechanice eku in, T ibun EU 2008. [2] VÍT, T.; DANČOVÁ, V.; DVOŘÁK, V.: Expe imen al Fluid Mechanics, TU Libe ci 2006. ISBN 80-7372-141-4 ___________________________________________________________________________ Ing. Pe Dolejš 14 EXPERIMENTÁLNÍ VÝZKUM SMĚŠOVACÍ TRYSKY PRO EJEKTORY V om o článku jsou po o ná ány d ě polohy laloko i é ysky u čené p o směšo ací p oces ejek o u. Předmě em pokusů bylo expe imen ální zjiš ění cha ak e is ik p oudo ých polí křížo é ysky. Měření ychlos ních p o ilů ysky p obíhalo při laku 2 kPa. Jedno li é ychlos ní p o ily ysky byly měřeny od ús í ysky do 90mm po 15mm a od 90mm do 180mm po 30mm. P o jednu polohu ysky bylo edy změřeno 10 ychlos ních p o ilů, k e é pak y ořily ýsledný g a . Důleži ým hlediskem k dopo učení ysky p o směšo ání byly cha ak e is iky ychlos ních p o ilů křížo é ysky měřené ůzných polohách, k e é byly naměřené mode ní bezkon ak ní měřící me odou - lase o á Dopple o ská anemome ie. Na základě naměřených da jsou pod obně popsány ychlos ní p o ily křížo é ysky. Expe imen o áním byly zjiš ěny de ek y na křížo é ysce a edy i její ne hodnos p o směšo ací p oces ejek o u. EXPERIMENTALUNTERSUCHUNG ÜBER DIE MISCHDÜSE FÜR EJEKTOREN In diesem A ikel we den zwei Lagen de ü den Mischp ozess eines Ejek o s bes imm en Zackendüse e glichen. Ve suchsgegens and wa die expe imen elle Bes immung on Cha ak e is iken de S om elde de K euzdüse. Das Messen de Geschwindigkei sp o ile de Düse wu de un e einem D uck on 2 kPa du chge üh . Die einzelnen Geschwindigkei sp o ile de Düse wu den on de Düsenö nung bis zu 90 mm je nach 15 mm und on 90 mm bis zu 180 mm je nach 30 mm gemessen. Fü eine Düsenlage wu den 10 Geschwindigkei sp o ile gemessen, die dann das Enddiag amm bilden. Wich ige Gesich spunk ü die Emp ehlung eine Düse ü Mischung wa en die Cha ak e is iken de Geschwindigkei sp o ile de K euzdüse, die in e schiedenen Lagen un e Anwendung de mode nen kon ak losen Messme hode, Lase -Dopple -Anemome ie, gemessen wu den. Au g und de gemessenen Angaben we den die Geschwindigkei sp o ile de K euzdüse aus üh lich besch ieben. Du ch Ve suche wu den De ek e an de K euzdüse es ges ell , demzu olge is de en Anwendung ü den Mischp ozess des Ejek o s nich geeigne . EKSPERYMENTALNE BADANIE DYSZY MIESZAJĄCEJ DLA EJEKTORÓW W niniejszym a ykule po ównywane są dwa położenia dyszy k zywkowej p zeznaczonej do p ocesu mieszania w ejek o ze. P zedmio em p zep owadzonych p ób było ekspe ymen alne us alenie cech pól s umieni dyszy k zyżowej. Pomia y p o ili p ędkości wykonywano p zy ciśnieniu 2 kPa. Poszczególne p o ile p ędkości dyszy mie zono od wylo u dyszy do 90mm co 15mm o az od 90mm do 180mm co 30mm. Dla jednego położenia dyszy dokonano za em pomia ów 10 p o ili p ędkości, k ó e nas ępnie naniesiono na wyk es wyników. Is o ną kwes ią w zak esie zalecenia dyszy do mieszania były cechy p o ili p ędkości dyszy k zyżowej mie zone w óżnych położeniach, k ó ych pomia y zos ały wykonane p zy zas osowaniu nowoczesnej bezkon ak owej me ody pomia owej - lase owej Anemome ii Dopple owskiej. Na pods awie danych pomia owych szczegółowo opisano p o ile p ędkości dyszy k zyżowej. W wyniku p zep owadzonych ekspe ymen ów s wie dzono us e ki na dyszy k zyżowej, czyli nie jes ona odpowiednia dla p ocesu mieszania ejek o a.