Bir yan akım içindeki türbülanslı jet akışının deneysel olarak incelenmesi
Experimental investigation of turbulent jet stream in a crossflow
- Tez No: 39771
- Danışmanlar: PROF.DR. OKTAY ÖZCAN
- Tez Türü: Yüksek Lisans
- Konular: Astronomi ve Uzay Bilimleri, Astronomy and Space Sciences
- Anahtar Kelimeler: Akış karakteristiği, Türbülanslı akış, Flow characteristic, Turbulent flow
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Bir yan akım içindeki jetin incelenmesi, mühendislikteki uygulama alanının çokluğu bakımından önem taşımaktadır.Bunun için, bir takım deneyler ve analizler yapılarak akım özellikleri hakkında bilgi edinilmesi gerekmektedir. Bu tezde yapılan çalışmalar deneylerin yapıldığı rüzgar tünellerine göre ikiye ayrılabilir: 1) İ.T.Ü Trisonik Laboratuvan 50x50 cm kesitli deney odasına sahip sesaltı tünelde yapılan "deneyler: Akım görünürlüğü deneylerinde gaz yağı-kömür tozu karışımı yöntemi kullanılarak jet çıkışı civarındaki yağ birikme çizgileri gözlenmiştir. Deney 64 m/s sabit jet hızında, 10, 20, 24 m/s' lik üç değişik yan akım hızında tekrarlanarak yağ birikme çizgisi mesafelerinin değişimleri ölçülmüştür. Basınç ölçümü deneylerinde 20 m/s sabit yan akım hızında, jet çalışırken ve çalışmazken, 180 derecelik bir alanda 10* ar derece arayla statik basınç ölçümleri yapılmıştır ve eşbasınç eğrileri elde edilmiştir. 2) İ.T.Ü Trisonik Laboratuvan 30x60 mm kesitli deney odasına sahip sesüstü tünelde yapılan deneyler: Akım görünürlüğü deneyinde yağ metodu kullanılarak 2.2 Mach hızındaki yan akıma enjekte edilen 4 bar başmandaki bir jetin yüzey akım görünürlüğü fotoğrafi alınmıştır. Statik basınç ölçümü ve sıcaklık ölçümü deneylerinde de 2.2 Mach hızındaki yan akıma enjekte edilen 1.75, 3.70, 5.45 bar geri başmandaki jetin etrafındaki sıcaklıklar ve basınçlar ölçülmüştür. Statik basınç ölçümleri sonucunda, yan akımdaki jetin, ön tarafinda pozitif arka tarafinda ise negatif bir basınç alanının oluştuğu, akım görünürlüğü deneylerinden de jetin ön tarafinda ayrılma arka tarafında ise yeniden yapışma çizgilerinin oluştuğu görülmüş, sesüstü akım için özel olarak jetin önünde iki tane ayrılma çizgisi oluştuğu görülmüştür. Sıcaklık ölçümlerinden sesüstü yan akımdaki jetin etrafında önemli bir sıcaklık değişimi olmadığı görülmüştür.
Özet (Çeviri)
SUMMARY EXPERIMENTAL INVESTIGATION OF TURBULENT JET STREAM IN A CROSSFLOW Jets in a crossflow is one of the important problems for fluid mechanics and have many field of engineering application, including thrust vector control in aerospace vehicles, fuel injection of supersonic combustion ramjets, cooling of blade elements in turbomachinery, VTOL (Vertical Take-Off and Landing) aircrafts and waste disposal into atmosphere and water. Experimental investigations about jets in a crossflow can be made ina wide range of varieties because of the oppotunity of changing many parameters. Some of them are: -Jet velocity -Crossflow velocity -Jet diameter -Injection angle -Number of jets -Jet fluid -Shape of jet exit In previous investigations jets in crossflow had been observed for these parameters. These investigations can be classified into two groups as subsonic and supersonic. In [1] and [2], jet in a subsonic crossflow has been investigated by the pressure distribution curves around the jet.In [3], turbulence measurements of a jet in a subsonic crossflow has been realized. In [4], interaction of a jet injected into a supersonic crossflow has been analyzed for thrust vector controls and the force induced on an adjacent wall has been estimated. In [5] and [6], jet enjected into a crossflow has been observed, providing flow visualization by Schlieren method and static pressure distribution. In [7], supersonic jet in a supersonic crossflow has been investigated and the injection has been stated be more related to the momentum rate rather than jet Mach number, VIpressure rate and density rate. In [8], jet in a supersonic stream has been studied in the manner of shock wave-boundary layer interaction. Investigations made for this study may be departed as two for the wind tunnels that the experiments have been realized: 1) İ.T.Ü Trisonics Laboratory, subsonic wind tunnel with 50x50 cm test section : Flow visualization and static pressure measurements. In experiments for this part, air from an electro compressor by a rubber trunk has been passed through a convergent nozzle for vertical injection into the cross flow in the test section. Nozzle section is a third degree curve (r = a + bx + cx2 +dxi) providing the boundary conditions. In order to measure static pressure around the jet, a circular plexiglass rotating plate placed in the test section has been manufactured. A hole for jet nozzle has been opened into the center and 34, 1.2 mm diameter pressure probes have been drilled in the radial direction. As only first 20 probes showed some difference in pressure measurements at the first few experiments, the rest haven't been used in the remaining tests. Figure 1. Jet in a crossflow y^ vuTunnel wall(top) l\V\V\\\\S.\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\^VVV\\\K V^^l Crossflow direction IU\\\\\U\\\\U',\v\\\\V\\\\\ ^^m m fu'iTTn I y y '' /"<i / y ir*r*r^ Tunnel wall(bottom) Turntable ( plan view Pressure probes Figure 2. Experimental arragament in subsonic wind tunnel. Rotating plate have been manufactured to rotate 360 degrees by the screw holes drilled by 10 degrees step. Screw holes haven't been extended in to the surface in order not to spoil the flow. As pressure measurements static pressure has been obtained for a 180 degrees field in 10 degrees step for and without jet stream in 20 m/s constant crossflow. Results have been converted into isobaric curves of surfaces by SURFER computer program. Symmetry in the event has been assumed to exist and extension for 360 degrees has been obtained. These curves have been showed that Cp increase along x axis, there is a positive pressure distribution in front of the jet and negatif backward. The changes in the static pressure distribution occurs around the jet exit about 4.7 diameter. VMAs flow visualization, gasoline-coal powder method for observations of oil segregation paths around jet exit has been used. For 64 m/s constant jet velocity, changes in distances of secretions from each other for three different crossflow velocity of 10, 20, 24 m/s have been measured. According the results, seperation line distances (A, B, C) increase with crossflow velocity for constant jet velocity. 2 ) İ:T:Ü Trisonics Laboratory, 30x60 mm test section supersonic wind tunnel: Flow visualization, static pressure measurements, temperature measurements. Air taken from 0-10 bar compressor by a trunk have been injected into the crossflow of test section through divergent-constant area- convergent nozzle section Convergent section of the nozzle a third degree curve (r = a + bx + cx2 +dx3) providing the boundary conditions. For this test set up, test section cover manufactured by Yüceil [11] previously used with necessary arrangements. This cover can be rotated by fixing into the test section by the help of 10 degree step drilled holes in the edge. A smooth surface have been obtained by covering the holes drilled for model installation on the cover, using adhesives. Then the hole for jet nozzle has been drilled at the center of the cover. In the radial direction 22 pressure probe holes on one side and 10 thermocouple holes on the other has been drilled. First 5 pressure probes have been observed to measure differences in the first few test, so in the remaining tests, the rest has been canceled. 1, 4, 7 and 10th thermocouple probes have been used for tests. M- Figure 3. Seperation lines around the jet in a supersonic crossfllow IXFor pressure measurements, static pressures have been obtained for 0, 90 and 180 degrees radial alongations at 1.75, 3.70 and 5.45 plenum bars of jet streams in 2.2 Mach constant cross flow velocity. Results have been showed the changes in the static pressure around the jet occurs 7 jet diameter.
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