İTÜ 150x150 mm trisonik rüzgar tüneli kalibrasyonu ve bazı deneyler
Başlık çevirisi mevcut değil.
- Tez No: 75188
- Danışmanlar: PROF. DR. ZEKİ ERİM
- Tez Türü: Yüksek Lisans
- Konular: Uçak Mühendisliği, Aeronautical Engineering
- Anahtar Kelimeler: Kalibrasyon, Rüzgar tüneli, Calibration, Wind tunnel
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Uçak Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
ÖZET Rüzgar tünelleri atmosfer içinde hareket eden uçak, helikopter, roket, mermi gibi uçan sistemlerle araba, otobüs ve raylı sistemler gibi karada hareket eden araçların deneysel olarak incelenmesine olanak sağlayan uçak mühendislerinin temel laboratuarlarıdır. Rüzgar tünelleri çalışma hızlarına göre düşük ses altı, yüksek ses altı, transonik, ses üstü ve hipersonik tüneller olarak sınıflandırılırlar. İTÜ 150x150 mm Trisonik Rüzgar Tüneli, iki değiştirilebilir kesiti sayesinde ses altı, transonik ve ses üstü hızlarda deneyler yapılmasına olanak tanıyan bir rüzgar tünelidir. Rüzgar tünellerinin kalibrasyonu yapılacak deneysel çalışmaların güvenilirliği açısından son derece önemlidir. Bu çalışmada ilk başta İTÜ Uçak ve Uzay Bilimleri Fakültesi Aerodinamik Laboratuarında bulunan 150x150 mm kesitli deney odasına sahip trisonik rüzgar tünelinin genel donanımı ve ölçüm sistemleri tanıtılmaktadır. İkinci aşamada rüzgar tünelinin kalibrasyonu için yapılan çalışmaların sonuçlan verilmektedir. Verilen sonuçlar bazen tünel performans büyüklükleri veya parametreleri ismiyle de tanımlanmaktadır. Tünel performans büyüklüklerinin tespiti için deney odasında statik basınç dağılımı ve toplam basınç değişimini içeren basınç ölçümleri, tünel hız ölçüm güvenilirliğinin tespiti için akım görünürlülüğü ve bir standart modele ait kuvvet ve moment ölçümleri yapılmıştır. Bu deneyler, İTÜ Trisonik Rüzgar Tünelinin performans parametreleri hakkında önemli bilgiler elde edilmesini ve yeni ölçüm sistemlerinin geliştirilmesi gerektiğinin anlaşılmasını sağlamıştır. Bu değerlendirme sonucunda İTÜ 150x150 mm Trisonik Rüzgar Tünelinin yüksek hızlarda bilimsel çalışmalara uygun olduğu sonucu elde edilmiştir. vi
Özet (Çeviri)
SUMMARY CALIBRATION OF ITU 150x150 mm TRISONIC WIND TUNNEL AND SOME EXPERIMENTS Wind tunnels are devices which provide an airstream flowing under controlled conditions so that items of interest to speeds as low subsonic wind tunnels (incompressible flow), high subsonic wind aeronautical engineers can be tested. Wind tunnels can be classified according to their operating tunnels (subsonic compressible flow), transonic wind tunnels, supersonic wind tunnels and hypersonic wind tunnels. İTÜ 150x150 mm Trisonic Wind Tunnel can operate at subsonic, transonic and supersonic speeds. Before carrying out experimental research, determining the characteristics and calibration of a wind tunnel is of vital importance. Wind tunnels having different operating speeds need different calibration techniques. Pope [1] has stated that the calibration of a supersonic wind tunnel includes determining the Mach number, flow angularity and turbulence level in the wind tunnel. Weinert [3] has shown how investigations of Mach number and flow-angle distributions at supersonic Mach numbers were carried out with pitot rakes and a combined calibration rake for measuring flow angularity in the test section of the high speed wind tunnel TVM 150 at the Aeronautical Institute of the Technical University of Darmstadt. Calibration and determining the performance of İTÜ 150x150 mm Trisonic Wind Tunnel is carried out according to what is indicated in Pope's book [1]. In this study, firstly İTÜ 150x150 mm Trisonic Wind Tunnel and measurement systems are introduced. Secondly the study based on the calibration works including flow visualization, pressure and especially force measurements carried out on the İTÜ 150x150 Trisonic Wind Tunnel are explained in detail. Force measurements are accepted as a separate methodology for the completion of wind tunnel calibration. Visualization experiments to obtain the flow speed and quality within the test chamber are also accepted as another method for the verification of the calibration. Pressure measurements, force measurements and flow visualization applications on standard models have shown the reliability of the measurement apparatus.İTÜ 150x150 mm TRISONIC WIND TUNNEL İTÜ 150x150 mm Trisonic Wind Tunnel-an intermittent blowdown wind tunnel with variable Mach number-is designed for investigations in the subsonic, transonic and supersonic flow ranges of Mach numbers from 0.3 to 4. It has two different test sections for different Mach ranges. The first test section is used for obtaining Mach numbers from 0.3 to 2.2 and the second one is used from 2.6 to 4 Mach number. The installation works as a high pressure storage plant in an intermittent manner. There are two pressure storage units each having a volume of 27m3. They are charged to a pressure of 40 bar by means of a compressor plant coupled with a air drying and filtration unit. During experiments the needed pressurised air is supplied to the stagnation chamber through a regulation valve. The regulation valve maintains a constant pressure inside of the stagnation chamber whereas the reservoir pressure varies during the test run. A schematic figure of the ÎTÜ 150x150 mm Trisonic Wind Tunnel is shown in Figure 1. MEASUREMENT SYSTEMS Measuring times are limited for blowdown tunnels, for this reason a highly qualified data processing and control unit is required. Test runs at the 150x150mm İTÜ Trisonic Wind Tunnel are computer controlled and measurements are obtained through a data acquisition system. Total pressure and total temperature in the settling chamber and static pressure at the upper test section wall are evaluated by means of transducers and thermocouples attached to the system via an AD/DA data acquisition unit. A scanning valve can be used to measure pressures from 48 channels. Wind Tunnel Balances Wind tunnel balances are used to measure forces and moments acting on a model directly. The main characteristic of wind tunnel balances is the number of measured components. Depending on the problem, this number can vary from 1 to 6 [5]. They can be classified according to their components, measuring system - mechanical or strain-gaged and location - inside the model or inside the support. Wind tunnel balances must be calibrated to obtain a calibration matrix before measuring forces and moments. Calibration is done by applying known loads in the direction of each component. By this way Kij calibration matrix coefficients are evaluated. Calibration matrix is used according to the following equation to obtain axial force, normal force and pitching moment when Vij voltage values are measured during experiments. vX N M K" Km K n K. K A three component sting type strain-gage electronic balance is used in İTÜ 150x150 mm Trisonic Wind Tunnel to measure lift, drag force and pitching moment at various angles of attack. CALIBRATION WORKS Calibration of the İTÜ Trisonic Wind Tunnel has been carried out in three steps : determination of total and static pressure distribution within the test chamber, determination of free stream Mach number by flow visualization method, force and moment measurements on standard models. Pressure Measurements Tracking a pitot tube and a static tube along a vertical section of the test chamber, total and static pressure distributions are evaluated in two different Mach numbers - M=2.67 and M=3.13 - having intervals of 20mm at 7 vertical stations. In Figure 5 the ratio of the difference between measured total pressure in one station and average value of the total pressures measured in different stations, and total pressure in the settling chamber is given. It is obtained that the total pressure distribution is satisfactory. In Figure 6 the same ratio is evaluated for static pressures. In addition, static pressures are measured both from the upper and lower walls of the 2.6<M<4.0 test section and are compared with each other. Pressure distributions are found satisfactory and a minor difference has been detected between the pressure values obtained from the lower and upper walls. Flow Visualization Flow visualization has been made on 15° nose angle conical model at zero angle of attack by means of the Schlieren system. Angle of the oblique shock wave formed on the front of the model has been measured and Yükselen [8] has used this for evaluating the free stream Mach number theoretically, which is then compared with the Mach number given by the data acquisition system of the wind tunnel. As an example in Figure 7. Schlieren photographs of the conical model are given at M=2.804 and M=3.078. Angle of the shock waves are measured 22° and 20° from these photographs respectively. Shock wave angles have been used to obtain free stream Mach number of 2.783 and 3.074 respectively. The two values have been found in good agreement. IXForce And Moment Measurements Force and moment measurements in İTÜ 150x150mm Trisonic Wind Tunnel can be carried out using the internal strain-gage balance. Before evaluating the force and moment data, the balance is calibrated. A specific calibration system is used for applying loads and the voltage values are obtained by using the program called CALIBRATION. After evaluating Kij calibration matrix coefficients calibration matrix is formed. Force and moment measurements on a cylindrical body with a conical nose have been made using the 3 component sting-type electronic balance at various angles of attack. This model has been selected for enabling comparison with the well-known force data given by Landrum and Babb at the NASA Technical Memorandum 78813, [7]. The data of M=2.96 are used for comparison. As it is stated by Landrum and Babb [7] the data should be evaluated with the estimated accuracy's, based on 0.5 percent balance accuracy given in the memorandum. r/l = 0.16667x/l (0<x/l<0.45) r/l = 0.075 (0.45<x/l<1) The model has been manufactured according to the formula given above, r is the model body radius, 1 is the body length and x is the longitudinal distance along body, measured from nose. Two models used in these experiments are given in Figure 3 and 4. Axial force, normal force and pitching moment coefficients of the model given in the memorandum is shown in Figure 9 and in Figure 10 estimated accuracy's is shown. In Figure 11 at M=2.85 axial and normal force and pitching moment coefficients is given in comparison with the NASA report. Axial force and pitching moment coefficients are found to be different. This difference originates from the model geometry and wind tunnels. The second model is used for obtaining more accurate results. The coefficients of the second model is given in Figure 12. Only axial force coefficient shows a difference. RESULTS AND ANALYSIS 1. Static pressures measured both from the upper and lower walls of the 2.6<M<4.0 test section are found to be in good agreement. So measuring static pressure from the upper wall in the test section during experiments is suitable. 2. Total and static pressures measured by tracking a pitot tube and a static tube along a vertical section of the test chamber, in two different Mach numbers -M=2.67 and M=3.13 - having intervals of 20mm at 7 vertical stations has shown acceptable results for future experiments. On the other hand the measurement systems should be developed for obtaining total and static pressures at different sections, such as a pitot rake used by Weinert [3]. 3. Mach number evaluation of the flow in the test section by means of the Schlieren system using 15° nose angle conical model at zero angle of attack has shown that the Mach number measured during experiments are suitable. 4. Axial force, normal force and pitching moment are measured on the model given by Landrum and Babb [7] with a three component sting type internal balance for evaluating the coefficients. The axial force, normal force and pitching moment coefficients are found satisfactory when compared with the NASA Memorandum within the estimated accuracy. 5. Axial force coefficient has shown a slight difference. The reason for this is the roughness on the model surface and junction area. Manufacturing smooth models for the experiments in the wind tunnels have an important role in the accuracy of the experiments. 6. All of the evaluations explained above are regarded as the performance parameters of the 150x150 mm trisonic wind tunnel and proved its reliability in experimental research. XI
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