Walter Beck

Experimental Study of a Scramjet Nozzle Flow Using the Pressure-Sensitive-Paint Method

An experimental study on scramjet nozzle flows was carried out at the German Aerospace Center. The tests were performed at a free-stream Mach number of 7 in the hypersonic wind tunnel H2K in Cologne. The Reynolds number in the tunnel flow was varied in order to study the performance of the scramjet nozzle at different flight altitudes. The effects of different nozzle pressure ratios were investigated and compared. The static pressure distribution on the single expansion ramp was measured by both the Pressure-Sensitive Paint (PSP) Method and PSI pressure transducers. The PSP method enables one to gain detailed field information about the pressure distribution on the entire nozzle surface. A Pitot rake was used to measure the Pitot pressure distribution in the nozzle wake. The data obtained by the different measurement techniques permitted a characterization of the nozzle flow and gave an insight into the properties of scramjet nozzle flows.

Measurement of Flow Properties and Thrust on Scramjet Nozzle Using Pressure-Sensitive Paint

An experimental study of flows over a single expansion ramp nozzle with flush-mounted side walls was carried out at the DLR, German Aerospace Center. The tests were performed at a freestream Mach number of 7 in the hypersonic wind tunnel H2K in Cologne. The Reynolds number and nozzle pressure ratios in the wind-tunnel flow were varied to study the performance of the scramjet nozzle at different flight altitudes and run conditions. The static pressure distribution on the single expansion ramp was measured by both the pressure-sensitive paint method and by using pressure transducer taps located at discrete points on the surface. These two methods showed that the nozzle pressure ratio and the freestream Reynolds number do not substantially influence the static pressure ratio on the expansion ramp. A pitot rake was also used to measure the pressure distribution in the nozzle wake. Using this technique the nozzle flow in the wake could be visualized and the strong influence of the nozzle pressure ratio on the interaction between nozzle and external flows was revealed. The data obtained by the different measurement techniques permitted a characterization of the nozzle flow and gave insight into the properties of single expansion ramp nozzle flows. The thrust generated by the nozzle, the thrust efficiency coefficient, and the thrust vector angle were calculated by using the pressure data obtained by both pressure measurement techniques and the results compared. It was shown that thrust values obtained from pressure tap measurements were overestimated. Criteria were developed to aid in the design and optimization of the thrust-related performance criteria for this single ramp nozzle.

Application of Temperature and Pressure Sensitive Paints to DLR Hypersonic Facilities: “lessons learned”

PSP and TSP measurements have been carried out on the following DLR facilities: small test shock tube, High Enthalpy Shock Tunnel (both in Gottingen) and the Hypersonic Wind Tunnel (in Cologne). Based on the results from these measurements, various challenges and problem areas could be identified: the role played by these in hindering a quantitative application of PSP/TSP to the facilities is discussed, and ways and means are presented for either overcoming them or at least ameliorating their influence.

Experimental Study of the Interaction between Internal and External Flows of a Scramjet Nozzle using Various Diagnostic Techniques

In the framework of a graduate student research group financed by the German National Research Council (DFG), an experimental study on nozzle flows was carried out at the German Aerospace Center (DLR). The tests were performed at a free-stream Mach number of 8 in the H2K wind tunnel at the DLR in Cologne. The Reynolds number was varied in order to simulate the influence of different flight altitudes of a scramjet vehicle. The effects of different nozzle pressure ratios have been investigated and compared. The static pressure distribution on the single expansion ramp was measured by the Pressure-Sensitive Paint (PSP) Method and PSI pressure transducers. A Pitot rake was used to measure the Pitot pressure distribution in the nozzle wake. Schlieren photographs are also used to investigate the flow field. The experimental results are discussed and compared with CFD calculations.

Measurement of an Oscillating Shock Wave in a Transonic Flow Using Two Different Pressure Sensitive Paints* (*Ru-based on anodized aluminum vs. Pt-based with screen layer)

The performance of two different PSP used at DLR and ONERA is compared by carrying out bench mark testing using the oft-studied configuration of an oscillating shock wave (up to 100 Hz) on a bump in the Mach 1.4 flow of the ONERA S8Ch wind tunnel. The shock is made to oscillate by rotating a cam with elliptical cross section, placed at a further downstream position, at frequencies of 15, 30 and 50 Hz. Both paint types are well known and much has been published on their use: the ONERA PSP is a Ruthenium complex Ru(dpp)_3Cl_2 placed as a thin layer on an anodized aluminum substrate, while the DLR PSP is a Platinum complex PtTFPP on a base coating containing TiO_2 particles. S8 run conditions were held constant, and separate test run series were carried out with each paint. Instationary calibration was also carried out using a special test rig. Fourier analyses of the PSP results in S8 enabled a semi-quantitative comparison of the time response of both paints. This is the first published attempt (to the authors’ knowledge) of carrying out a side-by-side comparison of the characteristics of these two paints on such a flow configuration in a wind tunnel. Particular emphasis is placed on their handling properties and, above all, their time responses.