Felix J. Förster

Design of a Focusing Schlieren Setup for Use in a Supersonic Combustion Chamber

Schlieren imagining is an often used technique to visualize shock and expansion waves in supersonic flows. While a conventional setup is sensitive to the entire light path between the imaging optics, the focusing Schlieren setup allows to select a specific focal plane normal to the optical axis for imaging due to its narrow depth of focus. In this paper, we present and analyze the performance of a focusing Schlieren system for application in the supersonic combustion test facility at the Institute of Aerospace Thermodynamics (ITLR).

Time resolved measurements in the Durham Cascade.

This paper describes investigations into unsteady flow phenomena in a high turning linear cascade with a nominal steady flow. Traditionally time averaged instrumentation is used in such a cascade. Detailed intermittency readings were taken inside the cascade using hot wires to highlight the detailed flow interactions of the passage vortex and the blade suction surface. A new fast response five hole probe was built and tested against a hot-wire. Time-accurate measurements taken using this probe allowed an evaluation of the error made by using a probe with limited frequency response for the cascade measurements. This evaluation showed significant deviations in loss for regions of high unsteadiness, for instance the passage vortex. The Reynolds stress tensor was measured at 101%, 115% and 128% axial chord and the deformation work was calculated for 126% axial chord. The deformation work shows regions of negative values and positive values. While negative values are associated with a production of turbulent k.e. from the mean kinetic energy, positive values may represent a gain of kinetic energy from the turbulence.Copyright

Design and Validation of an Uncooled Pitot Probe for Hot, Supersonic Flow Investigations

A detailed understanding of supersonic free jets and the underlying flow phenomena is key to many technical applications such as exhaust nozzle flows of aircraft or rocket engines, or for well-defined test cases in the validation process of numerical setups. In this paper, we suggest an uncooled, low-cost pitot probe made from a high perfomance metall alloy. The paper describes the design of the probe, the obstacles during the manufacturing process and presents validation and application cases for free jets with an inlet total temperature of up to 1100K.

Characterization of a High Temporal Resolution TDLAS System for Measurements in a Shock Tube Facility

Transient heating and pressurization of a gas by shock waves can be useful for a variety of purposes, particularly for configurations involving shock wave focussing. Unless the geometry is particularly simple, the time history of temperature can be difficult to predict accurately. Hence, a non-intrusive measurement technique with high temporal resolution is required to record the time history of the very rapidly changing temperature of a shock-heated flow. One promising measurement techniques for these high-speed flows is Tunable Diode Laser Absorption Spectroscopy (TDLAS)

Reconstruction of the Unsteady Pressure Field in a Low Speed Linear Cascade

This paper describes investigations into unsteady flow phenomena in a high turning linear cascade with a nominal steady flow. A fast response five hole probe was used to obtain time-accurate measurements. Since a single probe was used to traverse an entire measurement plane, the results were obtained as discrete points and were not synchronous. One method used to address this issue is to traverse the measurement plane point by point and record the signal of a reference probe simultaneously. Synchronization can be performed during post processing by analyzing the reference signal for a common periodic component and phase-shifting all signals with respect to the reference phase of that flow feature. This paper presents results from the application this unsteady reconstruction technique to the so-called Durham Cascade 28% downstream of the trailing edge in order to provide insight into the nature of the dominant unsteady mode. It was found that there was significant temporal variation in the strength of the passage vortex but the position of the vortex remains fixed.