Recent developments and applications of quantitative laser light sheet measuring techniques in turbomachinery components

Abstract

Concerning the further development of gas turbine engines, advances of the aero-thermodynamic design can be achieved most efficiently by cooperative efforts aimed at the improvement of both the numerical simulation methods and the experimental test and measurement techniques. Rapid development of numerical capability is accompanied by increasing demands on experimental data. In this context significant instrumentation research efforts are being conducted to develop the needed measurement technologies. Because of the need for reduced experimental costs planar measurement techniques have undergone a rapid pace of development. Three newly developed quantitative light sheet techniques utilizing the scattered light of tracer particles are described in this paper. First a Doppler global velocimetry (DGV) system optimized for time-averaged three component velocity measurements is presented. The system, which uses a single viewing direction in conjunction with three different illumination directions enables very accurate velocity measurements. Second a quantitative light sheet (QLS) technique for quantitative mass fraction measurements in mixing processes is treated. To apply the technique the inflow of the mixing experiment must consist at least of two separate flows, one of which can be seeded while the other remains unseeded. DGV and QLS results obtained from experimental investigation in a model combuster are presented. Third a method named tracer-based shock visualization (TSV) is described which is capable of determining the shape and structure of shock waves in transonic flows by analysing the sudden increase of flow density across a shock. Results taken in a transonic compressor are presented.

Formation and flame-induced suppression of the precessing vortex core in a swirl combustor: Experiments and linear stability analysis

“…While the density is approximately uniform for the non-reacting case A, the reacting cases B and C exhibit strong density variations due to thermal expansion of the unburned gas. For these cases the density was determined using the quantitative light sheet (QLS) technique [19,40,49]. As the QLS technique derives the density from the Mie scattering signal of the PIV particles, the particle images recorded for the velocity measurements were used for the density estimation.…”

Impact of Steam-Dilution on the Flame Shape and Coherent Structures in Swirl-Stabilized Combustors

“…The QLS technique is mainly used as an alternative to laser induced fluorescence (LIF) measurements for mixing experiments, where the flow is only partly seeded (Findeisen et al 2005;Roehle et al 2000;Voigt et al, 1997). However, the principle is transferrable to density measurements in a homogeneously seeded flow.…”

Residence Time Distribution in a Swirling Flow at Nonreacting, Reacting, and Steam-Diluted Conditions

“…Mie scattering of a particle is proportional to its surface. Assuming a constant particle size distribution, the scattered light is proportional to the local particle concentration [21],…”