Performance comparison of background-oriented schlieren and fringe deflection in temperature measurement: part I. Numerical evaluation

A new technique using background oriented schlieren for temperature reconstruction of an axisymmetric open reactive flow

“…where r i is the outer radius of ring i. Solving equations ( 7) and (8) for their intersection point results in a quadratic equation that gives two points. Due to the placement of the origin, the coordinate pair with the lesser z value is taken as the valid intersection point on the background side and labeled (z bg,i , y bg,i ).…”

“…Having full field accurate temperature data within these systems is crucial as overall gas turbine engine efficiency is dependent on the combustion chamber exhaust/turbine inlet temperature profile, harmful emission levels are dependent on peak combustion temperature, and identifying hot spots on the combustor liner leads to more targeted, efficient cooling designs. Significant effort has been made to experimentally measure the temperature throughout reactive flows using noninvasive approaches such as planar laser induced fluorescence (PLIF) [1][2][3][4][5][6], interferometry [7,8], conventional knife edge schlieren [9], and rainbow schlieren [10,11]. All of these techniques require complex optical setups to maneuver the specific laser or light source used, and either multiple or a tunable high powered laser is required to isolate a temperature dependent signal in PLIF.…”

“…The Gladstone-Dale relation is a direct relationship between refractive index and density, so it naturally follows that numerous studies have used BOS to measure the density field of variable density flows [12][13][14][15][16][17][18][19]. By also utilizing the ideal gas law, direct relationships between refractive index and temperature can be formulated as well [8,12,16,20,21].…”

Temperature reconstruction of an axisymmetric enclosed reactive flow using simultaneous background oriented schlieren and infrared thermography

“…Traditionally, temperature is simply measured with discrete thermocouple probes, however it is difficult for these probes to survive these systems due to the high energy levels present as well as the fact that thermocouples can be visibly observed to act as a flame holder when exposed to reactive flows, changing the flow dynamics. For this reason, noninvasive approaches are required for feasible full field temperature measurements, and several of these techniques used for measuring various flow parameters (temperature, density, mixture fraction, species concentration, etc) exist such as planar laser induced fluorescence (PLIF) [1][2][3][4][5][6][7][8][9], interferometry [10][11][12], and schlieren imaging. Schlieren imaging can be categorized further into conventional knife edge schlieren [13], rainbow schlieren [14,15], and BOS [11,[16][17][18][19][20][21][22][23][24][25][26][27][28].…”

“…For this reason, noninvasive approaches are required for feasible full field temperature measurements, and several of these techniques used for measuring various flow parameters (temperature, density, mixture fraction, species concentration, etc) exist such as planar laser induced fluorescence (PLIF) [1][2][3][4][5][6][7][8][9], interferometry [10][11][12], and schlieren imaging. Schlieren imaging can be categorized further into conventional knife edge schlieren [13], rainbow schlieren [14,15], and BOS [11,[16][17][18][19][20][21][22][23][24][25][26][27][28]. Of these techniques, BOS is by far the simplest and most inexpensive to implement experimentally making it an attractive choice for researchers if it can be developed to the maturity of more established quantitative techniques such as PLIF, and in fact the purpose of this current work is to aid in this process.…”