Spray Flame Characterization of the CORIA Rouen Spray Burner (CRSB) using Optical Diagnostics

Abstract

Este trabalho teve como objetivo desenvolver e validar uma bancada experimental para o CORIA Rouen Spray Burner (CRSB) e caracterizar a chama produzida por meio de técnicas de diagnóstico óptico. O CRSB é um queimador atmosférico equipado com um injetor simplex DANFOSS e um plenum para geração de co-escoamento de ar. Para sua operação, um sistema de injeção completo foi projetado e montado em uma placa de aço, integrando medidores de vazão, uma bomba e uma interface LabVIEW para controle dos componentes. Com o objetivo de reproduzir as condições de baixa temperatura encontradas em voo de alta altitude, um sistema de resfriamento baseado em um circulador refrigerado Julabo FP50-HE e um trocador de calor foi integrado à bancada. O sistema foi capaz de reduzir a temperatura do combustível a −20 °C na entrada do queimador; no entanto, medições próximas ao injetor indicaram que as perdas térmicas internas ao queimador são não negligenciáveis, impedindo que temperaturas subzero fossem atingidas no ponto de injeção. Para caracterizar a chama, duas técnicas de diagnóstico óptico foram aplicadas: a quimiluminescência e a Anemometria Laser Doppler (LDA). A quimiluminescência, utilizando uma câmera ICCD Teledyne PI-MAX 4 com filtro BG12, permitiu determinar a geometria e a altura de levantamento da chama para n-heptano e n-decano. Os resultados mostraram alturas de levantamento de 22,56 mm e 21,52 mm para n-heptano (pelos métodos de média simples e RMS, respectivamente) e de 23,20 mm para n-decano em ambos os métodos, indicando maior estabilidade desta chama. A LDA, utilizando um sistema DANTEC comercial, forneceu perfis de velocidade tridimensionais em seis posições axiais. Os perfis obtidos são coerentes com resultados reportados na literatura para o mesmo queimador, validando a bancada montada. As principais limitações identificadas dizem respeito à impossibilidade de atingir temperaturas de injeção subzero com a configuração atual, sendo necessária uma modificação geométrica do CRSB para permitir o resfriamento de todo o sistema de injeção.

Abstract: This work aimed to develop and validate a test bench for the CORIA Rouen Spray Burner (CRSB) and to characterize the flame it produces using optical diagnostic techniques. The CRSB is an atmospheric burner equipped with a DANFOSS simplex fuel injector and a plenum for generating an air co-flow. To operate the burner, a complete injection system was designed and assembled on a steel plate, integrating flowmeters, a pump, and a LabVIEW interface for component control. With the objective of reproducing the low-temperature conditions encountered during high-altitude flight, a cooling system based on a Julabo FP50-HE refrigerated circulator and a heat exchanger was integrated into the setup. The system successfully brought the fuel temperature to −20 °C at the burner inlet; however, temperature measurements near the injector indicated that internal thermal losses within the burner are not negligible, preventing subzero temperatures from being achieved at the injection point. To characterize the flame, two optical diagnostic techniques were applied: chemiluminescence imaging and Laser Doppler Anemometry (LDA). Chemiluminescence imaging, using a Teledyne PI-MAX 4 ICCD camera with a BG12 bandpass filter, allowed the determination of flame geometry and lift height for n-heptane and n-decane flames. Lift heights of 22.56 mm and 21.52 mm were found for n-heptane using the simple averaging and RMS methods, respectively, while n-decane yielded 23.20 mm for both methods, indicating greater flame stability. The LDA measurements, performed with a commercial DANTEC system, provided three-dimensional velocity profiles at six axial positions. The obtained profiles are coherent with results reported in the literature for the same burner, confirming the validity of the assembled setup. The primary limitation identified is the inability to achieve subzero injection temperatures with the current configuration; a geometric modification of the CRSB would be required to allow cooling of the entire injection system.

This work aimed to develop and validate a test bench for the CORIA Rouen Spray Burner (CRSB) and to characterize the flame it produces using optical diagnostic techniques. The CRSB is an atmospheric burner equipped with a DANFOSS simplex fuel injector and a plenum for generating an air co-flow. To operate the burner, a complete injection system was designed and assembled on a steel plate, integrating flowmeters, a pump, and a LabVIEW interface for component control. With the objective of reproducing the low-temperature conditions encountered during high-altitude flight, a cooling system based on a Julabo FP50-HE refrigerated circulator and a heat exchanger was integrated into the setup. The system successfully brought the fuel temperature to −20 °C at the burner inlet; however, temperature measurements near the injector indicated that internal thermal losses within the burner are not negligible, preventing subzero temperatures from being achieved at the injection point. To characterize the flame, two optical diagnostic techniques were applied: chemiluminescence imaging and Laser Doppler Anemometry (LDA). Chemiluminescence imaging, using a Teledyne PI-MAX 4 ICCD camera with a BG12 bandpass filter, allowed the determination of flame geometry and lift height for n-heptane and n-decane flames. Lift heights of 22.56 mm and 21.52 mm were found for n-heptane using the simple averaging and RMS methods, respectively, while n-decane yielded 23.20 mm for both methods, indicating greater flame stability. The LDA measurements, performed with a commercial DANTEC system, provided three-dimensional velocity profiles at six axial positions. The obtained profiles are coherent with results reported in the literature for the same burner, confirming the validity of the assembled setup. The primary limitation identified is the inability to achieve subzero injection temperatures with the current configuration; a geometric modification of the CRSB would be required to allow cooling of the entire injection system.