Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows

Abstract

Reply to "Comment on 'Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows' " [Rev. Sci. Instrum. 74, 3559 (2003)] Rev. Sci. Instrum. 75, 286 (2004); 10.1063/1.1634361Comments on "Fiber optic reflectometer for velocity and fraction ratio measurements in multiphase flows" [Rev.A technique based on the coherent mixing of scattered signal with Fresnel reflection signal from the tip of an optical fiber is used to demonstrate the feasibility of measuring the velocity and fraction ratio of solid particles and gas bubbles or liquid droplets in a liquid or gas flow. If the liquid or gas flow is seeded with small neutrally buoyant particles, the technique is then capable of measuring the velocity as well as the fraction ratio of all three phases of the flow at a given point. The method is briefly described as follows. An optical signal derived from a diode laser driven by a constant current is launched into a single-mode optical fiber and transmitted, through a fiber coupler, to the signal fiber inserted into the test fluid. The diode laser used is a multilongitudinal mode device that has a low coherence length of about 200 m. The coherently mixed signal propagates back to the signal fiber, through the fiber coupler, and detected by a detector. By analyzing the signal, the velocity and fraction ratio of each phase can be obtained. Using water seeded with small solid particles and air bubbles, it is demonstrated that the technique is capable of measuring the velocity in the direction parallel to the fiber. Since the only intrusion to the fluid is the tiny fiber probe ͑a dimension of 125 m in diameter͒, the disturbance to most fluid flows is negligible, therefore, the technique is nearly nonintrusive.

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

“…Generally, the optical probe is considered rather accurate in terms of void fraction. Comparing optical probe results with other measurement techniques (i.e., visual or pressure sensors), the relative differences found in the literature are as follows: between À 0.8% and À 16% (Barrau et al, 1999), À2.2% (Zhang and Zhu, 2013), -3% (Chang et al, 2003), À 11% (Lima Neto et al, 2008), between À6 and À 14% (Kiambi et al, 2003), þ 12% (Simonnet et al, 2007). Barrau et al observed the worst performance with no liquid flow and/or at low gas fractions.…”

“…Moreover, this measurement period is far above the typical values of 1-5 min for similar optical probes (Chang et al, 2003;Chaumat et al, 2005a;Lima Neto et al, 2008;Zhang and Zhu, 2013).…”

“…The rise time errors are primarily affected by the impact angle of the bubbles with the probe tip. The relative difference reported in the literature, compared with other techniques (i.e., image processing) are þ 45% (Cartellier and Barrau, 1998), þ5% (Kiambi et al, 2003), between þ 5 and þ 6% (Chang et al, 2003), between þ10 and þ30% (Chaumat et al, 2005a), þ15% (Simonnet et al, 2007), and þ 29% (Lima Neto et al, 2008), approximately þ9% (Zhang and Zhu, 2013). Bubble diameter.…”

Annular Gap Bubble Column: Experimental Investigation and Computational Fluid Dynamics Modeling

“…• Void fraction: Comparing optical probe results with other measurement techniques (i.e., visual or pressure sensors), it is generally found that the underestimation of the local value and the relative differences is between À0.8% and À16% [33,[36][37][38][39]. It is worth noting that Simonnet et al [34] observed an overestimation of the optical probe value of þ12%.…”

Application of Image Technique and Optical Fiber Sensor for Air-water Mixture Flow

“…신호의 시계열로부터 위상 상 태를 검토하고 지속시간을 바탕으로 공극률 및 크기를 추 정한다 (Chanson, 1997). 전도도식 장치 외에 위상차에 신 호변화를 나타내는 광섬유를 활용한 기법도 연구에 사용 되고 있다 (Chang et al, 2002;Chang et al, 2003). Chang et al (2003) (Ryu et al, 2007 (Chanson, 1997;Jung and Ryu, 2012 …”