Experimental Investigation of Two-Phase Flow Instabilities in Low-Mass-Flux Water Wall Tubes of Supercritical Circular Fluidized Bed Boilers

Abstract

For the purpose of disclosing the hydrodynamic flow characteristics, under the low mass velocity conditions of the 600-MW supercritical circular fluidized beds boilers, experimental studies on instability of two-phase flow in parallel vertical internally ribbed tubes were conducted. Two kinds of oscillations, pressure-drop oscillation and density-wave oscillation, have been observed. In the range of test parameters the effects of pressure, mass flux, inlet subcooling, compressible volume, exit throttle, and asymmetric heat flux to the two-phase instability were explored and analyzed. Indications from experiment data are: To increase system pressure, mass flux and inlet subcooling will intensify the stability of water wall tubes. To increase exit throttle will intensify the instability of water wall tubes. The bounding pressure and bounding mass flux of density-wave oscillations and the bounding pressure of pressure-drop oscillation have been obtained. Based on the results of testing and using a homogeneous model, the threshold relational expressions of instability were obtained. The results may be used for the design and safe operation of parallel vertical rifled water wall tubes of supercritical circular fluidized beds boilers.

Acknowledgments

This work was supported by the National Natural Science Foundation of China, number 10975111.

Fan Huang is an M.S. student at the State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, China, under the supervision of Prof. Luo. He received his B.S. in storage and transportation of oil and gas from the Petroleum Engineering School, Xi’an Petroleum University, China. He is currently working on fluidity and heat transfer of gas–liquid two-phase flow.

Yushan Luo is a professor of thermal sciences at the State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, China. Her research interests include heat transfer and testing of multiphase flow. She obtained three national prizes and 14 ministerial prizes, such as the National Prize of Natural Science and Technology Progress, 1996, and Ministerial Prize by State Educational Commission, 1992. Professor Luo has co-authored more than 100 papers in archival journals and conference proceedings.

Haijun Wang is an associate professor at Xi’an Jiaotong University, Xi’an, China. He received his Ph.D. in thermal engineering from Xi’an Jiaotong University in 2001. He obtained his bachelor's degree in power engineering in 1994 from the Nanjing University of Science and Technology, China. His research interests include gas–liquid two-phase flow and heat transfer, steam boilers and heat exchangers, energy-saving technology, air cooling system in power plant. He has co-authored more than 40 papers in archival journals and conference proceedings. He has gained one ministerial prize by Chinese nuclear industry general corporation.

Tingkuan Chen is a professor at the State Key Laboratory of Multiphase Flow in Power Engineering. He earned his B.S. degree in power engineering in Shanghai Jiaotong University in 1956 and M.S. degree in power engineering in Xi’an Jiaotong University in 1960. He was honored as a National Specialist with Outstanding Contribution by the state ministry of personnel affairs of China in 1988, a National Specialist with Outstanding Contribution in High Grade Education by the state council of China in 1991, a Distinguished Talent in Science and Technology by Shaanxi province in 1992, and an Outstanding Professor by Shaanxi province Government in 1993. He also received a first class prize of the National Guang-Hua Award in Science and Technology in 1994. He obtained 3 national prizes and 14 ministerial prizes. He has published 12 books and more than 300 papers.

Yangyang Wu is an M.S. student at the Key Laboratory of Photoelectricity Gas and Oil Logging and Detecting Ministry of Education, School of Electronic Engineering, Xi’an Petroleum University. She obtained her B.S. in communication engineering from the School of Electronic Engineering, Xi’an Petroleum University, China. She is currently working on testing of real-time signal and data processing.