Development and application of a turbulence model for a sootblower jet propagating between recovery boiler superheater platens.
Published: 2005
Language: eng
Number of pages: 189
Description: The flow of a sootblower jet as it exits the nozzle is supersonic and turbulent. Further downstream, as the jet mixes with its surroundings, the velocity decreases while the turbulence level increases. The jet can be described using the averaged Navier-Stokes equations, the perfect gas equation of state, and a turbulence model. Among these equations, it is only the turbulence model that has not reached a mature stage of development. The inability of current turbulence models to account for the turbulent effects of the jet has been the major source of errors in sootblower jet simulations.Understanding the dynamics and characteristics of a sootblower jet as it sweeps through boiler banks and interacts with deposits is an important step in the effort to improve sootblowing strategies. It is difficult and costly to study sootblower jet flow characteristics directly in an operating boiler due to its hostile environment. A much more convenient way to study the jet flow characteristics is through a numerical simulation and laboratory experiments.The second part of this thesis deals with the application of the new model to study the performance of low pressure sootblowing and the jet characteristic as it flows between two platens. The results of the numerical simulations suggest that the jet produced by the low pressure nozzle can exert a comparable amount of force on deposits of various thicknesses and distances from the nozzle exit as the jet produced by the high pressure nozzle.In the first part of this thesis, the governing equations and a literature review, which is aimed at gaining insight from the works of other researchers in an effort to model the turbulence of high-speed jets, are presented. Several challenges associated with modeling the turbulence of a sootblower jet are identified. These challenges together with the Direct Numerical Simulation (DNS) results of Sarkar (1995) and Sinha et al (2003) were used as a guide to develop a new K-epsilon based turbulence model. The model accuracy to predict free, confined, and impinging jets has been demonstrated by its good agreement with experimental measurements.The objective of this research is to develop a numerical model that can satisfactorily describe the fluid mechanics of sootblower jet interaction with tube banks and deposits, especially in the superheater sections of the boiler where massive deposit build-up generally occurs. In conjunction with laboratory experiments, the verified model will be used to study (i) the feasibility of utilizing less valuable low pressure steam for sootblowing and (ii) the characteristics of a sootblower jet propagating between superheater platens.
Notes: Thesis (Ph.D.)--University of Toronto, 2005.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 66-06, Section: B, page: 3278.