Abstract
An inherent defect of the operating rotary air preheaters (RAPH) is known as leakage, which seriously hinders the efficient and safe operation of RAPH. It is significant for the estimation of the direct leakage to determine the effects of different structure parameters of sealing sheets and different operation parameters of a RAPH. A direct leakage set-up was built and a three-dimensional numerical model was established to explore the local direct air leaking process of rotary regenerative air preheater and study the effects of geometrical and operational parameters on the leakage. The numerical simulation using the transition k-kl-ω turbulence model was verified by the experimental results. The results show that the local direct air leakage mainly depends on the total pressure difference between the two sides of the seal instead of the one-side pressure. The air leakage can be significantly reduced by narrowing the leakage gap. The increase in the number of sealing sheets can reduce the air leakage own to the increase in the leakage resistance. The increase in the spacing between the adjacent sealing sheets can enlarge the recirculation zone and increase the energy loss of mainstream, greatly reducing the local direct air leakage. Due to the different size recirculation zone formation and streamline curvature induced by sealing sheet, the effect of bending angle on the direct air leakage varies. To obtain lower leakage rate, it is recommended for the rotor of tri-sectional air preheater to pass through flue gas section, secondary-air section, and primary-air section in sequence.
Highlights
The improvement of the energy conversion efficiency in the process of energy consumption is of great significance and has attracted increasing attention in the global energy shortage scenario [1].As an indispensable device in the coal-fired power plant, rotary air preheaters (RAPH) are widely applied to recover the waste heat from flue gas and heat combustion air owing to its compactness and superior performance [2,3]
They assumed that the orifice coefficient and the engineering modifying factor are related to the inlet pressure and sealing gap size, and neglected the effect of the spacing value of adjacent sealing sheets, whereas some other factors, i.e., the bending angle of the sealing sheets and the spacing leakage in an RAPH
They assumed that the orifice coefficient and the engineering modifying factor are related to the inlet pressure and sealing gap size, and neglected the effect of the spacing value of adjacent sealing sheets, whereas some other factors, i.e., the bending angle of the sealing sheets and the spacing the adjacent sheets, could alsothe greatly thewhich directare leakage, which between the between adjacent sealing sheets,sealing could greatly affect directaffect leakage, not reported areprevious not reported in previous studies
Summary
The improvement of the energy conversion efficiency in the process of energy consumption is of great significance and has attracted increasing attention in the global energy shortage scenario [1]. Zhang et al [20] proposed an online application approach to the gap size and estimate the direct leakage of the air preheater. Several studies have considered the effects of different structure of sealing sheets, which are quite important for the estimation and calculation of the direct leakage. Cai et al [13] carried out numerical simulation and experimental research on the direct air an RAPH They assumed that the orifice coefficient and the engineering modifying factor are related to the inlet pressure and sealing gap size, and neglected the effect of the spacing value of adjacent sealing sheets, whereas some other factors, i.e., the bending angle of the sealing sheets and the spacing leakage in an RAPH.
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