Some Essential Principles for Adjustment of Seal Clearances in Rotary Regenerators

Abstract

In the present study, attention is paid to some indispensable principles for making a useful adjustment of seal clearances in a rotary regenerator, illustrated by means of examples. First, the effect of leakages and their distribution within such a heat exchanger on the efficiency of a steam power plant is presented. In this way it is shown that not only total leakage but also the distribution of the leakages within the rotary regenerator have an important influence on the efficiency. An interesting conclusion appears here—reduction in total leakage may even bring about a drop in power plant efficiency if distribution of leakages changes unfavorably. Second, in order to show in which rotor state seal clearances should be adjusted, appropriate examples of experimental results concerning radial seal clearances in the hot and cold rotor state are compared. Next, on the basis of a leakage network and some experimental data before and after reduction in radial seal clearances, the effect of reduction in seal clearances on the total leakage and its distribution within a rotary regenerator is shown. Thus the value of such a reduction for the efficiency of a steam power plant is evaluated.     

Indirect Estimation of Leakage Distribution in Steam Boiler Rotary Regenerators

Leakages are inherently associated with the heat transfer process in a rotary heat exchanger, owing to clearances brought about by construction difficulties and rotor-housing thermal distortions. The method proposed permits one to evaluate leakage distributions within steam boiler rotary regenerators. In principle, the method is based on a gas flow diagram of the regenerator, where gas streams are arranged into a network in which the corresponding mass flow rates are governed by pressure drops in the seals and matrix rotation. Moreover, energy and mass balances are taken into account where appropriate. On this basis, a nonlinear equation system modeling gas flows within the rotary regenerator is derived. Supplementing this system with data determined experimentally, one obtains a closed form of the gas flow problem, the solution of which gives particular gas mass flow rates within the regenerator and the leakage distribution resulting from it. On the basis of experiments carried out on real devices, the approach presented is exemplified with two particular cases accompanied by evaluation of uncertainties in the final results. A comparison of the results presented with those available by another method concludes the article.