Effect of Back Pressure Chamber Size on Scroll Expander Flow Behavior
Keywords:
Organic Rankine Cycle, Scroll Expander, Back Pressure Chamber,, Flow Dynamics, Pressure DistributionAbstract
This study investigates the influence of back pressure chamber size on the discharge flow dynamics of a scroll expander in an Organic Rankine Cycle system. The objective is to analyze how variations in chamber volume affect pressure characteristics and flow structures at different crank angles. The methodology involves a comparative analysis of three models with increasing chamber sizes: 260 mm, 300 mm, and 340 mm. The results demonstrate that increasing the back pressure chamber size leads to a consistent reduction in average pressure in both the discharge chamber and outlet. For instance, at a 0° crank angle, the average pressure decreases from 126,175 Pa in Model 1 to 95,466 Pa in Model 3. This pressure reduction is most pronounced during the early discharge phase between 0° and 90° crank angles. However, the relationship with flow stability is non-linear. The intermediate chamber size promotes stronger vortex formation due to higher discharge velocities and localized pressure differences, whereas the largest chamber reduces vortex intensity, thereby improving flow stability. The study concludes that back pressure chamber size is a determining factor in scroll discharge dynamics. Larger chamber configurations effectively reduce pressure levels, although intermediate sizes may induce unfavorable flow instabilities. These findings provide important insights for optimizing expansion devices in waste heat recovery applications.
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