Cyclic variation in combustion in a constant volume combustion chamber.

Abstract

Cycle to cycle variations in combustion and turbulence characteristics in a swirling flow were measured in a cylindrical vessel. The vessel was charged by rapid tangential injection using a shrouded valve for two valve lifts (7 mm and 12 mm). A premixed lean mixture of propane and air ($\phi$ = 0.8) was ignited at quarter radius from the center. Pressure rise as a function of time was measured using a pressure transducer. Mean flow, turbulence intensity and Taylor microscale were estimated by statistical analysis of a single hot wire anemometer signal using ensemble averaging and cyclic analysis. Results obtained indicate that changing the valve lift changes turbulence characteristics at mid-radius. However, turbulence characteristics at quarter radius from center and quarter radius to wall were found to be independent of valve lift. Mean time, standard deviation of mean time delay and Taylor microscale were estimated using combustion pressure traces. Results indicate that the mean time and the standard deviation ignition are weak functions of mean flow and turbulence intensity and strong functions of the Taylor microscale as implied by the Tennekes model. Cyclic variations at ignition were observed to contribute the most to cyclic variations.