The Autoignition of Cyclopentane in an Ignition Quality Tester

Cyclopentane is a flammable hydrocarbon being considered as a working fluid for waste heat recovery applications using Organic Rankine Cycles with direct evaporators. A postulated failure mode consisting of a pinhole leak in a heat exchanger tube raises safety concerns because of autoignition of the working fluid. The ignition delay time of cyclopentane was measured using an Ignition Quality Test device (Advanced Engine Technology Ltd., Ottawa, Ontario, Canada). Hot vitiated air was used to simulate turbine exhaust gas. Experiments were conducted in accordance with ASTM D6890 (with exception to charge pressure and temperature) to determine ignition delay of the fuel at atmospheric pressure for vitiated air (13.3% oxygen). The test matrix encompassed equivalence ratios from 0.5 to 5.0 and chamber temperatures ranging from 673 K to 823 K to establish a set of ignition delay curves. The ignition delay time was observed to decrease with increasing temperature and equivalence ratio. For the cases tested, no ignition was observed at temperatures at or below 723 K or at an equivalence ratio of 0.5.