Hot wire ignition of hydrogen-oxygen mixtures

Experiments were conduted to measure the temperature at which hot wires ignited hydrogen-oxygen mixtures. The wires served both as ignition sources and as resistance temperature sensors. Gas compositions were varied between lean and rich flammability limits (4 %-94 % hydrogen) and initial gas pressures from 100 to 110 kPa. A simple model of hot surface ignition used to correlate results gave reasonable predictions for the variation of ignition temperature with hydrogen concentration. However, the ignition temperature was reduced only by approximately 50 K when the pressure was raised to 1100 kPa. The model predicted a much larger decrease in ignition temperature, Suggesting that the assumption of a single-step chemical reaction made in its formulation was not valid as elevated pressures.