The process of pulse combustion begins as gas and air are introduced into the sealed combustion chamber with the spark plug igniter. Spark from the plug ignites the gas-air mixture, which in turn causes a positive pressure buildup that closes the gas and air inlets. This pressure relieves itself by forcing the products of combustion out of the combustion chamber through the tailpipe into the heat-exchanger exhaust decoupler and into the heat-exchanger coil. As the combustion chamber empties, its pressure becomes negative, drawing in air and gas for ignition of the next pulse. At the same instant, part of the pressure pulse is reflected back from the tailpipe at the top of the combustion chamber. The flame remnants of the previous pulse of combustion ignite the new gas-air mixture in the chamber, continuing the cycle.
Once combustion is started, it feeds on itself, allowing the purge blower and spark igniter to be turned off. Each pulse of gas-air mixture is ignited at the rate of 60 to 70 times per second, producing 1/4 to 1/2 Btu per pulse of combustion. Almost complete combustion occurs with each pulse. The force of these series of ignitions creates great turbulence, which forces the products of combustion through the entire heatexchanger assembly, resulting in maximum heat transfer (see Fig. 2-18).
Start-up procedures for the GSR-14Q series of Lennox Pulse furnaces, as well as maintenance and repair parts, are shown in Fig. 2-19.