Abstract: A method of controlling an economizer is provided. A heating, ventilating, and air conditioning unit is operated in one of a heating mode and a cooling mode to provide conditioned air to a plurality of zones. A first temperature representative of air returned to the unit from the plurality of zones is sensed and a second temperature representative of the outdoor air is sensed. An economizer is modulated to increase the amount of outdoor air entering the unit when the first temperature falls below a cooling setpoint, the second temperature is greater than the first temperature, and the unit is operating in the cooling mode. The economizer is also modulated to increase the amount of outdoor air entering the unit when the first temperature rises above a heating setpoint, the second temperature is lower than the first temperature, and the unit is operating in the heating mode.

Abstract: A method for producing apertures in hot section components of gas turbine engines made from ceramic matrix composites that have at least one oxidizable component. The method involves forming the apertures using a laser beam controlled by parameters that ablate the ceramic matrix composite in the path of the beam, while simultaneously heating the matrix material, SiC or SiN, to a sufficient temperature to oxidize it to form a silica. Sufficient heat is supplied by the beam to melt the silica to cause it to flow. The melted silica is quickly solidified as recast silica along the walls of the newly created aperture before it has an opportunity to flow and form undesirable geometries. The wall of the aperture is formed of recast silica that is a smooth surface and that forms an oxidation barrier to inhibit any further oxidation of the underlying composite as it is exposed to the high temperatures and oxidative, corrosive atmosphere of an operating gas turbine.