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Show INTRODUCTION Powered infrared (PIR) burners consist of a pressurized air supply, an air/fuel mixing chamber, and a porous metallic or ceramic radiant tile. PIR burner is a surface combustor that elevates the temperature of the burner head to a radiant condition. The principle of the infrared burner is as follows [1]: A premixed fuel/air gas mixture enters a highly porous ceramic or metal layer; the mixture is gradually heated inside the layer and combusted, while it is flowing through the layer. The combustion takes place within the layer. The enthalpy of combustion released in the gas phase heats the porous matrix which then emits thermal radiation from the surface to a heat load. PIR burners operate with uniform heat transfer, high efficiency, and low NOx emissions. Applications for PIR burners include boilers, air heaters, process heaters, immersion heaters, and commercial ovens and fryers. One main reason for the present interest in this type of burner is its low NOx emissions. This is attributed to the fact that a large proportion of the heat of combustion is given out as radiation from the burner surface. This results in relatively low gas temperature in the combustion zone compared to that of a conventional free-flame burner. As a consequence, such burners produce less NOx mainly by the so called prompt-NO mechanism [2]. The performance of natural gas-fired heating and cooking equipment is strongly dependent on ambient conditions and natural gas composition. In the United States, ambient temperature, pressure, and relative humidity vary significantly by location and season. Also, natural gas compositions supplied by local gas distribution companies exhibit seasonal and regional variations. This is mainly due to the effort for these gas companies to meet the changing demands from users including industrial, commercial and domestic gas applications. To meet the peak demand in the most economic way, it is a common practice to supplement the existing supply with a readily available gas such as liquefied petroleum gas. In service~ PIR burners have had reliability and performance problems, especially when exposed to various gas compositions, operating altitudes, and other ambient conditions like temperature and humidity. Fuel gases having different heating values or specific gravities invariably have different chemical compositions. These parameters effect the composition of the gaseous emissions from these burners. Burning characteristics of such gases will differ in important respects, one of the most being speed of flame propagation. Generally, the gas company must make sure that the standby fuel will, when mixed with the base natural gas in the maximum proportion to which it is to be utilized, permit the continued satisfactory functioning of appliances. It is the responsibility of the manufacturers to design appliances capable of performing more satisfactorily under reasonably wide variations in gas composition while retaining desirable efficiencies and operation. There have been very limited studies to investigate the effects of gas composition upon the performance of radiant burner. Due to the lack of data and fundamental understanding, the IR burner product development in the industry is empirical in nature, and is conducted with one gas composition. This paper is part of a project that is focused on characterizing the effect of fuel gas composition and ambient conditions such as tempera~ure, (pressur~) altitude, and humidity. on the operation of powered infrared (PIR) burners. In thIS work, a unIque measure~~nt system was developed at CAU's Combustion Laboratory to study the effects of gas compOSItIons upon 2 |