FLAMELESS COMBUSTION ELLIS. 643 



the surface, and no heat is developed in any other part of the ap- 

 paratus. While the front of the diaphragm is intensely hot, the back 

 of the apparatus is so cold that one can laj' the hand on it. The 

 combustion of the gas, although confined within narrow limits, is 

 perfect ; for, when once the relative proportions of gas and air have 

 been properly adjusted, no trace of unburnt gas escapes from the 

 surface. Moreover, the temperature at the surface of the diaphragm 

 can be instantly varied at will by altering the rate of feeding of the 

 gaseous mixture; there is no lag in the temperature response — a cir- 

 cumstance of great importance in operations where a fine regulation 

 of heat is required. The temperature of a diaphragm working on 

 a mixture of coal-gas and air, at a given rate of feeding, depends 

 on whether or not the intense radiation from its surface is impeded ; 

 with a freely radiating surface, the temperature of a properly made 

 diaphragm may be maintained at any point up to about 850° C. (say 

 1,550° F.), according to the rate of supply of combustible mixture. 

 A curious feature of the diaphragm is the freedom from back-firing 

 at this or lower temperature. Even when an explosive gaseous mix- 

 ture is passed through the porous wall at a velocity very much smaller 

 than the normal speed of back-firing of the mixture, no explosion 

 backward will occur. Such a plain diaphragm may be placed at any 

 desired angle between the horizontal and vertical planes. 



The diaphragm method is applicable to a variety of combustible 

 gases. Coal or coke oven gas (either imdiluted, or mixed with water 

 gas), natural gas, gasolene-air gas, carburetted water gas, are all 

 well suited in cases where unimpeded radiation is required. I have 

 recently found compressed liquefied gas (Blau gas) to give satisfac- 

 tory results. Also, Prof. Bone has constructed and successfully 

 operated plane diaphragms of all sizes up to 4 square feet in area, 

 and is able to vouch from experience that their durability and radi- 

 ant power are unimpaired, even after long-continued use. 



INCANDESCENCE NOT DEPENDENT ON EXTERNAL ATMOSPHERE. 



A further important point with regard to diaphragm-heating is, 

 that the incandescence of the surface in no way depends upon the 

 external atmosphere. When once the diaphragm has become incan- 

 descent, and the proportions of air and gas supplied in the mixing- 

 chamber at the back have been properly adjusted, the surface will 

 maintain its incandescence unimpaired even in an atmosphere of 

 carbon dioxide, nitrogen, or steam. 



APPLICATIONS OF DIAPHRAGM-HEATING. 



I need hardly point out the many obvious purposes to which " dia- 

 phragm-heating " may be applied. Broiling, roasting, toasting, are 

 at once suggested; others will doubtless occur to you — such efficient 



