respectively these figures illustrate that there is relatively even flow of material which results in more controlled and even combustion a velocity variance of about u2212 0 2 to about 0 2 across the upper port is desirable in order to create a symmetrical flat flame and prevent excess velocity shear outside the range of 0 5 to 5 and preferably 0 8 to 4 which results in the formation of hot spots inside of the precombustor because of excessive mixing of fuel and oxidant inside the precombustor chamber and a velocity variance of about u2212 0 2 to about 0 2 across the gaseous fuel nozzle is desirable for same reasons as outlined above for the oxidant the data shown in fig6 and fig8 was generated by using a pitot tube and hot wire anemometer in accordance with conventional methods fig9 is a graphical representation of the operation of the device of fig1 that shows the relationship between pressure and flow of air used as an analog fluid in place of oxygen in the oxygen inlet port the data shown in fig9 was generated in the same manner as that of fig5 with the exception that the flow was measured with a commercially available flow meter an oxidant pressure of about 0 to about 225 inches of water column at a flow rate of about 0 to about 40 000 scfh is desirable in order to have a low pressure oxygen supply system e g oxygen supplied from an adsorption based air separation unit without the use of a pressure boosting device e g a fan or a pump which adds capital and operating costs to the air separation unit fig1 is a graphical representation of the operation of the device of fig1 that shows the.