By the first
rule this tube must be in length equal to four and a half times its
diameter, or 5-5/8 inches. It would appear that the mixing-tube, having
100 times the area of the gas jet, is out of all proportion to the size
necessary for obtaining a mixture of one of gas to nine or ten of air;
but it must be remembered that the gas is supplied under pressure. It is
therefore evident that no mere calculation of areas can be taken,
into account, unless the difference in pressure of the supply is also
considered. A complete reversal of this law is shown in that ruling the
construction of blowpipes, which I have already given in a previous
paper on 'The Use and Construction of the Blowpipe.' In these the air
supply, being under a heavier pressure, is much smaller in area than
the gas inlet; and, to obtain maximum power, the air-jet requires to be
enlarged in proportion to the gas pressure.
"Given a certain area of tube delivering a combustible mixture, the
outlet for this mixture must be neither more nor less than the size of
the tube.
Pages:
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142