Mixing Element and the Test Results 



The two amplifiers of the system were combined to form one 

 single element for compatness. The elanent in this configuration 

 consists of one amplifier mounted on top of the other. The amplifiers 

 are separated by 1/4-inch thick aluminum plate; the top and bottom 

 cover plates of the mixing element are 3/4- inch thick plexi-glass 

 plates for visualization. The disassembled parts of the element are 

 shown in Figure 34 and the assembled element ready to undergo tests 

 is shown in Figure 35. 



The mixing element was tested on the test setup as shown schematically 

 in Figure 36 and photographically in Figure 37. Mixing tests were 

 conducted under several configurations by running fresh water through 

 each amplifier circuit. Corresponding to a fixed setting of control on 

 one amplifier, the control on the other was varied discretely from 

 zero to the designed value of 0.267 gpm. Since the amplifier operates 

 on a very low output impedance, the flow through the drain side output 

 line of each amplifier was measured using a calibrated bucket and a 

 stop watch. The flow through the mixing side output line of each 

 amplifier was computed by subtracting the flow through the drainside 

 output line from the sum of the supply and the control flows. The 

 reduced data from mxxing tests is shown in Table 9. As can be 

 seen by examining Table 9, the system performed well, i.e., each 

 amplifier operated as predicted. The interaction of the mixing side 

 output flows of the amplifier did not affect the operation of the 

 amplifier. 



DISCUSSION 



It is interesting to note that the system can be automated as 

 shown by the concept of Figure 38. According to this design the 

 control flow to each modulating amplifier is supplied by a controlling 

 amplifier of the proportional type. The supply flow to each controlling 

 amplifier can be varied by a needle valve provided on its line. The 

 control port of each amplifier is connected to the mixing line side 

 output of the moderating amplifier. The change of pressure in the lines 

 OlM and 02M (Figure 38) due to change in mixture demand is communicated 

 to the controlling amplifier which in turn sends a required signal 

 flow into the control port of each modulating amplifier to deliver 

 some definite flow. The controlling amplifier circuitory can be 

 designed such that for no mixture demand the controlling amplifiers 

 do not send any signal to the modulating amplifiers. The valves 

 on the controlling amplifiers can be calibrated such tha t the 

 mixture ratio of the fluids being mixed can be changed simply by 

 varying their settings. Such a system in addition to having 

 fast response is free from hybrid sensors which utilize electrical 

 signals. 



27 



