INTRODUCTION 



A study conducted at the Naval Civil Engineering Laboratory (NCEL) 

 showed that mixing of two or more fluids in desired proportions is 

 feasible by using proportional fluid amplifiers. The operational 

 principle of such mixing systems is based upon the flow modulating 

 characteristics, an unique feature, of most proportional fluid ampli- 

 fiers. A proposed concept of a fluidic system'^ suitable for mixing 

 two fluids is shown in Figure 1. The system uses two double leg 

 elbow proportional amplifiers, one for each fluid. The fluid ampli- 

 fiers control the flow of two fluids to mix them in the desired 

 ratios. The amplifiers are controlled by the signals tapped off from 

 the venturi orifice on the mixture line. For changing the mixture 

 ratio a variable fluid resistor is provided on the control line of 

 each fluid amplifier. These variable resistors are fluidic passive 

 devices consisting of a resistance path either of a variable length 

 or of a variable cross-section which is varied with a control knob. 



Due to some definite advantages offered by the fluidic components , 

 a research program was initiated to develop a fluidic system for mixing 

 hot and cold water capable of handling 5 gpm of each fluid. During 

 this program it was found necessary to develop a double leg elbow 

 amplifier with a 0-5 gpm output flow range since this component is not 

 available commercially. Following successful development of a suitable 

 amplifier, a mixing system was designed and was tested by mixing water 

 from two sources. The report describes in detail the entire development 

 program of the mixing system. 



DOUBLE LEG ELBOW AMPLIFIER 



Consider the amplifier shown in Figure 2, in which the flow through 



its active leg, in the form of a short radius elbow, is interacted by 



a small flow through its control port. Further, the flow through the 



passive leg of the amplifier combines with that through the active leg 



at its exit and forms a jet which is called the "power jet" in the 



Fluid State terminlogy. The emanating angle of the power jet can be 



changed either by regulating the supply flow or by varying the flow 



through the control port. However, the efflux velocity of the power 



jet can be changed by varying the supply flow only. The proportional 



deflection of the power jet by the control flow can then be utilized in 



dividing the supply flow between the two output ports of the amplifier 



to obtain a proportional action. Development of such an amplifier to 



handle 5 gpm of water is described in the following sections of the 

 report . 



