The amplifier consists of three major components: top and 

 bottom cover plates, and the middle plate, called the amplifier's 

 elements, with the flow passages machined in it. The middle plate is 

 made of aluminum and the flow passages in it were machined by milling 

 process. The top cover plate is made of transparent plexi-glass sheet 

 to facilitate flow visualization during tests, whereas, the bottom 

 cover plate is a 1/4-inch thick aluminum sheet. Before assembling 

 the amplifier, the two surfaces of its element were coated with a 

 thin layer of silicon grease to ensure a leak proof assembly. 

 The assembled amplifier, with the pipe fittings for connecting hoses 

 ready for testing is shown in Figure 27. 



Tests and Performance Characteristics 



Testing of the amplifier was necessary to determine its performance. 

 The tests were conducted using the test setup shown in Figure 6. 

 A photograph of the setup showing the amplifier undergaing tests is 

 shown in Figure 28. For a combination of active and passive leg 

 flows, the control flow was varied stepwise from zero to some optimum 

 value and back to zero. Since the amplifier is a low impedance 

 device, the flow through its output ports can not be measured by high 

 impedance devices such as rotamaters and orifices. Thus, the flow 

 through the output ports was measured with a calibrated bucket and a 

 stop watch. It is worfti mentioning here that for the proper operation 

 of the amplifier, the vent on the left of its power jet was connected 

 to the output Ot whereas the one on its right side was connected to the 

 output 0^ . This arrangement prevented occurrence of low pressure 

 regions inside the amplifier caused by the power jet deflection. 



After a series of tests, the operating parameters for the optimum 

 performance of the amplifier were determined and are listed in Table 8. 

 It can be seen from the test data that the active and passive leg 

 flows at the optimum operating point are 2.30 and 3,55 gpm respectively. 

 Correspondingly the flow through the output ports varies from 5.85 

 to zero gpm in the port Od and from zero to 6.10 gpm in the port 

 when the control flow is changed from zero to 0.267 gpm. Photographs 

 of the flow patterns in the amplifier were taken; two of these taken 

 at zero and 0.267 gpm control flow respectively are shown in Figure 29 

 and 30. It is evident from the records that the flow patterns consisted 

 of a strong vortex on the left side of the power jet. Because of 

 turbulent nature of the flow through the amplifier about three percent 

 flow f luctuatior /Qo - Qq . \was observed. The output flow verses 



" mean 



control flow characteristics for the amplifier were plotted from the test 

 data and are shown in Figure 31. The flow characteristics are linear 

 over about 80 percent of the operating control flow range. It should be 



23 



