walls monotonically decreasing to zero at the separation bubble 
center. Such a velocity distribution will induce a monotonically 
decreasing centrifugal acceleration on the jet with a maximum 
near the wall. This configuration will force most of the oil 
into the separation bubble. The effluent flows out through 
the two outlets provided on the device. Such a design should 
improve the separating capabilities of the separator markedly. 
An experimental investigation is underway to evaluate this 
concept. 
Another possible improvement in the oil separation capability 
of the device can be accomplished by decreasing the static 
pressure within the separation bubble of the flow. This can 
be achieved by increasing the centrifugal force on the mixture 
jet which in turn can be increased by decreasing the radius 
of the jet center-line. The separation bubble pressure can 
also be decreased by increasing jet efflux momentum. 
An Automated Oil Extraction System 
It was observed during the feasibility tests that the 
rate of oil extraction from the oil collecting chambers of 
the elements affected the quality of oil being extracted appreciably. 
Too high an extraction rate disturbed the oil-water interface 
in the collecting chamber and the oil being extracted contained 
up to 50% water. A low oil extraction rate on the other 
hand reduced the rate of oil captured by the separation bubble 
of the flow. This resulted in more oil in the effluents thereby 
deteriorating the performance of the device. A system to control 
the oil extraction rate is, therefore, required for proper 
functioning of the separator. Such a system can be either a 
proportional or on-off type. Because of the simplicity of their 
design and their lower costs, systems of the on-off type are 
considered for this application. 
One such system, shown in Figure 15, uses the difference 
in electrical conductance of water and that of the oil. Practically 
all oils are electrical insulators. Water (excluding pure water) 
is capable of conducting electricity. The system of Figure 
15 uses this property in sensing the oil-water interface in 
the collecting chamber by providing two electrodes at different 
heights in it. For sensing, the electrodes are connected to 
a 10 volt AC supply through a 1000 ohm resistor. The solenoid 
valve on the outgoing oil line is operated by the output of 
the amplifier which receives its input from a rectified voltage 
signal across the resistor in the sensing circuit. The use 
of AC supply in the sensing circuit minimizes the electrolysis 
in the collecting chamber. When the oil-water interface is 
below the bottom electrode, the resistance in the sensing circuit 
is very high and practically no current flows through it. 
