MFCU
Mass flow control unit (MFCU) consists of a plug whose shape is contoured having a radius of curvature of 288mm.
The movement of the plug is axial and is controlled through a drive motor. The plug is driven by a geared DC motor and the plug position is obtained using incremental optical encoder mounted on the motor shaft rear extension.
The encoder provides 500 pulses per rotation. An interface unit has to be built to provide an integrated pulse counting (BCD) with LCD/7-segment LED display and buffered TTL equivalent data (20 bit) to the associated data acquisition system for position of the plug. The total traverse length of the MFCU is 73mm which corresponds to 5000 counts in controller.
At different axial locations, different throat areas are formed between the plug and the insert ring. This is the area that controls the mass flow through the intake model, for a given upstream condition. The flow through (throat) area varies from a maximum to a minimum value (non-zero) at the two extreme traverse limits.
The interface unit provides for local mode controls for forward/reverse drive of the plug and for resetting the counters to zero and the display, at plug fully open end. The unit also will be used to provides these operations from the PC (NAL scope).