Table 2. Coefficients used in present methodology. The choking of mass flow can be expressed by the famous equation of Dixon"! -* The first controller introduced herein is the closed coupled valve. CCV. It is named so as the valve is installed very close and coupled tc the compressor. According to Gravdahl'*!, close coupled valve is to be understood that the distance between the compressor outlet and the valve is so small that no significant mass storage can take place. The assumption of no mass storage between the compressor and the valve allows for the definition of an equivalent compressor. The closed couplec valve is introduced into the compression system to achieve a pressure drop on the compressor pressure rise. Thus, reduces the characteristic peak and shifts it towers lower flow rates, thus avoiding falling intc surge. Consequently the second state equation of model Eq. 7 can be rewritten as: ot an Table 3. Eckardt rotors geometrical parameter. Table 4. Bayomi rotor geometrical parameter. Fig. 3. Euler’s head and total losses for Eckardt rotor B at different speeds. Fig. 5. Comparison of the experimental choke line and that estimated mathematically for Eckardt rotor O. Fig. 6. Effect of 8 parameter variation on surge line location on performance map of Eckardt rotor B. Fig. 7. Comparison between closed coupled valve and variable speed drive behavior for Eckardt rotor A at 10000 rpm.
