Abstract: The complicated flow pattern is existent in fixed conical valve. When the high speed jet flowing near the diversion cone injects the sudden enlargement area, the severe vortex and evident negative pressure are generated. To reduce or eliminate the negative pressure area, the admission pipe should be installed. For clarifying the air admission and flow rule beyond air admission, a calculation mathematical model is built, the basic law of negative pressure generation and air admission is obtained; CFD is adopted to certify that the admission pipe is efficient to restrain the negative pressure; under air admission condition, the two-phase flow analysis for fixed conical valve are done, so the discharge coefficient and air injection law are gotten. The conclusion is verified by experiment. The study testified that combining the CFD with theoretical model to solve the air admission and discharge coefficient for fixed conical valve is feasible.

Key words: fixed conical valve, air admission, discharge coefficient, two phase flow