Gas Dynamics of Flow through Valves P M
- Slides: 15
Gas Dynamics of Flow through Valves P M V Subbarao Professor Mechanical Engineering Department Method to Estimate the Flow Capacity of Valve Passage….
Stream Tube formed by Flow Through Valves Equivalent Converging-Diverging Nozzle Configurations: Mild Separation. Severe Separation
Models for Valve Flow Passage Instantaneous Minimum Area
Instantaneous Governing Equations Non reacting, no body forces, viscous work negligible Conservation of momentum for frictional steady flow: Conservation of energy for ideal steady flow:
Ideal Gas law : Mach number equation :
Nature of Real Flow : Variable Area Ducts
Compressible Real Flow Effect of Mach number is negligible on friction factor….
Friction Factor for Compressible Flow Laminar Flow Turbulent Flows k : Roughness Parameter
Mach Models for Isentropic Valve Flow Passage Minimum Area Effect of Differential Change in Area:
Specific Mass flow Rate through Valve Passage Mass flow rate per unit area of cross section:
Conditions for Choked Flow
Isentropic Compressible Flow Through Inlet Valve Resource : The total pressure in the inlet manifold Cylinder pressure – • The air flow rate is related to the upstream stagnation pressure p 0 and stagnation temperature T 0, Static pressure just down stream of the valve and a reference area AR. • AR is a characteristic of the valve design. When the flow is chocked:
Isentropic Compressible Flow Through Exhaust Valve Resource : The total pressure in the cylinder – Static Pressure in Exhaust manifold • The gas flow rate is related to the cylinder stagnation pressure p 0, cyl and stagnation temperature T 0, cyl , Static pressure just down stream of the valve and a reference area AR. • AR is a characteristic of the valve design. When the flow is chocked:
Early Choking of Valve Passage Extent of Valve Opening
Frictional Compressible Flow Through Inlet Valve • The real gas flow effects are included by means of an experimentally determined discharge coefficient CD. When the flow is chocked: