Euler Turbine Equation P M V Subbarao Professor Mechanical Engineering Department I I T Delhi An Important Engineering Form of Newton's Laws!!!?!?!?!
Simple Turbine : Harvester of Useful Fluid Energy out T
Macro Analysis of A Turbine Fluid in Fluid out
Cartesian View of Momentum Equation This is a vector equation and will have three components in x, y and z Directions. X – component of momentum equation:
X – component of momentum equation: Y – component of momentum equation: Z – component of momentum equation:
Axial Momentum Equations A turbomachine cannot tolerate this force doing any work. The axial force should be completely absorbed by a thrust bearing. Any remaining traces of this force can cause mechanical or aerodynamic damages.
Concurrent Designs for Minimum Axial Thrust
Normal Momentum Equations Resultant radial Force: The radial force component has little do with steady state aerodynamic performance of a turbo-machine. Special Casings are designed to reduce this force. The remaining force is normally absorbed in a journal type bearing.
Pump Impeller and casing
Radial Force on Impeller
Best Efficiency Point (B. E. P Best Efficiency Point (B.E.P.): The point on a pump's performance curve that corresponds to the highest safe efficiency. At this point, the impeller is subjected to minimum radial force promoting a smooth operation with low vibration and noise.
Euler’s Version of Newton’s Second Law In turbo-machines much useful information is obtained by employing Newton’s second law in the form where it applies to the moments of forces. This form is of central importance in the analysis of the energy transfer process in turbo-machines.
Euler’s Statement for Second Law For a system of mass m, the vector sum of the moments of all external forces acting on the system about some arbitrary axis A--A fixed in space is equal to the time rate of change of angular momentum of the system about that axis, i.e.
Euler Theory: Torque exerted by flow on blade row = shaft output torque = Rate of change of Angular momentum of fluid = t Angular momentum is moment of linear momentum of angular velocity, Vq Define, L as Angular momentum :
The Boeing 747 Cruising at an Altitude of 10 km
Turbo-jet Engine
Even for a steady flow through a turbo-machine: Inlet rate of angular momentum : Exit rate of angular momentum at exit: Change in Rate of angular momentum: