Velocity diagram impulse turbine stage z represents the blade speed , Vr represents the relative velocity, Vwa & Vwb- represents the tangential component of the absolute steam in and steam out velocities The power developed per stage = Tangential force on blade x blade speed. Power /stage= (Vw a - Vwb).z/1000 kW per kg/s of steam Reaction Blading The reaction blading principle depends on the blade diverting the steam flow and gaining kinetic energy by the reaction. The Catherine wheel (firework) is an example of this principle. For this turbine principle the steam pressure drop is divide between the fixed and moving blades.

Velocity diagram reaction turbine stage z represents the blade speed , Vr represents the relative velocity, Vwa & Vwb- represents the tangential component of the absolute steam in and steam out velocities The power developed per stage = Tangential force on blade x blade speed. Power /stage= (Vw a - Vwb).z/1000 kW per kg/s of steam The blade speed z is limited by the mechanical design and material constraints of the blades. Rankine Cycle The Rankine cycle is a steam cycle for a steam plant operating under the best theoretical conditions for most efficient operation. This is an ideal imaginary cycle against which all other real steam working cycles can be compared. The theoretic cycle can be considered with reference to the figure below. There will no losses of energy by radiation, leakage of steam, or frictional losses in the mechanical components. The condenser cooling will condense the steam to water with only sensible heat (saturated water). The feed pump will add no energy to the water. The

chimney gases would be at the same pressure as the atmosphere. Within the turbine the work done would be equal to the energy entering the turbine as steam (h1) minus the energy leaving the turbine as steam after perfect expansion (h2) this being isentropic (reversible adiabatic) i.e. (h1- h2). The energy supplied by the steam by heat transfer from the combustion and flue gases in the furnace to the water and steam in the boiler will be the difference in the enthalpy of the steam leaving the boiler and the water entering the boiler = (h1 - h3). Basic Rankine Cycle The various energy streams flowing in a simple steam turbine system are as indicated in the diagram below. It is clear that the working fluid is in a closed circuit apart from the free surface of the hot well. Every time the working fluid flows at a uniform rate around the circuit it experiences a series of processes making up a thermodynamic cycle. The complete plant is enclosed in an outer boundary and the working fluid crosses inner boundaries (control surfaces). The inner boundaries defines a flow process.

The various identifiers represent the various energy flows per unit mass flowing along the steady-flow streams and crossing the boundaries. This allows energy equations to be developed for the individual units and the whole plant. When the turbine system is operating under steady state conditions the law of conservation of energy dictates that the energy per unit mass of working agent ** entering any system boundary must be equal to the rate of energy leaving the system boundary. **It is acceptable to consider rates per unit mass or unit time whichever is most convenient Steady Flow Energy Equations Boiler The energy streams entering and leaving the boiler unit are as follows: F + A + hd = h1 + G + hlb hence F + A = G + h1 - hd + hlb Turbine

The energy streams entering and leaving the turbine are as follows: h1 = T + h2 + hlt hence 0 = T - h1 + h2 + hlt Condenser Unit The energy streams entering and leaving the condenser unit are as follows: Wi + h2 = Wo + hw + hlc hence W i = W o + h w - h 2 + hlc

Feed Water System The energy streams entering and leaving the Feed Water System are as follows: hw + de + df= hd + hlf hence de + df = - hw + hd + hl The four equations on the right can be arranged to give the energy equation for the whole turbine system enclosed by the outer boundary. That is the energy of the fuel (F) per unit mass of the working agent (water) is equal to the sum of - the mechanical energy available from the turbine less that used to drive the pumps (T - (de+ df) - the energy leaving the exhaust [G - A] using the air temperature as the datum. - the energy gained by the water circulating through the condenser [Wo - Wi] - the energy gained by the atmosphere surrounding the plant Σ hl