Turbine#Theory of operation

Under a constant-pressure turbine, also called pulse action turbine or turbine means a turbine in which the working medium has before and after the impeller on the same ( static ) pressure and the same enthalpy. The usable work for the impeller so come exclusively from the conversion of kinetic energy ( dynamic pressure) of the working medium in accordance with Bernoulli's energy equation. An impulse turbine has a response rate of zero. Examples of constant-pressure turbines are the Pelton turbine, Curtis turbine, Lavalturbine and the cross-flow turbine. Constant-pressure turbines are mainly built in chamber construction, since the cross-sectional areas for leakage currents are small compared to the drum construction. The chamber design is also due to the very low axial forces possible (likely to occur increasingly in reaction turbines on ).

The counterpart of the impulse turbine is the reaction turbine, also called a reaction turbine ( response rate> 0). A low pressure turbine ( reaction degree <0) is theoretically possible, but practically not useful and therefore not realized.

Advantage of peer pressure level (among others):

  • Minimum number of stages, lower investment costs ( the impulse turbine can degrade the dual peripheral speed in one step )
  • Seal between the blade and housing is not important ( no pressure difference before and after the blade )
  • Partial action is possible, because the working medium after leaving the vane does not extend (density constant)
  • For the same power output a constant-pressure stage rotates 0.707 times (1 / √ 2) slower than a pressure level with a reaction rate of 0.5, assuming mass flow and turbine diameter are identical.
  • At the same speed, a constant-pressure stage is twice the power as from a pressure stage with a degree of reaction of 0.5, assuming the mass flow and turbine diameter are identical.
  • A turbine with Gleichdruckbeschaufelung thus has the largest Losreißmoment compared to other turbines, and is therefore in the art, in particular interest where at low speeds, high starting torques are required. So peer pressure levels are preferably in air starters for jet engines used.

Disadvantage of constant-pressure level (among others):

  • Constant efficiency, moderate performance (but slightly lower in comparison with constant-pressure turbines)
  • Flow velocity between the rotor blades higher than Überdruckbeschaufelung ⇒ more pressure loss in the blade itself ( gap losses are higher).

Swell

  • Willy JG Brown Ling: aircraft engines, Springer Verlag. Impulse turbine side 578 Online
  • Turbine
38937
de