Turbine (mechanical)
A turbine is a rotary mechanical device that extracts energy from a flowing fluid (gas, steam, water, or wind) and converts it into rotational mechanical work through the dynamic action of the fluid on bladed rotor stages. Unlike reciprocating engines, turbines produce continuous rotary output with high power-to-weight ratios and are the dominant prime movers in power generation, aircraft propulsion, and large-scale industrial drives. The energy extraction follows the principles of fluid dynamics, thermodynamics, and blade aerodynamics.
Key Formula
P = m_dot * (U1*Vw1 - U2*Vw2) [Euler's turbine equation]
LaTeX: P = \dot{m} \cdot (U_1 V_{w1} - U_2 V_{w2})
| Symbol | Meaning | Unit |
|---|---|---|
| P | Power output of turbine stage | W |
| \dot{m} | Mass flow rate of working fluid | kg/s |
| U_1 | Blade speed at rotor inlet | m/s |
| U_2 | Blade speed at rotor outlet | m/s |
| V_{w1} | Whirl component of absolute velocity at inlet | m/s |
| V_{w2} | Whirl component of absolute velocity at outlet | m/s |
Worked Example
Problem
In a steam turbine stage, the mass flow rate is 10 kg/s. The blade speed U = 200 m/s (uniform at inlet and outlet). The whirl velocity at inlet Vw1 = 350 m/s and at outlet Vw2 = 50 m/s. Calculate the power output of the stage.
Solution
Step 1: Apply Euler's turbine equation. P = ṁ × (U1 × Vw1 − U2 × Vw2) Step 2: Since blade speed is uniform (U1 = U2 = U = 200 m/s): P = ṁ × U × (Vw1 − Vw2) P = 10 × 200 × (350 − 50) P = 10 × 200 × 300 P = 600,000 W
Answer
Power output = 600 kW
Comparison of Major Turbine Types and Their Operating Parameters
| Turbine Type | Working Fluid | Efficiency (%) | Power Range | Primary Application |
|---|---|---|---|---|
| Steam Turbine (impulse) | Steam | 85–90 | kW to GW | Thermal power plants, ships |
| Gas Turbine (Brayton cycle) | Hot combustion gas | 35–45 (simple), 55–60 (combined) | MW to GW | Jet engines, power generation |
| Hydraulic (Pelton) Turbine | High-head water | 85–92 | kW to 750 MW | Hydroelectric (high head) |
| Hydraulic (Francis) Turbine | Medium-head water | 90–95 | kW to 1 GW | Hydroelectric (medium head) |
| Wind Turbine | Wind (air) | 35–45 (Betz limit ≈59%) | kW to 15 MW | Renewable energy generation |
| Axial Flow Gas Turbine | Hot gas | 88–92 (stage) | MW to GW | Aircraft jet propulsion |
Interactive Tools
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Related Terms
Flywheel
A flywheel is a rotating mechanical device that stores rotational kinetic energy by virtue of its high moment of inertia, acting as an energy reservoir that resists changes in rotational speed. It smooths out fluctuations in power delivery from reciprocating engines (such as internal combustion engines) by absorbing energy during power strokes and releasing it during non-power strokes. Flywheels are used in punch presses, steam engines, automotive engines, and modern grid-scale energy storage systems.
Piston
A piston is a cylindrical mechanical component that reciprocates within a cylinder to transfer force from an expanding gas or fluid to a crankshaft (in engines) or to compress/displace a fluid (in pumps and compressors). The piston forms a movable seal with the cylinder walls through piston rings, enabling controlled pressure differentials. Pistons are the heart of internal combustion engines, steam engines, hydraulic actuators, and pneumatic cylinders.
Thermal Stress
Thermal stress is the internal stress developed in a material when its thermal expansion or contraction is restrained by external constraints or non-uniform temperature distribution. It arises because materials naturally expand when heated and contract when cooled, and any restriction to this dimensional change generates internal forces. Thermal stresses are critical in the design of pipelines, bridges, engine components, and structural elements exposed to temperature fluctuations.
From Latin "turbo" (spinning top, whirlwind), derived from "turbare" (to disturb, to spin). The word was first applied to rotating flow machines by French engineer Claude Burdin in 1822, who coined "turbine" in his work on water wheels submitted to the French Academy of Sciences, inspiring his student Benoit Fourneyron to build the first practical water turbine in 1827.