Turbines and compressors are vital in fluid mechanics, converting energy between fluids and mechanical systems. From gas turbines in jet engines to hydraulic turbines in dams, these devices play crucial roles in power generation and industrial processes.
Thermodynamics is key to understanding turbine and compressor performance. Efficiency metrics like isentropic efficiency help engineers optimize these machines, balancing power output with energy losses. Design considerations vary based on application, from high-temperature materials in gas turbines to moisture control in steam turbines.
Types and Applications of Turbines and Compressors
Types of turbines and compressors
Top images from around the web for Types of turbines and compressors
Centrifugal Flow Jet Engine Compressor View original
Is this image relevant?
1 of 3
Turbines convert fluid energy into mechanical energy
Gas turbines convert thermal energy from high-temperature, high-pressure gases into mechanical energy used in power generation (power plants), aircraft propulsion (jet engines), and industrial applications (oil and gas)
Steam turbines convert thermal energy from high-pressure steam into mechanical energy used in power generation (coal and nuclear power plants) and industrial processes (chemical manufacturing)
Hydraulic turbines convert kinetic energy from flowing water into mechanical energy used in hydroelectric power generation (dams and run-of-river systems)
Compressors increase the pressure of a fluid by converting mechanical energy into fluid energy
Centrifugal compressors increase fluid pressure by converting kinetic energy into pressure energy used in gas processing (natural gas), refrigeration (air conditioners), and air conditioning systems (buildings)
Axial compressors increase fluid pressure by progressively compressing it along the axis of rotation used in gas turbines (power generation) and jet engines (aircraft propulsion)
Positive displacement compressors increase fluid pressure by reducing its volume in a confined space used in refrigeration (refrigerators), air conditioning (heat pumps), and compressed air systems (pneumatic tools)
Thermodynamics and Performance Characteristics
Thermodynamics of turbines and compressors
Turbines involve an expansion process that converts high-pressure, high-temperature fluid into low-pressure, low-temperature fluid while extracting work
Isentropic expansion process is an ideal process where the entropy remains constant
Actual expansion process involves irreversibilities such as friction and heat transfer resulting in a lower efficiency compared to the isentropic process
Compressors involve a compression process that converts low-pressure, low-temperature fluid into high-pressure, high-temperature fluid while requiring work input
Isentropic compression process is an ideal process where the entropy remains constant
Actual compression process involves irreversibilities such as friction and heat transfer resulting in a higher work input requirement compared to the isentropic process
Performance metrics for turbines and compressors
Power output quantifies the rate of work produced or consumed
Turbines: W˙=m˙(h1−h2), where W˙ is power output, m˙ is mass flow rate, and h1 and h2 are inlet and outlet specific enthalpies
Compressors: W˙=m˙(h2−h1), where W˙ is power input, m˙ is mass flow rate, and h1 and h2 are inlet and outlet specific enthalpies
Isentropic efficiency compares the actual performance to the ideal isentropic process
Turbines: ηt=h1−h2sh1−h2, where h2s is the specific enthalpy at the outlet for an isentropic process
Compressors: ηc=h2−h1h2s−h1, where h2s is the specific enthalpy at the outlet for an isentropic process
Pressure ratio, defined as the ratio of outlet pressure to inlet pressure, affects the power output, efficiency, and size of turbines and compressors
Design Considerations and Operating Principles
Design of gas and steam turbines
Gas turbines operate on the Brayton cycle, which consists of:
Isentropic compression in the compressor
Constant-pressure heat addition in the combustion chamber
Isentropic expansion in the turbine
Constant-pressure heat rejection in the exhaust
Gas turbine components include:
Compressor increases the pressure of the incoming air
Combustion chamber mixes the compressed air with fuel and ignites the mixture
Turbine extracts work from the high-temperature, high-pressure gases
Gas turbine design considerations involve materials selection for high-temperature operation, cooling systems for turbine blades, and emission control technologies (catalytic converters)
Steam turbines operate on the Rankine cycle, which consists of:
Isentropic compression in the pump
Constant-pressure heat addition in the boiler
Isentropic expansion in the turbine
Constant-pressure heat rejection in the condenser
Steam turbine components include:
Boiler generates high-pressure steam by heating water
Turbine extracts work from the high-pressure steam
Condenser condenses the low-pressure steam back into water
Pump increases the pressure of the water and returns it to the boiler
Steam turbine design considerations involve steam quality and moisture separation, blade erosion prevention, and thermal efficiency optimization through regenerative heating (feedwater heaters) and reheating stages (intermediate pressure turbines)