George Brayton Designed the first continuous ignition combustion engine (Brayton’s ready motor) The machine he invented introduced the process of continuous combustion (brayton cycle) which became the basis of for development of gas turbine. His machine made headlines in scientific journals of his time, but was superseded within a few years by Nikolaus Otto’s engine a more efficient and quieter design
Brayton Engine componentA Brayton-type engine consists of three components: A gas compressor A mixing chamber An expander
Brayton Cycle A thermodynamic cycle (also variously called the Joule or complete expansion diesel cycle) consisting of two constant- pressure (isobaric) processes interspersed with two reversible adiabatic (isentropic) processes.
Brayton Cycle Now, the Brayton cycle is used for gas turbines only where both the compression and expansion processes take place in rotating machinery.
Brayton Cycle Components: First, Fresh air is drawn into the compressor in which pressure and temperature are raised The high-pressure air proceeds into the combustion chamber, where the fuel is burned at constant pressure. The resulting high-temperature gases then enter the turbine, where they expand to the atmospheric pressure through a row of nozzle vanes
Brayton cycle components This expansion causes the turbine blade to spin, which then turns a shaft inside a magnetic coil. When the shaft is rotating inside the magnetic coil, electrical current is produced. The exhaust gases leaving the turbine in the open cycle are not re- circulated.
Processes and how they occur Isentropic process - Ambient air is drawn into the compressor, where it is pressurized. Isobaric process - The compressed air then runs through a combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the chamber is open to flow in and out. Isentropic process - The heated, pressurized air then gives up its energy, expanding through a turbine (or series of turbines). Some of the work extracted by the turbine is used to drive the compressor. Isobaric process - Heat rejection (in the atmosphere).
Differences to other cycles The thermal efficiency for a given gas, air, is solely a function of the ratio of compression. This is also the case with the Otto cycle. For the diesel cycle with incomplete expansion, the thermal efficiency is lower. The Brayton cycle, with its high inherent thermal efficiency, requires the maximum volume of gas flow for a given power output.
Differences to other cycles The Otto and diesel cycles require much lower gas flow rates, but have the disadvantage of higher peak pressures and temperatures. These conflicting elements led to many designs, all attempting to achieve practical compromises. With the development of fluid acceleration devices for the compression and expansion of gases, the Brayton cycle found mechanisms which could economically handle the large volumes of working fluid. This is perfected in the gas turbine power plant.
The open gas-turbine cycle can be modelled as a closed cycle by utilizing the air-standard assumptions. Here the compression and expansion process remain the same, but a constant-pressure heat- rejection process to the ambient air replaces the combustion process.