Did James Prescott Joule also design this thermodynamic workcycle, separate from George Brayton? I've not found any reference to Joule's involvement besides that from George Brayton. Could someone clarify?
As is usual with technological inventions no one person invents the whole thing. Watt's steam engine was indebted to Newcommen's, and toy steam engines were known in antiquity and described by Heron. The same is true of the constant pressure cycle. Here is from Comparative Study of Open and Closed Heat-Engines by Eames, Evans and Pickering, which includes references to Joule's and Brayton's original works:
"The constant pressure cycle too has a long history. In 1791 John Barber patented the first engine of this type, which incorporated an air compressor, a combustion chamber and an early type of turbine . However, it was James Prescott Joule (1850) that provided the first theoretical description of the constant pressure cycle , more than 20 years before George Brayton invented his improvements . It is interesting to note that both Joule’s and Brayton’s engines were reciprocating piston types and both the original work of Barber and the improvements by Brayton were based on internal combustion engines but that Joule’s own test engine was externally heated.
- Eckardt, D. Gas Turbine Powerhouse; De Gruyter Oldenbourg: Berlin, Germany, 2014.
- Joule, J.P. On Air-Engines; Report of the British Association: Manchester, UK; 19; June; 1851.
- Brayton, G. Improvements in Gas-Engines. U.S. Patent 125166A, 2 April 1871.
On the Air Engine was published in the Philosophical Transactions of the Royal Society of London the next year, 1852, as a joint work with William Thomson, a.k.a Lord Kelvin, just two years after Joule's most famous paper On the Mechanical Equivalent of Heat. Joule did not actually construct the engine and perform experiments on it, but he described it in detail, and gave a mathematical theory of its work developed with Thomson's help. For more on Joule and Thomson's joint work, which clarified the foundations of modern thermodynamics, see James Joule, William Thomson and the Concept of a Perfect Gas by Rowlinson.