Aircraft Propulsion, 2nd Edition

12.12 Thrust Chamber Cooling

In this section, we examine the cooling requirements and challenges in liquid and solid propellant rocket thrust chambers.

12.12.1 Liquid Propellant Thrust Chambers

Liquid propellant rockets usually operate for extended periods, that is, typically for several minutes, and thus expose the combustion chamber walls to intense heating. The combustion products reach (near stoichiometric level) temperatures of ∼3000–4700 K depending on the propellant combination (Table 12.1). All modes of heat transfer, that is, convection, conduction, and radiation exist in a rocket combustor and contribute to the combustor wall heating. The products of combustion then expand in a convergent–divergent nozzle to produce thrust. Although expansion of the combustion gases in the nozzle convert their thermal energy into kinetic energy, extended sections of the nozzle downstream of the throat are still exposed to excessive gas temperatures and thus need to be cooled. Fortunately, the liquid propellant onboard offers a cooling capacity that is tapped for the so-called regenerative cooling purposes of the thrust chamber walls. The cooling capacity is due to the phase change, that is, from liquid to vapor, known as latent heat of vaporization. Figure 12.31 shows a definition sketch of the regenerative cooling scheme in a liquid propellant rocket. Note that we switched the chamber designation of temperature, pressure, and so on from using the subscript “c” (for chamber) to “g” ...