the cooling of air with an increase in altitude is called convection.
the cooling of air with an increase in altitude is called convection.
the cooling of air with an increase in altitude is called?
convection
Na
Na
the liner contains the combustion process and introduces the various airflows (intermediate, dilution, and cooling, see "air flow paths" below) into the combustion zone. the liner must be designed and built to withstand extended high temperature cycles. for that reason liners tend to be made from superalloys like hastelloy x. furthermore, even though high performance alloys are used, the liners must be cooled with air flow. some combustors also make use of thermal barrier coatings. however, air cooling is still required. in general, there are two main types of liner cooling; film cooling and transpiration cooling. film cooling works by injecting (by one of several methods) cool air from outside of the liner to just inside of the liner. this creates a thin film of cool air that protects the liner, reducing the temperature at the liner from around 1800 kelvins (k) to around 830 k, for example. the other type of liner cooling, transpiration cooling, is a more modern approach that uses a porous material for the liner. the porous liner allows a small amount of cooling air to pass through it, providing cooling benefits similar to film cooling. the two primary differences are in the resulting temperature profile of the liner and the amount of cooling air required. transpiration cooling results in a much more even temperature profile, as the cooling air is uniformly introduced through pores. film cooling air is generally introduced through slats or louvers, resulting in an uneven profile where it is cooler at the slat and warmer between the slats. more importantly, transpiration cooling uses much less cooling air (on the order of 10% of total airflow, rather than 20-50% for film cooling). using less air for cooling allows more to be used for combustion, which is more and more important for high performance, high thrust engines.
combustor