What is back pressure turbine?

Question

What is back pressure turbine?

Answer 1

A gas turbine forces compressed air into a combustion can where "atomised" distillate fuel or natural gas is combusted.

Obviously when the fuel is burned it creates HEAT and EXPANSION OF GASES. This increases the pressure in the combustion can and therefore pushes BACK against the compressed air being injected.

This is why turbines are designed such that there is "mechanical advantage" for the gases to be released towards the turbine blades and exhaust. This means that the output path generally is "wider" than the input path. this way gases choose the easiest route to dissipate.

Back pressure is just the force applied to the fuel and air injection system (mostly relevant for the air). If the back pressure exceeds the discharge pressure of the compressor stages then you will have big problems.

The combustion cans have air grooves routed around them to keep temperatures down. Upstream of this there is no protection for heat and the turbine may suffer catastrophic failure.

UPDATE:

My bad, I read the question incorrectly. I thought it was "what is back pressure in a turbine"

Answer 2

A back pressure turbine is the type of turbine used in turbo chargers it utilizes the back pressure from ones engine to created more horse power.

Answer 3

For steam turbines there are three general classifications of steam discharge- back pressure, atmospheric, condensing.

The pack pressure turbine discharges the steam into a pressurized piping system to be used for process heating elsewhere or as the supply to other turbines. For instance a turbine may receive steam at 600 psig and discharge into a 100 psig system.

The atmospheric turbine is obvious. Here the usually short discharge piping is used just to get the steam out of the building or to direct it away safely.

The discharge of a condensing turbine connects to a surface condenser to extend the range of pressure drop through the turbine to extract more power. The discharge pressure is actuallly a vacuum.