turbine - combustion

an effective combustion chamber must provide

• Means for mixing fuel and air for efficient combustion

• Burn the mixture efficiently

• Provide sufficient cooling to a temperature tolerable by turbine blades under all operating conditions

• Distribute hot gasses evenly to the turbine section

components of combustion chamber

• casing

• perforated inner liner

• fuel drain system

• fuel nozzle fuel injection system

• igniter plugs for ignition

combustion chamber converts ____ energy into ___ energy

potential, kinetic

casing

• delivers high pressure to inner liner

• provides cooling

perforated inner liner

fuel/air mixture burns here

contains holes for air to enter for combustion and cooling

fuel drain system

drain fuel out after engine shutdown

prevents tailpipe fires and hot starts during next engine start

fuel nozzle fuel injection system

inject atomized fuel into the inner liner for combustion

igniter plugs

provide initial ignition 

airflow patters

primary air (combustion air)

secondary air (cooling air)

primary air

directed into front of inner liner to mix with fuel for combustion

secondary air

passes thru outer casing via holes in the liner to prevent combustion gasses from contacting the inside wall of the inner liner

cooling air

causes of flameout

• High or slow airflow rates

• Turbulent weather

• High altitude

• Slow acceleration

• High speed manoeuvers

types of flameout

lean die-out

rich blowout

lean die-out

occurs at high altitude, low engine speeds or low fuel pressure

produces weak flame that can extinguish with normal airflow

rich blowout

caused by rapid acceleration with overly rich mixture and insufficient airflow or low fuel temperature

types of combustion chambers

• Single-can burner

• Multiple-can

• Annual combustor

  • Straight flow

  • Reverse flow

• Can-annular combustor

single-can burner

single fuel injection annular-type 

multiple can burner

consists of series of individual combustor cans that function as one unit (8-10 cans)

cans are interconnected with flame propagation tubes to provide a path to spread combustion

annular combustor

consists of 360 degrees single circular combustor with a basket

straight flow or reverse flow

annular combustor - straight flow

air enters front (fuel nozzle area) and discharged at rear

annular combustor - reverse flow

airflow reverse direction 180 degrees twice

used on helicopters and turboprop

can-annular combustor

combination of multiple-can and annular

individual units are arranged radially

cans are connected via interconnect tubes (flame propagation tubes) that move combustion to all cans

precombustor chamber

Portion of primary air enters precombustion chamber > air is mixed with fuel and ignited > gas enters main chamber and joins primary air and a 2nd fuel nozzle

machined ring annular liner

constructed by welding rings of heavy gauge metal together

twin annular premixing swirler combustor nozzle

Improves fuel efficiency and reduce nitrogen dioxide and nitric oxide emissions

consists of 2 independentally controlled, swirl stabilized annular flames for low and high power operation

inspection

boroscope

hot section inspection

emissions

engine emissions must follow strict guidelines iaw Environmental Protection Agency

Includes smoke (carbon particles), unburned hydrocarbons in fuel (HC), carbon monoxide (CO), nitrogen oxides (NOx)