TFE731-5 Combustor Rig Testing

TPE731-5 combustor rig testing was completed to determine the effect of the biofuel blend on combustion system performance. A full scale TFE731-5 combustor rig was installed in the combustion test facility (Figure 3-8) in Phoenix, Arizona, and tests completed from April 20^th to April 30^th, 2009.

The biofuel was supplied from 55-gallon drums, while the JP-8 was provided from the standard laboratory fuel supply. The measured lower heating value (LHV), specific gravity, and aromatic content of the biofuel blend were 43.7 MJ/kg (18808 btu/lb), 0.781, and 7.5 vol.% respectively, while the baseline JP-8 values were 43.2 MJ/kg (18612 btu/lb), 0.792, and 14.1 vol.% respectively.

Performance tests were completed over a range of operating conditions from idle to take-off thrust conditions. Lower power settings are run at actual engine conditions, while the higher power settings are run at scaled conditions. Fuel flows were adjusted to provide a constant heat input (MJ/hr) to the combustor, to account for the varying fuel LHV. There was no significant fuel effect on combustor performance including pattern factor and radial profile, which are a measure of the temperature distribution at the turbine stator inlet plane.

Figure 3-8. TFE731-5 Combustor Rig Installed in C-100 Test Cell

Gaseous and smoke emissions were measured during combustor performance testing using a water cooled sampling rake and a mobile emissions truck. Combustor NOx, CO, UHC, and smoke emissions were measured over a range of conditions including ground idle (7% thrust), take-off (100% thrust), approach (30% thrust), and cruise (75% thrust) conditions. The data reported were averages of the samples taken during a 360^◦ scan of the combustor exhaust (turbine inlet plane). Test results with the biofuel blend are presented as percent change from the emissions with the baseline fuel.

A summary of the rig emission results is shown in Figure 3-9 at each load condition.

-100 -80 -60 -40 -20 0 20

Idle Approach Cruise T/O

Test Condition

%Difference Relative to JP-8

NOx CO UHC Smoke

Figure 3-9. TFE731-5 Rig Gaseous and Smoke Emissions

Inlet

Instrumentation Rake

Exhaust

The NOx, CO, and UHC emissions were very comparable at all conditions for the biofuel blend and the baseline fuel. The CO and UHC emissions were significant only at the idle condition, where there was a small (approximately 2%) reduction due to the lighter more volatile biofuel. There was no significant difference in combustion efficiency at any power condition. There was a 3.5% increase in NOx emissions at the cruise condition, but no significant difference at the other load conditions. Smoke emissions were reduced 25% to 50% at the higher power conditions, due to the lower aromatic content of the biofuel. Smoke emissions at low power conditions were very low, at the instrument detection limit, and not accurate. Test results showed no adverse effect of the biofuel blend on engine gaseous emissions, with a significant reduction in high power smoke emissions, which could improve local air quality near the airport.

Lean blowout tests were run at simulated engine idle conditions ranging from sea level static cold day to 27,500 feet altitude, Mach 0.7. After stabilizing at each condition, the fuel flow rate was slowly decreased while holding combustor inlet conditions constant and continuously recording data. Blowout was detected when the measured combustor exit temperatures suddenly dropped.

Blowout test results were correlated against a corrected reference velocity (corrected airflow). Test results (Figure 3-10) showed no significant difference in lean blowout fuel-air ratios due to fuel type over the range of test conditions, and no loss in blowout margin (difference between minimum fuel schedule and lean blowout line).

Historical LBO Line JP-8

Biojet

Decel Schedule

Fuel/Air Ratio

Corrected Reference Velocity, fps

Historical LBO Line JP-8

Biojet

Decel Schedule

Historical LBO Line JP-8

Biojet

Decel Schedule

Fuel/Air Ratio

Corrected Reference Velocity, fps

Figure 3-10. TFE731-5 Rig Lean Blowout Results

Lean blowout characteristics with both the baseline and biofuel blend were consistent with expectations based on previous Honeywell rig and engine testing.

Lean ignition tests were run at simulated engine ground start and altitude relight conditions. Altitude relights were run at 15,000 and 30,000 feet windmill conditions with varying ambient temperature and aircraft Mach number (0.27 to 0.6). After stabilizing at each condition, an ignition attempt was performed at varying fuel flows until the minimum fuel flow for acceptable ignition delay is found. Ignition delay is the time from when the fuel is introduced and the igniter switched on until ignition was detected by a

rise in combustor exit temperature. The lean ignition fuel-air ratio is reported as a function of corrected reference velocity (corrected airflow). Test results (Figure 3-11) showed no significant difference in lean ignition fuel-air rations due to fuel type over the range of test conditions.

00

Historical SL Lean Ignition Line

00

Historical SL Lean Ignition Line

Figure 3-11. TFE731-5 Rig Lean Ignition Results

There was also no loss of margin between the start fuel schedule and the lean ignition line. Ignition characteristics with the baseline and biofuel blend were consistent with expectations based on previous Honeywell rig and engine testing.

0

Figure 3-12. TFE731-5 Rig Lean Ignition Results for Cold Fuel

Several altitude relight conditions were repeated with cold fuel, simulating a relight after the engine was shutdown for an extended period of time. Test results (Figure 3-12) showed an increase in lean ignition fuel-air ratio with cold fuel compared to ambient fuel as expected, due to the effect of the cold fuel temperatures on atomization.

The ignition characteristics with the biofuel were as good as or better than the baseline

fuel, as the relevant fuel properties (flash point, distillation, and viscosity) were similar.

Note that the scales are different in Figure 3-11 and Figure 3-12.