Using Burner Exit Temperature
in the Control of a Geared
Turbofan Engine with NPSS
David Shore
Project Summary and Background
• Internal Pratt & Whitney engine simulations use the
Numerical Propulsion System Simulation (NPSS) for
modeling engine performance.
• All models supplied to the customer for engine
performance modeling use NPSS as well.
• Previous customer model was developed for thrust
levels of 23k and 21k lbs of thrust, for max takeoff
(MTO), max continuous (MCT), and max climb (MCL)
power settings.
– Customer model target thrusts for a number of flight regimes in
the flight envelope were either missing updated targets, or not
meeting new requirements.
– New simulation needed to be developed using combustor exit
temperature (CET or T4) as the rating target.
New Customer Requirements
• Additional to the 23k base thrust level and the 21k
derate, an 18.9k derate was also requested.
• New requirements for MTO, MCT, and MCL across all
derates was required. Examples follow:
– 21k MCT = 0.94 * 23k MCT within the takeoff envelope. Outside
the takeoff envelope, 21k MCT = 23k MCT
– 18.9k derate = 0.90 * 21k at all flight regimes and bleed
configurations
– MTO ≥ MCT ≥ MCL
• These examples above are additional requirements to
the agreed upon thrust targets outlined in the technical
requirements document (TRD) agreed upon between the
customer and P&W.
T4 Ratings Table
• Thrust targets were hit by creating a new T4 ratings
table. By running the baseline customer simulation,
saving the thrust and T4 output, and modifying the T4
values, I created a new T4 table that hits the new thrust
targets.
• These requirements had to be met for the following
conditions:
– 23k MTO, MCT, MCL
– 21k MTO, MCT, MCL
– 18.9k MTO, MCT, MCL
• Additional to the thrust levels above, new schedules
need to be developed for a number of different bleed
configurations. Different schedules were created using
the different combinations of ECS, CAI, and WAI bleed
off-take.
T4 Schedules
Modified A/C Flight Envelope
• Schedules needed to be defined throughout the entire
flight envelope and takeoff envelope of the aircraft.
Typically, a “node” was placed at every 2000 feet and
0.05 MN. Ratings file nearly doubled in size (~10k lines
of code)
CSeries Operating Envelopes
40000.00
39,000 ft
35000.00
0.77M
30000.00
Pressure Altitude (ft)
25000.00
20000.00
15000.00
14,500 ft
12,000 ft
10000.00
Take-Off
Envelope
5000.00
0.00
-2,000 ft
-5000.00
0
0.1
0.2
0.3
0.4
0.5
Mach Number
0.6
0.7
0.8
0.9
Contour Plots and Behavior Checks
• Ratings design using T4 results in a typical behavior –
final ratings file exhibited normal behavior
+
=
Contour Plots and Behavior Checks
• Hundreds of contour plots were created to ensure model
was correctly targeting T4, and resulting in the required
thrust levels.
21k to 18.9k Derate Contour Plot
23k to 21k MCT Bleeds OFF Contour Plot