Abstract
This project presents a large matrix of burner temperature (T4) targets across the
entire operating envelope of a Pratt and Whitney customer’s aircraft for use in thrust
output control. The design of this matrix is geared around hitting a number of thrust
requirements agreed upon with the customer for maximum takeoff, cruise, and continuous power requirements. Additionally, the ratings will be defined for 23k, 21k, and
18.9k pounds of thrust, and for a number of different customer bleed off take combinations. The ratings will be created using the Numerical Propulsion System Simulation
(NPSS), which utilizes turbomachinery theory to determine various engine parameters
based on a specific set of inputs. The entire work through of the rating creation process
will be shown and will result in a final set of ratings that will meet customer demands.
These final ratings will be the input for a customer simulation to be used in the aircraft
design process.
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Table of Contents
Abstract
ii
List of Tables
iv
List of Figures
v
Nomenclature
vi
1. Introduction
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1.1
Geared Turbofan Basics
1.2
Numerical Propulsion System Simulation
2. Methodology
xx
3. Results and Discussion
xx
4. Conclusions
xx
5. References
xx
6. Appendices
xx
2
LIST OF TABLES
3
LIST OF FIGURES
Figure 1 - Two-Spool Turbofan Cross Section with Station Designations
4
LIST OF SYMBOLS
BPR = fan bypass ratio
ISA = International Standard Atmosphere
LHV = Lower Heating Value of fuel (BTU/lb)
MN = Mach number
N1 = Low rotor speed (RPM)
N1F = Fan speed (RPM)
N2 = High rotor speed (RPM)
P0, Pamb = Outside free-stream air temperature (psia)
P2 = Pressure at the face of the fan, core stream (psia)
P12 = Pressure at the face of the fan, fan stream (psia)
P2.5 = Pressure in between the LPC and HPC (psia)
P3 = Pressure at the exit of the HPC (psia)
P4 = Pressure at the exit of the burner (psia)
P4.5 = Pressure in between the HPT and LPT (psia)
P4.9 = Pressure at exit of the LPT (psia)
T0, Tamb = Outside free-stream air temperature (°F)
T2 = Temperature at the face of the fan, core stream (°F)
T12 = Temperature at the face of the fan, fan stream (°F)
T2.5 = Temperature in between the LPC and HPC (°F)
T3 = Temperature at the exit of the HPC (°F)
T4 = Temperature at the exit of the burner (°F)
T4.5 = Temperature in between the HPT and LPT (°F)
T4.9 = Temperature at exit of the LPT (°F)
TSFC = Thrust Specific Fuel Consumption
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1. Introduction
The Pratt and Whitney PW1500G is a high-bypass geared turbofan engine currently
selected as the exclusive engine for the Bombardier C-Series aircraft. At the time of this
project creation, the first engine is currently being tested in Pratt and Whitney’s outdoor
testing facilities in Florida. With the C-Series estimated entry in to service date of 2013
rapidly approaching, there is a substantial amount of work that needs to be completed.
One such task is defining a rating that will be used to determine performance (thrust
targets) of the engine. This rating will eventually be defined by low turbine rotor speed
(N1), but as an intermediate step, will be defined by burner exit temperature (T4).
The final goal of this project will be a number of T4 matrices organized into a
comprehensive ratings file. This file will be packaged in a customer simulation and
shipped to Bombardier for use in their aircraft design process. The customer simulation
is essential for accurate expectations on thrust targets, station temperatures and pressures, bleed pressures and temperatures, fuel burn, etc. Additional to the design process,
it will be used by the Bombardier engine performance group to quote aircraft thrust
capabilities to potential aircraft buyers.
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1.1 Geared Turbofan Basics
The PW1500G Geared Turbofan engine is a typical two spooled engine design with
a twist. Normal two spool engine designs are driven by two rotors, called the high spool
and low spool. The low spool is composed of the fan, low pressure compressor (LPC),
and low pressure turbine (LPT). The high spool, often called the core when combined
with the burner, is composed of the high pressure compressor (HPC) and high pressure
turbine (HPT). In the typical two spool design, all components on the low spool spin at
the same rate, referred to as the low rotor speed (N1). All components on the high spool
also spin at the same rate, referred to as the high rotor speed (N2). The figure below
shows a simplified cartoon of a two-spool engine. Additionally, the figure has numeric
station designations that will be used in the remainder of this project.
Figure 1 – Two-Spool Turbofan Cross Section with Station Designations
In the geared turbofan design, the low spool components are separated by a reduction
gearbox. In this design, the LPC and LPT will spin at the same rate, but the reduction
gearbox will create a slower spinning fan. The reason behind this design is fan bypass
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ratio (BPR). For subsonic commercial aircraft, the goal in engine design is multipronged,
but all aircraft suppliers would agree the engine needs to be as lightweight as possible
with low thrust specific fuel consumption (TSFC), while still being able to meet thrust
requirements. A high bypass ratio gives a lower exhaust speed, which helps reduce
TSFC. Unfortunately for the two spool engine design, a high bypass ratio requires a slow
spinning fan. Since the fan is driven by the LPT, to slow the fan down to an optimal
speed would require more stages on the LPT, which increases size and, more importantly, weight of the engine. By adding the reduction gearbox, the fan can spin at an optimal
speed (N1F) without needing to increase the size of the LPT.
1.2 Numerical Propulsion System Simulation
asd
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