Advanced Turbine Engine Gas Generator (ATEGG)

Advanced Turbine Engine Gas Generator (ATEGG) - Archived 3/2001

Outlook

Performance of XTC-66/2 during ATEGG met or exceeded Pratt’s expectations. Headed for JTDE program

Ambitious GE/Allison XTC-76/2 failed in February 1999. Now re-built and in testing

See Variants/Upgrades section for ATEGG demonstrator production information

Orientation

Description. The ATEGG program involves ongoing design, development and evaluation of turbine engine gas generators (cores, a.k.a. high-pressure (HP) sections) and related components for transition into systems development. See also Integrated High Performance Turbine Engine Technology (IHPTET) report in this Tab, as ATEGG contributes to, and is a program under, this effort.

Sponsor. The ATEGG effort is managed by the US Department of Defense through the US Air Force, Aeronautical Systems Center, Wright Laboratory, Aero Propulsion and Power Laboratory; Wright-Patterson AFB, OH, USA.

Contractors. The current contractors involved in the program are:

AlliedSignal Incorporated, AlliedSignal Engines; Phoenix, AZ, USA

General Electric Company USA, GE Aircraft Engines; Evendale, OH, USA

Allison Engine Company; Indianapolis, IN, USA

Teledyne Incorporated, Teledyne CAE; Toledo, OH, USA

United Technologies Corporation, Pratt & Whitney Group, Government Engines & Space Propulsion; West Palm Beach, FL, USA

Status. The ATEGG effort is an ongoing program.

Total Produced. Owing to the R&D nature of ATEGG, no production-standard complete engines will emerge from the program.

Application. While the primary focus of the ATEGG effort is military aircraft engines – with primary emphasis on turbofan and turbojet engines, technology developed in this effort has also has applicability to commercial aircraft engines. Applicability also extends to small gas turbine-based power packages/generator sets, marine engines, and APUs.

Price Range. Owing to the nature of this R&D effort, a price range/pricing structure is inapplicable.

Technical Data

Owing to the R&D nature of the ATEGG effort, technology developed is/will be applied to various engines. As part of the overall effort, technical goals and data are variable, depending on the demonstrator engine; as such, there is no ATEGG engine.

Variants/Upgrades

Only core gas generators have been produced under ATEGG in the first two phases. More are planned initially for Phase III. Identified cores are as follows:

Phase I

Allison XTC-15

GE XTC-45

P&W XTC-65

Phase II

Allison XTC-16 (initial Phase II core)

P&W XTC-66/1B (rebuilt from -1A version)

P&W XTC-66/SC (CAESAR core supporting JSF119)

GE-Allison XTC-76/2 (fan demonstrator)

GE-Allison XTC-76/3 (Phase II core T3 demonstrator)

Phase III

P&W XTC-67/1 (initial Phase III core)

GE-Allison XTC-77/1 (initial Phase III core)

Program Review

Background. The Advanced Turbine Engine Gas Generator (ATEGG) program has contributed to the technology of most major US engines in service or scheduled to become operational within the next several years. ATEGG was conceived in 1963 as an ongoing program to improve the technology base for aircraft engines. Part of the methodology concerns itself with competitive projects and actual hardware demonstration, which is done before a new engine enters the engineering development level.

The program, managed by USAF ASD Aero Propulsion Laboratory, currently includes Teledyne CAE, GE, Pratt & Whitney, AlliedSignal Engines (Garrett Engine Division), and Allison. Funding is provided under Program Element #0603216F, Aerospace Propulsion and Power Technology, Project 681B, Advanced Turbine Engine Gas Generator (ATEGG).

Objective of ATEGG. The overall objective of ATEGG is to provide the continued evolution of the most advanced core engine technologies – compressors, combustors, and high-pressure turbines – into an advanced gas generator in which performance, cost and durability can be assessed in a real engine environment. This critical hardware demonstration improves the early low-risk transition of these technologies to engineering development where they can be applied to derivative or totally new systems. The technologies are flexible and applicable to a wide variety of potential systems.

One of the long-range goals of the ATEGG program is the development of a variable-cycle engine, which could operate at optimum parameters throughout a greater portion of its total envelope. Some components of such an engine have already been tested, and Allison and GE continue working together on a variable-cycle engine for full testing in late 2000.

GE has built five ATEGG cores. ATEGG-3 ran in the GE23 Joint Technology Demonstrator Engine (JTDE). ATEGG-4 is in advanced development and is incorporated in the GE29, an advanced, variable-cycle turbojet based on the GE23 and targeted for supersonic cruise applications. ATEGG-5 is now known as the F120-GE-100 (formerly GE37), GE’s Advanced Technology Fighter Engine (ATFE) engine. The new Allison/GE engine, using Allison’s XTC-67/2 core, will be the latest ATEGG/JTDE engine. The goal with this demonstrator is a 60 percent improvement in thrust-to-weight ratio over an F110-GE-129, with a 34 percent improvement in specific fuel consumption.

Related Work. Activities related to the ATEGG effort include the following:

Gas generator and other engine component feasibility and practicality are demonstrated initially in Exploratory Development under USAF PE#0602203F (formerly PE#62203F), Aerospace Propulsion, in several projects, but primarily under Project 3066, Turbine Engine Technology. The other engine

subsystems such as controls, fan drive turbines and afterburners which, when added to the basic gas generator, complete the engine, are demonstrated in Advanced Development under PE#0603202F (formerly PE#63202F), Aircraft Propulsion Subsystems Integration (APSI), Project 668A. Other related work is done under PE#0602122N, Aircraft Technology, PE#0603210N, Aircraft Propulsion, PE#0603217N, Air Systems Advanced Technology Development, and PE#0603033A, Aviation Advanced Technology.

Close coordination with the US Navy, US Army, and National Aeronautics and Space Administration (NASA) will continue to ensure that resources are effectively utilized for common needs. Current and planned development efforts by the Navy and USAF’s Materials Laboratory and Flight Dynamics Laboratory directly complement the ATEGG effort.

In addition to the above efforts, the Aero Propulsion Laboratory together with the Materials Laboratory has started a new initiative directed at focusing resources toward the development of revolutionary advancements in turbine engine technology. The new initiative is the Integrated High Performance Turbine Engine Technologies (IHPTET) effort and is intended to ensure that individually developed materials and component technologies are compatible with the overall objective of a 100 percent engine technology improvement (e.g., thrust-to-weight) over the Advanced Tactical Fighter Engine (ATFE) level. Under the initiative, resources will be combined to further advances in aerodynamics, materials, and design: the ATEGG effort forms the backbone of the IHPTET initiative.

The Aircraft Propulsion Subsystem Integration (APSI) program is related to ATEGG, and includes the development of components for use in the ATEGG effort. The program falls under the management of the Air Force Aero Propulsion Laboratory, and includes such major manufacturers in the gas turbine industry as Allison, Teledyne CAE, Pratt & Whitney, GE and AlliedSignal (including the former Garrett).

ATEGG and APSI Activity. Recent and planned R&D activity for ATEGG and APSI is as follows:

ATEGG FY92 Program. The ATEGG FY92 program included the completion of testing of IHPTET Phase I Joint Technology Advanced Gas Generator (JTAGG) to provide 20 percent reduced specific fuel consumption and 40 percent power-to-weight improvement for turboprop engine cores. Applicable technologies include brush seals, non-metallic combustor panels, and super-cooled turbine technologies. Other efforts included the fabrication of the Allison IHPTET Phase II dual annular lamilloy combustor that increases temperature capability by 500°F over baseline; the fabrication of the Allison IHPTET Phase II all-metal matrix composite compressor yielding 25 percent improvement in work per stage with associated thrust-to-weight and reliability increases; and the fabrication of the P&W IHPTET Phase II high work turbine with a 500°F increase in rotor inlet temperature capability or full life capability at today’s temperature levels.

ATEGG FY93 Program. The ATEGG FY93 program was established to demonstrate a turbofan/turbojet core with an overall 30 percent increase in thrust-to-weight, 23 percent reduction in fuel consumption, and 10 percent reduction in life-cycle cost. Applicable technologies include intermetallic compressor blades, brush seals in the turbine section, a swept aerodynamic compressor, bonded single crystal turbine blades, an effusion cooled combustor, ceramic ball bearings, and magnetic bearings. Other efforts included engine test of Allison IHPTET Phase II compressors using metal matrix rotor structures providing a 40 percent weight reduction and reduced parts count for improved reliability; structural and life assessment on IHPTET Phase I ATEGG core to demonstrate equivalent ATF engine life; engine test of P&W IHPTET Phase II axial staged combustors reducing cooling air requirement by 70 percent and length by 20 percent; engine test of P&W IHPTET Phase II high work turbine design with cooling schemes to provide a 500°F temperature improvement with corresponding 3 percent reduction in blade cooling; and continuation of JTAGG IHPTET Phase II testing demonstrating a 25 percent reduction in specific fuel consumption and 60 percent power-to-weight improvement.

ATEGG FY94 Program. The ATEGG FY94 program involved engine test of an axial-staged combustor that improves cooling airflow by 70 percent, improves emissions, and is 20 percent shorter; engine test of a +300°F metal matrix composite (MMC) compressor rotor providing a 20 percent reduction in weight and reduced spare parts count for improved reliability; core testing of a next-generation turboprop demonstrator engine having a 25 percent reduction in SFC and a 60 percent increase in power-to-weight ratio. Applicable technologies include an aerodynamic compressor, bonded single crystal turbine blades, a ceramic combustor, and ceramic ball bearings. Other efforts include the design of affordable turbofan/turbojet core engines utilizing such advanced technologies as MMC compressor rotors, ceramic combustor liners, and composite reinforced turbine disks. The goal is to reduce engine fuel consumption by 30 percent, increase thrust-to-weight ratio by 60 percent, reduce engine life-cycle cost by 20 percent, and decrease engine acquisition cost per pound of thrust by 30 percent.

ATEGG FY95 Program. The ATEGG FY95 program called for a continuation of the efforts conducted in FY94. Individual tasks were not identified, and no new initiatives were identified for FY95.

ATEGG FY96 Program. The ATEGG FY96 program objective was to design, fabricate, and test technology demonstration core engines for turbojet/turbofan engines for fighters, attack aircraft, and large transports. A total of $30.3 million was budgeted for this task. Individual projects supporting this effort included:

Fabrication of turbofan/turbojet core engine hardware (flexible, variable-cycle core; high-temperature metal matrix composite compressor rotor; low-pressure section turbofan/turbojet core engine hardware (titanium aluminide [TiAl] compressor blades; super-cooled turbine components; Lamilloy turbine vanes) in support of durability core engine testing in FY97.

Design, fabrication, and demonstration of core engines for turboshaft, turboprop, and small turbofan engines for trainers, rotorcraft, special operations aircraft, and theater transports ($1.5 million).

ATEGG FY97 Program. Accomplishments for 1997 included the following tasks, funded at $28.894 million total: Tested a turbofan/turbojet engine core demonstrating a 60 percent increase in thrust-to-weight ratio, a 20 percent reduction in manufacturing costs, and a 20 percent reduction in maintenance cost ($23.4 million); tested demo core fighters, trainers, bombers and transports and conducted a high-temperature durability test of this core demonstrating critical technology potential life characteristics ($4.2 million); tested a smaller core for turboshafts/turboprops, demonstrating a 30 percent reduction in fuel consumption and an 80 percent increase in power to weight ratio ($1.2 million).

ATEGG FY98 Program. Under the ATEGG FY98 program, durability and performance testing of turbofan/turbojet core engines was conducted to demonstrate improved performance and lower fuel consumption GTs for all aircraft types ($26.8 million).

These tests were to include the fabrication of hardware (high-temperature metal matrix composite compressor rotor, dual alloy turbine disk) and assembly of a core engine for high compressor exit temperature testing (30 percent reduction in fuel consumption). They were also to include the design and fabrication of core engine hardware (high-stage loading compressor, dual-web turbine disk, air-to-fuel heat exchanger) in support of core engine testing. Objectives were a 40 percent reduction in fuel consumption, a 100 percent increase in thrust-to-weight ratio, a 35 percent reduction in manufacturing cost, and a 35 percent reduction in maintenance cost.

The objective of the testing of a turboprop/turboshaft core engine was a 28 percent reduction in fuel consumption and an 102 percent increase in power-to-weight ratio.

Another task in FY98 was the design (or continuance of design work) of a turboprop/turboshaft core engine demonstrating a 40 percent reduction in fuel consumption, a 120 percent increase in power-to-weight ratio, a 35 percent reduction in manufacturing costs, and a 35 percent reduction in maintenance cost.

ATEGG FY99 through FY2001 Programs. The ATEGG FY99 and FY00 programs plans are very generic, and are exactly the same in the FY2000 PEDS. Descriptors from FY99 are expected by Forecast International to be accurate for each year. The following activities were collectively funded at (USAF estimate) $31.4 million for FY99, $33.4 million for FY2000, and $34.3 million for FY2001:

Fabricate hardware for and advanced core engine with a high-stage loading compressor, dual web turbine disk, and air-to-fuel heat exchanger to provide an initial assessment of the technologies required to provide a 40 percent reduction in fuel consumption, a 100 percent increase in thrust-to-weight ratio, a 35 percent reduction in manufacturing cost, and a 35 percent reduction in maintenance costs (FY99: $25.558 million, FY00: $26.918 million, FY01: $24.663 million).

Conduct high-exit temperature testing (30 percent reduction in fuel consumption) of an advanced core engine with a high-temperature metal matrix composite compressor rotor and an advanced nickel turbine disk ($7.847 million).

Test a turboprop/turboshaft core engine demonstrating a 30 percent reduction in fuel consumption, a 112 percent increase in power-to-weight ratio, a 20 percent reduction in manufacturing cost, and a 20 percent reduction in maintenance cost. Also, complete the design of a turboprop/turboshaft core engine with a 40 percent reduction in fuel consumption, a 120 percent increase in power-to-weight ratio, a 35 percent reduction in manufacturing cost, and a 35 percent reduction in maintenance cost ($3.921 million).

APSI FY92 Program. The APSI FY92 program included the fabrication of hollow titanium metal matrix composite fan blades for P&W JTDE. The blades will save 46 percent (95 lb/43 kg) in weight compared to conventional solid titanium blades. Also in FY92, engine tests on lightweight metal matrix composite support structures were completed. These tests demonstrated increased vibration damping capability with a 25 percent (80 lb/36.2 kg) weight reduction; Testing of carbon/carbon turbine for man-rated engines was also completed, providing a 45 percent weight reduction and the elimination of cooling air. Finally, other activities in FY93 included the preliminary design of dry super-cruise technology configuration with low subsonic/supersonic fuel consumption and high thrust-to-weight capability for tactical fighters, and the fabrication and initial assembly of next-generation expendable demonstrator engines.

APSI FY93 Program. The APSI FY93 program included the conduct of expendable missile demonstrator engine testing of the Advanced Exhaust System Cooling Concept to reduce cruise missile infrared and radar cross-section signatures, and the demonstration of fighter engine technologies with a 30 percent increase in thrust-to-weight and a 20 percent fuel savings. Applicable technologies include hollow metal matrix composite compressor fan blades, transpiration cooled turbine vanes, super-cooled blades, and multifunction nozzles. Other FY93 activities included the fabrication of advanced capability exhaust systems incorporating composite and metallurgic structures technology and providing significant reductions in weight, cooling flow, cost, and observables for man-rated systems; fabrication of super-cooling turbine components for a 3-SR life improvement and a 20 percent increase in thrust for current fighter engines and derivatives; and the conduct of initial testing of expendable missile demonstrator engines with a capability of 70 percent specific thrust improvement and 30 percent reduction in fuel consumption.

APSI FY94 Program. The APSI FY94 program included testing of an advanced spherical convergent flap nozzle; the preparation of tests of super-cooled turbine components; the detailed design of next-generation JTDE configurations which will include a 60 percent thrust-to-weight-ratio improvement; and the demonstration of fighter engine technologies with a 33 percent improved thrust-to-weight ratio and 20 percent fuel savings. Applicable technologies include hollow metal matrix composite fan blades, transpiration-cooled turbine vanes, and multifunctional nozzle components. Finally, the first ever composite turbine engine fan/compressor intermediate case was tested, providing a 20 percent weight savings and improved vibration resistance.

APSI FY95 Program. The APSI FY95 program included the design, fabrication and demonstration of fans, low-pressure turbines, engine controls, and exhaust nozzles, and the integration of technology for turbofan/turbojet engines for Air Force aircraft ($4.35 million). The goals of these tasks were:

Fabrication and demonstration of a low-signature, lightweight axisymmetric nozzle.

Rig-test of an advanced-concepts fan incorporating two-stage swept aero fan technology.

Design, fabrication, and test of technology demonstration engines for fighters, attack aircraft, bombers and transports ($20.82 million – dropped to $20.03 million in 1997).

Fabrication and demonstration of a swept aerodynamic fan with hollow metal matrix composite blades.

Fabrication and demonstration of advanced, high-flow-through fan and high-stability fan casing and treatment.

Fabrication and demonstration of advanced low-pressure turbine cooling technology.

Design of forward-swept fan technology.

Design of Castcool, Nickel Aluminide, and Internal Convective Enhancement (ICE) turbines.

Design of integration technologies including metal matrix composite shafts, hybrid ceramic bearings, and counter-rotating vaneless turbines.

Also in FY94, a variable cycle engine with fixed geometry, fluidic area control, and fluidic thrust vectoring exhaust nozzle technologies was designed, and expendable missile engines were designed, fabricated, and demonstrated. A total of $4.22 million was budgeted for this effort (dropped to $3.94 million in 1997). The goals of this effort were:

The design of a carbon/silicone carbon (CSiC) exhaust nozzle and high-flow-through combustor.

The design of an efficient, lightweight, low-cost Lamilloy hot section, including first use of MA754 sheet material for a turbine nozzle.

APSI FY96 Program. The APSI FY96 program tasks were the same as those outlined for 1995. A total of $4.1 million was budgeted for aircraft engine technology programs, and $4 million for expendable missile engine technology programs.

APSI FY97 Program. The APSI FY97 program called for the completion of all efforts outlined in FY95 under the aircraft engine technology program, with $20.3 million budgeted for these programs; the demonstration of all technologies outlined for FY95 under the expendable missile engine technology programs, with $3.9 million budgeted for these efforts; and the demonstration of fans, LP turbines, engine controls, and exhaust nozzles and the integration of technology for turbofan/turbojet engines for USAF aircraft, budgeted at $4 million.

APSI FY98 Program. The FY98 ATEGG program goals, funded at $23.3 million, included the following: the integration of technologies including metal matrix composite shafts, hybrid ceramic bearings, and counter-rotating vaneless turbines; demonstration of a variable cycle engine with a swirl augmentor and fixed geometry thermal and fluidic area control exhaust nozzle; demonstration of model based, distributed and active stability engine controls; design, fabrication and testing of technology demonstration engines for missiles and uninhabited air vehicle applications; design of a high- temperature shrouded compressor; design of a low-cost ceramic matrix composite combustor; design of a low-cost, high-efficiency uncooled carbon-carbon turbine; design of a rich burn nozzle and controls for thrust augmentation.

APSI FY99 Program. The FY99 ATEGG program goals, funded at $30.8 million, included the following:

Demonstration of model-based, distributed and active-stability engine controls; design of integral starter/generator; and conduct of preliminary design for fully distributed and active stability engine controls ($4.148 million).

Demonstration of laser-spot peening; demonstration of MMC composite shafts, hybrid ceramic bearings and a counter-rotating vainless turbine; and conduct of preliminary design of more affordable integration technologies, including composite hot-section components, an advanced fan, and low observable exhaust nozzles ($10.136 million).

Demonstration of a variable-cycle engine with a swirl augmentor and fixed geometry thermal and fluidic area control exhaust nozzle; and design, fabrication and demonstration of advanced hot-section cooling system ($11.306 million).

For missile and UAV engines: fabrication of high-temperature shrouded compressor; fabrication of low-cost CMC combustor; fabrication of low-cost, high-efficiency, uncooled carbon-carbon turbine; fabrication of a rich burn nozzle and controls for thrust augmentation; and fabrication of affordable, high-temperature-capable components with reduced cooling requirements ($5.224 million).

APSI FY00-01 Programs. The goals for FY2000 and FY2001 are identical in each category.

Design, fabrication and demonstration of durability and integration technologies for turbofan/turbojet engines for improved supportability and affordability of USAF aircraft. (FY00: $4.2 million; FY01: $5.5 million).

Design, fabrication and test of advanced component technologies for improved performance and fuel consumption for turbofan/turbojet engines for USAF aircraft (FY2000: $20.8 million; FY2001: $19.8 million).

Design, fabrication and test of advanced component technologies for improved performance and fuel consumption for engines for missile and uninhabited air vehicle applications (FY2000: $4.6 million; FY2001: $5.6 million).

Funding

Recent and current funding for ATEGG (PE#0603216F, 681B) and APSI (PE#0603202F, 668A) is as follows (as identified in the US Air Force’s FY2000/2001 PEDS):

US AIR FORCE FUNDING

                      FY95    FY96    FY97    FY98    FY99    FY00     FY01
                                              (Est)   (Req)   (Req)    (Req)
                       AMT     AMT     AMT     AMT     AMT     AMT      AMT

RDT&E
PE#0603202F,668A 27.6 31.1 23.9 22.2 27.7 29.8 31.0
PE#0603216F,681B 27.2 30.0 28.8 26.8 31.4 33.4 34.3

                      FY02    FY03    FY04    FY05
                      (Req)   (Req)   (Req)   (Req)
                       AMT     AMT     AMT     AMT

RDT&E
PE#0603202F,668A 25.4 20.0 13.7 14.1
PE#0603216F,681B 32.0 27.6 21.8 22.5

All $ figures are in millions of FY00 US dollars.

Funding prior to FY95 was as follows:

ATEGG: FY90, $23.7 million; FY91, $21.9 million; FY92, $23.4 million; FY93, $26.553 million; FY94, $28.74 million.

APSI: FY90, $20.5 million; FY91, $20.3 million; FY92, $25.3 million; FY93, $26.279 million; FY94, $26.45 million.

Recent Contracts

Recent contract activity involving the ATEGG effort is as follows:

Date	Contractor	Contract	Amount^(a)	Expiration Date
04/25/95	P&W	F33615-95/C-2503	17.8	October 1999
02/17/95	GE/Allison	F33615-95/C-2502	43.2	-

^{(a)All $ in millions of then-year US dollars.
Recent Activity. Recent activities within and relevant to the ATEGG effort include the following:

The Lubrication Branch (AFRL/PRSL) of the USAF recently awarded a Phase II SBIR contract to Mohawk Innovative Technology Inc, for the development of a high-temperature zero clearance auxiliary bearing (ZCAB). Under this contract, Mohawk will continue the development of the ZCAB, a device intended to provide a low maintenance backup bearing for turbomachinery supported by magnetic bearings. The target application for this bearing technology is the hot section in the second build of the Integrated High Performance Turbine Engine Technology (IHPTET) Phase III Advanced Turbine Engine Gas Generator (ATEGG) demonstrator. Since both General Electric and Allison Advanced Development Company have a vested interest in the ATEGG Phase III demonstrator, they will participate in the ZCAB development. Having all of the concerned parties involved in the ZCAB development and design should enhance the probability of a successful program. (R. Wright, AFRL/PRSL, (937) 255-5568).
* * *
Testing of four different Trapped Vortex Combustor (TVC) geometries in the Propulsion Directorate’s High Pressure Combustion Research Facility was recently completed. During this testing, which started in July 1998, Combustion Branch (AFRL/PRSC) engineers collected performance, stability, and temperature data for each of the four 12-inch-sector geometries over a range of conditions. Tests were conducted at pressures ranging from 3 psia, simulating an altitude of about 40,000 feet, to 300 psia with inlet air temperatures ranging from 70° F to 1,150° F. The TVC sectors logged over 250 hours of hot test time during the program. The test results have demonstrated the feasibility of the TVC for both military and commercial gas turbine applications.
In testing, the overall fuel-to-air ratio, combustor flow loading, cavity-main air split, and main combustor were investigated using emissions sampling, temperature profiling, and lean blow-out tests. Measured combustion efficiencies ranged from 88 percent to more than 99 percent depending on the flow conditions.
The TVC is an innovative combustor concept conceived to improve flame stability and reduce undesirable emissions (e.g., NOx, volatile organic compounds, and carbon monoxide). The TVC’s simple geometry also offers the potential benefit of reduced production cost, as well as a much shorter engine, and therefore a significant weight reduction.
GEAE and AFRL/PRSC are redesigning the integrated diffuser injector flameholder (IDIF) for the TVC. The IDIF supplies the main air and fuel flows to the combustor. The current IDIF and fuel injection system, although performing well, can be enhanced significantly, yielding further reductions in NOx and better combustion efficiency over a wider fuel-to-air ratio range. The Universal Dome, or new IDIF, will most likely be either a perforated plate of AFRL design or a swirl-cup diffuser of GEAE design. Both designs will be evaluated in AFRL/PRSC’s in-house facilities. AFRL/PRSC will be designing a set of diffuser plates with different arrangements of fuel and air injection to be evaluated in both the atmospheric-pressure and high-pressure combustion facilities over the next two years. (Capt I. Vihinen, AFRL/PRSC, (937) 255-8623).
* * *
Saddleback Aerospace, in cooperation with Pratt & Whitney (P&W) and the Air Force’s Turbine Engine Division, has been working on a Phase I SBIR program aimed at improving its Advanced Integrated Fuel System (AIFS) heat exchanger technology and tailoring its development to the Integrated High Performance Turbine Engine Technology (IHPTET) program. In one engine cooling concept, fuel is used as a coolant in a fuel/air heat exchanger. Care must be taken to prevent hot spots in the heat exchanger as they can cause the fuel to form deposits that degrade heat exchanger performance. Saddleback’s innovative concept will feature an improved heat exchanger core designed to yield uniform heating of the fuel by grading the heat transfer coefficient across the core. Uniform heating minimizes hot spots in the heat exchanger and thus helps prevent deposition. The improved heat exchanger capability offered by this concept will also allow for higher bulk fuel temperatures. Other key features include vacuum safety circuits that will minimize engine risk while the heat exchanger is in operation. This innovative heat exchanger core technology will also be applicable to many other thermal management system applications such as chemical processing plants. Success in this Phase I SBIR effort may lead to continued development of this concept for possible insertion in P&W’s Advanced Turbine Engine Gas Generator (ATEGG) IHPTET demonstrator by the 2000-01 time frame. (C. Arana, AFRL/PRTC, (937) 255-5974).
* * *
Pratt & Whitney tested a modified version of its XTC-65/2 core during 1995, dubbed XTC-66. The modified core was to demonstrate high-pressure turbine temperatures, which in turn would support advances under IHPTET. This demonstrator failed during testing, however, due to a materials failure. Testing of a second build of the XTC-66 core began in September 1997 to demonstrate improved compressor, combustor, and turbine technologies in an advanced flowpath design. Key technologies include the use of metal matrix composites, as well as electronic engine monitoring, for pinpointing operating inefficiencies and predicting failures through heat and stress analysis. This work is contributing to Pratt’s CAESAR (Component And Engine Structure Assessment Research) program which was created by the US Air Force’s Wright Laboratory and P&W to assess promising propulsion technologies in a structurally demanding environment.
CAESAR is part of the DoD/NASA/Industry IHPTET program. CAESAR (XTC-66/1B) testing focused on gamma titanium aluminide components in the compressor, and on current and advanced cooling system blades and vanes in the high-pressure turbine of the F119 demonstrator engine for JAST. Testing of this core, as configured when it first went to test in September 1997, ran into February 1998. The core was 3D mapped, and then incorporated into the XTE-66 JTDE.
Timetable
The ATEGG program began in 1963. According to the US Air Force’s FY00 PEDS, the ATEGG schedule was:

Month

Year

Major Development

Apr

1994

Initiate testing of next-generation turboshaft/turboprop core

Feb

1995

Conduct testing of next-generation turbofan/turbojet core (+60 percent power-to-weight, -25 percent SFC)

Apr

1995

Conduct testing of turbofan/turbojet core with transpiration-cooled combustor and turbine at +600°F

Sep

1995

Conduct steady-state durability testing of advanced turbofan/turbojet core (50 hours maximum temperature)

Sep

1996

Conduct turbofan/turbojet core cyclic durability testing (2,000 cycles); conduct testing of turboshaft/turboprop core (+80 percent power-to-weight, -30 percent SFC)

1997

Design, fabricate and test forward-swept fan technology; and variable-cycle engine with fixed geometry, fluidic area control, and fluidic thrust varying technologies

1998-99

Design, fabricate and test demo cores for improved performance, durability and fuel consumption for fighters, bombers, tankers and transports, special ops, and UAV aircraft

Worldwide Distribution
Owing to the R&D nature of the ATEGG effort, no production-standard engines have emerged from the program.
Forecast Rationale
Looking at the two major teams producing ATEGG cores, we see Pratt & Whitney and GE/Allison rising admirably from the setback of core engine failures. Both companies are gleaning much useful technology from these demonstrator cores under the Integrated High Performance Turbine Engine Technology (IHPTET) program.
Pratt & Whitney experienced a failure of its XTC-66/1 core in 1995, and has done very well to date in gathering meaningful results from changes incorporated in its predecessors.
Pratt has tested its latest XTC-66/1B core with swept blades and remodeled stators using Nastran aerodynamic codes. The compressor’s flowpath contours were also changed. Equally important was the "super cooling" technology applied to the conventional, single-stage turbine blades. The single-pass channel cooling passages (rather than serpentine channels) used allow narrower blades which can be tapered.
Titanium was used in the first two HPC stages, with nickel-based superalloys in the last three (the failed unit used reinforced metal matrix composites, a disk of which debonded, destroying the earlier core during a run in 1995). The redesigned XTC-66/1B has demonstrated the highest pressure rise of any P&W compressor ever, handily meeting Stage II requirements. Efficiency goals were also met, and stall margins were exceeded.
An axially staged combustor (20 pilot nozzles/20 main nozzles) was successfully tested as well, demonstrating reduced NOx. This was accomplished with a hotter burn in a shorter length of space/time (lower residence time). Pratt is using the dual combustor in the XTE-66 JTDE, but advanced combustion tools indicate that a simpler, single-stage combustor can be made to achieve the same temperature rise.
Pratt’s XTC-66 embodies the core technology used in the PW6000/8000, as well as the developing 25,000-30,000 lbst PW7000 military turbofan. The PW7000 is viewed as a future GE F414 competitor. Some of the technology (such as the microwave ignitor and vaneless LP turbine) could also be incorporated into the JSF119 engines in years to come. The blade shaping and supercooling technologies clearly have commercial engine potential.
The GE/Allison team experienced a failure of their XTC-76/1 core in early 1998. A tear-down of the core in early 1998 was followed by full mapping, and a decision to mate the core with an LP section for testing in the Joint Technology Demonstrator Engine (JTDE) portion of the program in mid-1999.
Unfortunately, a failure of their XTC-76/2 core occurred in February 1999. The team was rebuilding the core in 1999 for testing in early 2000, followed by mating with LP components for testing of the XTE-76 JTDE late in 2000.
One cannot consider the XTC-76 core without considering the intent of the design of the XTE-76 engine.
GE remains committed to its two-stage fan concept first embodied in its XF-120 Advanced Tactical Fighter engine. Two forward-swept-bladed fans are employed. The second, a core-driven fan, is at the front of the engine’s air bypass duct. Airflow to the fan is regulated by inlet vanes, which are fully adjustable to regulate flow to the turbine. The benefits of this fan arrangement are two-fold. First, the work done by the LP turbine is matched to the core’s load, which equates to much higher engine efficiency in cruise conditions. Second, a simpler, fixed-area exhaust nozzle can be used, which is lighter and much less costly to furnish and maintain than a variable nozzle. The fan’s bypass air also keeps the LP turbine running cooler for the most part, thus lasting longer and likely requiring less maintenance.
The combustor employs aerodynamic fuel mixers, or swirlers, rather than mechanical fuel nozzles. Aerodynamic fuel/air-mixing was adopted and refined by Allison to reduce complexity and cost. The five HP compressor stages are all one-piece blade-in-disk (BLISK). Two of the five are joined, doing away with bearings and flanges. Bearings used in the HP compressor are made of silicon carbide, held in very high-speed-tolerant metallic races. GE is also using a metal matrix composite LP shaft made of a titanium matrix reinforced with silicon carbide fibers. The materials make a lighter shaft, having the strength for a smaller diameter. Like P&W with the XTE-66, GE eliminated vanes between the two turbine sections.
Some of the IHPTET technologies already selected to be used in the XF120 are bi-directional taped roller bearings, the HP compressor from GE’s XTC45-1/2 ATEGG demonstrator, a Lamilloy combustor and turbine vanes, and a contra-rotating turbine section with no vanes between the HP and LP sections (the computational model which designed this came from IHPTET, not the turbine design itself).
It should be noted that the technology from the ATEGG effort will also find its way into the commercial engines of the programs’ participants. Future tasks of ATEGG will undoubtedly be structured for dual, military/ commercial engine applications.
Ten-Year Outlook
The ATEGG program will not result in production-standard engines, and therefore cannot be assessed on that basis for a forecast.
* * *}

Month	Year	Major Development
Apr	1994	Initiate testing of next-generation turboshaft/turboprop core
Feb	1995	Conduct testing of next-generation turbofan/turbojet core (+60 percent power-to-weight, -25 percent SFC)
Apr	1995	Conduct testing of turbofan/turbojet core with transpiration-cooled combustor and turbine at +600°F
Sep	1995	Conduct steady-state durability testing of advanced turbofan/turbojet core (50 hours maximum temperature)
Sep	1996	Conduct turbofan/turbojet core cyclic durability testing (2,000 cycles); conduct testing of turboshaft/turboprop core (+80 percent power-to-weight, -30 percent SFC)
	1997	Design, fabricate and test forward-swept fan technology; and variable-cycle engine with fixed geometry, fluidic area control, and fluidic thrust varying technologies
	1998-99	Design, fabricate and test demo cores for improved performance, durability and fuel consumption for fighters, bombers, tankers and transports, special ops, and UAV aircraft