This seminar attempts at highlighting the various aspects of the engine by presenting a brief insight into its features.

HIGH THRUST CLASS TURBOFAN ENGINES (> 200 kN) (modified after [2])

• gives improved fuel consumption.
• better engine control and reduces pilot work load by interacting with aircraft computers.
• lower aircraft operating costs.

LOW THRUST CLASS TURBOFAN ENGINES (< 200 kN) (modified after [2])

Following are the results of a simple high bypass ratio turbofan engine cycle analysis carried with the help of a computer program. The theory of the analysis can be found in [3]. A more extensive and accurate analysis can be obtained from [4]. The available data on the GE90 engine was merely limited to its take-off thrust, bypass ratio (BPR) and overall pressure ratio (OPR). The rest of the data is tentative and is assumed on the basis of other similar GE engines (like CF6-80C2 and CFM56) with the appropriate improvements considered.

Intake efficiency = 0.980

Fan polytropic efficiency = 0.930

Compressor polytropic efficiency = 0.910

Turbine polytropic efficiency = 0.930

Isentropic nozzle efficiency = 0.950

Mechanical efficiency = 0.990

Combustion pressure loss (ratio) = 0.050

Fuel combustion efficiency = 0.990

Area of hot nozzle = 1.0111 m²

Area of cold nozzle = 3.5935 m²

CERTIFICATION ([1] and [2])

With FAA certification of the GE90, GE Aircraft Engines brought to close one of the most extensive ground and flight test programs ever undertaken by an engine manufacturer.

GE announced the development of the GE90 in January 1990. In November 1992, the first full-scale engine core went to test; the first full engine followed in March of 1993. Since that time, GE and its revenue sharing participants have run a total of 13 development engines which have verified the engine’s inherent design benefits. Overall, the engines have logged more than 5,000 hours, including 228 flight hours on GE’s modified Boeing 747 flying test bed.

GE90 endurance engines completed more than 14,000 cycles and demonstrated excellent section durability. Seven engines have operated at more than 100,000 lb. (444.5 kN) of thrust, with one achieving a record-breaking 110,000 lb. (489 kN) of thrust. In fact, GE90 development engines have sustained thrust levels in excess of 100,000 lb. (444.5 kN) for more than 65 hours.

As part of the required certification testing, the GE90 successfully completed both the 2.5 and 8 lb. (1.13 and 3.63 kg) bird ingestion tests on the engine’s composite blades.

In October 94, four 2.5 lb. birds were ingested with the engine running at speeds required to produce 85,000 lb. (377.8 kN) of thrust at takeoff on a hot day. There was no thrust loss and the engine responded to all throttle commands during the required 20 minutes of operation following the ingestion. All fan blades were in excellent condition and have continued to run in other engine tests.

In mid-November 94, GE conducted the fan bladeout test with the FAA present. The release blade was detonated at a fan speed of 2,485 rpm, 10 rpm over the target, with the engine generating more than 105,000 lb. (466.8 kN) of sea level static (SLS) corrected thrust. The engine mount system performed as designed and the test demonstrated fan blade containment. The ruggedness of the composite fan blade was successfully demonstrated, and the observed trailing blade damage matched pre-test analysis, verifying the inherent benefits of the composite blade design.

The GE90 flew for the first time in late 1993 installed on the 747 flying testbed. Throughout the first phase of testing, the engine accumulated nearly 228 hours in 45 flights. The engine performed exceptionally well, demonstrating performance levels that were better than specification and provided pilots unrestricted throttle movement throughout the flight envelope.

• Common engine for entire families of new, larger aircraft.
• New widebody aircraft demand 20-30% higher thrust than today’s engines.
• Aircraft historically require 20-30% additional thrust for increases in TOGW.

Modern cycle design has built-in total performance advantages

• 10% better SFC than today’s engines.
• High thrust growth with commonality.
• Low noise and emissions.

Reliability of Proven Technology incorporating "Lessons Learned".

The GE90 is designed for :

• Thrust Growth.
• Engine commonality for the 777 Airplane Family.
• Fuel Efficiency.
• 180-Minute ETOPS (Extended Twin OPerationS).
• Low Emissions.
• Low Noise.
• Reduced Operating Cost.

Cycle Selected for significant fuel savings.

• Bypass ratio optimized.
• Overall pressure ratio optimized.
• Designed for lowest SFC and fuel burn.

Designs selected for maximum airline benefit.

• Designed and demonstrated technologies for high reliability.
• Builds on CF6 and CFM56 reliability.
• ETOPS approval.
• Operator developed maintenance procedures.
• Designed for low noise and low emissions.
• Designed for Lowest Operating Cost.

Engine Sized For Future Aircraft Requirements.

• Initial certification at 84,700 lb. (376.5 kN) thrust - February 1995
• First growth certification at 92,000 lb. (408.9 kN) thrust - May 1996.
• Potential to grow to 120,000 lb. (533.4 kN).

• Over 145 Hours at > 422.3 kN
• Over 95 Hours at > 435.6 kN
• Over 75 Hours at > 440.0 kN
• Over 65 Hours at > 444.5 kN
• 20 Hours of Continuous Running on 900-105/1A at > 444.5 kN

Note : Sea Level Static (SLS) Corrected Thrust Levels

Eight GE90 engines have operated at or above 445 kN of SLS Thrust.

• Fan Mapping.
• Booster Stress Survey.
• Overspeed Certification (490.3 kN).
• "Dress Rehearsal" for Triple Redline Block Test.
• 1.13 kg Bird Certification / Blade Out Certification.

THE ENGINE AND ITS COMPONENTS ([2])

The following are the main components of the engine -

1. Composite fan

2. Low Pressure Compressor (LPC) / Booster

3. High Pressure Compressor (HPC)

4. Dual Dome Combustor

5. High Pressure Turbine (HPT)

6. Low pressure Turbine (LPT)

• 22 composite wide-chord blades and platforms.
• Large fan diameter for higher air mass flow.
• Fan geared - reduces fan tip speed thus producing less noise.
• Low tip speed and pressure ratio for quiet efficient operation.
• Lightweight tri-web disk for inspectibility and reduced weight.
• Hybrid (conical/elliptical) spinner for low core debris ingestion.
• Fan Pressure Ratio (FPR) about 1.60-1.65 (tentative).

• Wide Chord Composite Fan - high performance and low weight.
• Environmental resistance - GE90 fan material system displays equal environmental resistance like those of current aircraft composites.
• GE90 fan composite material system demonstrated similar to those currently in service.
• Laminated specimens fully exposed to aircraft fluids typically maintained 95 percent base properties.
• Actual blade fully protected by polyurethane coating.
• No exposure to ultraviolet radiation.

• GE90 Composite Blade Benefits from 25 Years of Development.
• Materials, manufacturing and computing advances have provided the necessary technology.

OTHER FEATURES ([2])

Reduced Emissions and Smoke

• Dual Dome Combustor.
• Reduced Noise.
• Low Fan Pressure Ratio and large aspect ratio low pressure turbine.
• Overall lower mission total fuel burn = Lower total mission pollutants.
• Higher thrust to core flow ratio.

GE90 Combustor Provides Improved Operability with Reduced Emission Levels

• Double Annular Combustor.
• Pilot dome optimized for operability - main dome optimized for high power.
• Emissions reduction Based on 15 years of NASA and Advanced Military Engine Development.
• Full-scale GE90 Testing.
• Exit temperature profiles meet design intent.
• Emission levels verified.

• Smaller than the high bypass turbofans of today

• Allows replacement of propulsor only
• Separate Propulsor/Nozzle from Fan Stator Module
• Fan stator module remains at main base or with aircraft
• Removal and Replacement Time Estimated at Less than 6 Hours

GE90 components are sized for growth. If the market requires it, 110,000 lb. (511 kN) of thrust could be produced by a GE90 with further investment. The following are the ways General Electric intends to achieve the thrust increment -

• 376.5 kN Fan

• 409 kN Fan

• 422.3 - 435.6 kN Fan

• 466.8 kN Fan

• 511.2 + kN TF

It is seen that GE90 is indeed the most powerful and efficient commercial transport engine of the 90’s. It also has ample scope for thrust growth to keep up with the future requirements. Although unavailability of exact technical information on the engine such as its weight, pressure ratio, TIT, cruise thrust, s.f.c, etc. render the data in this report tentative, its comparison with other engines clearly shows that it is a class apart from them in terms of thrust and fuel efficiency.