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Copy of CFM-56 Turbofan Jet Engines
Transcript of Copy of CFM-56 Turbofan Jet Engines
Clover Park Technical College
CFM-56 Turbofan Jet Engines
What are Jet Engines?
The CFM56 features a single-stage fan, and most variants have a three-stage booster on the low-pressure shaft, with four stages in the -5B and -5C variants. The booster is also commonly called the "low-pressure compressor" (LPC) as it sits on the low-pressure shaft and compresses the flow initially before reaching the high-pressure compressor. The original CFM56-2 variant featured 44 tip-shrouded fan blades, although the number of fan blades was reduced in later variants as wide-chord blade technology developed, down to 22 blades in the latest variant, the CFM56-7.
The CFM56 fan features dovetailed fan blades which allows them to be replaced without removing the entire engine, and GE/SNECMA claim that the CFM56 was the first engine to have that capability. This attachment method is useful for circumstances where only a few fan blades need to be repaired or replaced, such as following bird strikes.
The fan diameter varies with the different models of the CFM56, and that change has a direct impact on the engine performance. For example, the low-pressure shaft rotates at the same speed for both the CFM56-2 and the CFM56-3 models; however, the fan diameter is smaller on the -3, which lowers the tip speed of the fan blades. The lower speed allows the fan blades to operate more efficiently (5.5% more in this case), which increases the overall fuel efficiency of the engine (improving specific fuel consumption nearly 3%).
Diagram of the CFM-56
History of the CFM-56
-FAN AND BOOSTER-
The high-pressure compressor-HPC, features 9 stages in each variants of the CFM56. The compressor stages have been developed from GE`s "GE1/9 core" (namely a single-turbine, nine-compressor stage design) which was designed in a compact core rotor. The small span of the compressor radius meant that the entire engine could be lighter and smaller, as the accessory units in the system (bearings, oiling systems) could be merged to the main fueling system running on aviation fuel. As design evolved HPC design improved through better airfoil design. As part of the Tech-56 improvement program CFMI has tested the new CFM-56 model with six-stage high-pressure compressor stages (discs that make up the compressor system) that was designed to deliver same pressure ratios (pressure gain 30) similar to the old nine-stages compressor design. While the new one was not fully replacing the old one, it offered an upgrade in HPC, thanks to improved blade dynamics, as a part of their "Tech Insertion" management plan from 2007.
Most variants of the CFM56 feature a single-annular combustor. An annular combustor is a continuous ring where fuel is injected into the airflow and ignited, raising the pressure and temperature of the flow. Other types of combustors include can combustors, where each combustion chamber is separate, and canannular which is a hybrid of the two.
In 1989, CFMI began work on a new, double-annular combustor. Instead of having just one combustion zone, the double-annular combustor has a second combustion zone that is used at high thrust levels. This design lowers the emissions of both nitrogen oxides (NOx) and carbon dioxide (CO2). The first CFM56 engine with the double-annular combustor entered service in 1995, and the combustor is used on "Tech Insertion" CFM56-5B and CFM56-7B variants.
GE started developing and testing a new type of combustor called the Twin Annular Premixing Swirler combustor, or "TAPS", during the Tech 56 program. This design is similar to the double-annular combustor in that it has two combustion zones; however, this combustor "swirls" the flow, creating an ideal fuel–air mixture. This difference allows the combustor to generate much less nitrogen oxides than other combustors. Tests on a CFM56-7B engine demonstrated an improvement of 46% over single-annular combustors and 22% over double-annular combustors.
All variants of the CFM56 feature a single-stage high-pressure turbine (HPT). In some variants, the HPT blades are "grown" from a single crystal superalloy, giving them high strength and creep resistance. The low-pressure turbine (LPT) features four stages in most variants of the engine, but the CFM56-5C has a five-stage LPT.
This change was implemented to drive the larger fan on this variant. Improvements to the turbine section were examined during the Tech56 program, and one development was an aerodynamically optimized low-pressure turbine blade design, which would have used 20% fewer blades for the whole low-pressure turbine, saving weight. Some of those Tech56 improvements made their way into the Tech Insertion package, where the turbine section was updated. The turbine section was updated again in the "Evolution" upgrade.
The high-pressure turbine stages in the CFM56 are internally cooled by air from the high-pressure compressor. The air passes through internal channels in each blade and ejects at the leading and trailing edges.
History and Engine Specifications
Research into the next generation of commercial jet engines, high-bypass ratio turbofans in the "10 ton" thrust class, began in the late 1960's. SNECMA, who had mostly built military engines until then, was the first company to seek entrance into the market by searching for a partner with commercial experience to design and build an engine in this class.
Here is a clip of how a CFM-56 turbofan engine works.
The video showed how the air went through the air inlet then was compressed and ignited with fuel to produce thrust.
9 Rotor Stages
1 Variable IGV
3 Variable Stator Stages
5 Stationary Stator Stages
FAN AND DEBOOSTER
1 Fan Stage
1 Fan OGV
1 Booster IGV Assy
3 Booster Rotor Assy
3 Booster Stator Stages
12 Variable Bleed Valves
There are several recorded incidents of CFM56 engines flaming out in heavy rain and hail conditions, beginning early in the CFM56's career. In 1987, a double flame out occurred in hail conditions (the pilots managed to relight the engines), followed by the TACA Flight 110 incident in 1988. Both CFM56 engines on the TACA 737 flamed out while passing through hail and heavy rain, and the crew was forced to land without engines on a grassy levee near New Orleans, Louisiana. CFMI modified the engines by adding a sensor to force the combustor to continuously ignite under those conditions.
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Jet Engines are classified as gas turbines which are responsible in propelling airplanes forward.
They take in air and turn it into exhaust gases so that it can be used as kinetic energy.
This is how jet engines are able to propel huge aircraft.
Fan and Booster
Exhaust and Reverse Thrust
The CFM56 series is a family of high-bypass turbofan aircraft engines made by CFM International (CFMI), with a thrust range of 18,000 to 34,000 pounds-force. CFMI is a 50-50 joint owned company of SNECMA, France and GE Aviation (GE), USA. Both companies are responsible for producing components and each has its own final assembly line.
The CFM56 first ran in 1974 and, despite initial political problems, it is now one of the most common turbofan aircraft engines in the world, with more than 20,000 having been built in four major variants.
GE produces the high pressure Compressor, Combustor, and high-pressure turbine, and SNECMA manufactures the fan, gearbox, exhaust and the low-pressure turbine, while some components are made by Avio of Italy. The engines are assembled by GE in Evendale, Ohio, and by SNECMA in Villaroche, France. The complete dengines are marketed by CFMI.
It is most widely used on the Boeing 737 airliner and, under military designation F108, replaced the Pratt & Whitney JT3D engines on many KC-135 Stratotankers in the 1980's creating the KC-135R variant of the aircraft. It is also the only engine used to power the Airbus A340-200 and 300 series. The engine (CFM56-5A and 5B) is also fitted to Airbus A320 series Aircraft.
High Pressure System
1 OGV Assy
1 Annular Combustor
HIGH PRESSURE TURBINE
1 HPT Nozzle Assy
1 HPT Rotor Assy
LOW PRESSURE SYSTEM
LOW PRESSURE TURBINE
4 LPT Rotor Stages
4 LPT Nozzle Stages
ACCESSORY DRIVE SECTION
Although the CFM56 is a very reliable engine (CFMI) states that there is only one in-flight shutdown every 333,333 hours, there have been several engine failures throughout the life of the CFM56 family which were serious enough to either ground the fleet or require aspects of the engine to be redesigned.
A Jet Engine produces thrust.
The action is that the Jet engine generates hot exhaust gases which exit the nozzle of the engine.
The reaction is that a thrusting force is produced in the opposite direction.
Newton's Third Law
For every action, there is an equal and opposite reaction
If object A exerts a force on object B, then object B will exert a force on object A. These forces will be of the same type, equal in size, and opposite in direction.
Force = Mass X Acceleration
One issue that lead to accidents with the CFM56-3C engine was the failure of fan blades. This mode of failure led to the Kegworth air disaster in 1989, which killed 47 people and injured 74 more. After the fan blade bailed, the pilots mistakenly shut down the wrong engine, resulting in the damaged engine failing completely when powered up after descent. Following the Kegworth accident, CFM56 engines fitted to a Dan-Air 737-400 and a British Midland 737-400 suffered fan blade failures under similar conditions, although neither incident resulted in a crash or injuries. After the second incident, the 737-400 fleet was grounded.
They considered Pratt & Whitney, Rolls-Royce, and GE Aviation as potential partners, but it was not until after two company executives, Gerhard Neumann from GE and Rene Ravaud from SNECMA, introduced themselves at the 1971 Paris Air Show that a decision was made. The two companies saw mutual benefit in the collaboration and met several more times, fleshing out the basics of the joint project.
At the time it was not mandatory to flight test new variants of existing engines, and certification testing failed to reveal vibration modes that the fan experienced during the regularly performed power climbs at high altitude. Analysis revealed that the fan was being subjected to worse than expected high-cycle fatigue stresses, causing the blade to fracture; and more severe than tested for certification. Les than a month after grounding, the fleet was allowed to resume operations once the fan blades and fan disk were replaced and the electronic engine controls were modified to reduce maximum engine thrust to 22,000 lbf from 23,500 lbf. The redesigned fan blades were installed on all CFM56-3C1 and CFM56-3B2 engines, including over 1,800 engines that had already been delivered to customers.
Jet Engines have also been used in missiles, spacecrafts, fireworks and even high-speed ground vehicles.
Jet Engines are found in aircraft and are used in a variety of airplanes.
In 2002, Garuda Indonesia Flight 421 had to ditch into a river because of hail-induced engine flam outs, killing a flight attendant and injuring dozens of passengers. Prior to this accident, there were several other incidents of single or dual flame outs due to these weather conditions. After three incidents through 1998, CFMI made modification to the engine to improve the way in which the engine handled hail ingestion. The major changes included a modification to the fan/booster splitter (making it more difficult for hail to be ingested by the core of the engine) and the use of an elliptical, rather than conical, spinner at the intake.
Fan Blade Failures