QUOTE (kerran @ Feb 25 2008, 14:04 )
Vad är det igentligen som skiljer GE404 motorn från RM12...
I ett gammalt
AIAA dokument med titeln "F404/RM12 A Key Step in the F404 Growth Plans"står följande att läsa(Är från en jetmotor konferens i mitten på 80-talet):
QUOTE
As mentioned earlier, the F404/RM12 engine is being developed for use in the Swedish Air Force's JAS 39 Gripen aircraft. JAS is an acronym for Jakt, Attack, Spaning, meaning fighter, attack, reconnaissance. . . a multi-role aircraft. The prime emphasis of the JAS 39 design is in the high speed, low altitude portion of the flight envelope.
The "F404J," as it was then called, was selected by Sweden in 1981 as the engine to power the JAS 39.The main motivations for selection of an F404 derivative were cost and the operability and R&M characteristics demonstrated by the F404-GE-400 in its flight test and service experience.
The F404J design and development program was built around the unique requirements established by Sweden for the engine:
1. Provide about 10-15% higher thrust than the F404-GE-400 engine, with emphasis on "tuning" the engine for use in the lower right-hand corner of the envelope.
2. Provide backup modes to the engine control system to improve available thrust in the event of control component failures (since the JAS 39 was a singleengine aircraft).
3. Improve the bird ingestion capability of the engine.
4. Develop and qualify the engine with minimum cost and minimum change from the U.S. Navy model. The way in which GE is managing the F404/RM12 development to meet these requirements provides some good examples of how the management precepts discussed earlier are being applied.
Increased Thrust
The two major changes made to the F404/RM12 to increase the thrust of the engine were the design of a new fan and an increase in the turbine inlet tempersture.
F404/RM12 Fan
This fan designed for more than just the JAS 39 application, is a key ingredient in the overall F404 growth/ development road map. To meet the specific JAS 39 thrust requirements an increase in fan flow of 5% is required. The F404/RM12 fan is designed for a 10% increase in flow, but only 5% is used in the JAS 39.
This means that:
1. The .JAS 39 thrust requirements are met
2. The Swedish Air Force has built-in and developed growth capability of an additional 5%.
3. The F404 family of engines has a significantly improved component that can enhance the thrust of virtually any of its "base" versions by up to 10%.
Though the F404/RM12 fan's main objective is to provide a 10 % increase in airflow, the number one priority in design, development and integration of the fan continues to be operability. The F404/RM12 engine and its integration with the JAS 39 inlet system will provide the Swedish Air Force with a completely unrestricted throttle, even in backup control modes.
Additionally, a unique approach was adopted in the design of the fan by making the inlet interface configuration compatible with the current F404-GE-400 fan. This was achieved by tapering the inner hub of the flow path and by flaring out the fan case aft of the inlet lip interface. This permits the required internal flow area distribution and still allows a mechanical inlet
interface that is consistent with existing inlets that use the F404-GE-400 fan. This approach means that current aircraft inlets (e.g. F/A-18, F-20, A-6, and A-4) can take advantage of F404 growth capability with little, if any, change to the inlet design. Since the size and shape of inlets for today's military fightdattack aircraft are often restricted by integral airframdinlet bulkhead forgings, this flexibility is very important and would not have been possible without careful management of the derivative development process.
Increased Turbine Inlet Temperature
The F404/RM12 engine is scheduled to a turbine inlet
temperature nominally 75°F hotter than the F404-GE-400. In addition, a "wartime" rating of the engine allows turbine inlet temperature to increase by up to another 90°F. This increase in temperature can be adequately accommodated by the F404-GE-400 high pressure turbine buckets which are made of Directionally Solidified (DS) R80 material. These DS buckets were developed by the Navy for lifeenhancement of its F/A-l8 engines. They have been operated extensively under factory Accelerated Mission Testing (AMT) to RM12 temperature levels and have still demonstrated adequate life. Use of these buckets is an example of how the internal cross-flow of data and information between derivative applications enhances the development process. Similarly, the service experience of these buckets exposed to the Swedish mission will provide data that can be assessed and used for future derivative applications.
The Low Pressure Turbine (LPT) blade for the F404/RM12 maintains the same aerodynamic configuration as the F404-GE-400 LPT, but the buckets are manufactured from Rene 125 material which has improved high temperature capability. This approach was adopted after assessing cost and reliability against performance. Since the F404/RM12 low pressure turbine
must drive a larger fan, the optimal configuration from a performance standpoint would have been a redesigned and optimized LPT. However, because of the development and production cost impact of a newLPT and because of the confidence and excellent service experience obtained with the current F404-GE-400 configuration, the current design was selected.
Control System Backup Modes
For the JAS 39, the same basic control system philosophy as used on the F404-GE-400 is appropriate during normal operation. However, since the JAS 39 is a single-engine aircraft, the control system had to be improved to incorporate backup modes to prevent excessive thrust loss in the event of control system component failures. The F-20 program had already
faced this same issue and had developed the so-called "single-engine features" package to meet its needs.
This single-engine features package consists of a modified control system that incorporates four backup modes. TheF404/RM12 utilizes the F-20 single-engine features but upgrades it further to improve thrust available to meet the more demanding JAS 39 requirements.
This is an example of the building block approach addressed by the long-term growth road map. Starting with the F-20 developed system, the F404/RM12 has developed further improvements, including software
Logic and main fuel control scheduling cam changes. These upgrades are now planned for introduction back into the F-20 system and are the baseline for future single-engine applications of the F404, such as the A4S-1 configuration. The improvements made for one user flow across and benefit others.
Another example of the F404 integrated development approach is illustrated by development of the Digital Electrical Control (DEC), which is the heart of the single-engine features package. The DEC is being designed so that the same physical unit can be used interchangeably on an F-20 engine, on a JAS 39 engine or on an A-4s-I engine in spite of each engine having
unique T5 and NL schedules. In the case of the A-4s-1, the DEC will even be able to recognize that it is installed on a non-afterburning engine and operate in the appropriate control mode for that configuration.
En hel del har ändrats sen dess antar jag?...nytt kontrollsystem finns väl i delserie 3 bl. a.
