Differences between Airline & Fighter jet turbine engines?
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Thread resume (for a moment or two anyway).
One of the other differences is not immediatey apparant in the military word.
Longivity.
Military engines, whether piston or jet, have traditionally been highly stressed. This has been to ensure, as far as practible, most power from least size/weight. The drawback from operating highly stressed engines is that they don't last as long.
As an example, some of you may remember a number of years back, CFM and Rolls-Royce were alternating adverts in Flight singing their own praises as one of their respective engines had broken new records. For RR it was a 211. For CFM it was a 56. Each manufacturer proudly stated that their engine had accomplished 30,000 hours and seven years 'on-wing' if memory serves me well. I am not aware of any military, front-line engines being this long-legged. Cue someone telling me otherwise.
Both adverts stopped around the same time...
Off thread now. With regard to the Real B0llicks 199, what a piece of tripe. A three-spool engine. WOW. Unfortunately, the IP (intermediate pressure) spool was so inefficient, it failed to contribute to engine thrust (i.e. it only produced enough to power itself). Read excess weight and wear for no performance gain. Good design, that. This is why the EJ200 is a two-spool engine (as it was designed using the 199 as a starting block).
camlobe
One of the other differences is not immediatey apparant in the military word.
Longivity.
Military engines, whether piston or jet, have traditionally been highly stressed. This has been to ensure, as far as practible, most power from least size/weight. The drawback from operating highly stressed engines is that they don't last as long.
As an example, some of you may remember a number of years back, CFM and Rolls-Royce were alternating adverts in Flight singing their own praises as one of their respective engines had broken new records. For RR it was a 211. For CFM it was a 56. Each manufacturer proudly stated that their engine had accomplished 30,000 hours and seven years 'on-wing' if memory serves me well. I am not aware of any military, front-line engines being this long-legged. Cue someone telling me otherwise.
Both adverts stopped around the same time...
Off thread now. With regard to the Real B0llicks 199, what a piece of tripe. A three-spool engine. WOW. Unfortunately, the IP (intermediate pressure) spool was so inefficient, it failed to contribute to engine thrust (i.e. it only produced enough to power itself). Read excess weight and wear for no performance gain. Good design, that. This is why the EJ200 is a two-spool engine (as it was designed using the 199 as a starting block).
camlobe
Jaguar PTR was indeed introduced as for AAR. It was found that the need to throttle the RH engine back at altitude to prevent surging left the driver without sufficient fine control of his airspeed on the LH engine- effectively he would have been at max dry or thereabouts, and any further increase in airspeed would necessitate going to Min reheat. This made the aircraft too fast. 
Solution was to provide reheat from 80%Nh or Part Throttle Reheat, thus giving the driver a much greater degree of control at a critical point in AAR. 
To ease commonality it was applied to all Jaguar engines and only required a bit of extra electrical string as far as the airframe was concerned. Think its the only type to have that facility but then when you look at the origins of the FCU its hardly surprising that little extras had to be added on to make it a militarily user friendly engine 
.
Use of 'n' is indeed as a result of maths/physics equations indicating rotational speed.
Solution was to provide reheat from 80%Nh or Part Throttle Reheat, thus giving the driver a much greater degree of control at a critical point in AAR. To ease commonality it was applied to all Jaguar engines and only required a bit of extra electrical string as far as the airframe was concerned. Think its the only type to have that facility but then when you look at the origins of the FCU its hardly surprising that little extras had to be added on to make it a militarily user friendly engine .Use of 'n' is indeed as a result of maths/physics equations indicating rotational speed.
*15-yr-old thread, resurrected by two words three posts above.
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Maybe he is a slow reader.
No one could explain why the Jag Reheat ran at a lower pressure than the main engine if i am remembering correctly. Neither Rolls Royce or the course staff.
No one could explain why the Jag Reheat ran at a lower pressure than the main engine if i am remembering correctly. Neither Rolls Royce or the course staff.
PV/T = C. Combined Gas Laws. Had a J41 type course exam question that was never in the type course requiring the theoretical knowledge of that (Mod 15 stuff) to answer it. 9 blokes on the course, I was the only bloke to get it right ( Was a temp at P3 over P2.5 or something like that, then we all moaned why it was in the exam!)
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Similar we did an exam at Halton and it mentioned Cotter pins that you naturally think push bike pedals, as we know the Americans call the split pin a cotter pin and it was mentioned in the Gnome maintenance manuals that of course we had access too, but were not in the engine build section that we did installing the turbines too etc.
