Originally Posted by
Turbine D
Concours77,
You are making this discussion much more complicated than it needs to be. Pratt had a problem with the initial engine design. A solution to that problem was identified and patented. It worked. It worked because of understanding what was taking place inside the engine that had to be modified. It had nothing to do with inlet stator trailing edges or feathering blades. Follow along this summary of the problem and solution:
A turbo-ramjet engine is exactly that, a turbojet working together with a ramjet to power an aircraft to Mach 3+ that could not be achieved independently of one another. To simplify this, A ramjet generates no static thrust and needs a booster to achieve a forward velocity high enough for efficient operation of the intake system. The turbojet is the booster. Ramjets generally give little or no thrust below about half the speed of sound, and they are highly inefficient until the airspeed exceeds 1000 km/h (600 mph) due to low compression ratios. The turbojet is very efficient in this regime. Ramjets work by ingesting relatively low speed air and expelling the air at a higher speed. The difference in speed results in a forward thrust. The burning fuel creates higher pressures inside the engine, causing higher exhaust speeds. But the thrust of the engine depends entirely upon how much air flows through it. No matter how hot the burning air-fuel mixture is, and how high the pressure, if not much air flows into the front of the engine not much thrust is produced. So the trick to improving ramjet efficiency is to increase airflow through the engine. This is accomplished by the spike or obstruction called an innerbody. It is pointed on both ends and thick in the middle and fits inside the intake tube. Air passing into the tube must flow around the innerbody, and the area around it is less than the area of the intake opening. Consequently the air is compressed as it flows around and reaches a maximum pressure in the narrow throat between the innerbody and the intake tube. The same amount of air flows into the engine, but it is raised to a higher pressure. This increases the pressure that the burning gasses must push against, causing the overall pressure inside the tube to increase. Higher internal pressures mean greater amounts of air in the engine, so more fuel can be burned. The result is still higher pressures, increased exhaust gas speed, and greater thrust. But there is a problem that must be dealt within the turbojet compressor area. When the pressure becomes too high in the compressor, the rotating blades tend to flutter, may break, the compressor can stall and the high temperatures can result in mechanical failures. So the P&W designers cleverly bled off air from the compressor to lower the pressure and temperature and fed it back to the burner in the afterburner section through the magical bypass tubes, it worked extremely well.
TurbineD. With great respect, you do exactly what seems to have drawn some anger when I did it. You are collecting, arranging, and repeating patent knowledge. Nothing you say is novel. It is well done, but my purpose is not to display expertise or new data on my part.
The way I approach learning is to take data in, rearrange it, and try to improve my understanding. One effective way to store it is to write about it, and see how it looks. I am not a teacher, I suck at teaching, the best I can do is try to understand what has gone before.
I really don’t care about how I look: bright, posturing, wanna be, whatever, my purpose is to increase my knowledge. I am essentially writing papers; megan was prescient when she answered lomapaseo with a “classroom” rubric.
Selfish? I don’t think so. I am taking a risk when I post here; looking or being read as stupid takes second place to my personal increase in knowledge.
best Regards,
John