Originally Posted by downwardspiral
AHEM lol
ramjet engine
Unfortunately there are two things that work against the ramjet:
- Operating Speed
Unlike pulsejets and jet-turbine engines, the ramjet will not operate unless it is moving through the air at a speed of at least 400 mph.
If you attempt to start a ramjet while it's stationary or moving to slowly then it will give little or no thrust -- in fact you'll just get lazy, smokey flames billowing out both the intake and exhaust.
This is because a ramjet relies on heating a fast-moving stream of cold air as it enters the engine and then expelling that air at a higher speed out the back. Unless the engine is moving rapidly through the air there's nothing for the burning fuel to heat.
- Fuel Consumption
As a general rule of thumb, the fuel-efficiency of an internal combustion engine is related to the compression ratio at which it operates. That is to say -- the more the air/fuel mixture is compressed before it is ignited then the more power you'll get from a given amount of fuel.
Diesel engines have a compression ratio of about 20:1, most car engines operate at compression ratios as high as 11:1, a pulsejet runs at a compression ratio of less than 2:1 and ramjets are about the same at low speeds. As a result, the ramjet (like the pulsejet) is not a particularly fuel-efficient engine. What makes it worse is that since the ramjet needs to be operated at very high speed, it's going to have to burn a lot of fuel just to overcome the drag it creats at that speed.
Thrust is a function of expanding gases due to heat. There is no pressure gain until combustion occurs. Venturii do not create pressure, they modify airflow charicteristics. Nozzle flow is a function of mass/volume flow rate between 2 points, with 1 area larger than the other. The idea of ram air is not applicable at the speeds a car can reach... and the ramjet engine isn't useful in any automotive application
We are not talking about "Ram Jets" we are talking about "ram air". I used the ram jet to show a practical application of air compression by movement of a properly configured pipe through the atmosphere.
The same principles of ram air
compression apply to ram air systems on automotive applications.
We are not talking about
venturi as I have already explained. So other than the speed issue, which is significant to a practical application, most of the technical info you posted is useful but unrelated to this discussion.
roadster with a stick
BTW we will soon be talking about the flow of air thru the CAI and the manifold. So, tell me what you know about the flow and properties of collodial gases throught a dynamic vacuum manifold vrs a dynamic pressure manifold. And please, don't give us crap about what the word vacuum means.