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If it helps, think of it this way. Start with a 1-m^3 accumulator at 101 kPa, 20C, and a rack of high-pressure bottles at 13786 kPa, 20C. Imagine a frictionless piston at one end of the accumulator. Now admit gas from the bottle rack on one side of the piston. The piston moves, compressing...

3D Dave said: >That's why I suspect the compression of gas into the chamber just before firing has significantly heated that gas, which allows it to sustain a sonic flow higher than in the air outside the gun. rb1957 said: >compressing gas heats it ... expanding gas cools it, no? > >so the tank...

> A convergent divergent nozzle is needed to achieve hypersonic fluid flow. I do not know who came up with that idea but every liquid fueled rocket has that. They are sometimes called de Laval nozzles: https://en.wikipedia.org/wiki/De_Laval_nozzle > So I see that the first place for the flow...

You've probably seen this by now, but just in case, last fall Destin Sandlin uploaded a video about a pneumatic baseball cannon he and some friends built that can launch baseballs at well over 1,000 MPH. There's a 23-minute video in which they describe the design, constructions, and early tests...

AIUI, when operating a critical flow venturi (CFV) the goal is to maintain an outlet/inlet pressure ratio sufficiently low to achieve sonic flow at the throat and a normal shock wave somewhere in the downstream section. The pressure ratio should be low enough to keep that normal shock some...

The whole thing is weird, I know. The end goal is to be able to estimate cylinder air mass at any speed/load point in the operating map. The problem is that the data I have available right now is limited. I have intake MAP for the entire operating map, but I don't have exhaust MAP data, so I...

You're quite right. I expressed myself poorly. I'm actually calculating it exactly the way you describe; I just wanted to differentiate this definition from the other definition, which always uses STP density instead of intake manifold density (which may be quite a bit higher due to boost)...

I think it's been adequately pointed out that the geometry (surface-area-to-volume-ratios and such) makes it unlikely that any tiny pockets of air trapped in the injector could ever get hot enough to ignite the fuel they come into contact with. But what if they magically did manage to light...

I'm trying to develop a coarse model of volumetric efficiency (VE) as a function of intake manifold pressure for a heavy-duty diesel engine (~15L). For this discussion, I'm defining VE as the in-cylinder density at intake-valve closure divided by the density in the intake manifold. I have...

I have a Meriam laminar flow element. To use it, you measure the pressure differential across the element, as well as the humidity, temperature and absolute pressure upstream of the element. Then some math happens, and you end up with a flow rate. You can make all of those measurements with...

>when torque required to rotate the compressor stages >exceed torque produced by the power stage you will >stall. when the air velocity in the burner can not >support combustion, you'll have flame out Makes sense in a "logic" kind of way. Presumably stable operation for a given fuel rate...

Gas turbine engines have maximum speed and power limits based on pressures, temperatures and mechanical loads on the parts spinning at ludicrous speed. So...what parameters determine the MINImum RPM for a gas turbine? When that 747 is waiting for takeoff, all four engines are "idling," putting...

The root of my mental struggle is understanding the sources and sinks for the energies involved. Suppose we create a 1 cubic-meter bubble of hydrogen at sea level. In pushing back (lifting up) the atmosphere to make room for this bubble of hydrogen, we have done 101.325 KJ of work. If we...

> don't understand why you are bringing work into the picture. See paragraph 2 in my OP: the purpose of the original discussion was to identify how much mechanical work could be extracted from a buoyant balloon rising from sea level to an arbitrary altitude.

Greetings - My background: I have a Ph.D. in mechanical engineering, so I'm well-versed in fluid mechanics, thermodynamics, and all that jazz. I was recently involved in an online discussion regarding the extraction of mechanical work from the buoyancy of a hydrogen balloon. I took a stab...