a design question.

[Wyatt Hatch]

i am brand new to all of this, so feel free to blow me off. i was looking around this website and became very interested in these jets. i was interested in the "Thunderchine", and i think it is a very great design(for what that's worth coming from me) and i wondered if it would work with four intakes instead of just two, and if it would improve or hurt performance. i originally just thought it would look cool, but looking around i saw pj's with four intakes. just a thought, thanks for any answers.

[metiz]

i am brand new to all of this, so feel free to blow me off. i was looking around this website and became very interested in these jets. i was interested in the "Thunderchine", and i think it is a very great design(for what that's worth coming from me) and i wondered if it would work with four intakes instead of just two, and if it would improve or hurt performance. i originally just thought it would look cool, but looking around i saw pj's with four intakes. just a thought, thanks for any answers.

Haha I know someone that's reading this who's grinding his teeth right now
But no. You can't just slap on 2 more intakes. It won't "hurt performance", It'll stop it from running.

[Wyatt Hatch]

oh, sorry. just a thought.

[hinote]

You can't just slap on 2 more intakes. It won't "hurt performance", It'll stop it from running.

I agree, but just for grins (and to edumucate our newbie friend), WHY??

Bill

[ace_fedde]

The grins?
Because somebody else has an idea to do so , but he is not just going to slap on two more intakes.

Fedde

[hinote]

The grins?
Because somebody else has an idea to do so , but he is not just going to slap on two more intakes.

Fedde

Again--you're right.

All I'm asking for is a discussion of the WHY's on this subject. Reason is, there hasn't been a lot of education about PJ design recently and I think this website deserves some educational posts.

Bill

[Jutte]

Hi Hinote,
Because the Intake to tail pipe ratio's would be effectively changed if you just
slapped two extra intakes on it.....?
Ummm ... the angle of the fangle dangle would be twice that of the aspect
of the thrunge guster ratio...?
OK ... I am just guessing now....LOL!

[hinote]

Hi Hinote,
Because the Intake to tail pipe ratio's would be effectively changed if you just
slapped two extra intakes on it.....?
Ummm ... the angle of the fangle dangle would be twice that of the aspect
of the thrunge guster ratio...?
OK ... I am just guessing now....LOL!

Thanks for your amusing post here. But..............

Based on existing successful designs there are several very important parameters to consider in the correct dimensioning of the intake. I'm not prepared to be an expert here, but I believe this one may be the most obvious:

The intake(s) diameter must be proportioned to maintain a very high velocity in both the inflow and outflow directions, for different reasons. During the outflow the high velocity aids in evacuation of the combustion chamber to a value below atmospheric; it also maximizes the thrust the intake is capable of contributing to the overall power of the engine. OTOH during the inflow portion of the cycle the velocity should be as high as possible to support the maximum duration of the (relatively) cold airflow into the front of the CC to create the plugging effect there, and the opaque front which the returning hot gas mass and its associated higher pressure wave (from the rear) will meet to begin the next combustion cycle.

In any case the max velocity must be limited in either direction to below supersonic velocities to prevent the deterioration this effect produces. In many cases this compromises one of the flow regimes (either "in" or "out") but must be accepted as a part of the design compromise.

In simpler terms--adding additional intakes would imply reductions in the design velocities of the inflow/outflow in the intake tubes, and result in substantially reduced performance.

I can do several more of these--but I think this one may be the most important parameter. Hope this helps.

Bill

P.S.: I invite more refined and/or different versions of the description above. I hope and believe the basic statements made are correct, based on my successes in designing and building my own designs and those of others.

[Jutte]

Hi Hinote,
Sorry to be a bit of a prat but I have a question in regards to what you said ....
"In simpler terms--adding additional intakes would imply reductions in the design velocities of the inflow/outflow in the intake tubes, and result in substantially reduced performance."
My question is ...Would the inflow/out flow velocities of the overall intakes be maintained if all of the intakes ( ie: additional Intakes ) diameters were reduced? (Of course boundary layer drag would eventually put a choke on things).
Thanks...