Flow Rate of Air??

<...hi,wat is the flow rate of air required for 50cc engine at inlet side,it may be petrol or diesel engine....>

What rating of engine? Which fuel? It can be estimated backwards, roughly, from the nominal power ouput figure and the chemistry of the selected fuel once this data is available.

http://www.simetric.co.uk/si_cc2hp.htm

<...how to find velocity....>

It is the volumetric flowrate, estimated above, divided by the cross-sectional area of the inlet duct.

You've stated the engine capacity. All you need is the rpm and whether it's 2 or 4-stroke and you can easily work out the air flow

Codey

Indeed. That method would be simpler than that in reply no.1.

Flow rate = 50 cc's per revolution. Pressure between 8 and 10 atmospheres.

Unless it has a blower on the inlet...the inlet pressure is hardly going to exceed 1bar.
Or is it a ram jet?

OK, Ok. You forced me to try to figure out some missing puzzle pieces. How many strokes is the engine? Where and when are you measuring the pressures? Is the engine diesel or does it have a spark? Is the chamber hemispherically shaped? Is it intake normally aspired or supercharged?

For four-stroke, spark, on compression stroke, inside the cylinder chamber, typically 8 to 10 atmospheres?

Yes, outside the intake, non-supercharged, compression stroke, one atmosphere.

For two stroke, expect different values. I need a rest. Get us more information!

Hello Eriew

Not sure where you get the 8 - 10 atmospheres from. The compression ratio might be 8 - 10, but this is a misnomer, ratio is actually volume of cylinder to volume of combustion chamber. Compression approaches adiabatic so pressure ratio is higher and temperature also rises.

But this doesn't affect the air flow, which is usually wanted at intake conditions of P and T (often close to standard conds anyway).

Flow (cc/min) = engine cc x RPM for a 2-stroke, or engine cc x RPM/2 for a 4-stroke. But for petrol engine this only applies when the throttle is wide open, and even then, and with diesel, there is some pressure drop so pressure in cylinder at end of induction is below atmospheric and flow (at atmospheric or std conditions) a bit lower.

Cheers......Codey

Yes, I was referring to the compression ratio as a "rough" measure of cylinder pressure using atmospheres to avoid unit conversion issues. At 9 to 1 and 14.7 psi (atmosphere), pressure would be 132 psi on the compression stroke in the chamber (assume 4 stroke).

I understand your points regarding volumes. Given is the volume of the cylinder as 50cc's. Unknown (to us and possibly the OP) is the volume of the combustion chamber. There is no point in going into the laws of thermodynamics yet. OP's homework has already been handed in and I have to get back to work.

BTW, compression can be measured and used as approximate pressure. Assuming the cylinder was "good", I wager the the result would be somewhere in this range (132 psi + or -). Such a reading would be actual. But as you point out, this may differ from theoretical values for the reasons you state.

So the key word here is "rough". Until we learn a bit more about this cylinder, I think "rough" is the best we can do.

Do you design new engine?

Please mention that there is a air filter at inlet side of engine. You can refer to egine of Honda or Suzuki or Yamaha motorcycle for your need.

Good luck.

unassembly the honda, yamaha...engine to find the filter

Do not must to disassembly those egines, just go out the motorbike maintenance shop or market and buy the filter and you can know what the size of inlert of engine.

spend money to buy the filter for checking the size of the inlet???? do you have another idea???

Sorry, it is a my mistake. I just think you need it, if your purpose is reference only you can see and look donot need to buy filter. My suggestion is real and fast, b/c of It was perfect designed by exellence team e.g. Hondad, Suzuki,... and it was well operated .... So you can use it when nercessary and donot lose your time for redesigning. Do you agree with me?

you are out of the track. keep to be on the right track to discuss with us

you are out of the track. keep to be on the right track to discuss with us

your perfomance is an immitation