Engine exhaust back pressure calculation

[Mechh007]

To find out engine exhaust back pressure we are using the following formula:
P= (L X S x Q^2 X 3.6 X 10^6) / (d^5) + Muffler resistance

P = Back pressure in KPa.
L= Length of pipe in Meter.
Q = Exhaust gas flow in Kg/m3
S = Density of gas Kg/m3.
D = Inside diameter of pipe in mm.
T = Exhaust Temperature ºC
Ps = Muffler resistance KPa.

In the above formula we coould not find elevation. Can we calculate back pressure without considering elevation ? Please clarify.

 

[BigInch]

The equation probably assumes that the exhaust pipe is horizontal, or of a height short enough such that consideration of any elevation change between inlet and outlet is not necessary. Not unreasonable for short stacks and hot=> low density gases.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[Mechh007]

L= Length of pipe in Meter. - 65 m
Q = Exhaust gas flow in Kg/m3 - 340.2 kg/m3
S = Density of gas Kg/m3- 0.51kg/m3
D = Inside diameter of pipe in mm-381 mm
T = Exhaust Temperature ºC - 425ºC
Ps = Muffler resistance KPa. - 2.5 KPa

Exhaust elevation is approx. 15m.
No. of 45º elbow - 4 Nos.
No. of 90º elbow - 4 Nos.
for this scenario do we need to consider elevation?

 

[Latexman]

15 m elevation of a 0.51 kg/m3 gas is only 0.075 KPa. What % is that of the frictional pressure drop?

Good luck,
Latexman

 

[Mechh007]

Do we need frictional pressure drop?

 

[Mechh007]

In existing projects we placed the muffler in horizontal position. But now we need to place the muffler in verticle postion. If we place the muffler in vertical postion, will it make any changes in back pressure? Please advice.

 

[BigInch]

I would not consider the pressure differential due to a 15 m elevation.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[MikeHalloran]

If the muffler fills with rainwater, it may affect the backpressure.


Mike Halloran
Pembroke Pines, FL, USA

 

[BigInch]

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[Latexman]

Needs a flapper valve at the top.

Good luck,
Latexman

 

[BigInch]

rain hat ^

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek