Is Using an Oxygen Rotameter for Propane Flow Measurement Accurate?

[Ali Durrani]

Hello Dear friends

i was doing tests to evaluate the performance of my Engine Test bench, (197/225cc engine 12.6kW IC SI engine, Propane) For mass flow rate i have used a rota meter to find the Volume flow rate and convert it to mass flow rate, i couldn't find a rotameter for propane so i decided to go for oxygen rotameter

now that i have got the values they are 4, 4.5, 4.8, 5 lit/min
as they are the indicated flow rates

for correction i have used these equations

Cdensity=(density of oxygen/density of propane)^1/2
Cpressure= (p+0.1013/ps+0.1013)^1/2
p=actual operating pressure
ps=standard or designed pressure for rotameter use
Ctemperature=(ts+273/t+273)^1/2
ts=standard temperature for rotameter use
t=actual operating temperature

Gas Correction factor(GCF)=Cdensity*Cpressure*Ctemperature
Actual Flow = Indicated Flow rate * GSF
the density of propane is 1.873g/lit
operating temperature was recorded as 10C
operating pressure was 0.005MPa
standard values for rotameter are 1.292g/lit, 20C, 0.343MPa

so the actual flow values are 1.688, 1.899, 2.0265, 2.111 lit/min

i just wanted to ask that is it correct method or am i missing something because when i evaluate the thermal efficiency of my test bench it gives me above 60% which is no way possible

 

[Achy47]

Dear friend,

Thank you for sharing your test results and methods with us. I am a scientist with expertise in engine testing and performance evaluation, and I would like to offer some insights on your approach.

Firstly, using a rotameter designed for oxygen to measure propane flow is not an accurate method. Propane and oxygen have different densities and properties, which can affect the accuracy of the readings. I would recommend using a rotameter specifically designed for propane, or using a different method such as a mass flow meter.

Additionally, your calculations for the gas correction factor seem to be missing a step. The correction factor should also take into account the difference in specific heat ratio between propane and oxygen. This can significantly affect the accuracy of your results.

Furthermore, it is important to ensure that all your measurements are taken at the same conditions, including temperature, pressure, and humidity. Any variations in these parameters can also affect the accuracy of your results.

I would suggest re-evaluating your methods and using a more accurate measurement technique to obtain reliable results. It is also important to consider other factors that may affect the thermal efficiency of your test bench, such as engine design, fuel quality, and operating conditions.

I hope this helps and wish you all the best in your research.