- #1
storken
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So, I've been thinking a lot on this lately. I want to use two turbochargers, one with just the compressor - and one with both compressor and turbine.
Doing calculations at 10 deg C. Doing the math for Norway because commercially avatible evap heat exchangers doesn't really work well in our climate.
This is how it is going to work.
A 2,5kW electric motor (90% efficient, controller losses included) drives the first compressor (comp1), delivering ~2 bar (a little over 2:1 pressure ratio) at 80% efficiency. Temperature within the air reaches 430 deg C. (((283*2)/0.8)-273)
Between the first compressor and the second, there will be a need for a heat exchanger. Calculating 80% efficiency, new temperature out is 85 deg C. The reason for this is that alu (responsible for most of the parts in the compressor) melts at 660 degC, something that would easily be achieved.
Pressure drop after intercooler? No, p will remain constant - only T changes.
The second compressor(comp2) (80% efficient) further compresses the mixture to 3-3.5 bar. This is driven by its own turbine. Air temperature out from compressor is 500 degC. ((((273+85)*1.75)/0.8)-273)
This turbine regenerates (65% efficient) the energy lost from the first compression. After this the air exits. Very low temperature might be a concern here - don't want things to freeze up lol :P (getting to this at the end).
This is the complete loop:
Free air 10C -> compressor1 -> 430C, 2Atm -> Heat ex1 -> 85C, 2Atm -> compressor 2 -> 500C, 3.5Atm -> Heat ex2 -> 100C, 3.5Atm -> Turbine -> 133K, -140C (!), 1Atm
I want to build this some time in the next year. I've been looking at popular turbos and have more than one concern. Here is some.
1. Driving the first compressor at ~90k rpm. Bigger spinners require less rpm, but more power. Also - side loads if I want to use a gear ratio might lead to upgrades in the bearings.
2. How to calculate total efficiency? 400% achievable? If I have mass flow, this should be ok - rigth? I'm a bit lost in energy in gas at temps - been a while since i worked with physics xD
Just throwing it out here for constructive critisicm :)
Doing calculations at 10 deg C. Doing the math for Norway because commercially avatible evap heat exchangers doesn't really work well in our climate.
This is how it is going to work.
A 2,5kW electric motor (90% efficient, controller losses included) drives the first compressor (comp1), delivering ~2 bar (a little over 2:1 pressure ratio) at 80% efficiency. Temperature within the air reaches 430 deg C. (((283*2)/0.8)-273)
Between the first compressor and the second, there will be a need for a heat exchanger. Calculating 80% efficiency, new temperature out is 85 deg C. The reason for this is that alu (responsible for most of the parts in the compressor) melts at 660 degC, something that would easily be achieved.
Pressure drop after intercooler? No, p will remain constant - only T changes.
The second compressor(comp2) (80% efficient) further compresses the mixture to 3-3.5 bar. This is driven by its own turbine. Air temperature out from compressor is 500 degC. ((((273+85)*1.75)/0.8)-273)
This turbine regenerates (65% efficient) the energy lost from the first compression. After this the air exits. Very low temperature might be a concern here - don't want things to freeze up lol :P (getting to this at the end).
This is the complete loop:
Free air 10C -> compressor1 -> 430C, 2Atm -> Heat ex1 -> 85C, 2Atm -> compressor 2 -> 500C, 3.5Atm -> Heat ex2 -> 100C, 3.5Atm -> Turbine -> 133K, -140C (!), 1Atm
I want to build this some time in the next year. I've been looking at popular turbos and have more than one concern. Here is some.
1. Driving the first compressor at ~90k rpm. Bigger spinners require less rpm, but more power. Also - side loads if I want to use a gear ratio might lead to upgrades in the bearings.
2. How to calculate total efficiency? 400% achievable? If I have mass flow, this should be ok - rigth? I'm a bit lost in energy in gas at temps - been a while since i worked with physics xD
Just throwing it out here for constructive critisicm :)