Temperature and mass flow rate of ICE exhaust gas

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Discussion Overview

The discussion revolves around the mass flow rates and temperatures of exhaust gases from light gasoline internal combustion engines, particularly in the context of analyzing waste heat recovery. Participants seek actual values and explore various factors influencing these parameters.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants mention that engineering thermodynamics textbooks, such as Çengel's, may provide useful examples and values related to internal combustion engines.
  • One participant emphasizes the need for actual values of mass flow rates and exhaust gas temperatures for studying waste heat recovery, noting that modern car engines typically have around 30% thermal efficiency.
  • Another participant states that exhaust temperatures can exceed 800°C during peak operation but generally range from 250-500°C during normal operation.
  • There is a mention of a rule of thumb regarding heat dissipation, suggesting that about one-third of the heat is lost through the radiator and another third through the exhaust.
  • One participant proposes that the mass flow rate of exhaust gases could be calculated using the mass air flow rate plus the weight of the fuel, factoring in volumetric efficiency and air/fuel ratio.
  • Another participant highlights the importance of specific heat of exhaust gases, noting that it may vary significantly at high temperatures and pressures compared to standard conditions.

Areas of Agreement / Disagreement

Participants express varying views on how to obtain the necessary values and calculations related to exhaust gases, with no consensus reached on specific figures or methods. Multiple competing approaches and models are presented.

Contextual Notes

Participants note the dependence on various assumptions, such as the specific heat of exhaust gases at different conditions and the efficiency of engines, which may affect the calculations and results discussed.

y2j
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Hi everyone
I searched about the mass flow rates and temperatures of exhaust gases of light gasoline internal combustion engine at different condition but I don't fond anything yet .
Anyone can guide me?
.
 
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Most engineering thermodynamics textbooks include chapters on internal combustion engines, you can get an idea on the values you need by looking at the examples provided in the books.

Check out Çengel's Engineering Thermodynamics.
 
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I need to actual values of mass flow rates and temperatures of exhaust gases of light gasoline internal combustion engine for analysis and studying effect of waste heat recovery
 
y2j said:
I need to actual values of mass flow rates and temperatures of exhaust gases of light gasoline internal combustion engine for analysis and studying effect of waste heat recovery

Modern road car engines can manage around 30% thermal efficiency, meaning that 70% of the heat energy generated by the engine is lost to the atmosphere. This heat energy is dissipated through the exhaust AND cooling system. While i can't give you figures on mass flow rates, exhaust gas is approximately 2/3 less dense than the intake. Exhaust temps can reach above 800C during peak operation, but can range from 250-500C during normal operation.

As a side note, the latest F1 engines(1.6L Turbo) manage a thermal efficiency of 45-50%

Hope this info helps
J Mc
 
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J Mc said:
Modern road car engines can manage around 30% thermal efficiency, meaning that 70% of the heat energy generated by the engine is lost to the atmosphere. This heat energy is dissipated through the exhaust AND cooling system. While i can't give you figures on mass flow rates, exhaust gas is approximately 2/3 less dense than the intake. Exhaust temps can reach above 800C during peak operation, but can range from 250-500C during normal operation.

As a side note, the latest F1 engines(1.6L Turbo) manage a thermal efficiency of 45-50%

Hope this info helps
J Mc
Thank you so much
 
Generally, the rule of thumb is a third of the heat is dissipated at the radiator and a third goes out the tailpipe.

How good are you at chemistry? It isn't all that hard to use the equation of combustion to calculate the mass flow rate.
 
that required the temperature of gases also and mole fraction of component
 
Wouldn't the mass flow rate going out be the same as the mass air flow rate going in plus the weight of the fuel? If you know the volumetric efficiency (VE) of the engine at a given RPM and the air/fuel ratio you should be able to get the mass flow rate from that. I think most stock engines operate in the 70-85% VE, while highly tuned engines (F1, Nascar, etc) can get significantly over 100% where the engine makes peak torque. And that's without a turbocharger.. Turbocharged engines (especially race diesels) can reach over 1000% VE.. Compounded turbos can provide boost pressures of 200PSI.
 
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Right, it doesn't depend on temperature: what goes in must come out. If you know the fuel flow rate and the chemistry (or there is some back-way of doing a fuel/air mixture), that's all you need.
 
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I think the trickiest thing is to get the specific heat of the exhaust gas.. at high temperatures and pressures it may be significantly different from STP, and that is going to be a key part of the equation of how much heat you can extract.
 

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