Estimate Air Density in ICE at Different Throttle Speeds

In summary, at high airflow speeds (Wide Open Throttle), pressure in the manifold should approximate atmospheric conditions. There is also less time for heat soak while the air travels to the cylinder. However, at lower air speeds (lower throttle), the density may be half of what it is at atmospheric conditions.
  • #1
TexanJohn
52
0
How would you estimate the charge density (air actually entering the cylinder) in an ICE? Assume the outside is standard pressure and temperature of 15*C (60* F) and 101.3kPa (14.7psi). At high airflow speeds (Wide Open Throttle), pressure in the manifold should approximate atmospheric conditions. There is also less time for heat soak while the air travels to the cylinder.

What about a lower throttle (air speeds)? Assume the manifold pressure is 50kPa, but we keep the temperature constant. Is the density really half of the atmospheric conditions (using 2.7 * P / T ; P in psi and T in *R)?
 
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  • #2
Anyone have a thought? :)
 
  • #3
Nobody. :frown:


Let me ask the question this way: :)

What if I had a long tube, and I was pushing/pulling air through this tube. Assume that there are signifcant temperature differences along the tube:

100* -20* 50*
---|---------------------|---------------------------|--------------

-> -> -> Airflow -> -> ->

---|---------------------|---------------------------|--------------


If I could "capture" part of the air at the temperature points above, is the density different at each point? Assume that a fan is pushing air through the tube at a rate of 200cfm and the air entering is 60*F and 101.3kPa.
 
  • #4
TexanJohn said:
How would you estimate the charge density (air actually entering the cylinder) in an ICE?

What is ICE?
 
  • #5
zoki85 said:
What is ICE?

Internal Combustion Engine


Is that why no one has responded? Where have all the IC engine gurus gone? :)


Just curious about thoughts on the effects of heat and pressure relating to airflow into an engine. Since the engine is not static nor a 'closed system'(I am sure that I am not using that term correctly. e.g. like a balloon filled with air; heat it, it expands, same mass but now more volume, thus less dense), I was curious about the effects of heat (and pressure) on the air entering the engine. The intake manifold, intake ports, etc. can't expand like the balloon, but the air can flow backwards through the system. i.e. back out through the TB the wrong direction. As air enters the engine and is heated, does the air 'expand', does this alter (slow) the airflow rate, etc.
 
  • #6
Yes, as the air picks up heat during the induction process, it expands, and you get less charge into the cylinders. This is exactly why air inlets on performance cars are sited to ensure the source is as cold as possible, why intercoolers work so well, and why your car seems to have better performance on a cold day.

I'd not done any replying cos I've just bought a house and been moving in!
 

What is the purpose of estimating air density in ICE at different throttle speeds?

The purpose of estimating air density in ICE (internal combustion engines) at different throttle speeds is to understand the effects of air density on the performance and efficiency of the engine. Air density plays a crucial role in the combustion process and can greatly impact the power output, fuel consumption, and emissions of an engine.

How is air density in ICE typically estimated?

Air density in ICE is typically estimated using the ideal gas law, which states that the density of a gas is directly proportional to its pressure and inversely proportional to its temperature. This can be determined using sensors that measure the pressure and temperature of the air entering the engine.

What are the factors that affect air density in ICE?

The factors that affect air density in ICE include altitude, temperature, and humidity. As altitude increases, air density decreases, which can affect engine performance. Higher temperatures and humidity levels can also decrease air density, resulting in a decrease in engine power and efficiency.

Why is it important to consider air density at different throttle speeds?

Air density can vary at different throttle speeds due to changes in engine load and air intake. It is important to consider these variations because they can affect the air-fuel ratio and combustion process, ultimately impacting the engine's performance and emissions. Additionally, understanding the air density at different throttle speeds can help in optimizing engine tuning and fuel economy.

How can knowing air density at different throttle speeds benefit engine development and design?

Knowing air density at different throttle speeds can benefit engine development and design by providing valuable data for improving engine performance and efficiency. This information can be used to optimize various engine components, such as the air intake system and fuel injection, to achieve maximum performance and reduce emissions. It can also aid in the development of more accurate engine simulation models for future designs.

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