What is the Velocity of Air Entering the Air Filter?

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Discussion Overview

The discussion revolves around determining the velocity of air entering an engine air filter system, with a focus on the implications for vehicle performance and design. Participants explore theoretical and empirical aspects related to air flow, mass flow rates, and the impact of air intake design on engine efficiency.

Discussion Character

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

Main Points Raised

  • One participant proposes using the equation for velocity based on volumetric flow rate and area to determine the air velocity entering the filter, but expresses uncertainty about the relationship between this velocity and the vehicle's speed.
  • Another participant notes that vehicle design limits the intake of cold air and mentions that heat can negatively affect horsepower, suggesting that air velocity is dependent on vehicle speed and intake location.
  • A participant calculates a mass flow rate based on empirical data, converting it to SI units, and seeks confirmation on this interpretation.
  • There is clarification regarding the distinction between engine air filters and cabin air filters, with emphasis on the role of engine intake in determining air velocity.
  • One participant describes the flow of air through the system, indicating the sequence from the air filter to the mass airflow (MAF) sensor and then to the engine intake.

Areas of Agreement / Disagreement

Participants express various viewpoints on the relationship between air velocity, vehicle design, and performance. There is no consensus on the exact velocity calculations or the implications of air intake design, indicating ongoing debate and exploration of the topic.

Contextual Notes

Participants acknowledge the complexity of the problem, including factors such as empirical data, vehicle-specific designs, and the influence of air temperature on density. The discussion highlights the need for further analysis and clarification of assumptions regarding airflow dynamics.

emKhairol
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Hello guys,

I just came out with a new idea for my thesis project which is to improve the air filter system (drop-in type).

Currently I doing some basic analysis based on the current stock air filter before I proceed to my prototype air filter system.Says, I've been given an air filter which the area is 0.25m X 0.15m = 0.0375m^2.

I assumed the ρ of the air at average temperature (27.5 C ≈ 300 K) is about 1.161 kg/m^3.

We already know that, mass flow rate = (density)(volumetric flow rate) = (density)(area)(velocity)Based on the data given above, how can I determine the velocity of the air going inside the air box?
- there are several unknowns volumetric flow rate, mass flow rate

By using this equation, velocity = (volumetric flow rate) / (area) can I assume the velocity of the air is the same with the velocity of the car? (its seems like the velocity of the air (in m/s) too big.

Hope our engineers and pros may help me by solving this problem together. Thanks.***sorry for my bad language. I trying to make it clear for better understanding***
 
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without going into a lot of emperical data here are a few things to think about...
todays vehicle design limits where cold air can be piped into todays engine room. With this limiting factor we have to use the air channel as manufactured. Heat is the biggest robber of HP on the intake side. If memory serves me I think at wide open throttle we are moving 40 pounds of air per minute (500cfm). Dyno results tell us we will LOOSE horsepower if we remove the intake air filter...surprise..but true...

I'll post the reason after we all think about how this can be...

as far as air velocity..pretty much vehicle dependent relative to speed and location of the intake inlet...the hot setup is to locate it in hugh pressure area to improve performance...K&N air filter are the number one supplier in th espeed world and have done mucho research on this issue..hope it helps
 
Ranger Mike said:
without going into a lot of emperical data here are a few things to think about...
todays vehicle design limits where cold air can be piped into todays engine room. With this limiting factor we have to use the air channel as manufactured. Heat is the biggest robber of HP on the intake side. If memory serves me I think at wide open throttle we are moving 40 pounds of air per minute (500cfm). Dyno results tell us we will LOOSE horsepower if we remove the intake air filter...surprise..but true...

I'll post the reason after we all think about how this can be...

as far as air velocity..pretty much vehicle dependent relative to speed and location of the intake inlet...the hot setup is to locate it in hugh pressure area to improve performance...K&N air filter are the number one supplier in th espeed world and have done mucho research on this issue..hope it helps


Thanks for your detail explanation. From your words, you saying that the air moving at 40 pounds per minute, it means that was the mass flow rate isn't? So that, if convert to SI unit it will be 0.3023949 kg/s.

***correct me if I wrong*** :blushing:
 
emKhairol said:
Based on the data given above, how can I determine the velocity of the air going inside the air box?
The velocity and therefore mass flow rate are arbitrarily chosen based on the cooling requirements and therefore the size of the fan.
By using this equation, velocity = (volumetric flow rate) / (area) can I assume the velocity of the air is the same with the velocity of the car? (its seems like the velocity of the air (in m/s) too big.
No. The air circulated through the cabin is circulated by a fan.

[Edit] Er, wait -- I guess you are talking about the engine air filter, not the cabin air conditioning filter. In that case, the air velocity/volume is determined by the intake of the engine. Similar concept to a fan, though.
 
russ_watters said:
Er, wait -- I guess you are talking about the engine air filter, not the cabin air conditioning filter. In that case, the air velocity/volume is determined by the intake of the engine. Similar concept to a fan, though.

Thanks for your answer. And yes, I'm talking about the engine air filter (not the air-conditioning filter). :smile:

By the way, I'm counting the amount of air velocity/volume just before the air pass through the MAF sensor. In other word, the air flow into the filter. ***sorry for my bad language if you don't understand it***

The simplest way like this :

AIR (at state 1) --->>> AIR FILTER --->>> AIR (at state 2) --->>> MAF SENSOR --->>> AIR INTAKE
 

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