The Squeeze

[MolaKule]

In a conventional IC engine during the intake stroke, the intake valve opens up, the fuel is injected, and turbulance enhances mixing.

When the valve closes and the piston moves up for compression,

the _____ _____ _____ of the hydrocarbon molecules decrease.


Fill in the three words.


Guidelines for the Question of the Day:

1. No Piston Cup Lapel Pin will be awarded to the same person within 14 days of a previous award.

2. Please respond with a complete sentence or explanation.

3. Please do not post links. If a question arises as to the need for clarification, then sources and links may be requested.

4. Please, no off topic posts.

 

[Shannow]

Apparent Activation Energy

 

[Olas]

Density per volume

 

[berniedd]

Distances between Atoms

Piston moves up, causes density of the air-fuel charge to INCREASE. Volume of the charge decreases = less spaces between the individual molecules of the whole AF mix.

 

[Sunnyinhollister]

Mean Free Path

 

[A_Harman]

Originally Posted By: Sunnyinhollister
Mean Free Path


ditto.

 

[CourierDriver]

All I know is, the engine is running and I get to point B.

 

[Olas]

Originally Posted By: Olas
Density per volume


Pre-coffee posting

Should have read sparsity.

 

[MolaKule]

The definition of the Mean Free Path (MFP) of a set of molecules is, that if a molecule is assumed to be a particle of diameter d, the distance between collisions of those molecules will be proportional to T/(Pi*d^2*P), where P is the pressure in the cylinder, and T is the temperature of the gas.

P in the cylinder is quickly increasing over time, since the volume is decreasing. T is increasing as well, but the pressure P is increasing faster than Temp.

Since P is increasing quickly over time, and since P is in the denominator, this means that the MFP is decreasing. The time between collisions will also decrease.

Once ignition occurs, the Temperature starts increasing rapidly at maximum pressure (since the pressure can't increase any further), and Temperature starts to overtake the equation. When this happens, the MFP has to increase, which results in more force on the piston, forcing it down to produce mechanical ppower.


So Mr. Harman of Motown fame takes home the priceless 3-D Piston Cup Lapel Pin.

 

[MolaKule]

While A. Harmon also had the correct answer, Sunnyinhollister had the first correct answer so the
3-D Piston Cup Lapel Pin goes to him.

Sorry A. Harman, maybe next time.

 

[Sunnyinhollister]

Woo Hoo!!!

All those years of working on high vacuum systems finally paid off!!