Amount of fuel required for combustion in one engine cycle

Automotive engineering

・Running resistance

・Vehicle acceleration

・Alternator

・Fuel injection amount

・IMEP vs BMEP

・MY, CY, FY

・Turning Radius

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・Engine vs vehicle speed

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Release date:2023/4/21　　　　　　　　　

　・In Japanese

■Amount of fuel required for combustion in one engine cycle

The calculation method is explained below.

＜Prior knowledge＞
Below is some knowledge of chemistry.

・ 1L = 1000cc
・ 1ml = 1cc = 1cm³
・ percentage of oxygen in the air：about 20%
・ oxygen mass：32g in 22.4L
・ gasoline density：0.73g/cm³

＜prerequisite＞

・ Engine displacement：2000cc =2000ml

・ Number of engine cylinders：4 cylinders

・ Atmospheric conditions：standard atmosphere

・ Charging efficiency：0.3 (when idling)

・ Air-fuel ratio：14.7 (mass ratio)

＜Method of calculation＞

・ Displacement of 1 cylinder = 2000/4 = 500 ml

・ Amount of air in the cylinder = 500 * 0.3 = 150 ml　※ Charging efficiency=0.3

・ Amount of oxygen in the cylinder = 150 * 0.2 = 31.5 ml　※ Oxygen percentage=0.2

・ Oxygen mass in cylinder = 32(g)*31.5/(22.4*1000) = 0.045 g

・ Required fuel mass = 0.0429 / 14.7 = 0.00306 g

・ Required fuel volume = 0.00306/0.73 = 0.00419 cm³ = ml

＜Generalization＞
The generalized formula is

■How long does it take to empty a full fuel tank.
In the above, we calculated the injection amount per cylinder, but this time we need to consider the injection amount for 4 cylinders.

＜prerequisite＞
・ Tank capacity：50L
・ Engine speed：800rpm (when idling)

＜Method of calculation＞
・ Number of injections per minute=800*2 =1600回 (2 combustions per engine revolution)

・ Fuel injection amount for 1 minute=1600 * 0.00419(ml)=6.704ml

・ Time to consume 50L=50/0.006704=7458.23 minutes=124.3 hours=5.19 days

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