Diesel injector sac pressure calculation

In summary, make sure to apply the discharge coefficient to the flow rate in the equation and you should get the correct answer.
  • #1
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I am trying to calculate the nozzle sac pressure required to deliver 60mm3/ms of diesel fuel into a pressurised cylinder (19MPa). The nozzle has 5 delivery holes of diameter 0.157mm and the discharge co-efficient is 0.87.
The sac diameter= 0.7 mm and the sac volume= 0.12mm3. I have tried to use the equation below:
Q=Cd x sqrt(2deltaP/rho) x A2/sqrt(1-(A2/A1)^2) ,
solving for delta P where p2 = 19MPa. p1= unknown (wanted item)
A2 = Sum of the 5 hole areas
A1=Sac area
rho= density of diesel

However I am getting incorrect answers, is there something I am missing or doing incorrecty?
Please let me know!
 
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  • #2
You are missing the fact that the discharge coefficient is applied to the flow rate. The equation you have should beQ = Cd*sqrt(2*ΔP/ρ)*A2/sqrt(1 - (A2/A1)^2)whereCd = discharge coefficientΔP = ΔP (19MPa)ρ = density of dieselA2 = sum of the 5 hole areasA1 = Sac areaSo, if you know the values for all the variables, you can solve for the sac pressure required to deliver the desired flow rate.
 

1. How is diesel injector sac pressure calculated?

Diesel injector sac pressure is calculated using the formula: Pressure = Force / Area. The force is determined by the weight of the fuel in the injector sac and the area is the cross-sectional area of the sac. This calculation is important in determining the fuel delivery rate of the injector and ensuring efficient combustion.

2. What factors affect diesel injector sac pressure?

The main factors that affect diesel injector sac pressure are the fuel density, the size of the injector sac, and the injection timing. The density of the fuel affects the weight of the fuel in the sac, while the size of the sac determines the volume of fuel that can be held. Injection timing also plays a role in determining the pressure as it affects the duration of fuel delivery.

3. Why is it important to calculate diesel injector sac pressure?

Calculating diesel injector sac pressure is important because it helps to ensure the proper functioning of the fuel injection system. If the pressure is too low, it can result in incomplete combustion and reduced engine performance. On the other hand, if the pressure is too high, it can cause damage to the injector and other engine components.

4. How is diesel injector sac pressure measured?

Diesel injector sac pressure can be measured using specialized equipment such as a pressure gauge or a pressure transducer. The injector is removed from the engine and connected to the measuring device. The engine is then cranked or run, and the pressure readings are recorded.

5. Can diesel injector sac pressure be adjusted?

Yes, diesel injector sac pressure can be adjusted by changing the size of the injector sac or by adjusting the injection timing. However, it is important to note that these adjustments should only be made by trained professionals using proper equipment to ensure the optimal performance of the engine.

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