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Study on seal performance of injector nozzle in high-pressure common rail injection system

Review
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Abstract

The injector needle valve assembly is a key component of the high-pressure common rail fuel injection system of a diesel engine. The sealing performance of the valve assembly significantly affects the normal operation of the engine, the emissions of which can be typically reduced by increasing the pressure of the fuel injection through the valve. However, increased injection pressure causes deformation of the gap of the needle valve assembly; this affects both the leakage from the needle valve assembly and the normal operation of the diesel engine. Herein, to study the effect of fuel pressure on the needle valve assembly leakage, fluid lubrication and tribology principles were used to analyze the sealing mechanism of the valve assembly in the present study. The film thickness and leakage were then simulated using different fuel pressures. In addition, an experiment was performed to verify the results of the theoretical analysis and simulation. It was found that the leakage rate through the needle valve assembly gradually increased with increasing fuel pressure, although the experimentally determined rates under low-pressure conditions were lower than those determined by theoretical analysis and simulation. The results of this study provide a basis for improving the sealing performance and structural optimization of needle valve assemblies.

Keywords

Needle valve assembly Sealing performance Theoretical analysis Two-way coupling Experimental verification 

List of symbols

U

Relative velocity between valve body and needle

Q

Needle valve assembly leakage

d

Diameter of sealing section of needle

ΔP

Pressure difference between inlet and outlet

L

Sealing plate length

μ

Dynamic viscosity of fuel

δ

Distance between plates (gap width)

C

Correction coefficient of laminar initial segment

e(x)

Eccentric magnitude of x section

ε

Needle eccentricity

F

Applied force on the upper surface

P

Fuel pressure

m

Mass of needle

a

Acceleration of needle

v

Velocity of needle

tn

Time required for the needle closing process

T0

Tightening torque of the nut

T1

Thread friction torque

Tf

Friction torque between the nut and valve body shoulder

F1

Applied force on the valve body shoulder

ρv

Equivalent friction angle of the nut

f

Friction coefficient of the thread

Ψ

Helix angle

β

Thread angle

Rf

Friction radius between the nut and valve body shoulder

fc

Friction coefficient between the nut and valve body shoulder

d

Pitch diameter of thread

Qs

Total leakage from control piston-cylinder assembly and needle valve assembly

qs

Total leakage rate from control piston-cylinder assembly and needle valve assembly

Qs1

Static leakage from control piston-cylinder assembly

qs1

Static leakage rate from control piston-cylinder assembly

Qs2

Static leakage from needle valve assembly

qs2

Static leakage rate from needle valve assembly

λ1/λ2

Proportional coefficient

d1

Diameter of control piston guidance sections

d2

Diameter of needle guidance sections

δ1

Mean gaps of control piston-cylinder assembly

δ2

Mean gaps of needle valve assembly

l1

Length of control piston-cylinder assembly film seals

l2

Length of needle valve assembly film seals

Qd

Total dynamic leakage from control piston-cylinder assembly and needle valve assembly

qd

Total dynamic leakage rate from control piston-cylinder assembly and needle valve assembly

Qd1

Dynamic leakage from control piston-cylinder assembly

Qd2

Dynamic leakage from needle valve assembly

qd2

Dynamic leakage rate from needle valve assembly

References

  1. 1.
    Prinz Katharina, Kemmetmüller Wolfgang, Kugi Andreas (2015) Mathematical modelling of a diesel common-rail system. Math Comput Model Dyn Syst 4(21):311–335CrossRefMATHGoogle Scholar
  2. 2.
    Knecht Walter (2004) Some historical steps in the development of the common rail injection system. Trans Newcomen Soc 74:89–107CrossRefGoogle Scholar
  3. 3.
    Jiping Lu, Tang Shuiyuan, Zhou Yong, Hong Jing, Jian Zhonghua (2011) Simulation of assembly tolerance and characteristics of high pressure common rail injector. Int J Comput Intell Syst 4:1282–1289CrossRefGoogle Scholar
  4. 4.
    Long RH, Wang SL (2015) Investigation on the surface quality of the needle in the nozzle injector. Mach Des Manuf 2:36–39 (in Chinese) Google Scholar
  5. 5.
    Wen BJ (2014) Research on coating anti-wear technology of injector’s sealing cone in diesel. South China University of Technology, Guangzhou (in Chinese) Google Scholar
  6. 6.
    Qian DH, Liao RD (2014) Review on piston/cylinder interface leakage research of high-pressure pump for diesel engine. Lubr Eng 9:108–115Google Scholar
  7. 7.
    Lu YZ (1982) Wear between the nozzle needle and body and its effect on operating reliability of fuel injector. J Xian Inst Metal Const Eng 2:85–94 (in Chinese) Google Scholar
  8. 8.
    Schlichting H (1968) Boundary layer theory, 6th edn. McGraw-Hill, New YorkGoogle Scholar
  9. 9.
    Yih CS (1969) Fluid mechanics. McGraw-Hill, New YorkGoogle Scholar
  10. 10.
    Wang SY (2004) An analysis on the leakage in precision pair of high pressure common rail fuel injector. Automot Eng 26(6):666–670 (in Chinese) Google Scholar
  11. 11.
    Daines James R (2012) Fluid power: hydraulics and pneumatics. Goodheart-Willcox Publisher, LllinoisGoogle Scholar
  12. 12.
    Schwab Scott D, Bennett Joshua J, Dell Steven J (2010) Internal injector deposits in high-pressure common rail diesel engines. SAE Int 3(2010-01-2242):865–878Google Scholar
  13. 13.
    Xu KY (2017) Research the application of 30 degree wedge angle of the thread in the flange nut. Equip Manuf Technol 4:129–131 (in Chinese) Google Scholar
  14. 14.
    Yamamoto (1980) The theory and computation of thread connection. Youkendo, TokyoGoogle Scholar
  15. 15.
    Huang J, Wang SY (2005) Basic information and latest development of common on rail systems of Bosch. Veh Power Technol 1:58–63Google Scholar
  16. 16.
    Pan SB (1987) The entrance effect of pipe. J Xinyang Norm Univ (Nat Sci Ed) 2:12–15 (in Chinese) Google Scholar
  17. 17.
    Gulhane Nitin P, Mahulikar Shripad P (2009) Variations in gas properties in laminar micro-convection with entrance effect. Int J Heat Mass Transf 52:1980–1990CrossRefMATHGoogle Scholar
  18. 18.
    Balluchi A, Bicchi A, Mazzi E, Sangiovanni A (2007) Hybrid modelling and control of the common rail injection system. Int J Control. 11(80):1780–1795MathSciNetCrossRefMATHGoogle Scholar
  19. 19.
    The Editorial Team of BOSCH, Robert Bosch GmbH (2005) Diesel-engine management, 4th edn. John Wiley & Sons Ltd, EnglandGoogle Scholar
  20. 20.
    Li Pimao, Zhang Youtong, Li Tieshuan, Xie Lizhe (2015) Elimination of fuel pressure fluctuation and multi-injection fuel mass deviation of high pressure common-rail fuel injection system. Chinese J Mech Eng 28(2):294–306CrossRefGoogle Scholar

Copyright information

© The Brazilian Society of Mechanical Sciences and Engineering 2018

Authors and Affiliations

  1. 1.School of Mechanical & Automotive EngineeringSouth China University of TechnologyGuangzhouChina

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