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International Journal of Automotive Technology

, Volume 20, Issue 4, pp 835–844 | Cite as

Theoretical and Experimental Study on Flow Characteristics of a Diaphragm Pump for Urea-SCR Systems

  • Shu Dong Yang
  • You Cheng ShiEmail author
  • Xi Wei Pan
  • Yin Shui Liu
Article
  • 6 Downloads

Abstract

Urea selective catalytic reduction (SCR) is the primary technology used to reduce the nitrogen oxides (NOx) of diesel engine exhaust. To meet the requirements of an SCR system, a novel type of miniature diaphragm pump was designed. Based on the theory of large deflection of annular plates, the equilibrium equations of a diaphragm with a rigid inclusion were established, and the equations were solved by the nondimensional method and the finite difference method. Theoretical and approximated flow model for this pump were proposed. A theoretical relationship between back pressure, rigid inclusion size and volumetric efficiencies were calculated. To verify the validity of theoretical model, a prototype pump was fabricated and tested. Experimental results demonstrated that the flow is proportional to the pump speed. The deviation between theoretical, approximated flow and experimental flow was less than 4 % and 9.4 %, respectively. The difference between theoretical and experimental volumetric efficiency was varied from 2.7 % to 6.1 % when back pressure changed from 0 to 0.9 MPa. The volumetric efficiency was growing with the increasing of the rigid inclusion size. The pressures in the working chamber showed almost the same overall trends between the theoretical results and experimental values. The experimental results show that the proposed theoretical model is effective.

Key Words

Urea-SCR Diaphragm pump Theoretical analysis Large deflection Flow characteristics Volumetric efficiency Pressure 

Nomenclature

pr

rated pressure (MPa)

p0

pressure in working chamber (MPa)

Q

actual flow (L/h)

Qt1

theoretical flow (L/h)

Qt2

approximated flow (L/h)

Qsh

instantaneous flow (L/h)

n

pump speed (rpm)

e

eccentricity of eccentric wheel(m)

l

connecting rod length (m)

P

output power (w)

R

effective radius of diaphragm (m)

b

radius of rigid inclusion (m)

h

average thickness of diaphragm (m)

E

elastic modulus (MPa)

v

poison’s ratio

ρR

density of rubber (kg/m3)

ρl

density of urea water solution (kg/m3)

wc

displacement of rigid inclusion (m)

w

diaphragm deflection

w

element of w

uc

velocity of rigid inclusion (m/s)

a

acceleration of rigid inclusion (m2/s)

a1

acceleration of liquid in the pipe (m2/s)

φ

phase angle of pump shaft (rad)

ω

angular velocity of pump shaft (rad/s)

S

distance between the top and bottom dead center

F0

connecting rod force (N)

m

mass (kg)

Mm

output torque of motor

Ft

shear force (N)

Ft

reacting force of Ft

Fg

inertial force of liquid (m)

Fs0

preload force of spring (N)

Fs0m

maximum spring force (N)

pt

shear force (N/m)

pt

reacting force of pt (N/m)

ηp

transmission efficiency (%)

ηv

volumetric efficiency (%)

Nr

radial force per unit length along the circumference (N/m)

Nθ

circumferential force per unit length (N/m)

D

flexural rigidity of rubber (N·m)

r

radius (m)

εθ

strain

u

radial displacement (m)

mi

mass of valve core (kg)

ms

mass of spring (kg)

Δp

pressure drop across port valve (MPa)

υk

max velocity of fluid at valve port (m/s)

rv

radius of pressure bearing surface (m)

Ai

cross-sectional area of valve chamber (m2)

fi

spring preload value (m)

Δf

displacement of valve core (m)

ksi

spring stiffness (N/m)

L

length of pipe (m)

Ap

sectional area of inlet pipe (m2)

V1

volume of working chamber under pressure p0 (m3)

V0

volume of working chamber at top dead center (m3)

K

bulk modulus of fluid (MPa)

Vs

approximated displacement of pump (m3)

Vt

theoretical displacement of pump (m3)

N

odd number

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Notes

Acknowledgement

This work was supported by the Science and Technology Planning Projects of Jiangsu Province, the People’s Republic of China (BY2016025-01).

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Copyright information

© KSAE 2019

Authors and Affiliations

  • Shu Dong Yang
    • 1
  • You Cheng Shi
    • 1
    Email author
  • Xi Wei Pan
    • 1
  • Yin Shui Liu
    • 1
  1. 1.School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhanChina

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