Applied Scientific Research

, Volume 40, Issue 1, pp 7–37

Investigation of water jet pulses generated by an impact piston device

  • Göran Rehbinder
Article

DOI: 10.1007/BF00539374

Cite this article as:
Rehbinder, G. Appl. Sci. Res. (1983) 40: 7. doi:10.1007/BF00539374

Abstract

High speed water pulses for destruction of rock, concrete etc. have been studied for more than a decade. The high speed pulses can be created in different ways and some investigations have been published about supersonic pulse generators. In this paper a device called impact pipe is studied theoretically as well as experimentally. In an impact pipe the impact velocity of a piston is transferred to pressure in a pressure chamber provided with a small nozzle through which a jet comes out. It is shown that theoretically the maximum pressure of 400 MPa is achieved if the length of the impacting piston is sufficiently long. Pressure measurements and high speed photography show that the water pulse coming out through the nozzle has violent radial bursts due to the pressure waves in the pressure chamber.

Symbols

a

cross sectional area of the nozzle exit m2

A

cross sectional area of the pressure chamber m2

cs

velocity of sound in the pistons ms−1

cw

velocity of sound in the liquid ms−1

cwf

fictitious velocity of sound in the liquid ms−1

Cp

specific heat capacity of the liquid Jkg−1K−1

d

diameter of the nozzle exit m

D

diameter of the pressure chamber m

Es

modulus of elasticity of the pistons Pa

Ewf

modulus of elasticity of the liquid Pa

F(t)

force at the liquid caused by the piston N

h

height of the pressure chamber m

\(\overline \ell \)

average diameter of the grains in a rock m

l

length of the nozzle m

le

effective length of the nozzle m

Lj

length of the liquid pulse m

Lk

length of the compression piston m

Ls

length of the impact piston m

M

mass of the impact piston kg

n

normal to the control surface S

p(t)

pressure in the liquid Pa

Pa

average pressure in the liquid Pa

r

position vector

r0

radius of the nozzle exit m

R0

radius of the nozzle inlet m

S(t)

control surface

t

time s

t0

duration of water pulse s

U0

impact velocity of the impact piston ms−1

T

temperature K

u

velocity of the liquid ms−1

u

axial component of u in the nozzle ms−1

v(t)

velocity of the liquid at the nozzle exit ms−1

V(t)

control volume

x(t)

displacement of the piston m

β0

volume expansion coefficient of the liquid K−1

δ(t)

boundary layer thickness in the nozzle m

ρ(t)

density of the liquid kgm−3

ρw

initial density of the liquid kgm−3

η

efficiency

σi

stress wave in the compression piston Pa

σr

stress wave in the compression piston Pa

ν

kinematic viscosity of the liquid m2s−1

µ

dynamic viscosity of the liquid kgm−1s−1

φ

velocity potential m2s−1

κP

modified permeability of rock m2

ξ

axial coordinate in the nozzle m

Copyright information

© Martinus Nijhoff Publishers 1983

Authors and Affiliations

  • Göran Rehbinder
    • 1
  1. 1.Research FoundationSwedish Rock MechanicsStockholmSweden

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