INFLUENCE OF WORKING REGIME ON HYDRAULIC PRESSURE AND FLOW RATE OF DRIVEN MOTOR IN a CORAL ROCK CUTTER OF DREDGERS

INFLUENCE OF WORKING REGIME ON HYDRAULIC PRESSURE AND FLOW RATE OF DRIVEN MOTOR IN A CORAL ROCK CUTTER OF DREDGERS Huu Ly Tran Military institute of mechanical engineering 42 Dong Qua

INFLUENCE OF WORKING REGIME ON HYDRAULIC PRESSURE AND FLOW RATE OF DRIVEN MOTOR IN A CORAL ROCK CUTTER OF

DREDGERS

Huu Ly Tran

Military institute of mechanical engineering

42 Dong Quan, Ward Quan Hoa, Dist Cau Giay, HN, Vietnam

Email: huulytran69@gmail.com; Tel: 0915 555 551

ABSTRACT:

The cutting non-explosive equipment has

been widely used and is an alternative solution to

avoid the negative impact of construction projects

on the environment Also, these devices can use

to carry out the construction projects near conflict

areas There are many different types of them that

come from the differences in the way that soil/rock

excavated (either mechanical or hydraulic):

hydraulic hammer, clamshell dredger, backhoe

and front shovel, hydraulic/mechanical dredgers

In this study, the interaction between a cuter of hydraulic dredgers with coral rock is first modeled Then, the effects of different type of rocks and productivity on the working parameters of hydraulic system of driving motor are investigated The obtained results provide a background knowledge for geometric and structural tailoring of the cutter in manufacturing an effective design of such dredging equipment for coral excavation with

no blasting

Keywords: coral rock cutter, pressure, flow rate, force, torque

1 Introduction

Recently, transportations of passengers and

goods by marine transportations systems oversea

or to reach islands are required of the developing

of dredging technology As mentioned above,

non-explosive approach is one suitable choice for

carrying out this task Rock excavation due to

device with the teeth (bits) could be useful for

conserving the geometrical foundations as well as

environments A number of previous works was

interested in the interaction between teeth and

materials such as Dombroski, A N Zelenhin, Ju

A Vetro… (see [1] for a details survey on

modeling of cutting rock or soil) This model is

widely used to calculate the resistant force for the

designing of moving earth machines However, for

the dredging process, the reference formula of this

method needs some improvements In the year of

1989, Miedema [2] provided a study on modeling

of the interaction between the excavating element

and the soil, for dredging vessels in swell In order

to elucidate the complex phenomena occurring in

the interaction area between the bits and the rock,

Iosif Kovacs et al [3] considered a model for

calculating three components of cutting forces

corresponding a given movement of the active

parts (tools) It is noted that these models were developed continuously with the works for designing the cutting head for a dredger [4], and considering the heterogeneity and anisotropy properties inside the structure of rock [5]

In this paper we employ the above method for investigation the influence of working conditions on the pressure and flow rate in hydraulic system of driven motor on the cutter-head attached on an amphibious excavator (see Figure 1)

Figure 1 An amphibious excavator with

cutter-head for dredging task

2 Interaction between cutterhead and coral 2.1 Calculating the resisting force and driving torque

Currently, there are two cutting methods are

applied in dredging using a head cutter, it depends

on the directions of the teeth and the rotation

Under cutting: the movement of cutting teeth from

ground to surface (Fig 2a) and Over cutting: the

cutting teeth moving from the surface into the

ground (Fig 2b) The diagram of calculating the

resisting force is shown in Fig 3

Figure 2 The diagram of calculating the resisting

force

These assumptions are:

The coefficients c1, c2, d1 and d2 have to be

constant for the case calculated, this

means that an average thickness of the layer cut

has to be chosen

The cutterhead is a conical cutterhead with a top

angle ξ

The blades have an angle t with the axis of the

cutterhead

The equation for the thickness of the layer cut is

simplified to:

s

max

v 60

h

np

 









The projected width of a blade on the axis of the

cutterhead is:

pr

b  bcos cos  

When the swing velocity is neglected, the cutting

velocity can be simplified to:

ciR

v v cos

2 Rn

v

60















 (2)

t

2 Rn sin

v

60

 (3)

a

 



The derived model is applicable for a segment of the cutterhead with a projected width bpr and a radius R For a conical or a crown cutterhead the calculation has to be repeated for each segment

Figure 3 The cutting process of a cutterhead

According to [2] the sum of average resisting force

is calculated by summing local resisting force apply on the cutting head:

0

0

p

2 



   (5)

In which:

p- The number of cutting teeth, [piece];

Fct- Average resisting force, [N];

- Angle at center of the cutting arc, [rad];

0- The maximum angle at center, [rad];

The force and torque are determined as following:

+ The sum of resisting force in s-direction

1 1

2

+ The sum of resisting force in v-direction

(7)

+ The sum of resisting force in axial direction

0 1

1

2

0







+ Driving torque

0 1

1

2

0

M c g R sin d c g R sin d







       

(9)

In Which:

The coefficients cnc and cca, which have the

dimension of force (kN), can be calculated by the

following equations:

2

m ciR

.g.b v

k



p

.g.b (z 10)

2



ca Cavitating cutting proces;

nc Non-cavitating cutting proces;

bpr = bv⋅cos ι⋅cosξ

bpr Width of blade projected on axis [m];

bv The parameters are investigated: the cutting

depth [m];

vci,ciR Circumferential velocity, [m/s];

himax Maximum thickness of layer cut, [m];

g Gravitational constant (9.81), [m/s²];

km Average permeability, [m/s];

z Water depth, [m];

e Volume strain, [%];

w

 - Water specific gravity, [kg/m3];

g  c cos t.cos ; (12)

2

g   c sin t.sin cos    c cos ;

g  d ;

cos

g d tan t.sin d

cos t





2

g  c sin t.cos   c sin cos   ;

sin

g d tan t.cos d

cos t





t - Angle of blades with axis cutterhead [rad]; R- Radius of cutting head, [m];

s

v - The velocity of cutting head in h-direction, [m/s];

n- The rotational speed of cutting head, [rpm];

ba- The cutting width of teeth in axial direction, [m];

- The cone angle of cutting head, [rad];

t - The inclined angle of cutting teeth in axial direction of cutting head, [rad];

c

v - The long velocity of cutting teeth, [m/s];

m

h - The maximum cutting thickness, [m];

i

h - The cutting thickness, [m];

1

 - The angle occurs cavitation, [rad];

c ;c - Cutting coefficient;

d ;d - Resisting force coefficient

2.2 Calculating the pressure of the hydraulic driving motor

Hydraulic motor drive the cutting head through a mechanic transmission The torque of hydraulic driving motor generate must satisfy following conditions:

(13)

where i is ratio of transmission and i is transmission efficiency

According to [7] the torque on sharp of hydraulic driving motor is calculated as follow:

20

m m

pq





(14)

With: p- Pressure of hydraulic oil in driving motor

(Bar); qm- Displacement of hydraulic driving motor

(cm3/rev); m-Hydraulic motor efficiency

Combine (13) and (14) we obtain the relation

between hydraulic pressure and resistive torque:

20

m m i

M

 

  (15)

From (9) and (15) we have:

0 1

1

2

0

m i m

p

iq



 







(16)

3 Discussion on the relative influence of

working regime Running Text

We used the researching data on the coral

foundation [6] and [2]

Tab 1 Input parameters

0.291 0.202 2.303 1.424 1000 9.81

30o 33.636 o 37o 21o 80 10

b z v s ι ξ R

0.2 0.6 0.2 30o 30o 0.5

Specific capacity of hydraulic is used in this

investigation corresponding qm (1) = 60 (cm3/rev);

qm (2)= 80 (cm3/rev); qm (3) = 100 (cm3/rev); qm

(4)=120 (cm3/rev) The parameters are

investigated: the cutting depth bv, rotational speed

of cutting heead n, feed velocity vs By using

Mathlab code to investigate equation (16) we are

obtained the following results

3.1 The effect of the cutting depth, b v

As the cutting depth increase lead to increase the

resistance force, consequently, the oil pressure of

hydraulic motor rises almost linearly (Fig 4) The

same cutting depth, if using a drive motor with

greater specific capacity, the pressure in the

driving motor will be smaller At the cutting depth

of 0.45 m, the specific capacity of the motor is 60

cm3/rev and 120 cm3/rev, the pressure in the

motor is 180 bar and 88 bar, respectively

Figure 4 The effect of cutting depth on the oil

pressure

3.2 The effect of the rotational rate, n

The rotational speed of cutting head has a great influence because of it is related directly to the thickness of the cut As the rotational speed increases, the oil pressure in the driving motor decreases rapidly (Figure 5) due to the cutting force decrease dramatically In addition, at the same speed, if the drive motor has a higher specific capacity, the oil pressure of driving motor will be smaller

3.3 The effect of the cutting head feed velocity, V s

As the cutting head rise, consequence the cutting thickness increases, so that the cutting force increases As a result, the driving torque also increases and the oil pressure in the driving motor increases as well (Figure 6) At the same feed velocity, if the drive motor has a higher specific capacity, the oil pressure in the driving motor will

be smaller

Figure 5 The effect of rotational speed on the oil

pressure

Figure 6 The effect of the cutting head feed

velocity on oil pressure

4 Conclusions

This paper presents the method for defining the

cutting force, driving moment and working

pressure in the hydraulic motor used for a

cutter-head for the task of dredging Additionally, we

investigate the influence of working parameters of

this cutter-head on the hydraulic pressure for 4

different levels of hydraulic displacement, qm The

results show that the enhanced of driving pressure

is accompanied by an increase in the cutting deep,

it seems to be a linear correlation Our predictions

also point out that the motor’s pressure decreases

sharply with a rise in its rotational rate, this law is

obtained when we use this cutter with high cutting speed In the case with given working conditions,

in order to lower the motor’s working pressure, using motors with higher hydraulic displacement could be a suitable technique

References

[1] Pham Van Dong, Luu Duc Thuan, and Hoang Van Ngu, Earth moving machine, 2004 (in Vietnamese) [2] A Miedema, “The Cutting Forces in Saturated Sand

of a Seagoing Cutter Suction Dredger”, Processding WODCON XII, orlando, Florida USA, April 1989 [3] I Kovacs, M.-S Nan, and I Andras, “Study of the interaction of the cutting heads of the rock cutting machines with rocks”, University of Miskolc Series A Mining, vol 65, no A, pp 73–93, 2004

[4] W Vlasblom, Dredging equipment and technology - Chap3: The cutter suction dredger, 2003, vol 1 [5] L Mamet’ev, A Khoreshok, A Tsekhin, and A Borisov, “Stress Distribution in Attachments of Disc Cutters in Heading Drivage”, Journal of Mining Science, vol 51, no 6, pp 1150–1156, 2015 [6] H X Luong, Research on technical factors of the coral foundation and the interaction between construction structure and coral foundation 2010 KC.09.07/06-10, (in vietnamese)

[7] http://www.hidraulicapractica.com/motors/hydraulic-motor-formulas-metric-units

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