Nghiên cứu xác định một số thông số tối ưu của máy chữa cháy rừng bằng đất cát ttta

MINISTRY OF AGRICULTURE AND
RURAL DEVELOPMENT

MINISTRY OF EDUCATION AND
TRAINING

TRƯỜNVIETNAM NATIONAL UNIVERSITY OF FORESTRY
LÊ NGỌCC

HOANG MINH HOA

DETERMINING SEVERAL OPTIMAL PARAMETERS OF FOREST
FIRE FIGHTING EXTINGUISHER

MAJORITY: MECHANICAL ENGINEERING
CODE:

SUMMARY OF ENGINEERING DOCTORAL THESIS

HA NOI, 2021


Research work is completed at: Vietnam National
Forestry Trường Đại học Lâm nghiệp Việt Nam

University of

Scientific instructors:
Scientific instructor 1: Ass. Dr. Duong Van Tai
Scientific instructor 2: Dr. Tran Van Tuong

Chương
Reviewer 1:……………………………………………
Reviewer 2:……………………………………………
Reviewer 3:…………………………………………….

The defense will be taken in front of the Institutional Board of
Thesis Evaluation at: Vietnam National University of Forestry
At: … time, Date ….Month…..Year 2021Thn

The thesis can be found in the libraries:
National Library; Vietnam National University of Forestry Library


I. INTRODUCTION
1. Introduction
Vietnam has about 14.8 million hectares of forests, in which forests are mainly
concentrated in places with complex topography and high slopes. Annually, external
forest resources provide a large volume of special forest products for various industries.
Forest resources also help regulate the climate, protect water sources and prevent soil
erosion, but our country's forest resources are at risk of being degraded, one of the reasons
is due to the situation of forest fires on a daily basis become more and more serious [1].
According to statistics from the Forest Protection Department [1], within 10 years
(2010 - 2020) in Vietnam, there have been several thousand forest fires, causing hundreds
of thousands of hectares of forest damage. On average, about 15,000 hectares are
damaged each year. Not only is it lost in terms of resources, but it also affects human
lives, material possessions and the ecological environment.
Stemming from the urgent need for forest fire fighting equipment, in 2008 the
Ministry of Science and Technology assigned the Forestry University to carry out the
state-level key project: "Technological research, design and manufacture specialized
equipment for forest fire fighting" code: KC07.13/06-10. The results of the project have

designed and manufactured a forest fire fighting machine made of sand, which has been
used in many localities with high efficiency in fighting forest fires. However, the
equipment still has many shortcomings such as the large vibration of the machine, the
volume and pressure of the sand sprayed on the fire is not high.
The cause of the above-mentioned shortcomings is that the national key topic only
focuses on calculation, design and manufacture, there is no research on optimal
calculation, no in-depth study on the dynamics of the machine. In order to have a
scientific basis for perfecting a forest fire fighting machine with sandy soil, it is necessary
to conduct in-depth research on dynamics, research and optimize some parameters of the
machine. Stemming from the above reasons, the thesis conducted a research with the title:
"Determining several optimal parameters of forest fire fighting extinguisher".
2. Research objectives
Build a scientific basis from which to calculate and determine the optimal values of some
parameters of forest fire extinguishers using sandy soil, ensuring the volume and pressure
of sand sprayed on the fire. , in order to improve the effectiveness of extinguishing forest
fires and reduce machine vibrations.
3. New contributions of the thesis
3.1. The thesis has built a dynamical model, established the equation for calculating the
shearing power - pulling the ground, the differential equation of vibration of the earth
breaker, the results. Surveying the cutting capacity - pulling the ground, the vibration
equation of the earth cutting system is the scientific basis for determining the optimal

1


values of the parameters of the earth cutting system and proposing solutions to reduce the
vibration of the machine. cutting land to fight forest fires.
3.2. A dynamic calculation model of the exhaust fan and soil spray has been built for
forest fire fighting, and the pressure and velocity of the suction fan and soil sprayer have
been investigated, the survey results are the scientific basis for calculation. Optimize the

exhaust fan and spray soil to fight forest fires.
3.3. By experimental research, the thesis has determined the optimal values of some
parameters of the sandy soil forest fire fighting machine which are: Diameter of steel disc
D=15 cm; soil cutter length L = 6 cm; outlet assembly angle of the exhaust fan and
ground spray is β2 = 100 degrees; the number of blades of the suction and soil spraying
fan Z = 18, the above parameters are the scientific basis for perfecting the forest fire
fighting machine with sandy soil.
4. Scientific significance of the thesis
The research results of the thesis have built a scientific basis to calculate the dynamic
parameters of the forest fire fighting machine with sandy soil, and at the same time, the
thesis has built an experimental method to determine a number of information. kinematics
of the machine. From the results of theoretical and experimental research, it is possible to
make scientific documents for calculating, designing, and perfecting specialized
equipment for forest fire fighting.
5. Practical significance of the thesis
The research results of the thesis are used for the design, manufacture and
completion of forest fire fighting machines with soil and sand, designed and manufactured
by the state-level key project, and also used as a reference. for the research, design, and
manufacture of equipment with a hammer-type soil cutting system such as a tree planting
hole excavator on sloping land, a system for digging soil and sucking and spraying soil on
a multi-purpose forest fire fighting vehicle.
Chapter 1
OVERVIEW OF RESEARCH ISSUES
1.1. The research works on forest fire fighting equipment in the world
Forest fire fighting is a matter of great concern to the governments of many
countries. has obtained many great achievements, the researches have been relatively
complete, from the research results have created devices for practical use. One of the
biggest shortcomings of the above studies is the use of water-based fire extinguishing
agent, so the operating range of the device is still limited. In fact, forest fires mainly occur
in the dry season, so there is no water source, leading to inoperability of the equipment.

Therefore, it is necessary to research to find out the available extinguishing agents in
place such as air and sand.
China is the leading country in the research of wind-powered fire extinguishers, there

2


have been many research projects on this machine, there are many factories and
companies producing wind-powered fire extinguishers. But the wind-powered fire
extinguishing machine still has many shortcomings that need to be researched and
perfected, such as increasing the speed and air flow, reducing the weight of the machine.
Currently, the published works on optimizing research on forest fire fighting machines by
wind power, as well as forest fire fighting machines with sand in the world are very
limited.
1.2. Research works on forest fire fighting equipment in Vietnam
From 2006 to 2007, Dr. Duong Van Tai University of Forestry has carried out a
project at the Ministry of Agriculture and Rural Development: "Research, testing and
improvement of forest fire fighting equipment using sand, air and water in the form of
mist" [18], the results of the project have designed and manufactured a model of a forest
fire fighting machine using sandy soil, the topic has not yet had a comprehensive and indepth study of a sand fire extinguisher, but only focused on the design part. , improve.
In 2010, the author Duong Van Tai published the results of a state-level key research
project code KC07.13/06-10 [19]: “Technology research and design and manufacture of
specialized equipment forest fire fighting", the results of the project have designed,
manufactured and tested a forest fire fighting machine with sand. The sand-based forest
fire fighting machine has been granted a patent for utility solution by the National Office
of Intellectual Property No. 936. However, the topic has not studied the dynamics of the
excavation system, has not studied the optimal calculation of the system. Soil excavation,
soil suction and spraying system mainly focus on design, manufacture and testing.
In summary: There have been a number of studies on forest fire forecasting and fire
prevention with great effectiveness, while research on specialized equipment for forest

fire fighting is still limited. The research and creation of specialized forest fire fighting
equipment suitable for topographical conditions, forest types, vegetation types, suitable
for on-site fire extinguishing agents is absolutely necessary and timely in the current
period. Therefore, the topic: "Research on some optimal parameters of forest fire fighting
machines with sand" is very necessary and topical.
Chapter 2:
SCIENCE OF CALCULATION OF WORKING SYSTEMS OF SAND
FOREST FIRE FIRE FIGHTING SYSTEM
2.1. Building a computational model for the system of soil cutting, soil suction and
soil spraying on fire
2.1.1. Calculation model of the system of soil cutting, suction and soil spraying on the
fire

3


From the structure and operating principle of the sandy soil forest fire fighting
machine, the thesis builds a computational model of the sandy soil forest fire fighting
machine. shown in figure 2.1.

Figure 2.1: Calculation diagram for soil cutting, soil suction and soil spraying system
1-Forest land; 2- Steel disc; 3- Soil cutter; 4- Covering 5- Soil after cutting; 6- Soil
suction pipe; 7- Suction and spray fan; 8- Soil spray pipe; 9- Suction chamber; 10Suction pipe
- Principle of operation: The earth cutting system cuts according to the cutting
principle in the form of a hammer, the earth cutter (3) is fitted with a steel disc (2) with a
joint (O'), when the cutter operates, it rotates around the point O. and point O'. The steel
disc rotates at a high speed, so the cutter stores a large kinetic energy, when it comes into
contact with the ground, generates a large impact impulse, the impact impulse turns into a
force to cut the ground, with this large impulse the earth is broken. and bounce with the
cutter. The exhaust fan (7) creates in the suction pipe (6) a large air velocity, at the inlet

(6) the soil is drawn into the suction pipe (6) and into the suction chamber (9); At the
suction chamber (9) the soil is sucked by the propeller (7) and sprayed out through the
nozzle (8) at high speed to extinguish the fire. The working principle of this system is:
Using a cutter to cut the soil, toss the soil up, use the suction and push fan with great
suction and push pressure to suck and spray the soil on the fire.
From the calculation model in Figure 2.1, the thesis needs to solve the following
three problems:
- The first problem: Building a dynamic model to calculate the soil shear system of

4


the earth cutter to the ground shear force. is the largest, the cost of cutting energy is
minimal, and the volume of soil excavated and lifted is the largest.
- The second problem: Building a vibration model of the earth breaker to establish
the differential equation of the machine's oscillation, thereby providing a solution to
reduce the vibration of the machine.
- The third problem: Building a computational model of the exhaust fan and soil
spraying system so that the volume of soil and the pressure of soil sprayed on the fire are
the largest.
In the following, the thesis conducts research on the problems mentioned above to
meet the requirements of forest fire extinguishers with sand, which are: The volume of
soil and the pressure of soil sprayed on the fire is the largest, the vibration of machine is
the lowest, from which the fire extinguishing efficiency of the machine increases,
minimizing the impact on the health of workers operating the machine.
2.1.2. Structure and operating principle of earth cutting system
2.1.2.1. Structure of the earth cutting system
The earth cutting machine has the structure as shown in Figure 2.2.

Figure 2.2: Model of ground cutting system

1. Gasoline saw engine; 2. Belt transmission; 3. Steel disc for mounting the cutter; 4.
Knife mounting bolts; 5. Knife to cut the ground; 6. The plate embellishing the suction
chamber.
2.1.2.2. Working principle of earth cutter
The rotational torque from the motor shaft is transmitted through the cone and
transmits the motion to the belt, through the belt transmission causing the steel disc to
rotate. On a steel plate with cutters mounted, the cutter rotates about its axis. When the
cutter movement consists of two movements, it rotates with the steel disc and rotates
around its axis creating an impulse. When the knife is in contact with the ground, the
impulse of the knife turns into a cutting force. Due to the short impact time, the cutting
force increases greatly. On the cutter, there is a wedge-shaped cutting edge (like a manual

5


earth hoe), with a strong force. large cutting causes the blade to penetrate the soil to break
the structure of the soil at the same time with the movement of the steel disc the blade of
the cutter conducts the earth pull to break the soil structure and pulls the soil along with
the cutter, partly The back ground is cut up with the movement of the cutter. Each
revolution of the steel disc performs a cutting process.
2.2. Setting the system of equations of motion of the mechanical system: Disc scissor-slasher
The establishment of the system of differential equations of motion of the system
aims: Through the investigation of these equations, it can be given get reasonable
machine detail sizes. For disc: Radius length and moment of inertia; for cutters: Length,
moment of inertia, cutter head type...
On the basis of the structure and operating principle of the earth cutter, we can model
the following mechanical problem

Figure 2.5 Dynamic model of the system: Disc - ground scissor blade
The steel disc for mounting the ground scissor with mass M rotates about the

horizontal axis O with a constant angular velocity (rad/s), half disc glass R. On the disc
are mounted two hammer rods of length L, the ground-cutting hammer ith rotates around
point Oi (referred to as rod OiA) mounted on the disc with distance OOi = R. The
hammer bar has density (in the direction). length: kg/m).
Set up a coordinate system: Oxygen as shown (Ox is downward, Oy is horizontal).
Let the angle formed by OOi and Ox be , the angle formed by the hammer OiA with Ox ,
and the angle made by the hammer at points Oi with radius OOi γi.
Thus, if 1 = φ is taken, then φ2 = φ + π. Thus, in the general case, the disc-hammer
mechanism has three degrees of freedom: the angles γi and the angle φ.
In case the disk rotates with uniform angular velocity ω, only two degrees of freedom
remain, namely angles γ1 and γ2.
Let J1 be the moment of inertia of the disc about the axis Oz.


Kinetic energy of the disc: : TĐ = J1.
(2.1)
2
where is the angular velocity of the disc. Call the point N(x,y) on the segment OiA.
2

6


Select local coordinate system Oix' on bar OiA, positive direction Oix' in direction
OiA. There are coordinates O1(0), point A(L).
The point N(x,y) is about :
x = R cos  + cos  ; y = R sin  + sin 
(2.2)
Hence: x   iR sin i  i sin i ;

y iRcosi  i cos i

(2.3)

Kinetic energy of rod segment OiA
L
(iRcosi  i cos i ) 2   iR sin i   i sin  i 
(x 2  y 2 )
TOiA   
d  
d
2
2
0
0
2

L

TOi A

L 2 2
L3 2
L2
  R i    i   Ri i.cos  i   i 
2
6
2

(2.4)

The potential energy of the hammer OiA
U Oi A   g



Oi A

L

xd   g   Rcosi  cos i  d
0

(2.5)



L2
UOi A   g  L.Rcosi 
cosi 
2



2.2.1. Calculating the work generated during the cutting process
a) Calculation of the earth shear force generated by the cutter
The shear force generated by the cutter is calculated by the following formula:
Pmax =

R+l

l2

(R+l)ω

Jo1 ω .

√gΔt)

×

1

(2.6)

t1

The soil breaking force is calculated according to the following formula:

2h 2
Pc 
 gh
3

(2.18)
b, Calculate the earth shear and earth splash angular momentum of the cutte

 2
 Ph
L3
RL2

J1   R L.    i  
2  i  cos( i )   c

3
2
i 1 
 
Skv  m G b
2


 
L3
2
2
2
J
+
m
.
b


L.R


RL
co
s
(


)
 1


G
i 
3
i 1 

 
2

(2.30)

c) Work produced by the earth shear - pulling momentum (average): Ac-v

A c  kv


2 
 Pch 
L3
RL2
2


J



R
L.




2


cos(

)







1
i
i
i
3
2
 
2m G b 2

i 1 


  Pc 
 bt
3
2 

b  2h
 
L
2
2
2


J1 + m G .b    L.R   RL cos( i )  


3
i 1 

 



2.2.2. Calculate the power to cut – pull the ground

7


N c  kv  

Ac  kv
t

2

 2
 Ph 
L3
RL2

J


R
L
.




2  i  cos( i )   c 




1
i
2
3
2

2mGb 

i 1 
  
 b  Pc 

3
2

b  2h
 2 L
 
2
2


 J1 + mG .b    L.R   RL cos( i )  


3
i 1 

 



The symbols in formula (242) are as follows:
b - the distance from the center of the steel plate where the tool is mounted (point O)
to the tip of the tool (point A);
mG - mass of soil towed and splashed;

J1 - moment of inertia of the steel disc fitted with the cutter;
ρ – mass density per length of earth cutter;
R- radius of steel plate with cutter (from center to tool mounting point);
L - length of earth cutter;
ɷ - angular velocity of the steel disc fitted with the earth cutter; Pc- earth shear force;
γ – the angle between the line (OO1) and the cutter (O1A).
Comment: The power of the earth cutting motor depends on many factors such as
the radius of the steel disc R1, the length of the earth cutter L, the angular velocity ɷ, the
weight of the cutter..., to determine the influence law. Of these factors, we examine the
equation for calculating the engine's power (2.42).
2.3. Calculation of vibration of earth shear system
2.3.1. Building a vibration model of the hammer ground cutter system
When operating the hammer cutter, the user places the machine horizontally on the
ground and holds it with both hands at the two handles (Figure 2.7), The connection
between the machine body and the earth cutting system with the upper handle is a C1
stiffness spring, the horizontal handle is a C2 stiffness spring. The oscillation equation of
the hammer ground cutter system is built on a dynamic model. the force depicted in
Figure 2.7b.

Figure 2.7 : Vibration model of a hammer earth cutter

8


In which: m1 - the converted mass of the engine and chassis located at the point O3,
kG;
m2 - converted mass of earth cutting system including steel disc, earth cutter
located at point O, kG
C1- Stiffness of spring connecting machine with upper handle
C2- Stiffness of spring connecting machine with horizontal handle

The center of gravity of the machine is at O2, when the scissor throws the ground,
creating a binding reaction in the form of an impulse acting on the disc shaft at O. The
vibration calculation model of the earth cutter is shown in Figure 2.7.
2.3.2. Set up the system of oscillation equations
Choose the coordinates of the generalization as y and φ.

T
With kinetic energy:
T





2
mv 2 m 2
m
2
2

x  y   y y   y 


2
2
2





m 2 2
2
2
y   y   1  2 yy 


2

Or
(2.43)
Leads to the system of differential equations for the oscillation of the ground
scissors:

m  2 yy  y 2  y y   C1 ( y  a)2   mgy  Q

 

2
2
2
m  y   1  y  2 y  y   C1 ( y  a)  C2 ( y  L2 )  mg   Qy
(2.49)
2.4. Theoretical basis for calculating the soil suction and spraying system on the fire
2.4.1. Determine the velocity of the air flow in the vertical pipe
vcb = 4,7√dγh , m/s
(2.70)
Thus, in order for the sandy soil to move in the vertical pipe, the air velocity is greater
than
the

equilibrium
velocity
calculated
by
formula
(2.70).
2.4.2. Determine the velocity of the air flow in the horizontal duct
G

vcb = √

ϕ(1−ϕ)π.d.l.ρ

(2.71)

Where: 𝜌 - density of air, kg.s2/m4;
l- length of the prismatic grain, m;
d - diameter of the prism, m;
2.4.3. Calculation of suction pressure of suction and soil injection fans
The outlet assembly angle is the angle formed by the tangent line of the outer
diameter of the blade to the tangent of the blade at the outlet point of the blade, referred to
as the outlet angle, symbol β2.
For centrifugal fans, the inlet assembly angle β1 and the outlet assembly angle β2
are two important criteria that determine the basic shape of the impeller. Based on the

9


shape, based on the large and small values of the angle β2, the centrifugal propeller is
divided into 3 types:

- β2 > 900 is called forward curved blade (Figure 2.14a);
- β2 < 900 is called backward curved wing (Figure 2.14b);
- β2 = 900 called the radial wing (Figure 2.14c).

Figure 2.14: Dynamic model to calculate the pressure of suction fan and ground
spray
a - Front curved blade; b - Back curved wings; c – Radial vane
a) Calculate the velocity of the output air of the exhaust and spray fan
To calculate the output velocity of the suction and soil injection fan, the thesis
makes the calculation diagram in Figure 2.15.
W

C





U

R2

R1



Figure 2.15: Calculation diagram for the output air velocity of the exhaust fan and
soil spray.
The symbols in the diagram for calculating the name of Figure 2.15 include:
- R1- radius of the outer circle of the reel;

- R2 - radius of the circle of the wing;
- Angle α is created with radius R1 with the line connecting the centers O and O1.
The absolute velocity of the gas flow at the outlet is calculated as follows:

C  U 2  W2  2UW cos 
U = w1 R1
W = w2 R 2 = aw1 R 2 = aw1 R1 sin α = aw1 R1 sin( 180 − β2)
We have α = 180 - β2
The absolute velocity of the outlet gas is calculated as follows:
With

10


C
= √(w1 R1 )2 + (aw1 R1 sin( 180 − β2))2 + 2a(w1 R1 )2 sin( 180 − β2) cos( 180 − β2)
(2.73)
b) Calculation of pressure of suction and soil spraying fans
From the diagram of Figure 2.15, the pressure of the suction and spray fans
is calculated according to the following formula:
𝐻𝑘 =

𝑈2 𝐶 𝑐𝑜𝑠𝛼
𝑔

(2.74)

In which: Hk - Pressure of the suction and spray fans, bar ; η - Performance; k - Resistance
loss coefficient,
According to the Sin theorem in Figure 2.15a, we have:

C=

𝑈2 .𝑆𝑖𝑛𝛽2

(2.75)

𝑆𝑖𝑛(𝛼+𝛽2 )

Substituting the data into formula (2.74) we have:
Hk =

𝑈2 2 .𝑆𝑖𝑛𝛽2 .𝐶𝑜𝑠𝛼
𝑔.𝑆𝑖𝑛(𝛼+𝛽2 )

. 𝜂. 𝑘

(2.76)

Chapter 3
SURVEYING FACTORS AFFECTING THE DYNAMICS
OF SAND LAND FOREST FIRE
3.1. Investigate factors affecting soil shear-stretch capacity
Based on experimental results in the documents [18]; [19], the thesis investigates
the factors affecting the cutting capacity - pulling the ground according to the formula
(2.42).
3.1.1. The influence of the kinematic radius of the steel disc on the shear-stripping
power
The effect of the radius of the steel disc fitted with the cutter on the shear-stripping
power is shown in Figure 3.1.

Figure 3.1: The influence of the radius of the steel disc fitted with the cutter on the
cutting capacity - pulling the ground

11


From the results obtained on the graph 3.1, the following comments are made:
- The power of cutting-stripping earth is covariable with the radius of the steel disc,
when the radius increases, the long speed of the cutter increases, the kinetic energy of the
cutter increases, resulting in an increased impulse, so the power cutting also increased.
3.1.2. The influence of the cutter length on the cutting capacity - soil pulling
The influence of the cutter length on the cutting capacity - pulling the ground is shown in
Figure 3.2.

Figure 3.2: Effect of cutter length on cutting capacity - ground pulling
3.1.3. Effect of cutter mass density on cutting power - soil pulling
The influence of tool weight on cutting power - soil pulling is shown in Figure 3.3.

Figure 3.3: Effect of tool mass density on ground shear-stretch power
From the obtained results, the following observations are made: The cutting power - earth
pulling is covariant with the mass density of the cutter, when the density of the tool mass
increases, the kinetic energy increases, the impact impulse increases and the cutting force
also increases. up, cutting power increases.
3.1.4. Investigate the influence of angular velocity of the steel disc fitted with the cutter
to the cutting power - earth pulling
The influence of angular velocity on the cutting power - pulling the ground is shown
in Figure 3.4.

12

Figure 3.4: Effect of angular velocity on shearing power - ground pulling
3.2. Vibration survey of earth cutting system
3.2.1. Determining the input parameters to investigate the system's vibration
The differential equation for the vibration of the earth shear system is set up according
to (2.49).
The input parameters for machine vibration survey according to (2.49) are as
follows:
C1y - The stiffness in the vertical y direction of the system, calculated according to
the technical documentation of the machine, we have: : C1y= 200N.m;
C2y- The stiffness of the spring in the vertical direction of the system according to
the technical documentation of our machine has C2y= 50N.m;
R - Radius of steel disc fitted with earth cutter, R = 0.08 (m);
L - Length of the tool, L = 0,07 (m);
md - Weight of cutter, m1 = 50 g;
ω - Angular speed of the steel disc shaft = 125 rad/s;
L1= 13cm , a=10cm , L3=17cm , L2= 27cm
Weight of whole machine Mm = 9.5kG
n - Number of revolutions of steel disc with cutter n = 1,200 (v/p).
The excitation force causing vibration is calculated according to the formula (2.63),
=the excitation form according to the rules in Figure 2.9, during the investigation of the
excitation force taken at a certain value.
3.2.2. Investigate the influence of the angular velocity of the steel disc fitted with the
cutter on the vibration acceleration of the machine
The thesis conducts a survey with the input parameter when changing the angular velocity
of the steel disc fitted with the cutter ɷ1 = 125 rad/s , ɷ2 = 165rad/s, ɷ3 = 205rad/s, the
survey results are shown in Figure 3.6; 3.7; 3.8.

13

Figure 3.6: Vibration acceleration of machine corresponding to ɷ1= 125 rad/s

Figure 3.7: Vibration acceleration of machine corresponding to ɷ2= 165rad/s

Figure 3.8: Vibration acceleration of machine corresponding to ɷ3= 205rad/s
From The survey results obtained in the thesis make the following comments:
- The vibration acceleration of the earth shear system has a cyclic form, depending on the
angular velocity of the steel plate fitted with the earth cutter.
- Vibration acceleration is greater than the allowable vibration acceleration of the
machine, this vibration acceleration affects the structure and durability of the details in the

14


earth cutting system, and at the same time affects the vibration of the machine.
3.2.3. Investigate the influence of the stiffness of the vibration damping spring C1 on
the vibration acceleration of the machine
The thesis conducts a survey when changing the input of the simulation program with
the change of the stiffness of the vibration reducing spring C1 = 200 N/m; C1 =300 N/m;
C1=400N/m, C2 takes the fixed value C2 = 50 N/m, the simulation results are graphed in
Figure 3.9; 3.10; 3.11.

Figure 3.9: Vibration acceleration of earth shear system corresponding to
damping spring stiffness C1 = 200N/m

Figure 3.10: Vibration acceleration of earth shear system corresponding to
damping spring stiffness C1 = 300N/m

Figure 3.11: Vibration acceleration of the ground shear system corresponding to the

damping spring stiffness C1 = 400N/m

15


From the obtained survey results, the following observations are made:
The vibration acceleration of the machine depends on the stiffness of the furnace. The damping
spring is the link between the machine and the handle, when the stiffness of the spring C1 =
300N/m, the vibration acceleration is the smallest, this survey result is the scientific basis for
providing an anti-vibration solution for the machine. earth cutting system.
3.3. Investigate parameters affecting speed and pressure of exhaust fans and soil
spraying
3.3.1. Investigate the influence of the outlet assembly angle on the speed of the exhaust
fan and ground spray
To find the rule of influence of the output assembly angle β2 on the speed of the exhaust
fan, the thesis investigates Equation (2.73). Survey method using software software
Matlab - Simulink, input parameters for the survey include: r1 = 10cm; r2 = 4cm, survey
results are shown in Figure 3.12.

Figure 3.12: Effect of angle β2 on the velocity of the exhaust fan and ground spray
Comment: The influence of the outlet assembly angle of the exhaust fan is nonlinear,
with the output assembly angle β2 = 100-125 degrees, the operation will The absolute
speed of the output air is the largest, the results of this survey are the basis for
determining the reasonable parameters of the angle β2 when designing and manufacturing
exhaust fans and spraying soil to fight forest fires.
3.3.2. Investigate the influence of outlet assembly angle on the spray pressure of the
exhaust fan
To determine the influence of angle β2 on the pressure of the exhaust fan and soil
spray, the thesis investigates the formula (2.76). Survey method using software software
Matlab - Simulink, input parameters for the survey include: r1 = 10cm; r2 = 4cm,, survey

results are shown in Figure 3.13.

16


Figure 3.13: Influence of angle β2 on exhaust fan pressure, soil spray
From the survey results obtained, the thesis has the following comments:
- The influence of outlet assembly angle on exhaust fan pressure is nonlinear. , when the
outlet assembly angle β2 changes from 100 - 125 degrees, the suction and injection
pressure is the largest.
- The above survey results are the scientific basis for choosing reasonable parameters of
the output assembly angle when calculating the design and manufacturing of exhaust fans,
spraying ground to fight forest fires.
Chapter 4
EXPERIMENTAL RESEARCH TO VERIFY THEORY AND DETERMINATE
SOME OPTIMIZED PARAMETERS OF SAND LAND FOREST FIRE
EXTINGUISHERS
4.1. Objectives and tasks of experimental research
4.1.1. Objectives of the experimental study
Determine the influence of some parameters of the soil cutting system on the cutting
capacity - soil pulling, the vibration of the excavator, the influence of the pressure exhaust
fan parameters on the amount of soil sprayed. and the pressure of the soil sprayed on the
fire, thereby verifying the theoretical calculation model established in Chapter 2 and
solving the optimization problem to determine some optimal parameters of the sandy soil
forest fire fighting machine.
4.1.2. Research tasks
In order to achieve the research objectives on experimental research, the following
tasks must be performed:
- Determine the cutting capacity - soil pulling, vibration of earth breakers;
- Determination of air flow velocity and pressure of exhaust and spray fans;

- Determine the influence of the steel disc diameter of the soil cutting system on the
volume and pressure of the sprayed soil;
- Determine the effect of the cutter length on the mass and pressure of the sprayed soil;
- Determine the effect of the outlet mounting angle β2 of the blower on the mass and
pressure of the sprayed earth;
- Determine the effect of the number of high-pressure blades on the mass and pressure of
the sprayed soil.
- From the results of experimental research, the thesis has established a regression

17


function, using the multi-objective optimization problem-solving method to determine the
values of some optimal parameters of the sandy soil forest fire fighting machine.
4.2. Experimental research objects and equipment
The object of experimental research is a forest fire fighting machine made of sand,
designed and manufactured by the state-level key project code KC07.13/60-10 and
manufactured and commercially by Vietnam Specialized Equipment Joint Stock
Company. commercialization. Experimental research equipment is shown in figure 4.1.

Figure 4.1: Experimental research equipment
4.3. Organization and conduct of experiments
4.3.1. Measuring torque on shaft mounted with steel discs
The experiments to measure axial torque on shafts fitted with steel discs were carried out
in the experimental forest of the Forestry University with the following parameters:
- Experimental soil: Natural soil In the forest, the soil type is sandy soil mixed with
gravel, split trees, soil moisture 30%, soil compaction 15kg/cm2.
- Experimental equipment: Weight of cutter m = 50g, radius of steel disc R0 changes as
follows: R0 = 6cm; R0 = 7cm; R0 = 8cm; R0 = 9cm; R0 = 10cm, the length of the cutter
takes a fixed value: l = 7cm, the number of revolutions of the shaft with the earth cutter n

= 1500 rpm. The experimental process is shown in figure 4.11.

Figure 4.11: Experimental measuring moment, vibration acceleration of earth shear

18


system

Figure 4.12: Torque diagram of steel disc shaft fitted with cutter against cutting time
4.3.2. Measuring the vibration acceleration of the earth cutter
Simultaneously with measuring the torque on the shaft mounted with the steel disc, the
thesis measures the vibration acceleration of the machine. To ensure the reliability of the
experimental data is 95%, according to the data of the initial exploratory experiment, the
number of repetitions for each experiment is determined to be 3. The experimental
process is by statistical method. mathematically, the input parameters change at different
values in the ascending direction. The experimental results are processed by Tcwin and
Catman software, Figure 4.13 is the graph of the vibration acceleration of the earth shear
system.

Figure 4.13: Vibration acceleration chart of earth shear system
4.4. Verifying theoretical computational model
4.4.1. Verifying the calculation model of earth shear-swing power
To compare the results calculated according to the theory with the experiment, in table
4.1, the results calculated according to the theory are presented with the quantities
determined by experiment (the parameters of the testing process have the same value). with
parameters calculated according to the theoretical model). The results of calculating the
shear-stretch power by theory and by experiment are recorded in comparative table 4.1.
Table 4.1. Compare the theoretically calculated soil shear force
with experimental results

19


Radius of steel
plate (cm)
6
7
8
9
10

Cutting capacity - earth pulling (KW)
Theory
Experiment
Error (%)
2,46
2,72
9,6
2,75
3,02
8,9
2,93
3,22
9,0
3,37
3,66
7,9
3,93
4,31

8,8

From the results in Table 4.1, the following observations are made:
- The difference between the experimental results of determining the shear - pulling
power in the ground compared with the theoretical calculation is within the allowable and
acceptable range, so the calculation model The ground breaking power calculation is
theoretically reliable. There is a discrepancy between the experimental results and the
theory because in the experimental process the influencing factors interact with each
other, but this effect has not been included in the theoretical research.
4.4.2. Verification of the vibration calculation model of the earth breaker
The thesis has determined the vibration acceleration of the earth cutter when changing
the radius of the steel disc fitted with the earth cutter, the results are obtained in the form
of a graph (Figure 4.13) using the software DMC-Plus, Catman to determine determine
the maximum vibration acceleration corresponding to the radii of the steel disc fitted with
different cutters. To evaluate the reliability of the theoretical model to calculate the
vibration of the ground shear system, the thesis compares the calculated results according
to the theoretical model with the experimental results in Table 4.2.
Table 4.2. The table compares the maximum vibration acceleration of the earth
shear system between the theoretical calculation model and the experimental results.
Radius of
Maximum vibration
Maximum vibration
Error (%)
steel disc
acceleration calculated
acceleration
fitted with
according to
experimentally
earth cutters theoretical simulation

determined (m/s2)
(cm)
(m/s2)
6
6,2
6,8
8,82
8
8,5
9,3
8,60
10
10,2
11,3
9,73
Comments: From the results of Table 4.2, the following comments are made:
- Graph of vibration acceleration of the ground shear system between theory and reality
The experiment is similar, in accordance with the law of change of the excitation force
caused by the earth shear impulse.
- The maximum vibration acceleration of the earth shear system is variable with the radius

20


of the steel disc fitted with the earth cutter, when the radius of the steel disc increases, the
impact impulse increases, the shear force increases, thereby accelerating the vibration.
movement increases.
- The error between the vibration acceleration of the earth shear system, calculated
according to the theoretical simulation results and the experimental results is within the
allowable range, so the vibration calculation model of the circuit breaker The land

established in chapter 2 is reliable.
4.5. Determining some optimal parameters of a forest fire fighting machine with
sandy soil
4.5.1. Choose a research method
The experimental planning method is the theoretical basis of modern experimental
research which has many advantages, in which Mathematical tools play an active role.
The mathematical basis of the experimental planning theory is statistical mathematics
with two important fields: analysis of variance and analysis of regression. The content of
the experimental planning method is presented in the documents [6]; [13]. Below, this
method is only applied to specific problems.
4.5.2. Choose the research objective function
There are many criteria to evaluate the quality and effectiveness of fire extinguishing
machines, in the thesis choose two important objective functions that are mass function of
soil sprayed on fire, symbol Q unit (kg/min) and objective function. Target the pressure of
the earth sprayed on the fire, symbol P unit (N).
4.5.3. Choose parameters that affect the objective function
Through the above analysis, according to the experimental planning method, the thesis
selects 4 main factors that have the greatest influence on the volume and pressure of the
earth sprayed on the fire for research, which are: Diameter of steel disc symbol is D, unit
(cm); cutter length, symbol L, unit (cm); outlet mounting angle of single β2 symbol highpressure airfoil (degrees); the number of blades of the blower is denoted by Z. The range
of variation of these parameters is determined from technical conditions, from research
results in chapter 2 and survey results in chapter 3.
4.5.3. Multifactorial experimental results
The single-factor experimental results show us that the influence of each parameter on
the objective function is mainly nonlinear, the thesis does not conduct first-order
experimental planning, but does second-order experimental planning, steps Multifactorial
experiment was conducted as follows:
4.5.3.1. Select the study area and variable values of input parameters
From the single-factor experimental results, we choose the variable domain of input
parameters as follows:

Experimental level and coding value of input parameters recorded in table 4.11.

21


Table 4.11. Test level of input parameters
value
Input
Levels
X1
X2
X3
X4
β2(d
D(
L(
Z
egrees)
cm)
cm)
Upper level
1
18
8
105
20
Base level
0
15
6

100
18
Lower level
-1
12
4
95
16
Range
1
3
2
5
2
4.5.3.2. Building the empirical matrix
According to 13, we have chosen the experimental matrix according to the Boks - Benken
plan in the hypersphere domain with four input parameters and presented in Table 4.12.
Table 4.12. Boks - Benken
TT
X1
X2
X3
X4
TT
X1
X2
X3
X4
1
-1

-1
0
0
15
-1
0
0
+1
2
+1
-1
0
0
16
+1
0
0
+1
3
-1
+1
0
0
17
0
-1
0
-1
4
+1

+1
0
0
18
0
+1
0
-1
5
-1
0
-1
0
19
0
-1
0
+1
6
+1
0
-1
0
20
0
+1
0
+1
7
-1

0
+1
0
21
0
0
-1
-1
8
1
0
+1
0
22
0
0
+1
-1
9
0
-1
-1
0
23
0
0
-1
+1
10
0

+1
-1
0
24
0
0
+1
+1
11
0
-1
+1
0
25
0
0
0
0
12
0
+1
+1
0
26
0
0
0
0
13
-1

0
0
-1
27
0
0
0
0
14
+1
0
0
-1
4.5.3.3. Results of multifactorial experiment
a) Effect of parameters on mass function of sprayed soil
Using software and program to process experimental data, after calculating the
following results:
- Regression model real form:
Q = -77.50431 + 0.824404D + 0.435675 L + 1.152349β + 1.569497Z - 0.002198DL +
0.001092 Dβ + 0.003233 DZ + 0.0015 Lβ -0.001875 LZ -0.000333βZ-0.032459D20.041736L2-0.005828β2-0.043611Z2
(4.25)
b) Effect of parameters on injection pressure function

22


Using software and program to process experimental data. After calculating the following
results:
- Real form regression model:
P = -629.052443 + 7.556757D + 8.538937L + 8.667088 β + 14.106034Z 0.108046DL - 0.034138Dβ -0.034626DZ- 0.053333Lβ - 0.010417LZ -0.066667βZ 0.099942D2- 0.122222L2 - 0.032889β2-0.179514Z2 (4.28)

4.5.4. Determining the optimal value of the influencing parameter
The purpose of the problem is to find the values of D; L; β2, Z so that the mass
function and the soil pressure are the largest, this is a multi-objective optimization
problem. To solve this problem, it is necessary to choose and develop a solution method.
- Determine the maximum value of each objective function: By domain meshing method
[D (12,18); L(4,8) ; β(95,105); Z(16,20)], computes the value of the function at the grid
nodes and compares them to find the maximum value. By meshing the survey domain into
104 points, the extreme values of the functions have been determined as follows:
Domain Mesh [D (12,18);L(4,8) ; β(95,105); Z(16,20)] to 104 points, calculate the
value of the function at the grid nodes and compare them to find the largest value equal to
: 1.9872 at the values : D = 15 ; L = 6 ; β2 = 100 ; Z = 18.4.
Because the number of propellers must be a natural number, compare the value of the
function  at two points:
D = 15; L = 6 ; β2 = 100 ; Z = 18 has  = 1.9830
and D = 15 ; L = 6 ; β2 = 100 ; Z = 19 has  = 1.9757
Thus, the optimal values of some parameters of the sandy soil forest fire fighting machine
are:
- Diameter of steel disc D = 15 cm; Cutter length L = 6 cm;
- The outlet assembly angle of the blower β = 100 degrees; The number of blades of the
high-pressure blower Z = 18 blades. The above parameters are the scientific
basis for perfecting the forest fire fighting machine with sandy soil.
CONCLUSIONS AND RECOMMENDATIONS
1. Conclusion
After obtaining the research results, the thesis draws the following conclusions:
1. The sand-based forest fire fighting machine is a product that has been granted a
solution patent by the National Office of Intellectual Property of Vietnam. The machine
has been used to fight forest fires in many localities for its high efficiency in fighting
forest fires. However, the machine still has some limitations that need to be further
improved to improve the effectiveness of forest fire fighting.
2. The thesis has built the model, the equation for calculating the earth shear force in

the form of hammer, the power of shearing-swinging of the ground, has conducted a

23