1. Mục đích và đối tượng nghiên cứu của luận án Mục đích của luận án: Xây dựng cơ sở khoa học để phục vụ cho việc tính toán xác định giá trị tối ưu một số thông số của máy chữa cháy rừng bằng đất cát nhằm nâng cao khối lượng và áp lực đất phun vào đám cháy, giảm rung động của máy, từ đó nâng cao hiệu quả dập lửa chữa cháy rừng Đối tượng nghiên cứu: Đối tượng nghiên cứu là máy chữa cháy bằng đất cát 2. Các phương pháp nghiên cứu đã sử dụng Luận án sử dụng phương pháp nghiên cứu lý thuyết kết hợp với thực nghiệm. * Phương pháp nghiên cứu lý thuyết - Luân án sử dụng lý thuyết cơ học, lý thuyết mô hình hóa, lý thuyết cắt đất ở dạng búa để xây dựng mô hình và thiết lập phương trình động lực học, sử dụng các phần mềm chuyên dùng để khảo sát các yếu tố ảnh hưởng đến các chỉ tiêu đánh giá. * Phương pháp nghiên cứu thực nghiệm - Sử dụng phương pháp đo lường các đại lượng không điện bằng điện để đo một số thông số độc lực học của máy chữa cháy rừng bằng đất cát - Sử dụng phương pháp qui hoạch thục nghiệm đơn yếu tố và đa yếu tố để thiết lập hàm hồi qui, sử dụng phương pháp giải bài toán tối ưu đa mục tiêu để xác định một số thông số hợp lý của máy chữa cháy rừng bằng đất cát. 3. Kết quả chính và kết luận 1. Luận án đã xây dựng được mô hình, phương trình tính toán lực cắt đất ở dạng búa, công suất cắt- kéo văng đất, đã tiến hành khảo sát một số thông số ảnh hưởng đến công cắt -kéo văng đất, từ đó đã xác định được chiều dài dao cắt, bán kính đĩa thép lắp dao cắt đất, trọng lượng dao cắt, công suất động cơ của máy cắt đất. Kết quả tính toán này đã sử dụng cho hoàn thiện hệ thống cắt đất dạng búa. 2. Luận án đã xây dựng được mô hình, hệ phương trình vi phân rung động của máy cắt đất, đã khảo sát hệ phương trình vi phân dao động, kết quả khảo sát cho thấy rung động của máy vượt quá giới hạn cho phép, đã đề xuất giải pháp giảm rung động của máy cắt đất. 3. Đã xây dựng mô hình tính toán quạt hút và phun đất vào đám cháy, đã khảo sát yếu tố ảnh hưởng đến áp lực và vận tốc của quạt hút, từ kết quả khảo sát đã xác định được góc lắp ráp đầu ra β2 hợp lý của quạt hút và phun đất, đã tính toán được vận tốc cần thiết của không khí trong ống hút, công suất động cơ quạt hút và phun đất. Kết quả tính toán đã sử dụng để hoàn thiện hệ thống hút và phun đất. 4. Luận án đã xây dựng được phương pháp thực nghiệm xác định một số thông số tối ưu của máy chữa cháy rừng bằng đất cát, kết quả nghiên cứu thực nghiệm đã lập được hàm hồi qui thực nghiệm (4.25); (4.28) ảnh hưởng của đường kính đĩa thép lắp dao cắt (D), chiều dài dao cắt (L), góc lắp ráp đầu ra (β2), số cánh của quạt gió (Z) đến hàm mục tiêu là khối lượng và áp lực đất phun vào đám cháy. Sử dụng phương pháp giải bài toán tối ưu đa mục tiêu, luận án đã xác định được một số thông số tối ưu của máy đó là: Đường kính đĩa thép D= 15cm; chiều dài dao cắt đất L = 6 cm; góc lắp ráp đầu ra của quạt gió β2 = 100 độ; số cánh của quạt hút, phun đất Z =18 cánh, với thông số tối ưu này khối lượng và áp lực đất phun vào đám cháy là lớn nhất. 4. Ý nghĩa khoa học của những kết quả nghiên cứu của đề tài luận án Luận án đã xây dựng được phương pháp luận nghiên cứu về máy chữa cháy rừng bằng đất cát. Kết quả nghiên cứu này là cơ sở khoa học cho việc tính toán thiết kế chế tạo và hoàn thiện máy chữa cháy rừng bằng đất cát 5. Ý nghĩa thực tiễn của đề tài luận án Kết quả nghiên cứu của luận án đã được sử dụng cho việc thiết kế chế tạo và hoàn thiện máy chữa cháy rừng bằng đất cát, ngoài ra còn sử dụng để làm tài liệu tham khảo cho việc tính toán thiết kế hệ thống cắt đất dạng búa.
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 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" 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 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 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 = 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 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 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 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 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 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 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 Gasoline saw engine; Belt transmission; Steel disc for mounting the cutter; Knife mounting bolts; Knife to cut the ground; 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 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 = 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) where is the angular velocity of the disc Call the point N(x,y) on the segment OiA 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 iRcosi i cos i (2.3) Kinetic energy of rod segment OiA L (iRcosi i cos i ) iR sin i i sin i (x y ) TOiA d d 2 0 L TOi A L 2 L3 L2 R i i Ri i.cos i i (2.4) The potential energy of the hammer OiA U Oi A g Oi A L xd g Rcosi cos i d (2.5) L2 UOi A g L.Rcosi cosi 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) × (2.6) t1 The soil breaking force is calculated according to the following formula: 2h Pc gh (2.18) b, Calculate the earth shear and earth splash angular momentum of the cutte Ph L3 RL2 J1 R L. i 2 i cos( i ) c i 1 Skv m G b L3 2 J + m b L.R RL co s ( ) G i i 1 (2.30) c) Work produced by the earth shear - pulling momentum (average): Ac-v A c kv Pch L3 RL2 J R L cos( ) i i i 2m G b 2 i 1 Pc bt b 2h L 2 J1 + m G b L.R RL cos( i ) i 1 2.2.2 Calculate the power to cut – pull the ground N c kv Ac kv t Ph L3 RL2 J R L 2 i cos( i ) c i 2mGb i 1 b Pc b 2h L 2 J1 + mG b L.R RL cos( i ) 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 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 𝑆𝑖𝑛𝛽2 𝐶𝑜𝑠𝛼 𝑔.𝑆𝑖𝑛(𝛼+𝛽2 ) 𝜂 𝑘 (2.76) Chapter 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 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 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 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) 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) 6,2 6,8 8,82 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 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 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 and survey results in chapter 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 18 105 20 Base level 15 100 18 Lower level -1 12 95 16 Range 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 0 15 -1 0 +1 +1 -1 0 16 +1 0 +1 -1 +1 0 17 -1 -1 +1 +1 0 18 +1 -1 -1 -1 19 -1 +1 +1 -1 20 +1 +1 -1 +1 21 0 -1 -1 +1 22 0 +1 -1 -1 -1 23 0 -1 +1 10 +1 -1 24 0 +1 +1 11 -1 +1 25 0 0 12 +1 +1 26 0 0 13 -1 0 -1 27 0 0 14 +1 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 = ; 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 = ; β2 = 100 ; Z = 18 has = 1.9830 and D = 15 ; L = ; 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 = 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 Conclusion After obtaining the research results, the thesis draws the following conclusions: 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 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 survey of some parameters affecting the shear-stretch work, from that determined the cutter length, the radius of the steel disc fitted with the earth cutter, the weight of the cutter, and the motor power of the earth cutter This calculation result was used to complete the hammer earth cutting system The thesis has built a model, the system of differential equations for the vibration of the earth cutter, has investigated the system of differential equations of oscillation, the survey results show that the vibration of the machine exceeds the allowable limit , proposed a solution to reduce the vibration of earth breakers Built a model to calculate the exhaust fan and spray soil on the fire, investigated the factors affecting the pressure and speed of the exhaust fan, from the survey results, the outlet assembly angle β2 was determined The rationality of the suction fan and soil spray, the necessary velocity of the air in the suction pipe, the power of the suction fan and the soil sprayer motor has been calculated Calculation results were used to complete the soil suction and spray system The thesis has built an experimental method to determine some optimal parameters of the forest fire fighting machine with sandy soil, experimental research results have established an experimental regression function (4.25); (4.28) the influence of the cutter disc diameter (D), cutter length (L), outlet assembly angle (β2), blower blade number (Z) on the objective function of mass and earth pressure sprayed on the fire Using the multiobjective optimization problem-solving method, the thesis has determined some optimal parameters of the machine: Diameter of steel disc D= 15cm; soil cutter length L = cm; outlet assembly angle of blower β2 = 100 degrees; the number of blades of the suction fan, which sprays the ground Z = 18 blades, with this optimal parameter, the volume and pressure of the soil sprayed on the fire is the largest The research results of the thesis have been used to perfect the forest fire fighting machine with sand in the state-level project: “Support to commercialize the technology of manufacturing some specialized fire fighting equipment forest of Vietnamese brands", thereby overcoming the limitations of the old machine and improving the fire extinguishing efficiency of the device Recommendations Due to the limited research time, in order to improve the topic, it is necessary to continue to study some of the following issues: According to the operating principle of the machine, the soil is sucked in by the fan and sprayed on the fire, so in the process of moving a the impact of the ground with the propeller, the study of the influence of the impact force of the soil on the vibration of the suction and sprayer as well as the power of the machine also needs to be further studied to improve the suction and spray earth on the fire 24 LIST OF PUBLICIZED ARTICLES, SCIENTIFIC WORKS RELATED TO THE THESIS Year of publication 2018 2021 2021 Name of the scientific article Study on the dynamics of the soil cutting system of a sand-based forest fire fighting machine Study on the Vibrations of a sand- based forest fire fighting machine Determination of some optimal parameters of a sand- based forest fire fighting machine 25 Author/Co -author Journal of Co-author Forestry Science and Technology Journal of Co-author Forestry Science and Technology Journal of Co-author Forestry Science and Technology Journal name