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

HỘI NGHỊ KHCN TỒN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM 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 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, nonexplosive 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 An amphibious excavator with cutterhead for dredging task Interaction between cutterhead and coral 2.1.Calculating the resisting force and driving torque Trang 359 HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM 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 va  2 Rn sin sin  60 sin     (4) 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 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: h i  h max sin  cos  vs 60  h max  np  Figure The cutting process of a cutterhead (1) According to [2] the sum of average resisting force is calculated by summing local resisting force apply on the cutting head: The projected width of a blade on the axis of the cutterhead is: p Fct  2 bpr  bcos  cos When the swing velocity is neglected, the cutting velocity can be simplified to:  vc  vciR cos   2 Rn  vciR  60 (2) 2 Rn sin vt  60 (3) Trang 360 0  F d c (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 HỘI NGHỊ KHCN TỒN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM 1  1  Fst  cnc g1  sin  cos d  g  sin d    0     cca g  sin  cos d  g  sin d  1  1  (6) g1  c1.cos t.cos  ; (12) g  c1.sin t.sin  cos   c2 cos  ; g3  d1 ; + The sum of resisting force in v-direction 1  1  Fvt  c nc g1  sin d  g  sin  cos d    0 0   cca  g  sin d  g  sin d    1 1 (7) + The sum of resisting force in axial direction g  d1.tan t.sin   d cos  cos t ; g5  c1.sin t.cos2   c2 sin  cos  ; g  d1.tan t.cos   d sin  ; cos t t - Angle of blades with axis cutterhead [rad]; 1 0 R- Radius of cutting head, [m]; 1 vs - Fat  cncg  sin d  cca g  sin d (8) The velocity of cutting head in h-direction, [m/s]; + Driving torque 1 0 1 n- The rotational speed of cutting head, [rpm]; M t  cncg1R  sin d  cca g 3R  sin d (9) 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]; In Which: The coefficients cnc and cca, which have the dimension of force (kN), can be calculated by the following equations: p e cnc   w g.bpr vciR h i2max 2 km (10) p  w g.bpr (z  10).h i max 2 (11) cca   w - Water specific gravity, [kg/m3]; ca Cavitating cutting proces; v c - The long velocity of cutting teeth, [m/s]; h m - The maximum cutting thickness, [m]; h i - The cutting thickness, [m]; 1 - The angle occurs cavitation, [rad]; c1;c2 - Cutting coefficient; nc Non-cavitating cutting proces; d1;d - Resisting force coefficient bpr = bv⋅cos ι⋅cosξ 2.2.Calculating the pressure of the hydraulic driving motor 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]; Hydraulic motor drive the cutting head through a mechanic transmission The torque of hydraulic driving motor generate must satisfy following conditions: T i.i  M (13) g Gravitational constant (9.81), [m/s²]; km Average permeability, [m/s]; z Water depth, [m]; e Volume strain, [%]; 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: Trang 361 HỘI NGHỊ KHCN TOÀN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM T pqmm 20 (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: pqmmii M 20 (15) From (9) and (15) we have: p 1 0 1 20 (cgc g1R  sin d  cca g3 R  sin d) mi iqm 3.2 The effect of the rotational rate, n (16) Discussion on the relative influence of working regime Running Text We used the researching data on the coral foundation [6] and [2] Tab Input parameters c1 c2 d1 d2 ρw g 0.291 0.202 2.303 1.424 1000 9.81 α β φ δ n p 30o 33.636o 37o 21o 80 10 b z vs ι ξ R 0.2 0.6 0.2 30 o 30 o Figure The effect of cutting depth on the oil pressure 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 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, Vs 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 3.1 The effect of the cutting depth, bv 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 Trang 362 Figure The effect of rotational speed on the oil pressure HỘI NGHỊ KHCN TỒN QUỐC VỀ CƠ KHÍ - ĐỘNG LỰC NĂM 2017 Ngày 14 tháng 10 năm 2017 Trường ĐH Bách Khoa – ĐHQG TP HCM 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 Figure The effect of the cutting head feed velocity on oil pressure Conclusions This paper presents the method for defining the cutting force, driving moment and working pressure in the hydraulic motor used for a cutterhead for the task of dredging Additionally, we investigate the influence of working parameters of this cutter-head on the hydraulic pressure for different levels of hydraulic displacement, q m 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 [4] W Vlasblom, Dredging equipment and technology Chap3: The cutter suction dredger, 2003, vol [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/hydraulicmotor-formulas-metric-units ẢNH HƯỞNG CỦA CHẾ ĐỘ LÀM VIỆC ĐẾN ÁP SUẤT VÀ LƯU LƯỢNG TRONG MÔ TƠ DẪN ĐỘNG ĐẦU CẮT PHÁ SAN HÔ TÓM TỦA Để tránh tác hại xấu thuốc nổ đến môi trường, số nước phát triển giới chế tạo nhiều loại thiết bị phá đá không dùng lượng nổ Các thiết bị cho phép thi công khu vực nhạy cảm không gây tiếng nổ như: búa đập thủy lực, ngàm kẹp thủy lực, máy xung điện thủy động, đầu cắt phá đá, Bài báo xây dựng sở lý thuyết, mơ hình tương tác đầu cắt với đá từ xác định thành phần lực cản cắt mô men dẫn động đầu cắt Kết nghiên cứu sử dụng làm tài liệu tham khảo để thiết kế, chế tạo lựa chọn tổ hợp thiết bị thi công mở luồng không nổ Từ khóa: đầu cắt san hơ, áp suất, lưu lượng, lực, mô men Trang 363 ... 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... cca g 3R  sin d (9) 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... 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,