Analysis and design of an axial piston water-pump with piston valve.pdf
资源目录
压缩包内文档预览：
编号：122561708
类型：共享资源
大小：2.34MB
格式：ZIP
上传时间：2021-04-20
上传人：221589****qq.com
认证信息
个人认证
李**（实名认证）
湖南
IP属地：湖南
40
积分
- 关 键 词：
-
煤矿
排水
设备
选型
设计
水泵
故障
分析
- 资源描述：
-
煤矿排水设备选型设计及水泵故障分析,煤矿,排水,设备,选型,设计,水泵,故障,分析
- 内容简介：
-
Journal of Mechanical Science and Technology 25 (2) (2011) 371378 /content/1738-494x DOI 10.1007/s12206-010-1214-6 Analysis and design of an axial piston water-pump with piston valve Luo Xiaohui*, Niu Zihua, Shi Zhaocun and Hu Junhua School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074, Peoples Republic of China (Manuscript Received May 3, 2010; Revised July 19, 2010; Accepted November 11, 2010) - Abstract In this paper, we present a novel axial piston water-pump with piston valve, which carries out the flow distribution to drain and sucks water by the interaction of each piston. This novel water-pump could achieve change in-phase between flow rate and the passage areas of the intake and outlet ports. In order to completely achieve the in-phase change, the pressure that is assigned a fixed value in the piston chamber is optimized. On these grounds, the optimum shapes of the intake and outlet ports have been found to be rectangular according to theoretical analysis. The simulation results indicated that the optimum intake and outlet port shapes keeps the pressure in the piston chamber constant, and there is almost no pressure surge except for a very small pressure wave in the piston chamber. Finally, the test of model machine showed that the pressures of the intake and outlet port are very steady, but the leakage is large and the volumetric effi-ciency is 74.7%. Keywords: Axial piston water-pump; Optimum design; Piston valve; Pressure surge - 1. Introduction Because water hydraulics have the merits of excellent safety characteristics, environmental protection, economization, easy maintenance and steady performance, they are being applied widely in many industrial fields, such as metallurgical, chemi-cal plants, food machinery, medical machinery, grain machin-ery and packaging machinery 1-5. As we know, the key to the development of water hydraulic technology is to develop water hydraulic components. As a power supply in water hy-draulic systems, the water hydraulic pumps development is the most crucial and difficult. Owing to the low viscosity of water, the phenomenon of ab-rasion and leakage occur more easily in water hydraulic pumps than that in oil hydraulic pumps. Traditional oil hy-draulic systems use several main structural forms, such as gear pumps, vane pumps and piston pumps. Because the axial pis-ton pump has good wear resistance, little leakage, compact structure, high output pressure, high efficiency and long ser-vice life, most water hydraulic pumps at the present adopt the structure form of an axial piston. Since the 1970s, some researchers have carried out studies for water hydraulic pumps, which were almost axial piston pumps with valve-plates or flat valves 6-10. For water-pumps with valve-plates, the abrasion phenomenon is severe and the making material is strictly required because water is used as the lubricating medium between the cylinder body and valve-plate. In pumps with flat valves, large pressure surges are frequent because of the motion incoordination between the flat valve and piston. Impact noise is also produced when a flat valve is opened and closed. Thus, a novel axial piston water-pump with a piston valve to counter the shortcomings discussed above will be designed in this paper. 2. Working principle of axial piston water-pump with piston valve Fig. 1 shows an axial piston water-pump with piston valve (the number of the piston is 8). From Fig. 1, we know that each piston chamber is connected with the valve chamber leading 90, and its own valve chamber is connected with the piston chamber delaying 90 through the valve groove on the valve plate. The valve principle of the water-pump draining and sucking water is analyzed and shown in Fig. 2, and the detailed working process of an axial piston water-pump with piston valve is described as below: (a) The 1st piston is at the top pole. It is about to move to the left side, and the volume of the 1st piston chamber will de-crease continuously. The water in the 1st piston chamber be-gins to drain through the 3rd valve chamber, which is con-nected to the 1st piston chamber. At the same time, the 3rd pis- This paper was recommended for publication in revised form by Associate Editor Byeong Rog Shin *Corresponding author. Tel.: +86 27 87556055, Fax.: +86 27 87542202 E-mail address: KSME & Springer 2011 372 X. Luo et al. / Journal of Mechanical Science and Technology 25 (2) (2011) 371378 ton moves left to the mid-stroke, while part A of the 3rd piston closes the intake port and part B opens the outlet port. (b) The 2nd piston continues to drain water. The water in the 2nd piston chamber is drained through the 4th valve chamber, which is connected with the 2nd piston chamber. At this time, part A of the 4th piston has closed the intake port and the seal-ing length becomes longer and longer. Then, part B has opened the outlet port and the passage area becomes larger gradually. (c) The 3rd piston continues to drain water. The water in the 3rd piston chamber is drained through the 5th valve chamber, which is connected to the 3rd piston chamber. At this time, the 5th piston is at the bottom pole. Then, part A has completely closed the intake port and part B has completely opened the outlet port. (d) The 4th piston continues to drain water. The water in the 4th piston chamber is drained through the 6th valve chamber, which is connected to the 4th piston chamber. At this time, the 6th piston is moving to the right. Part A of the 6th piston continues to close the intake port, the sealing length becoming shorter and shorter, and part B begins to close the outlet port causing the passage area to gradually become smaller. (e) The 5th piston is at the bottom pole. It is about to move to the right side. The volume of the 5th piston chamber will increase continuously and a partial vacuum is generated in it. Subjected to the atmospheric pressure, water is sucked into the 5th piston chamber through the 7th valve chamber, which is connected to the 5th piston chamber. At the same time, the 7th piston is moving right to the mid-stroke, and part A of the 7th piston just opens the intake port as part B closes the outlet port. (f) The 6th piston continues to suck water. Water is sucked into the 6th piston chamber through the 8th valve chamber, which is connected to the 6th piston chamber. At this time, part A of the 8th piston has opened the intake port and the passage area gradually becomes larger, while part B has closed the outlet port and the sealing length becomes longer and longer. (g) The 7th piston continues to suck water. Water is sucked into the 7th piston chamber through the 1st valve chamber, which is connected to the 7th piston chamber. At this time, the 1st piston is at the top pole. Part A has completely opened the intake port and part B has completely closed the outlet port. (h) The 8th piston continues to suck water. Water is sucked into the 8th piston chamber through the 2nd valve chamber, Fig. 1. Structure of an axial piston water-pump with piston valve. Fig. 2. Structure of an axial piston water-pump with piston valve. X. Luo et al. / Journal of Mechanical Science and Technology 25 (2) (2011) 371378 373 which is connected to the 8th piston chamber. At this time, the intake port remains open in part A and the passage area gradu-ally becomes smaller, while the outlet port remains closed in part B, resulting in the sealing length becoming shorter and shorter. When the swash plate rotates in a circle, each piston will suck water and drain water once. According to the working principle discussed above, we can see that each piston can suck water and drain water with the help of two pistons spaced at 90. In addition, when two pis-tons are draining water, there must be another two pistons sucking water. Therefore, the number of pistons of an axial piston water-pump with a piston valve must be a multiple of four. Moreover, compared to a pump with a flat valve or valve-plate, one with a piston valve not only cuts down a friction pair in the structure and avoids impact noise of valve devices, but also could achieve the change in-phase relationship be-tween the flow rate and the passage areas of the intake and outlet ports, decreasing pressure surge and cavitation noise. Because of the fact that the passage areas depend on the shapes of the intake and outlet ports when working, it is nec-essary to carry out the optimum design work for the ports to achieve the complete change in-phase relationship between flow rate and the passage areas of the intake and outlet ports. 3. Optimum designs for the shapes of the intake port and outlet port In order to accomplish the goal of changing the in-phase re-lationship between flow rate and the passage areas of the in-take port and the outlet port, it is necessary to analyze the characteristics of pressure and flow in a single piston chamber. On this ground, the optimum shapes of the intake port and outlet port will be designed. Also, the 1st piston and the 3rd piston will be selected as subjects investigated for the conven-ient analysis as follows. 3.1 Design for shape of outlet port When the 1st piston is draining water, high pressure water in the 1st piston chamber is drained through the 3rd outlet port, as is shown in Fig. 3. In order to achieve the change in-phase relationship be-tween the flowrate of the draining water and the passage area of outlet port, the reduced water in the 1st piston chamber should be equal to the water discharged through the 3rd outlet port in an instantaneous state. So, the instant flow equation of draining water could be described as follows: 2p1sq312()4dppC av= (1) where Cq is the flow coefficient of the outlet port, a3 is the passage area of the 3rd outlet port, p1 is water pressure of the 1st piston chamber, ps is the pressure at outlet port, is the density of water, dp is the diameter of piston, and v1 is the ve-locity of the 1st piston. The water-pump discussed in this paper adopts the swash plate and ball-end rod as a power mechanism. According to Ref. 11, 12, if the time of piston 1st at the top pole is seen as zero time, the motion equations of the 1st piston could be ex-pressed as below: 1sin (1cos )sR= (2) 11dsin sindsvRt= (3) where s1 is the displacement of the 1st piston, R and are the radius and slope angle of the swash plate, respectively, is the rotation speed of pump, and is the rotation angle of swash plate and =t. When Eq. (3) is substituted into Eq. (1), the passage area a3 of the 3rd outlet port can be obtained as 2p3q1ssin sin42()R daCpp=. (4) Because the 3rd piston leads 90 to the 1st piston, the dis-placement equation of the 3rd piston should be 3sin 1cos()sin (1sin )2sRR=+=+ (5) where s3 is the displacement of the 3rd piston. According to the Eq. (4) and Eq. (5), the area gradient y3 of the 3rd outlet port is 2p333q1sdd42()daysCpp=. (6) Fig. 3. Process of draining water. 374 X. Luo et al. / Journal of Mechanical Science and Technology 25 (2) (2011) 371378 Therefore, the pressure p1 in the 1st piston chamber when draining water could be obtained as bellow by Eq. (6) 2p21s3q()32dppy C=+. (7) From Eq. (7), if the pressure p1 in the 1st piston chamber remains constant in order to avoid pressure fluctuation when draining water, the area gradient y3 should be a constant value because other parameters on the right-hand side of Eq. (7) are all constant values. Namely, the shape of the 3rd outlet port is rectangular (as shown in Fig. 3), and its length Ld3 is a half stroke described by maxd32sL= (8) where smax is the stroke of a piston. By Eq. (5), there is max3max( )2 sinssR=. (9) Furthermore, constrained by the structure size and structure strength, the value y3 should be 3psmin(,)ydL= (10) where Ls is the maximum width of the outlet port when meet-ing the structural strength. Thus, the optimal shape of the 3rd outlet port is a rectangle whose length and width is Ld3 and y3. 3.2 Design for shape of intake port Fig. 4 shows the process of sucking water by an interwork-ing of the 1st piston and the 3rd piston. As in actualizing the change in-phase relationship between flow rate of sucking water and the passage area of the intake port, there is a similar instant flow equation of sucking water described as follows: 2p01q312()4dppC av = (11) where Cq is the flow coefficient of the intake port, a3 is the passage area of the 3rd intake port, and p0 is the pressure at intake port. When Eq. (3) is substituted into Eq. (11), the a3 is 2p3q01sin sin42()R daCpp =. (12) According to Eq. (12) and Eq. (5), the area gradient y3 of the 3rd intake port is 2p333q01dd42()daysCpp =. (13) Based on Eq. (13), the pressure p1 in the 1st piston chamber when sucking water is as follows: 2p2103q()32dppy C= . (14) According to Eq. (14), we know that the pressure p1 in the 1st piston chamber when sucking water could remain constant if the area gradient y3 is a constant value. In other words, the optimal shape of the 3rd outlet port is a rectangular (as shown in Fig. 4), and its length Ld3 is a half stroke as maxd32sL =. (15) In addition, under the constraint of the structure size and structure strength, the value y3 should be 3psmin(,)ydL= (16) where Ls is the maximum width of intake port that meets the requirement of structural strength. According to the analysis above, the optimal shape of the 3rd intake port is also a rectangul whose length and width is Ld3 and y3. 3.3 Results of optimum design The optimal shapes of the outlet and intake ports designed above are based on the fact that the 1st piston and the 3rd piston are adopted as analysis objects. Because the other pistons have the same attributes with the 1st piston and the 3rd piston, the structure parameters of all outlet ports and intake ports should be identical, and they are Outlet portIntake port1st piston3rd pistonValve chamberv1v3Ay3a3 Shape of intake port View A (5:1) Ld3 Fig. 4. Process of sucking water. X. Luo et al. / Journal of Mechanical Science and Technology 25 (2) (2011) 371378 375 3dd33dd3yyLLyyLL= (17) where y and y are the area gradient of the outlet port and in-take port, respectively, and Ld and Ld are the length of the outlet port and intake port, respectively. 4. Simulation analysis for optimization results In order to show the effects of the optimal shapes of the out-let and intake ports, the pressure and flow rate of the 1st piston chamber will be examined by simulation analysis. 4.1 Characteristic equations of pressure and flowrate If the influences of geopotential, inertia force, velocity po-tential and leakage are ignored, the volume change of piston chamber, inflow and outflow of water are the main factors that cause pressure variation in the piston chamber. Then the pres-sure in the 1st piston chamber could be described as follows: 1111ddddpVqtVt=+ (18) where is the bulk modulus of elasticity of water, q1 is the flow rate of the 1st piston chamber from the 3rd valve chamber, and V1 is the volume of the 1st piston chamber as expressed below 22pp10max10sin()(1cos )44dRdVVssV=+=+ (19) where V0 is the clearance volume of a single piston chamber. If1ddt= and Eq. (19) are substituted into Eq. (18), there will be 2p112p0sindsinsind4(1cos )4RdpqRdV=+. (20) In addition, the flowrate q1 of the 1st piston chamber from the 3rd valve chamber is 1sq3101q32() 02() 2ppC aqppC a= (21) where the passage area a3 and a3 are shown as follows: max333() 020 2sy sa= (22) 3max330 0() 22asys =. (23) 4.2 Simulation analysis According to Eq. (18)-(23) and the structure parameters of the model machine shown in Table 1, the pressure and flow rate of the 1st piston chamber have been simulated. The simu-lation results are shown in Fig. 5 and Fig. 6. Fig. 5 shows the curves of the flow rate of the 1st piston chamber and the passage areas of the 3rd outlet and intake ports when the water-pump with piston valve is running. In Fig. 5, the flow rate of the 1st piston chamber and the passage areas of the 3rd outlet and intake ports are all smooth half-period sinusoids when the 1st piston chamber drains water (0) and sucks water (2), so they have the same change trend and reach the maximum and minimum values at Table 1. Model machine parameters. Parameters Value Parameters Value Parameters Value R (m) 0.084 smax (m) 0.071 Cq 0.7 (deg.) 25 ( N/m2) 2.4109 Cq 0.7 ( rad/s) 25 y (m) 0.020 p0 (Pa) 0.1106 V0 (m3) 1.710-4 y (m) 0.020 (kgm-3) 1000 dp (m) 0.036 ps (Pa) 3.5106 0p/2p3p/22p-3-2-10123Rotation angle of swashplate f /radFlowrate of the 1st piston chamberq1 /(m3/s)0810-464210-3Passage area of the 3rd outlet port and intake port a3, a3 /m2q1a3a3 Fig. 5. Curves of the flowrate of the 1st piston chamber, and the pas-sage area of the 3rd outlet port and intake port. Fig. 6. Curve of the 1st piston chamber pressure. 376 X. Luo et al. / Journal of Mechanical Science and Technology 25 (2) (2011) 371378 the same time. Fig. 6 shows the pressure curve of the 1st piston chamber. From Fig. 6, we know that the pressure curve presents two straight lines, namely, the pressure of the 1st piston chamber almost stays unchanged in the draining sucking stages. As a result, the vibration and noise generated by pressure surge are greatly lowered. At the time of the conversion between high pressure and low pressure (=0, ), the pressure impact is very small because the flow rate approaches zero (q10). Furher-more, on the stage of draining water (0), the pressure p1=3.52106 Pa and the pressure difference p1-ps=0.02106 Pa. On the stage of sucking water (2), the pressure p1=0.08106 Pa and the pressure difference p0-p1=0.02106 Pa. Just under the action of the pressure difference, the axial pis-ton water-pump with piston valve successfully carries out the work of draining water and sucking water. 5. Results of the experiments The pressures at the intake and outlet ports of the model machine, which is designed according to the parameters shown in Table 1, have been tested. The shapes of the intake and outlet ports are the same, as shown in Fig.7. The experi-ment table and results are shown in Fig. 8 and Figs. 9-11. Fig. 9 describes the pressures at the intake and outlet ports of the axial piston water-pump with piston valve. In Fig. 9, the pressure at the intake port almost keeps 0.1106 Pa. There are no pressure surges at the outlet port, but there are some sine trend pressure waves, which are generated by the sine trend flow waves under the action of the system impedance. Fig. 10 displays no-load (ps=0) flowrate under different ro-tation speeds. From Fig. 10, it could be seen that the no-load flowrate linearly increases with rotation speed. Thus, there is hardly any leakage in the pump when ps=0. Fig. 11 presents flowrate and volumetric efficiency with dif-ferent ps when rotation speed =25 rad/s. In Fig. 11, the curves of flowrate and volumetric efficiency are almost identi-cal because they both express the capability of sucking water. Fig. 7. Shapes of intake port and outlet port. Pressure sensor for intake portPressure sensor for outlet port Fig. 8. Experiment table. Fig. 9. Pressure in the outlet port and intake port. Fig. 10. No-load flowrate with different rotation speed. Fig. 11. Flowrate and volumetric efficiency with different pressure at outlet port. X. Luo et al. / Journal of Mechanical Science and Technology 25 (2) (2011) 371378 377 The flowrate and volumetric efficiency diminish gradually when ps increases. Moreover, the larger the ps, the faster the diminution speed of the flowrate and volumetric efficiency. When ps =3.5106Pa (rated pressure), the volumetric effi-ciency is only 74.7%. The reason for this low volumetric effi-ciency is that the lengths of clearance seal between the valve chamber and outlet and intake ports are both very short, and then there is large leakage. 6. Conclusions In this paper, an axial piston water-pump with piston valve, which utilizes the pistons existing phase difference and in-terworking to drain and suck water, has been analyzed and designed. On the basis of the introduction of the working prin-ciple, it is known that the pump opens and closes the outlet port and intake port in an active way, and the flow rate changes in-phase with the passage areas of the intake and outlet ports. All of these characteristics are helpful to reduce the pressure surge in the piston chamber. Thus, the supposi-tion that the pressure in the piston chamber stays constant is considered as the optimized object. According to our analysis, the shapes of the outlet and intake ports are both rectangles whose lengths are a half stroke. Thereafter, simulations of the optimized pump have been performed. The simulation results indicated that the rectangular outlet and intake ports could make the flow rate in the piston chamber change wholly in-phase with the passage areas of outlet port and intake port. The pressure curve in the piston chamber presents two straight lines, which means there is almost no pressure surge in the piston chamber. At the same time, the pressure impact is very small when high and low pressure are conversing. Further-more, the experiment results show the fact that there are no pressure surges in the outlet port and intake port, and the volumetric efficiency is only 74.7% because of the short lengths of clearance seal between the valve chamber and the outlet port as well as intake port. Acknowledgment This work was supported by the Natural Science Founda-tion of China (No. 10972086). The authors thank the anony-mous reviewers for their insightful comments and suggestions that helped in improving the manuscript. Nomenclature a3 : Passage area of the 3rd outlet port, m2 a3 : Passage area of the 3rd intake port, m2 Cq : Flow coefficient of the outlet port Cq : Flow coefficient of the intake port dp : Diameter of piston, m Ld : Length of the outlet port, m Ld3 : Length of the 3rd outlet port, m Ld : Length of the intake port, m Ld3 : Length of the 3rd intake port, m p0 : Pressure at intake port, Pa p1 : Water pressure of the 1st piston chamber, Pa ps : Pressure at outlet port, Pa q1 : Flowrate of the 1st piston chamber, m3/s q : Flowrate of the pump, m3/s R : Radius of swashplate, m s1 : Displacement of the 1st piston, m s3 : Displacement of the 3rd piston, m smax : Stroke of piston, m v1 : Velocity of the 1st piston, m/s V0 : Clearance volume of a single piston chamber, m3 V1 : Volume of the 1st piston chamber, m3 y : Area gradient
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
|
2:不支持迅雷下载,请使用浏览器下载
3:不支持QQ浏览器下载,请用其他浏览器
4:下载后的文档和图纸-无水印
5:文档经过压缩，下载后原文更清晰
|
川公网安备: 51019002004831号