压缩机气阀设计基础

Valves Fundamental Design 气阀设计基础 Paul Modern Chief Engineer Valves Flow Control Products 2PROPRIETARY AND CONFIDENTIAL Valve Fundamental Operation气阀基本工作原理 Valve Technical Design气阀技术设计 Material Considerations材料选择 Valve Design Principles 气阀设计原理气阀设计原理 3PROPRIETARY AND CONFIDENTIAL Valve Fundamental Operation气阀基本工作原理 Valve Technical Design Material Considerations Valve Design Principles 气阀设计原理气阀设计原理 4PROPRIETARY AND CONFIDENTIAL The sheer quantity of operation cycles involved soon highlights any problems with design 下面例子中 气阀运动周期之多足以说明气阀设计所要面临的问题 Example 1 API618 type compressor at 400RPM Valves open and close 210 million times in one year 8000 hrs 举例1 假如压缩机转速400RPM 气阀开启关闭2 1亿次每年 8000h Example 2 High speed compressor at 1200RPM Valves open and close 630 million times 举例2 假如压缩机转速1200RPM 气阀开启关闭6 3亿次每年 8000h Car engine average 3000 RPM 20 000 km Around 300 hrs and 54 million cycles Easy 汽车发动机 平均转速3000RPM 2万公里 约300hs 约5 4千万运动周期 Conclusion Compressor valves have a very hard life Valve designs have developed over many years to develop specific types for specific applications 从这个角度看 压缩机气阀能运行8000h真不容易 气阀设计经过多年发展 针对具体工况 需要设计 特定的气阀 Valve Fundamental 气气阀基础阀基础 7PROPRIETARY AND CONFIDENTIAL Basic Valve Principles 气阀基本原理 Valves rely solely on pressure differential and flow forces to operate 气阀仅仅依靠压差和气体力启闭 Inlet Suction Outlet Discharge are one way valves 气阀是单向阀 Sealing element s plate ring poppets move between seat and guard 密封原件在阀盖阀座之间运动 Valve closing is controlled by spring forces 弹簧控制气阀的启闭 Valve Fundamental 气气阀基础阀基础 8PROPRIETARY AND CONFIDENTIALDischarge Suction Valve Fundamental 气气阀基础阀基础 Head End HE 盖侧 Crank End CE 轴侧 Basic Valve Principles气阀基本原理 Start of piston motion at bottom dead centre BDC zero velocity all valves closed 活塞在下止点的时候 速度为零 所有气阀处于关闭状态 9PROPRIETARY AND CONFIDENTIALDischarge Suction Valve Fundamental 气气阀基础阀基础 Basic Valve Principles气阀基本原理 Piston starts to travel gas pressure changes due to expansion of volume below piston CE compression of volume above piston HE 活塞开始运动 轴侧气阀膨胀 压力下降 盖侧气阀受压缩 压力上升 Pressure Increasing Pressure Dropping 10PROPRIETARY AND CONFIDENTIALDischarge Pressure Increasing Pressure Dropping Suction Valve Opens Suction Valve Fundamental 气气阀基础阀基础 Basic Valve Principles气阀基本原理 Pressure differential opens suction valve against springs lighter springs on crank end 气缸内外的压差克服轴侧进气阀弹簧力 气阀打开 11PROPRIETARY AND CONFIDENTIALDischarge Gas Flowing into Cylinder Suction Valve Fundamental 气气阀基础阀基础 Basic Valve Principles气阀基本原理 Flowing gas drag forces and differential pressure allow gas to flow into CE cylinder 气体力和压差共同作用下 气体继续流入气缸轴侧 HE still compressing 盖侧气体继续压缩 Pressure Increasing 12PROPRIETARY AND CONFIDENTIAL Valve Fundamental 气气阀基础阀基础 Basic Valve Principles气阀基本原理 HE pressure increases enough for differential pressure to open discharge valve 盖侧气体受压上升 气缸内外压差大于弹簧力 盖侧排气阀打开 Discharge Discharge Valve Opens Suction Gas Flowing into Cylinder 13PROPRIETARY AND CONFIDENTIAL Suction Discharge Gas Flowing into Cylinder slowing rate Gas Flowing out of Cylinder Valve Fundamental 气气阀基础阀基础 Basic Valve Principles Gas flowing into CE at suction pressure gas flowing out of HE at discharge 轴侧气体压力等于进气压力 盖侧压缩气体排向气缸外 Piston slowing 活塞减速 14PROPRIETARY AND CONFIDENTIAL Suction Discharge Pressure Equalises Springs in Valves Close Elements Pressure Equalises Valve Fundamental 气气阀基础阀基础 Basic Valve Principles Near to top dead centre TDC flow rates decrease pressures equalise valve springs overcome forces and close valves At least that s the plan 活塞快到上止点 气体流速下降 压力达到平衡 气阀弹簧力克服气体力 气阀关闭 气阀随着曲轴的 转动周而复始这样工作 15PROPRIETARY AND CONFIDENTIAL Valve Technical Design Flow Area 气阀设计技术气阀设计技术 通流面积通流面积 Basic Valve Principles Flow流量 Valves need enough flow area for efficiency 气阀需要足够的通流面积保证流通性 Flow area changes power loss changes 通流面积改变 压力损失改变 Physical space available for a valve usually dictates area pocket dimensions 阀窝的尺寸基本上限制了气阀的大小 16PROPRIETARY AND CONFIDENTIAL Valve Technical Design Flow Area 气阀设计技术气阀设计技术 通流面积通流面积 PRESSURE DROP P 0 5 x x x v2 PRESSURE DROP COEFFICIENT Orifice Plate Passage Area A cm2 Pipe D Pressure Drop Across Orifice P bar EFA area cm2 Basic Valve Principles Valves need enough flow area for efficiency 气阀需要一定的流通面积 Flow area changes power loss changes 通流面积改变 压力损失改变 Flow restriction can be studied by flow testing 通过实验测试流动损失 Valve flow area can be stated in 2 ways 气阀流通面积的两种计算方式 Passage area or lift area FULL geometric flow area of valve when fully open气阀完全开启后的几何流通面积 Effective flow area EFA comparative flow area to constrained flow through an equivalent orifice plate used to calculate pressure and power losses有效流通面积 17PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Pressure drop P 0 5 x x x v2 压力损失计算 P 0 5 x x x v2 Substitute actual valve and determine 实验测试数据能代表实际气阀并确定阻力系数 Do this for a range of valve lift values With this data for a range of valve sizes we can calculate accurate power losses 测试一系列升程值的阻力系数 根据这些数据就 可以准确计算功率损失 EFA passage area SQRT Valve Technical Design Flow Area 气阀设计技术气阀设计技术 通流面积通流面积 Lift Relationship 0 00 0 50 1 00 1 50 2 00 2 50 3 00 3 50 4 00 00 20 40 60 811 21 41 6 lift h Coefficient 0 00 5 00 10 00 15 00 20 00 25 00 30 00 EFA cm 2 EFA area cm2 Pressure Drop Across Orifice P bar Passage Area A cm2 18PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Using EFA value we can calculate Q Valve size adequacy is determined using valve Q factor 通过有效通流面积计算Q值 Q值决定了气阀大小是否合适 Q indicates pressure drop as a percentage of suction pressure Q needs to be in a range 2 to 15 ideally 2 to 5 Q值表示压力损失的百分比 通常在2 15之间 理想状态是2 5 Below 2 the valve is too large and low spring forces may allow pulsation effects and potential valve flutter issues 低于2 表示气阀太大 气阀会有振颤 Above 15 the valve is too restrictive and will cause excessive pressure and therefore power losses 大于15表示气阀太小 压力损失太大 功耗急剧上升 Valve Technical Design Q Value 气气阀设计技术阀设计技术 Q Q值值 where Qsv q at suction pressure 进气阀Q值 s suction gas density 进气密度 Ps suction pressure 进气压力 Vm mean gas velocity 流速 Fe passage lift area 通流面积 EFA 有效通流面积 19PROPRIETARY AND CONFIDENTIAL Valve Technical Design Flow Area 气阀设计技术气阀设计技术 通流面积通流面积 Summary Flow总结 If we know valve coefficient from experiments we can calculate EFA 如果知道气阀阻力系数 就能计算有效通流面积 If we know EFA and flow rate we can calculate pressure drops 如果知道有效通流面积 就能计算压降 If we know pressure drops we can calculate Q 如果知道压降 就能计算Q值 If we know Q we can judge efficiency of the design to a known standard 如果知道Q值 就能判断气阀的流通性能是否符合要求 Lift Relationship 0 00 0 50 1 00 1 50 2 00 2 50 3 00 3 50 4 00 00 20 40 60 811 21 41 6 lift h Coefficient 0 00 5 00 10 00 15 00 20 00 25 00 30 00 EFA cm 2 20PROPRIETARY AND CONFIDENTIAL Valve Technical Design Spring Forces 气阀设计技术气阀设计技术 弹簧力弹簧力 Basic Valve Principles Forces弹簧力 Valves need springs to close on time 需要弹簧准时关闭气阀 Poor spring load design poor dynamics and high impact speeds 弹簧力不合适 气阀动力学性能差 阀片撞击速度高 Dynamic modelling of forces is required 气阀设计时需要创建气阀动力学模型 21PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Why do valves need springs 为什么需要气阀弹簧 With no springs the sealing element or plate does not close until gas begins to flow backward through the valve This would slam the valve shut and shorten valve life 没有弹簧 密封原件或阀片不能准时 关闭 气体回流 会增加阀片或密封 原件额外的撞击力 缩短气阀寿命 Valve Technical Design Spring Forces 气阀设计技术气阀设计技术 弹簧力弹簧力 22PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Flow creates drag forces on plate ring 气流通过阀片时会产生气体力 Experimental known flow rate measure force 实验测试气体流量 气体力 CFD generated flow pressure force data CFD生成气流和压力数据 With this experimental data for a range of valve lifts we can calculate accurate drag forces for any differential flow rate根据这些实验数据可以精确计算任何流量的气体力 Valve Technical Design Spring Forces 气阀设计技术气阀设计技术 弹簧力弹簧力 EFA and Force Area CFD Generated Plate Pressure Profile 23PROPRIETARY AND CONFIDENTIAL Basic Valve Principles 气阀基本原理 Valve Technical Design Dynamic Model 气阀设计技术气阀设计技术 动力学模型动力学模型 D is c h a r g e 24PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Valve Dynamics Simulation Software 气阀动力仿真程序 Valve Technical Design Dynamic Model 气阀设计技术气阀设计技术 动力学模型动力学模型 25PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Valve Dynamics Simulation Software Late Closure延迟关闭 Valve Technical Design Dynamic Model 气阀设计技术气阀设计技术 动力学模型动力学模型 Late closure reversed flow causes high impact speeds bad for reliability 延迟关闭 气体回流 高撞击速度 可靠性差 May be caused by insufficient spring load in valve or valves with too small an area 原因是气阀弹簧力太弱或者气阀太小 0 50 100 090180270360 Crank Angle Lift Suction HE Delivery HE Suction CE Delivery CE 26PROPRIETARY AND CONFIDENTIAL Basic Valve Principles Valve Dynamics Simulation Software Valve Flutter振颤 Valve Technical Design Dynamic Model 气阀设计技术气阀设计技术 动力学模型动力学模型 Insufficient gas drag flutter causes multiple impacts also bad for reliability 气体力不够 气阀颤振 可靠性差 May be caused by excessive spring load in valve or valves with too large an area 原因是弹簧力太强或者气阀太大 0 50 100 090180270360 Crank Angle Lift Suction HE Delivery HE Suction CE Delivery CE 27PROPRIETARY AND CONFIDENTIAL 0 50 100 090180270360 Crank Angle Lift Suction HE Delivery HE Suction CE Delivery CE Basic Valve Principles Valve Dynamics Simulation Software Satisfactory设计合理 Valve Technical Design Dynamic Model 气阀设计技术气阀设计技术 动力学模型动力学模型 Minimal valve flutter at end of stroke as flow rate decays valves closed on time 阀片在气体力逐渐减弱时关闭 气阀准时关闭 Impact velocities of plates rings controlled and within material based limits 阀片或阀环撞击力控制在材料允许的范围内 28PROPRIETARY AND CONFIDENTIAL Valve Technical Design Dynamic Model 气阀设计技术气阀设计技术 动力学模型动力学模型 Caveat 注意 Dynamics can only be optimised for one set of conditions 气阀的最佳动力学性能只适用于一种工况 Changes to gas weight change dynamics 气体摩尔质量变了 气阀的动力学性能也会改变 Changes to RPM change dynamics 压缩机转速改变同样会改变气阀动力学性能 Compressors with multiple duties or a range of RPM are very difficult for valves 很难保证变工况和变转速的压缩机上的气阀寿命 29PROPRIETARY AND CONFIDENTIAL Valve Technical Design Dynamic Model Summary Forces If we know valve force coefficients from experiments we can calculate flow forces 通过实验获得气体力系数 就能计算气体力 If we know flow force and spring detail we can calculate plate position 知道气体力和弹簧数据 就能计算阀片位置 If we know plate position we can determine mass flow and iterate 知道阀片位置就能计算气体质量流量 If we know position throughout stroke we have dynamics to determine life 所以计算整个活塞行程中阀片位置 就能控制气阀的动力性能 掌握气阀的寿命 0 50 100 090180270360 Crank Angle Lift Suction HE Delivery HE Suction CE Delivery CE 30PROPRIETARY AND CONFIDENTIAL Valve Fundamental Operation Valve Technical Design Material Considerations材料选择 Valve Design Principles 气阀设计原理气阀设