A 泵 curve chart is a graphical representation that illustrates the performance characteristics of a 泵. 它提供了泵在不同条件下如何运行的信息, 帮助用户了解泵的效率和能力. 这对泵的尺寸和选择至关重要.
泵曲线已经存在很长时间了，它包含了很多信息, 包括头, 流量, 效率和功耗. 典型的泵曲线在X-Y图上包含四个主要数据图:
总动态水头
总动态水头 (TDH) describes the total energy that a 泵 must overcome to move a fluid from one point to another within a piping system. 它是以下内容的总和:
- 静扬程-液体源表面与泵之间的垂直距离
- 压头-系统中的压力能量, 吸入(负压)和排出(正压)
- Friction head – the energy lost due to the resistance encountered by the flowing fluid as it moves through the system
总动态水头通常用长度单位表示，如米和英尺. 用于确定泵的工作点, as the 泵 must be capable of providing enough energy to overcome the TDH in the system to ensure proper fluid circulation.
总动态头在图形的垂直y轴上表示.
流量
流量 refers to the volume of fluid the 泵 is capable of moving through its system per unit of time. 通常以加仑每分钟(gpm)为单位。, 升每秒(L/s)或立方米每小时(m)3/h).
流量受泵产生压差的能力影响, 或头部, 这推动液体通过系统. The 泵 curve chart illustrates how the 泵’s 流量 changes at different levels of head.
流量在图的水平x轴上表示.
电力消耗
电力消耗 is the amount of energy required for the 泵 to operate at its duty point. 它通常以马力为单位来衡量.
功耗在图的垂直y轴上表示.
需要净正吸头
需要净正吸头 (NPSHr) is the minimum required pressure above the suction line to avoid cavitation issues at the selected 流量. 通常用英尺或米来测量.
为了避免空化, the NPSHr should always be less than the Net Positive Suction Head available (NPSHa) provided by the sump. NPSHa represents the total suction head available at the 泵 inlet and is calculated as the difference between the total suction head and the vapor pressure head. 当NPSHa大于NPSHr时，泵发生空化的可能性较小.
NPSHr在图的纵y轴上表示.
把它们放在一起
总动态头, 流量, 功耗和NPSHr数据, 以及效率和速度范围, 绘制在X-Y曲线上，称为泵曲线. 泵曲线的格式可能因制造商而异, 但所有泵曲线的原理是相同的. 在某些情况下, the information is displayed on one graph with multiple vertical Y-axis labels (总动态水头, 功率消耗和NPSHr)和流量在水平x轴上表示, 因为它是公分母.
在其他情况下, 信息显示在三个图表上:一个描绘了总动态水头和流量, 另一个描述功率消耗和流量, 第三张图描述NPSHr和流量.
作为图的一部分，泵的速度范围和效率点被覆盖. The speed and efficiency information comes from extensive testing performed by the 泵 manufacturer. This allows an individual to use their application’s 总动态水头 and 流量 to evaluate different 泵s to select the best option for their operation.
一旦确定了总动态水头并选择了所需的流量, 在泵曲线上查找信息很容易.
考虑一个带有三个图形的泵曲线.
1. 找到泵的工作点
首先，确定总动态水头和流量图上的坐标轴. 纵轴(y轴)表示以英尺或米为单位的总动态头部. The horizontal axis (X-axis) represents the 流量 of the fluid being pumped measured in gallons per minute, 升每秒或立方米每小时.
For example, consider an application with a 总动态水头 of 25’ and a 流量 of 1,000流量. Draw a horizontal line (shown in red dashes in the image below) across the graph at the known 总动态水头, 也就是25 '. 然后在已知流速下，在图中画一条垂直线(下图黄色部分), 也就是1,000流量. 两条线相交的地方就是泵的工作点.
2. 确定泵的效率范围
效率是输出功率与输入功率的比值. 泵曲线显示了泵在不同工作点的效率. 曲线上效率的最高点, 称为最佳效率点(BEP), 表示泵的最佳运行条件.
The graph depicting 总动态水头 and 流量 also features upward curving lines that illustrate efficiency (measured in percentage). 泵的工作点, 由总动态水头和流量的交集决定, 应在列出的效率范围内.
在下面的例子中, 泵的工作点落在69%的效率范围内, 哪个被认为是理想的选择.
如果工作点落在所示效率曲线的右侧, 泵通常被认为超出了范围. 在相同的TDH下，更大的流量可能会导致严重的泵送问题. 在大多数情况下，避免“在曲线的右侧操作”.
3. 确定所需的泵转速
The graph depicting 总动态水头 and 流量 also features horizontal curving lines that illustrate speed (measured in rpm). 速度是泵需要运行的速度，以满足工作点. 泵的工作点, 由总动态水头和流量的交集决定, 应该落在列出的速度范围内吗.
在下面的例子中, the 泵 speed for the determined duty point is between 450 rpm and 600 rpm at approximately 500 rpm (shown in orange).
4. 确定所需马力
利用第一张图中的信息, you can use the data on the next graph depicting power consumption and 流量 to determine the horsepower that will be required to operate the 泵 at its duty point.
第一个, 在已知流量(黄色部分)上画一条垂直线, 哪一个, 使用上面的例子, is 1,000流量. 然后, 在500 rpm到y轴上画一条水平线(用蓝色表示), 哪个是由第一张图确定的运行速度. 在水平线与y轴相交的地方需要的马力是多少, 在这个例子中, 是10马力.
比重如何影响泵的尺寸和选择
Note that the power consumption graph depicts the required power to operate the 泵 with only water; it does not show the impact of pumping a heavier 泥浆. 抽吸比水密度大的物质, 如骨料浆, 可能需要额外的马力来移动相同的距离. The specific gravity of the 泥浆 will be used to adjust the required horsepower for the application.
因为12.3 isn’t a standard horsepower rating, round up to the next interval, 哪一个 would be 15 in this case. 因此, the horsepower required for the 泵 to operate at its duty point with a sand and water 泥浆 at 14% solids would be 15 HP.
粘度如何影响泵的尺寸和选择
Viscosity is one of the more recognized physical properties of a fluid that influences the operation of a 泵. 粘度测量的是对剪切能量的阻力，例如在离心泵中. Honey at room temperature exhibits high internal resistance to flow and is considered to have a high viscosity. 低粘度液体具有低的流动内阻, 如室温下的水.
The effects of viscosity show up in calculating friction losses in a fluid process system and must be considered to make a good 泵 selection. 在一般情况下, a centrifugal 泵 is suitable for low viscosity fluids since the pumping action generates high liquid shear. 随着流体粘度的增加, 流量略有降低, 对泵的功耗有更大的影响.
5. 确定NPSHr
第三张图描述了所需的净正吸头. 在已知流量处绘制垂直线(下面黄色部分), 从我们的例子中我们知道哪个等于1,000流量. 在垂直线与地块信息相交的地方, 在y轴上画一条水平线(如下面的绿色所示). 在这个例子中，NPSHr是5 '的压力.
泵 curves can provide valuable information for selecting the right 泵 for an application. They use existing application data from the 总动态水头 and 流量 to size the 泵, and to then find the speed and horsepower required to operate the 泵 at its duty point within an ideal efficiency range. 它们还提供了计算净正吸头所需的信息, 哪一个 is the minimum pressure above the suction line to avoid cavitation — the imploding of vapor bubbles within the 泵 that can cause serious 泵 issues.
通过检查泵曲线, 用户可以确定泵在各种流量和水头条件下的性能, 哪一个 is crucial for selecting the right 泵 for an application and for optimizing its operation for energy efficiency.
