目前市场上的罗茨米兰(中国)多为三叶式。三叶罗茨米兰(中国)采用两组三叶叶轮，每转动一次完成 3 次吸气和排气。它属于容积式风机，是一种定容旋转的气动力机器，具有结构简单、性能稳定的特点。

　　At present, most Roots blowers on the market are three bladed. The three bladed Roots blower uses two sets of three bladed impellers, with each rotation completing three suction and exhaust operations. It belongs to the positive displacement fan, which is a fixed volume rotating pneumatic machine with the characteristics of simple structure and stable performance.

　　罗茨米兰(中国)选型技巧

　　Selection Techniques for Roots Blowers

　　1、挑选

　　1. Select

　　在为污水处理厂挑选罗茨米兰(中国)时，相关产品样本上显示的是其在标准进气状态下的性能参数。但罗茨米兰(中国)在实际使用中并非处于标准状态，当使用环境的温度、大气压、海拔高度等条件不同时，风机的性能也会随之改变。因此，产品样本上的性能参数不能在设计和挑选时直接采用，而是需要根据实际使用状态，将风机的性能要求转换为标准进气状态下的参数后再使用。

　　When selecting Roots blowers for sewage treatment plants, the performance parameters displayed on the relevant product samples are under standard intake conditions. However, Roots blowers are not in a standard state in practical use. When the temperature, atmospheric pressure, altitude and other conditions of the operating environment are different, the performance of the blower will also change accordingly. Therefore, the performance parameters on the product sample cannot be directly used in design and selection. Instead, the performance requirements of the fan need to be converted into parameters under standard intake conditions based on actual usage before use.

　　2、压力

　　2. Pressure

　　容积式罗茨米兰(中国)的排气压力并不由其自身决定，而是由风机排出气体后装置的情况，即所谓的 “背压” 来确定。曝气米兰(中国)具有强制送风的特点，罗茨米兰(中国)铭牌上标注的排气压力是其额定排气压力。实际上，只要强度和排气温度允许，罗茨米兰(中国)既可以在低于额定排气压力的任意压力下工作，也能在高于额定排气压力的情况下运行。

　　The exhaust pressure of a positive displacement Roots blower is not determined by itself, but by the condition of the device after the fan exhausts the gas, known as the "back pressure". The aeration blower has the characteristic of forced air supply, and the exhaust pressure marked on the nameplate of the Roots blower is its rated exhaust pressure. In fact, as long as the strength and exhaust temperature allow, Roots blowers can operate at any pressure below the rated exhaust pressure or above the rated exhaust pressure.

　　对于污水处理厂而言，排气系统产生的背压是管道系统压力损失值、曝气池水深与环境大气压力的总和。

　　For sewage treatment plants, the back pressure generated by the exhaust system is the sum of the pressure loss value of the pipeline system, the water depth of the aeration tank, and the ambient atmospheric pressure.

　　3、风量（需氧量）

　　3. Air volume (oxygen demand)

　　在计算污水处理需氧量时，得出的结果是标准状态下所需氧气的质量流量 qm（kg/min），之后再换算成标准状态下所需空气的体积流量 qv1（m/min）。如果罗茨米兰(中国)的使用状态并非标准状态，比如在高原地区，空气密度和水分含量会发生变化，此时罗茨米兰(中国)提供的风量流量虽与标准状态相同，但供给空气的质量流量会有所下降。

　　When calculating the oxygen demand for sewage treatment, the result obtained is the mass flow rate qm (kg/min) of oxygen required under standard conditions, which is then converted into the volume flow rate qv1 (m/min) of air required under standard conditions. If the usage state of the Roots blower is not standard, such as in high-altitude areas, the air density and moisture content will change. At this time, although the air flow rate provided by the Roots blower is the same as the standard state, the mass flow rate of the supplied air will decrease.

　　4、冬夏的区别

　　4. The difference between winter and summer

　　挑选风机时，要留意其送风量的变化规律。对于同一台罗茨米兰(中国)，冬夏两季的体积流量不会改变，但由于空气密度不同，质量流量会有所差异，也就是供氧量不同。这是因为冬季气温降低，空气密度增大，所以风机供给的干燥空气质量流量比标准状态下有较大增加，进而使供氧量增多。

　　When selecting a fan, pay attention to the variation pattern of its air supply volume. For the same Roots blower, the volumetric flow rate in winter and summer will not change, but due to different air densities, the mass flow rate will differ, that is, the oxygen supply will be different. This is because the winter temperature decreases and the air density increases, so the dry air mass flow rate supplied by the fan is significantly increased compared to the standard state, thereby increasing the oxygen supply.

　　因此，在生产运行过程中，需要针对这种变化及时调整设备，让罗茨米兰(中国)的充氧能力与实际运行中的需氧量相匹配。对于罗茨米兰(中国)来说，使用变频器通过改变风机转速来调节送风量，是一种经济实用的方式。

　　Therefore, in the production and operation process, it is necessary to adjust the equipment in a timely manner to match the oxygenation capacity of the Roots blower with the actual oxygen demand during operation. For Roots blowers, using a frequency converter to adjust the air supply by changing the fan speed is an economical and practical way.

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