Gas turbine performance are optimized by the precise humidity measurement

Gas turbine to ensure efficient operation is the first goal of operators.In the current economic situation, any can improve productivity, so as to increase profits, apparently, is welcome.From the Angle of environment, make the turbine running as efficiently as possible and produce emissions as low as possible is also very important.Fortunately, there are many ways to increase the output power of gas turbine.Control the entrance into the combustion air humidity and temperature is one of the important measures, because it directly affects the efficiency of steam turbine, emissions, and reliability.

More cold, more strong air can improve the output and efficiency

In terms of the efficiency of gas turbine, the influence of the air density is well known: more intensive intake increases the mass velocity, thus improved the output and efficiency of the steam turbine.Air density is inversely proportional to the temperature, which means that the temperature can reduce air density, thus reducing the efficiency of gas turbine and power.

Inlet cooling (especially in the warm and hot environment) is typically used for compensation due to the high air temperature efficiency loss.Even if slightly lower air temperature, also can lead to significantly higher power output.

Every 1 ° C below the air temperature, the output power can be improved as much as 0.5%.

There are several techniques can be used for cooling air intake.A common solution is to spray, the system through the nozzle to spray the water to the air, and as the water droplets evaporation cools the air.Atomization of the second advantage is that the increase of air humidity reducing NOx emissions generated in the combustion process.In addition to the warm or hot conditions cooling air intake, humidity is also avoid a key factor in the icy cold climate.If the wet air close to freezing, the anti-icing system are needed to protect the compressor from damage from the fast moving grains of ice.

To achieve the ideal control, need accurate information about the humidity

In view of the air intake system of high speed air flow, must prevent water droplets and ice particles from entering the compressor and turbine, lest cause costly damage and corrosion.In fact, this means that the need to keep the air humidity under saturation level.In other words, in order to avoid condensation, enter the system of the air dew point temperature must be lower than the air in the system and the surface temperature.Control system must have a safety margin to the property of measurement uncertainty and measuring air fluctuations and irregularity.However, the allowance of measurement uncertainty and need more wide, the greater the potential loss of efficiency.This is a high level of measuring reliability really play a role.Accurate measurement of dew point can make cooling and fog (or even heating) as much as possible close to ice condensation or limit in the system.

Said the humidity of different methods

Humidity according to applications using different terms, including but not limited to, relative humidity, dew point temperature and wet bulb temperature.

Relative humidity (RH)Is water vapor partial pressure under certain temperature and the ratio of the saturation pressure.RH expressed as a percentage, is often used to describe the environment humidity of the air.Use of RH downside is that it depends largely on the temperature.For example, if the RH was 85%, the temperature is 20 ° C, the air temperature only reduce 2 ° C, 96% RH.If use RH to measure the humidity of the air turbine inlet, you must remember this correlation, because even if there is no cooling or heating, air inlet air temperature in the system will change too.Effect is mainly due to the acceleration of bell mouth air compressor and cooling, which may lead to some degrees Celsius temperature drop.Because the cooling effect, even if the environment temperature is higher than 0 ° C, there is still a risk of freezing.

Dew point temperature (Td)Refers to the air cooled at constant pressure, air due to water vapor become completely saturated liquid water temperature (called condensation).In RH was 100%, the environment temperature and the dew point temperature is the same, and when the dew point temperature is lower than the environment temperature, the air becomes drier, thus forming a lower risk of condensation.Use Td's two main advantage is that it has nothing to do with temperature, and its direct allowance for condensing condition.

Wet bulb temperature (Tw)Is wrapped in wet sheathed in the thermometer indicator of temperature.Wet bulb temperature and environmental temperature can be used in the calculation of relative humidity and dew point.Tw is used to determine the humidity of the traditional method, but due to the limited accuracy and takes the method of using and maintenance skill, therefore has largely replaced by direct measurement.Above all humidity parameters are related to stress, but for admission applications, a typical pressure drop is very small, that does not produce significant effect.For example, under 20 ° C and 1013 mbar, the pressure drop 20 mbar resulting in RH 1.7% lower or Td reduce 0.3 ° C.

The influencing factors of accuracy

There are many factors that can affect the accuracy of humidity measurement, one obvious factor is the basic sensing technology.Polymer film sensors, however, has been shown to meet the needs of intake monitoring of the key: accuracy, robustness and long-term stability and low maintenance requirements.As the air in the air inlet may be very close to saturation, may even be condensation formation, so even under these conditions, the sensor must also keep the accuracy.humidity传感器在冷凝空气中的一个挑战是，如果传感器变湿，则测量将持续显示饱和状态，直到传感器变干 - 即使空气本身不再饱和也是如此。为了解决这个问题，维萨拉开发了加热探头技术。这可确保探头的温度保持在周围空气温度以上，以避免在传感器本身上出现冷凝。根据系统和确切的安装位置，直接的溅水也可能会弄湿湿度传感器。可使用专用安装附件来防止发生这种情况发生。

In power plant and the polluted environment, intake may contain contaminants, it will affect the long-term accuracy of the transducer.In response to this challenge, for the advanced sensor configuration chemical removal function, this function by evaporation possible contaminants to automatically clean the sensor components.