Meteorological Particle Sensor (MPS)

The MPS, or PMS, instrument collects a continuous sample of the droplets passing through the measurement region. Ideally suited for larger drops and sparse sprays, the instrument is typically used to measure rainfall droplet characteristics. The MPS system provides a method for the Spraying Systems Co. testing lab to measure larger droplets that may not be spherical, and can even provide results demonstrating the ligament-type nature of an incompletely atomized spray. Post-processing software allows the continuous data stream to be converted to drop size statistics and distributions.

The methodology used with the MPS instrument is consistent with other Optical Array Probe (OAP) instruments; Spraying Systems Co. currently uses the Droplet Measurement Technologies MPS instrument.

Method ▼

The MPS systems uses a laser light source to provide a background light, which is sensed by a series of optical sensors directed toward the laser source. As droplets pass through the laser beam, a diode may register a reduced light intensity and this is recoded for post processing. The system has a fixed sample rate (all diodes simultaneously), which is manually set according to the average drop velocity, and the result is recoded as a running set of measurements from the diode array which may be examined as a continuous data stream.

Custom post-processing software, developed by Spraying Systems Co., allows the data stream to be post-processed into a standard drop size distribution and related statistical drop size values. Given the instruments roots in measuring rain droplets, a mean terminal velocity is also calculated.

Benefits ▼

The laser back-illumination and optical diode array provide a non-intrusive method to characterize large, sparse, and potentially non-spherical droplet sprays. The MPS systems provides a uniquely large maximum measureable drop size, up to 6000 um.

While the MPS system is able to measure extremely large droplets, the diode resolution is 100um, providing a strong limitation on the resolution and its ability to measure small droplets.

Examples ▼

The MPS instrument is used when the droplets are very large, on the order of millimeters, which will typically result in non-spherical droplets. Examples of past projects using the MPS system at Spraying Systems Co. include extensive measurements with large capacity WhirlJet® nozzles, often used in refinery and processing applications. This instrument is also used in rain simulation studies due to its original design purpose that lends itself to droplets approaching from a known and uniform direction.

Rain simulator development

A customer contact Spraying System Co. to request the design and development of a rain simulation system. The wide array of Spraying Systems CO. nozzles as well as support piping and pumping expertise allowed for a prototype assembly to be tested and modified before delivering the final total solution to the customer. The MPS was used to measured and characterized the spray and optimize the operating parameters to achieve the designed spray characteristics.

Large WhirlJet nozzle characterization

Spraying Systems Co. manufactures very large WhirlJet® nozzles which can spray hundreds of gallons of water per minute and produce very large droplets. These droplets are typically non-spherical and are therefore best suited to be characterized by the MPS instrument. Due to the application details, there was a maximum drop size which the nozzle could produce, and the MPOS was used to determine the maximum achievable flow rate while adhering to this limitation.

Example Data ▼

MPS Data
MPS Data 2