Designing an axial turbine in principal is simple, i.e., putting a propeller in a tube. With years of experience, the basic design has been developed into a relatively complex assembly. The key aspect of any design is keeping the turbine spinning freely. Hence, bearing design and sources of drag within the assembly have been given special focus.
Due to this, it is difficult to make miniature axial turbines as the relative turbine energy is largely negated by the bearing and sensor drags. For rotational efficiency, plain bushes or roller/ball bearings are employed. A ball is generally employed to handle the end thrust. The presence of hydrodynamically designed turbine and bearing supports in some designs creates a low pressure zone in front of the turbine. As a result, the turbine is pulled forward, thus mitigating or removing the end thrust.
The bearing supports lower pressure drop but increases the fluid velocity over the turbine blades. The sensor is typically magnetic and provides a low voltage sine wave output. An electronic pick-up is generally employed for extended flow range, extra accuracy or in the case of operating the flow meter in an electrically noisy environment.
What is an Ultrasonic Flow Meter : Types and Its Applications
The first ultrasonic flow meter was invented by Japanese physicist namely “Shiego Satomura” in the year 1959. This flow meter uses Doppler technology and the main intention of this meter is to deliver the analysis of blood flow. After four years, the earliest flow meters have appeared in industrial applications. At present, there are many manufacturing companies were designing different types of clamp-on flow meters to measure the liquid flow within a pipe. These meters use high-frequency sensors by penetrating throughout the pipe wall as well as the liquid by using Doppler otherwise transit time propagation method. So that fluid velocity and flow rate can be determined.
What is an Ultrasonic Flow Meter?
Definition: An ultrasonic flow meter can be defined as, a meter that is used to measure liquid velocity with ultrasound to analyze the volume of liquid flow. This is a volumetric flow meter that needs bubble or minute particles within the liquid flow. These meters are suitable in the applications of wastewater but they will not work with drinking/distill water. So this type of flow meter is ideal for the applications wherever chemical compatibility, low maintenance, and low-pressure drop are required.
These meters will affect the audio properties of the liquid and also impact through viscosity, density, temperature, etc. Like mechanical flow meters, these meters do not include moving parts. The price of these meters will change greatly so frequently it can be used and maintained at a low cost.
Ultrasonic Flow Meter Working Principle
An ultrasonic flow meter construction can be done by using upstream and downstream transducers, sensor pipe and reflector. The working principle of ultrasonic flow meter is, it uses sound waves to resolve the velocity of a liquid within a pipe. There are two conditions in the pipe like no flow and flowing. In the first condition, the frequencies of ultrasonic waves are transmitted into a pipe & its indications from the fluid are similar. In the second condition, the reflected wave’s frequency is dissimilar because of the Doppler Effect.
Whenever the liquid flows in the pipe quickly, then the frequency shift can be increased linearly. The transmitter processes the signals from the wave & its reflections determine the flow rate. Transit time meters transmit & receive ultrasonic waves in both the directions within the pipe. At no-flow condition, the time taken to flow in between upstream & downstream in between the transducers is the same.
Under these two flowing conditions, the wave at upstream will flow with less speed than the downstream wave. As the liquid flows faster, the distinction between the up & downstream times raises. The times of the upstream & downstream processed by the transmitter to decide the flow rate.
Types of Ultrasonic Flow Meter
Ultrasonic flow meters available in the market are radar, Doppler velocity, ultrasonic clamp-on, and ultrasonic level.
Doppler velocity type meters use reproduced ultrasonic noise to calculate the liquid’s velocity.
Radar type meter employs microwave technology for transmitting small pulses to reflect off a flowing surface back to the sensor for deciding velocity.
Ultrasonic clamp-on type meter is ideal for applications wherever accessing the pipe is difficult otherwise not possible.
Ultrasonic level type meter is ideal for determining the fluid level in both open & closed channels.
