Final Design

Description of Final Design

The final design was divided into 3 components: the test rig, the mounting device, and the housing.

Assumptions

To obtain the final design, several assumptions were made. To obtain the final flow meter used in the final design, the following assumptions were made:

· The flow is fully developed

· The pump is constant

· No attenuation (energy loss) per bounce

Summary of Final Design

Housing

The final design of the flow meter housing will be taken up by CMA. The current housing has dimensions of 310mm X 145mm X 165mm. Unfortunately, the ADM 7407 and F601 flow meters were too large to fit within the housing, each having dimensions of 287mm X 200mm X 70mm and 226mm X 213mm X 59mm, respectively. The components in the housing include the flow meter system (computer and transducer), the stainless steel pipe, the transducer mounting device, and the power source.

Mounting Devices: Hinged Mounting Device

Hinged Mounting Device on Pipe Hinged Mounting Device - CAD

The mounting device is constrained to the pipe via a hinge mechanism with a screw on the opposite edge of the hinge, which serves to tighten the mount and hold it together. The hinge connects the top and bottom of the mounts, which have a cylindrical cutout to fit a circular pipe through. To constrain the pipe, foam will be lined to the cylindrical cutout to the transducer. For a smaller diameter pipe, the foam will be able to restrain the pipe in the proper place. For larger diameter pipes, the foam will compress and constrain the pipe.

Slots are cutout at the top of the mount to fit a ruler. The ruler slides into the slots and is constrained via a screw from the top. It also serves to keep the mounts and transducers in the same orientation with respect to each other, as well as to keep the optimal distance for the transducers known and constant.

Velcro Mounting Device

The hinged mounting devices serve to constrain the ultrasonic transducers to the pipe which the transducers are measuring a flow through. The mounts need to constrain the transducers such that the bottom of the transducer is in direct contact to the pipe. For this design, the transducer is inserted through the top slot, and will sit directly onto the pipe via gravity. There are also two screws on both sides of the mount, which constrains the transducer to the mount, see figure 9.Hinged Mounting Device on Pipe

Test Rig

The only sizing constraints of the bottom mount was that it needed to fit a 0.5 inch pipe and stick to the flat outer edges of a 4.45cm x 2.54 cm x 1.91 cm (1.75” x 1” x 0.75”) flat transducer. Thus, tolerances of 0.25 to 0.38 cm (0.1” to 0.15”) were added, in order to ensure a larger surface area for the transducer to stick to.

Due to the fact that we are testing 3 different sized pipes with varying thicknesses, a second mount was designed and fabricated in order to easily adjust and put on or take off the transducers on each pipe. It is a simple design that insures the transducers stick to the pipe and do not move during the testing phase. Essentially, there are two adhesive strips of Velcro hooks that are attached to the bottom of the transducer. On the opposite side, there is 3D printed cube, with a cutout for the pipe that will feature the Velcro loops on its top. Thus, by sticking the transducer on top of the pipe, which is nestled within the bottom mount, the Velcro halves then are compressed and the test rig setup is made stable. See figure 10 for a visual representation.

The purpose of this mounting device was for adjustability easiness. This mounting device is easy, simple and cost-effective. Since we already have a budget for the 3D printer, we would have not used it for any other designs otherwise. In addition, 5.08 cm x .508 cm (2” x .2”) strips of Velcro are quite cheap and easy to come by.

Velcro Mounting Device

There were two versions of the pipe mounts. The first was essentially a layer of steel plates. The first layer was a rectangular plate, measuring 12.7 cm (5”) by 17.8 cm (7”). Its corners contained four holes, each with a 2.54 cm (1”) long screw placed through it. A bracket with a width of 1.27 cm (.5”) was placed between the screws, and it was used to hold the pipe straight along the length of the plate. The ultrasonic transducers were placed on top of the pipe and constrained with another bracket of the same size. From here, another plate with holes in the corner was attached on top and set in place with the aforementioned screws. The layers were sealed together by tightening nuts onto the ends of the screws, thereby providing a secure mount for the transducers to measure from. The F601 meters were placed in this setup.

Steel Plate Mount

The main function of the test rig was for the calibration and optimization of the ultrasonic transducers. It provided a uniform flow condition for the two sets of ultrasonic transducers to measure simultaneously, thus providing a side-by-side comparison in real time. The test rig was essentially composed of two parts: a closed loop flow system, and basic mounts for the transducers.

The closed loop flow system was made up of the peristaltic pump, stainless steel piping, and flexible tubing. The size of the pipes and tubing used was dependent on diameter being tested. The stainless steel pipes were the interface for testing, and they were wrapped with a sound-proof material. This allowed them to keep the transducer waves within them without losing as much energy per wave bounce. There were cut outs on the top of the sound-proof material to allow the transducer waves to enter the pipe with minimal amounts of energy loss. The tygon tubes were used to provide an inlet for a hose to fill the system with water. They were also used to connect the stainless steel piping together, and provide a connection to the peristaltic pump flow path. The tygon tubes also housed valves on each end to close off the path of an external water source. When the loop was filled with water, the pump was used to actuate a controlled flow through it. The entire system ran through the transducer mounts. The overall system can be seen in the figure above.

The second version of the pipe mount was a set of H-bars mounted on top of each other. The ends of the H-bars each contained a spindle between them, constraining them together. These spindles were also used to hold the pipe between them. The H-bars’ widths were adjusted to match the size of the transducers, creating a snug fit with no lateral displacement. In addition to that, zip ties were used to push the transducers down onto the pipes. This ensured a secure fit for the transducer testing. The ADM7407 meters were housed in this setup. When the entire system was set up, a flow was run through the closed loop. The transducers were then set to start measuring the flow for the desired amount of time. The main design decisions of the test rig were the pipe material, flow conditions, and the setup of the transducer mounts. The optimal pipe material for the experiment was determined to be stainless steel. This was because stainless steel had the lowest attenuation coefficient for sound when compared to all other feasible materials. In addition to that, stainless steel was relatively cheap and abundant in source. The pipes were wrapped with the sound-proof material because accuracy was a high priority objective for the project.

The flow conditions were set by the peristaltic pump. A peristaltic pump was used because it was able to replicate very low-speed flow conditions with a great deal of accuracy. It was also able to provide a variable output for the speed of the flows.

The transducer mounts were built out of materials from the sponsor. They were built to constrain the transducers from moving on top of the pipe. Although the mounts for the test rig were somewhat rudimentary, they were able to constrain the transducers and provided a basis for the mounts designed in the project.

H-Bar Mount

The components required for purchase for the test rig were the pipes. The pipe material was chosen to be stainless steel because of its extremely low attenuation coefficient- meaning that the ultrasonic waves travelling through stainless steel lose less energy per bounce. The diameter and thickness of the pipes were variables used to test the accuracy of the transducers. The team chose a range of thicknesses and diameters to test different scenarios to find the optimal accuracy setting. The peristaltic pump and transducer mounts were provided by the sponsor, but the basis of their selection would have been based on the qualities listed in the previous section. The components of the test rig were constructed individually. The flow through the system needed to be a closed-loop system in order to have the pump running at a consistent and accurate rate. Tubes were attached at the ends to allow a water source to run through the system to clear of air bubbles and fill it with water. In addition to that, the connections for the peristaltic pump needed to be removable without affecting the rest of the system so that it could be calibrated.

The only requirement for the transducer mount was that it constrained the transducers to the pipes so that there was no movement or rotation for the duration of the testing.

Initially, both rigs were used separately to test flows for each set of transducers. However, they were combined to provide a real-time comparison of the meters on the same flow conditions. In addition to that, combining the test rig sped up testing considerably.

Digital Filter

Both first and second order filters were designed to obtain a better representation of the underground water seepage data. Both filters used a Taylor expansion. The first order filter utilized the equation , and the second order filter used the equation where is the raw, unfiltered velocity (collected data), is the once-filtered velocity, is the twice-filtered velocity, and (equal to where is the time step and is the time constant) is the filter coefficient.

Filter Comparisons

Project Performance

The designed components were able to meet the project's primary objectives: the calibration and optimization of the flow meters. The test rig was able to provide suitable simulations of low-flow conditions for the transducers to measure. The rig allowed both flows to test the same flow conditions simultaneously, and allowed pipes of varying diameters to be placed throughout it. In addition to that, the rig allowed the distance between the transducers to be easily adjusted to find the optimal configuration. The test rig conditions helped to show that the optimal distance between the transducers was about 13.3 cm (5.25 in) at a setting of 24 bounces.

The mounting devices were able to constrain the transducers upon the pipes efficiently. The hinged mounting device clamped the pipe down and kept it from rotating. It had the ability to easily switch transducers out, and it was also adjustable for distance. The mounting device did not impede the measurements of the flow meters, so it was considered to be an acceptable solution for the design criterion.

The velcro mounting device was able to easily switch between pipes, but it had trouble constraining the transducers onto the pipes themselves. As such, the signal strength attained by the transducers suffered. However, this mounting device was sufficient to run tests on the effects of low signal strength for the flow meters.

The housing evaluation showed that the current setup for the Ultraseep system would not be able to hold the flow meter controllers, as their current housing is not wide enough.