Case Study:

Cooling and Vibration Control System for a Portable Oxygen Concentrator

Client:

SeQual Technologies

Project Scope:

Medical Device Research & Development

Methods:

Cooling System Design, Prototype Design

When San Diego based medical products company SeQual Technologies was developing the their first ambulatory oxygen concentrator, Flometrics redesigned the vibration, thermal and acoustic systems.

Flometrics unique cooling system for the compressor that cooled the oxygen system needed to provide a highly reliable continuous flow and pulse oxygen dose options in a 24/7 portable device. The device was intended for both stationary and ambulatory oxygen needs.

As a result of Flometrics design of cooling and vibration control system for the Eclipse, the small, lightweight unit was successfully launched and immediately revolutionized the industry with clinical features and accessory options that supported user’s active lifestyles.

The Eclipse 3 lowered operational costs by reducing monthly deliveries and simplifying inventory management and space. Now into its third generation, the award-winning product retains all of the initial designed systems. The SeQual Eclipse has become the clear choice for a non-delivery oxygen concentrator model.

Case Study:

Infant Respiratory Device

Client:

Cardinal Health

Project Scope:

Medical Device Research & Development

Methods:

Flow Visualization, Design & Testing, Prototyping

Flometrics designed a Nasal Continuous Positive Airway Pressure (NCPAP) ventilator for Cardinal Health to help premature and sick infants breathe. The ventilator keeps the baby’s lungs inflated as the inhale and exhale. It must keep a positive pressure in the lungs while allowing the baby to breathe easily, i.e the “work of breathing” must be minimized. The ventilator must also be small and lightweight. The photo at right shows a prototype that we designed and built.

The device is based on the jet pump principle but it allows for the flow to be reversed with minimal flow resistance. The jet sizes, flow rates and pressures were determined analytically to meet the customer’s specifications. The prototype ventilator worked as predicted.

We used flow visualization with laser sheet light and fluorescent particles in water to determine the optimum placement of the jets and other features in the device. The flow visualization was conducted in water with the scale adjusted to match Reynolds number.

In the image on the lower right, the two jets combine and help entrain air during the inhalation process. On the right, the exhaled air breaks up the flow pattern and allows the exhaled air to flow freely in the reverse direction. The pressure inside the patients lungs stays constant, regardless of the flow direction.

We used a Labview based data acquisition system to make measurements of the pressure and flow during simulated breathing cycles. The data was used to optimize the design.

Cardinal engineers took the fluid pathway that we developed and designed a ventilator which is less harmful to the baby’s nose than competitor products.

Case Study:

Biofuel Flight Test

Client:

In-House

Project Scope:

Research & Development

Methods:

Thermodynamics, Fluid Dynamics, Design & Testing

We launched the Biofuel rocket on July 11th at the FAR rocket test site near Cantil, CA, east of Edwards Air Force Base. The fuel was a renewable JP-8 developed by the EERC at the University of North Dakota for the Air Force Research Lab at Wright-Patterson. The fuel was developed under a contract with DARPA and was procured for us by Bob Allen at the Fuels and Energy branch of the Air Force Research Lab at Wright Patterson. The Biofuel worked quite well, propelling the rockets to a speed near Mach 1. The rocket propulsion system exceeded expectations. Our predictions for the flight indicated a maximum Mach number of about 0.9, just under the limit of supersonic flight. Although the Biofuel launch had a successful burn, the recovery system failed due to the fins experiencing critical flutter near apogee. We have flown these types of fins, tanks, engines, and pressurization systems before with no problem, therefore, we are left to believe the Biofuel had a much higher specific impulse than expected.

Flometrics originally built the rocket for Discovery Channel’s “Mythbusters” TV show. In addition, we were currently working on biofuel plant fluid dynamics at the time, so we decided to use the rocket to test whether Bio-Diesel would work as a rocket fuel. Besides the obvious environmental perks of using a cleaner, sustainable fuel, one can imagine growing oilseed crops on other planets to provide fuel for return vehicles. Also, there is always interest on how new designer fuels may improve rocket performance.

Flometrics initial static fire test using commercial grade Bio-Diesel proved a success, so we attempted to launch the rocket on Biodiesel. Unfortunately, during the launch the rocket had a hard start, which cracked the oxidizer manifold. However, this revealed a key safety attribute of the renewable fuel. With fuel and oxidizing spraying out on to a live igniter, there is a high potential for disaster. The low flammability/high flash point of the BioDiesel fuel left only an unusually small fire on the launch pad, leaving the rocket practically unscathed and ready for another launch attempt. For more see our article in Biodiesel Magazine.

For the final launch, we slowed down the fuel valve opening to prevent a hard start and used a more robust igniter [made by Jeff Kent with assistance from Ken Mason]. Overall, the fuel performed extremely well, with a flawless burn during the test flight. After the flight, we took apart the rocket engine to observe how the fuel performed. We noticed that the Biofuel burned much cleaner that the Jet A or the RP that we have used in the past. The injector plate normally is covered with a layer of sludge, but in the case of the Biofuel, it was very clean. The inside of the engine was coated with a layer of soot similar to what we usually see, which is good because it reduces the heat transfer. There was no visible damage to the engine, which is also good, because the engine will burn through if there is any reduction in cooling capacity of the fuel. The evidence from the biofuel rocket engine testing promotes confidence that one-day space vehicles will be able to travel using safer, cleaner, and sustainable fuels.

Unlike the red RP-1 [refined kerosene rocket fuel], the biofuel does not have any dye in it, It exhibits an odor of a sweet paint thinner. This fuel was designed to duplicate the properties of JP-8, the current jet fuel used by the U.S. Air Force. A particular challenge was achieving the same freezing temperature in the biofuel. However, it is very possible the fuel could be optimized for the cold temperatures of space. With custom designed biofuels, there is the possibility of increasing the density, heat transfer, and perhaps specific impulse of the fuel

Case Study:

Aircraft Cooling System Design

Client:

Northrop Grumman

Project Scope:

Cooling Design, Acoustic Testing, Prototyping

Methods:

Design & Testing, CAD, Parts Procurement

Northrop Grumman was contracted by the military to modify Hunter unmanned aerial vehicles (UAVs) from gasoline engines to turbo charged diesel engines. The plane needed new cowling to accommodate radiators and an intercooler. Flometrics support included:

• Design new cowlings and cooling paths




• Construct and test full size mock up of the cooling system




• Modify wind tunnel model and conduct wind tunnel measurements




• CFD of the UAV and cooling passages




• Write computer software to model flight parameters of the vehicle

The first step in the design process was to calculate the pressure coefficient over the entire aircraft in order to determine the best location for cooling air inlets and outlets. The flow through the scoops and ductwork was modeled in CFD to assure free flow of the cooling air.

The top right image shows the pressure coefficients on the original aircraft based on computational fluid dynamics (CFD) calculations, without propellers. The resulting information was used to select locations for the various cooling inlets and outlets. Then the intercoolers and radiators were tested with realistic flows, temperatures and pressures in a laboratory environment. This bench testing resulted in minor modifications which resulted in optimal performance of the system.

A scale model of the modified aircraft was fitted with prototype scoops, ducts, radiator and intercooler models and was tested in the wind tunnel with motorized propellers. The aircraft was then underwent extensive testing and later was placed in service with the U.S. military.

Case Study:

Cooling System Design for Portable Electronic Device

Client:

Broadcast Microwave Services (BMS)

Project Scope:

Cooling Design, Acoustic Testing, Prototyping

Methods:

Design & Testing, CAD, Parts Procurement

Flometrics client company Broadcast Microwave Services (BMS) was developing a new COFDM digital hand held portable microwave receiver with 2-way diversity for law enforcement, public safety, homeland security, and Unmanned Vehicle Remote Video Terminal (RVT) applications. This device was required to operate in harsh environments, dealing with extreme temperatures [0 to +55 °C] and rain. The exposure to moisture required the air inlet and outlet ducts to be separate from the internal circuitry. In addition, the cooling system had to be designed with strict thickness requirements to fit the compact electronics and match the slender final design. Also, the new handheld device would generate more waste heat than their previous products, so BMS asked Flometrics to aid them in the thermal design.

Flometrics provided the following services on this project:

• Calculations to optimize the system for maximum heat transfer coefficient with minimum fan power and thickness




• Designed heat sink and cross-flow fan to carry away waste heat from PCB




• Specified, procured and selected long-life brushless motor and controller




• Performed acoustical testing to minimize fan noise




• Had prototype heat sink and fan fabricated and tested




• Aided in CAD integration and documentation

Concept Development:

Several configurations were conceptualized, including axial and centrifugal fans. The cross-flow fan was selected due to it low profile, quietness, power consumption and availability to place the inlet & outlet out of hand hold regions.

Prototype:

A heat sink and fan were developed further and prototypes were made.

Test & Validation:

Prototype heat sink and fan were integrated with a mock-up PCB. Power resistors were used to simulate the expected thermal loads and the housing was instrumented with thermocouples. The prototype components met the requirements keeping all the PCB components under their design temperatures.

Integration into Detail Design:

Working with BMS, the heat sink, fan and motor were integrated into the top-level CAD model and BOM.

Finished Product:

With the help of Flometrics, BMS is proud to offer the Carry-Viewer III handheld microwave receiver. A great example of how Flometrics can provide the solutions to accelerate your product from conception to production, so that you get your ideas to market sooner and with confidence.

Case Study:

Gimbal Rocket Test

Client:

In-House

Project Scope:

Research & Development

Methods:

Thermodynamics, Fluid Dynamics, Design & Testing

Flometrics test of a fuel pressure powered hydraulic thrust vector control system. We tested our LR-101 Atlas vernier with a thrust vector control system of our own design. The goal is to be able to fly a rocket with a low thrust to weight ratio, so it can attain very high altitudes.

Testing of a gimbaled engine firing in the Mohave desert. The Gimbal system worked well. Hydraulic cylinders with solenoid valves were used to move the engine using fuel pressure and slide pots were used to monitor position. The system was controlled via a laptop computer using LabView.

Thrust Estimate

The thrust was only measured in one direction, so it changed as the engine was deflected.

Fuel LOX Pressure

The regulators have about 60 psi of droop. The LOX pressure continues to fall off while the fuel pressure holds steady because the more of the cold LOX tanks walls are exposed to the incoming helium as the level falls.

Control System Response

The nozzle deflected on startup, but the control system recovered and followed the programmed position pretty well after that. Each mm corresponds to an deflection of about 1/2 degree, so the system deflected +/- 2.5 degrees at a speed of 5-20 degrees per second.

The control signals represent what the valves were doing. The control system is on/off with orifices in each hydraulic cylinder to control the speed of actuation. The next step is to hook up our R-C allen artificial horizon and fly our liquid fueled rocket under automatic control.

Case Study:

Separated Flow Over A Truncated Pyramid

Client:

In-House

Project Scope:

Research & Development

Methods:

Flow Visualization, Fluid Dynamics, Design & Testing

The above photos show an example of flow separation. The flow is from left to right and the flow behind the pyramid is random and chaotic.

Flow separation causes excess drag and pressure drop in many products and systems. In the second photo, the flow is slower, and the pyramid is shedding vortices.

Case Study:

Computed Flow Over Land Speed Record Car

Client:

In-House

Project Scope:

Research & Development

Methods:

Computational Fluid Dynamics, Fluid Dynamics, Design & Testing

The image shows velocity contours over a jet powered car designed to win back the land speed record set by the British Thrust SSC car in 1997. The design was developed by Bill Fredericks, who designed the Budweiser Rocket Car that broke the sound barrier in 1979. The flow around the car was simulated using a commercial finite element code, Floworks.

This simulation involves the solution of the three dimensional, steady, compressible Navier-Stokes equations with Newtonian viscosity. The computational domain was chosen to simulate the environment as closely as possible and to make the boundary conditions, especially the problematic ground boundary condition. This simulation led to a number of improvements in the vehicle design.

Case Study:

Pulsatile Flow Through an Arterial Stent

Client:

In-House

Project Scope:

Research & Development

Methods:

Flow Visualization, Fluid Dynamics, Design & Testing

By looking at the flow through a stent, a better understanding of the reasons for restenosis can be understood. Flometrics evaluated a new type of stent under development and compared it to the market leader at the time. The first image above shows the market leading product in a transparent silicone rubber artery. The second image shows what portion of the stent is being visualized. The flow is seeded with fluorescent particles and illuminated by laser sheet light.

The third image shows the flow and the stent with respect to the artery wall under pulsatile flow. The video of the stent exit and similar flow visualization videos can be valuable when proving the efficacy of a medical device to the FDA.

Case Study:

Flow Visualization of Arteries

Client:

In-House

Project Scope:

Research & Development

Methods:

Flow Visualization, Fluid Dynamics, Design & Testing

Computed Flow Through Cerebral Aneurysm

Particle paths of the computed flow through a cerebral aneurysm. The flow was simulated using a commercial finite element code.

The second image is a cross section showing the pressure contours in the cerebral aneurysm. By combining CFD and flow visualization, Flometrics can analyze flows with accuracy and confidence.

Flow Visualization of Arteries

Flometrics has developed a technique for visualization of the flow within artificial arteries. This allow manufacturers of stents, valves and atherectomy devices to see how their devices affect the flow of blood in the body.

We have developed silicone rubber arteries with realistic compliance, curvature and excellent visibility. We can supply arbitrary pressure waveforms with our pressure pulse generator.

The flow within the artery is visualized using a proprietary technique similar to the laser sheet light technique. We can show the flow pattern around catheters, valves, stents, balloons and grafts with this technique.

Shown at right is a photo of the flow pattern in a carotid bifurcation. (Thanks to Dr. David Levy for the artery model and advice.)

In the movie below, the flow in an aneurysm is visualized. The slow flow rate and low shear levels inside the aneurysm may stimulate the growth of the aneurysm.

These flow visualizations can be valuable in showing the efficacy of medical devices and proving out conceptual design without expensive clinical studies. For situations like flow in an artery, flow visualization shows the flow pattern quickly and accurately.

The flow within the artery is visualized using a proprietary technique similar to the laser sheet light technique. We can show the flow pattern around catheters, valves, stents, balloons and grafts with this technique.