Metered dose inhalers (MDIs) are widely used for the treatment of lung diseases, such as asthma. The delivery of the drug to the lung can be as low as 5% of the metered dose. In order to maximize the dose, a patient needs to inhale whilst simultaneously actuating the inhaler, which can be difficult. Spacers have been developed to solve these drawbacks, and increase drug delivery to the lungs. However, there continues to be significant room for improvement.

FTS Engineering Answers has been investigating the parameters of most influence of drug delivery (the atomized droplet size distribution and the spacer geometry) using transient, multiphase CFD simulations.

The majority of the mass of the metered dose is an accelerant, typically HFA134, which provides the energy to atomize the spray. Detailed properties of the accelerant and the drug as well as multiphase heat and mass transfer are required in order to capture these physics correctly.

These physics are combined with detailed geometrical models of a range of spacer devices and design options (position of vents, valve position and design etc.) to quantify the effect of each change on the drug delivery.

FTS Engineering Answers is regularly asked to provide insight into the effectiveness of the cooling of electric motors particularly for the overall packaging of the motor within the electric machine, and to optimize the cooling design of electric motors.

Cooling the motor aims to maximise the motor efficiency by reducing temperature losses; allows for the potential of higher power density leading to weight and size reduction; and increases machine reliability by decreasing the operating temperatures. Design of motors is typically carried out in 2D motor design software. These capture the temperature dependent physics, but are limited in the 3D effects around the stator end windings.

FTS Engineering Answers has developed CFD modelling approaches for three methods of cooling:

• Air cooling
• Water cooling
• Oil Cooling

For all of these methods, the underlying temperature dependent physics are incorporated from the motor design software, and then the cooling is carried out in 3D CFD software, which captures the 3D effects around the stator end windings.

Air Cooling

Air cooling is the simplest form of cooling. In the example, there is forced convection over the motor; the heat that’s generated within the motor is transferred to the housing and convected away from the device via the cooling fins or conducted away via a heat sink.
Key engineering challenges are the effectiveness of the cooling within the overall packaging and the optimization of the cooling fin arrangements.

Water Cooling

Typically, a water/glycol mix is pumped through a series of channels in the motor’s housing. This approach is typical of larger automotive motors, because the approach is simple and robust, and the motor can be easily sealed. However, it leads to an increase in packaging of the motor. The cooling is indirect so the thermal inertia associated with the heat transfer from the hot stator windings to the cold water jacket can lead to reduced performance. Additionally, the cooling of the rotor is not as effective as the cooling of the stator. Key engineering challenges are the effectiveness and optimization of the cooling channels within the motor housing.

Oil Cooling of the Stator Windings Directly

In contrast to the indirect water cooling, here jets of oil are aimed directly on to the stator windings. The oil is injected via a series of high pressure nozzles, and after the oil is injected it must be drained and cooled and can then be recycled. The challenges of this approach are the arrangements for the high pressure nozzles; ensuring that the oil coverage of the windings is as uniform as possible to give even cooling; and the incorporation of oil outlets to drain the oil effectively. The major benefit of the approach is achieving very high convective heat transfer coefficients.
Key engineering challenges are the effectiveness and optimization of the oil cooling jets in ensuring uniform coverage of the windings and the drainage of the oil from the motor.

Contact FTS Engineering Answers to discuss your Motor Cooling questions!

The objective of the study was to demonstrate the process of taking a Medical Scan (either CT or MRI) extracting physical parts of the scan (in this case the carotid arteries) and carry out a simulation with that geometry.

Process
Using an open source tool (3D Slicer), the CT Scan was segmented to extract the carotid arteries. The segmented carotid arteries are then exported from 3D Slicer and imported into STAR-CCM+ as stl files.

Simulation
A Fluid Structure Interaction Simulation is then set up within STAR-CCM+. Appropriate boundary conditions are applied. A pulse flow rate at the inlet and a series of windkessel models at the outlets. Material properties are applied to the artery walls, and a pseudo “neck” is added around the artery to give the damping effect the neck does in reality.

We are able to support our clients with converting CT/MRI data to simulations, ensure sensible simulation set up and carry out FSI simulations; contact FTS Engineering Answers to discuss your questions!

One option for corneal transplants is DMEK (Descemet Membrane Endothelial Keratoplasty). The procedure is outlined here. As described, once the replacement cornea is unrolled and positioned in the anterior chamber of the eye, SF6 or Air is injected below the cornea graft to push it up to the graft site. SF6 or Air is then left in the chamber until it is naturally replaced by the aqueous fluid of the eye. This takes a few days.

During the recovery period the patient is instructed to lie down for longer periods especially in the immediate period after surgery. Following this period the patient is allowed to move freely. It is known that some grafts peel away from the graft site, and the surgery must be repeated.

FTS Engineering Answers is working with Moorfields Eye Hospital to investigate the problem using CFD.

We are helping to show that the presence of both liquid and gas in the anterior chamber during the motion, as a patient moves from horizontal to vertical, may causes a force that effectively drags the cornea graft off the graft site. Removing the air/gas reduces or eliminates the force. This discovery may potentially lead to a change of surgical procedure.

Contact FTS Engineering Answers to discuss your biomedical questions!

Turbocharger suppliers test their devices in idealized conditions i.e. straight inlets with no flow distortions. In reality, the real estate in an engine bay is limited at best which does not afford the luxury of ideal conditions. Subsequently, there is a need to know what effect this will have on performance.

FTS Engineering Answers has been working with OEMs to quantify these effects. Providing insight into not only the performance effects but improvements that can be made within the project scales.

In addition, FTS Engineering Answers continues to provide support on the following;

• By building detailed models of the compressor inlet, housing wheel and scroll, FTS Engineering Answers has investigated the cause of increased acoustics associated with different designs.
• Identified temperatures and thermal stress levels associated with the thermal heat up and cool down cycle to understand thermal fatigue issues of a twin turbocharger.
• Provided insight into the guide vanes of the turbine of a variable geometry turbocharger to understand potential hysteresis comparing the behaviour of the guide vanes as the open and close.

We are able to support our clients with a range of automotive packaging activities, contact FTS Engineering Answers to discuss your questions!