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Sealing and Shielding

The technology of providing tight and perfect closure. Parker engineered seals and sealing systems provide safety and enhance equipment performance.
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  • Sealing and Shielding Knowledge Base

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When designing a gland in which an O-ring or elastomeric seal is the desired sealing component, there are several aspects that need to be considered. A perfectly designed seal with the right material, ideal compression, gland fill and stretch can have inadequate sealing capability if the surface finish of the hardware is neglected. This blog discusses the ideal surface finish requirements for both the application and testing of seals.

Consider these photos of metal surfaces. At first glance, all three may appear to be identical, but looking closely, the main difference is surface finish. Figure 1 illustrates the appearance of surface finish as it will be discussed.

 

Ideal Surface Finish Recommendations For Optimum Sealing Performance_Figure 1 magnification_Parker O-Ring & Engineered Sealing Division

  Figure 1: Left to Right: 500x magnification of 16µin RMS, 32µin RMS, 63µin RMS

 

Surface finish, as pertinent to seal design, is the measurement of the roughness of the two hardware faces compressing the O-ring or seal. That is why it is sometimes referred to as “surface roughness” as well as surface finish. Maintaining proper surface finish of these two surfaces is essential to obtaining a good seal. Table 1 outlines the basic guidance suggested in the ORD 5700 O-Ring Handbook.

table { width:100%; } table, th, td { border: 1px solid black; border-collapse: collapse; } th, td { padding: 12px; text-align: left; } #t01 tr:nth-child(even) { background-color: #eee; } #t01 tr:nth-child(odd) { background-color: #fff; } #t01 th { background-color: navy; color: white; }     Static Dynamic Liquid 32µin RMS 16µin RMS Gas or Vacuum 16µin RMS 16µin RMS
 Table 1: Surface finish recommendations

 

The requirements for sealing gas and vacuum are more restrictive than a liquid due to gas’s ability to find passage through very minute pathways on a hardware surface. Some estimates are that the viscosity of air is 53x to 55x less than that of water, which equates to about 53x more volume of air passing through the hardware indentation than water would. 

For static seals, Parker recommends using a surface roughness value not to exceed 32  µin (32µin RMS) when the seal involves liquid and a maximum of 16µin RMS when the seal involves gas.

If a surface is too rough against a static seal, the O-ring may have difficulty conforming to surface imperfections causing leakage.  Durometer of material can play a role in overcoming surface finish. The softer the material, the more it will fill in the peaks and valleys of the sealing surface, however, this may be at the detriment of other sealing properties, such as contact pressure, compression set resistance, extrusion resistance, or  durability.

For static sealing, consideration of the method used to produce the surface finish can certainly play a role and potentially offer improved sealing margin. Methods such as lathe or some other machining technique that produces tool marks parallel to the groove can be sealed most effectively and in certain situations may seal at roughness values greater than recommended. Other methods, such as end milling or routing, produce tool marks perpendicular to the groove and may be too deep for the O-ring to make full contact which could result in a leak path. In this situation, the recommended roughness values should not be exceeded.

For dynamic seals, the shaft or bore should have a surface finish between 8µin and 16µin RMS. This range of peaks and valleys on the hardware serves the purpose of holding the lubricant against the O-ring and ultimately minimize friction and wear damage. 

Surface finishes above 20µin will cause abrasion on the O-ring surface, and no amount of lube will prevent the O-ring from wearing. Surfaces which are better than 10µin will result in the lubricant being wiped away, which thereby increases friction and accelerates wear over the life of the seal.

 

Ideal Surface Finish Recommendations For Optimum Sealing Performance_molded component_Parker O-Ring & Engineered Sealing Division Figure 2 Illustration of mismatch on a molded component.

 

Questions come from customers with respect to hardware mismatch, surface porosity, and air or helium testing. Each of these questions often simplify down to the same guidance which has been outlined above. Figure 2 illustrates the mismatch that can be present on a molded housing. While there is not a hard and fast rule for overcoming mismatch, application experience has found success with limiting the step to a maximum of .003”. Like mismatch, surface porosity is another application specific hardware challenge that can be difficult for a seal to overcome. A general rule of thumb is for the maximum porosity size to be less than half of the contact width of the compressed seal in the least material condition. Lastly, a seal designed to contain fluid which is failing an air leak test often has the root cause of leakage due to surface roughness. This comes back to the reality that air and gas are a much more difficult sealing medium than a liquid and a smoother surface finish can often improve this condition. In some instances, mismatch and surface porosity can be overcome with a custom designed seal, but it will not be possible for a custom designed fluid seal to pass a gaseous leak test when the surface finish is the cause of leakage.

If you have additional questions about surface roughness, please visit our website and chat with our support team or reach out to one of our application engineers at OESmailbox@parker.com. 

 

Surface Roughness_Dorothy Kern_applications engineering lead_Parker O-Ring & Engineered Seals DivisionDorothy Kern, applications engineering lead, Parker O-Ring & Engineered Seals Division

 

 

 

 

Matthew Frye, product design engineer, Parker O-Ring & Engineered Seals DivisionMatt Frye, product design engineer, Parker O-Ring & Engineered Seals Division

 

 

 

 

 

 

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table { font-family: arial, sans-serif; border-collapse: collapse; width: 100%; } td, th { border: 1px solid #dddddd; text-align: left; padding: 8px; } tr:nth-child(even) { background-color: #dddddd; }

Ideal Surface Finish Recommendations For Optimum Sealing Performance

23 Feb 2021

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 If the words “Fire Seal” bring to your imagination a Sea World show gone terribly wrong, then you probably won’t be interested in this blog. But, for anyone associated with the field of aviation, you’ll recognize a crucial element of aircraft safety. Fire Seals are barriers located within an aircraft nacelle that, in the event of an engine fire, work to keep it contained within the immediate area and deny it the oxygen it needs to propagate. This provides the opportunity to safely shut down the engine or APU.

 

Aircraft engine safety

Few things worry the cautious traveler more than the idea of an aircraft engine fire. After all, it’s not like you can pull over 6 miles above the ground and call Triple-A. But, the reality is that without fire, a flight would be impossible. It is the controlled burn of fuel within the engine that generates the thrust necessary for flight. So, what those burdened with ensuring aircraft safety focus on is the prevention, detection, and suppression of unwanted engine fire. To combat this, aircraft are designed with redundant systems for fire detection which alert the flight crew to engage in appropriate countermeasures. These include cutting off fuel to the compromised engine and activating fire extinguishers. These are examples of active measures for fire control.

Fire seals fall into the category of passive systems. Passive systems are always in place and require no external engagement to function.

Fire seals typically feature a composite structure. A flame-resistant elastomer is layered with a fire-resistant fabric which helps to maintain the structural integrity of the seal for a specific period of time. Typical materials used are silicone, aramid fabrics, ceramic, or other inorganic fabrics. Seals are typically molded for finite lengths (typically < 12 feet long) and can be spliced to meet longer length requirements or irregular geometries. Intricate custom shapes are possible employing salt core molding techniques.

 

Typical configurations include:

  • P-seals

  • Bellows

  • Diaphragms

  • Omega seals

  • Gaskets

  • Custom shapes

How Fire Seals Contribute To Overall Aircraft Flight Safety - applications in enginer - Parker Hannifin

Governing specifications

The main specifications governing fire seals are ISO 2685 and AC20-135. These documents define the test methods and acceptance criteria for evaluating seal performance. Seals are evaluated by their ability to survive exposure to a 2000 degree flame for a specified period of time. Components can be classified as either fire-resistant (5 minutes) or fireproof (15 minutes).

Parker's Engineered Materials Group supplies fire seals through our Composite Sealing Systems Division (CSS), headquartered in San Diego, CA. Our seals have been tested by a third-party laboratory and have been proven to meet the requirements of the governing specifications. Testing consists of exposing a production-representative component to a set of application-specific conditions that may include pressurization, airflow, and vibration, all while exposed to a calibrated 2000°F flame. The component must not allow any burn-through during the entire test and should not self-ignite after the burner is removed.

Parker is a major supplier to many major aerospace OEMs. To learn more about how we can help support your production, reliability, and safety goals, contact us.

Learn more by watching our video on all our sealing solutions for aerospace.

 

 

How Fire Seals Contribute To Overall Aircraft Flight Safety - Brian Alessio, Parker HannifinArticle contributed by Brian Alessio, business development engineer, Engineered Materials Group, Parker Hannifin.

 

 

 

 

 

 

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How Fire Seals Contribute To Overall Aircraft Flight Safety

18 Feb 2021

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Thermal Gels or Gap Filler Pads? Top 6 Things You Should Know - Feature Image - Parker ChomericsThermal interface materials are used to eliminate air gaps or voids from adjoining rough or un-even mating surfaces. Because the thermal interface material has a greater thermal conductivity than the air it replaces, the resistance across the joint decreases, and the component junction temperature will be reduced.

Two principal “gap filler” thermal interface materials prevalent on the market today are thermal gels – also known as dispensable gap fillers – and gap filler pads.

So, which one should you select for your application? Here are the top 6 things you need to know:

1. Conformability

Both thermal gels and thermal gap filler pads are highly conformable, but the maximum configurability of a gap pad is less than that of a gel due to its solid structure. Dispensable gels provide maximum conformability because they can be dispensed in near infinite shapes and patterns.
 

2. Automation  Both thermal gels and gap filler pads offer application via automation, but thermal gels get the significant advantage here because dispensing systems are quite versatile. While pad placement can be automated to an extent, the equipment and fixturing required to do so is typically quite specialized and may not be readily adapted from one job to the next.
  3. Cost When it comes to cost, thermal gap filler pads require less up-front capital because there is no dispensing equipment to invest in. However, our experience with multiple applications suggests that about 5,000 parts per year is the threshold where it becomes more economical to use thermal gels and an automated dispensing system versus pads that are manually applied for the same application. 
  4. Precision Precision and accuracy are important, and the edge might go towards gap filler pads in this instance. Pads can be cut to the exact shape of your part, whereas the thermal gel takes the shape of how it spreads out once it is compressed. But as usual, the specific application will drive the degree of precision required, as well as determine the acceptability of whether the gel material extends beyond the surface of what it is being applied to.
  5. Throughout Speed in production is application-dependent, but recently, one of our customers was considering a switch from pads to gels and ran a test of both materials to gauge the difference in throughput. Their study revealed that it required an operator 18 seconds to apply one pad, including handling the pad, placing it properly and then moving on to the next component. Using a dispensable gel and an automated process, those same steps required only four seconds.
  6. Technology advances

Gap filler pads have long been the go-to choice for many design engineers, but recent advances in thermal gels, which are highly conformable, pre-cured single-component compounds, can provide superior performance, a greater ease of manufacturing and assembly, and a lower cost in certain high-volume applications; particularly as electronic design applications get smaller, more fragile and more complex.

Looking to learn more about thermal gap pads and dispensable gels? Download our new white paper Thermal Interface Materials: Choosing Between Gels and Gap Filler Pads now!

In this white paper, you’ll learn about the two general types of thermal interface materials – gels (or dispensable gap fillers) and gap filler pads – which are used by design engineers for displacing air voids and ensuring proper heat transfer, as well as:

•    Heat transfer fundamentals refresher
•    Intro to gap filler pads and thermal gels
•    Pads vs. gels – understanding key differences
•    Conclusion and recommendations

This white paper analyzes and draws conclusions about key performance and manufacturability characteristics in both gap pads and new advances in gels. Download it today!
 

Thermal Interface Materials: Choosing Between Gels and Gap Filler Pads - Download White Paper - Parker Chomerics

 

 

 

 

 

 

 

 

 

 

Thermal Gels or Gap Filler Pads? Top 6 Things You Should Know - Jarrod Cohen - Parker Chomerics

 

 

This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics.

 

 

 

 


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Selecting a Thermal Gel or Thermal Gap Pad – Your Questions Answered (Part I)

Selecting a Thermal Gel or Thermal Gap Pad – Your Questions Answered (Part II)

How to Identify Quality Thermal Gap Fillers in Four Steps

Overcoming Challenges of Fully Autonomous Vehicles

Thermal Gels or Gap Filler Pads? Top 6 Things You Should Know

11 Jan 2021

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Challenges of Commercial Vehicle Electrification - Yellow electric bus being charged at a station - Parker HannifinIn 1933, Kenworth Motor Truck Co. became the first American truck manufacturer to introduce the Cummins 4 cylinder, 100 hp, HA4 model diesel engine as standard equipment. By 1938 the first two-stroke diesel powered bus was introduced. In 1940, Cummins was the first diesel engine manufacturer to offer a 100,000-mile warranty. By the 1950s, diesel engines had virtually replaced gasoline engines in commercial trucks. Since 1997, engineers of diesel engine manufacturers have risen to the challenges of meeting new and more stringent limits for particulate matter (PM) and nitrogen oxides (NOx) and increasing the fuel efficiency of the engine. 

As the heavy truck and bus market continues to evolve, engineers need to meet new challenges by identifying and adopting innovative technologies. 

Challenges of Commercial Vehicle Electrification - Transportation Trends White Paper - Parker Hannifin

 

 

Download our Transportation Trends white paper and learn how Parker is helping heavy truck and bus manufacturers respond to sustainability trends.

 

 

 

Consider the trend of commercial vehicle electrification. Driven largely by concerns over emissions and environmental impact, the vehicle electrification market has grown substantially. And enhanced vehicle battery technologies are the key to driving truck and bus electrification. 

Challenges remain, however, before these systems will prove feasible and practical over the long term.  

Lithium-ion batteries have been the primary solution for electric vehicle manufacturers because they have higher energy densities than lead-acid or nickel-metal hybrid batteries. Li-ion batteries also offer attractive features such as low self-discharge and considerable energy storage, or battery capacity. Yet, there are still many barriers for the vehicle electrification market to overcome. Among these barriers are cost, weight and range, safe storage and thermal management. 

 

Electric vehicle battery technology 

A lot of research is being conducted to identify alternative battery chemistries and reduce the use of cobalt. Although cobalt is ideal for rechargeable batteries because of its thermal stability and high energy density, a problem is that it is almost exclusively mined in the Democratic Republic of Congo, an unstable country that has been charged with numerous human rights violations. 

Increased ethics concerns and growing costs have universities, private companies and the U.S. military aggressively researching alternatives to cobalt. 

  • The U.S. Army is focusing on a new electrolyte design using silicon particle anodes in conjunction with lower cost transitional fluorides. The solid polymer electrolyte provides greater stability, even at higher temperatures, overcoming previous heat concerns. 
  • IBM is researching a cobalt- and nickel-free cathode material and a safe liquid electrolyte with a high flash point. 
  • Research at Washington University in St. Louis on potassium-air batteries has shown that the effective selection of the electrolyte in battery chemistries can double their capacity.  
  • Engineers at the McKelvey School of Engineering also have developed a borohydride fuel cell that operates at double the voltage of conventional hydrogen fuel cells.  
     
Battery safe storage 

Since it is critical to protect the integrity of a battery from dirt and water, proper sealing is a key design consideration. Electric vehicle battery covers pose unique sealing challenges due to the significant size of the perimeter of the battery, as well as the aggressive performance requirements. Batteries are assigned Ingress Protection (IP) ratings to specify the degree of environmental protection from solids and water that might otherwise enter the enclosure and cause damage. Sealing products from Parker O-ring and Engineered Seals and electronic materials from Parker Lord prevent ingress between battery covers and housings—for both serviceable and non-serviceable batteries.   

 

Watch this webinar to learn more:

View our webinar on Serviceability of EV Battery Packs

 

Electromagnetic interference (EMI) 

Challenges of Commercial Vehicle Electrification - EMI Shielding - Parker HannifinElectromagnetic interference is a concern because electric vehicles have multiple battery cells, converters and powered electronics (ADAS, LiDAR and infotainment screens). The signals from one could interfere with those of another. The good news is that special EMI shields now exist to help contain the magnetic signals within the components. 

Among them are seals that are made of electrically conductive elastomers and form-in-place (FIP) conductive gaskets and even plastic pellet materials for housings 

 

Thermal management 

Challenges of Commercial Vehicle Electrification - Thermally conductive gap filler pads - Parker HannifinThermal management tops the list of priority concerns. Parker offers several material innovations in this area that can stand up to excessively high temperatures and are flame-retardant to prevent a catastrophic thermal event, including thermally conductive gap filler pads and thermally conductive structural adhesives  

In addition, there are air ventilation panels that dissipate heat and provide EMI shielding. 

 

 

  Conclusion 

Electric vehicle battery technology is a significant, trending topic in the bus and commercial vehicle market. While lithium-ion is currently the most dominant type of EV battery, engineers are driven by concerns over emissions and environmental impact to find a higher performing alternative. Reduced weight, improved storage, and better thermal management are among the features that engineers are hoping to work into EV batteries.  

 

Challenges of Commercial Vehicle Electrification - Download our Transportation Trends White Paper - Parker HannifinTo learn more about how Parker is helping heavy truck and bus manufacturers respond to sustainability trends, read our Transportation Trends White Paper.

 

Challenges of Commercial Vehicle Electrification - Christopher Overmyer - Parker HannifinThis article was contributed by Christopher Overmyer, Senior Field Application Engineer, Parker Engineered Materials Group 

 

 

 

 

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Improving Efficiency of Diesel Truck and Bus Fleets - Line of buses driving along highway - Parker HannifinClean energy consultancy Gladstein, Neandross and Associates, in its recent report on sustainable fleets¹, predicts another decade of diesel-powered heavy trucks leading long-haul. Diesel efficiency and emissions reductions are important areas of research as broader trends toward sustainable fleet adoption accelerate. 

One new technology to the diesel market is cylinder deactivation (CDA). This technology has been commercially applied to the automotive sector as “Displacement on Demand” to improve fuel economy in V-8 engines. In the diesel market, CDA not only helps with fuel economy, but it also helps to increase exhaust temperatures and reduce engine-out nitrogen oxides (NOx).  

 

Improving Efficiency of Diesel Truck and Bus Fleets - Download our transportation trends white paper - Parker Hannifin

 

Read our Transportation Trends White Paper to learn more about how Parker is helping heavy truck and bus manufacturers evolve to sustainability trends,

 

 

 

 

CDA would be used when the diesel engine runs below its normal operating temperatures, such as in a cold start or when the engine is under light loads (i.e., idling or cruising at highway speeds). In these conditions, the system deactivates some of the cylinders to increase the load on the remaining cylinders. When this occurs, more fuel per injection is required and this produces more heat in the engine block. This, in turn, raises the exhaust gas temperature to an appropriate operating level to activate the diesel particulate filter (DPF) burn off cycle. Successful development and commercialization of CDA technology would help the industry meet 2024 emissions standards. 

Another major advancement has been in the development of ducted fuel injectors. Developed by Sandia National Laboratory’s Combustion Research Facility, the ducted fuel injectors offer many benefits. They clean emissions like soot (another potent climate change chemical second only to carbon dioxide) from vehicle fuel, and they represent an inexpensive transition by working well with conventional diesel fuels. They can easily be retrofitted into existing engines, require no after-treatment systems, and have the potential to lengthen oil change intervals. 

The ducts are small tubes that are mounted to the underside of the cylinder head near the injector nozzle. Researchers continue to search for appropriate high-temperature alloys for those tubes without substantially increasing costs. 

 

Thermal energy recovery systems 

A desire to improve energy efficiency and cut greenhouse gas emissions has led to considerable interest and research in various waste heat recovery techniques. Topping the list of options are thermoelectricity and Rankine Cycle. Rankine Cycle offers the greatest potential due to its higher cycle efficiency. 

Rankine Cycle is not a new concept. It has been widely employed in large-scale power plants for years. But it has yet to be fully implemented for heavy-duty trucks and buses.  

The cycle works by recovering wasted heat from the engine through an intermediate heat transfer loop that is filled with a working fluid. The fluid captures some of the energy from the waste heat source. The fluid is often water, but with organic Rankine cycles, a higher molecular mass fluid with a lower boiling point is used to reduce the amount of heat needed for energy recovery.  

Despite its tremendous potential, some challenges remain, such as limitations of heat available in the heat source, heat rejection constraints, backpressures during the recovery process, and safety and environmental impacts of the chosen working fluid.  

The beauty of this form is that its heat source--exhaust waste heat--exists on all current engines on the market. 

 

Creating a more aerodynamic truck 

Today there is a large array of aerodynamic aids available for heavy-duty trucks and trailers, all designed to increase efficiency by reducing drag and fuel consumption by as much as 12%. 

Some of the more popular options include front and underbody deflectors, side skirts, rear diffusers and boat tails. Companies have experimented with the specific design and rigidity of such aids to further enhance aerodynamic performance. While all of these can provide some benefit, the key is to identify the right combination of aids that provides enough fuel savings to offset the added costs. 

Low-rolling resistance tires also improve truck aerodynamic performance by reducing resistance caused by the tires rolling on the highway’s surface, often through tread depth and design. To date, however, while more fuel-efficient truck tires have garnered interest because of their ability to minimize energy and boost fuel economy, their lower life cycles cause concerns for bottom line-oriented owners and operators.  

Another trend in commercial trucking is the replacement of dual tires with super single tires. The advantage of reducing the number of tires on a large rig is minimized friction and resistance. However, safety concerns arising from what happens when a tire blows are keeping most fleets from making the switch. 

 

Alternative fuel sources 

Electric (battery or fuel cell) is not the only alternative energy source being explored, as companies continue to research the potential of various renewable fuels, like renewable natural gas (RNG), biodiesel and renewable diesel (RD) which are efficient as fuel sources while producing inherently lower greenhouse gas emissions. 

California leads the way in renewable energy research with herds of dairy cows already powering fleets, homes and factories throughout the state. An especially promising development is the recycling of dairy cow waste to produce methane--an option that creates a negative carbon footprint. Known as biomethane, it is an attractive tool for battling climate change.  

Beyond dairy waste, RNG can come from other sources of manure, landfills, as well as wastewater. The advantage is that it can be easily exchanged with natural gas drilled out of the ground, minimizing the need to overhaul natural gas engine designs.  

Biodiesel (B) and renewable (R) diesel, both of which can be made from similar feedstocks, recycled cooking oil (i.e., oil used to make French fries), oil from algae, soybeans, and other oilseed crops, are also attractive alternatives for existing diesel engines. Not only are they carbon neutral, but, like RNG, their use does not necessitate a diesel engine modification. However, biodiesel blends above 20 percent (B20) will require use of higher performance fluorocarbon sealing compounds. Learn more in our Seal Materials for Biodiesel blog.

One of the concerns for renewable diesel is the choice of which feedstock is used. Palm oil feedstock, for example, has been linked to significant land use impacts, including deforestation, which results from allocating land to grow and farm the palm oil. 

Yet another alternative fuel is ethanol. One company recently completed tests showing that its system matched the torque and power of a commercial diesel engine using ethanol instead of diesel fuel, delivering over 500 hp and 1850 ft lb. of torque without additional aftertreatment. 

There are several points of concern for fleets that operate Class 4 through Class 8 vehicles with multiple power sources, i.e., some diesel, some natural gas, some electric, etc. Among other things, they will face “right to repair” and maintenance challenges as technicians must be sufficiently trained in the repair of multiple power-source vehicles. For example, mechanics working with electric systems need to be well-versed on sensors and how to properly ground them to avoid serious injuries. In addition, a wide variety of parts may need to be inventoried to maintain an array of engine types.  

Another point of concern is the training of first responders—not only the emergency responders, but also tow/salvage operators. Diesel, natural gas, and electric engines require different approaches to putting out fires in a roadway vehicle crash or in a facility where electric vehicles are charged.  

 

Conclusion 

When considering options for lessening environmental impact, total cost of ownership still plays a role in ultimately determining which technologies will be adopted and to what extent. The ability to make these innovations affordable, safe, reliable, and sustainable is the key to the future of a sustainable transportation model. 

 

Improving Efficiency of Diesel Truck and Bus Fleets - Download the transportation trends white paper - Parker HannifinTo learn more about how Parker is helping heavy truck and bus manufacturers evolve to sustainability trends, read our Transportation Trends White Paper.

 

Improving Efficiency of Diesel Truck and Bus Fleets - Christopher Overmyer - Parker HannifinThis article was contributed by Christopher Overmyer, Senior Field Application Engineer, Parker Engineered Materials Group 

 

¹ Cision PR Newwire - State of Sustainable Fleets Report Released, Finds Sustainable Vehicle Technologies and Fuels Are Growing Across All Sectors

 

 

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Overcoming Challenges of Fully Autonomous Vehicles + Vehicles with wifi connection driving on busy highway + AutomobileAs the automotive industry moves toward more automated, connected vehicles, engineers are challenged to identify technologies that can process and transfer large volumes of data in real-time without adding significantly to the price of the vehicle. 

For example, Level-5 autonomous driving (meaning the vehicle is capable of safely performing all driving functions on its own) requires a combination of: 

  • radar  
  • Lidar 
  • video camera technology; and, 
  • high-performance, on-board computer systems to perform highly complex functions. 

Accommodating all the necessary cameras, sensors and electronic control units (ECUs) that enhance connectivity and ensure autonomous vehicle safety has proven to be problematic due to the resulting electromagnetic interference (EMI) and excess heat being generated by the growing complement of electronic devices, including advanced driver assistance systems (ADAS).  

Parker is aggressively responding to both challenges with innovative shields and thermal management technologies that contain the electromagnetic noise and transfer heat away from critical components. 

 

Overcoming Challenges of Fully Autonomous Vehicles - Download TransportationTrends White Paper - Parker HannifinTo learn more about Parker solutions for ADAS, autonomous and connected vehicles, read our Transportation Trends White Paper.

 

 


 

 

 

Addressing EMI concerns 

EMI pollution not only interferes with communications, but it deteriorates the durability and proper function of electronic equipment. This has opened the door to numerous technology advances in the form of EMI shielding.  

EMI shielding uses materials to act as barriers to reflect and/or absorb electromagnetic radiation. Although metals are great for the task and have been used extensively to date, a major drawback is added weight. Other concerns include costs and vulnerability to corrosion. 

In 2018, Parker Chomerics introduced its innovative CHOFORM 5575 silver-aluminum filled form-in-place EMI gasket, which is a moisture cure silicone system that provides reliable EMI protection for packaged electronic assemblies. Robust enough to provide corrosion resistance and able to endure high-temperature applications, it is ideal when isolation and complex cross-section patterns are required, which is often the case with ADAS modules and telecommunications boxes. 

In recent years, the market has witnessed the emergence of more flexible polymer components that are lightweight and corrosion-resistant and offer superior electrical, dielectric, thermal, mechanical, and magnetic properties, which are highly useful for suppressing electromagnetic noise. Even newer are flexible polymer composites comprised of metals and various forms of carbon nanofillers, such as:  

  • carbon black  
  • carbon nanotubes  
  • graphite  
  • graphene, and 
  • graphene oxide  

Among these options, graphene has thus far shown the most promise and is a focus of Parker’s ongoing R&D efforts. 


Advances in thermal management 

Challenges abound regarding thermal management, which includes thermal connectivity and the cooling of electrical components. Not only are engineers working to manage heat from the large array of electric components required to make today’s cars more connected and autonomous, but they are doing so in confined spaces of the vehicle where temperatures are often elevated. With components under the hood reaching ambient temperatures as high as 221°F (105°C), there is an added burden on thermal management solutions. 

Equally challenging is controlling noise associated with a cooling system, such as the case with any type of fan. Today’s discriminating automobile purchaser expects a quiet driving environment uncompromised by the whirring of fan blades. That means solutions must be identified that generate little to no noise and possess high thermal conductivity and low interface resistance with a low-pressure bond.  

While there are many possible Thermal Interface Materials to choose from, the most pursued today in the automotive sector are dispensable thermally conductive gap fillers (gels), which are also commonly referred to as Gap Filler Liquids (GFLs). Proponents of thermally conductive gels tout the products’ softness and low viscosity that make them highly effective in managing heat and easy to use. 

Other engineers prefer thermal gap filler pads because of their high level of flexibility and enormous mechanical resistance. 

Parker continues to test new chemistries and advanced polymers that offer greater thermal conductivity. Parker Chomerics THERM-A-GAP™ GELs are examples of Parker’s success in developing products that are meeting growing demands for thermal management. The cross-linked gel structure provides superior long-term thermal stability and reliable performance without needing to be cured. Parker is currently the only company to provide a single component, fully cured conductive gap filler. 


Trends on the horizon 

On the horizon are new thermal absorbent materials with unique properties that can also absorb some of the EMI noise. 

Beyond the search for alternative materials, work also is being done with novel active heat sink designs, which are sealed miniature loops with liquid metal alloys, such as Galinstan. Connecting a heat source to heat sink has proven to be a highly efficient means for thermal cooling of electronic components while simultaneously having an electrically insulating effect. 

Other types of active cooling approaches also are gaining interest, including spray and jet impingement. With these designs, the vehicle’s AC loop is modified by adding a pump and integrating a spray chamber. One problem in the early designs, however, continues to be the added weight of the loop. 

In another test, two-phase cooling of the underside of automotive power inverters was investigated.  The study involved two pressure-atomized nozzles that sprayed antifreeze coolant at 190.4°F (88°C) on the bottom thick-film resistors. Early results are encouraging since this method resulted in cooler temperatures than those obtained using a commercially available heat sink. 

Still, other work is being done to modify the aerodynamics of a vehicle in recognition of the impact of convective cooling on thermal management. 

Cost remains a key obstacle. Parker’s contribution to the cost equation has been to simplify product designs as a means for lowering total costs. 


Adapting military applications 

Driving many of Parker’s advancements in the automotive sector are adaptations of technologies currently used for military applications. Lidar is an example of a technology once used exclusively by the military that is proving valuable for automobiles. Lidar is a method of measuring distances by illuminating the target with laser light and measuring the reflection with a sensor. Its advantage over traditional cameras is in its ability to function well even at night or on cloudy days. 

The military uses lidar to map out the terrain of the battlefield and to know the exact position of the enemy and its capacity. Lidar is a critical technology for the advancement of driverless military vehicles. The superior resolution produced by lidar is a result of its use of light pulses that have about 100,000 times smaller wavelengths than the radio waves used by radar. The speed and sensitivity of the lidar components, combined with the massive amount of data that is being processed, require specific material properties that optimize the accuracy, reliability, and durability of the lidar assembly. This is where Parker comes in, providing the specialized EMI shielding and thermal conductivity necessary to support the advanced lidar technology. 

Industry experts agree that it is a matter of when, not if fully connected, autonomous vehicles will become a reality. Some of the remaining challenges relative to EMI and thermal management have proven a bit more difficult than originally envisioned, but progress is being made in both areas to bring us closer to a new driving reality. 

 

Overcoming Challenges of Fully Autonomous Vehicles - Download the Transportation Trends White Paper - Parker HannifinTo learn more about Parker solutions for ADAS, autonomous and connected vehicles, read our Transportation Trends White Paper.

 

Overcoming Challenges of Fully Autonomous Vehicles - Daniel Chang - Parker Hannifin

This article was contributed by Daniel Chang, Global Automotive Market Sales Manager, Parker Chomerics Division. 

 

 

 

 

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