The Importance Of Additives In Today's Aviation Fuels

An article by Walter P. Chartrand

Aircraft technology continues to change and improve at an impressive rate, leaving many industry observers and the general public left to ponder the "flying machines" of the future.

By all indications, engines will likely become faster and smarter. And, much like the military, jet fuel will likely be used to support more than just the aircraft's engine. In fact, everything from hydraulic systems to climate control may rely on fuel to be operational. The challenge in that scenario, however, will be to maintain the fuel's performance at it goes from one extreme temperature change to another through the various applications.

Unfortunately, such efforts to improve the thermal stability of the fuel in those situations will come at the post-refining stage. The fuel refining process may very well have reached its peak potential in providing high-performance fuel for today's aircraft at an acceptable cost. Thus, the aviation industry is turning more of its attention to fuel additives and the benefits they provide in enhancing fuel performance.

Not surprisingly, fuel additives were once considered unnecessary, contributing nothing to the fuel's quality or performance. Most industry experts agreed that the best way to produce high-grade fuel was at the refining stage. And that was the case - to a point. Take, for example, the requirements of our U-2 or SR-71. These aircraft require "thermally stable" jet fuel. Yet, not only is there a very small amount of crude that will make thermally stable jet fuel, it is extremely expensive. Thus, additives are crucial in this instance. Fuel additives have come a long way in changing attitudes and garnering respect in all industries.

Today, fuel additives are used for any number of applications. Take, for example, those additives used to kill the microbial growth that breeds in the bottoms of fuel tanks. The fuel that went in the tank may have been the best quality the industry has to offer. But if there is any water at the bottom of the tank before it's filled, chances are Hydrocarbon Utilizing Microorganisms - or HUM-Bugs - are living in the tank and breaking down the fuel's quality. Without the proper fuel additive designed specifically to kill HUM-Bugs, the quality of the fuel suffers and leads to plugged fuel lines, deteriorating fuel-related parts and much more.

The same is true for anti-icing fuel additives. Once again, there are situations when the fuel begins as a high quality component. When exposed to low temperatures at high altitudes, water can come out of the solution and freeze -- even with the highest quality fuel. Anti-icing fuel additives are used to prepare the fuel for such a change and keep it from solidifying and adversely affecting engine performance.

Now, new fuel additive technology can clean turbine fuel and combustion systems, while stabilizing the fuel at high temperatures. Hammonds was recently introduced as the domestic distributor for BetzDearborn's Turboline FS 100 additive, which is considered the wave of the future. BetzDearborn is well known as a specialty chemical supplier to the refining and petrochemical markets, as well as an industry leader in high temperature process chemistry.

Combined with anti-oxidant and metal deactivator additives, Turboline is a multi-functional product formulated with the same proprietary BetzDearborn detergent technology used by the U.S. Air Force in their JP-8+ 100 program. In the military application, the detergent provides greater fuel heat sink capacity by allowing fuel temperatures to increase without degradation. Simultaneously, the additive has provided the military with reduced deposits in turbine engines relying on JP-8 and JET-A fuels, has cleaned carbon buildup in fuel system and combustion sections of turbine engines and has reduced hazardous waste disposal costs associated with cleaning aircraft parts.

Commercial aviation faces many of the same challenges that have plagued the military. As aircraft maintenance professionals will tell you, jet fuel can undergo significant changes when exposed to increased temperatures. Chemical reactions take place that result in gum formation and even color change. When this happens over a period of time, the exposure can result in carbon or coke deposits on metal surfaces inside the engine.

Fuel nozzles typically represent the highest temperature contact point for the jet fuel (greater than 300 degree F) and often carbon buildup can be seen at the face. This type of carbon buildup can lead to poor atomization and distorted fuel spray patterns in combustion sections that can cause increased levels of carbon and soot in the exhaust.

In these dirty systems, Turboline works by first shutting down reactions that cause carbon and coke buildup as the fuel is thermally stressed. Next, the detergent power of the additive begins binding to existing carbon-on-metal surfaces that, with high turbulent environments, creates a cleaning action as the additive flows through the systems. As such, the aircraft's engine operates as designed, leading to better operational performance.

Overall better performance is the number one objective. But reducing maintenance time is a close second. Fortunately, Turboline has managed to do both. In fact, two Florida law enforcement agencies can attest to that.

The Tampa Police and Hillsborough County Sheriff's Departments operate McDonnell Douglas and Bell OH-6A and OH-58 model aircraft. Both are powered with Allison T63-A-720 engines. And both departments provide air support for ground and water law enforcement units in the surrounding areas.

The Tampa Police Department performs its aircraft maintenance in-house, with inspections at 100 and 300 intervals. They also do a compressor wash once per week. The Hillsborough County Sheriff's Department contracts out its inspections at the same intervals and completes a compressor wash every 25 hours. Additionally, both operations have found it necessary to clean the fuel nozzle more often than anticipated, due to a build up of hard carbon or coke material.

After learning of the military's success with BetzDearborn's additive technology, both departments agreed to follow suit with the aid of Air Force personnel. Specifically, Tampa and Hillsborough established an untreated performance baseline of three months, and then compared treated performance with Turboline FS100. During that time, the Tampa Police Department alone logged more than 900 flight hours.

At a treat cost of 5.0 cpg for an equivalent time period, the results were outstanding. Both Tampa and Hillsborough reported having less soot and coke in the combustor, less coke buildup on the face of the fuel nozzle, longer maintained engine power levels and a nearly ten-fold increase in the interval between fuel nozzle cleanings. In fact, the Tampa Police Department went from cleaning fuel nozzles every 10 to 20 hours to more than 200 hours after using Turboline.

Hammonds experts recommend a fuel treatment level of 625 ppm, which equates to 80 ounces for every 1,000 gallons of fuel. Additionally, they recommend adding Turboline via proportional injection into the fuel. Those users with their own fuel farm system or fuel truck can use several appropriately-sized injectors systems, while smaller packages of the additive are available to batch treat 200 gallons of fuel for those who are away from home or who have smaller base operations.

For best results, Hammonds and BetzDearborn suggest continuous use of the additive, with a minimum of 70 percent of total engine hours recommended ensuring measurable results.

While Turboline FS100 is not currently certified by the Federal Aviation Administration (FAA), a supplemental type certificate is likely to occur in the future, as is OEM approval on all major engines and airframes. The additive, however, is available to public-use aircraft, and anyone wanting to operate non-public-use aircraft with Turboline can send a request to their local OEM and FAA contact.

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