Clean Fuel – Keep Running

  Donaldson Filtration Solutions |  2017

Exploring the challenges to consistently delivering clean fuel to engine’s fuel injection system, and how to overcome challenges, with large focus on handling fuel prior to being pumped into vehicle

  • How evolving diesel engine technology is driving the need for cleaner fuel (HPCR fuel injection systems operate upwards of 40,000 psi – require very clean fuel to operate as-designed for their entire service interval)
  • Organic fuel contamination:
    • Hard particulate (dirt) picked up during transport (pipelines, terminals, trucks) and from tanks
  • Inorganic fuel contamination
    • Anything carbon-based - typically hydrocarbons with various chemicals attached, created by various sources (lubricity improvers, cold flow improvers, biodiesel, corrosion inhibitors, etc); fuel additives can become insoluble causing fuel instability if dosed at the wrong levels or under the wrong conditions
  • Most fuel delivered to tanks 500-1000 times dirtier than what is allowed in injector systems
  • Fuel should first be filtered in bulk storage tank to cleanliness level of ISO 14/13/11
  • Most OEMs meet emissions standards with on-engine technologies (like HPCR, which carefully controls amount and timing of fuel that is injected into cylinder, and exhaust gas recirculation (EGR)) and exhaust after-treatment solutions (like diesel particulate filters (DPFs) and selective catalytic reducers (SCR) which reduce particulate matter and NOx)
  • Diesel production
    • Oil – light, dark, sweet or sour (more sulfur=more sour); 15% of barrel goes to production of diesel
    • At refinery, oil is placed into crude distillation unit where it is repeatedly heated under various pressures to split “heavy” from “light”; catalysts can also be used to manipulate chemistry of fuel
      • Ex. to meet large petrol demand, refineries treat heavier streams to turn them into lighter fuels which are then stripped of sulfur and nitrogen; to raise octane number, fuel is then sent to reformer, where large amounts of hydrogen are produced as by-product
    • Hydrogen is used in hydrotreater with heat and catalysts to remove sulfur from diesel stream
  • ULSD requires heightened use of additives, and cleanliness specifications require use of tighter filtration efficiencies (beta ratio) – not a good combination
    • Filters are plugging with soft organic material (not hard particulate)
    • Filters designed in lab to capture hard particulate, not soft matter
    • Instances of filters plugging more than 1000 times faster than normal
    • Numerous papers published about injector deposit problems since removing sulfur – very possible could be same substance plugging filters
  • Why didn’t filters clog before?
    • Filters may not have been efficient enough to catch smaller matter (6 micron and less vs. 2-3 microns)
  • Cause?
    • Additives unstable? Under what conditions? Old phenomenon caused by tighter filter or new phenomenon caused by something else? Does filter media play a role?
    • Do properties of fuel change downstream of the filter once organics are captured? If they are captured, will injector deposits disappear?
    • Storage vessels as potential cause of contamination; importance of using filters and breathers on storage tanks
  • Cleanliness levels changing and getting more complex to meet
    • Around 1100 hydrocarbon chains used to drive engines – a high percentage non existent in the 80s, and modern engines technologies are completely different
    • Clear and bright standard no longer applies – lower limit of human visibility is 40μm – “fact is that modern High Pressure Common rail injectors are not very fond of particles greater than 2 μm”
    • ISO 4406 standard: permits differentiation of the dimension and distribution of particles allowed in fuel – identified by measuring number of particles 4, 6, and 14 microns and greater in one mL of the system sample; range between upper and lower limits for each scale number is a factor of 2; target cleanliness is ISO 14/13/11

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