Introduction
Much has been published during the past decade about air quality concerns and harmful atmospheric emissions discharged by current diesel engines equipped with DPF (Diesel Particulate Filter) technology and older diesel engines without such systems. While it is true that hydrocarbon burning diesel engines can and do add to the overall production of air quality emissions, it is not necessarily a finite fact that diesel fuel consuming equipment ‘must’ release excessive amounts of harmful unburned hydrocarbon fuel emissions.
Diesel engines in America burn significant quantities of refined crude oil petroleum and other organic products in the production of horsepower energy. However, diesel fuels consumed in an engine will not create excessive emissions IF the fuel is properly burned with sufficient amounts of excess air to create complete conversion of the individual components comprising the fuel. The fuel ‘burning efficiency’ of these engines determines the extent of harmful unburned hydrocarbon emissions emitted into the atmosphere.
Remember, crude oil is composed primarily of decayed plant and animal life (dead dinosaurs and other organic materials from past millennia) so the diesel fuel refined from crude oils will contain multiple amounts of material that can potentially be difficult to burn. Additionally, crude oils are unique compounds in that they contain all of the known elements in the elemental chemical charts. Refining removes most of the really harmful elements, but the physical structure of finished products can be difficult for engines to deal with.
Modern engine fuel systems are manufactured with special fuel delivery components that require constant and sophisticated efforts to maintain them in good working order. Today’s diesel engine fuel pumps create enormously high operating fuel pressures and the exceptionally fine fuel injector holes and tolerances are extremely sensitive to the slightest amount of dirt, debris, moisture and other potential contaminations typically found in diesel fuels. If not kept exceedingly clean and in proper working order, these systems will exponentially increase operational issues and dramatically increase the creation of unburned hydrocarbon emissions at all levels of operation.
Another factor directly influencing the creation of excessive diesel fuel emissions is the cold weather operation of diesel equipment. As the temperature drops, the diesel fuel becomes harder to pump through the fuel delivery system (especially Common Rail Injection Systems). These changes in fuel consistency (i.e. viscosity and flow ability) are made more difficult by the water content and other physical contaminants present in the fuel along with today’s storage tank and piping configurations.
These conditions deliver less than optimum fuel to the engine and cause improper mixing of the air with the fuel in the combustion chamber necessary to achieve the best stoichiometric air/fuel ratios during each engine combustion cycle. This will increase unburned hydrocarbon and related fuel emissions. The following article further discusses environmental emissions from diesel fueled engines and how to better reduce the production of these air quality concerns through the application of the ‘right’ diesel fuel additives.
Diesel Fuel Composition Impacts
Crude Oil Impacts – Crude oils processed today are much heavier and contain more contaminants than those of past decades. Therefore, the diesel fuels of today are considerably different from those previously produced. Today’s refining techniques allow the fuel producer to convert 100 percent of every barrel of crude oil entering the refinery into gasolines, diesel fuels and other petroleum derived products. This means the heavier materials in crude oil that were once discarded, today comprise a significant part of the finished fuels produced in the refineries.
Modern production technology has made it possible for refiners to handle these more difficult and complicated crude oils (such as the Canadian Tar Sand Crudes and Western America Shale Crudes). But, the finished fuels, particularly diesel fuels, tend to contain more varied chemical components that can cause higher and more severe DPF deposits and air quality emission issues.
Fuel Properties – These diesel fuels are also much more prone to more rapid degradation and instability which causes increased fuel related deposits and poor fuel combustion. This leads to increased DPF issues, increased smoke and higher unwanted post combustion exhaust emissions.
Today’s diesel fuels also tend to hold more moisture (water content) which increases the presence of naturally inherent salts leading to internal fuel injector deposits that can cause fuel injectors to function poorly or ‘stick’ and seize. Again, poor operation of the fuel injector system will increase fuel related combustion area deposits causing incomplete combustion, negatively impacting DPF cleanliness and its operational efficiency increasing the frequency of DPF regens.
Since diesel fuel is used as the cleaning agent during DPF REGENS, increased DPF REGEN frequency results in increased fuel consumption without any additional horsepower or work accomplished.
Other diesel fuel physical parameters that impact DPF REGENS and exhaust emissions are the fuel Distillation Range (IBP – initial boiling point and other boiling temperatures including the EP – end point temperature), the Engine Cetane Number and the HFRR fuel lubricity value.
Diesel fuel Distillation Range is determined by:
(a) The crude oil processed into the diesel fuel
(b) The refining processes used to manufacture the diesel fuel
(c) The fuel component blending that occurs within the refinery rundown lines and storage holding tankage, any blending or mixing of different fuels by the intermediate fuel supply terminals receiving the refined fuels and any mixing of different supply sources or blending of light distillates into the diesel fuel by the final fuel distribution companies prior to delivery to the fuel users
Higher IBP temperatures make the diesel fuel harder to ignite and start to burn. Lower IBP temperatures result in the diesel fuel igniting and burning too quickly before the engine pistons reach TDC – top dead center during the combustion cycle. Either of these situations can cause increased emissions.
Fuel Properties – The Engine Cetane Number of a diesel fuel plays an even bigger role in the creation of DPF deposits causing operational issues and unwanted unburned hydrocarbon and smoke emissions. Low Engine Cetane Number diesel fuels (particularly below 50) increase the ‘ignition delay time’ from the time of fuel injection to actual ignition of the fuel. This results in increased smoke emissions.
The electronic ignition controls on newer diesel engines help to improve operational efficiency with slightly lower Engine Cetane Number diesel fuels than the engine is designed to utilize. But, these electronic engine controls cannot effectively and completely modify the engine timing adequately to account for significantly low and varied Engine Cetane Numbers routinely seen in the fuel marketplace today.
Higher Engine Cetane Number diesel fuels (substantially above 50) decrease the ‘ignition delay time’ which allows the diesel fuel to ignite at the proper time and begin burning well before TDC – top dead center occurs in each engine cylinder. If a higher Engine Cetane Number diesel fuel is properly injected (with a balanced spray pattern) at the correct time during the combustion cycle, the diesel fuel ignites at the proper time and the fuel will burn evenly and more completely without any significant visible smoke (as long as the diesel fuel is of good quality and consistent physical characteristics).
Since the entire fuel injection/delivery system (pumps and injectors) is lubricated by the diesel fuel, the fuel Lubricity Value must be adequate to insure that effective lubrication is always present in the system. Thus, diesel fuel Lubricity Value as measured by the HFRR test (High Frequency Reciprocating Rig) plays a very important role in the creation of DPF REGEN activity and the extent of unwanted exhaust emissions.
In order to combust the diesel fuel properly and completely, it is imperative that the diesel fuel is injected into each cylinder at the proper time in an evenly balanced spray pattern. If the diesel fuel Lubricity Value is too low, the fuel injectors (which are lubricated by the diesel fuel itself) will stick and ‘chatter’ or seize entirely. When this happens, combustion efficiency is reduced and unburned hydrocarbons and other exhaust emissions are increased.
Other Factors Affecting Diesel Fuel Emissions
Weather Effects – Diesel fuel burns with the least amount of unburned harmful emissions when the weather is stable with constant pressure and humidity. Unfortunately, the air taken into the engine is almost never a constant product. As the weather gets hotter or colder or wetter or drier, the air taken into the diesel engine dramatically changes. The changes in air density as a result of temperature and humidity act to change the combustion efficiency with each cylinder firing. These changes to the combustion dynamics of the diesel fuel increase the fuel related emissions exhausted from each cylinder.
Cold Weather Effects – All diesel fuels contain significant amounts of liquid paraffin which provide a substantial portion of the heat energy in the fuel. Unfortunately for the diesel users, the liquid paraffin content changes to solid wax crystals as the fuel temperature is lowered. These wax crystals will agglomerate and foul the fuel delivery system (pumps, filters and injectors) causing poor or incomplete combustion which increases unburned hydrocarbon emissions.
This poor combustion efficiency leads to increased carbon particulates entering the EGR Valve and DPF systems which reduces the time between DPF regenerations – “REGENS” and increases diesel fuel consumption with no additional horsepower being sent to the drive train.
Correcting The Problem
All of the issues affecting diesel fuel combustion efficiency and ultimately unburned diesel fuel hydrocarbon emissions discussed in this article can be eliminated by treating the diesel fuel with the ‘right’ combination of diesel fuel chemical additives.
Unfortunately, most of the commercially available diesel fuel additives sold in the retail market (i.e. truck stops, auto parts stores, department stores, etc.) and many of those sold in wholesale markets do not contain even minimally adequate amounts of the required chemistries to do the job.
In order to fully correct the problem, the ‘right’ diesel fuel additive must contain (at a minimum) enough chemistries at the recommended treat rate to achieve these minimum performance parameters:
(a) Cetane Improver to increase the Engine Cetane Number to 50+
(b) Detergent chemistry to achieve a DW-10 Detergency Rating in all fuels
(c) Lubricity Agent to lower the HFRR fuel lubricity to 400μm or less
(d) Storage Stability to retard natural fuel degradation for 12 months or more
(e) Deposit Modifier to clean off existing deposits and minimize future fuel related deposits
(f) Cold Flow Improver to lower the Cold Filter Plugging Point (CFPP) by 25 degrees F or more
(g) Wax Dispersant to fully suspend the paraffin wax 25 degrees F below the Cloud Point
(h) De-Icer Agent to reduce the moisture freeze point to – 40 degrees F or more
The above chemistries compounded in the ‘right’ concentrations will correct more than 90 percent of all diesel fuel combustion issues and thereby prevent nearly 90 percent of all unburned hydrocarbon and related emissions at all operating levels. The other 10 percent can be directly targeted by specific chemicals compounded into specialized diesel fuel additive products for the individual application.
Conclusion
Correcting combustion issues allows the diesel engine to operate as designed and minimize fuel related issues and extend the useful life of the equipment. This also will maximize the rated fuel economy designed for the engine with typical diesel fuels and greatly enhance the engine performance achievable with less than optimum quality diesel fuels.
But, the ‘right’ diesel fuel additives cannot be treated only once. The ‘right’ formulated diesel fuel additives must be utilized and treated into the diesel fuel at the ‘right’ dosage rate with every fill-up of fuel or every bulk delivery into the storage tanks.
This will allow the diesel fuel to burn properly without visible smoke and other unburned hydrocarbon emissions AND reduce fuel related maintenance costs. The operator will also realize a significant improvement in fuel economy (efficiency) because a greater portion of the diesel fuel will be producing usable horsepower instead of being blown out of the exhaust stack.
Written by: Gary Pipenger, President
Amalgamated, Inc
P. O. Box 8977
Fort Wayne, IN 46898
260-489-2549
www.amalgamatedinc.com
Foot Note:
Amalgamated, Inc is the only true independent “custom blender” in North America and a unique supplier of “synergistically balanced” distillate fuel additive chemistries. These custom blended fuel additive products are thoroughly tested and unmatched in operability performance in all types of diesel fuels and all engine applications because the additive chemistries are “specifically matched” to the fuel for optimum engine application. These chemistries are the best available for maximizing combustion efficiency and reducing fuel related combustion emissions.