July Summary of Fuel Injection Equipment With Respect to Diesel Fuel Filtration. From AVL and Racor Division of Parker Hannifin

Transcription

1 July 2014 Summary of Fuel Injection Equipment With Respect to Diesel Fuel Filtration From AVL and Racor Division of Parker Hannifin Abridged and Edited Version 1/07/15 Contact Information: Racor Division Global Headquarters Steven Hardison Parker Hannifin Racor Division 3400 Finch Road, Modesto CA United States Ph: Fax Racor Filter Division Europe Adam Pearce Parker Hannifin Manufacturing Limited Shaw Cross Business Park Churwell Vale, Dewsbury WF12 7RD United Kingdom Ph: +44 (0) Fax +44 (0)

2 Executive Summary In a climate of continued environmental focus there has been a drive towards reduced tailpipe emissions in all major global markets. In order for manufacturers to develop engines that can comply with the new legislations, engine technologies have been developed both in complexity and cost. Additionally, there has been a demand to reduce fuel consumption and greenhouse gas production. To deal with these demands, diesel engine injection pressures have increased to the 2500 bar (36,300 psi) range, driven by the criteria emissions benefits associated with higher injection pressures. Complex after-treatment systems coupled with a drive for improved NVH has led to an increase in injection flexibility with multiple pilot injections and late post injections for DPF and SCR management. Common rail has emerged as the mainstream technology across all sectors. The increase in system pressures in diesel engines has a significant effect on filtration requirements. These systems are highly vulnerable to many forms of contaminants and the need for robust high efficiency filtration has never been higher. The costs of fuel injection systems have also risen in line with system pressure increases and this further justifies the increase in filtration efficiency to protect these systems. An analysis of global diesel fuel quality shows that although the fuel quality in the developed markets has improved, significant quality concerns still remain. Levels of water and contaminants remain at levels that can cause long term issues to the latest fuel injection systems. Specifically, the levels of contaminants smaller than 5 microns remain very high. These particles can be small enough to pass into the internal clearances of high pressure fuel injection systems and can lead to erosion and wear of critical areas leading to a loss in system performance and eventually system malfunction. Diesel filtration balances pressure drop, useful life and efficiency. However the real long term effect on fuel system life is often not adequately considered; as much of the engine durability testing performed is done using high quality fuel that doesn t represent the range of fuels seen in the market. Consideration of filtration performance under less than ideal conditions is necessary to develop an acceptable level of protection. Diesel fuel filters have become integral, complex engine systems, integrating multiple sensors, valves and pumps. As engines become more complex, manufacturers are looking for suppliers to take on more system development responsibility and offer integrated solutions. Filter modules are now available that integrate filtration and distribution functions for not only fuel, but for engine oil, coolant, and Selective Catalytic Reduction (SCR). As overall engine costs have risen with increased emissions compliance, the cost pressures on existing engine components has also grown. By themselves, filters can still be seen as commodity products. However, filtration costs may be justified with use of new media technologies, sensors, function consolidation, and enhanced protection of fuel system components. Page i

3 Contents Executive Summary... i Contents... ii List of Figures...iii 1. Introduction Background Project Objectives Emissions Legislation European On-road Euro 5& US On-road LEVIII, EPA European Non-road Stage IV US Non-road, Tier 4 (40 CFR 1039) Marine IMO Tier III (International Marine Organization) Emissions Summary Engine Technology Drivers European and North America On road heavy duty European and North America Non road Engine Technology Drivers Summary Fuel Types and Specifications Diesel Worldwide Fuel Charter Biodiesel Fuel Properties and their Impact on Filtration Fuel Quality Survey Seasonal difference Fuel Quality Survey Summary Diesel Fuel Injection Systems Passenger Car Diesel Systems Summary Contaminants and Sources Contaminants Wear Mechanisms Filtration Requirements Filtration from Refinery to Tank Conclusions and Recommendations Parker Racor Fuel Filtration Products References Page ii

4 List of Figures Figure 2 1 Global Non-road emissions requirements... 6 Figure 2 2 Global HD On road emissions requirements... 7 Figure 2 3 North America NOx + HC emissions reduction... 7 Figure 3 1 Typical European diesel technology roadmap Figure 3 2 Heavy duty engine and after-treatment configuration Figure 3 3 Example of fuel dispensing cabinet with high efficiency filter Figure 5 1 ISO 4406 Code chart Figure 6 1 Scheme of Passenger Car Common Rail Injection System Figure 6 2 Piezo injector Figure 6 3 Scheme of Heavy Duty Common Rail Injection System Figure 6 4 BOSCH Amplifier Piston Common Rail Figure 6 5 Illustration of Delphi s F2 System Figure 6 6 Delphi F2P System, 1 pumping element and 3 pumping elements Figure 6 7 Common Rail FIS Layout / Jumper Lines FIS Layout Figure 7 1 Example of rust in an off highway fuel tank Figure 7 2 Sludge Build up due to algae / particles formed by Acid attack Figure 7 3 Example of fuel deposit on an armature and needle (injector) Figure 7 4 Abrasive Flow Wear Mechanism Figure 7 5 Effect of Abrasive Flow Wear on a Control Edge Figure 7 6 Abrasive Contact Wear Figure 7 7 Abrasive contact wear mechanism Figure 9 1 Example of BP facing a class action lawsuit for poor quality fuel Figure 9 2 UK example of contaminated fuel Figure 9 3 Example of enhanced filtration on fuel dispensing truck Figure 10 1 Example of system approach to fuel filtration (Parker Racor) Figure 11 1 Diesel Filtration Solutions by Parker Racor Page iii

5 1. Introduction 1.1. Background Racor is a leading supplier of filtration systems. In 2000 Racor requested AVL to conduct a study of diesel fuel filtration system requirements. In 2013 Racor requested AVL to provide an updated fuel filtration study. This report is a Racor abridged diesel-only version of the AVL report. The focus is on filtration systems designed for diesel engines that are intended to comply with the latest emissions legislations. (Euro 6, EPA 10, Tier 4) The application areas within the scope of this Racor abridged AVL study are: On road truck (LD,MD,HD), Large engines, Off highway, Marine diesel, Power generation. AVL also acquired a global fuel quality study. Included within this paper is a Racor abridged analysis of the fuel study data and an assessment of how these influence diesel fuel filtration requirements. For more complete information please contact Racor Project Objectives There are many factors that determine the correct filtration specification for any given diesel engine application. The aim of this study is to look at the factors for each market and application in detail and review the impact of these factors on diesel fuel filtration. The focus of this study will be on technologies that apply to the developed markets that have adopted more stringent emissions legislations. Page 4

6 2. Emissions Legislation This study will focus on the requirements for regions that have adopted enhanced criteria emissions standards. However lesser regulated markets should also be considered. In the industrial engine market it is becoming standard practice to sell the engines / vehicles / machines into lesser regulated countries after several years of operation in the original market. Often de-tier kits are applied to the engines to remove engine systems that are not required in the new markets. However the fuel system is at the heart of the engine and this will normally remain on the engine as it enters service in a new market. The fuel quality in these markets can be significantly worse than the original market, therefore the filtration requirements can be different. Figure 2-1 Global Non-road emissions requirements Page 5

7 Figure 2-2 Global HD On road emissions requirements Over the last 30 years there has been a steady reduction in criteria emissions limits for all vehicle and engine types. The following chart gives an example of this reduction for NOx + HC emissions for North America: Figure 2-3 North America NOx + HC emissions reduction Page 6

8 2.1. European On-road Euro 5&6 Light Medium Duty The Euro 5 / 6 standards were phased in starting in 2009, the phase in is dependent on vehicle type. Euro 6 will start to be introduced in September 2014, although most manufacturers have introduced Euro 6 vehicles already to comply with regional incentive programs. The most notable change between Euro 5 and 6 in respect to diesel engines is a significant NOx reduction. This NOx reduction will drive the introduction of enhanced diesel after-treatment systems (SCR) as well as increased injection pressures. Heavy Duty The Euro 6 heavy duty emissions standards came into force in December 2012 for new approvals and December 2013 for all registrations. This standard applies to heavy duty vehicles where the gross weight exceeds 2610 kg. As engines in this category are used in multiple applications the test takes place on an engine dynamometer rather than a vehicle dynamometer. As with light duty, Euro 6 saw a significant NOx reduction compared with the Euro 5 standard. As the fuel system can make a significant contribution to the deterioration of emission systems over time, Euro 6 requires a useful life ranging from 160K km or five years, up to 700K km or seven years, depending on vehicle class and load capability US On-road LEVIII, EPA 10 Light Duty The Tier 3 standards closely aligned with California LEV III standards are to be phased-in over the period from 2017 through The structure of Tier 3 standards is similar to the Tier 2 standards manufacturers must certify vehicles to one of seven available certification bins and must meet a fleet average emission standards for their vehicle fleet in a given model year. The standards are more stringent than Tier 2 standards and include a number of other important changes regarding limits on the sum of nonmethane organic gases and nitrogen oxides. The Tier 3 rule also includes emission standards for heavy-duty vehicles (HDV), such as heavy-duty pick-ups and vans, and chassis-certified as complete vehicles. Tier 3 standards apply over a useful life of 150,000 miles or 15 years, whichever occurs first. Heavy Duty The current emissions standard in force for heavy duty engines is referred to as EPA10 (40 CFR Part 86). The standard was first introduced in 2007 with a phase in to get to full compliance by Useful life requirements range from 110 thousand miles or 10 years for light duty diesel engines, up to 435 thousand miles, 10 years, or 22,000 hours, for heavy-heavy duty diesel engines, with some possible exceptions. Page 7

9 2.3. European Non-road Stage IV The stage IV emissions requirements closely mirror the emissions requirements for US non road engines. The requirements for stage IV came into force in The standard requires the emissions to be measured on engine during both a steady state and transient test cycle. For the main power sector (130kW to 560kW), the NOx standard is the same between Europe and the USA. The particulate matter (PM) standard in the USA is 20% lower than Europe. Unlike the USA, Europe currently has no limitation for engines over 560kW in this category. In reality there are very few applications that this would apply to, for example a large 560kW harvester would be too big to be practical in Europe where as in the USA these are commonly seen. There are currently no fixed plans for stage 5 but the expectation is that the sector below 19kW and above 560kW will be regulated. In addition particulate number standards are expected to bring the standard in line with the on road legislation US Non-road, Tier 4 (40 CFR 1039) The Non-road legislation for diesel engines has reduced the criteria emissions limits steadily from 1996 to This sector has seen the most significant changes in the shortest time. This has driven a total shift in applied technology in this area. The non-road legislation is staggered in 4 stages (Tier 1-4), with Tier 4 being the current legislation. Due to the difference in engine cost at different power levels, the emissions targets are staggered by power band. It would be cost prohibitive to apply a full heavy duty style exhaust after-treatment system to light duty engine. Useful emission equipment life requirements also apply depending on engine duty cycle. This legislation applies to most non-road engines, however certain categories are covered by alternative rules, such as locomotive, marine, and mining engines. Tier 5 is not yet defined and if implemented may focus on other aspects of the legislation (e.g. On Board Diagnostics), rather than the criteria pollutants Marine IMO Tier III (International Marine Organization) The IMO is a UN organization which promotes maritime safety. Through the International Convention on the Prevention of Pollution from Ships known as MARPOL 73/78, it regulates the emissions from ship exhausts. The IMO standards are known as Tier I, II and III. Tier I was introduced on 19th May 2005 and covers engines greater than 130kW installed on vessels on or after January 1, 2000 or which undergo major conversions after that date. Tiers II and III were adopted in 2008 and cover new fuel quality specifications, improved NOx standards for existing pre-2000 engines, and globally based ocean regions and Emission Control Areas with specified emission reduction requirements. Actual emission levels are defined by engine rated speed and the area of operation. Page 8

10 Although there are no limits on soot, generally no visible smoke is acceptable. Avoiding smoke requires higher injection pressures, especially at partial load and therefore high pressure common rail injection systems are being increasingly used Emissions Summary In all engine sectors from small passenger engines to large marine vessels there has been a focused effort to reduce harmful exhaust emissions. In on road applications the emissions levels have dropped to the point where further reductions will have a smaller environmental impact. Therefore future changes in legislation for harmful emissions will focus on refinements to address specific issues rather than major order of magnitude reductions that have been seen in the past. An example of this could be the introduction of particulate number standards to effectively mandate the use of DPF filters for on road trucks in the USA. However with the harmful emissions standards reaching a plateau the focus will shift towards fuel economy and CO2 reduction. In the past the main pressure for improved fuel economy has been consumer driven, however recent legislation is mandating fuel economy improvement. These standards will continue to drive engine, after-treatment and vehicle technology. Fuel systems will continue to play an important role in the package of technologies being applied to meet the challenge. Page 9

11 3. Engine Technology Drivers In order to understand the effect of the emissions legislation into filtration requirements the first step is to consider the steps required on the engine and after-treatment to comply with the standards. As the technologies vary by market sector and region these are categorized into: European and North America On road heavy duty North America non road heavy duty European and North America Non road For diesel engines direct injection has overtaken indirect injection for many years. In the diesel combustion system fuel is injected directly into the cylinder over a very short period. At full load this duration is around 27 engine degrees. In a modern high speed diesel engine at 4000 rpm this equates to around second. Fuel flow into the cylinder is determined by the pressure of the injection and the number and size of the injection holes. If the holes are too big then the fuel atomization can be poor leading to higher smoke emissions. Therefore high fuel injection pressures are a key requirement for current and future diesel engines. These pressures have historically been limited by the fuel injection technology and the high parasitic losses required to create these pressures. The chart below shows a typical technology roadmap for European diesel engines. This chart shows that with increased vehicle size and therefore increased power the required injection pressure increases from around 1600 bar for A class vehicles and up to 2500 bar for full size passenger cars and SUV s. Figure 3-1 Typical European diesel technology roadmap Page 10

12 In both Europe and North America alternative fuels have been considered; E85 is available in North America but the consumer benefit is limited, Bio-diesel is readily available in Europe, however the mainstream usage rate is only about 7% European and North America On road heavy duty Currently different emissions standard exist in North America and Europe. Plans have been discussed to harmonize the standards and test procedure. However it seems unlikely for this to happen in the near future. The target of both legislating bodies is very similar; both have targeted very low NOx standards that have effectively mandated the use of active NOx reduction after-treatment systems. The mainstream system now being applied is Selective Catalytic Reduction (SCR). Differences do exist on the standards for particulate matter (PM), the standards in both regions do not mandate the use of a Diesel Particulate Filters (DPF), but in practice it is quite difficult to achieve the standards without the use of one. In Europe an additional standard exists that controls the particle number, this ensures that a DPF is used in Europe. The following chart shows the typical engine and after-treatment configuration for a heavy duty engine: Figure 3-2 Heavy duty engine and after-treatment configuration Page 11

13 With this class of engine there is more than one way to achieve the emissions targets. The key parameter for this is Exhaust Gas Recirculation (EGR). Using EGR, engine exhaust NOx emissions can be reduced through the use of a lower efficiency (lower cost) SCR system and consequently lower Diesel Exhaust Fluid (DEF, AdBlue in Europe) consumption. This is where fuel injection plays a role. Using EGR increases engine exhaust PM emissions, which is then controlled by using higher injection pressures. The decision to have an EGR system or not is quite complex and depends on the capability of the engine, air system flexibility and whether the engine will need to go into high sulfur fuel markets that cannot use EGR systems. Many of these heavy duty engines have historically used unit injection fuel systems and suitable common rail systems have not been available. In recent years many of these engines have been converted over to common rail as new systems have been developed. Typically injection pressures in the range of 2000 bar to 2500 bar are used. Studies have been done up to 3000 bar and systems are in development to realize these pressures. EGR systems also offer the potential of fuel economy improvements, therefore the direction in the future is likely to be towards EGR as standard and high pressure fuel injection as a standard European and North America Non road Non road engines have been one of the last classes of engines to be targeted for emissions reductions. The standards applied are not as stringent as on road. Also these standards are much closer aligned between Europe and North America as these engines are produced as global products. This allows manufacturers to take a more varied approach. In addition different technologies can be applied at different power levels as the emissions requirements reduce at lower powers. Non road engines have been developed with multiple variations, often due to specific application requirements or the technology route taken for previous emissions tiers. Below 560 kw the technology requirements decrease. This is due to the emissions requirements easing above 560 kw. However the authorities have stated that this will be an area of investigation for them at the next round of rulemaking. Page 12

14 3.3. Engine Technology Drivers Summary As previously stated emissions and fuel economy pressures have been the main drivers for engine technology development. Across all engine sectors this has led to the introduction of more advanced fuel injection systems, these systems have higher pressures, smaller nozzle holes, higher accuracy and advanced controls. In the developed regions this technology development has been matched with a focus on improved fuel quality. In the on and off road diesel engine fields advanced after-treatment systems have been introduced and in many cases this has allowed the use of lower pressure fuel injection systems as the burden of emissions control is taken up by the SCR system. A real challenge still exists for the emerging markets where the proposed emissions standards will drive the introduction of advanced engine and after-treatment systems, however the fuel quality in these regions has lagged behind leading to potential concerns with high pressure fuel systems, EGR systems and after-treatment. Improved fuel filtration is a key to ensuring robustness of the fuel systems in these markets. Going forward, because of the difficulties of maintaining a clean supply of diesel at all times, more consideration should be applied to upstream sources of contamination as well as at the engine. Filtering recirculation systems can be applied to storage and onboard systems, along with high efficiency filters at the dispensing pump. Careful monitoring of fuel quality and filter performance is needed to protect sensitive diesel engine injection systems. Figure 3-3 Example of fuel dispensing cabinet with high efficiency filter Page 13

15 4. Fuel Types and Specifications The majority of fuels are subject to standards and norms which the fuels have to meet on leaving the refinery. Norms differ somewhat from country to country, for instance in Europe Diesel fuel should meet the Norm EN 590, while in the USA ASTM D975 is the required standard. The fuel quality also varies with the climate into which the fuel is to be sold which especially governs the fuel s low temperature characteristics. Where possible, the different fuel standards for Europe and the USA have been summarized. For more information, the actual Norms should be used as the values can change with new editions. In addition, a worldwide fuel charter has been issued by the European Automobile Manufacturers Association (ACEA), the Alliance of Automobile Manufacturers (Auto Alliance), the Truck and Engine Manufacturers Association (EMA) and the Japanese Automobile Manufacturers Association (JAMA) which aims to increase the understanding of the needs of vehicle and engine technologies and promote quality harmonization in accordance with those needs Diesel Diesel fuel in Europe is specified according to EN 590 which among other requirements specifies minimum Cetane and maximum sulfur, water, and ash contaminant levels. In addition, the properties are divided into groups for different climatic zones. The temperate climatic zones split the fuel into six classes from A to F, while the arctic zones are classified into five classes from 0 to 4. These classifications are necessary to ensure that under the given environmental conditions, problems with waxing of fuel which lead to filter plugging and cold start-ability do not arise. North American Diesel fuel is specified according to ASTM D975 and cover the same specifications as found in EN 590. As the climatic conditions vary from state to state so fuel characteristics can vary from state to state and by time of year. The cold start performance of the fuels is based on low temperature operability requirements derived from tenth percentile minimum ambient air temperatures derived for the different states and regions. Depending on the state or region into which the fuel is to be sold, there are differences in the cold behavior of the fuel and this information is included in the specification. The fuel is graded into three grades, 1-D, 2-D and 4-D with different sulfur levels for each Worldwide Fuel Charter The worldwide fuel charter is proposed by the ACEA (European Automobile Manufacturers Association), the alliance of Automobile Manufacturers, the Truck and Engine Manufacturers Association and the Japan Automobile Manufacturers Association. They specify five different classes of fuels, both gasoline and diesel, dependent upon the requirements for emissions controls. Category 1 is for markets with no or basic emission controls, up to Category 5 for markets with highly advanced requirements for emissions control and fuel efficiency. Page 14

16 4.3. Biodiesel In many countries, due to concerns about fuel security and CO2 emissions, there is an increasing desire to move away from fossil based fuels and use renewable fuels derived from plants, trees and other similar biological sources. For diesel, such fuels can be produced from rape seed, soy beans and other oil rich plants and are the 1st generation of biofuels. The second generation of biofuels will be produced from wood waste and similar sources which can be gasified by processes such as Fischer Tropsch, turned into a diesel substitute having excellent diesel like properties. Such fuels are also sulfur free. In the USA there are two Biodiesel standards, ASTM D6571 for 100% Biodiesel and ASTM D7467 for biodiesel blends. The ASTM D6571 is the grade for the biodiesel used to produce the blends. In a similar fashion to ASTM D975, ASTM D6571 covers different grades of biodiesel, 1-B and 2-B having differing Sulfur levels. The blended Biodiesel is regulated in the range 5 20% biodiesel content. As for normal diesel fuel, biodiesel cold temperature performance requirements are based on the temperatures experienced in the different states and regions Fuel Properties and their Impact on Filtration There are several properties in the fuel specifications which have an impact on diesel fuel filtration. Ash Content The ash content is a measure of the ash forming material contained in the fuel. The total ash content is determined by burning a small sample of the fuel in a weighed dish until all the combustible material is consumed. The weight of the residue is reported as a percentage of the original sample. Some of the this ash can be present as suspended solids in the fuel or soluble organic metallic compounds which can add to wear of both the fuel injection equipment of the engine components such as piston rings. Water Water is usually only present in very small quantities when the fuel is refined as it cannot be totally eliminated. However, water contaminates the diesel at various stages during the storage and transportation processes. This happens due to residual water content in the storage container, water entering with humid air during fuel withdrawals from the tank and condensation when temperature falls. As water collects at the bottom of the tank, fuel should not be drawn from the bottom of the tank. The presence of water encourages microorganism growth which blocks filters and causes corrosion. Water also promotes rust and displaces fuel lubrication throughout the fuel injection system. Page 15

17 Total Contamination Contamination usually refers to sediments of rust and inorganic particles. These tend to originate from tanks and lines and are a result of poor housekeeping. Diesel specification values refer to the content of contamination when the fuel leaves the refinery, not when it enters the fuel tank of the vehicle. Cloud Point CP The cloud point refers to the temperature at which wax forms in the fuel. This is a somewhat subjective test as it is determined by observing the temperature that wax is first seen at the bottom of a jar as the fuel is cooled. The value of the cloud point will vary by as much as 4 C depending upon operator and facility. Cold Filter Plugging Point CFPP The CFPP is a measure of the fuel temperature at which the flow is restricted by the wax such that 20 ml of fuel will not flow through a wire mesh with a pore size of 45µm within 60 seconds. The CFPP is approximately 10 C below the cloud point and is recognized as giving a more realistic indication of the expected driving experience. Glycerin Content Glycerides are a byproduct of Biodiesel manufacturing through the transesterification processes and are produced from the reaction of fatty acid stock oils with methanol. The levels of glycerides which are permitted are of the order of 0.2% and glycerin 0.02%, but glycerins are highly hygroscopic so they attract extra water. Glycerin also has a much higher viscosity than diesel. Compatibility of Elastomers Biodiesel may have negative effects on the standard elastomers used for sealing components in the fuel injection systems. Page 16

18 5. Fuel Quality Survey As part of the scope of the fuel filtration investigation a global fuel survey from SGS in Switzerland is referenced. SGS produces this survey twice per year, once for the winter season the other for summer. These surveys are produced for a number of fuels. For this project only diesel fuel is referenced from summer 2013 and winter 2013/214. This survey covers the results of a wide range of testing of 924 fuel samples gathered in 100 countries. For analysis, the countries were grouped by region; Western Europe, Eastern Europe, North America, South America, Asia, Africa, Australasia and the Middle East. The following report focuses only on the different types of fuel contamination related to fuel filtration performance requirements: Contamination (gross particulates) Water Bio-content Cold Characteristics The survey size is statistically large enough to draw conclusions from. However the sample number per country can be small. Therefore the maximum level seen in any one country must not be considered to represent the real worst case fuels found in the market Contamination (gross particulates) The measuring of contamination was done in a number of different ways. Each sample had a full weight and particle distribution analysis done. Test EN590 specifies a maximum contamination of 24 mg/kg (measured according to EN 12662). This test is a general measurement of total particle contamination. When considering contamination, the particle size distribution can be a more useful measurement. For example, one sample may meet the 24mg/kg total limit, but have a very high concentration of small particles that will pass through the filter and cause wear on fuel system components. Whereas another sample may exceed the 24 mg/kg limit but contain larger particles that are easily retained in the filter. It must be noted that current laboratory particle counting of diesel fuel samples cannot see or count particles smaller than 4 microns. At the same time, these smaller unknown size particles are much more difficult to filter out. This highlights the need for improved efficiency when offering filtration solutions to markets with fuel injection systems developed for higher emissions tiers. The general result obtained was that most samples worldwide were below the 24mg/kg limit, with some isolated areas measuring considerably worse. Higher emission tier regions were generally within the limit. Page 17

19 As stated before, in order to accurately assess the true fuel sample quality the contamination particle size distribution must be considered. Worst case fuel may often be several times more contaminated than average. ISO-4406 A useful and standard way of determining fuel contamination level is using the ISO system. A laser particle counter is used to count the number of particles at each size. The number of particles are then categorized in three size ranges, >4um, >6um and >14um. The number count is used to look up a code number from a chart. The chart below is an extract from the ISO standard. The resulting three number code is used to represent the fuel cleanliness level. Many diesel fuel system manufacturers use this system to specify the cleanliness requirements of fuel entering the fuel system. Figure 5-1 ISO 4406 Code chart The regional analysis using the ISO4406 coding gave a similar picture to the particle size distribution analysis. Again, Africa, Asia and the Middle East have the most highly contaminated fuel in the survey markets, and developed regions have the cleanest fuel. UK fuel contamination levels were higher than expected. Fuels samples were taken from regular filling stations and do not represent the real worse case fuels that could be encountered. Off highway fuel samples are often highly contaminated by dirt and dust stirred up at the work site Water Water contamination represents a significant hazard to diesel fuel injection systems by encouraging microorganism growth which blocks filters and causes corrosion. Water also promotes rust and displaces fuel lubrication throughout the fuel injection system. The European standard allows a maximum free water content of 200mg/kg. With this much water, a fuel filter could conceivably need to block and collect a liter of water every 100 hours on a typical industrial engine. Data from developed regions showed low water content, so stopping water there is often less of a problem out of the dispensing pump. Page 18

20 Most samples taken globally were within the limits, with a few exceptions in the undeveloped markets. As the samples were all taken at service station pumps, it is reasonable to assume that under other circumstances, additional water introduced though poor fuel handling and tank condensation may still pose a threat at the vehicle. It should also be noted that during diesel filtration, overall water removal efficiency is also greatly influenced by the amount of biodiesel mixed with the fuel. Biodiesel acts as a surfactant and can severely degrade fuel filter water removal performance Bio-Content The European fuel standard (EN590) for Fatty Acid Methyl Ester (FAME) content is currently 7%. Although higher levels are available but a different fuel standard applies. Generally Europe leads the way on the promotion and used of Bio-diesel, this is born out in the data analysis. Most European fuel are at or below the 7% level. Western Europe, Eastern Europe, South America and North America have higher levels of bio-fuels, whereas Africa, Asia, Australasia and the Middle East have low levels. In addition to the Bio-content the oxidation stability of the fuel should also be considered. Bio-diesel contains hydrocarbons that will oxidize when exposed to atmospheric oxygen. The fuel standard uses 2 metrics to determine fuel stability, one is oxidation stability and the other is Rancimat. For stability the max level is 25g/m^3, for Rancimat there is a minimum level of 20 (h). In the study, only a few samples measured high oxidation levels, with most of the fuel coming from areas of high biodiesel adoption. Cold Characteristics For filtration, another key characteristic is the cold flow properties of the fuel. Cold fuel filter plugging is a common problem with diesel fuel systems. Manufacturers have adopted various strategies to handle this problem. These include: Electrical heating of the filter and fuel lines Warmed engine return fuel reintroduction Engine coolant heat exchanger Pressurized filter supply Engine block heater Cold filter plugging point (CFPP) is the lowest temperature at which a given volume of fuel still passes through a standardized filter device in a specified time when cooled under specific conditions. Cloud point, is the temperature at which dissolved paraffin solids are no longer completely soluble. Pour point and flow point, as the names suggest, indicate the point at which diesel will not pour or flow correctly. This metric is outdated as it doesn t capture the impact of fuel passing through a filter. In general CFPP is used. Page 19

21 CFPP is varied by the fuel producer to suit the local market conditions by blending #1 diesel (basically kerosene) with #2 diesel. Additives are used to further lower the CFPP if the temperatures require it Seasonal difference Refiners produce different grades of diesel fuel to suit the local market temperature requirements. However there is normally a winter and summer grade. The winter grade will have a lower CFPP tailored to the region. In some regions such as Scandinavia, where the temperature variation is more significant, a larger difference can be seen between the summer and winter grades. Their CFPP shift is a large as 15 C between summer and winter compared to only a 5 C shift in the USA Fuel Quality Survey Summary The samples were taken from filling stations around the world and in practice, there will always be stations and situations where worse fuel is available. However the data can be used to judge regional and national trends: The fuel quality in some developed markets raises concerns (UK, Portugal, Germany) Bio-Diesel content is generally under control worldwide, with a few exceptions. Water levels were also under control, although higher water levels will be seen due to water entering fuel tanks through condensation and poor fuel handling practices. Excessive inorganic, abrasive contamination content raises serious concerns over the use of high pressure common rail systems in the developing markets. For further discussions on Fuel Quality, please contact Racor. Page 20

22 6. Diesel Fuel Injection Systems 6.1. Passenger Car Diesel Systems The vast majority of passenger car fuel injection systems in production and use today are high pressure common rail systems. In principle they all function in the same manner, although there are minor differences between manufacturers. There are a number of different manufacturers for diesel direct injection systems for passenger cars, namely: Bosch Continental Delphi Denso The systems are very similar in their working principles and therefore only the general principles are described, without reference to the manufacturer. Figure 6-1 Scheme of Passenger Car Common Rail Injection System Typical passenger car common rail fuel injection systems have a supply pump directly mounted in the fuel tank, protected from debris by a fine strainer fitted to the inlet. The fuel is then fed to the high pressure pump through a fine filter at a pressure of around three to five bar. The fuel is then supplied to the common rail at pressures of between 300 and 2500 bar, depending on the operating point. The fuel quantity and pressure are regulated by the electronic control unit based on a signal from the rail pressure sensor and other driving inputs. The injected fuel quantity is based on the pressure in the rail and the duration of the control signal to the injector. Page 21

23 In passenger cars, there are mainly two kind of injectors, piezo and solenoid valve actuated. The piezo valves have much faster response times than injectors with solenoid valves, and allow faster and more precise operation of the injector, allowing smaller separation between injections. Figure 6-2 Piezo injector The common rail system offers a high flexibility in means of engine combustion requirements. This flexibility is achieved by: High injection pressures Adapted injection pressures according to engine load Great range of start of injection timings Multiple injections, up to 6, depending on engine load, emission compliance and after treatment strategies In that way, the common rail system has contributed to achieve higher engine power densities, lower fuel consumption, and lower soot as well as noise emissions. In the future, maximum injection pressures up to 3000 bar are expected in applications where very high power density is required. Page 22

24 6.2. Light to Heavy Duty Engines Diesel Systems Because of the current and further emission levels requirements, high pressure and high flexible systems are also required for these engine sizes. The majority of the truck engines, from light to heavy duty are also equipped with high pressure common rail systems. There are a number of different manufacturers for diesel direct injection systems for commercial vehicles, namely: Bosch Delphi Denso Liebherr Stanadyne Woodward Principally, the same working principle of the passenger car common rail systems applies for larger engines common rail systems, with some differences as: Solenoid actuators High pressure pumps, mainly in-line Pre-pump normally mounted on the high pressure pump Fine filter normally installed pre-pump downstream Up to 4 injections per cycle A scheme of a typical common rail system for heavy duty can be seen in the next Figure: Figure 6-3 Scheme of Heavy Duty Common Rail Injection System Page 23

25 The applied injection pressures in commercial vehicle are in the range from 300 to 2700 bar. Depending on the NOx reduction strategy and the after-treatment systems, the current max. injection pressures applied in commercial vehicles are in the range from 1800 to 2700 bar. Although for future emission levels the high pressure common rail system will be well established, there are three hybrid systems that should also be mentioned, the Amplifier Piston Common Rail System from Bosch (APCRS), the F2 and the F2P System from Delphi. Bosch Amplifier Piston Common Rail System (APCRS) The so called APCRS from Bosch works with hydraulically amplified injectors. Their amplifiers realize injection pressures of more than 2400 bar at the nozzle. In that way, high specific power output can be achieved despite low nozzle flow rates. The amplifiers are hydraulically driven with geometrical transmission ratio of more than 1:2; meaning a moderate high pressure level on the high pressure pump and rail side, up to 1350 bar. Hence the mechanical stress of such components is reduced, because only the nozzle module has to be designed for the highest pressure range. On the other hand, the delivery rate of the high pressure pump has to be significantly increased to deliver the necessary control quantity to drive the amplifiers. In the figure below, a cross section view of the hydraulically amplified injector and the hydraulic scheme is shown. Figure 6-4 BOSCH Amplifier Piston Common Rail The hydraulic layout of the pressure amplified system is similar to the standard Common Rail System except for rail pressure and amplifier piston modules, wherein rail pressure is at high medium level. The injectors contain amplifier modules to generate high injection pressure determined by a stepped piston. The amplifier is activated by a second solenoid valve in the injector. Without activating this solenoid the injection system acts as a standard common rail system because of the bypass path with check valve. Varying energising time of both solenoid valves allows for highly flexible pressure curves versus time to be generated. Page 24

26 Delphi F2 Integrated Pump Diesel Common Rail System The Delphi F2 integrated Pump Diesel Common Rail System (F2 System) is a different concept in diesel common rail technology, allowing the high pressure parts to be mounted entirely within an engine s cylinder head. The F2 system utilizes two types of injectors. Non-pumping injectors act like traditional common rail injectors whereas pumping injectors also contain separate pumping elements driven by the overhead cam, which pressurize the rail. The number of pumping elements is no longer fixed to the number of injectors and may, therefore, be optimized according to the power requirement of each application, see picture below. Typical applications are 9 to 16 litre heavy duty diesel engines that are used for on- and off-highway applications. For future applications, maximum injection pressures from 2700 to 3000 bar are expected. Figure 6-5 Illustration of Delphi s F2 System Page 25

27 Delphi F2P High Pressure Heavy Duty Diesel Common Rail System In the Delphi F2P Common Rail System, the pumping elements are separated from the injectors and are driven by the engine s camshaft or mounted in a separate cam box. The unit pumps constantly charge up the common rail to high pressures. Dependent on the power requirement of the application, this can be achieved by using any combination of electronic unit pumps between two and six per engine, see Figure below. Typical applications are 9 to 16 litre heavy duty diesel engines that are used for on- and off-highway applications. For future applications, maximum injection pressures from 2700 to 3000 bar are expected. Figure 6-6 Delphi F2P System, 1 pumping element and 3 pumping elements Page 26

28 6.3. Large Engines Fuel Injection Systems For current and future emission legislation, the high pressure common rail will also be used on large bore engine sizes. Current maximum injection pressures are up to 1800 bar, but all the suppliers are already working on 2500 bar systems. There are a number of different manufacturers for diesel direct injection systems for large engines, namely: Bosch Ganser (for Micro Pilot Common Rail Systems) DUAP Heinzmann L Orange OMT Woodward The main difference to the high pressure common rail system of smaller engines resides in the almost tailored solution for each engine and application. In this field, also special requirements must be fulfilled, e.g. certification for marine operation. In this case, double wall piping, system redundancy and leakage detection among others must be considered for the fuel system layout. The layout of the large engine common rail differs from smaller engines common rail designs. Due to the modular requirements (e.g. engine family with different number of cylinders), it is common to have the rail within the injector, known as accumulator volume, and the injectors connected by jumper lines. In the next Figure, an example of both, rail and jumper lines system layouts are shown. Figure 6-7 Common Rail FIS Layout / Jumper Lines FIS Layout Page 27

29 6.4. Summary The vast majority of passenger car fuel injection systems in production and use today are high pressure common rail systems. Because of the current and further emission levels requirements, high pressure and high flexible systems are also required for heavy duty and large engines. In high pressure common rail systems, particulate filtration efficiency requirements are more stringent, making finer filtration a critical requirement for modern diesel engines. In low regulated countries, robust mechanical injection systems as in line pumps, rotary pumps and P-L-N systems are still playing an important role. The upgrade from mechanical FIE to high pressure common rail systems will imply higher filtration efficiency requirements, meaning an additional challenge in those low regulated areas due to the poor fuel quality. To avoid costly engine and fuel system components damages, advanced multistage filtration is recommended Upstream quality control of the diesel fuel supply through fuel polishing and high quality dispensing filters is an effective step in avoiding damage from contaminated fuel. Page 28

30 7. Contaminants and Sources 7.1. Contaminants As we have seen from the fuel specifications, the definition of contaminant quantity is somewhat vague. None of the norms has a specification for the amount of contamination allowed in the fuel, although the worldwide fuel charter suggests 18/16/13 for contaminants of >4µm, >6µm and >14µm, which would mean a maximum of 2500, 640 and 80 particles per millilitre respectively. Theoretically, this information could be a basis for calculating fuel filter life. Unfortunately, with diesel fuel, even assuming that this quality of the cleanliness can be achieved at the filling station, further contamination can occur. The major sources of this contamination are: Dirt & Dust Rust Water Microbes Diesel Decomposition Internal Deposits Dirt & Dust Dirt refers to soil organics, clay, and sand. Some of this can be very fine and find its way into our fuels, blown by wind or falling from objects. Soil organics tend to be soft; while sands and clays contain fine hard silica based particles, which work abrasively. One third of the earth s land surface is covered by dust producing deserts and dry lands. Dust from these regions can be picked up by the wind and transported thousands of miles. In addition, road dust from vehicles can contribute up to 30% of air pollution. Dust can find its way into fuel tanks through open fuel caps during filling, breather holes in fuel caps as well as during transfer of the fuel to tanks. Rust Rust is also a source of particles in fuel as it can come from the inside of fuel tanks, storage tanks and other steel components in contact with the fuel. Water in the fuel corrodes steel tanks and causes the formation of rust. Many fuel tanks today are either plastic or plastic lined, but rust can form in any exposed steel in the system. Page 29

31 Figure 7-1 Example of rust in an off highway fuel tank Water Water is a major source of contamination of fuel and forms easily when temperatures drop and condensation from the air forms on tank walls. Extreme temperature changes (especially in desert climates) with nearly empty tanks can cause water to condense in fuel tanks overnight. As would be expected, marine environments are well known to have water in fuel problems due to condensation and poor fuel handling. Water poses a significant threat to diesel fuel injection systems. Microbiological Contamination Microbiological contamination, (bacteria, fungus, and algae) or diesel bug is organic growth which can occur where water is present in the fuel. It can be seen in the form of sludge which forms at the fuel/water interface, as a dark coating on filters, and as metal corrosion particles that result from bacterial waste acids. The bugs live and grow at the interface between the fuel and water. Usually it forms in the fuel tank and when the sludge build up is large enough it can block the fuel system, the filters, and starve the engine of fuel. An increase in the occurrence of diesel bug may be associated with the increased use of biodiesel because of its higher water content and biological ingredients. There are a number of biocides available to kill diesel bug, but the best defence is avoiding water and dirt contamination, and the best cure is to clean the fuel tanks and fuel system. Page 30