Search Results

Internal Diesel Injector Deposits (IDIDs) have been known for some time. With the latest powertrains becoming ever more sophisticated and reliant on efficient fuel delivery, the necessity for a continued focus on limiting their formation remains. Initial studies probed both carbonaceous based/ashless polymeric and sodium salt based IDIDs. The reported occurrence of the latter variety of IDID has declined in recent years as a result of the removal of certain additives from the diesel distribution system. Conversely, ashless polymeric based deposits remain problematic and a regular occurrence in the field.

Modern diesel Fuel Injection Equipment (FIE) systems are susceptible to the formation of a variety of deposits. These can occur in different locations, e.g. in nozzle spray-holes and inside the injector body. The problems associated with deposits are increasing and are seen in both Passenger Car (PC) and Heavy Duty (HD) vehicles. Mechanisms responsible for the formation of these deposits are not limited to one particular type. This paper reviews FIE deposits developed in modern PC and HD engines using a variety of bench engine testing and field trials. Euro 4/ IV and Euro 5/V engines were selected for this programme. The fuels used ranged from fossil only to distillate fuels containing up to 10% Fatty Acid Methyl Ester (FAME) and then treated with additives to overcome the formation of FIE deposits.

Future diesel engines will require new hardware to reduce emissions to the levels required by upcoming legislation. Advances in the fuel injection equipment (FIE) of the engine are a key enabler towards meeting such legislation. These modern systems produce temperatures and pressures at the injector tips that are considerably higher than those experienced today. This environment can initiate or increase the rate of deposit formation at and around the injector tip compared with current systems. Investigations have been carried out to further the understanding of this phenomenon using experimental nozzles simulating a similar deposit build-up as expected in EU 5 engines. The investigation used a protocol that has recently been released to the industry, commercial 10 ppm S fuel and a commercial diesel fuel detergent. Testing was carried out with both clean and zinc contaminated fuel. Zinc contamination with a fuel soluble salt was used to simulate severe market conditions.

Diesel engines will require new hardware to meet future emissions levels required by upcoming legislation. One of the key enablers towards meeting such legislation is the use of better fuel injection equipment (FIE). However, these systems can produce temperatures at the injector tips that are considerably higher than those seen today. This environment can exacerbate the rate of deposit formation or generate new types of deposits at and around the injector tip. Previous and ongoing investigations continue to further our understanding of this phenomenon using a modern passenger car diesel engine, various commercial 10 ppm S diesel fuels, a severe test cycle and injector nozzles representative of those likely to be in use in EURO V engines. The engine tests show good repeatability with clear and treated fuels. This supports the validity of the data generated. The test protocol used has recently been released to the industry.

This paper looks at the underlying fundamentals of diesel fuel system lubrication for the highly-loaded contacts found in fuel injection equipment like high-pressure pumps. These types of contacts are already occurring in modern systems and their severity is likely to increase in future applications due to the requirement for increased fuel pressure. The aim of the work was to characterise the tribological behavior of these contacts when lubricated with diesel fuel and diesel fuel treated with lubricity additives and model nitrogen and sulphur compounds of different chemical composition. It is essential to understand the role of diesel fuel and of lubricity additives to ensure that future, more severely-loaded systems, will be free of any wear problem in the field.

A variety of additives are used in automotive diesel fuel to meet specification limits and to enhance quality. For example, lubricity additives and cold flow improvers are used to meet specifications whilst diesel detergents further enhance the quality of the fuel. Recently, several premium fuels that use high levels of diesel detergents and, in some cases, cetane improver have been introduced in the market place. The purpose of the work carried out was to assess the potential impact of these additives on vehicle performance. In order to do this, a fuel free of any additive was treated with very high levels of all the diesel fuel additives currently used to meet specification limits and to enhance diesel fuel performance. A common rail vehicle using an advanced common rail system was then driven in a controlled manner for 50.000 km. Emissions and driveability tests took place at 0km to provide baseline data.

Continued legislative pressure to reduce diesel emissions has resulted in the development of engines with advanced fuel injection equipment (FIE). These injection systems produce temperatures and pressures at the injector tips that are considerably higher than those seen in previous technologies. This environment is initiating deposit formation at and around the injector tip which is leading to significant power loss and increased smoke generation. Investigations have been carried out to understand this phenomenon. Cyclic bench engine testing has generated high levels of deposits when minimal amounts of a fuel soluble zinc salt are doped into clear fuels. The deposits are found both in and around the nozzle tips. Analysis of the deposit shows the presence of zinc. These deposits are proving to be more challenging than those previously seen with older FIE technology. Detergents that have historically been effective in resolving injector deposits are proving less effective.

Diesel fuel is a major grade in the Thai market used in transportation of goods and in most light duty vehicles. Over the last fifteen years the quality of this fuel has continuously increased. This is one of the major factors that have allowed a substantial improvement in air quality. The improvement in diesel fuel quality has been achieved by using a mix of measures, some well known like reduction in sulphur content, whilst others are unique to this market. Since 1993, in Thailand it has been mandatory to use a diesel detergent. This has ensured best driveability and lowest emissions due to the control of injector deposits. This measure was unique in the world and although not mandatory any longer, this market has a large proportion of automotive diesel treated with this type of additive. Another action has been the evaluation of Palm Oil Methyl Ester (PME) and its potential impact in the market. However, experience with PME is limited.

Diesel fuel injector deposits have been observed in the field for many years. Their location and composition is dependant on the type of Fuel Injection Equipment (FIE) technology utilised in vehicles and fuel quality. This paper first characterises such deposits and then defines the maximum acceptable level to ensure best field performance for the following FIE systems: InDirect Injection (IDI), High Pressure Common Rail (HPCR) and Electronic Unit Injection (EUI). HPCR has been instrumental in achieving the lowest possible emissions and Fuel Consumption (FC) levels. It is now the only choice for new Passenger Car (PC) applications meeting Euro 5, US Tier 2 and Japan Post New Long Term emission regulations. Its use is also increasing in Heavy Duty (HD) applications. However, HPCR and EUI have both been shown to have a tendency to form injector deposits that can negatively impact emissions, power and fuel consumption.

The high frequency reciprocating rig (HFRR) was developed in the early 1990s as a test method to assess diesel fuel lubricity in order to provide wear protection for fuel injection pumps. This was necessary in response to the many field failures that occurred following the introduction of ultra-low sulphur diesel in Sweden. The prevalent fuel injection equipment (FIE) technology at this time utilised rotary pumps capable of reaching maximum fuel pressures of ∼650 bar in systems for direct injection engines. The continued drive for efficiency led to many changes in FIE technologies, materials and pressures. Modern high pressure common rail pumps reach significantly higher pressures, with 2200 bar available today and pressures up to 3000 bar discussed in the industry.

The addition of a proportion of Fatty Acid Methyl Esters (FAME) in automotive diesel fuel is becoming prevalent in different areas of the world. Indeed, in several countries it is now a legislative requirement that a proportion of diesel fuel must be derived from natural sources. This trend is increasing continuously, both in terms of geographical coverage and for the use of higher percentages of bio-derived fuel. Our work has focused mostly on Rapeseed Methyl Ester (RME). A variety of diesel fuels containing different ratios of RME has been tested to assess their propensity to form injector deposits in engines using different fuel injection systems: Swirl chamber (for indirect fuel injection) Current common rail Future common rail Results have been obtained using industry recognised tests and a new test that uses future fuel injection system design.

Internal Diesel Injector Deposits (IDID) in compression ignition engines have been widely studied in the past few years. Published results indicate that commonly observed IDID chemistries may be replicated using full-scale engine tests and subsequently fuel injection equipment (FIE) operated on non-fired electric motor driven test stands. Such processes are costly, complex and by nature can be difficult to repeat. The next logical simplification is to replicate IDID formation using laboratory-scale apparatus that recreate the appropriate chemical reaction process under well controlled steady state conditions. This approach is made more feasible by the fact that IDID, unlike nozzle hole coking, are not directly exposed to gasses involved in the combustion process. The present study uses an instrument designed to measure thermal oxidation stability of aviation turbine fuels to successfully replicate the deposit chemistries observed in full-scale FIE.