Purpose, Objectives, and Key Question

Alternative fuels have been intensively introduced in transportation sectors in recent years. While some of the wear caused by these fuels can be seen initially, the problems really become clear after years of application. The goal of this task was to identify and present an overview of potential wear issues to prevent major surprises in the future.

The Task evaluated excess wear in internal combustion engines caused by the use of alternative fuels. The objectives were to review ongoing related projects in the member countries and conduct a general literature review to evaluate which engine wear problem that can be foreseen with future application of alternative fuels.

The key questions to be addressed were as follows:

• How severe are the problems associated with use of alternative fuels?
• What is the expected increase in engine wear caused by these fuels?
• What can be done to solve these problems?

Activities

General literature review

A general literature review for alternative fuels, focusing on those relevant to ongoing studies related to engine applications in the countries involved in the task was completed: methanol, ammonia, and bio-oils, among others.

In the literature review, the available information and report it in a structured way that supports future application of alternative fuels were compiled.

On-line seminars

Activities related to engine wear are ongoing in the involved AMF countries. These studies have been communicated through presentations from the responsible “activity” persons (or other designated people) at frequent seminars. The results from the seminars provided a background for the literature review report.

Key Findings

For biofuels suitable for diesel combustion the major problems are associated with dilution of lubricant with fuel, the fuel tends to biodegrade, and corrosive nature is seen towards some materials.

For ethanol, wear conditions are worsened due to lowering lubricant viscosity and due to water content in the lubricant. Ethanol, furthermore, reacts with the lubricant. This increases the acidity of the lubricant and the breakdown of some lubricant additives. On top of this, increased water content of ethanol, which is often seen, increases engine corrosion.

For methanol, the same issues as for ethanol with water is seen. Chinese experiences conclude on more specific material issues which are summarized in Table 6. Furthermore, formation of formic acid has a negative impact on anti-wear performance. Methanol, lubricant and water forms an emulsion at low temperatures which can cause lubricant to fail. Lubricants needs improved alkali values and antioxidant properties for the engines to work properly. Finally, spark plugs undergoing pitting and ablation is seen.

Hydrogen is reported to cause surface embrittlement, fuel injector failure (due to bad lubricity) and prevention of formation of surface protective oxides. Furthermore, hydrogen is seen to decrease lubricant additive content in many different ways, and it can cause emulsification of the lubricant. Finally, excessive wear is caused by water condensation on the cylinder liner.

Ammonia is a relatively new fuel for combustion engine applications. Therefore, much more experience is needed to describe the fuel impact on wear completely. However, corrosion effects on copper alloys are reported, and it is expected that this is also the case for other materials. Increase in lubricant viscosity has been reported, caused by amines, and high water content in the exhaust is expected to cause excessive wear due to water condensation on the cylinder liner.

DME was seen as a highly relevant potential fuel to substitute diesel in the early 2000´s. The problems with DME is that it is an excellent solvent which can cause damage to most materials. However, materials resistant to DME have been identified due to huge interest in applying DME in the early 2000´s. DME’s low lubricity has caused surface wear in the fuel injection system. Additives have been developed to mitigate this problem.

Main Conclusions

The project results identified and added to the understanding of the high degrees of wear caused by use of alternative fuels in engines used in the transportation sector.

Publications

Key Messages have been published already, Final reports will follow by the end of 2024.