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Simulation of cavitation and erosion in fuel injection systems of medium/heavy duty Diesel engines at injection pressures reaching 3000bar

Final Report Summary - FUELSYSTEM3000 (Simulation of cavitation and erosion in fuel injection systems of medium/heavy duty Diesel engines at injection pressures reaching 3000bar)

(Please find a detailed Final Report attached)

1. Executive summary

Current technological trends in the Diesel engine industry indicate that increased fuel injection pressures lead to reduced NOx and PM emissions. However increased fuel injection pressures lead to the appearance of fuel heating and catastrophic cavitation phenomena inside the fuel injection systems and particularly inside the injectors, which are associated with loss of efficiency, material erosion and reduced injector operating life. The present IAPP project has achieved the following:
• Shed light into the mechanisms of material erosion due to cavitation through the mechanisms of bubble creation and implosion;
• Developed indexes for industrial use of identifying the flow regions prone to cavitation (Cavitation Aggressiveness Index) and erosion (Erosion Aggressiveness Index) and identified conditions for a free cavitation operation of industrial injectors, thus extending their operation life.
• Tested various cavitation models and assessed the predictive capability for flows inside injectors.
• Assessed extreme injection pressures on Diesel fuel injector characteristics; these can lead to high fuel temperatures, due to internal friction and even boiling, which may impose an upper limit on injection pressure. Heat transfer from the engine walls to injector can lead to excessive fuel temperatures and to fuel boiling.
• Developed guidelines for an erosion-free injector design; the later has been produced/manufactured by the industrial partners.

Apart from the scientific part outlined above and equally import the project contributed to:
• A new generation of researchers with skills on computational fluid dynamics and advanced experimental techniques has been created through collaboration with industrial partners, secondments in the industrial environment and educated in problem solving of financial and social impact. The interaction with publicity media transferred their technological knowhow to the public and made them aware of the engineering areas sensitive to the public and which must be or are addressed by the research community.
• Through the present project apart from the scientific new knowledge created, the industrial partners benefited from their collaboration with Academia, acquiring improved design tools as regards new generation injectors for high fuel injection pressures with improved operation life, thus increasing the competitive advantage of the industry on a European and global scale.
• The researchers with their outreach activities made aware to the public the social and economic benefits that their research had on the environment, which is expected to have a positive effect on European competitiveness. Further to that the allocated website will be updated and will be online to disseminate the activities and findings of the project further (

2. Description of project context and objectives

2.1 Project context (Based on the project proposal)
The proposed work and finally the work conducted represented a balanced portfolio between:
• knowledge transfer of existing state-of-the-art Fuel Injection Equipment (FIE) design, manufacturing and testing as well as computational models predicting cavitation erosion sites within the framework of multi-dispersed CFD flow solvers and
• research advancements in this area, aiming to develop new and more accurate models that will be validated against new and well monitored experimental data.

The programme explored fundamental aspects of cavitation such as the influence of bubble collapse processes within fuel injectors on the pressure/temperature levels developing on nearby wall surfaces. Based on this knowledge, we explored the potential of designing new and more efficient nozzles that show improved flow characteristics with respect to their resistance to cavitation erosion. The experiments which have been performed, building upon existing experience, were new to the relevant industrial sector and thus, they offered improved physical understanding. New models have been implemented into the state-of-the-art CFD code developed over the years within the research groups of the applicants and became an integral part of the design tools developed. Figure 2.2 shows the work flow of the overall methodology as it was in the original proposal and which has finally implemented. The whole project was monitored and managed by the activities of the corresponding dedicated work package (WP7); only own resources of the partners (i.e. not Marie Curie fellows) were allocated on this WP7, which aimed to coordinate the activities, review progress with representatives of the partners at the set milestones, support reporting and communication towards the project officer and perform quality control on project content and deliverables. WP1 represented the first stage knowledge transfer activity and aimed to set-up the scene of the detailed work (to be performed) which was performed. It led to the identification of training needs for the industrial and academic partners, communication of experimental data and simulation tools already available, product specifications for meeting the foreseen technology trends, description of existing experience from current modelling capabilities, decision on the new tests to be performed and the new model development, implementation and testing. In this work package the secondments of staff starts. It also deals with all required training activities for the newly recruited as well as for the seconded Marie Curie fellows; these represent ~6% of the total man-months supported.

Training feeded to all other WPs at various stages throughout the duration of the project; for the seconded fellows, this consisted of one month basic training while the newly employed fellows received 3 months of training by their corresponding institutions.
WP2, WP4 and WP6 represented the three main knowledge transfer work packages; the man-months in these work packages represented approximately 44% of the requested man-months support, which was the largest planned activity. Knowledge transfer was inter-sectoral. The expertise of the industrial partners on Diesel engine technology, FIE design, manufacturing and testing was communicated to the academic partners at very detailed and project specific level. Experimental data for well controlled and monitored operating conditions included fuel injection pressure, injection flow rate and images of cavitation erosion for different injector nozzles designs as function of hours of operation. On the other hand, the expertise of the academic partners on simulation of cavitating flows and heat transfer processes in two-phase flows that are available within the corresponding institutions have been transferred to the CFD solver of the industrial partners. These numerical tools have been validated against the experimental data and have been further utilized in assisting in the design on new durable fuel injector nozzles. As a follow-up, the industrial partner has manufactured the proposed injector nozzles and performed durability experiments aiming to verify the findings of the simulation tools and prove their validity.
The research work was planned within WP3 and WP5 and referred to the development of new boiling heat transfer and cavitation erosion models applicable to fuel injectors. Research addressed the physics of compressible bubble cloud dynamics that included thermal effects and heat transfer to/from the surrounding fluid. Collective bubble dynamics effects were given special attention, as these processes lie on the heart of the cavitation erosion predictions in flow environments where multi-million clouds of bubbles are present. Finally, WP8 was devoted to the dissemination activities. These are carefully planned and finally executed through the wide networks of the partners. In brief, these activities aimed to promote and communicate the results of this project though workshops, conference presentations, scientific journal publications and well planned outreach activities.

2.2 Project Objectives
The primary objective for the work envisaged in the 4 years of the programme and which was implemented was to transfer the existing state-of-the-art knowledge on cavitation bubble dynamics leading to cavitation erosion as well as convective/boiling heat transfer processes to the design process of Diesel fuel injectors. More specifically, the proposed research targeted the following objectives:
1. Identify the problems and areas of concern of the industrial partner products and the applicability of existing simulation tools to resolve them.
2. Train the seconded and recruited researchers to the various activities and areas of expertise of each partner.
3. Produce an experimental data-base of cavitation erosion initiation and temporal development for medium/heavy duty Diesel engine injectors under controlled and monitored operating conditions; such data will be used and have been used for validation of computational models.
4. Transfer the knowledge and evaluate the predictive capability of cavitation erosion models as implemented in computational fluid dynamics (CFD) codes used by the academic and the industrial partners.
5. Extend the current cavitation bubble dynamics models to include pressure/temperature effects on the development of cavitation bubble clouds.
6. Transfer the knowledge of boiling heat transfer simulation tools able to describe the heating caused by the friction between the flowing liquid and the solid walls of the injector.
7. Design durable nozzles with the aid of the integrated simulation tools.
8. Disseminate the knowledge that will be acquired through the research activities and the engineering tools it develops through publications in international workshops, conferences and leading scientific journals.

3. The Social-Economic potential impact of the project

The project involved the collaboration of research institutes and industrial partners.
Societal and technological pressures drive research, which is funded for creating
• New scientific knowledge
• Improve the knowledge based economy
• Create technological innovations
for improvement of the technological competence of the industry and in final analysis for the benefit of the wellbeing of people.

3.1. Societal pressures
The increasing concern of society for environmentally friendly internal combustion engines and the constantly increasing environmental legislation for a healthier living environment represent the main societal pressures on industry for cleaner internal combustion engines. The consumer pressure for cheaper transportation costs drives industry to energy efficient engines.

3.2.Technological pressures
Industry’s response to meet the above societal pressures, among the other technological measures it takes, is by investigating the incorporation of advanced injection pressures into the fuel injection equipment of ICE. By doing so, reduced CO and NOx emissions can be achieved as also more efficient engines and reduced CO2 greenhouse gases. Apart from the above, by incorporating the state of the art into the design process keeps European Technology at a competitive technological advantage.

3.3. Collaboration outcome
The research and technological outcome of the project has been analyzed and described in this report and it consists of proof of concept that the increased fuel injection pressures in ICE meets all the societal and technological pressures outlined above and through manufacturing of prototypes proved that a new generation of fuel injectors of improved design can operate in high injection pressures, have competitive advantages, extended operational life, improved efficiency and reduced environmental pollution.

3.4. Social-Economic Impact of the project-Beneficiaries
The present publicly funded research has produced major scientific and industrial findings of benefit to Science, Technology and Society.
a. Science
b. Technology
c. Society

3.4.1. Scientific Impact
The scientific impact of the project can be quantified by its published account, as it is numerated by the number of scientific publications in Journals, conferences, scientific meetings; the number of scientific publications of the present four-year project accounts to more than 15 in lean scientific journals, participation in 13 scientific conferences around the globe and in a large number of publicly available deliverables. Due to the number of innovative concepts the project has produced, it is expected that its scientific impact will soon become evident through the science citation index in an measurable way.

3.4.2. Technological Impact
The technological impact of the project is distinguished in short and long term.
In short term, the industrial partners of the project have benefited by
• The transfer to industry from the academic partners the developed technological know-how, above the current state of the art, which allows it to design advanced, more efficient and more durable fuel injection systems; thus the industry has ackired an increased technological competitive advantage, improving its position in the European and global markets.
• The training of the industrial personnel from the experienced researchers and the job secondements to industry improved the knowledge based design capability of the industrial partners; as a sequence improved their design skills, their attitude in innovative thinking and materialization concepts; the training created skilled workers for the todays knowledge based economy.
The long term technological impact of the project will be evident with the diffusion of the produced new technological know-how into the European industry by incorporating into the design of fuel injection systems the new concepts which have been produced and which the industrial partners of the project already enjoy. This will eventually when the new fuel injectors are mass introduced into the market will
• Improve the competency of the European Industry in fuel injection systems and maintain its global leadership into the market
• Improve the knowledge based industrial and scientific basis for a competitive economy
• reduce the environmental impact
• Improve the environmental health standards

3.4.3. Societal Impact
Below is outlined the project impact in society.

a. Knowledge production and diffusion
The project created a wealth of scientific information which has been diffused into a much larger body of the society throughThe scientific publications
• Outreach activities, among others, school visits
• Organization of international conferences, like the conferences of the International Institute of cavitation Research & DIPSI workshop
• Training seminars not only on scientific matters but also on oral and writing communication, patent procedures etc.
• Creation of a web site particularly dedicated to the project

b. Impact on employment
The project has generated highly skillful researchers who improved their employment ability in finding new jobs either in the university sector or in industry. (4 of them currently working in the industry, 2 were appointed lecturers in the academia, 2 received individual Marie Curie projects)

c. Collaboration links
• The project strengthened the links between the university and the industrial partners and improved the level of trust in exchanging confidential information;
• these links of collaboration were further developed in NEW research projects either in bilateral agreement or through European funds.
• new collaborations with new industrial and university partners have been created which have led to new collaborative projects and share and exchange new knowledge

d. Environmental benefits
The new generation of the fuel injection systems will allow the European ICE industry to meet stringent environmental regulations as regards CO, CO2 and NOx emissions into the environment from transportation, thus Citizens of the world will have a healthier environment and improved life expectancy.

e. Economic benefits
The improved durability of the fuel injection system and reduced CO2 emissions accompanied by increased fuel efficiency will have an immediate benefit to the economy as these new designs are introduced into the market will benefit people who will reduce transportation costs and maintenance costs of their ICE. Apart from these, European industry will improve its global leadership into the market increasing its competitiveness.

f. Partner position in the market
A highly welcome outcome of the project is that the project has improved the market position of the partners in the competitive world market; the research partners have benefited by the advanced experimental and computational tools which the project has created and the International Institute of cavitation research has been established as world leader in bubble dynamics and erosion of fuel injection systems. The industrial partners improved their market position by new design capabilities in creating new generation of fuel injection components, with characteristics giving the industry competitive market advantages; for both market improvements, finally Society will be benefited; at the end, it is the Society which supported the research effort.