Community Research and Development Information Service - CORDIS

H2020

ARGOS Report Summary

Project ID: 714030
Funded under: H2020-EU.3.4.5.5.

Periodic Reporting for period 1 - ARGOS (Aerospace propeller useful for diesel engines with extreme excitation of vibrations)

Reporting period: 2016-06-01 to 2017-06-30

Summary of the context and overall objectives of the project

The 714030-ARGOS project is aimed at a new aerospace propulsion unit based on a compression ignition (diesel) engine. The specific problem solved by ARGOS is the design of a direct drive propeller capable to withstand the increased level of torsional vibrations of a piston engine producing high power on low rotational speed of crankshaft.
The main advantages of such a propulsion unit are low fuel consumption that allows significant increase of the flight radius of the aircraft without serious impacts to the airframe design, lower fuel flammability important during accidents and better availability of certified jet fuel worldwide compared to certified avgas fuel. One of the most important properties is also the low noise produced by the slowly rotating propeller.
Of course such a propulsion unit has also disadvantages given by the specific properties of piston engines with the diesel working cycle. The power produced by the engine is given by the torque moment and its fluctuation during one revolution of the crankshaft together with rotational speed of the crankshaft. The same power produced on lower rotational speed of a diesel engine requests higher torque moment peeks than the torque moment peeks produced by equivalent avgas engines working on higher rotational speed.
Simply said the diesel engines need propellers capable to withstand increased level of torsional vibrations of propeller shaft. The propellers originally developed and certified for avgas engines usually suffer by fatigue-life problems when adopted to diesel engines.
Fuel consumption reduction, lower noise emissions and low operational cost of the aerospace diesel engine propulsion unit and therefore of the aircraft using it are in great accordance with preferences of modern society who is gradually increasing its demand on transport activities.
The main objective of the project is to design a new propeller and a governor useful for diesel engines with optimized aerodynamics to provide maximum propulsion efficiency for the specific working conditions of the engine and also capable to work with the increased level of torsional vibration excitation without negative impacts to fatigue-life properties of the propeller.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The first project period was devoted to the comparison of equivalent avgas and diesel engines mainly from the point of view of excitation of torsional vibrations and to the corresponding response of the propeller.
The data measured on different engines prove significantly increased level of torsional vibrations and corresponding increase of cyclic components of stress measured on the propeller parts. On the other hand the increased level of vibrations is given mainly by the different rotational speed and number of cylinders. The influence of different work cycle (compression ignition - diesel) seems to be less significant. A more detailed analysis of this fact will be done in the next phases of the project because better understanding of the dependences would allow better exploitation of experimental data from different projects for future propeller development.
The main output of the first period is the definition of design specifications and development plan. The output provides basic rules for the propeller design and continuation of experimental work to meet the project objectives.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Important data files were obtained during the first period of the project. It is necessary to point out that most of the currently produced modern propellers were optimized based on avgas engine parameters corresponding to the state of art from the middle of the last century.
Typical direct drive avgas engine has maximum rotational speed between 2600 and 2750 RPM and it is known that some of the (direct drive) engine projects were working with the rotational speed exceeding 3000 RPM. Such development goes against the requirement to reduce noise emissions of new aircrafts and also limits the flight performances of aeroplanes. The high rotational speed lowers maximum flight velocity of aeroplanes because of the problems with the maximum permitted Mach number at the propeller blade tip.
The aerodynamic analysis done during the first reported project period proves that propeller blades optimized for the lowered rotational speed of diesel engines provide better propulsion efficiency than the blades originally optimized for avgas engines when simply adopted to the diesel conditions. Noise emission analysis also proves better parameters of the new propeller because of the lower speed of the blade tips, i.e. due to the lower blade tip Mach number, and also because of the lower frequency of emitted noise which is important for the results of noise expressed by means of filter “A” weighted values of pressure level. Filter “A” reflects the specific properties of human hearing, i.e. the ability to suppress some tones and to increase the influence of other tones to the life comfort of people.

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