Moteur Diesel

Résumé

Le moteur Diesel, appelé également moteur à allumage par compression, est un moteur à combustion et explosion dont la combustion est déclenchée lors de l'injection de carburant dans la chambre de combustion, par un phénomène d'auto-inflammation. Celui-ci est permis par les températures de , atteintes par la compression de l'air dans les cylindres jusqu'à un taux de compression de 14:1 à 25:1. Des bougies de préchauffage sont souvent utilisées pour le démarrage à froid des petits moteurs, qui créent un point chaud facilitant le déclenchement de l'inflammation du mélange air-carburant. Pour les moteurs de bateaux et les gros moteurs fixes à fioul lourd, on chauffe celui-ci à haute température pour permettre le démarrage. Le moteur Diesel tire son nom des travaux de Rudolf Diesel entre 1893 et 1897. Le moteur Diesel peut être soit à deux temps (surtout sur les navires, avec suralimentation par compresseur et injection pneumatique), soit à quatre temps, notamment dans les véhicules rout

Source officielle

https://fr.wikipedia.org/wiki/Moteur_Diesel

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Evaluation of the State-of-the-art of Biomass gasification for heat and electricity production

In the order to produce energy for the large amount of people still currently out of the national girds, different possibilities exist. For practical and economic reasons, the most popular one is the use of Diesel engines coupled with generator sets. Petrol reserves being not infinite, renewable solutions have to be found to insure a sustainable development of the poorest areas in the world. One of those could be the gasification of biomass. The latter has two advantages: Biomass is a renewable energy source and is present almost everywhere in the world: the gas produced can have various applications among them fuel for unmodified Diesel engines. Unfortunately, things are not so simple: the gas produced has a low heating value, its use in an internal combustion engine requires cleaning, biomass is not uniform through the world and technology has to be adapted for each properties, biomass supplying can product to environmental hazards if it is not strictly controlled, etc. Moreover, no standardization exists currently for the development of the technology. However, positive results have been obtained and it seems that interesting opportunities exist for the future. It requires further investments and global communication between the protagonists. The present study tries to give a complete overview of the current biomass gasification field. Some important results obtained on existing gasification plants, as well as problems encountered on technical, social, environmental and economic point of view, are also presented. Finally, some promising alternatives are proposed, as well as the main required research.

2001

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SPS: Projet d'une minicentrale pilote électro-thermo-solaire de 10 KWe.

Daniel Favrat, El Hadj Malick Kane

This report presents the field tests synthesis of a small Hybrid Solar Power Plant integrating three technologies : hermetic volumetric scroll expander - generators working with two superposed Organic Rankine Cycles (ORC) a cogeneration group composed by a Diesel engine coupled with an asynchronous generator with heat recovery at two levels of temperature and a solar field made of plate concentrators. This type of hybrid power plant is mainly intended for rural electrification purposes in developing countries or cogeneration in applications like heating swimming pools in other countries. After having been tested separately, the three main components of the plant (Concentrators, ORC and cogeneration group) have been coupled in a field on the EPFL campus in Lausanne (Switzerland) in order to allow experimentation of the entire installation with real conditions. The general concept is promising, thermal cycles being quite robust and adapting well to the very variable solar conditions, and this for the two working modes (Solar and Hybrid). In terms of performances, results have been encouraging, even if improvements are still necessary. Expanders worked at part load, the concentrating surface having been under-dimensioned and there are no doubts results could be achieved with better adaptation between these two elements. In hybrid mode, fuel energy was transformed up to 40.5 into electricity, opening good perspectives for the future including with other cogeneration technologies like micro gas turbines or medium to high temperature fuel cells.

2001

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This paper presents field tests of an original concept of a small hybrid solar power plant integrating three technologies: hermetic volumetric scroll expander-generators installed in two superposed Organic Rankine Cycles (ORC), a (bio-)Diesel engine with heat recovery exchangers and a solar field made of two rows of sun following flat plate concentrators with vacuumed isolated collector tubes. The basic idea of the concept is to exploit the synergy between equipment, use cheap and maintenance free expander- generators, guaranty power availability at all time and improve the efficiency of the engine when it has to operate alone at night time by converting the waste heat with the solar ORC. This type of hybrid power plant is intended for rural electrification purposes in developing countries or cogeneration in applications like heated swimming pools in other countries. Pressurized hot water is used at this time as a thermal fluid in the collectors with HCFC123 in the topping cycle and HFC134a in the bottoming cycle. The field tests have been performed during the summer 2001 in Lausanne (Switzerland) and the pland proved operationally reliable. However performance results (with exergetic efficiencies up to 45%) did not meet the expectations but measures to improve the concept have been identified.

2002

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