Combustion

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Note: The course is aimed at students wanting to master the basics of combustion technology. For this endeavor a sound knowledge of fluid mechanics, heat and mass transfer and thermodynamics is needed. Given some extra effort limited deficits in these pre-requisites may be filled up under the guidance of the instructor.

The students know the basic concepts of combustion. They can do the basic thermochemical and fluiddynamical calculations of combustion systems. They master the basic design and scaling of combustion systems. With their fundamental understanding of the processes in flames they can analyze existing combustion systems and solve problems occurring with them.

Reactive flow occurs in many areas of engineering. Its application spectrum ranges from reactors in chemical process technology to rocket motors. Pivotal to all is the chemical conversion of matter under the conservation laws of mass, momentum and energy. The lecture introduces the basic description of reactive flow on the example of steady constant pressure combustion in flames, which has a broad application in chemical synthesis, industrial process furnaces, gas turbine engines, stovetops and heating appliances. The global balances of combustion introduced in Thermodynamics I+II (stoichiometry, species- and element- balance, enthalpy of formation and heat of reaction) are shortly revisited. The reaction kinetics of the gas phase are then explained using the collision model leading to the Arrhenius law and the net formation rate. The chemical equilibrium as the limit process of combustion and its relation with the thermodynamical equilibrium is presented. Then the typical sequence of combustion kinetics (start-, chain- and recombination rections) are introduced and shown in classical mechanisms. The resulting methods of simplification (partial equilibrium and steady state) are illustrated. Structure and description of laminar diffusion and premixed flames lead to the simultaneous treatment of transport, mixing and heat release focussing on the development of the characteristic parameters of the process. An introduction into using the Freeware CANTERA allows interested participants to extend the basic skills from paper and pencil to general application. An brief excursion into the phenomena and characteristics of turbulent flows provides the necessary basis for the technically most relevant turbulent flames. These are then introduced with examples of actual comustion systems and characterized with the respective characteristic turbulence parameters of the process. A short survey of turbulent combustion modelling concepts underlines their relevance. The processes occurring in two phase combustion systems are being touched upon focussing on the simplified treatment of single droplets and particles. Finally the formation and control of air pollutants and the influence of the technical combustion design are discussed. Parallel to the lecture exercises are being offered which pick up the previous lecture content with a typical example.

Participants should have a basis in thermo- fluiddynamics. Principles as the first and second law of thermodynamics, the balances of mass, momentum and energy and the basics of heat and mass transfer should be available in the sense that these concepts will be not be introduced anymore in detail but only recapitulated by example. Given some extra effort limited deficits in these pre-requisites may be ironed out under the guidance of the instructor.

An interactive presentation and the lecture notes provide the basis for self-study.
Resulting questions can be clarified in during the lecture, the exercises and consultation hours. An introduction to the software CANTERA allows the participants to transfer the basics learned in simplified settings to fully complex reality. Demonstrations of model flames and relevant effects.

Written exam (in german). It comprises 30Min closed book short questions without calculations and 60Min open book design calulations where a non-programmable hand calculator is allowed. Foreign students may bring a dictionary and ask the examiner for clarifications.

Stephen Turns: "An Introduction to Combustion", McGraw Hill