CFD INVESTIGATIONS OF MIXTURE FORMATION, FLOW AND COMBUSTION FOR MULTI-FUEL ROTARY ENGINE Von der Fakultät für Maschinenbau, Elektrotechnik and WirtschaftsIngenieurwesen der Brandenburgischen Technischen Universität Cottbus
zur Erlangung des akademischen Grades eines Doktor-Ingenieurs (Dr.-Ing.) genehmigte Dissertation vorgelegt von Master of Science Husni Taher Izweik Geboren am 15.12.1954 in Zawia, Libyen
Vorsitzender: Gutachter: Gutachter:
Prof. Dr.-Ing. P. Steinberg Prof. Dr.-Ing. H.P. Berg Prof. Dr. E. Sigmund 18.11.2009
Tag der mündlichen Prüfung:
I dedicate this work to my family, my wife, and my children
Powerful, smooth, compact and light combined with multi-fuel capability are the main features of the rotary engine. The Wankel engine superb power-to-weight ratio and reliability make it not only suitable for automobile application, but also particularly well suited to aircraft engine use and it can replace the reciprocating piston engine in many areas of use such as sport cars, motorcycle, boats, and small power generation units etc. Since the physics that taking place inside Wankel engine combustion chambers are exceedingly complex, a numerical CFD studies were obtained to understand the unsteady, multidimensional fluid flow and fuel-air mixing inside the combustion chamber of the Wankel rotary engine during the intake and compression cycles. The effects of the engine combustion chamber design and operating parameters on fluid flow and fuel-air mixture formation were investigated: engine velocity, direction of fuel injection into the combustion chamber, with emphasize on diesel and hydrogen injection fuels. The injector nozzle size, injected fuel velocity, the position of injector and angle of injection were also investigated. A well known CFD Code AVL-Fire v7.x and v8.x with its moving mesh capability was used to simulate one rotor side, presenting the intake and compression stroke. The CFD-Code is capable of simulating the complex movement of the rotor and calculates the fluid flow parameters; temperature, pressure, velocity, volume changes and combustion variables. The k-ε model is the most widely used turbulence model in practical engineering applications and was used by the code to calculate the flow variables. A variety of ignition and combustion models available by this code including: eddy breakup or magnussen model, coherent flame (CFM) model, PDF model, and TFSC model. The fire combustion module enables the calculation of species transport/mixing phenomena and the simulation of combustion in internal combustion engines and technical combustion devices under premixed, partially premixed or a non-premixed conditions. In combination with fire spray model, the combustion module enables the calculation of spray combustion process in direct injection engines; where mixture formation and combustion are simultaneous process exhibiting a significant degree of interaction and interdependence. The droplet breakup models available with suitably adjusted model parameters are highly recommended for this type of application.
In previous work conducted by Fushui Liu , in this chair of combustion engines and flight propulsion, at BTU-Cottbus, the fire code has been validated and approved for high velocity gas injection of hydrogen and it helps to choose and adjust the different model variables for hydrogen injection. A geometrical data of a new family of compact, lightweight Wankel engine for multipurpose applications were designed and are currently under an optimization test was used in this research work. In the first part of this research simulation work, concentration on understanding the flow field inside the combustion chamber is a part of this research work to help understanding engine fuel injection configuration. The engine is capable of burning different kind of liquid and gas fuels.
The diesel fuel is the most extreme liquid fuel and more complicated in comparison...
References: AVL Fire, Species transport, Version 8, July2003. Loyd, R., Curtiss-Wright Corp., R.C. Engine Division. Wood-Ridge. N.J. 07075,
Curtiss-Wright Stratified Charge Rotary Engine Development, Combustion Science and
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