A PAH growth mechanism and synergistic effect on PAH formation in counterflow diffusion flames

Preliminary design studies indicate that a cruise-efficient short takeoff and landing aircraft has enhanced takeoff performance at competitive direct operating costs when using high-speed propellers in combination with internally blown flaps. The original tractor configuration is compared to an over-the-wing propeller, which allows for noise shielding. An additional geometry with partially embedded rotor similar to a channel wing is considered to increase the beneficial interaction. This paper shows the aerodynamic integration effects with a focus on climb performance and provides an assessment of the three aforementioned configurations for a simplified wing segment at takeoff conditions. Steady Reynolds-averaged Navier–Stokes simulations have been conducted using an actuator disk model and were evaluated based on the overall design. Interacting with the blown flap, the conventional tractor propeller induces large lift and drag increments due to the vectored sliptream. Although this effect is much smaller...

Aerodynamic Installation Effects of an Over-the-Wing Propeller on a High-Lift Configuration

A skeletal mechanism for kerosene combustion with aromatic ring formation for the following operating conditions of pressure, temperate and mixture ratio - 1bar < p < 60 bar, 900 K < T < 1400 K and 1.0 < Ф < 2.0 - has been developed and validated applying a broad experimental data base. The input model with 179 species and 1180 reactions was reduced to skeletal model with 118 species and 814 reactions without lost of predictive capabilities and than to short model which comprised the necessary 40 species and 208 irreversible reactions. All elaborated models predict satisfactory heat release and aromatic molecule formation in reference fuels.

Skeletal Mechanism for Kerosene Combustion with PAH Production

The skeletal reaction mechanism for methane combustion is developed to be applied in the CFD simulations of rocket combustion chamber under pressure 20 bar. The used reduction procedure analyses the model behavior under different pressures, temperature and equivalence ratios and selects the reaction and species those are redundant simultaneously for all studied processes and parameters. The rate of production analysis and sensitivity analysis were applied to simulations of experimental targets for ignition delay times (65 points) and laminar flame speed (15 targets) in intervals of p5 = 1-50 bar, T5= 940-210K, and p = 1-60 bar, T0= 300K, correspond. The input detailed mechanism with 41 species (including Ar, He and N2) and 298 reactions has been reduced to the skeletal model with 24 species and 100 reactions. This kinetic mechanism is applicable for simulations of a wide range of combustion parameters. INTRODUCTION I. Within the last ten recent years, the propellant combination LOX/CH4 has received considerable attraction worldwide as a propellant combination for space propulsion applications [1-5]. The advantages are numerous: a better specific impulse than that of oxygen/kerosene, reduced cost and complexity in in handling compared to hydrogen and reduced requirements for turbomachinery. In Germany, this propellant combination is investigated both experimentally and numerically within the collaborative research center TRR40 on ‘Technological foundations for the design of thermally and mechanically highly loaded components of future space transportation systems’ [6-8]. Within this project, specific effort is put on developing design tools for thrust chambers which requires validated numerical tools for the prediction of combustion and heat transfer in such devices. In an effort to compare different numerical approaches, a special workshop will be organized later this year at the Technical University of Munich where teams from all over the world which apply RANS, URANS, LES and hybrid models will try to reproduce combustion efficiency and heat transfer of a test case provided by one of the TRR 40 projects [9]. Generally, different groups use not only different approaches to handle fluid mechanics as mentioned above, but also their way to treat combustion differs substantially. In order to allow more detailed comparisons of the applied numerical tools, a reduced chemical kinetic scheme has been developed and will be provided to the workshop participants. The extremely large CPU times for CFD calculations with detailed chemical mechanisms necessitate that the applied kinetic models must be as simple as possible. However, any accurate modelling of diffusion flames and in general combustion processes in liquid propellant rocket engines are of this type requires that the chemical model must be able to sufficiently describe these combustion processes for a wide range of parameters: propellant mixture, temperatures and pressures. Obviously, such a reduced mechanism can be generated only on the base of large number of different calculations, which integrate the calculation of chemical processes (ignition delays, flame speeds, concentration profiles in chemical reactors) and sensitivity analyses of different model outputs to the system parameters. The presented work results of such a reduction of a methane (CH4) / oxygen (O2) reaction mechanism reduction. KINETIUC MODEL AND REDUCTION PROCEDURE II. The input detailed mechanism is a part of the DLR reaction data base [10], which was validated and optimized on the different experimental data for the C1C16 hydrocarbons which present n-,i-paraffines, naphthenes and aromatics. The divided CH4 sub-model has 41 species (including Ar, He and N2) and 298 reactions. The reduction strategy is based on the modeling and sensitivity analyses of experimental points obtained under different conditions. To construct a skeletal mechanism, applicable for the CFD simulations of rocket combustion chamber under pressure 20 bar, the selected experimental targets for ignition delay times (65 points) cover the interval parameters of p5 = 1-50 bar, T5= 940-210K, forlaminar flame speed (15 targets) p = 1-60 bar, T0= 300K,  The global sensitivity analysis implemented in the inhouse developed RedMaster code [11] has been applied to reduce the basic mechanism to the skeletal one. RedMaster code manages the calculation of chemical processes with CHEMKIN code [12] and the calculation of sensitivity coefficients with procedures from KINALC code [13]. The multi target reduction strategy realized in the RedMaster code, Fig.1, allows determination and elimination of unimportant species and reactions on the basis of integrated information obtained from the mechanism sensitivity analysis performed for ignition delay time and laminar flame simulations at different time points of the studied processes. A species is considered redundant if its concentration change has no significant effect on the production rate of necessary species. The influence of a change of the

/pdf/methane-skeletal-mechanism-for-space-propulsion-applications-421psoye4o.pdf

Methane Skeletal Mechanism for Space Propulsion Applications

In this contribution, we present aeroacoustic experiments concerning installation effects of propellers. Such installation effects are important as they can significantly alter the sound radiation as compared to an isolated propeller. For this purpose, detailed experiments have been conducted in the NWB aeroacoustic wind tunnel in Braunschweig, Germany. The considered geometry is a nine-bladed propeller installed in front of a high-lift
wing (employing a Coanda flap). The results illustrate the influence of propeller rotational speed, blade pitch angle, wind tunnel velocity, and angle of attack variations on the sound radiation. Furthermore, with a source localisation technique insight is gained in the dominant sound sources, and reveals the importance of periodic as well as broadband noise for the considered geometry.

/pdf/installation-effects-of-a-propeller-mounted-on-ahigh-lift-1c83qnnjmi.pdf

Installation Effects of a Propeller Mounted on aHigh-Lift Wing with a Coanda Flap. Part I:Aeroacoustic Experiments

Due to increasing airport congestion the German research project 'Burgernahes Flugzeug' (BNF, citizen friendly airplane) investigates the potential of aircraft for a possible future air transportation system integrating small airports. Key technologies like aerodynamics for developing new generation quiet, efficient, short take-off and landing (QESTOL) aircraft are meant to be made available via Computational Fluid Dynamics (CFD) and new wind tunnel data. Subject of these studies is a generic twin-engine single-aisle confguration with an active high-lift system and a turboprop propulsion system. With respect to aerodynamics,
the possible benefits of the propeller slipstream interaction with the fow field around an active high-lift wing are explored. The first step, the propeller design for the turboprop propulsion system of the aircraft is conducted taking aerodynamic and aeroacoustic constraints into account. This propeller is scaled down to suit a wind tunnel (w/t) model with
an active high-lift wing. Aspects of the integration of the turboprop propulsion system on the wing half model and instrumentation of the propeller wind tunnel model are examined.

Propeller Design for a future QESTOL Aircraft in the BNF Project

The German Burgernahes Flugzeug (Citizen-Oriented Airplane) research program advances technologies for high-lift systems using circulation control Coanda-type flaps. The interaction of these high-lift systems with a propeller engine is the subject of the present work. A large and complex wind-tunnel model equipped with an active high-lift system and a powered propeller was designed, manufactured and instrumented. The wind-tunnel data show the potentials of the active high-lift system in three-dimensional wing applications. The results characterize and quantify the interactions between a propeller and a high-lift wing by using systematic variations of blowing momentum and propeller thrust. The results represent a unique database for future efforts to improve the efficiency of active lift and for validation of numerical simulation methods.

Aerodynamic Effects of Propeller Slipstream on a Wing with Circulation Control

Within the German BNF research project a generic twin-engine configuration with an active high-lift wing and modern turboprop engines is investigated. This paper deals with high fidelity RANS computations of the wind tunnel configuration measured in previous measurement campaigns. The simulation data is in good agreement with the experiment. The presented investigations focus on the jet flow due to the internally blown flap and the propeller slipstream.

Propeller and Active High Lift Wing Interaction in Experiment and Simulation

Due to increasing airport congestion the German research project ’Burgernahes Flugzeug’ (BNF, citizen friendly airplane) investigates the potential of aircraft concepts for a possible future air transportation system integrating small airports. Key technologies in aerodynamics for developing new generation quiet, efficient, short take-off and landing (QESTOL) aircraft are studied through the synergistic exploitationof Computational Fluid Dynamics (CFD) and new wind tunnel data. One subject of the conducted investigations is a ninebladed high power propeller mounted in tractor configuration on a wing that is equipped with an active gapless high-lift system. As the aerodynamic focus of the BNF project is on the interaction between the propeller slipstream and the high-lift flowfield, this paper is focussed on the experimental investigation of the propeller performance in comparison with simulation data.

/pdf/experimental-investigation-of-the-propeller-design-for-1r6bvkk6wl.pdf

Experimental Investigation of the Propeller Design for future QESTOL Aircraft in the BNF Project

A semi-detailed kinetic mechanism with 100 species and 816 reactions for ethylene combustion including PAH formation was elaborated. The model includes the C2 H5 OH sub mechanism combustion as well. This mechanism has in view to be the base of further kinetic schemes of practical fuels (reference fuels). The mechanism was reduced to a skeletal model with 72 species and 580 reactions. The elaborated models were validated on experimental data bases of heat release as well as formation of polyaromatic hydrocarbons and soot in laminar premixed C2 H4 , C2 H4 / C2 H5 OH flames taken from literature. The calculated ignition delay times, laminar flame speeds, as well as temporal profiles of small and large aromatics and also soot particles are in good agreement with experimental data obtained for pressures 1 – 5 bar, temperatures T0 = 1100 – 2300 K, fuel/oxygen equivalence ratio φ = 0.5 – 2.Copyright © 2008 by German Aerospace Center

Carsten Lenfers

Papers

Propeller Design for a future QESTOL Aircraft in the BNF Project

Aerodynamic Effects of Propeller Slipstream on a Wing with Circulation Control

Propeller and Active High Lift Wing Interaction in Experiment and Simulation

Experimental Investigation of the Propeller Design for future QESTOL Aircraft in the BNF Project

Skeletal Mechanism for C2H4 Combustion With PAH Formation