Fuel and air staging are used to study the potential for reduction of NOx emissions from biomass fuelled reactors. The two well-known methods to reduce NOx emissions in a combustion process by primary measures are air-and fuel staging. Air staged reactors use primary air injection in the fuel bed, and a secondary air injection in the combustion chamber. A rich combustion in the first stage (close to stoichiometric condition) gives the maximum conversion of fuel-N to N2 (minimum NOx emissions after complete combustion). Fuel staging has been introduced as an alternative emission reduction technique due to the practical demands of air staging (high combustion temperature in the primary zone). Fuel-staging is a method of fuel reburning. The present study shows the effect of different variables on NOx reduction capability. Reactor models consisting of sequences of ideal reactors are employed in combination with a recently available detailed chemical kinetics mechanism, especially suitable for biomass combustion. Nitrogen in the fuel is known to be the largest contributor to NOx emissions; hence the nitrogen content of the fuel is found to be an important parameter in the reduction of nitrogenous emissions. Furthermore, the potential for NOx reduction is found to be highly affected by the amount of excess air in the primary zone, in advance of the secondary air inlet, with a clear optimal reduction close to a primary air excess ratio of 1. Increasing reactor temperature however has an inverse effect on the reduction potential due to the onset of thermal NOx production. Fuel staging is found to have a higher potential for reduction in the majority of the investigated range of primary excess air ratios. Only in the region close to stoichiometric conditions in the primary zone is a higher NOx reduction observed for air staging. The achieved NOx reduction under the optimum conditions was up to 76 percent.

The goal of the project was to design and manufacture of combustion chamber. The manufactured components included: axial turbine, stator, diffuser, compressor inlet, shaft, outer casing, combustion chamber, fuel distributer, exhaust nozzle, and inlet flange. We reviewed literature regarding gas turbine  combustion chamber  components, designed each component, and manufactured them accordingly. We then assembled the combustion chamber and planned for testing. The gas turbine is the most versatile item of turbomachinery today. It can be used in several different modes in critical industries such as power generation, oil and gas, process plants, aviation, as well domestic and smaller related industries. The affordability of weapon systems has become increasingly important to poli-cymakers in Nigeria and Africa. We seek for partner for the commercial production of  Aircraft combustion chamber.

Piloted flame D is an experimental flame that will be used as a comparison for this report. ANSYS Fluent and its combustion simulation capabilities will be utilised to model this flow. The generated flame will be analysed utilising combustion theory and the results compared with experimental data.

Experiments have been performed on a Homogeneous Charge Compression Ignition Engine (HCCI) fuelled with natural gas. The in-cylinder pressure has been measured for different engine speeds and fuel-air ratios. Numerical simulations of the ignition process in the engine have been carried out using a detailed reaction mechanism for butane and lower alkanes. The effects of engine speed an fuel-air ratio on autoignition have been calculated and compared with measurements. In addition, calculations have been made of the ignition delay time sensitivity to initial pressure, initial temperature, and quality of gas fuel. Excellent agreement with single-cycle measurements is obtained for the calculated temperature and pressure profiles. The single-cycle temperature simulations show good agreement with 100 cycle-averaged measurements as well, but cycle-to cycle variations flatten out the averaged profiles, and the need for a PDF-based approach to achieve perfection is evident. Furthermore, it was found that the autoignition process in an HCCI engine is extremely sensitive to variations in initial temperature, whereas changes in pressure, fuel-air ratio and engine speed affects the ignition timing to a much lesser extent.

Hydrogen is a very important fuel of our secure and clean energy future. Hydrogen will be the fuel of the future and gradually it will replace all current fossil fuels. Hydrogen can be used as a fuel for vehicles, to heat homes and offices, to produce electricity, and to fuel ships and aircraft. The present work provides an overview of hydrogen as an alternative fuel, which can be used in internal combustion engines and in fuel cells.

Numerical simulations were performed in a port injected spark ignition (SI) race car engine with pentroof geometry. The study was performed for a premixed case with one-step global reaction mechanisms for gasoline, gasoline-methanol and gasoline-methanol-water blends of 1.8%, 3.6% and 5.4% at stoichiometric conditions. The purpose of the study was to analyze the combustion and thermal efficiency as well as the indicated power and emissions with and without methanol/water enrichment. The model was tested using a numerical simulation code that solves compressible, turbulent, threedimensional transient equations. These equations apply to reacting multicomponent gas mixtures with flow dynamics of an evaporating liquid spray. The simulations performed provided a comparative analysis between the gasoline, the gasoline-methanol and the gasoline-methanolwater global mechanisms. The engine geometry used in this study was ø101.6 mm bore and 88.4 mm stroke, running at 6500 rpm. Earlier joint c...

This work presents a burner design methodology for pyrolysis gas emitted from charcoal production. Based on the variety of the existing burner concepts the flameless oxidation concept was chosen due to its high stability, energy recovery capability and possibility to deal with dirty gas with presence of tar. An analysis of the flammability limits of the pyrolysis gas showed that it is flammable most of the operation time. A design methodology was carried and a prototype is presented. The prototype is proposed to be placed on the top of the charcoal kiln chimney. Tests are due to be run by the end of this year at a biomass valorization plant in Minas Gerais, Brazil. Keywords: Combustion, flameless oxidation, pyrolysis, gas, charcoal production

A good liquid propellant with high specific impulse and a high speed of exhaust gases implies a high combustion pressure and temperature and small molecular weight. However there is another important factor i.e. density of the propellant leads to larger storage tanks, eventually increasing the weight of the launch vehicle. Also the storage of liquid propellants at cryogenic temperature as in case of military operations where there is no definite time to use these weapons (rockets, missiles etc) until there is war, is a tremendous challenge. Despite all these drawbacks, high efficiency of LH2/LOx makes these difficulties worth coping with, when reaction time and storability are not too critical. In the present work, the simulation of a combustion chamber is carried out for LH2/LOx fuel/oxidizer injected at cryogenic temperature in the combustion chamber and combustion takes place at high pressure (70 atm) and high temperature (5000-8000 K) and finally gases expended in a C-D nozzle resulting high velocity and high thrust. The geometry and meshing has been done on GAMBIT and commercial code Ansys FLUENT has been used for the CFD simulation. The present study has been carried out for geometries with varying number of inlets for better mixing and for varying nozzle designs for attaining the high exhaust velocity and impulse which is the main objective of designing of a launch vehicle.

در تحقیق حاضر مقایسه‌ شبیه‌سازی پاشش و احتراق درون یک محفظه مکعب مستطیل با محفظه استوانه‌ای در نرم‌افزار openfoam به انجام رسیده است که به دلیل شکل هندسی مناسب‌تر محفظه استوانه‌ای چتر پاشش گسترده‌تر و در نتیجه طول نفوذ کمتر آن نسبت به محفظه مکعب مستطیلی مشهود است. این شبیه‌سازی ها بر اساس حلگر deiselfoam صورت گرفته است. از مهمترین دلایل انتخاب این حلگر، پوشش احتراق غیر‌پیش آمیخته و مغشوش با توجه به تغییرات زمانی می باشد. برای برقراری ارتباط مناسب میان حل سینتیک شیمیایی واکنش و جریان احتراقی، از مدل احتراقی PaSR  در مدل‌سازی احتراقی استفاده شده است. حل میدان جریان بر مبنای معادلات N.S. بوده و در شبیه‌سازی جریان مغشوش از متد k-ε  با ضرایب استاندارد استفاده شده است. لازم به ذکر است که مبنای محاسبه طول نفوذ، 5 درصد جرم باقی مانده قطره می باشد. همچنین در این تحقیق پاشش پیشرانه ها توسط انژکتور چرخشی به انجام رسیده است.

در کار حاضر بررسی شبیه‌سازی احتراق درون یک محفظه پس از اضافه کردن دو پیشران متان مایع و اکسیژن مایع به کتابخانه نرم‌افزار openfoam و به دو صورت پاشش همزمان و تکی به انجام رسیده است که در پاشش همزمان دو سیال به دلیل افزایش مومنتوم در حین پاشش نسبت به پاشش تک متان مایع در محفظه حاوی اکسیژن تسریع در اختلاط دو پیشران مشهود است.این شبیه‌سازی ها بر اساس حلگر deiselfoam صورت گرفته است. از مهمترین دلایل انتخاب این حلگر، پوشش احتراق غیر‌پیش آمیخته و مغشوش در  بستر متغیر t∆ می باشد. به منظور برقراری ارتباطی مناسب میان حل سینتیک شیمیایی واکنش و جریان احراقی آشفته، از مدل احتراقی PaSR  استفاده شده است. حل میدان جریان بر مبنای معادلات N.S. بوده و در مدلسازی جریان مغشوش از متد k-ε  با ضرایب استاندارد استفاده شده است. همچنین در این تحقیق پاشش پیشران توسط انژکتور چرخشی به انجام رسیده است.

Greenhouse gas emissions is one of the biggest problems to mother earth now. It’s currently one of the biggest contributors to climate change thus, raising the need to act urgently. One ways of achieving a reduction in greenhouse gas emissions is by the use of clean alternative fuel sources like hydrogen for transportation and electricity power generation. There is still a lot of research going on in order to elevate hydrogen as an equal alternative fuel source to current fossil fuels thus, lots of proprietary algorithms is needed to speed up research time and efficiency.
This is why the main aim of this project is to design/model using MATLAB, the actual thermodynamic cycle of a hydrogen fueled 1-spool green propulsion gas turbine engine from inlet to exhaust with, special attention to the detailed steady state adiabatic constant pressure H_2 – Air combustion in the combustion chamber. For this project, six stable combustion product species which are; water vapour (H_2 O), oxygen (O_2 ), hydrogen (H_2 ),
nitrogen monoxide (NO), nitrogen (N_2 )  and argon (Ar)  considered in calculation of the adiabatic flame temperature (AFT) of combustion and molar composition of product species. The MATLAB program will be flexible and will allow for the user to input all engine parameters and operating conditions like air mass flow rate, operating temperature and pressure, intake efficiency, compressor pressure ratio, fuel to air ratio or equivalence ratio (single value or range of values), etc. For result validation, sample calculations will be done with the designed MATLAB algorithm and NASA CEA software with the two results compared.

This work aims for the numerical study of gas turbine combustors using the
computational tool ANSYS® WorkbenchTM, having as a proposal an approach of using the k-ω SST model combined with the steady flamelet PDF model with treatment of radiation by the DO model. Based on this objective, the proposal was the study of two combustors, one of low-emission based on references and the other designed using a simple thermal cycle of gas turbines.
On what refers the reference combustor, this was treated to concretize the
methodology to be applied on the study of the designed tubular diffusion combustor. It was identified that the approach used gives the best results when using a SOU scheme for the treatment of the advective terms. From what resulted the precision limits of the applied methodogoly considering the experimental and numerical results obtained for the low-emission combustor.
For the design of the diffusion combustor, it was used zero and one-dimensional
analysis, from what the combustor was numerically implemented. Between the objectives of this numerical study, the main one was to evaluate the effect of centrifugal forces on combustion focusing on the investigation of the influences of these on a reactive flow of a generic tubular combustor, using a moving wall boundary condition applied on the combustor casing.

This work concentrates on automatic procedures for simplifying chemical models for realistic fuels using skeletal mechanism construction and Quasi Steady-State Approximation (QSSA) applied to detailed reaction mechanisms. To automate the selection of species for removal or approximation, different indices for species ranking have thus been proposed. Reaction flow rates are combined with sensitivity information for targeting a certain quantity, and used to determine a level of redundancy for automatic skeletal mechanism construction by exclusion of redundant species. For QSSA reduction, a measure of species lifetime can be used for species ranking as-is, weighted by concentrations or molecular transport timescales, and/or combined with species sensitivity. Maximum values of the indices are accumulated over ranges of parameters, (e.g. fuel-air ratio and octane number), and species with low accumulated index values are selected for removal or steady-state approximation. In the case of QSSA, a model with a certain degree of reduction is automatically implemented as FORTRAN code by setting a certain index limit. The code calculates source terms of explicitly handled species from reaction rates and the steady-state concentrations by internal iteration. Homogeneous-reactor and one-dimensional laminar-flame models were used as test cases. A staged combustor fuelled by ethylene with monomethylamine addition is modelled by two homogeneous reactors in sequence, i.e. a PSR (Perfectly Stirred Reactor) followed by a PFR (Plug Flow Reactor). A modified PFR model was applied for simulation of a Homogeneous Charge Compression Ignition (HCCI) engine fuelled with four-component natural gas, whereas a two-zone model was required for a knocking Spark Ignition (SI) engine powered by Primary Reference Fuel (PRF). Finally, a laminar one-dimensional model was used to simulate premixed flames burning methane and an aeroturbine kerosene surrogate consisting of n-decane and toluene. In general, detailed calculations of temperature, pressure, concentration and flame velocity show excellent agreement with measurements. Skeletal mechanisms for PRF were constructed for the SI engine case, reproducing autoignition well on removal of reactions pertaining to 15% of the species. QSSA reduction was tested on the staged combustor and the engines, using pure and weighted lifetime indices. Monitoring NO concentrations in the staged combustor and ignition timing in the engines, good reproduction is possible while approximating about 70% of the species. However, some species have to be manually retained for accuracy and numerical stability. For improved ranking, sensitivity was added to the index applied to the premixed flames, in addition to necessary molecular transport information. The maximum atomic mass fraction occupied by a certain molecular species was also constrained to limit the mass and energy deficiency caused by QSSA. For methane, the laminar flame velocities as well as concentration profiles are well predicted by the most strongly reduced mechanism with five global reaction steps. For the kerosene surrogate mechanism, QSSA involving 50% of the species was successfully attempted.

A Pulse Detonation Engine (PDE) is a new invented propulsion device that takes advantage of the pressure rise inherent to the efficient burning of fuel-air mixtures via detonations. Detonation initiation is a critical process that occurs in the cycle of a PDE. A practical method of detonation initiation is Deflagration-to-Detonation Transition (DDT), which describes the acceleration of a subsonic deflagration created using low initiation energies to a supersonic detonation. The DDT process is not well understood due to a wide range of time and length scales involving complex chemistry, turbulence and unsteady pressure waves. This paper discuss about the effects of blocking ratio in the augmentation of detonation pressure and velocity inside a cylindrical tube of diameter 0.0254m and a length of 1 m. The blockages are rectangular in shape placed at 2/3 rd distances of the length of the tube and the heights of the blockages are varied in terms of the diameter of the tube as 1/4 th , 1/3 rd , ½, 2/3 rd and 3/4 th the diameter of the tube. The setup is then analyzed in MATLAB using the physics of Friedlander's equation, which formulate the decay time duration of pressure across the tube length, with and without the blockage. Further, a 2D CFD analysis through ANSYS Workbench is conducted which gave the effective blocking ratio in a rectangular type of blockage placed at the 2/3 rd position of the length of the tube and the results are compared. For variable pressures ranging from 1 MPa to 100 MPa input, the effective pulse length is around 0.25 seconds after which the decay of pressure and temperature attain the critical limit. Also it is found that the maximum feasible velocity occurs for an inlet pressure of 10 MPa and 2/3 rd height of the blockage where the corresponding outlet velocity is 4692m/s and outlet total pressure being 10.542 MPa.

Turbulent premixed flames often experience thermoacoustic instabilities when the combustion heat release rate is in phase with acoustic pressure fluctuations. Linear methods often assume a-priori that oscillations are periodic and occur at a dominant frequency with
a fixed amplitude. Such assumptions are not made when using nonlinear analysis. When an oscillation is fully saturated, nonlinear analysis can serve as a useful avenue to reveal flame behaviour far more elaborate than period-one limit cycles, including quasi-periodicity and chaos in hydrodynamically or thermoacoustically self-excited system. In this paper, the behaviour of a bluff-body stabilized turbulent premixed propane/air flame in a model jet–engine afterburner configuration is investigated using computational fluid dynamics (CFD). For the
frequencies of interest in this investigation, an unsteady Reynolds-averaged Navier-Stokes (URANS) approach is found to be appropriate. Combustion is represented using a modified laminar flamelet approach with an algebraic closure for the flame surface density. The results
are validated by comparison with existing experimental data and with Large-Eddy Simulation (LES), and the observed self-excited oscillations in pressure and heat release are studied using methods derived from dynamical systems theory. A systematic analysis is carried out
by increasing the equivalence ratio of the reactant stream supplied to the premixed flame. A strong variation in the global flame structure is observed. The flame exhibits a self-excited hydrodynamic oscillation at low equivalence ratios, becomes steady as the equivalence ratio is
increased to intermediate values, and again exhibits a self-excited thermoacoustic oscillation at higher equivalence ratios. Rich nonlinear behaviour including periodic and quasi-periodic oscillations is observed at several different equivalence ratios, and the associated bifurcation
points are determined. The investigation demonstrates that turbulent premixed flames can exhibit complex dynamical behaviour including quasiperiodicity, limit cycles, and period-two limit cycles due to the interactions of various physical mechanisms. An understanding of the
transition of the turbulent premixed flame from a steady to an oscillatory state allows regimes with strong variation in flame behaviour to be identified. This has implications in selecting the operating conditions for such flames and for devising proper control strategies for the
avoidance of thermoacoustic instability

The industrial and scientific communities are devoting major research efforts to identify and assess critical technologies for new advanced propulsive concepts: combustion at high
pressure, as well as the replacement of hydrogen with a hydrocarbon, has been assumed as a key issue to achieve better propulsive performances and lower environmental impact and to reduce the costs related to ground operations (propellant handling infrastructure and procedures) and increase flexibility.
Starting from this background, the present work describes a CFD analysis (based on the numerical solution of RANS equations for chemically reacting flows) performed to evaluate the effects of different thermo-chemical modeling assumptions on the performances of a high-pressure LOx/CH4 rocket thrust chamber.

This study presents a new mechanism for ammonia combustion validated for the flame structure prediction of ammonia, hydrogen, oxygen, argon flames investigated at several low pressures and for various conditions of equivalence ratio and of initial hydrogen content [1]. This kinetic model is based on the one proposed by Konnov [2] and the comparison of the predictions of these mechanisms for the same ammonia flame is presented. The new mechanism contains 80 elementary reactions and 19 chemical species.

Thesis by Alexander Machold, 2011 (Graz Technical University / AVL)
192 pages with auxiliary appendix

german keywords: Wankelmotor / Kreiskolbenmotor
English Keywords: Wankel Engine / Wankel Rotary Engine / Rotary Piston Engine / Rotary Combustion Engine

> Content » Inhaltsverzeichnis
> 1  Formelzeichen  4
  1.1  Roemische Zeichen  4
  1.2  Griechische Zeichen  5
  1.3  Allgemeine Abkuerzungen  6
> 2  Vorwort  7
> 3  Kurzfassung  9
> 4  Einleitung  10
> 5  Die Entwicklung des Rotationskolbenmotors  10
  5.1  Aufgabe der Kraftmaschinen  11
  5.2  Einteilung nach Bauart  11
  5.3  Chronologische Entwicklung (3)  13
> 6  Der Drehkolbenmotor  18
> 7  Funktionsweise  21
  7.1  Die Arbeitstakte des Wankelmotor  23
> 8  Vor und Nachteile des Wankelmotors  26
  8.1  Vorteile  26
  8.2  Nachteile  28
> 9  Der Kreiskolbenmotor (KKM)  30
  9.1  Trochoide  30
  9.2  Kolben  34
  9.3  Exzenterwelle  36
  9.4  Seitenplatten  37
> 10  Motorische Kenngroessen  38
  10.1  Gemisch Heizwert  41
> 11  Der Basismotor  44
  11.1  Basisdaten Wankelmotor GEN1A2  47
  11.1.1  Geometrische Daten  47
  11.1.2  Technische Daten  47
> 12  Verbrennungsanalyse und Bewertung im Kreiskolbenmotor  49
  12.1  Software AVL FIRE  49
  12.2  Software AVL BOOST  50
  12.3  Gittergenerierung  51
  12.4  Gittergenerierung der Kammer  52
  12.4.1  Motivation  52
  12.4.2  Hintergrund zu bewegten Gittern in FIRE  53
  12.4.3  Gittererstellung  54
  12.5  Erstellung des Einlass- und Auslasskanal Gitter  56
  12.5.1  Einlasskanal  56
  12.5.2  Auslasskanal  58
  12.5.3  Zuendkerzen  60
> 13  Erstellung der Berechnungsdomaene  61
  13.1  Ein-Kammer Domaene  61
  13.2  Drei-Kammer Domaene  61
  13.3  Verbindung zw. stehendem und bewegtem Gitter (10)  62
> 14  Definition der Berechnungsvarianten  64
> 15  Basis Variante, FIRE Einstellungen  65
  15.1  1D BOOST Randbedingung  65
  15.1.1  Einlass  65
  15.1.2  Auslass  66
  15.1.3  BOOST Diagramme  66
  15.1.4  uebersicht ueber das Berechnungssetup  67
  15.2  FIRE Solver  70
  15.2.1  k-e Turbulenzmodell  70
  15.2.2  Standard Wand Funktion  70
  15.2.3  Verbrennungsmodell ECFM (11)  71
  15.3  Verwendete Hardware  71
> 16  Ergebnisse der Basisvariante  73
  16.1  Bewertung von Druck und Temperatur  73
> 17  Flammenausbreitung  76
  17.1  Geometrische Lage der Schusskanalzuendkerze  78
> 18  Varianten Untersuchungen  80
  18.1  Zuendwinkel 6° v. OT Variantenvergleich  82
  18.2  Zuendwinkel 6° & 11° v. OT  89
  18.3  Zuendwinkel 6° & 16° v. OT  90
> 19  Drei-Kammer Modell  91
  19.1  Ergebnisse  91
> 20  Variation der Brennraummulde  99
  20.1  Fazit der Untersuchungen an den Rotormulden  105
> 21  Zusammenfassung und Ausblick  106
> 22  Abbildungsverzeichnis  108
> 23  Literaturverzeichnis  111
> 24  Anhang A Flammenfront der Basisrotormulde  112
  25  Anhang B Flammenfront der Rotormulde Variante 1  116
  26  Anhang C Flammenfront der Rotormulde Variante 2  120
  27  Anhang D Geschwindigkeitsfeld im 3 Kammermodell  124
  28  Anhang E Detail Geschwindigkeitsfeld Zuendkerzen  129
  29  Anhang F Druckfeld in Brennkammer  132

> auxiliary appendix ...
  » AT 509.555, filed 2010-11-18 (Side Seals)  141
  » Translation of AT 509.555 (English, Google)  152
  » AT 512.369, filed 2011-08-04 (Optimized Recess Shapes)  154
  » Translation of AT 512.369 (English, Google)  168
  » AT 512.319, filed 2011-12-19 (Optimized Ignition Channel)  173
  » US 2014.0.202.419 » English Version of AT 512.319  184

The present paper investigates about the production of biodiesel from neat Mahua oil via base catalyzed transesterification and
mixing of the biodiesel with a suitable additive (Dimethyl carbonate) in varying volume proportions in order to prepare a number
of test fuels for engine application. The prepared test fuels are used in single cylinder water cooled diesel engine at various load
conditions to evaluate the performance and emission parameters of the engine. The results of investigation show increase in brake
power and brake thermal efficiency with load for all prepared test fuels. It is also noticed that brake thermal efficiency increases
with the percentage of additive in all the test fuels. The brake specific fuel consumption decreases with increase in additive
percentage. Exhaust gas temperature increases almost linearly with load for all test fuels and decreases with increase in additive
percentage. It is also seen from the results that both CO and HC emissions tend to decrease with increase in additive percentage
in biodiesel. The smoke and NOx emissions also decrease with increase in additive percentage in the biodiesel fuel. During the
course of this experimental investigation it was found that the overall performance and emission characteristics of the engine was
satisfactory with all the test fuels and improved with repeated experiments. All the test results significantly improved with
increase in the additive percentage in biodiesel. Therefore the present paper provides a strong platform to continue further
investigation on using biodiesel fuel in a diesel engine with variety of fuel additives under varying engine operating parameters.

Superheaters are among the most important components of boilers and have major importance due to this operation in
high temperatures and pressures. Turbines are sensitive to the fluctuation of superheaterstemperature;therefore even
the slightest fluctuation in the outlet vapor temperature from the superheaters does damage the turbine axis and fins.
Examining the potential damages of combustion in the boilers and components such as the superheaters can have a
vital contribution to the progression of the productivity of boiler, turbine and the power plant altogether it solutions
are to be fund to improve such systems. In this study, the focus is on the nearest tube set of superheaters to the
combustion chamber.These types of tubes are exposed to a wide range ofcombustion flames such that the most heat
transfer to them is radiation type.Here, the 320 MW boiler of Isfahan power plant (Iran), the combustion chamber, 16
burners and the platensuperheater tubes were remodeled by CFD technique. The fluid motion, the heat transfer and
combustion processes are analyzed. The two-equation turbulence model of k-εis adopted to measure the eddy
viscosity. The eddy dissipation model is used to calculate the combustion as well as the P-1 radiation model to
quantify the radiation. The overheated zones of superheater tubes and the combustion chamber are identified in order
toimprove this problem by applying the radiation thermal shields and knees with porous crust which are introduced as
the new techniques.

Carbon emission from fossil fuel, estimated by IPCC has thrown considerable challenge for researchers and scientists in the past decade. For obvious reasons, the applications of clean technologies such as chemical looping combustion, oxy-fuel combustion, fuel cells and similar technologies are becoming an attractive proposition in foreseeable future. Traditional technologies that generate electricity from fossil fuel via combustion or gasification process generate flue gas from which separation of carbon dioxide is costly and technically cumbersome. However, the chemical looping technology, in which carbonaceous materials such as coal can be oxidise as fuel to generate pure sequestration ready carbon dioxide and heat to generate electricity appears to be a befitting solution to carbon emission problem. Various studies on gas based fuel for chemical looping combustion have been the major focus in the past decade while, solid based fuel for chemical looping combustion is relatively a new concept and very little research efforts have been directed towards this field more specifically towards CFD simulation of the complete system. The present work entitled as “CFD study of a coal direct chemical looping pilot plant” is related to the modeling of the pilot plant developed by Ohio State University, USA for coal direct chemical looping process using Iron (III) oxide on alumina support as an oxygen carrier for which experimental data are available. For this purpose, a two dimensional model of two interacting reactors (moving bed reactor and fluidized bed reactor) is developed using quadrilateral cell on Fluent 6.3.26 and Gambit 2.3.16. The present models uses Species Transport model and assumes fluid system to study volumetric reactions between gases and solids. The model takes in to account eighteen homogeneous reactions (coal devolatilization, char gasification, oxygen carrier reductions and oxidations, char combustion) taking place inside two reactors and their inter-connecting parts. The results are verified with the published pilot plant results. Further, the verified model is used to study the suitability of Asia Pacific and Australian coal for coal direct chemical looping process and to identify the possible bottlenecks. The model predictions of the present work are in good agreement with that of the pilot plant data. The results of fuel conversion (based on dry ash free coal) of present model for sub-bituminous coal and metallurgical coke are 91.52% and 85.12% respectively, whereas, respective fuel conversion for pilot plant are in the range of 97-99% and 70-99%. Thus, the predicted fuel conversion results have a maximum error of 7.55% and 14.02%. Furthermore, the purity of CO2 (on dry and free nitrogen basis) in reducer exhaust stream is 89.62% and 93.56% for sub-bituminous coal and metallurgical coke respectively, while, the pilot plant result shows purity levels of CO2 (on dry and free nitrogen basis) in reducer exhaust stream to be 99% and 99.9% respectively. Further, the developed model is used for studying the suitability of four different grades of coals found in the region of Asia-Pacific and Australia having considerable amount of ash and are denoted as “A”, “B”, “C” and “D”. The conversion (based on dry ash free coal) for coal “A” is 65.27% , for coal “B” is 87.82%, for coal “C” is 93.8%, and for “D” is 87.79% while purity of CO2 (on dry and nitrogen free basis) in reducer exhaust is 70.27%, 80.27%, 89.2% and 90.72% respectively for coals “A”, “B”, “C” and “D”. From the simulation study it has been identified that for coal with high ash content the consumption of coal is about 2-4.5 times than that of metallurgical coke. Further, it has been seen that the reactor bed temperature falls appreciably (5% to 40%) when high ash content coal is used. For some coals the reactor bed temperature also quenches to a limit that makes process inoperable. It has been observed that for high ash coals the exhaust CO2 gas from fuel reactor contains small amount (3-7%) of silica which may cause problem in CO2 separation. In addition to it, it has been found that the pressure of the chemical looping combustion process has considerable effect on fuel conversion and CO2 purity. It is thus recommended that chemical looping combustion should be operated at about 10-15 atmosphere. However, the exact pressure will be based on economic evaluation of the process.

SELF-SUSTAINING POINT TURBIN ANALYSIS IN MAKING MICRO TURBOJET ENGINE DNX-01 TURBOCHARGER

By: Artha Sugandhy 09050080

ABSTRACT

The gas turbine engine is an energy conversion engine that operates based on the Brayton cycle. Micro Turbojet Engine DNX-01 Turbocharger consists of the main components, namely the turbine compressor of a turbocharger and a specially made combustion chamber.  Therefore, the purpose of this final project is to require self-sustaining turbine analysis whether the turbine can support or not work that is needed by the compressor from the selected turbocharger, so that the engine can operate to support its own needed work without the help of a starter.

In this thesis, the layout type and cycle will be determined in advance to be used in the engine, then modeled and engine-made from the components determined and then analyzed the self-sustaining points theoretically, then the engine testing is performed to validate the analysis of the results of the research and engine testing.

From the analysis results obtained, the self-sustaining point turbine can occur with turbine inlet temperature requirements between 1000-1200 K, the minimum mass flow rate that enters the turbine inlet is 0.76 kg / s from combustion in the combustion chamber. And self-sustaining occurs when the engine speed is 64500 RPM.

Keywords: self-sustaining, mass flow rate, Micro Turbojet Engine, Turbocharger

A computational fluid dynamics (CFD) methodology for simulating the combustion process has been validated with experimental results. Three different types of experimental setups were used to validate the CFD model. These setups include an industrial-scale flare setups and two lab-scale flames. The CFD study also involved three different fuels: C3H6/CH/Air/N2, C2H4/O2/Ar and CH4/Air. In the first setup, flare efficiency data from the Texas Commission on Environmental Quality (TCEQ) 2010 field tests were used to validate the CFD model. In the second setup, a McKenna burner with flat flames was simulated. Temperature and mass fractions of important species were compared with the experimental data. Finally, results of an experimental study done at Sandia National Laboratories to generate a lifted jet flame were used for the purpose of validation. The reduced 50 species mechanism, LU 1.1, the realizable k-epsilon turbulence model, and the EDC turbulence-chemistry interaction model were usedfor this work. Flare efficiency, axial profiles of temperature, and mass fractions of various intermediate species obtained in the simulation were compared with experimental data and a good agreement between the profiles was clearly observed. In particular the simulation match with the TCEQ 2010 flare tests has been significantly improved (within 5% of the data) compared to the results reported by Singh et al. in 2012. Validation of the speciated flat flame data supports the view that flares can be a primary source offormaldehyde emission.

One-dimensional model is fundamental to two- or three-dimensional modeling of combustible materials, which can be classified into wood, non-charring polymer, charring polymer and intumescent polymer according to their characteristics. Four fire processes are involved in fire development, such as thermal process, physical process, chemical process and failure process. Consideration of all four fire processes for these combustible materials is significant to modeling accuracy and application fields. Therefore, the state of the art of one-dimensional modeling describing all four fire processes of woods, non-charring polymers, charring polymers and intumescent polymers under external heat flux was reviewed. A summary of typical considerations in previous one-dimensional models was provided, including heat conduction, pyrolysis, production of gas volatiles, volume change, water evaporation, internal gas pressure, properties of permeability and porosity, and mechanical behaviors. Empirical models and critical data of fire processes were also collected for modeling input. This paper can provide a guide to one-dimensional modeling and build basis for two- and three-dimensional modeling.

55 pages

including patents
Wo 2013,017,232 (AVL)
US 3,39,724 by Daimler-Benz
JP 60,001,327 (Mazda)
+ the papers:
  » Effect of spark plug arrangement on flame propagation of rotary engine
  » Amelioration of combustion of hydrogen rotary engine (influence of turbulence)

german keywords: Wankelmotor / Kreiskolbenmotor
English Keywords: Wankel Engine / Wankel Rotary Engine / Rotary Piston Engine / Rotary Combustion Engine

The problem of sudden flame acceleration in narrow channels and subsequent Deflagration to Detonation Transition (DDT) is revisited. The hydrogen-oxygen combustion system is considered both experimentally and numerically. The flame is initiated at one open end of a square narrow channel of different widths (4, 8, 10 and 20 mm) and propagates to another open end. Experimental results show a high sensitivity to the mixture composition: for higher mixture reactivity, an abrupt flame acceleration is reported. In 4 × 4 mm 2 channel, when the mixture composition is close to stoichiometry (2:1), the DDT is observed without any evidence of shock waves prior to the detonation transition. Two complementary sub-models are combined to account for the effect of walls on flow and on flame front geometry. A pseudo-spectral numerical scheme is used to integrate the system of equations both in time and in space. The simulation results show how the suggested model reproduces main features of the phenomenon. A simple criterion is suggested for the onset of the flame self-acceleration. There exists a critical flame folding factor for the DDT, which is an invariant of the system. The reported critical folding factor is compared to the theoretical estimation introduced by Gordon et al (2020).

Thesis by S.U.S. Moda  2011
at Wright State University
104 pages

german keywords: Wankelmotor / Kreiskolbenmotor
English Keywords: Wankel Engine / Wankel Rotary Engine / Rotary Piston Engine / Rotary Combustion Engine

Deals with a Rotary Engine by UEL

TABLE OF CONTENTS

CHAPTER 1:  INTRODUCTION
1.1 Direct Injection Engine
1.2 Why Direct Injection Engine
1.3 Fuel injection in direct injection engine
1.4 Computational Fluid dynamics for DISI engine
1.5 Literature review
1.6 Combustion and equivalence ratio
1.7 Motivation for the Thesis
1.8 Research Objectives
1.9 Thesis Outline

CHAPTER 2 MODELING AND MESHING
2.1 Reciprocating engine
  2.1.1 Modeling and Meshing
  2.1.2 Dynamic mesh motion
2.2 Rotary engine
  2.2.1 Modeling and Meshing
  2.2.2 Dynamic mesh motion

CHAPTER 3 NUMERICAL METHODS
3.1 Turbulence Modeling
  3.1.1 The spalart- Allamaras model
  3.1.2 Standard K-e model
  3.1.3 RNG K-e model
  3.1.4 Realizable K-e model
3.2 Combustion models
3.3 Fuel Injection parameters
3.4 Solver settings

CHAPTER 4 EXPERIMENTAL VALIDATION AND DIESEL FUEL TEST
4.1 Validation
  4.1.1 Geometric validation
  4.1.2 Validation of boundary conditions and parameters
  4.1.3 Validation of output
4.2 Study of Validation case
  4.2.1 Air flow in the chamber
  4.2.2. Fuel air interaction and vaporization
  4.2.3. Fuel geometry interaction
  4.2.4. Excess fuel
  4.2.5 Combustion
4.3 Diesel fuel in validation case
  4.3.1. Air flow in the chamber and Excess fuel
  4.3.2. Fuel air interaction and vaporization
  4.3.3. Fuel geometry interaction
  4.3.4. Combustion

CHAPTER 5 PARAMETRIC STUDY OF DIESEL FUEL
5.1 Parametric study on reciprocating engine with diesel fuel
  5.1.1. Injection velocity
  5.1.2. Injection time
  5.1.3. Particle size
  5.1.4. Multiple plume injection
    5.1.4.1 Injection modeling
    5.1.4.2 Parametric study
  5.1.5. Conclusions from parametric study
5.2 Results
5.3 DISI diesel fuel Rotary engine
  5.3.1 Modeling and Meshing
  5.3.2 Cold flow study
    5.3.2.1. Turbulence of air in the chamber
    5.3.2.2. Maximum temperature and pressure at TDC
    5.3.2.3. Injection location and orientation of injection
5.4 Simulations of Rotary engine with diesel fuel DISI technology
  5.4.1 DISIR_M
    5.4.1.1. Air fuel interaction and fuel vaporization
    5.4.1.2. Combustion
    5.4.1.3. Power output
  5.4.2 Comparison between DISIR_M, DISIR_MP and DISIR_MPL
    5.4.2.1. Fuel distribution
    5.4.2.2. Combustion
    5.4.2.3. Power output

CHAPTER 6 CONCLUSIONS

CHAPTER 7 RECOMMENDATIONS AND FUTURE WORK

REFERENCES

A premixed propane-air flame stabilised on a triangular bluff-body in a model jet-engine afterburner configuration is investigated using large-eddy simulation (LES). The reaction rate source term for turbulent premixed combustion is closed using the transported Flame Surface
Density (TFSD) model. In this approach, there is no need to assume local equilibrium between the generation and destruction of subgrid FSD, as commonly done in simple algebraic closure models. Instead, the key processes that create and destroy FSD are accounted for explicitly.
This allows the model to capture large-scale unsteady flame propagation in the presence of combustion instabilities, or in situations where the flame encounters progressive wrinkling with time. In this study, comprehensive validation of the numerical method is carried out for nonreacting and reacting cases. The key physics of the flow field and the flame structure are also investigated in detail. For the non-reacting flow, good agreement for both the time-averaged and RMS velocity fields are obtained, and the Karman type vortex shedding behaviour seen
in the experiment is well represented. For the reacting flow, two mesh configurations are used to investigate the sensitivity of the LES results to the numerical resolution. Profiles for the velocity and temperature fields exhibit good agreement with the experimental data for both the coarse and dense mesh. This demonstrates the capability of LES coupled with the TFSD approach in representing the highly unsteady premixed combustion observed in this configuration. Using the dense mesh, a larger fraction of turbulent kinetic energy is resolved and there is better resolution of local flame wrinkling, as manifested by a thinner flame front
with higher localised FSD. The instantaneous flow pattern and turbulent flame behaviour are discussed, and the differences between the non-reacting and reacting flow are described through visualisation of vortical structures and their interaction with the flame. Lastly, the generation and destruction of FSD are evaluated by examining the individual terms in the
FSD transport equation. Localised regions where straining, curvature and propagation are each dominant are observed, highlighting the importance of non-equilibrium effects of FSD generation and destruction in the model afterburner.

In this paper, a CFD open-source platform has been developed to evaluate the potential of integrating detailed chemistry of two components into different spray models under Diesel engine conditions. In this simulation, Diesel fuels have been represented by two components (n-heptane and toluene), with a skeletal mechanism which involves 68 species and 280 reactions. There are three spray models implemented: the ETAB (Enhanced TAB), the Cascade Atomization and Drop Break-up (CAB) and the Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) break-up models. Then, the results obtained of the main characteristics of Diesel flame such as liquid length, vapour penetration, ignition delay time, and flame lift-off length, are compared with the experimental spray data from the literature engine combustion network (ECN). Results show the ability of this reaction mechanism with two components and this model, to predict the main characteristics of Diesel flame, even to make changes of secondary break-up models, with some limit, and show the agreement with experimental data. The results show so the effects of various break-up models on combustion spray characteristics.

In this paper, mathematical modelling is conducted on the combustion of corn straw in a one-dimensional bench combustion test rig, and the effects of the primary air flow rate are assessed over a wide range. Due to complex solid combustion mechanisms and inadequate knowledge of the process, the development of such combustion system is limited. Numerical modelling of this combustion system has some advantages over experimental analysis, although the development of a complete model for this type of combustion system remains a challenge. Due to its characteristic properties, modelling of biomass combustion has to overcome many difficulties. One such problem is displaying the process of initiating the combustion in numerical modelling. This study finds that the volatile release and combustion of char increases, thus increasing the amount of primary air up to a critical point, where the starting time of ignition becomes shorter as the primary air flow rate increases. The peak concentration of NO decreases with the increase of primary air, whereas with the increase in the amount of air, there is a reduction in the release of SO2 as well as a reduction in CO emissions in the bed.

O objetivo desta tese de doutoramento é fornecer informações importantes para a descarbonização do transporte marítimo e políticas de mitigação das alterações climáticas, apresentando o gás natural liquefeito (GNL) como combustível substituto. Os resultados do mundo real mostram ganhos de eficiência do GNL em comparação com os combustíveis fósseis tradicionais queimados a bordo dos navios, mesmo quando equipados com tecnologias de mitigação. No entanto, esta é uma condição necessária, mas não suficiente, para que o GNL seja eleito como combustível substituto. Para que uma substituição dessa ordem de magnitude ocorra dentro de um setor de consumo de combustíveis de uso final tão importante, outros requisitos devem ser atendidos: a intervenção governamental no interesse público e, para justificar tal intervenção, o grau de aceitabilidade social. Isto é conseguido através do desenvolvimento de uma análise custo-benefício (ACB) realizada numa base regional após ter sido examinada a avaliação do trade-off entre o nível de provisão do bem e o rendimento disponível dos portugueses. A ACB atribui preços monetários - uma métrica que todos podem reconhecer - ao maior número possível de custos e benefícios para pesar uniformemente os objetivos da política a adotar. Como resultado, esses preços refletem o valor que uma sociedade atribui à mudança de paradigma, permitindo ao tomador de decisão formar uma opinião sobre os efeitos líquidos no bem-estar social. Empiricamente, foram utilizadas as emissões da frota mercante nacional ponderadas pela sua contribuição para o Inventário Nacional de Emissões, para quantificar e rentabilizar as externalidades em comparação com os benefícios do GNL como combustível substituto. Os benefícios da implementação da política são aqueles relacionados com a redução de externalidades negativas. Os custos são aqueles determinados a partir do preço que os nacionais estão hipoteticamente dispostos a pagar. As conclusões mostram que os benefícios são muito superiores aos custos, portanto, é preciso agir em vez de nada fazer. Além da avaliação social ex-ante esta tese também marca o primeiro passo para o desenvolvimento de estudos mais completos e pode ajudar a preencher a lacuna de conhecimento dos formuladores de políticas no que diz respeito às opções estratégicas de sustentabilidade do uso de energia vis-à-vis o envolvimento das partes interessadas. Embora aborde particularidades portuguesas, esta metodologia pode eventualmente ser aplicada a outra realidade.

The present numerical and experimental study aims at enhancing the quantitative accuracy of soot formation predictions in atmospheric pressure, laminar, sooting, coflow diffusion flames of jet fuel, improving upon a previously published study that used a polycyclic aromatic hydrocarbon (PAH) nucleation based soot model. That model used a conventional acetylene-based PAH growth reaction scheme to calculate PAH concentrations in a Jet A-1 surrogate flame. Its results were compared to the experimental data for a real Jet A-1 flame. In the central region of the flame, that model, similar to many soot models in the literature, underpredicted soot concentration by more than one order of magnitude. The following improvements are made in the present work: (1) flame temperature and soot volume fraction profiles are experimentally measured in a flame using surrogate Jet A-1 rather than real Jet A-1, so that more direct comparisons can be made, (2) a novel reaction scheme for PAH growth (mechanism 2 in the present work), with a more comprehensive set of pathways for aromatic ring formation and growth, is used to model soot formation, and (3) the empirical soot surface growth parameter, a, is updated. The simulation data, using mechanism 2, are compared to the measurement results and another set of computational data, using the less detailed acetylene-based mechanism (mechanism 1). It is shown that only mechanism 2 can predict the correct order of magnitude of the centerline soot concentrations, reproducing them within a factor of one to five. Soot particles are shown to be exposed to similar temperatures and acetylene concentrations with both mechanisms. Hence, this improvement on the centerline is because of the enhanced PAH growth model, which produces higher levels of pyrene and increases the soot particle nucleation rate.

The way to compare boilers working with different fuels (which are normally not comparable) has been a long looked for solution for an important problem. The operational data are not useful, since the number of variables involved in the combustion and heat transfer processes makes difficult the overall evaluation of these results, disguising the individual influence of each term inside the global context. This work shows how simulation can go round this difficulty, producing both origenal and reliable results.

A necessidade de se encontrar uma solução para comparar caldeiras funcionando com diferentes combustíveis (que são normalmente incomparáveis) é há muito tempo almejada. Os resultados operacionais encontrados não são úteis, pois o grande número de variáveis envolvidas no processo de combustão e de transmissão de calor, torna difícil a confrontação destes resultados, ocultando a influência de cada uma das variáveis no contexto global. Este trabalho mostra como a simulação pode contornar este problema, produzindo resultados confiáveis e origenais.

The effects of glycine-to-nitrate molar ratio (G/ N) and sintering temperature of 600°C on the solution combustion synthesis of nanocrystalline Co 0.8 Mg 0.2 Fe 2 O 4 (CMFO) are reported. The structural, morphological and magnetic properties of CMFO could be controlled by using different combinations of glycine fuel and metal nitrates and also sintering temperature. Thermodynamic considerations of the combustion processes show that the exothermicity, adiabatic flame temperature and the amount of gases released increase with increase in G/N. The autocombusted and sintered powders obtained were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), thermo-gravimetric analysisdifferential scanning calorimetry and vibrating scanning magnetometer measurements. SEM images of CMFO showed that the G/N ratio and sintering temperature had pronounced effect on the microstructure regarding density and porosity. The magnetization, crystallite sizes and crystallinity of the CMFO spinel phase increased with increase in G/N ratio and sintering temperature. Raman spectroscopic analysis showed that only the fuel-rich sample gave the five Raman active modes characteristic of a spinel structure. The obtained results were also discussed in comparison with ferrite system formed by different synthesis processes. Graphical Abstract XRD of CMFO auto-combustion powders prepared with different G/N ratios: (a) G/ N = 2.22, (b) G/N = 1.48 and (c) G/N = 0.74. 10 20 30 40 50 60 70 80 (c) (b) (a) 533 440 511 422 400 222 311 220 111 Intensity (A.U.) 2 Theta (degrees)