Modeling of Chemical Processes in a Diesel Engine With Alcohol Fuels

2007 ◽  
Vol 129 (4) ◽  
pp. 355-359 ◽  
Author(s):  
Nadir Yilmaz ◽  
A. Burl Donaldson
Keyword(s):  
Large Scale ◽  
Reaction Rates ◽  
Field Trials ◽  
Engine Oil ◽  
Cylinder Pressure ◽  
Reactor Model ◽  
Compression Ignition Engine ◽  
Chemical Reaction Kinetics ◽  
Stirred Reactor ◽  
Partially Stirred Reactor

Methanol utilization in a compression ignition engine has held tentative promise for a number of years, and, in fact, the concept has seen large scale field trials intended to demonstrate this option as a precursor to commercial implementation. However, results from those tests have identified some of the practical problems encountered with this fuel, namely, (1) its difficulty of vaporization and (2) its high autoignition temperature. Luminosity promoting additives, which facilitate radiative transport as a component of flame spread (because pure alcohol burns with little luminosity, continuum radiation as a reaction transport mechanism is essentially absent), intake air heating, active and passive heat sources, etc., represent some of the attempts to overcome limitations of these two factors. Except for intake air preheat, these augmentation methods have been noted to result in poor off-load thermal cycle efficiency. Focusing on the case of intake air preheat (which can be achieved by elevated compression ratio), and to model the chemical reaction kinetics, the partially stirred reactor model in CHEMKIN was used. This approach provided examination of the chemistry and reaction rates associated with an actual trial in which methanol was the fuel under study. To initiate this simulation, literature available reaction mechanisms were obtained, and then the experimental cylinder pressure history was matched by control of heat release rate via the partially stirred reactor model. This is represented within the reactor model by changing the turbulent mixing intensity factor. The overall reaction sequence, which models cylinder pressure, and attendant extent of reaction were the major focus. The minor focus included production of emission gases, e.g., the aldehydes and unburned fuel. Not only are the model results consistent with actual findings, they also support a method for addressing causes of off-load inefficiency and engine failures due to engine oil dilution with fuel.

scholarly journals Numerical simulation of a backward-facing step combustor using reynolds-averaged navier–stokes / extended partially stirred reactor model

2019 ◽  
Author(s):  
N. Petrova ◽  
V. Sabelnikov ◽  
N. Bertier
Keyword(s):  
Chemical Mechanism ◽  
Navier Stokes ◽  
Backward Facing Step ◽  
Reactor Model ◽  
Experimental Database ◽  
Eddy Simulation ◽  
Stirred Reactor ◽  
Tabulated Chemistry ◽  
Reynolds Averaged Navier Stokes ◽  
Partially Stirred Reactor

The authors adapt recently developed a large eddy simulation / extended partially stirred reactor (LES/EPaSR) model by Sabelnikov and Fureby for simulation of turbulent combustion to Reynolds-averaged Navier–Stokes (RANS) equations. The proposed RANS/EPaSR model is validated against experimental database created at ONERA for an air–methane premixed flame stabilized by a backward-facing step combustor. The RANS/EPaSR model is compared also with the following RANSbased combustion models: (i) quasi-laminar model with reduced chemical mechanism (QL RCM); (ii) premixed flamelet tabulated chemistry (PFTC) without taking into account the turbulence–chemistry interaction (TCI); and (iii) a PFTC with a presumed β probability density function (PDF) for a progress combustion variable.

A Comparative Study of Flamelet and Finite Rate Chemistry LES for a Swirl Stabilized Flame

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
C. Fureby
Keyword(s):  
Large Scale ◽  
Small Scale ◽  
Reactor Model ◽  
Finite Rate ◽  
Eddy Simulation ◽  
Transient Nature ◽  
No Formation ◽  
Stirred Reactor ◽  
Large Eddy ◽  
Large Scale Flow

Present-day demands on combustion equipment are increasing the need for improved understanding and prediction of turbulent combustion. Large eddy simulation (LES), in which the large-scale flow is resolved on the grid, leaving only the small-scale flow to be modeled, provides a natural framework for combustion simulations as the transient nature of the flow is resolved. In most situations; however, the flame is thinner than the LES grid, and subgrid modeling is required to handle the turbulence-chemistry interaction. Here we examine the predictive capabilities between LES flamelet models, such as the flamelet progress variable (LES-FPV) model, and LES finite rate chemistry models, such as the thickened flame model (LES-TFM), the eddy dissipation concept (LES-EDC) model, and the partially stirred reactor model (LES-PaSR). The different models are here used to examine a swirl-stabilized premixed flame in a laboratory gas turbine combustor, featuring the triple annular research swirler (TARS), for which high-quality experimental data is available. The comparisons include velocity and temperature profiles as well as combustor dynamics and NO formation.

scholarly journals Effect of Injection Timing and Injection Duration of Manifold Injected Fuels in Reactivity Controlled Compression Ignition Engine Operated with Renewable Fuels

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4621
Author(s):  
P. A. Harari ◽  
N. R. Banapurmath ◽  
V. S. Yaliwal ◽  
T. M. Yunus Khan ◽  
Irfan Anjum Badruddin ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Injection Timing ◽  
Compression Ignition ◽  
Cylinder Pressure ◽  
Compression Ignition Engine ◽  
Compressed Natural Gas ◽  
Reactivity Controlled Compression Ignition ◽  
Brake Thermal Efficiency ◽  
Injection Duration ◽  
Fuel Mixtures

In the current work, an effort is made to study the influence of injection timing (IT) and injection duration (ID) of manifold injected fuels (MIF) in the reactivity controlled compression ignition (RCCI) engine. Compressed natural gas (CNG) and compressed biogas (CBG) are used as the MIF along with diesel and blends of Thevetia Peruviana methyl ester (TPME) are used as the direct injected fuels (DIF). The ITs of the MIF that were studied includes 45°ATDC, 50°ATDC, and 55°ATDC. Also, present study includes impact of various IDs of the MIF such as 3, 6, and 9 ms on RCCI mode of combustion. The complete experimental work is conducted at 75% of rated power. The results show that among the different ITs studied, the D+CNG mixture exhibits higher brake thermal efficiency (BTE), about 29.32% is observed at 50° ATDC IT, which is about 1.77, 3.58, 5.56, 7.51, and 8.54% higher than D+CBG, B20+CNG, B20+CBG, B100+CNG, and B100+CBG fuel combinations. The highest BTE, about 30.25%, is found for the D+CNG fuel combination at 6 ms ID, which is about 1.69, 3.48, 5.32%, 7.24, and 9.16% higher as compared with the D+CBG, B20+CNG, B20+CBG, B100+CNG, and B100+CBG fuel combinations. At all ITs and IDs, higher emissions of nitric oxide (NOx) along with lower emissions of smoke, carbon monoxide (CO), and hydrocarbon (HC) are found for D+CNG mixture as related to other fuel mixtures. At all ITs and IDs, D+CNG gives higher In-cylinder pressure (ICP) and heat release rate (HRR) as compared with other fuel combinations.

A Multidisciplinary Approach for the Comprehensive Assessment of Integrated Rotorcraft–Powerplant Systems at Mission Level

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Ioannis Goulos ◽  
Fakhre Ali ◽  
Konstantinos Tzanidakis ◽  
Vassilios Pachidis ◽  
Roberto d'Ippolito
Keyword(s):  
Environmental Impact ◽  
Fuel Consumption ◽  
Comprehensive Assessment ◽  
Pollutant Emissions ◽  
Operational Performance ◽  
Civil Aviation ◽  
Accurate Estimation ◽  
Nox Emissions ◽  
Reactor Model ◽  
Stirred Reactor

This paper presents an integrated methodology for the comprehensive assessment of combined rotorcraft–powerplant systems at mission level. Analytical evaluation of existing and conceptual designs is carried out in terms of operational performance and environmental impact. The proposed approach comprises a wide-range of individual modeling theories applicable to rotorcraft flight dynamics and gas turbine engine performance. A novel, physics-based, stirred reactor model is employed for the rapid estimation of nitrogen oxides (NOx) emissions. The individual mathematical models are implemented within an elaborate numerical procedure, solving for total mission fuel consumption and associated pollutant emissions. The combined approach is applied to the comprehensive analysis of a reference twin-engine light (TEL) aircraft modeled after the Eurocopter Bo 105 helicopter, operating on representative mission scenarios. Extensive comparisons with flight test data are carried out and presented in terms of main rotor trim control angles and power requirements, along with general flight performance charts including payload-range diagrams. Predictions of total mission fuel consumption and NOx emissions are compared with estimated values provided by the Swiss Federal Office of Civil Aviation (FOCA). Good agreement is exhibited between predictions made with the physics-based stirred reactor model and experimentally measured values of NOx emission indices. The obtained results suggest that the production rates of NOx pollutant emissions are predominantly influenced by the behavior of total air inlet pressure upstream of the combustion chamber, which is affected by the employed operational procedures and the time-dependent all-up mass (AUM) of the aircraft. It is demonstrated that accurate estimation of on-board fuel supplies ahead of flight is key to improving fuel economy as well as reducing environmental impact. The proposed methodology essentially constitutes an enabling technology for the comprehensive assessment of existing and conceptual rotorcraft–powerplant systems, in terms of operational performance and environmental impact.

Modeling an Enclosed, Turbulent Reacting Methane Jet With the Premixed Conditional Moment Closure Method

2013 ◽  
Author(s):  
Scott Martin ◽  
Aleksandar Jemcov ◽  
Björn de Ruijter
Keyword(s):  
Turbulent Combustion ◽  
Large Scale ◽  
Reaction Rates ◽  
Moment Closure ◽  
Scalar Dissipation ◽  
Small Scale ◽  
Conditional Moment ◽  
Progress Variable ◽  
Conditional Moment Closure ◽  
Scale Turbulence

Here the premixed Conditional Moment Closure (CMC) method is used to model the recent PIV and Raman turbulent, enclosed reacting methane jet data from DLR Stuttgart [1]. The experimental data has a rectangular test section at atmospheric pressure and temperature with a single inlet jet. A jet velocity of 90 m/s is used with an adiabatic flame temperature of 2,064 K. Contours of major species, temperature and velocities along with velocity rms values are provided. The conditional moment closure model has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes [2]. The simplified CMC model used here falls into the class of table lookup turbulent combustion models where the chemical kinetics are solved offline over a range of conditions and stored in a table that is accessed by the CFD code. Most table lookup models are based on the laminar 1-D flamelet equations, which assume the small scale turbulence does not affect the reaction rates, only the large scale turbulence has an effect on the reaction rates. The CMC model is derived from first principles to account for the effects of small scale turbulence on the reaction rates, as well as the effects of the large scale mixing, making it more versatile than other models. This is accomplished by conditioning the scalars with the reaction progress variable. By conditioning the scalars and accounting for the small scale mixing, the effects of turbulent fluctuations of the temperature on the reaction rates are more accurately modeled. The scalar dissipation is used to account for the effects of the small scale mixing on the reaction rates. The original premixed CMC model used a constant value of scalar dissipation, here the scalar dissipation is conditioned by the reaction progress variable. The steady RANS 3-D version of the open source CFD code OpenFOAM is used. Velocity, temperature and species are compared to the experimental data. Once validated, this CFD turbulent combustion model will have great utility for designing lean premixed gas turbine combustors.

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