Reacting flow analysis of a cavity-based scramjet combustor using a Jacobian-free Newton–Krylov method

2018 ◽  
Vol 122 (1258) ◽  
pp. 1884-1915
Author(s):  
R. Rouzbar ◽  
S. Eyi
Keyword(s):  
Chemical Reaction ◽  
High Speed ◽  
Fuel Injection ◽  
Computational Cost ◽  
Mixing Efficiency ◽  
Reacting Flow ◽  
Flux Vector ◽  
Flux Limiter ◽  
Scramjet Combustor ◽  
Flux Vector Splitting

ABSTRACTThe scramjet is a rather a new technology and there are many issues related to their operation, especially when it comes to the combustion processes. Combustion in high-speed flows causes various problems such as flame instability and poor fuel–air mixing efficiency. One of the methods used to overcome these problems is to recess a cavity in the combustor wall where a secondary flow is generated. In this study, a computational fluid dynamics (CFD) code is developed to analyse the reacting flow passing through the cavity-based scramjet combustor. The developed code is based on three-dimensional coupled Navier–Stokes and finite rate chemistry equations. An ethylene-air reduced chemical reaction model is used as a fuel–air combination. The Spalart–Allmaras model is utilised for turbulence closure. The non-dimensional form of the flow and chemical reaction equations are discretised using a finite volume method. The Jacobian-Free Newton–Krylov (JFNK) method is used to solve the coupled system of non-linear equations. The JFNK is a matrix-free solution method which improves the computational cost of Newton’s method. The parameters that affect the performance of the JFNK method are studied in the analysis of a scramjet combustor. The influence of the forcing term on the convergence of the JFNK method is studied in the analysis of scramjet combustor. Different upwind flux vector splitting methods are utilised. Various flux limiter techniques are employed for the calculations of higher order flux vectors. The effects of flux vector splitting and flux limiter methods on the convergence and accuracy of the JFNK method are evaluated. Moreover, the variations of the mixing efficiency with fuel injection angles are studied.

Transverse Injection Experiments within an Axisymmetric Scramjet Combustor

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Shan M. Assis ◽  
Jeyakumar Suppandipillai ◽  
Jayaraman Kandasamy
Keyword(s):  
High Speed ◽  
Fuel Injection ◽  
Flow Direction ◽  
Reacting Flow ◽  
Rear Wall ◽  
Cross Sectional ◽  
Scramjet Combustor ◽  
Transverse Injection ◽  
Downstream Flow ◽  
Injection Pressures

Abstract Investigations on the performance of a rear wall angled cavity with upstream transverse fuel injection in a Mach 1.8 flow field is experimentally studied in a non-reacting flow facility. The high speed flow is directed to a circular cross sectional supersonic combustor and proceeded towards the cavities having two consecutive angles being inclined towards the downstream flow direction. Wall mounted injector is positioned at a distance of 10 mm upstream from the cavity. Air is used as the injectant to simulate the gaseous fuel. The experiments are performed to explore the effect of the increase in injection pressures within various rear wall angled cavities by comparing with the ‘no-injection’ case and to finally assess the mixing performance of the flow. Transverse injection through upstream wall orifice of the cavities outlines a more uniform mixing compared to ‘no-injection’ configuration. Increase in injection pressures enhances mixing and stagnation pressure loss values.

scholarly journals The Effect of Fuel Injection Location on Supersonic Hydrogen Combustion in a Cavity-Based Model Scramjet Combustor

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 193 ◽  
Author(s):  
Eunju Jeong ◽  
Sean O’Byrne ◽  
In-Seuck Jeung ◽  
A. F. P. Houwing
Keyword(s):  
Equivalence Ratio ◽  
Fuel Injection ◽  
Flow Direction ◽  
Flame Structure ◽  
Flow Characteristics ◽  
Supersonic Combustion ◽  
Reacting Flow ◽  
Total Enthalpy ◽  
Scramjet Combustor ◽  
Injection Location

Supersonic combustion experiments were performed using three different hydrogen fuel-injection configurations in a cavity-based model scramjet combustor with various global fuel–air equivalence ratios. The configurations tested were angled injection at 15° to the flow direction upstream of the cavity, parallel injection from the front step, and upstream injection from the rear ramp. Planar laser-induced fluorescence of the hydroxyl radical and time-resolved pressure measurements were used to investigate the flow characteristics. Angled injection generated a weak bow shock in front of the injector and recirculation zone to maintain the combustion as the equivalence ratio increased. Parallel and upstream injections both showed similar flame structure over the cavity at low equivalence ratio. Upstream injection enhanced the fuel diffusion and enabled ignition with a shorter delay length than with parallel injection. The presence of a flame near the cavity was determined while varying the fuel injection location, the equivalence ratio, and total enthalpy of the air flow. The flame characteristics agreed with the correlation plot for the stable flame limit of non-premixed conditions. The pressure increase in the cavity for reacting flow compared to non-reacting flow was almost identical for all three configurations. More than 300 mm downstream of the duct entrance, averaged pressure ratios at low global equivalence ratio were similar for all three injection configurations.

Numerical Analysis of a Kerosene-Fueled Scramjet Combustor

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Malsur Dharavath ◽  
P. Manna ◽  
P. K. Sinha ◽  
Debasis Chakraborty
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fuel Injection ◽  
Wall Pressure ◽  
Test Facility ◽  
Reacting Flow ◽  
Significant Drop ◽  
Scramjet Combustor ◽  
Fuel Flow

A kerosene-fueled scramjet combustor was numerically analyzed in order to meet the requirement of thrust for a hypersonic test vehicle. The internal configuration of the fuel injection struts and fuel injection was arrived through computational fluid dynamics (CFD) study. The combustor was tested in the hypersonic test facility at DRDL. Numerical simulations were carried out along with facility nozzle (from throat onward) both for nonreacting and reacting flow. Three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) equations are solved along with k–ε turbulence model. Single-step chemical reaction with Lagrangian particle tracking method (LPTM) is used for combustion of kerosene fuel. Fairly good match of the top wall pressure has been obtained with experimental data for both nonreacting and reacting flows. Effects of mass flow rate of incoming vitiated air and fuel flow have been studied numerically in details. Top wall pressure distributions have been found to decrease with the decrease of the mass flow rate of vitiated air. Significant drop of wall pressure, higher thrust per unit fuel flow, and combustion efficiency have been observed with the decrease of fuel flow.

scholarly journals Event-Driven Simulation Scheme for Spiking Neural Networks Using Lookup Tables to Characterize Neuronal Dynamics

2006 ◽  
Vol 18 (12) ◽  
pp. 2959-2993 ◽  
Author(s):  
Eduardo Ros ◽  
Richard Carrillo ◽  
Eva M. Ortigosa ◽  
Boris Barbour ◽  
Rodrigo Agís
Keyword(s):  
Synaptic Plasticity ◽  
High Speed ◽  
Large Scale ◽  
Computational Cost ◽  
Brain Structures ◽  
Spike Timing ◽  
Neuronal Dynamics ◽  
Event Driven ◽  
Synaptic Dynamics

Nearly all neuronal information processing and interneuronal communication in the brain involves action potentials, or spikes, which drive the short-term synaptic dynamics of neurons, but also their long-term dynamics, via synaptic plasticity. In many brain structures, action potential activity is considered to be sparse. This sparseness of activity has been exploited to reduce the computational cost of large-scale network simulations, through the development of event-driven simulation schemes. However, existing event-driven simulations schemes use extremely simplified neuronal models. Here, we implement and evaluate critically an event-driven algorithm (ED-LUT) that uses precalculated look-up tables to characterize synaptic and neuronal dynamics. This approach enables the use of more complex (and realistic) neuronal models or data in representing the neurons, while retaining the advantage of high-speed simulation. We demonstrate the method's application for neurons containing exponential synaptic conductances, thereby implementing shunting inhibition, a phenomenon that is critical to cellular computation. We also introduce an improved two-stage event-queue algorithm, which allows the simulations to scale efficiently to highly connected networks with arbitrary propagation delays. Finally, the scheme readily accommodates implementation of synaptic plasticity mechanisms that depend on spike timing, enabling future simulations to explore issues of long-term learning and adaptation in large-scale networks.

Flux-vector splitting for compressible low mach number flow

1993 ◽  
Vol 22 (4-5) ◽  
pp. 441-451 ◽  
Author(s):  
Jörn Sesterhenn ◽  
Bernhard Müller ◽  
Hans Thomann
Keyword(s):  
Mach Number ◽  
Flux Vector ◽  
Low Mach Number ◽  
Flux Vector Splitting ◽  
Number Flow ◽  
Low Mach Number Flow

An Automated Machine Learning-Genetic Algorithm Framework With Active Learning for Design Optimization

2021 ◽  
Vol 143 (8) ◽  
Author(s):  
Opeoluwa Owoyele ◽  
Pinaki Pal ◽  
Alvaro Vidal Torreira
Keyword(s):  
Machine Learning ◽  
Active Learning ◽  
Design Optimization ◽  
Fuel Injection ◽  
A Priori ◽  
Computational Cost ◽  
Learning Approach ◽  
Data Generation ◽  
Compression Ignition Engine ◽  
Hyperparameter Selection

AbstractThe use of machine learning (ML)-based surrogate models is a promising technique to significantly accelerate simulation-driven design optimization of internal combustion (IC) engines, due to the high computational cost of running computational fluid dynamics (CFD) simulations. However, training the ML models requires hyperparameter selection, which is often done using trial-and-error and domain expertise. Another challenge is that the data required to train these models are often unknown a priori. In this work, we present an automated hyperparameter selection technique coupled with an active learning approach to address these challenges. The technique presented in this study involves the use of a Bayesian approach to optimize the hyperparameters of the base learners that make up a super learner model. In addition to performing hyperparameter optimization (HPO), an active learning approach is employed, where the process of data generation using simulations, ML training, and surrogate optimization is performed repeatedly to refine the solution in the vicinity of the predicted optimum. The proposed approach is applied to the optimization of a compression ignition engine with control parameters relating to fuel injection, in-cylinder flow, and thermodynamic conditions. It is demonstrated that by automatically selecting the best values of the hyperparameters, a 1.6% improvement in merit value is obtained, compared to an improvement of 1.0% with default hyperparameters. Overall, the framework introduced in this study reduces the need for technical expertise in training ML models for optimization while also reducing the number of simulations needed for performing surrogate-based design optimization.

Characteristics of injection of diesel fuel, rapeseed oil and their mixtures in diesel engines of various types

2021 ◽  
pp. 167-178
Author(s):  
Keyword(s):  
Diesel Engine ◽  
Diesel Fuel ◽  
Diesel Engines ◽  
Rapeseed Oil ◽  
High Speed ◽  
Fuel Injection ◽  
Experimental Studies ◽  
Fuel Injector ◽  
High Speed Diesel ◽  
Engine Type

The necessity of adapting diesel engines to work on vegetable oils is justified. The possibility of using rapeseed oil and its mixtures with petroleum diesel fuel as motor fuels is considered. Experimental studies of fuel injection of small high-speed diesel engine type MD-6 (1 Ch 8,0/7,5)when using diesel oil and rapeseed oil and computational studies of auto-tractor diesel engine type D-245.12 (1 ChN 11/12,5), working on blends of petroleum diesel fuel and rapeseed oil. When switching autotractor diesel engine from diesel fuel to rapeseed oil in the full-fuel mode, the mass cycle fuel supply increased by 12 %, and in the small-size high-speed diesel engine – by about 27 %. From the point of view of the flow of the working process of these diesel engines, changes in other parameters of the fuel injection process are less significant. Keywords diesel engine; petroleum diesel fuel; vegetable oil; rapeseed oil; high pressure fuel pump; fuel injector; sprayer

Reaction in a scalar mixing layer

1991 ◽  
Vol 233 ◽  
pp. 211-242 ◽  
Author(s):  
R. W. Bilger ◽  
L. R. Saetran ◽  
L. V. Krishnamoorthy
Keyword(s):  
Chemical Reaction ◽  
Mixing Layer ◽  
Reacting Flow ◽  
Scalar Mixing ◽  
Scalar Theory ◽  
Thermal Mixing ◽  
Fast Chemistry ◽  
The Mean ◽  
Reactive Scalars ◽  
Made In

Reaction in a scalar mixing layer in grid-generated turbulence is studied experimentally by doping half of the flow with nitric oxide and the other half with ozone. The flow conditions and concentrations are such that the chemical reaction is passive and the flow and chemical timescales are of the same order. Conserved scalar theory for such flows is outlined and further developed; it is used as a basis for presentation of the experimental results. Continuous measurements of concentration are limited in their spatial and temporal resolution but capture sufficient of their spectra for adequate second-order correlations to be made. Two components of velocity have been measured simultaneously with hot-wire anemometry. Conserved scalar mixing results, deduced from reacting and non-reacting measurements of concentration, show the independence of concentration level and concentration ratio expected for passive reacting flow. The results are subject to several limitations due to the necessary experimental compromises, but they agree generally with measurements made in thermal mixing layers. Reactive scalar statistics are consistent with the realizability constraints obtainable from conserved scalar theory where such constraints apply, and otherwise are generally found to lie between the conserved scalar theory limits for frozen and very fast chemistry. It is suggested that Toor's (1969) closure for the mean chemical reaction rate could be improved by interpolating between the frozen and equilibrium values for the covariance. The turbulent fluxes of the reactive scalars are found to approximately obey the gradient model but the value of the diffusivity is found to depend on the Damköhler number.

scholarly journals Performance evaluation of common rail direct injection (CRDI) engine fuelled with Uppage Oil Methyl Ester (UOME)

2015 ◽  
Vol 4 (1) ◽  
pp. 1-10 ◽  
Author(s):  
D.N. Basavarajappa ◽  
N. R. Banapurmath ◽  
S.V. Khandal ◽  
G. Manavendra
Keyword(s):  
Diesel Engine ◽  
Methyl Ester ◽  
Diesel Engines ◽  
High Speed ◽  
Alternative Fuels ◽  
High Pressures ◽  
Fuel Injection ◽  
Injection Timing ◽  
Engine Operation ◽  
Performance And Emission

For economic and social development of any country energy is one of the most essential requirements. Continuously increasing price of crude petroleum fuels in the present days coupled with alarming emissions and stringent emission regulations has led to growing attention towards use of alternative fuels like vegetable oils, alcoholic and gaseous fuels for diesel engine applications. Use of such fuels can ease the burden on the economy by curtailing the fuel imports. Diesel engines are highly efficient and the main problems associated with them is their high smoke and NOx emissions.  Hence there is an urgent need to promote the use of alternative fuels in place of high speed diesel (HSD) as substitute. India has a large agriculture base that can be used as a feed stock to obtain newer fuel which is renewable and sustainable. Accordingly Uppage oil methyl ester (UOME) biodiesel was selected as an alternative fuel. Use of biodiesels in diesel engines fitted with mechanical fuel injection systems has limitation on the injector opening pressure (300 bar). CRDI system can overcome this drawback by injecting fuel at very high pressures (1500-2500 bar) and is most suitable for biodiesel fuels which are high viscous. This paper presents the performance and emission characteristics of a CRDI diesel engine fuelled with UOME biodiesel at different injection timings and injection pressures. From the experimental evidence it was revealed that UOME biodiesel yielded overall better performance with reduced emissions at retarded injection timing of -10° BTDC in CRDI mode of engine operation.

Fuel Injection System for a High Speed One Cylinder S.I.Engine

2001 ◽  
Author(s):  
Göran Almkvist ◽  
Tomas Karlsson ◽  
Styrbjörn Gren ◽  
Jörgen Bengtsson ◽  
Conny Andersson ◽  
...  
Keyword(s):  
High Speed ◽  
Fuel Injection ◽  
Injection System ◽  
Fuel Injection System
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