From Pillars to AI Technology-Based Forest Fire Protection Systems

The importance of forest environment in the perspective of the biodiversity as well as from the economic resources which forests enclose, is more than evident. Any threat posed to this critical component of the environment should be identified and attacked through the use of the most efficient available technological means. Early warning and immediate response to a fire event are critical in avoiding great environmental damages. Fire risk assessment, reliable detection and localization of fire as well as motion planning, constitute the most vital ingredients of a fire protection system. In this chapter, we review the evolution of the forest fire protection systems and emphasize on open issues and the improvements that can be achieved using artificial intelligence technology. We start our tour from the pillars which were for a long time period, the only possible method to oversee the forest fires. Then, we will proceed to the exploration of early AI systems and will end-up with nowadays systems that might receive multimodal data from satellites, optical and thermal sensors, smart phones and UAVs and use techniques that cover the spectrum from early signal processing algorithms to latest deep learning-based ones to achieving the ultimate goal

Χαρακτηριστικά τυρβώδους ροής και ανάμειξης φλογών προπανίου-αέρα, σταθεροποιημένων σε αξονοσυμμετρικό σώμα, υπό την επίδραση διαστρωμάτωσης και προθέρμανσης

The isothermal and reacting time mean and fluctuating flow fields along with the mixing characteristics in the near wake region of a premixer/disk stabilizing arrangement, have been investigated and analyzed for a variety of inlet mixture compositions and preheating temperatures. The burner consists of three concentric disks that form two premixing cavities. Fuel (propane) is injected in the first cavity and is partially premixed with air flowing through the cavity system, resulting into a stratified equivalence ratio profile at the inlet of the stabilization region. Four levels of preheat temperatures, of the incoming reactants, ranging from 300 to 743 , for lean and ultra-lean mixtures have been studied. The employed preheated and stratified mixture burner is capable of anchoring flames at very lean mixtures, expanding the lean flammability limits and promoting flame stabilization at global equivalence ratio values, as low as Φ=0.13 at 743 . This study has been motivated by the fact that bluff body flame stabilization characteristics under both inlet mixture stratification and preheat have not been documented extensively so far.For the non-reacting cases, Particle Image Velocimetry (PIV) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis have been performed to evaluate the flow and mixing fields developing in the downstream near wake. The impact of preheat on the developing disk wake topology and mixing performance has been examined and its operational parameters have been evaluated. Further the study has helped to elucidate the effects of inlet mixture stratification alone or in combination with preheat on the performance characteristics of the disk stabilizer and to identify parameters controlling the recirculation zone mixture placement. For the reacting cases, the time mean and fluctuating reacting velocity fields, developing in the downstream near wake, have been evaluated with Particle Image Velocimetry (PIV) analysis, while OH* Chemiluminescence emissions and exhaust gas measurements have been obtained to evaluate the impact of preheat on the flame topology characteristics, emissions performance and combustion efficiency. Moreover, flame properties such as inlet mixture reactivity, 2D aerodynamic strain rates, Damköhler and Karlovitz numbers, flame brush thicknesses and turbulent flame speeds, at various locations along the flame edge, have been estimated and analyzed to elucidate the effects of turbulence, inlet preheat and mixture composition on flame structure topology and anchoring characteristics.Στην παρούσα εργασία μελετήθηκαν και αναλύθηκαν τα ισόθερμα και αντιδρώντα, χρονικά μέσα και διακυμαινόμενα, πεδία ροής καθώς και τα χαρακτηρίστηκα ανάμειξης στην περιοχή κατάντη ενός προ-αναμείκτη καυστήρα, για μια σειρά μειγμάτων καυσίμου-αέρα και επίπεδων προθέρμανσης των αντιδρώντων. Ο καυστήρας αποτελείται από τρείς ομοαξονικούς δίσκους οι οποίοι δημιουργούν δύο κοιλότητες. Το καύσιμο (προπάνιο) παροχετεύεται στην πρώτη κοιλότητα και αναμειγνύεται μερικώς με τον αέρα, καταλήγοντας σε μια διαστρωματωμένη κατανομή σχετικού λόγου καυσίμου αέρα στην είσοδο της περιοχής σταθεροποίησης. Μελετήθηκαν τέσσερα επίπεδα προθέρμανσης των αντιδρώντων τα οποία κυμαίνονται από 300 έως 743Κ, για πτωχά και υπέρ-πτωχα μείγματα. Ο συγκεκριμένος καυστήρας, προθέρμανσης και διαστρωμάτωσης των αντιδρώντων, επιτρέπει τη σταθεροποίηση φλόγας για πολύ πτωχά μείγματα, διευρύνοντας τα πτωχά όρια απόσβεσης και προωθώντας την σταθεροποίηση σε ολικούς σχετικούς λόγους καυσίμου αέρα της τάξης του Φ=0.13 στους 743Κ. Βασικό κίνητρο για την συγκεκριμένη μελέτη ήταν ότι τα χαρακτηριστικά σταθεροποίησης φλογών, σε σταθεροποιητικό σώμα, υπό την επίδραση διαστρωμάτωσης και προθέρμανσης των αντιδρώντων δεν έχουν, ακόμη, εκτενώς καταγραφεί. Για τις ισόθερμες (μη-αντιδρώσες) περιπτώσεις, πραγματοποιήθηκαν μετρήσεις Απεικόνισης Ταχυμετρίας Σωματιδίων (PIV) και Φασματοσκοπίας Υπέρυθρου με Μετασχηματισμό Fourier (FT-IR) για την αξιολόγηση των πεδίων ροής και ανάμειξης που αναπτύσσονται στην περιοχή της κατάντη ανακυκλοφορίας. Επίσης μελετήθηκε η επίδραση της προθέρμανσης του αντιδρώντος μείγματος στα χαρακτηριστικά ανάμειξης και αξιολογήθηκαν τα χαρακτηριστικά λειτουργείας του καυστήρα. Επιπλέον η παρούσα μελέτη βοήθησε στο να διευκρινιστεί η επίδραση της διαστρωμάτωσης του μείγματος, μόνη της ή σε συνδυασμό με την προθέρμανση, στα χαρακτηριστικά απόδοσης του φλογοσταθεροποιητή, καθώς και να αναγνωριστούν παράμετροι ελέγχου της τοπολογίας του μείγματος στην περιοχή της ανακυκλοφορίας.Για τις αντιδρώσες περιπτώσεις, πραγματοποιήθηκαν επίσης μετρήσεις Απεικόνισης Ταχυμετρίας Σωματιδίων (PIV) για το μέσο και διακυμαινόμενο πεδίο ταχυτήτων, μετρήσεις εκπομπών χημειοφωταυγαζώντων ριζικών OH* καθώς και μετρήσεις των εκπεμπόμενων ρύπων με σκοπό να αξιολογηθεί η επίδραση της προθέρμανσης των αντιδρώντων στην τοπολογία της φλόγας, στις εκπομπές ρύπων και στην απόδοση της καύσης. Επιπλέον, εκτιμήθηκαν και αναλύθηκαν ιδιότητες της φλόγας όπως οι διδιάστατες αεροδυναμικές τάσεις που επιδρούν σε αυτήν, οι αριθμοί Damköhler και Karlovitz, το μέσο πάχος του τυρβώδους μετώπου της φλόγας και οι ταχύτητα διάδοσης του τυρβώδους μετώπου, σε διάφορες θέσεις πάνω στο μέτωπο της φλόγας, με σκοπό να διευκρινιστεί η επίδραση της τύρβης καθώς και της προθέρμανσης και σύστασης του μείγματος στην δομή της φλόγας και στα χαρακτηριστικά σταθεροποίησής της

A Study of Recirculating Flow Fields Downstream of a Diverse Range of Axisymmetric Bluff Body Geometries Suitable for Flame Stabilization

This work investigates the non-reacting time averaged and fluctuating flow field characteristics downstream of a variety of axisymmetric baffles, operating in combination with an upstream double-cavity premixer arrangement. The study aims to broaden knowledge with respect to the impact of different bluff body shapes, leading and trailing edge flow contours, blockage ratios and incoming flow profiles impinging on the bluff body, on the development and properties of the downstream recirculating wake. Particle Image Velocimetry (PIV) measurements have been employed to obtain the mean and turbulent velocity fields throughout the centrally located recirculation zone and the adjacent developing toroidal shear layer. The results are helpful in demarcating the cold flow structure variations in the near wake of the examined baffles which support and, to some extent, determine the flame anchoring performance and heat release disposition in counterpart reacting configurations. Additionally, such results could also assist in the selection of the most suitable flame stabilization configuration for fuels possessing challenging combustion behavior such as multi-component heavier hydrocarbons, biofuels, or hydrogen blends

A comparative study of the effect of varied reaction environments on a swirl stabilized flame geometry via optical measurements

The present work is a part of a larger experimental campaign which examines the behaviour of various fuels on a swirl stabilized flame burner configuration. Overall, detailed speciation measurements and temperature measurements were combined with optical measurements. The work presented here concerns the part of the experimental campaign which deals with the optical characteristics of the examined flames. The work adds to the growing database of experimental measurements assessing engine-relevant reaction environments which shift from traditional ones in order to meet pollutant emission regulations and efficiency standards. Here, the oxidation of several commonly used fuel and fuel surrogates that are subjected to the addition of a bio-derived fuel additive (dimethyl ether) and emulated exhaust gas recirculation (EGR) is studied in a laboratory-scale swirl stabilized burner. The natural flame chemiluminescence has been exploited to selectively measure line of sight CH* and OH* profiles for combinations of these fuels and reaction environments. As a result, the geometry and intensity of the reaction and oxidation zones have been parametrically evaluated for a sizable number of initial conditions. From an analysis of the collected data, a chemical uniqueness in methane and propane flames has been found along with a change in flame topology as a function reactant temperature and dilution with inert gases, while the flames were virtually unaffected by all other variations in reaction conditions. This insensitivity provides confidence in the use of tailored in-cylinder fluid dynamic/chemical interactions to extend engine operating conditions to otherwise difficult regimes.The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA grant agreement no 607214. All authors are additionally grateful to the SMARTCATS action.peer-reviewed2020-01-0

Data analysis to assess part quality in DED-LB/M based on in-situ process monitoring

LANE 2022, 4-8 September 2022, Fürth, GermanyIn the field of Laser beam Direct Energy Deposition (DED-LB/M) for metal additive manufacturing, the implementation of qualification strategies parts from monitoring data and reduced order models is presently at low level of maturity. In this work, a methodology and a suite of novel data analysis tools targeting the joint analysis of multimodal data: process parameters, coaxial thermal imaging and part quality by Computer Tomography scans is presented. To demonstrate the proposed approach, a set of stainless-steel coupons were built with varying process parameters (power, process speed) and path planning strategies. Exploratory data analysis and feature engineering was performed on the dataset: process indicators, thermal and geometrical monitoring features are correlated to spatially resolved defects (mainly cracks) as well as the overall part quality obtained from the inspection phase paving the way for further implementation of in-situ process monitoring as a reliable tool for process optimization and qualification

A comparative study of the effect of varied reaction environments on a swirl stabilized flame geometry via optical measurements

The present work is a part of a larger experimental campaign which examines the behaviour of various fuels on a swirl stabilized flame burner configuration. Overall, detailed speciation measurements and temperature measurements were combined with optical measurements. The work presented here concerns the part of the experimental campaign which deals with the optical characteristics of the examined flames. The work adds to the growing database of experimental measurements assessing engine-relevant reaction environments which shift from traditional ones in order to meet pollutant emission regulations and efficiency standards. Here, the oxidation of several commonly used fuel and fuel surrogates that are subjected to the addition of a bio-derived fuel additive (dimethyl ether) and emulated exhaust gas recirculation (EGR) is studied in a laboratory-scale swirl stabilized burner. The natural flame chemiluminescence has been exploited to selectively measure line of sight CH* and OH* profiles for combinations of these fuels and reaction environments. As a result, the geometry and intensity of the reaction and oxidation zones have been parametrically evaluated for a sizable number of initial conditions. From an analysis of the collected data, a chemical uniqueness in methane and propane flames has been found along with a change in flame topology as a function reactant temperature and dilution with inert gases, while the flames were virtually unaffected by all other variations in reaction conditions. This insensitivity provides confidence in the use of tailored in-cylinder fluid dynamic/chemical interactions to extend engine operating conditions to otherwise difficult regimes.The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA grant agreement no 607214. All authors are additionally grateful to the SMARTCATS action.2020-01-0