PROJECT DURATION:           July 2017 - December 2019
DURATA PROIECTULUI:        Iulie 2017 - Decembrie 2019

PROJECT LEADER:              National Institute for Laser, Plasma and Radiation Physics, Magurele 077125, Ilfov, Romania
CONDUCATOR PROIECT:      Institutul National de Cercetare-Dezvoltare pentru Fizica Laserilor, Plasmei si Radiatiei, Magurele 077125, Ilfov, Romania

Contract value:                      850.000 lei

Valoare contract:                   850.000 lei

The research team:                PAVEL Nicolaie, PhD             (CS I)

Echipa de cercetare:              DASCALU Traian, PhD           (CS I)  (July 2017 - August 2018)

                                            DINCA Mihai, PhD                  (CS II)

                                            STANCIU George, PhD                          (CS)

                                            VASILE Nicolae-Tiberius, PhD                (CS)   (since September 2018)

                                            CROITORU Gabriela, PhD student          (CS)   (July 2017 - July 2019)

                                            BRANDUS Catalina-Alice                       (CS)   (since August 2019)

                                            GRIGORE Oana Valeria, PhD student     (CS)

                                            VOICU Flavius-Marian, PhD student        (CS)
 

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● The ignition by laser of inflammable air-fuel mixtures, in principal in automobile engines or for energy cogeneration in natural-gas stationary engines, has been seen recently as a possible answer to human concern on environmental impact of the gases emitted by such equipments. For example, an automotive manufacturer has to meet strict environmental legislation demands, for which at least two critical engine performances: the fuel economy and exhaust gas emission must always be considered. In respect to these issues, our research group has shown recently that ignition by laser can lower the fuel consumption, decrease the CO and HC emissions, increase the stability and improve the performances and efficiency of a real four-cylinder engine. This is because laser ignition has several advantages in comparison with classical ignition by a spark plug: a) there is no electrode to quench a flame propagation kernel resulting shorter ignition delays and faster combustion; b) the energy required for ignition by laser is lower, or c) the position of ignition can be chosen.
● Another advantage of laser ignition is its ability to ignite mixtures with air-fuel ratio (lambda) larger than unit (this is the stoichiometric ratio, common for gasoline automobile engine with internal combustion). In our experiments, one-beam laser sparks were used to ignite air-fuels mixture with lambda up to 1.21. The main purposes of this project is the realization of a laser spark with multiple (up to five) beams (this is a technological challenge) and the study of the influence of various parameters (like in-space distribution of the ignition points or time-dependent firing) on ignition of lean air-fuel mixtures of different kinds (this is the fundamental aspect of this project, with great implications on environment). Further increase of lambda will access important advantages of laser ignition, such as leaner operation, reductions in emissions, lower idle speed and improved combustion stability.
● The main objectives of this project are:
O1. Realization of a compact, high-peak power, passively Q-switched Nd:YAG/Cr⁴⁺:YAG laser with multiple-beam output;
O2. Ignition in a static chamber of various inflammable mixtures and determination of the lean limit that still can be ignited for each combustible composition;
O3. Improving of the laser spark-plug like configuration such to be used in adverse conditions of vibrations and temperatures, as well as for ignition of turbulent media.

1. STAGE I. July - December 2017
2. STAGE II. January - December 2018
3. STAGE III. January - December 2019
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RESULTS
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1. ETAPA I. Iulie - Decembrie 2017
● A fost proiectat laserul comutat pasiv Nd:YAG/Cr⁴⁺:YAG cu patru fascicule.
● A fost proiectata camera statica pentru experimentele de aprindere cu laser.
● In colaborare cu Universitatea Politehnica Bucuresti, au fost efectuate experimente de aprindere laser pe un motor K7M 710 (motor Dacia, Renault), in conditii de functionare specifice traficului urban (2000 rpm, sarcina 2 bar, amestec stoichiometric aer-combustibil). Au fost realizate simulari privind imbunatatirea performantelor motorului prin schimbarea locului in care se efectueaza aprinderea combustibilului (acest aspect, al posibilitatii de a schimba pozitia aprinderii in motor, fiind un avantaj al aprinderii cu laser in comparatie cu aprinderea clasica cu bujii electrice).
● Diseminare: O prezentare orala la o conferinta cu participare internationala; o lucrare publicata in proceeding indexat ISI - Web of Knowledge. ___________________________________________________________________________________________________________________________________________________________________________
2.  ETAPA II. Ianuarie - Decembrie 2018
● A fost realizat un laser Nd:YAG/Cr⁴⁺:YAG cu patru fascicule, toate fasciculele avand caracteristici ale pulsului (energie si durata) corespunzatoare pentru a induce, dupa focalizare, fenomenul de ‘air breakdown’ (Fig. 1).
● Au fost investigate performantele unui motor de automobil, cu patru cilindrii, KTM 710, care a fost operat numai cu bujii laser (Fig. 2). Au fost masurati diferiti parametrii ai motorului: a) puterea si consumul; b) stabilitatea in functionare; c) timpii de ardere; d) emisiile CO, THC si NOx, la viteza de 2000 rpm si sarcina de 2 bar, pentru amestecuri de combustibil cu lambda~1 (amestec stoichiometric) si lambda~1.25 (amestec sarac in combustibil); s-a determinat avansul optim pentru fiecare regim de operare. Experimentele au fost facute in colaborare cu Univ. Politehnica Bucuresti si cu Renault Technologie Roumanie.
● A fost pregatita camera statica, pentru a se studia influenta distributiei spatiale (aprindere in patru puncte) a aprinderii cu laser (Fig. 3).
● A fost obtinuta emisie laser in regim de comutarea a factorului de calitate (Q-switch) de la ghiduri de unda circulare (diametrul de 100 μm) care au fost realizate in medii active Nd:YAG si Nd:YVO₄ prin tehnica scrierii directe cu fascicul laser cu durata de ordinul fs. Regimul de Q-switch a fost de tip pasiv, fiind realizat cu cristale Cr⁴⁺:YAG cu absorbtie saturabila.
● Diseminare: Doua articole publicate in reviste indexate ISI Web of Knowledge; sase prezentari la conferinte internationale; o lucrare publicata in proceeding indexat ISI - Web of Knowledge; o propunere de brevet, OSIM.

     
 Fig. 1. Laser Nd:YAG/Cr⁴⁺:YAG care permite aprinderea in patru puncte.       Fig. 2. Motor KTM 710 in timpul functionarii cu bujii laser. LSP: laser spark plug.                  Fig. 3. Camera statica. P: port.
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3. ETAPA III. Ianuarie - Decembrie 2019
● In colaborare cu Fraunhofer Institute for Applied Physics and Precision Engineering (Fraunhofer IOF), Jena, Germania, a fost realizat un prototip de bujie laser, in care fixarea elementelor optice in monturile metalice ale bujiei s-a facut prin lipire metalica, folosind tehnica de "Soldejet Bumping" (Fig. 4).
● Au fost efectuate experimente de operare a motorului KTM 710 la sarcini partiale mai inalte: 1600 rpm, sarcina 3.3 bar si 2000 rpm, sarcina 5 bar, pentru amestec combustibil stoichiometric (lamda~1) si sarac (lambda~1.25), avans variabil (colaborare cu Univ. Politehnica Bucuresti).
● Experimente de aprindere in camera statica a amestecului combustibil aer - metan, cu diferite concentratii de saracire. Masuratori ale presiunii dezvoltate in timpul aprinderii, in functie de numarul punctelor de aprindere (experimente in desfasurare; Fig. 5).
● Diseminare: Doua articole publicate in reviste indexate ISI Web of Knowledge; doua prezentari la conferinte internationale; o propunere de brevet OSIM.

               
Fig. 4. a) Dispozitive de tip bujie laser realizate in colaborare cu Fraunhofer IOF, Jena, Germania prin             Fig. 5. a) Montajul experimental pentru inregistrarea diagramelor de presiunea si imagistica Schlieren.
tehnica de lipire metalica ”Solderjet Bumping”. b) Fenomenul de ”air breakdown” indus de bujia laser.                           b) Vedere in camera statica a celor patru puncte in care se face aprinderea cu laser.
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ARTICLES PUBLISHED IN ISI JOURNALS
1. N. Pavel, M. Baerwinkel, P. Heinz, D. Brueggemann, G. Dearden, G. Croitoru, O. V. Grigore, “Laser Ignition - Spark Plug Development and Application in Reciprocating Engines,”
Prog. Quantum Electron. 58, 1-32, 1-32 (2018). https://www.sciencedirect.com/science/article/pii/S0079672718300107?via%3Dihub  [2018 Impact Factor: 5.105]
2. G. Croitoru (Salamu) and N. Pavel, “Passive Q-Switching by Cr⁴⁺:YAG Saturable Absorber of Buried Depressed-Cladding Waveguides Obtained in Nd-Doped Media by Femtosecond Laser Beam Writing,”
Materials 11(9), 1689 (2018);  http://www.mdpi.com/1996-1944/11/9/1689  [2018 Impact Factor: 2.972]
3. N. Pavel, R. Chiriac, A. Birtas, F. Draghici, and M. Dinca, “On the improvement by laser ignition of the performances of a passenger car gasoline engine,” Opt. Express 27(8), A385-A396 (2019);  https://doi.org/10.1364/OE.27.00A385 [2018 Impact Factor: 3.561]
Note: a. A short description of this publication was included in Laser Focus World, May 2019 issue, section World News: pdf
web page: https://www.laserfocusworld.com/home/article/16556331/lasers-in-transportation-laser-ignition-quantitatively-improves-performance-of-gasoline-engines
b. A summary of the article was published in ee NEWS Europe at:
                    https://www.eenewseurope.com/news/forget-spark-plug-use-laser-ignition-gasoline-ices
and in ECI Electronique, in French, at the web address:   
                     https://www.ecinews.fr/news/fini-les-bougies-lallumage-laser-ameliore-le-rendement-de-30
c. A highlight of the article was published in Advances In Engineering, Appplied Physics section, at:
                https://advanceseng.com/gasoline-engine-operating-lean-air-fuel-mixture-laser-ignition/
4. P. Ribes-Pleguezuelo, N. Pavel, E. Beckert, C. Damm, A. Bodemann, O. V. Grigore, G. Croitoru, C. A. Brandus, N. T. Vasile, R. Eberhardt, and A. Tuennermann, “Assembly process and optical performances for a golden laser spark-plug device,” Opt. Eng. 58(6), 065101 (2019). https://doi.org/10.1117/1.OE.58.6.065101   [2018 Impact Factor: 1.209]
5. N. T. Vasile, N. Pavel, “Multi-point laser-induced ignition of air-methane mixtures by a high peak-power passively Q-switched Nd:YAG/Cr⁴⁺:YAG laser,” Opt. & Laser Techn. 141, 107169 (2021). [2019 Impact Factor: 3.233]

PROCEEDINGS
1.  A. Birtas, N. Boicea, F. Draghici, R. Chiriac, G. Croitoru, M. Dinca, T. Dascalu and N. Pavel, “On the assessment of performance and emissions characteristics of a SI engine provided with a laser ignition system,” IOP Conf. Ser.: Mater. Sci. Eng. 252, art. 012071 (2017); https://iopscience.iop.org/article/10.1088/1757-899X/252/1/012071
2.  A. Birtas, N. Boicea, G. Croitoru, M. Dinca, N. Pavel, F. Draghici, R. Chiriac “On the possibility to improve petrol engine operation by laser ignition,” Energy Procedia 157, 1022-1028 (2019); Proceeding paper, Technologies and Materials for Renewable Energy, Environment and Sustainability (TMREES), TMREES18, 19-21 Sept. 2018, Athens, Greece. https://doi.org/10.1016/j.egypro.2018.11.269

CONFERENCES
1.  A. Birtas, N. Boicea, F. Draghici, R. Chiriac, G. Croitoru, M. Dinca, T. Dascalu and N. Pavel, “On the assessment of performance and emissions characteristics of a SI engine provided with a laser ignition system,” CAR 2017, The 11^th Edition of The International Congress of Automotive and Transport Engineering, November 8-11 2017, University of Pitesti, Pitesti, Romania; presentation CAR 2017_090.
2.  A. Birtas, N. Boicea, F. Draghici, R. Chiriac, G. Croitoru, M. Dinca, and N. Pavel, “On the performances of a 4-cylinder automobile engine with classical spark plug and laser ignition systems,” The 6th Laser Ignition Conference, 23-27 April 2018, Pacifico Yokohama, Yokohama, Japan, presentation LIC3-5.
3.  N. Pavel, O. V. Grigore, G. Croitoru, and M. Dinca, “A high-peak power passively Q-switched Nd:YAG/Cr⁴⁺:YAG compact laser with multiple-beam output,” The 6th Laser Ignition Conference, 23-27 April 2018, Pacifico Yokohama, Yokohama, Japan, presentation LICp6-1.
4. G. Stanciu, F. Voicu, C. A. Brandus, C. Tihon, L. Gheorghe, T. Dascalu, “ Highly transparent Yb³⁺-doped Y₂O₃ sesquioxide ceramics,” TIM18 Physics Conference, 24-26 May 2018, Timisoara, Romania; CM-P10, poster presentation.
5. G. Croitoru and N. Pavel, “Passive Q-switch by Cr⁴⁺:YAG saturable absorber laser operation of circular, buried depressed-cladding waveguides inscribed by fs-laser beam in Nd:YAG and Nd:YVO₄,” 8th EPS-QEOD EUROPHOTON CONFERENCE, Solid State, Fibre, and Waveguide Coherent Light Sources, 02-07 September, 2018, Barcelona, Spain; Europhysics Conference Abstracts Volume 42C, ISBN 979-10-96389-10-0; presentation WeP.16 (poster presentation).
6. N. Pavel, G. Croitoru, O. V. Grigore, M. Dinca, T. Dascalu, “Laser ignition - A review of laser spark plug development and achievements on engine ignition,” Joint International Student Conference on Photonics & Modern Laser Application Conference 2018, ISCP-INDLAS 2018, September 3-7, 2018, Alba-Iulia, Romania; Plenary lesson; Book of abstracts ISBN 978-606-16-1001-3; pages 19-21.
7. A. Birtas, N. Boicea, G. Croitoru, M. Dinca, N. Pavel, F. Draghici, R. Chiriac, “On the possibility to improve petrol engine operation by laser ignition,” TMREES Conference Series, Technologies and Materials for Renewable Energy, Environment and Sustainability, TMREES18, 19-21 Sept. 2018, Athens, Greece; presentation 175.
8. G. Stanciu, L. Gheorghe, F. Voicu, C. A. Brandus, C. Tihon, G. Croitoru, and N. Pavel, “Fabrication and laser performance of highly transparent Nd:YAG ceramics,” TIM 19 Physics Conference, 29 - 31 May 2019, Timisoara, Romania, presentation CM-P08 (poster presentation).
9. N. Pavel, R. Chiriac, A. Birtas, N. Boicea, F. Draghici, G. Croitoru, and M. Dinca, “Lean-mixture operation of a passenger car gasoline engine ignited by passively Q-switched Nd:YAG/Cr⁴⁺:YAG laser spark plugs,” CLEO Europe - EQEC 2019 Conference, 23-27 June 2019, Munich, Germany, presentation CM-P.13 (poster presentation).

PATENTS
1.  M. Ganciu-Petcu, O. S. Stoican, A. L. Groza, N. Pavel, G. Croitoru, A. Marcu, ”Sistem Combinat Electric-Laser pentru Controlul Descărcărilor Electrice,” Romanian patent, No. RO133688-A0, Publication date 30.10.2019; OSIM application number a 2018 01123 / 19.12.2018.
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