1,199 research outputs found
Hydrogen with water addition: an exergy analysis of the internal combustion engine
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The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The internal combustion engine is likely to be used for on- and off-road vehicles for many years yet, but the push to cease using fossil fuels is strong. Hydrogen is a possible alternative fuel with both advantages and disadvantages, so understanding and quantifying the efficiency losses of burning hydrogen are important. The limits to efficiency and the compromises needed to reduce losses can be investigated using exergy analysis. This analysis of a boosted lean-burn neat hydrogen spark ignition engine investigates exergetic processes under real-world engine operating conditions. Using a two-zone combustion model to study in-cylinder processes, the results suggest exergy transfer to work improves with increasing air dilution by diverting exhaust exergy to reversible work. Injecting water could potentially control emissions through in-cylinder thermo-physical property changes. For an equivalence ratio of 0.45 with 5% water addition, the exergy transfers to heat and work decrease by 12% and 7%, respectively. Conversely, the exergy transfers to combustion-related irreversibility and exhaust rise by 2% and 81%, respectively. However, it was shown that increasing manifold air pressures and compression ratios increases the quantity of exergy directed to work and heat, while reducing exergy expelled to exhaust. This exergy analysis of a hydrogen-fueled spark ignition engine operating under real-world parameters shows the need to optimize water injection as the trade-off between engine performance and emission reductions. Understanding the fundamentals of the thermodynamic mechanisms of work loss may inform engineering improvements to minimize exergy losses and increase efficiency and work output.The author(s) declare that no financial support was received for the research and/or publication of this article
Disputatio Medica De Generatione Hominis In Ovo / Quam, ... Sub Praesidio ... Dn. Johannis Jacobi Waldschmied/ Medicinae Doctoris ... exhibet Author Dominicus Beddevole, Genevensis, In Auditorio Medico d. 3. Septemb. ...
No full textDISPUTATIO MEDICA DE GENERATIONE HOMINIS IN OVO / QUAM, ... SUB PRAESIDIO ... DN. JOHANNIS JACOBI WALDSCHMIED/ MEDICINAE DOCTORIS ... EXHIBET AUTHOR DOMINICUS BEDDEVOLE, GENEVENSIS, IN AUDITORIO MEDICO D. 3. SEPTEMB. ...
Disputatio Medica De Generatione Hominis In Ovo / Quam, ... Sub Praesidio ... Dn. Johannis Jacobi Waldschmied/ Medicinae Doctoris ... exhibet Author Dominicus Beddevole, Genevensis, In Auditorio Medico d. 3. Septemb. ... (1)
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Consensu Et Author. Magnifici Ictorum Ordinis In Illustri Ad Salam Academia, Sub Praesidio ... Dn. Joh. Volk. Bechmanns ... Dissertationem Iuridicam De Iure Braxandi in Ictorum Auditorio ad diem Octobr. h.c. Publicae Eruditorum Censurae Subiiciet Paul. Christianus Arnoldus, Olsnen. Siles. Author & Respondens
No full textCONSENSU ET AUTHOR. MAGNIFICI ICTORUM ORDINIS IN ILLUSTRI AD SALAM ACADEMIA, SUB PRAESIDIO ... DN. JOH. VOLK. BECHMANNS ... DISSERTATIONEM IURIDICAM DE IURE BRAXANDI IN ICTORUM AUDITORIO AD DIEM OCTOBR. H.C. PUBLICAE ERUDITORUM CENSURAE SUBIICIET PAUL. CHRISTIANUS ARNOLDUS, OLSNEN. SILES. AUTHOR & RESPONDENS
Consensu Et Author. Magnifici Ictorum Ordinis In Illustri Ad Salam Academia, Sub Praesidio ... Dn. Joh. Volk. Bechmanns ... Dissertationem Iuridicam De Iure Braxandi in Ictorum Auditorio ad diem Octobr. h.c. Publicae Eruditorum Censurae Subiiciet Paul. Christianus Arnoldus, Olsnen. Siles. Author & Respondens ([1])
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De. Condictione L. Si quis Conductionis. 25. C. de locato conducto. Sub Praesidio Dn. Andreae Mylii ... Publice disputabit. Author. Johann Gottfried Schönfeld/ Zitt. Lus. die 11. Iunii. M.DC.XCVI.
No full textDE. CONDICTIONE L. SI QUIS CONDUCTIONIS. 25. C. DE LOCATO CONDUCTO. SUB PRAESIDIO DN. ANDREAE MYLII ... PUBLICE DISPUTABIT. AUTHOR. JOHANN GOTTFRIED SCHÖNFELD/ ZITT. LUS. DIE 11. IUNII. M.DC.XCVI.
De. Condictione L. Si quis Conductionis. 25. C. de locato conducto. Sub Praesidio Dn. Andreae Mylii ... Publice disputabit. Author. Johann Gottfried Schönfeld/ Zitt. Lus. die 11. Iunii. M.DC.XCVI. (1)
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Dissertatio De Censu Augusti / Quam Sub Praesidio ... Dn. Ulrici Obrechti, In Alma Argentinensium Universitate Professoris Histor. ... Ad Examen Solenne Proponit Michael Förtsch/ Wertheimio-Francus Author. A. D. [...] Maii MDCLXXV.
No full textDISSERTATIO DE CENSU AUGUSTI / QUAM SUB PRAESIDIO ... DN. ULRICI OBRECHTI, IN ALMA ARGENTINENSIUM UNIVERSITATE PROFESSORIS HISTOR. ... AD EXAMEN SOLENNE PROPONIT MICHAEL FÖRTSCH/ WERTHEIMIO-FRANCUS AUTHOR. A. D. [...] MAII MDCLXXV.
Dissertatio De Censu Augusti / Quam Sub Praesidio ... Dn. Ulrici Obrechti, In Alma Argentinensium Universitate Professoris Histor. ... Ad Examen Solenne Proponit Michael Förtsch/ Wertheimio-Francus Author. A. D. [...] Maii MDCLXXV. (1)
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Tractatio Iuris Publici De Serenissimis Potentissimisque Ducibus Brunsvicensibus Et Luneburgensibus / D.O.M.A. Praeside ... Dn. Joh. Ulrico Pregizero ... In Illustri Collegio Ad Diem 10. Decembr. Placido Eruditorum Examini sistit Author Christian Ulrich Blum
No full textTRACTATIO IURIS PUBLICI DE SERENISSIMIS POTENTISSIMISQUE DUCIBUS BRUNSVICENSIBUS ET LUNEBURGENSIBUS / D.O.M.A. PRAESIDE ... DN. JOH. ULRICO PREGIZERO ... IN ILLUSTRI COLLEGIO AD DIEM 10. DECEMBR. PLACIDO ERUDITORUM EXAMINI SISTIT AUTHOR CHRISTIAN ULRICH BLUM
Tractatio Iuris Publici De Serenissimis Potentissimisque Ducibus Brunsvicensibus Et Luneburgensibus / D.O.M.A. Praeside ... Dn. Joh. Ulrico Pregizero ... In Illustri Collegio Ad Diem 10. Decembr. Placido Eruditorum Examini sistit Author Christian Ulrich Blum (1)
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Investigation of boost pressure and spark timing on combustion and NO emissions under lean mixture operation in hydrogen engines
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Data will be made available on request.Copyright © 2023 The Authors. Hydrogen may become a replacement for liquid fossil fuels, contributing to greenhouse gas emissions reductions by improving the thermal efficiency of boosted lean burn spark ignition engines. Single-zone engine combustion models are simple, but can yield useful results as a step in the design process for developing alternative fuel systems. The single-zone thermodynamic model is advanced by implementing a laminar flame speed sub-model to investigate combustion, an extended Zeldovich mechanism for nitric oxide emissions, and incorporating the Livengood-Wu integral model for knock characteristics. The results were validated using published experiments giving satisfactory predictions between simulation and experiment for spark timing variation, manifold air pressure, and equivalence ratios. A detailed analysis of boosted lean burn strategies showed that nitric oxide emissions increased with boosted pressure, hence emissions can be controlled through optimizing the excess air ratio and the start of combustion. Further techniques to achieve high thermal efficiency and to prevent knock for boosted lean burn hydrogen SI engine are discussed
Exergy analysis of the lean-burn hydrogen-fuelled engine
No full textData availability:
Data will be made available on request.Hydrogen is considered an alternative fuel for use in internal combustion engines. The internal combustion engine will likely remain in use for vehicle and stationary applications for the foreseeable future, therefore identifying and quantifying efficiency losses of burning fuels is important. Exergy analysis is a method for investigating the fundamental origins of losses, the limits to efficiency, and the engineering trade-offs required to reduce losses. This comprehensive exergy analysis of a boosted lean-burn hydrogen spark ignition engine investigates the processes involving exergy destruction under real-world conditions. This efficiency of a hydrogen SI engine and the NO emissions are evaluated by quantifying the exergy destruction for various intake manifold air pressures, lean-burn mixtures, compression ratios, and spark timings. Using an improved two-zone engine model to study in-cylinder processes, the results indicate that increasing air dilution enhances exergy transfer to work, due mainly to diverting exhaust exergy into reversible work. However, increasing air dilution also increases combustion-related exergy destruction due to greater entropy generation for leaner mixtures, but reducing heat loss decreases combustion-related irreversibility. Higher manifold air pressures and compression ratios increase the quantity of exergy directed to work and heat, whilst reducing exergy expelled to exhaust. Gaining understanding of the detail of thermodynamic mechanisms of the routes by which the work potential is lost potentially assists in engineering improvements to minimize exergy losses, and to increase efficiency and work output
Rational conjugacy classes of maximal tori in groups of Dn
No full textAuthor original manuscript (preprint)We give a concrete characterization of the rational conjugacy classes of maximal tori in groups of type Dn, with specific emphasis on the case of number fields and p-adic fields. This includes the forms associated to quadratic spaces, all of their inner and outer forms as well as the Spin groups, their simply connected covers. In particular, in this work, we handle all (simply connected) outer forms of D4.N
Dn. Iohannes Kellerus
No full textHalbfigur nach rechts, die rechte Hand in die Taille gestützt; links und rechts vom Ovalrahmen sind ein Rüstungshelm und das Wappen der Familie Keller zu sehenJoh. Meyer fecit Ao. 1703Vgl. die Zeichnung von Conrad Meyer, Signatur: Pp A4, sowie die Druckgraphik, Signatur: Keller, Johannes a) I, 2Porträt des Zürcher Bürgermeisters Johannes Keller (erstmals erwähnt 1417-1460/61)Inschrift unter dem Bild: "Dn: Iohannes Kellerus, / Reipubl: Tigur: Consul. / Ao. D. 1445"; weitere Inschrift: "Dives opum, et pacis Cellarius optimus Author / Composuit longâ bella patrata morà. / Quin etiam patriis Kyburgum finibus arcem. / Adjecit totâ cum ditione suâ."Signiert rechts unten: "Joh. Meyer fecit. Ao. 1703"Nummeriert unten in der Mitte unterhalb des Ovalrahmens: "18." Am Blattrand oben handschriftlich in brauner Tinte biografische Angaben zu Joahnnes Keller in VersformIn Peter Mortzfeld: Katalog der graphischen Porträts in der Herzog-August-Bibliothek Wolfenbüttel nicht verzeichne
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