Experimental and numerical investigation of a simplified exhaust model

A simplified experimental equipment was built to investigate heat radiation and free convection around hot exhaust pipe. Temperatures were measured on the surface of the pipe as like as on heat insulating and -reflecting aluminum shield. Special care was taken to the temperature measuring method: result proved that inappropriate fixing of measuring thermocouples lead to an error of up to 30 % in the temperature-increase values. A detailed 1D numerical model was set up and parametrized so as to the calculation results can be fitted to measured temperature values. In this way thermal properties of the surfaces – as emissivities, absorption coefficients and convective heat transfer coefficients – were determined for temperature sweeps and stationary state cases. The used methods are to be further improved for real automotive parts and higher temperatures

Octopamine increases the excitability of neurons in the snail feeding system by modulation of inward sodium current but not outward potassium currents

Background: Although octopamine has long been known to have major roles as both transmitter and modulator in arthropods, it has only recently been shown to be functionally important in molluscs, playing a role as a neurotransmitter in the feeding network of the snail Lymnaea stagnalis. The synaptic potentials cannot explain all the effects of octopamine-containing neurons on the feeding network, and here we test the hypothesis that octopamine is also a neuromodulator. Results: The excitability of the B1 and B4 motoneurons in the buccal ganglia to depolarising current clamp pulses is significantly (P << 0.05) increased by (10 mu M) octopamine, whereas the B2 motoneuron becomes significantly less excitable. The ionic currents evoked by voltage steps were recorded using 2-electrode voltage clamp. The outward current of B1, B2 and B4 motoneurons had two components, a transient I-A current and a sustained I-K delayed-rectifier current, but neither was modulated by octopamine in any of these three buccal neurons. The fast inward current was eliminated in sodium - free saline and so is likely to be carried by sodium ions. 10 mu M octopamine enhanced this current by 33 and 45% in the B1 and B4 motoneurons respectively (P << 0.05), but a small reduction was seen in the B2 neuron. A Hodgkin-Huxley style simulation of the B1 motoneuron confirms that a 33% increase in the fast inward current by octopamine increases the excitability markedly. Conclusion: We conclude that octopamine is also a neuromodulator in snails, changing the excitability of the buccal neurons. This is supported by the close relationship from the voltage clamp data, through the quantitative simulation, to the action potential threshold, changing the properties of neurons in a rhythmic network. The increase in inward sodium current provides an explanation for the polycyclic modulation of the feeding system by the octopamine-containing interneurons, making feeding easier to initiate and making the feeding bursts more intense

Complex study of H-induced structural rearrangements in FeZr glasses

Microstructural changes and relaxation processes were examined in Fe-Zr based rapidly solidified samples. These phenomena occur far below crystallization temperature in the course of heat treatment, or even at room temperature, induced by absorbed hydrogen

Experimental and numerical investigation of a simplified exhaust model

A simplified experimental equipment was built to investigate heat radiation and free convection around hot exhaust pipe. Temperatures were measured on the surface of the pipe as like as on heat insulating and -reflecting aluminum shield. Special care was taken to the temperature measuring method: result proved that inappropriate fixing of measuring thermocouples lead to an error of up to 30 % in the temperature-increase values. A detailed 1D numerical model was set up and parametrized so as to the calculation results can be fitted to measured temperature values. In this way thermal properties of the surfaces – as emissivities, absorption coefficients and convective heat transfer coefficients – were determined for temperature sweeps and stationary state cases. The used methods are to be further improved for real automotive parts and higher temperatures

Otto-motorok teljes terhelésen alkalmazott sztöchiometrikus üzemének lehetőségei az EURO 7 tekintetében: Possibilities of Full-Load Stoichiometric Operation of Gasoline Engines with Regard to EURO 7

Meeting the requirements of future emission standards (EURO 7) is a significant challenge for engine development, which requires the integration of new methods into practice. Presently, gasoline engines use enrichment at full load to cool components (e.g., cylinder head) and reduce exhaust temperature. In this case, the three-way catalyst operates with low efficiency and the emission is also increased. The present study offers opportunities for development engineers to achieve λ=1 at full load. Kivonat A jövőbeli emissziós előírások (EURO 7) teljesítése jelentős kihívást jelent a motorfejlesztés számára, melyhez új módszerek integrálására lesz szükség. Jelenleg Otto-motoroknál teljes terhelésen dúsítással oldják meg az alkatrészek hűtését (pl. hengerfej) és a kipufogógáz hőmérséklet csökkentését. Ez esetben a katalizátor alacsony hatásfokkal üzemel és megnő az emisszió. Jelen tanulmány olyan lehetőségeket kíván összegyűjteni a mérnökök számára, amelyek segítenek teljes terhelésen a λ=1 megvalósításában. &nbsp

Investigation of Surface and Bulk Processes in Mg-based Alloys during Hydrogen Absorption

Different Mg-based alloys were tailored and prepared to investigate the surface and bulk processes during hydrogen absorption. Volumetric-, resistance-, XRD-, optical-, and mass measurements were carried out. Heat treatment experiments showed that the short-term thermal stability limits (during heating up at 5 K/min) of the amorphous samples were between 125-175 ° C, while long-term stability (during 24h heat treatment) is always lower – between 80 and 150°C. Nanocrystalline alloys were stable up to 300°C. Hydrogen absorption measurements were executed between 25 and 300°C. Pd-containing alloys were found to be the fastest absorbers, and 200°C was the optimal temperature regarding absorption rate. Etching the samples previously in HF solution enhances absorption by inducing surface cracking. This phenomenon was thoroughly examined by optical microscopy. The effect of hydrogen on the crystallization properties of MgNiPd sample was determined via in-situ resistance measurements

Investigation of Surface and Bulk Processes in Mg-based Alloys during Hydrogen Absorption

Different Mg-based alloys were tailored and prepared to investigate the surface and bulk processes during hydrogen absorption. Volumetric-, resistance-, XRD-, optical-, and mass measurements were carried out. Heat treatment experiments showed that the short-term thermal stability limits (during heating up at 5 K/min) of the amorphous samples were between 125-175 ° C, while long-term stability (during 24h heat treatment) is always lower – between 80 and 150°C. Nanocrystalline alloys were stable up to 300°C. Hydrogen absorption measurements were executed between 25 and 300°C. Pd-containing alloys were found to be the fastest absorbers, and 200°C was the optimal temperature regarding absorption rate. Etching the samples previously in HF solution enhances absorption by inducing surface cracking. This phenomenon was thoroughly examined by optical microscopy. The effect of hydrogen on the crystallization properties of MgNiPd sample was determined via in-situ resistance measurements

A dopamin és a szerotonin lehetséges szabályozó szerepe a csigák táplálkozásában = The possible role of dopamine and serotonin in the regulation of feeding behavior in gastropods

Összefoglalás: A dopamin (DA) és a szerotonin (5HT) lehetséges szabályozó szerepét vizsgáltuk a csigák táplálkozásában HPLC méréseket, intracelluláris elvezetést és komplex neuroanatómiai módszereket alkalmazva. A HPLC mérések azt mutatják, hogy külső kulcs-ingerek, amik képesek megemelni az inaktív éheztetett állat központi arousalját és beindítani de nem fenntartani a ciklikus táplálkozási mozgásokat, csökkentik a CNS DA és 5HT szintjeit. Ezzel szemben a külső és belső táplálékingerek képesek fenntartani a táplálkozási mozgások generálását és ezzel párhuzamosan növelik a CNS DA és 5HT szintjét. Helix táplálkozási 5HTerg modulátor neuronjának (MGC) valamint a szívserkentő 5HTerg neuronjainak (RPaS) aktivitása megemelkedett mind külső mind belső táplálék ingerekre annak ellenére, hogy a CNS monoamin szintje csak belső táplálékingerre emelkedett. Míg a jóllakottság elérésekor az MGC aktivitása lecsökken addig az RPAS neuronoké fennmarad. Míg az MGC glukóz hatására csökkentette az aktivitását addig az RPAS neuronok nem, jelezve, hogy a táplálékból felszabaduló glukóz hozzájárulhat a táplálkozási arousal kialakulásához és fenntartásához. A neuroanatómiai vizsgálataink szerint a tápcsatorna különböző szakaszaiból érkező érző bemenetek a CNS különböző területein végződnek, ami azt felételezi, hogy a CNS DA és 5HT szintjei valamint az 5HTerg rendszer aktivitása az éppen aktuális bemenetektől függ. | Summary: Applying HPLC assay, intracellular recording and combined neuroanatomical methods, we studied the response of the DAergic and 5HTergic systems to food ingestion in the snail Helix pomatia and Lymnaea stagnalis. The HPLC assay of DA and 5HT shows that external key stimuli, as the humidity and food stimuli, which are able to increase the central arousal and to elicit feeding arousal in starved inactive animals, decreases the central DA and 5HT levels. The external and internal food stimuli together are able to maintain the feeding arousal and to increase the central DA and 5HT content. At satiation a new internal stimulus appears which stops food intake and decreases the central DA and 5HT content. Intracellular recordings from the 5HTergic feeding modulator neurons (MGC) and the heart exciter 5HTergic neurons (RPAS) show that they increase their firing frequency not only to internal but external key stimuli when the central monoamine levels decreased. Glucose inhibited the firing frequency of the feeding modulator MGC but not of RPAS neurons indicating that the circulating glucose can regulate the maintenance of feeding arousal. The neuroanatomical studies show that sensory inputs from the different segments of the alimentary canal terminate in the different areas of the CNS, therefore we suggest that the central monoamine levels and the activity of 5HTergic system is regulated by the actual sensory inputs from the different segments of the alimentary canal

A Comprehensive Review of the Simulation Methods for Analysis at the Pore-scale

Fluid flow through porous material is relevant in different fields of engineering, such as in engine and vehicle development, and can be supported through CFD simulation. Numerical simulations at the pore-scale can be used to replace or reduce expensive laboratory measurements. These methods offer a valuable opportunity to connect the pore-scale properties of the porous material with displacement processes on the continuum-scale. Furthermore, they allow researchers to specify crucial flow properties, e.g., capillary pressure, which are crucial for REV-scale research. Three main methods, direct numerical, pore network modeling, and hybrid approaches, are widely used in order to analyze the pore-scale mechanics of fluid flow behavior through porous materials with CFD simulations. The present comprehensive review demonstrates and highlights the significant advantages, disadvantages, and critical challenges in the pore-scale fluid flow simulations. The main challenges include the characterization of material properties, and up-scaling process from pore to continuum or field-scale

Thermal Examination of a Simplified Exhaust Tube-Heatshield Model

Exhaust system and its surrounding is a thermally highly critical part of a vehicle: during forced operation, hottest elements can reach 600 °C. The thermal conditions turn to even more critical if the forced flow leaves off – e.g. when the car stops at a highway parking place. In such a case not only the cooling effect of cross-flow disappears, but the natural convection starts to bring heat toward nearby elements – resulting potential overheating of concerned parts. A measurement setup for modelling such case was built, and different parameters were examined, which have influence on the heating of aluminium heatshield above the exhaust tube. Measurements were complemented by CFD simulations and flow visualization technique aiming the better understanding of evolving thermal and flow conditions