119 research outputs found
Two-stage Fuel Direct Injection in a Diesel Fuelled HCCI Engine
No full textTwo-stage fuel direct injection (DI) has the potential to expand the operating region and control the autoignition timing in a Diesel fuelled homogeneous charge compression ignition (HCCI) engine. In this work, to investigate the dual-injection HCCI combustion, a stochastic reactor model, based on a probability density function (PDF) approach, is utilized. A new wall-impingement sub-model is incorporated into the stochastic spray model for direct injection. The model is then validated against measurements for combustion parameters and emissions carried out on a four stroke HCCI engine. The initial results of our numerical simulation reveal that the two-stage injection is capable of triggering the charge ignition on account of locally rich fuel parcels under certain operating conditions, and consequently extending the HCCI operating range. Furthermore, both simulated and experimental results on the effect of second injection timing on combustion indicate that there exists an optimal second injection timing to gain maximum engine output work for a given fuel split ratio.기계공학전
Studying the Influence of Direct Injection on PCCI Combustion and Emissions at Engine Idle Condition Using Two Dimensional CFD and Stochastic Reactor Model
No full textThis work has been partially funded by Aramco Overseas Company B.V., contract number 6600014846, and by the EPSRC (Engineering and Physical Sciences Research Council), UK, grant number EP/D068703/1
Is Hippopotamus antiquus (Mammalia, Hippopotamidae) affected by body size variations? The contribution of the Mosbach (Germany, Middle Pleistocene) specimen
No full textFunding Information:
Open access funding provided by FCT|FCCN (b-on). RM is granted by the Fundação para a Ciência e a Tecnologia (FCT) [2021.08458.BD] and SYNTHESYS + [DE-TAF-TA4 - 063 2022]. This research was also supported FCT, I.P through the Research Unit UIDB/04035/2020 (https://doi.org/10.54499/UIDB/04035/2020). This work is part of the project P2022RZ4PL funded by the European Union—Next Generation EU, call PRIN 2022 PNRR (granted to LP). MR thanks the Stimulus of Scientific Employment, Individual Support–2018 Call grant by the Fundação para a Ciência e a Tecnologia (Portugal, CEECIND/02199/2018) and GeoBioTec.
Publisher Copyright:
© The Author(s) 2025.Hippopotamus antiquus is a well-documented species within the Hippopotamidae family, with evidence of its presence in almost all Europe during the Pleistocene. Despite its abundance in the fossiliferous record, there is still much debate surrounding the first and last appearance data of this taxon, as well as its evolutionary trend. In this work we present a well-preserved mandible recovered from Mosbach (Germany) referred to the Middle Pleistocene. The latter period is represented by less H. antiquus remains in comparison to the Early Pleistocene, making the description of this specimen helpful for morphometric and morphological considerations. Early Pleistocene H. antiquus specimens from Upper Valdarno, Collecurti and Durfort display larger dimensions in comparison to those from Middle Pleistocene localities, including Maglianella, Ortona, Ponte Molle and the specimen from Mosbach. A decrease in body size in H. antiquus, most likely correlated to climate fluctuations, is therefore discussed providing news insights into the biogeography, morphology and morphometry of late H. antiquus.publishersversioninpres
Several Lower Palaeolithic Sites along the Rhine Rift Valley, Dated from 1.3 to 0.6 Million Years
No full textThe important discoveries of Lower Palaeolithic artefacts in stratigraphical context within Lower and early Middle Pleistocene deposits in the western continental part of Europe along the rift systeme of the Rhine Valley are pointing at the possible continuous presence of hominins since the Lower Pleistocene. This paper reports on lithic industry from its early appearance at around 1.3 million years (Ma) at the site of Münster-Sarmsheim to the latest pre-Elsterian period at around 0.6 Ma at Mauer, Mosbach, and Miesenheim
The future of computational modelling in reaction engineering
No full textIn this paper, we outline the future of modelling in reaction engineering. Specifically, we use the example of particulate emission formation in internal combustion engines to demonstrate what modelling can achieve at present, and to illustrate the ultimately inevitable steps that need to be taken in order to create a new generation of engineering models.</jats:p
A systematic method to estimate and validate enthalpies of formation using error-cancelling balanced reactions
No full textThe Combustion Institute This paper presents an automated framework that uses overlapping subsets of reference data to systematically derive an informed estimate of the standard enthalpy of formation of chemical species and assess the consistency of the reference data. The theory of error-cancelling balanced reactions (EBRs) is used to calculate estimates of the standard enthalpy of formation. Individual EBRs are identified using linear programming. The first part of the framework recursively identifies multiple EBRs for specified target species. A distribution of estimates can then be determined for each species from which an informed estimate of the enthalpy is derived. The second part of the framework iteratively isolates inconsistent reference data and improves the prediction accuracy by excluding such data. The application of the framework is demonstrated for test cases from organic and inorganic chemistry, including transition metal complexes. Its application to a set of 920 carbon, hydrogen and oxygen containing species resulted in a rapid decrease of the mean absolute error for estimates of the enthalpy of formation of each species due to the identification and exclusion of inconsistent reference data. Its application to titanium-containing species identified that the available reference values of TiOCl and TiO(OH) 2 are inconsistent and need further attention. Revised values are calculated for both species. A comparison with popular high-level quantum chemistry methods shows that the framework is able to use affordable density functional theory (DFT) calculations to deliver highly accurate estimates of the standard enthalpy of formation, comparable to high-level quantum chemistry methods for both hydrocarbons and transition metal complexes
A quantitative probabilistic investigation into the accumulation of rounding errors in numerical ODE solution.
No full textWe examine numerical rounding errors of some deterministic solvers for systems of ordinary differential equations (ODEs) from a probabilistic viewpoint. We show that the accumulation of rounding errors results in a solution which is inherently random and we obtain the theoretical distribution of the trajectory as a function of time, the step size and the numerical precision of the computer. We consider, in particular, systems which amplify the effect of the rounding errors so that over long time periods the solutions exhibit divergent behaviour. By performing multiple repetitions with different values of the time step size, we observe numerically the random distributions predicted theoretically. We mainly focus on the explicit Euler and fourth order Runge–Kutta methods but also briefly consider more complex algorithms such as the implicit solvers VODE and RADAU5 in order to demonstrate that the observed effects are not specific to a particular method
HCCI Combustion Phasing Transient Control by Hydrogen-Rich Gas: Investigation Using a Fast Detailed-Chemistry Full-Cycle Model
No full textHCCI Combustion Control Using Dual-Fuel Approach: Experimental and Modeling Investigations
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