CFD Modeling of an Alcohol-Diesel Direct-Injection Dual-Liquid-Fuel Engine using OpenFOAM

Legislation for heavy duty combustion engines are becoming more stringent. To keep up with the legislation, new engine technology is required. Furthermore, renewable\ua0fuels can also be used together with new engine technology to further reduce emissions.Computational techniques such as Computational Fluid Dynamics (CFD) provides a powerful and cost effective alternative/complement to traditional engine tests when developing new engine technology. To effectively use CFD for engine development, accurate models for spray formation and chemistry are required. In this work a new direct-injection dual-liquid-fuel engine concept using methanol and diesel was investigated using CFD. The first part of this thesis involved validation and development of our in-house spray model, VSB2. The VSB2 is a Eulerian-Lagrangian model with a minimal amount of tuning parameter. It models the impact of secondary breakup by including a distribution of droplet sizes inside each computational blob. The model was first validated for use with alcohol fuels, where the turbulence parameters were also tuned together with experimental data for later use in enginesimulations. It was shown that the VSB2 spray model could accurately predict the spray formation of an alcohol spray.Furthermore, the spray model was developed further by implementing a new break up treatment that addressed some conceptual flaws in how the model handles the momentum of a computational blob with different droplet sizes. Previously, each computational blob contained the momentum of all droplet sizes, which had the consequence that smaller droplets would have the same momentum as larger droplets. This was addressed by creating child blobs from the stable droplet sizes. It was shown that this had the effect of enhancing the evaporation and dispersion at lower ambient gas temperatures.The last part of this thesis was to create a CFD model in OpenFOAM that could model a direct-injection dual-liquid-fuel engine. A tabulated chemistry solver based on the well stirred reactor approach called LOGE-CPV was used to model the chemistry. It was shown that the model could accurately predict global parameters such as in cylinder pressure and rate of heat release of the system, but pollutant formation was predicted poorly when compared to experiments. It was concluded that a turbulent combustion model would be needed to accurately predict pollutant formation. The ignition process was also studied, showing that the pilot diesel could easily ignite the methanol as long as the pilot flame would reach the center of the combustion chamber. It was also shown that further offsetting the pilot injector caused the combustion to become unstable as it was difficult to ignite allthe sprays from the main injector

Improving sample efficiency and multi-agent communication in RL-based train rescheduling

We present preliminary results from our sixth placed entry to the Flatland international competition for train rescheduling, including two improvements for optimized reinforcement learning (RL) training efficiency, and two hypotheses with respect to the prospect of deep RL for complex real-world control tasks: first, that current state of the art policy gradient methods seem inappropriate in the domain of high-consequence environments; second, that learning explicit communication actions (an emerging machine-to-machine language, so to speak) might offer a remedy. These hypotheses need to be confirmed by future work. If confirmed, they hold promises with respect to optimizing highly efficient logistics ecosystems like the Swiss Federal Railways railway network

Modeling of Spray Formation and Development in OpenFOAM with Application to Diesel and Alcohol Fuels

Legislation with reagards to fuel emissions are becoming more stringent. This creates a need for improved engine concepts and fuels. This work is part of an ongoin project to create a concept for a direct injection dual fuel engine, which uses alcohol as main fuel and diesel as a pilot. The work in this thesis is part of the task to create a CFD model for this engine that can be used for improving the current engine concept.The first part of this project has been to validate the in-house spray model, VSB2 for usage with alcohol fuels. This was done by comparing simululations made in OpenFOAM with experimental data obtained from the Chalmers HT/HP spray chamber. The simulations showed that the model could capture spray penetration at the simulation conditions accurately. It was also concluded that it was neccessary to fix the turbulent length scale in the injector cell to get an accurate prediction of the liquid penetration.The second part of this project has been to improve upon the spray model. This has been done by extending the spray break up treament inside VSB2. The model was extended by implenting a mechanism for removing the stable droplets inside each blob and using these to create child parcels, containing only stable droplets. It was shown that this improves the prediction of liquid penetration, especially at lower temperatures. The Third part of this project, that is still undergoing is to do CFD simulations of a direct injection dual fuel engine. Some preliminary results are shown in this work that show good agreement in the pressure trace. The sprays also ignites in a way that is expected, with the sprays closest to the pilot igniting first. There is still some uncertainty in the results, and further studies and development are needed to produce good results

Alcohol flexible HD single cylinder diesel engine tests with separate dual high pressure direct fuel injection

Both greenhouse gas (GHG) emissions and local emissions from heavy duty (HD) Diesel engines must be greatly reduced to make transportation sustainable and comply with increasingly stringent emissions regulations. The fuel flexible engine concept for HD Diesel engines uses a dual fuel direct injection system in which ignition of the main alcohol fuel, either methanol or ethanol, is induced by a small Diesel pilot injection delivered via a separate direct injector. The objective of this investigation was to find ways to combine the advantages of conventional Diesel engines with the advantages of low carbon fuels and to thereby bypass the soot-NOx-trade-off. Experiments were conducted using a modified single-cylinder HD engine and three fuels (methanol, ethanol, and a reference Diesel fuel) to determine how the choice of fuel affected the engine\u27s combustion behaviour, emissions and fuel efficiency. Injection pressures on the alcohol side were varied up to 1500 bar and the investigation was carried out at low, medium and high speed-load points. The alcohol fuels significantly outperformed Diesel fuel under all tested conditions (with and without exhaust gas recirculation (EGR)). Indicated thermal efficiency was increased by up to 3.5%-points and simultaneously soot emissions were lowered by a factor of 40 or more and NOx by 20%. Combustion stability and emissions were in the same range as for Diesel but replacing more than 95 % of the fossil Diesel with an alcohol fuel

Use of 3D-printed mixers in laboratory reactor design for modelling of heterogeneous catalytic converters

A method for identifying radial concentration maldistribution in synthetic catalyst activity test (SCAT) benches, is presented, where spatially resolved concentration measurements are not available. The developed methodology was successfully tested for an injection-based SCAT. To resolve the radial concentration maldistribution a static mixer was designed, 3D-printed and inserted upstream the test sample. The methodology could also prove the effectiveness of the mixer, which did not only resolve the concentration maldistribution but also avoided causing reaction disturbances. The resulting increased axial dispersion from the turbulence created by the static mixer was evaluated using a 3D CFD model in Ansys Fluent 19. The axial dispersion of the injection-based SCAT bench was compared to a premixed SCAT bench through classical Aris-Taylor calculations. The results from the axial dispersion calculations show that the injection-based design with the use of a static mixer is far superior to the premixed design – both with regards to pulse broadening but also time delay. This is highly desirable for modelling studies towards zero emission exhaust aftertreatment

Elevated [11C]-D-Deprenyl Uptake in Chronic Whiplash Associated Disorder Suggests Persistent Musculoskeletal Inflammation

There are few diagnostic tools for chronic musculoskeletal pain as structural imaging methods seldom reveal pathological alterations. This is especially true for Whiplash Associated Disorder, for which physical signs of persistent injuries to the neck have yet to be established. Here, we sought to visualize inflammatory processes in the neck region by means Positron Emission Tomography using the tracer 11C-D-deprenyl, a potential marker for inflammation. Twenty-two patients with enduring pain after a rear impact car accident (Whiplash Associated Disorder grade II) and 14 healthy controls were investigated. Patients displayed significantly elevated tracer uptake in the neck, particularly in regions around the spineous process of the second cervical vertebra. This suggests that whiplash patients have signs of local persistent peripheral tissue inflammation, which may potentially serve as a diagnostic biomarker. The present investigation demonstrates that painful processes in the periphery can be objectively visualized and quantified with PET and that 11C-D-deprenyl is a promising tracer for these purposes

Prognostic Value of Three Different Methods of MGMT Promoter Methylation Analysis in a Prospective Trial on Newly Diagnosed Glioblastoma

Hypermethylation in the promoter region of the MGMT gene encoding the DNA repair protein O6-methylguanine-DNA methyltransferase is among the most important prognostic factors for patients with glioblastoma and predicts response to treatment with alkylating agents like temozolomide. Hence, the MGMT status is widely determined in most clinical trials and frequently requested in routine diagnostics of glioblastoma. Since various different techniques are available for MGMT promoter methylation analysis, a generally accepted consensus as to the most suitable diagnostic method remains an unmet need. Here, we assessed methylation-specific polymerase chain reaction (MSP) as a qualitative and semi-quantitative method, pyrosequencing (PSQ) as a quantitative method, and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) as a semi-quantitative method in a series of 35 formalin-fixed, paraffin-embedded glioblastoma tissues derived from patients treated in a prospective clinical phase II trial that tested up-front chemoradiotherapy with dose-intensified temozolomide (UKT-05). Our goal was to determine which of these three diagnostic methods provides the most accurate prediction of progression-free survival (PFS). The MGMT promoter methylation status was assessable by each method in almost all cases (n = 33/35 for MSP; n = 35/35 for PSQ; n = 34/35 for MS-MLPA). We were able to calculate significant cut-points for the continuous methylation signals at each CpG site analysed by PSQ (range, 11.5 to 44.9%) and at one CpG site assessed by MS-MLPA (3.6%) indicating that a dichotomisation of continuous methylation data as a prerequisite for comparative survival analyses is feasible. Our results show that, unlike MS-MLPA, MSP and PSQ provide a significant improvement of predicting PFS compared with established clinical prognostic factors alone (likelihood ratio tests: p<0.001). Conclusively, taking into consideration prognostic value, cost effectiveness and ease of use, we recommend pyrosequencing for analyses of MGMT promoter methylation in high-throughput settings and MSP for clinical routine diagnostics with low sample numbers

Epigenetic regulation of CD44 in Hodgkin and non-Hodgkin lymphoma

<p>Abstract</p> <p>Background</p> <p>Epigenetic inactivation of tumor suppressor genes (TSG) by promoter CpG island hypermethylation is a hallmark of cancer. To assay its extent in human lymphoma, methylation of 24 TSG was analyzed in lymphoma-derived cell lines as well as in patient samples.</p> <p>Methods</p> <p>We screened for TSG methylation using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) in 40 lymphoma-derived cell lines representing anaplastic large cell lymphoma, Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), Hodgkin lymphoma and mantle cell lymphoma (MCL) as well as in 50 primary lymphoma samples. The methylation status of differentially methylated <it>CD44 </it>was verified by methylation-specific PCR and bisulfite sequencing. Gene expression of <it>CD44 </it>and its reactivation by DNA demethylation was determined by quantitative real-time PCR and on the protein level by flow cytometry. Induction of apoptosis by anti-CD44 antibody was analyzed by annexin-V/PI staining and flow cytometry.</p> <p>Results</p> <p>On average 8 ± 2.8 of 24 TSG were methylated per lymphoma cell line and 2.4 ± 2 of 24 TSG in primary lymphomas, whereas 0/24 TSG were methylated in tonsils and blood mononuclear cells from healthy donors. Notably, we identified that <it>CD44 </it>was hypermethylated and transcriptionally silenced in all BL and most FL and DLBCL cell lines, but was usually unmethylated and expressed in MCL cell lines. Concordant results were obtained from primary lymphoma material: <it>CD44 </it>was not methylated in MCL patients (0/11) whereas <it>CD44 </it>was frequently hypermethylated in BL patients (18/29). In cell lines with <it>CD44 </it>hypermethylation, expression was re-inducible at mRNA and protein levels by treatment with the DNA demethylating agent 5-Aza-2'-deoxycytidine, confirming epigenetic regulation of <it>CD44</it>. CD44 ligation assays with a monoclonal anti-CD44 antibody showed that CD44 can mediate apoptosis in CD44⁺lymphoma cells. <it>CD44 </it>hypermethylated, CD44^-lymphoma cell lines were consistently resistant towards anti-CD44 induced apoptosis.</p> <p>Conclusion</p> <p>Our data show that <it>CD44 </it>is epigenetically regulated in lymphoma and undergoes <it>de novo </it>methylation in distinct lymphoma subtypes like BL. Thus <it>CD44 </it>may be a promising new epigenetic marker for diagnosis and a potential therapeutic target for the treatment of specific lymphoma subtypes.</p