| 1. |
- Anchordoqui, Luis A., et al.
(författare)
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The Forward Physics Facility : Sites, experiments, and physics potential
- 2022
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Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 968, s. 1-50
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Tidskriftsartikel (refereegranskat)abstract
- The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.
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| 2. |
- Dembinski, Henrik, 1980-, et al.
(författare)
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An Experimental Study of the Influence of Variable In-Cylinder Flow, Caused by Active Valve Train, on Combustion and Emissions in a Diesel Engine at Low Lambda Operation
- 2011
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : Society of Automotive Engineers of Japan, Inc.. - 0148-7191. ; , s. 2011-01-1830-
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Konferensbidrag (refereegranskat)abstract
- Spray and mixture formation in a compression ignition engine is of paramount importance for diesel combustion. In engine transient operation, when the load increases rapidly, the combustion system needs to handle low lambda (λ) operation while avoiding high particle emissions. Single cylinder tests were performed to evaluate the effect of differences in cylinder flow on combustion and emissions at typical low λ transient operation. The tests were performed on a heavy duty single cylinder test engine with Lotus Active Valve Train (AVT) controlling the inlet airflow. The required swirl number (SN) and tumble were controlled by applying different inlet valve profiles and opening either both inlet valves or only one or the other. The operating point of interest was extracted from engine transient conditions before the boost pressure was increased and investigated further at steady state conditions. The AVT enabled the resulting SN to be controlled at bottom dead centre (BDC) from ~0.3 to 6.8 and tumble from ~0.5 to 4. The fuel injection pressure was varied from 500 bar up to 2000 bar, with increments of 500 bar, for each SN and tumble setting. No exhaust gas recirculation was used in following tests. GT-POWER was used to calculate SN, tumble, and turbulent intensity with the different valve settings. The input data for the GT-POWER flow calculations were measured in a steady-state flow rig with honeycomb torque measurement.The main conclusion of this study was that the air flow structure in the cylinder, characterized by SN, tumble, and turbulent intensity, has a significant effect on the resulting engine combustion and emissions for the investigated range of fuel injection pressures. By increasing SN above 3, while maintaining tumble at low levels, the engine could be run with richer air/fuel mixtures without further increasing smoke emissions at injection pressures 1000 bar and above. Also, NOxemissions decreased at λ below 1.3; ignition delay time decreased at higher tumble and turbulent levels; and higher levels of swirl resulted in more rapid combustion, decreasing smoke emissions at injection pressures over 1000 bar. Smoke emissions increase at higher engine speeds (above 1200 rpm) and high SN (above 6). The results of this study demonstrate that the mixing process controlled by in-cylinder flow (swirl and tumble) has a dominant effect on combustion.
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| 3. |
- Dembinski, Henrik, 1980-
(författare)
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Flow measurements using combustion image velocimetry in diesel engines
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work shows the in-cylinder airflow, and its effects on combustion and emissions, in a modern, heavy-duty diesel engine. The in-cylinder airflow is examined experimentally in an optical engine and the flow field inside the cylinder is quantified and shown during combustion, crank angle resolved. Cross-correlation on combustion pictures, with its natural light from black body radiation, has been done to calculate the vector field during the injection and after-oxidation period. In this work, this technique is called combustion image velocimetry (CIV). The quantified in-cylinder flow is compared with simulated data, calculated using the GT-POWER 1-D simulation tool, and combined with single-cylinder emission measurements at various in-cylinder airflows. The airflow in the single cylinder, characterised by swirl, tumble and turbulent intensity, was varied by using an active valve train (AVT), which allowed change in airflow during the engine’s operation. The same operation points were examined in the single-cylinder engine, optical engine and simulated in GT-POWER.This work has shown that the in-cylinder airflow has a great impact on emissions and combustion in diesel engines, even at injection pressures up to 2,500 bar, with or without EGR and load up to 20-bar IMEP. Swirl is the strongest player to reduce soot emissions. Tumble has been shown to affect soot emissions negatively in combination with swirl. Tumble seems to offset the swirl centre and the offset is observed also after combustion in the optical engine tests. Injection pressure affects the swirl at late crank angle degrees during the after-oxidation part of the combustion. Higher injection pressure gives a higher measured swirl. This increase is thought to be created by the fuel spray flow interaction. The angular velocity in the centre of the piston bowl is significantly higher compared with the velocity in the outer region of the bowl. Higher injection pressure gives larger difference of the angular velocity.Calculated swirl number from the CIV technique has also been compared with other calculation methods, GT-POWER and CFD-based method. The result from the CIV technique are in line with the other methods. CFD-based calculations, according to [62], has the best fit to the CIV method. The GT-POWER calculations shows the same trend at low swirl number, but at high swirl number the two methods differs significantly.
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| 4. |
- Dembinski, Henrik, 1980-
(författare)
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In-cylinder Flow Characterisation of Heavy Duty Diesel Engines Using Combustion Image Velocimetry
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In-cylinder flow in diesel engines has a large impact on combustion and emission formation. In this work, the flow is characterised with a new measurement method called combustion image velocimetry (CIV). This technique is used to explain how airflow introduced during induction affects soot emissions and interacts with injection pressures up to 2500 bar. The CIV measurements enable flow analysis during the combustion and post-oxidation phases. The flow velocities inside the cylinder of a heavy duty optical engine, was measured with a crank angle (CA) resolution of 0.17° at injection pressures of 200–2500 bar and up to nearly full load (20 bar indicated mean effective pressure (IMEP)), were investigated with this method. The flow field results were combined with optical flame temperature and soot measurements, calculated according to Planck’s black body radiation theory.At the high injection pressures typical of today’s production standard engines and with rotational in-cylinder flow about the cylinder axis, large deviations from solid-body rotational flow were observed during combustion and post-oxidation. The rotational flow, called swirl, was varied between swirl number (SN) 0.4 and 6.7. The deviation from solid-body rotational flow, which normally is an assumption made in swirling combustion systems, formed much higher angular rotational velocities of the air in the central region of the piston bowl than in the outer part of the bowl. This deviation has been shown to be a source for turbulent kinetic energy production, which has the possibility to influence soot burn-out during the post-oxidation period.The measured CIV data was compared to Reynolds-averaged Navier–Stokes (RANS) CFD simulations, and the two methods produced similar results for the flow behaviour. This thesis describes the CIV method, which is closely related to particle image velocimetry (PIV). It was found in this work that the spatial plane in the cylinder evaluated with CIV corresponds to a mean depth of 3 mm from the piston bowl surface into the combustion chamber during combustion. During the post-oxidation phase of combustion, the measured spatial plane corresponds to a mean value of the total depth of the cylinder. The large bulk flow that contributes to the soot oxidation is thereby captured with the method and can successfully be analysed. The link between changes in in-cylinder flow and emissions is examined in this work.
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| 5. |
- Dembinski, Henrik, 1980-, et al.
(författare)
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In-Cylinder Flow Pattern Evaluated with Combustion Image Velocimetry, CIV, and CFD Calculations during Combustion and Post-Oxidation in a HD Diesel Engine
- 2013
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Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In-cylinder flow pattern was evaluated during diesel combustion and post-oxidation in a heavy duty optical engine and compared with CFD calculations. In this work the recently developed optical method combustion image velocimetry (CIV) is evaluated. It was used for extracting the flow pattern during combustion and post-oxidation by tracing the glowing soot clouds in the cylinder. The results were compared with CFD sector simulation on the same heavy duty engine geometry. Load was 10 bar IMEP and injection pressure was varied in two steps together with two different swirl levels. The same variations were done in both the optical engine and in the CFD simulations.The main results in this work show that the CIV method and the CFD results catch the same flow pattern trends during combustion and post-oxidation. Evaluation of the CIV technique has been done on large scale swirl vortices and compared with the CFD results at different distances from the piston bowl surface. The flow field according to CIV is shown to resemble the flow quite near the optical piston bowl surface during the diffusion combustion period in the CFD results. During the after-oxidation period, the observed CIV data coincide with mean velocity data from CFD, calculated on the total depth from cylinder head to piston surface. Both methods indicate that the in-cylinder flow is strongly deviating from solid body rotation during the diffusion flame and after-oxidation period. This deviation is not so significant before injection. During the after-oxidation period, the deviation from solid body rotation increases with injection pressure.
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| 6. |
- Dembinski, Henrik, 1980-, et al.
(författare)
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Optical study of swirl during combustion in a CI engine with different injection pressures and swirl ratios compared with calculations
- 2012
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Ingår i: SAE Technical Papers. - Detroit : Society of Automotive Engineers. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- Spray and mixture formation in a compression-ignition engine is of paramount importance in the diesel combustion process. In an ngine transient, when the load increases rapidly, the combustion system needs to handle low operation without producing high NO x emissions and large amounts of particulate matter. By changing the in-cylinder flow, the emissions and engine efficiency are affected.Optical engine studies were therefore performed on a heavy-duty engine geometry at different fuel injection pressures and inlet airflow characteristics. By applying different inlet port designs and valve seat masking, swirl and tumble were varied. In the engine tests, swirl number was varied from 2.3 to 6.3 and the injection pressure from 500 to 2500 bar. To measure the in-cylinder flow around TDC, particle image velocimetry software was used to evaluate combustion pictures. The pictures were taken in an optical engine using a digital high-speed camera. Clouds of glowing soot particles were captured by the camera and traced with particle image velocimetry software. The velocity-vector field from the pictures was thereby extracted and a mean swirl number was calculated. The swirl number was then compared with 1D simulation program GT-POWER and CFD based correlations. The GT-POWER simulations and CFD based correlation calculations were initiated from steady-state flow bench data on tested cylinder heads.The main conclusions from this study were that the mean swirl numbers, evaluated with the PIV software from combustion pictures around TDC, agreed with CFD based correlations and the low swirl numbers also correlated with the 1D-simulation program. Most of the induced swirl motion survives the compression and combustion, while the induced tumble does not survive to the late combustion phase. The tumble however, disturbs the swirl motion and offsets the swirl centre. This offset survives the compression and combustion. The diesel sprays that are injected symmetrically in the combustion chamber are thereby exposed to the swirl asymmetrically. This study also shows that the angular velocity at different piston bowl radii deviates from solid body rotation. The angular velocity is higher closer to the centre and decreases to be at the lowest value at the outer piston bowl edge. When the injection pressure is increased, the deviation from solid body rotation increases due to spray effects.
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| 7. |
- Dembinski, Henrik, 1980-, et al.
(författare)
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Swirl and Injection Pressure Effect on Post-Oxidation Flow Pattern Evaluated with Combustion Image Velocimetry, CIV, and CFD Simulation
- 2013
-
Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
-
Konferensbidrag (refereegranskat)abstract
- In-cylinder flow pattern has been examined experimentally in a heavy duty optical diesel engine and simulated with CFD code during the combustion and the post-oxidation phase. Mean swirling velocity field and its evolution were extracted from optical tests with combustion image velocimetry (CIV). It is known that the post-oxidation period has great impact on the soot emissions. Lately it has been shown in swirling combustion systems with high injection pressures, that the remaining swirling vortex in the post-oxidation phase deviates strongly from solid body rotation. Solid body rotation can only be assumed to be the case before fuel injection. In the studied cases the tangential velocity is higher in the centre of the piston bowl compared to the outer region of the bowl. The used CIV method is closely related to the PIV technique, but makes it possible to extract flow pattern during combustion at full load in an optical diesel engine. Injection pressure was varied from 200 up to 2500 bar at 1000 rpm without EGR. Swirl was varied between 1.2 and 6.4 at BDC. The CFD simulation was a sector simulation on the same in-cylinder geometry and boundary conditions as in the optical engine.The main findings show that with increased injection pressure, together with swirl, the angular velocity increases in the centre of the piston bowl meanwhile the angular velocity decreases slightly in the outer region. The total angular momentum decreases slightly when injection starts and the total rotational kinetic energy increases significantly. The redistribution of the angular velocity is caused by the driving force from the injection. When the swirling bulk flow acts on the injected spray/flame, its orbit is slightly directed to the leeward side of the swirl. When the flame is directed back to the cylinder centre, by the bowl, it has thereby an offset from where it is injected. This offset together with the high flow velocity from the flame increases the angular velocity in the central region of the combustion chamber. The angular velocity in the outer part of the bowl decreases slightly when angular momentum is moved into the centre of the bowl were the velocity increases. This deviation in angular velocity has been observed in both the CFD results and in the CIV results were it survives into the post-oxidation phase with slow dissipation during the expansion stroke. The dissipation is a source for late cycle turbulence generation that affects the soot oxidation.
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| 8. |
- Dembinski, H., et al.
(författare)
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Swirl and injection pressure impact on after-oxidation in diesel combustion, examined with simultaneous combustion image velocimetry and two colour optical method
- 2013
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : S A E Inc. ; , s. 2013-01-0913-
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Konferensbidrag (refereegranskat)abstract
- After-oxidation in Heavy Duty (HD) diesel combustion is of paramount importance for emissions out from the engine. During diffusion diesel combustion, lots of particulate matter (PM) is created. Most of the PM are combusted during the after-oxidation part of the combustion. Still some of the PM is not, especially during an engine transient at low lambda. To enhance the PM oxidation in the late engine cycle, swirl together with high injection pressure can be implemented to increase in-cylinder turbulence at different stages in the cycle. Historically swirl is known to reduce soot particulates. It has also been shown, that with today's high injection pressures, can be combined with swirl to reduce PM at an, for example, engine transient. The mechanism why the PM engine out is reduced also at high injection pressures is however not so well understood. In this work flow field data during combustion and after-oxidation together with soot and temperature measurements was combined to examine how flow field affects soot formation and oxidation. Swirl number was varied together with injection pressure and the engine tests were done in a HD optical engine. The load was set to 10 bar & 20 bar IMEP at low lambda without EGR, typically transient load points. A high speed colour camera captures picture of the combustion seen through a glass piston-bowl. The flow field was extracted with combustion image velocimetry (CIV) that traces the glowing soot particulates (or the light luminosity difference) by cross correlation between two pictures from the high speed colour camera. From the same pictures the KL factor and flame temperature were simultaneously calculated with the 2-colour method. Both CIV and the 2-colour method are line of sight optical methods that catches flow, soot and temperature from the light observed through the piston. It was found that in the after-oxidation part of the cycle, the flow in the piston bowl deviates strongly from solid body rotation (that can be assumed to be the case before injection). With increased injection pressure this deviation from solid body rotation increased at constant swirl number. When swirl number was increased, the deviation from solid body rotation increased even further. This seems to be an important factor during the after-oxidation part of the combustion by amplifying the turbulence. The flame temperature together with KL factor (a measure of soot density inside the cylinder) was also influenced when the flow field in the cylinder was changed. With increased injection pressure, from 500 bar to 1000 bar, the maximum KL was amplified during combustion with 50%, but the measured tail pipe soot was decreasing from 1.22 FSN to 0.49 FSN. This together with increased solid body deviation for the 1000 bar case, at the after-oxidation part of the combustion, leads to the conclusion: The flow field during the late part of the cycle has strong impact on tail pipe soot emissions. What was created during the diffusion combustion has less impact on the tail pipe soot compared to the flow field effects during after-oxidation.
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| 9. |
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| 10. |
- Königsson, Fredrik, et al.
(författare)
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The Influence of In-Cylinder Flows on Emissions and Heat Transfer from Methane-Diesel Dual Fuel Combustion
- 2013
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- In order for premixed methane diesel dual fuel engines to meet current and future legislation, the emissions of unburned hydrocarbons must be reduced while high efficiency and high methane utilization is maintained. This paper presents an experimental investigation into the effects of in cylinder air motion, swirl and tumble, on the emissions, heat transfer and combustion characteristics of dual fuel combustion at different air excess ratios. Measurements have been carried out on a single cylinder engine equipped with a fully variable valve train, Lotus AVT. By applying different valve lift profiles for the intake valves, the swirl was varied between 0.5 and 6.5 at BDC and the tumble between 0.5 and 4 at BDC. A commercial 1D engine simulation tool was used to calculate swirl number and tumble for the different valve profiles. Input data for the simulation software was generated using a steady-state flow rig with honeycomb torque measurements. To measure heat transfer, thermocouples were fitted in the cylinder head and heat exchangers on the coolant circuit and the engine oil. The study shows that swirl has a strong effect on the heat transfer; increasing the swirl from 0.5 to 6.5 increases the heat transfer to the coolant by 50%. With regards to emissions; swirl has the effect of increasing oxidation of hydrocarbons returning from crevices. For this reason a 20% reduction of hydrocarbon emissions can be achieved by increasing the swirl from 0.4 to 3. At high λ of 1.9, combustion is very sensitive to mixing between the gas and the air. The mixing is affected by the turbulence generated over the intake valves. A difference in engine out HC emissions by a factor of two can be achieved by varying the valve lift curve and hence varying the turbulence generated during the intake event. The timing of the gas injection can also improve mixing and achieve similar results. Compared to SI, dual fuel combustion is relatively insensitive to tumble.
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