| 1. |
- Alsved, Malin, et al.
(författare)
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Droplet, aerosol and SARS-CoV-2 emissions during singing and talking
- 2021
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Konferensbidrag (refereegranskat)abstract
- IntroductionAs the pandemic continues to spread, more knowledge is needed about the viral transmission routes. Several super spreading events during the Covid-19 pandemic have been linked to singing in choirs and talking loud. However, in the beginning of the pandemic there was only one study about emitted aerosols and droplets from singing, published in 1968, and only a handful on emissions from talking. Therefore, we conducted a study to measure the aerosol and droplet emissions from talking and singing. We also evaluated the emissions from singing when wearing a face mask.We have further developed our setup so that we collect the aerosol particles from Covid-19 infected patients that are talking and singing, and analyze our samples for SARS-CoV-2, the virus causing Covid-19.MethodTwelve healthy singers (7 professionals, 5 amateurs) were included in the first study part on quantifying the amount of emitted aerosols and droplets. The singers were singing or talking a short consonant rich text repeatedly at a constant pitch with their face in the opening of a funnel. The aerosol particle size and concentration was measured from the other end of the funnel using an aerodynamic particle sizer (APS, 3321, TSI Inc). In addition, the amount of un-evaporated droplets were captured with a high-speed camera and quantified using image analysis.During February and March 2021 we will collect aerosol particles from patients with confirmed Covid-19 that are singing and talking into a funnel. We will use a growth tube condensation collector, a BioSpot (Aerosol Devices), operating at 8 L min-1, and a NIOSH BC-251 cyclone sampler operating at 3.5 L min-1 (TISCH Environmental). The BioSpot collects the whole range of exhaled aerosol particles with high (95%) efficiency into liquid, and the NIOSH cyclone sampler collects particles into three size fractions: <1 µm (filter), 1-4 µm (liquid), >4 µm (liquid). The APS is again used to measure size and concentration of the emitted aerosol particles, so that emissions from infected test subjects can be compared with those of the healthy test subjects. Air samples will be analyzed for detection of SARS-CoV-2 genes, and if possible, SARS-CoV-2 infectivity in cell cultures.ResultsAerosol particle emissions from healthy test subjects were significantly higher during normal singing (median 690, range [320–2870] particles/s) than during normal talking (270 [120–1380] particles/s) (Wilcoxon’s signed rank test, p=0.002). Loud singing produced even more aerosol particles (980 [390–2870] particles/s) than normal singing (p=0.002). The amount of non-evaporated droplets detected by the high-speed camera setup showed similar results: more droplets during loud singing or talking. For both aerosol particle concentrations and droplet numbers, the levels were reduced by on average 70-80% when wearing a surgical face mask.ConclusionsSinging and talking give rise to high aerosol and droplet emissions from the respiratory tract. This is likely an important transmission route for Covid-19. In our upcoming part of the study we hope to determine how much SARS-CoV-2 that is emitted during these social activities.
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| 2. |
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| 3. |
- Alsved, Malin, et al.
(författare)
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Exhaled respiratory particles during singing and talking
- 2020
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 1521-7388 .- 0278-6826. ; 54:11, s. 245-1248
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Tidskriftsartikel (refereegranskat)abstract
- Choir singing has been suspended in many countriesduring the Covid-19 pandemic due to incidental reportsof disease transmission. The mode of transmission has been attributed to exhaled droplets, but with the exception of a study on tuberculosis from1968, there is presently almost no scientific evidence ofincreased particle emissions from singing. A substantial number of studies have,however, investigated aerosols emitted from breathing,talking, coughing and sneezing. It has also been shown that justnormal breathing over time can generate more viablevirus aerosol than coughing, since the latter is a less fre-quent activity.Compared to talking, singing often involves continu-ous voicing, higher sound pressure, higher frequencies,deeper breaths, higher peak airflows and more articu-lated consonants. All these factors are likely to increaseexhaled emissions.The aim of this study was to investigate aerosol anddroplet emissions during singing, as compared to talking and breathing. We also examined the presence of SARS-CoV-2 in the air from breathing, talking and singing,and the efficacy of face masks to reduce emissions. In this study we defined aerosol particles as having a drysize in the range 0.5–10mm. Although debatable from anaerosol physics point of view, a cutoff diameter between5 and 10mm is normally used in medicine for classifica-tion of aerosol versus droplet route of transmission. Droplets are here defined as exhaled particles, frommicron size with no upper size limit, and measured dir-ectly at the mouth before complete evaporation, thuspartly in liquid phase.
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| 4. |
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| 5. |
- Binder, Christian, 1988-, et al.
(författare)
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Comparison of heat losses at the impingement point and in between two impingement points in a diesel engine using phosphor thermometry
- 2019
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Ingår i: 2019 JSAE/SAE Powertrains, Fuels and Lubricants. - Kyoto, Japan : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- In-cylinder heat losses in diesel engines reduce engine efficiency significantly and account for a considerable amount of injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the impingement of the flame. The present study compares the heat losses at the point where the flame impinges onto the piston bowl wall and the heat losses between two impingement points. Measurements were performed in a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the combusting diesel spray and at a point in between two impingement points was determined using phosphor thermometry. The dynamic heat fluxes and the heat transfer coefficients which result from the surface temperature measurements are estimated. Simultaneous cylinder pressure measurements and high-speed videos are associated to individual surface temperature measurements. Thus each surface temperature measurement is linked to a specific impingement and combustion events. An analysis of the surface temperature in connection with the high speed images reveals the great impact of flame impingement on instantaneous local heat flux at the impingement point. Absence of such an effect in between two impingement points implies an inhomogeneous temperature field.
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| 6. |
- Binder, Christian, 1988-, et al.
(författare)
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Study on heat losses during flame impingement in a diesel engine using phosphor thermometry surface temperature measurements
- 2019
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Ingår i: SAE Technical Papers. - Detroit, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- In-cylinder heat losses in diesel engines decrease engine efficiency significantly and account for approximately 14-19% [1, 2, 3] of the injected fuel energy. A great part of the heat losses during diesel combustion presumably arises from the flame impingement onto the piston. Therefore, the present study investigates the heat losses during flame impingement onto the piston bowl wall experimentally. The measurements were performed on a full metal heavy-duty diesel engine with a small optical access through a removed exhaust valve. The surface temperature at the impingement point of the flame was determined by evaluating a phosphor's temperature dependent emission decay. Simultaneous cylinder pressure measurements and high-speed videos are associated to the surface temperature measurements in each cycle. Thus, surface temperature readings could be linked to specific impingement and combustion events. The results showed a sharp increase of the surface temperature during the flame impingement and an abrupt decrease as the flame disappeared.
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| 7. |
- Denny, Michael, et al.
(författare)
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Interaction between Fuel Jets and Prevailing Combustion During Closely-Coupled Injections in an Optical LD Diesel Engine
- 2019
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Ingår i: SAE Technical Paper : Automotive - Automotive. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- Two imaging techniques are used to investigate the interaction between developed combustion from earlier injections and partially oxidized fuel (POF) ofa subsequent injection. The latter is visualized by using planar laser induced fluorescence (PLIF) of formaldehyde and poly-cyclic aromatic hydrocarbons. High speed imaging captures the natural luminescence (NL) of the prevailing combustion. Three different fuel injection strategies are studied. One strategy consists of two pilot injections, with modest separations after each, followed by single main and post injections. Both of the other two strategies have threepilots followed by single main and post injections. The separations after the second and third pilots are several times shorter than in the reference case (making them closelycoupled). The closely-coupled cases have more linear heatrelease rates (HRR) which lead to much lower combustion noise levels. For all cases, POF is detected during the very weak HRR before the notable combustion of the first pilot injection’s fuel. When the subsequent fuel injections overlapwith a local decrease in HRR, the prevailing combustion is to some degree extinguished during these phases. This is seen via the NL signal being replaced by the POF signal, indicating that hotter combustion products are being replaced by cooler ones. When the NL and POF regions spatially overlap, the POF signal decreases, and there is no injection, this marks the further oxidation of the POF into hotter combustion products. This extinguishing phenomenon can, to a lesser extent than closely-coupling, affect the combustion noise by affecting the magnitude of the local dips in the HRR, which via its influence on the pressure trace, affects combustion noise.
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| 8. |
- Denny, Michael, et al.
(författare)
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Optical Investigation on the Combustion Process Differences between Double-Pilot and Closely-Coupled Triple-Pilot Injection Strategies in a LD Diesel Engine
- 2019
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Ingår i: International Powertrains, Fuels & Lubricants Meeting. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2019-January
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Konferensbidrag (refereegranskat)abstract
- The combustion processes of three injection strategies in a light-duty (LD) diesel engine at a medium load point are captured with a high speed video camera. A double-pilot/main/single-post injection strategy representative of a LD Euro 6 calibration is considered as the reference. There is a modest temporal spacing (dwell) after the first pilot (P1) and second pilot (P2). A second strategy, "A," adds a third pilot (P3). The dwell after both P2 and P3 are several times shorter than in the reference strategy. A third strategy, "B," further reduces all dwells. Each injection has its own associated local peak in the heat release rate (HRR) following some ignition delay. Between these peaks lie local minima, or dips. In all three cases, the fuel from P1 combusts as a propagating premixed flame. For all strategies, the ignition of P2 primarily occurs at its interface with the existing combustion regions. Extinguishing of the prevailing combustion by the fuel jets of later injections is noted in all strategies. This phenomenon is confirmed by comparing the timing of each fuel injection with the dips in the HRR and spatial luminescence over time. These dips after each injection are larger than would be expected by the cooling effect of the injected fuel alone. Furthermore, not all dips in the HRR are the result of this extinguishing, and it would not have been possible to determine if the dips are due to this extinguishing or a simple exhaustion of available fuel without this optical investigation. Even if the precise hydraulic injection timing can be known, knowledge of the spatial relationship of the injected fuel and prevailing combustion is necessary.
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| 9. |
- Hult, Johan, et al.
(författare)
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Optical Characterization of the Combustion Process inside a Large-Bore Dual-Fuel Two-Stroke Marine Engine by Using Multiple High-Speed Cameras
- 2020
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Ingår i: WCX SAE World Congress Experience. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2020-April
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Konferensbidrag (refereegranskat)abstract
- Dual-fuel engines for marine propulsion are gaining in importance due to operational and environmental benefits. Here the combustion in a dual-fuel marine engine operating on diesel and natural gas, is studied using a multiple high-speed camera arrangement. By recording the natural flame emission from three different directions the flame position inside the engine cylinder can be spatially mapped and tracked in time. Through space carving a rough estimate of the three-dimensional (3D) flame contour can be obtained. From this contour, properties like flame length and height, as well as ignition locations can be extracted. The multi-camera imaging is applied to a dual-fuel marine two-stroke engine, with a bore diameter of 0.5 m and a stroke of 2.2 m. Both liquid and gaseous fuels are directly injected at high pressure, using separate injection systems. Optical access is obtained using borescope inserts, resulting in a minimum disturbance to the cylinder geometry. In this type of engine, with fuel injection from positions at the rim of the cylinder, the flame morphology becomes asymmetric. The optical spatial mapping and tracking method is demonstrated to be well suited for the study of such an asymmetric combustion system. Spatial mapping and tracking of flame position is applied to both engine operating modes; normal diesel operation and dual-fuel operation with diesel pilot ignition of the gas. Similarities and differences between diesel and gas flame shape and development can thus be visualised directly. The effects of changing charge density, gas injection pressure and injection nozzle geometry on the flame geometry and development are also studied.
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| 10. |
- Hult, Johan, et al.
(författare)
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Spatiotemporal flame mapping in a large-bore marine diesel engine using multiple high-speed cameras
- 2020
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Ingår i: International Journal of Engine Research. - : SAGE Publications. - 1468-0874 .- 2041-3149. ; 21:4, s. 622-631
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Tidskriftsartikel (refereegranskat)abstract
- A calibrated multiple high-speed camera arrangement recording the flame emission from three different directions has been demonstrated on an engine. From the multiple views, the flame position inside the engine cylinder can be spatially mapped, allowing quantitative studies of the dynamics of ignition, flame development and propagation. Through space carving, the three-dimensional flame contour can be estimated. From this contour, properties like flame length, flame height, ignition locations and flame directions can be extracted. The technique is demonstrated by measurements on diesel flames inside a marine two-stroke engine with a bore diameter of 500 mm. It is found to be a valuable tool for spatiotemporal flame mapping in this asymmetric industrial combustion system.
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