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Wyszukujesz frazę "Mayer, J. F." wg kryterium: Autor


Wyświetlanie 1-6 z 6
Tytuł:
A preconditioned solution scheme for the computation of compressible flow in turbomachinery at arbitrary mach numbers
Autorzy:
Anker, J. E.
Mayer, J. F.
Stetter, H.
Powiązania:
https://bibliotekanauki.pl/articles/1986683.pdf
Data publikacji:
2002
Wydawca:
Politechnika Gdańska
Tematy:
preconditioning
non-reflecting boundary condition
Mach number independency
turbomachinery flow
Opis:
A preconditioned solution scheme for the computation of compressible flow in turbomachinery at arbitrary Mach numbers is presented. The preconditioning technique used is applied to a state-of-the-art explicit, time-marching Navier-Stokes code which originally was developed for compressible, high-speed turbomachinery applications. It combines the ideas of low Mach number preconditioning and artificial compressibility method into a unified approach where principally fluids with arbitrary equations of state can be simulated. As shown by the test cases presented, it allows the code to simulate flows efficiently and accurately independent of the Mach number. A description of the Navier-Stokes equations for rotating coordinate systems, along with the solution scheme and the details of the preconditioning method is given. Since turbomachinery computations are often performed on truncated domains, the solution scheme should be used in conjunction with non-reflecting boundary conditions. A change in the time-dependency of the equations due to preconditioning necessitates a modification of the boundary conditions. Thus, a derivation of the appropriate boundary conditions for the presented preconditioned scheme was performed and the resultant equations are given in this paper. The effectiveness of the new boundary conditions is demonstrated by comparing them with both boundary conditions that use the standard one-dimensional characteristic approach and the original boundary conditions for the non-preconditioned case.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2002, 6, 1; 143-176
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of soil aggregate breakdown dynamics under low dispersive ultrasonic energies with sedimentation and X-ray attenuation
Autorzy:
Schomakers, J.
Zehetner, F.
Mentler, A.
Ottner, F.
Mayer, H.
Powiązania:
https://bibliotekanauki.pl/articles/24254.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Źródło:
International Agrophysics; 2015, 29, 4
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Changes of the 2-stroke aerosol in the exhaust sampling system
Autorzy:
Czerwinski, J.
Comte, P.
Mayer, A.
Reutimann, F.
Powiązania:
https://bibliotekanauki.pl/articles/247914.pdf
Data publikacji:
2012
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
scooters
two-stroke direct injection
carburettor
2-stroke aerosol
nanoparticulate emissions
Opis:
Nanoparticle emissions of two 2-stroke scooters were investigated along the exhaust- and CVS-system (Constant Volume Sampling) with closed and with open line (cone). Due to their technology, the scooters produce different kind of aerosol (state of oxidation & SOF-content) and in addition to that they were operated with and without oxidation catalyst. The scooters represent a modern technology with direct injection TSDI* ) (two stroke direct injection) and with carburettor. The tests were performed at two constant speeds of the vehicles (20 km/h & 40 km/h) according to the measuring procedures, which were established in the previous research in the Swiss Scooter Network. The nanoparticulate emissions were measured by means of SMPS (CPC) and NanoMet (abbreviations see at the end of this paper). The most important results are: - the changes of the PSD's of the aerosol along the exhaust and CVS-system are connected to the average gas temperature and PC-concentration, which result after the different dilution steps and cooling down in the connecting pipe, - in the "open" variant of exhaust gas extraction there is a dilution step with unfiltered ambient air directly after tailpipe. This causes a stop of agglomeration, reduction of diffusion loses and increased background NPconcentration. There is also lower post oxidation of CO & HC. In some cases spontaneous condensates due to the temperature drop are supposed, - with the "closed" variant there is a stronger reduction of SMPS PC's along the gas way, than with the open variant. This is to explain with the higher temperatures and concentrations in the closed system, which enable more intense thermophoresis - and diffusion losses, - the NP-concentrations measured with "open" variant are always higher, - most intense oxidation is observed with Peugeot Carb: due to the SAS, rich tuning and a relatively high temperature level there are oxidation effects already without catalyst (temp. approx. 350 centigrade). With catalyst the temperature is in the range of 400centigrade and the oxidation is so intense, that the particles are nearly eliminated. The type of sampling: "open", or "closed" as well as the sampling position in the exhaust installation have significant influence on the measured nanoparticles emission results.
Źródło:
Journal of KONES; 2012, 19, 2; 109-119
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Combined DPF+SCR systems for retrofitting in the VERT quality verification tests
Autorzy:
Czerwinski, J.
Zimmerli, Y.
Mayer, A.
Bunge, R.
Heeb, N.
Lemaire, J.
Jauss, F.
Powiązania:
https://bibliotekanauki.pl/articles/248088.pdf
Data publikacji:
2008
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
diesel emission reduction
diesel particle filter
SCR
limited and unlimited emissions
deNOx
Opis:
New Diesel exhaust gas aftertreatment systems, with DPF*) and deNOx (mostly SCR) inline application are very important step towards zero emission Diesel fleet. Solid quality standards of those quite complex systems are urgently necessary to enable decisions by several authorities. The Swiss Federal Office of the Environment BAFU and the Swiss Federal Roads Office ASTRA decided to support further activities of VERT to develop appropriate testing procedures and to define the quality criteria. The present report informs about the international network project VERT *) dePN (de-activation, de-contamination, disposal of particles & NOx), which was started in Nov. 2006 with the objective to introduce the SCR-, or (DPF+SCR)-systems in the VERT verification procedure. Examples of results with some investigated systems are given. The most important statements are: - the investigated combined aftertreatment systems (DPF+SCR) for dynamic engine application efficiently reduce the target emissions with deNOx-efficiency up to 92% (if operated in the right temperature window) and filtration efficiency based on particle count up to 100%, - the average NOx conversion rate at transient operation (ETC) depends strongly on the exhaust gas temperature profile and the resulting urea dosing control, - the NP filtration efficiency, which is verified at stationary engine operation is perfectly valid also at the transient operation. The present results will be confirmed in the further project activities with other systems and with different testing cycles. A special attention will be paid to the operational profiles, which are representative for low emissions zones LEZ.
Źródło:
Journal of KONES; 2008, 15, 3; 89-101
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigations of emissions of reactive substances NO2 and NH3 from passenger cars
Autorzy:
Czerwinski, J.
Comte, P.
Güdel, M.
Lemaire, J.
Mayer, A.
Heeb, N.
Berger, H.
Reutimann, F.
Powiązania:
https://bibliotekanauki.pl/articles/133799.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Naukowe Silników Spalinowych
Tematy:
exhaust emissions
reactive substances
NO2
NH3
emisje spalin
substancje reaktywne
Opis:
Public concern and complaints regarding ambient air in zones of dense traffic pertains to two compounds of nitrogen, nitrogen dioxide (NO2) and ammonia (NH3); both are toxic and strongly irritant, such that legal limitations are under discussion. This paper contributes to measuring methods as already in part proposed by GRPE subgroup WLTP-DTP (Worldwide Light Duty Test Procedures – Diesel Test Procedures) for NO2. Despite legally lowered NOx emission levels, lumping both, NO2 and NO, levels of NO2 have risen in cities and agglomerations as a result of both, deployed catalytic exhaust after-treatment devices and low sulphur Diesel fuels. In present tests two different combinations of NO2 measuring methods as proposed by WLTP were checked on Diesel cars for practicability in handling and accuracy. These integral, indirect methods (NO2 = NOx – NO) have been found as useful tools for estimate of NO2 and with use of appropriate analyzers a satisfactory accuracy was attained. Furthermore, attention was brought to ammonia (NH3) emitted by gasoline engines with three way catalysts (TWC) which ought not to be ignored while on the other hand SCR systems for Diesel engines are strictly regulated. Emission levels of more recent TWC turned out to be mostly below 20 ppm NH3. Vehicle of older technology exhibited significantly higher levels, about 10 times more. As chemical reactions depend on pressure and temperature (= i.e. flow condition in CVS-tunnel) as well as concentrations, doubts need to be considered on accuracy of results based on chemical reactive substances. Nevertheless, clear tendencies regarding changes of concentrations of NO2 and NH3 along the path-way could not be observed.
Źródło:
Combustion Engines; 2016, 55, 3; 24-33
2300-9896
2658-1442
Pojawia się w:
Combustion Engines
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Vert particle filter test procedure and quality standard for new and in-use diesel engines
Autorzy:
Mayer, A.
Czerwinski, J.
Kasper, M.
Leutert, G.
Heeb, N. V.
Ulrich, A.
Jaussi, F.
Powiązania:
https://bibliotekanauki.pl/articles/247808.pdf
Data publikacji:
2010
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
internal combustion engines
diesel engines
ecology
filters
particulates
Opis:
A new approach is needed to test particle filters for retrofitting Diesel engines. Considering the toxicity of the particles as also the physical and chemical attributes of particle filters, the optimal scheme is to test the components themselves independent of the deployment. That scheme ensures the highest effectiveness with least effort. It also enables evaluation of worst-case situations and assesses the hazards of secondary emissions. The Swiss standard SNR 277 205, which mandates the VERT test procedure, is a first step in that direction. The solution is derived from the physics of the filter media. The filtration of fine particles essentially depends on the particle size and the space velocity. The attributes of the emitting engine are only insignificantly relevant. Hence the physics and chemistry of particle filters can be investigated independent of the engine and its deployment duty. This concept facilitates a very thorough investigation of the size-dependent filtration, aging susceptibility, secondary emissions and extreme situations. Filter systems, which pass this detailed test, perform equally well in every retrofit configuration. This filter test concept was implemented 1998 in the VERT project and is successful for assessing retrofltting [4]. VERT approved fllter systems are already deployed in the Low Emission Zones of Europe, North and South America.
Źródło:
Journal of KONES; 2010, 17, 4; 313-322
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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