Parallel measurement of size distribution and spectral responses of particulate matter of diesel engines using 4-PAS and SMPS

Diesel engine emissions are under scrutiny in various fields. Due to its complex air quality and climate relevancies, the parallel measurement of size distribution and the spectral responses of thermally pretreated diesel particulate matter (DPM) provides a powerful opportunity to better understand its environmental impact and serve as a novel method for emission-based fuel development. In this study, we demonstrate the experimental results of number concentration, size distribution, and absorption spectra measurements of DPM as function of the operational conditions of diesel engines using different fuel types by 4-PAS and SMPS. The numberconcentration and the population statistics including TNC, TVC and GMD values as well as the absorption responses including OAC and AAE data at different operational wavelengths were measured at each operational mode of the engine using pure petroleum based B0 and FAME mixed diesel fuels at three different TD temperatures. The thermal evolution of the investigated emission was also investigated at all measurement conditions. The results demonstrate the applicability of multi-wavelength PA spectroscopy for the qualitative investigation of diesel emissions and thermal evolution using a multi wavelength PA instrument - thermodenuder unit combination

Controlled Laboratory Generation of Atmospheric Black Carbon Using Laser Excitation-Based Soot Generator: From Basic Principles to Application Perspectives: A Review

The mimicking of atmospheric soot with versatile chemophysical properties is a critical issue in many applications, starting from instrument calibration, through producing aerosol standards for academic research, and ending with the reduction of uncertainties associated to carbonaceous particulate matter in the atmosphere, just to name a few. The present study deals with laser ablation as a novel and interesting technique for the generation of soot with high elementary carbon (EC) content with microphysical features similar to diesel or atmospheric soot and for modelling biomass emission under well-controlled laboratory conditions. The operation of the laser-excitation-based soot generator and the characteristics of the produced particles are compared to the most widely used techniques like flame, spark discharge generators, and real combustion soot originating from diesel- and aircraft engines or from field measurement. The comparison shows that significant differences in the physicochemical features exist between the real combustion soot and the soot originating from different excitation mechanisms. Moreover, the soot produced by different techniques shown also significant differences. However, due to some inherent and favorable attributes of the laser ablation technique—such as the possibility of the independent variation of physical characteristics of the generated soot particles—the potential for modelling biomass burning or to produce soot particles even in the accumulation mode makes it a useful tool in many cases

Nemlineáris egyensúlyi rendszerek elméleti és módszertani kérdései = Theoretical and methodological issues of nonlinear equilibrium systems

A nemlineáris egyensúlyi rendszerek területén új eredményeket értünk el egyes feladatosztályok megoldhatóságának skaláris deriváltakra alapozott jellemzésével. A nemlineáris egyensúlyi rendszerek egy új megközelítését adtuk az izotón projekciós kúpok és kiterjesztéseik segítségével, és új eredményeket mutattunk be izoton projekciós kúpokkal történő rekurziók konvergenciáját illetően. Megmutattuk a metszetgörbülek nemlineáris optimalizálásban betöltött szerepét, és kvadratikus törtfüggvények speciális tulajdonságaival is foglalkoztunk. Fontos módszertani és implementációs eredményeket értünk el a kvadratikus optimalizálás belső pontos módszereinek területén is. Új blokkolási sémát fejlesztettünk ki a belső pontos algoritmusoknál előforduló szimmetrikus mátrixok faktorizációjához. A kvadratikus feltételek melletti konvex optimalizálás fontos feladatosztály a folytonos optimalizálásban. Megmutattuk, hogy belső pontos módszerekkel ez a feladatosztály nagy méretekben is hatékonyan kezelhető. Sikeresen alkalmaztuk a nemlineáris programozást döntési feladatok megoldásánál, elsősorban páros összhasonlítási mátrixok konzisztens márixokkal való közelítésével kapcsolatban. Új módszereket mutattunk be a legkisebb négyzetek célfüggvényű közelítés globális optimális megoldásainak meghatározására, valamint kiterjesztettük a sajátvektor módszert a nem teljesen kitöltött páros összehasonlítási mátrixok esetére | New results have been achieved in the field of nonlinear equilibrium problems by characterizing the solvability of some problem classes based on scalar derivatives. A new approach has been presented for the nonlinear equilibrium systems by the help of isotone projection cones and their extensions. Also, new results were presented on the convergence of recursions with isotone projection cones. We pointed out the role of sectional curvatures in nonlinear optimization. Some special properties of quadratic fractional functions have been also dealt with. We achieved important methodological and implementational results in the field of interior point methods of quadratic optimization. A new blocking scheme was developed for the symmetric matrix factorizations arising in interior point methods. An important class of the continuous optimization is that of the quadratically constrained convex problems. New techniques have been presented that improve the efficiency of interior point methods when solving quadratically constrained large-scale problems. Nonlinear programming was applied successfully at solving some decision problems, mainly at approximating pairwise comparison matrices by consistent ones. We presented new methods for finding the global optimal solutions in the case of approximating in the least squares sense. We also extended the eigenvector method for the case of incomplete pairwise comparison matrices

Measurement of aerosol from exhaust emission of motor vehicles using photoacoustic spectroscopy

There is an international concern about the adverse health effects of motor vehicles generated air pollutants in many towns and cities. To investigate the importance and effects of exhaust emissions from both diesel and gasoline motor vehicles to the human population, it is required to effectively measure the aerosol levels emitted into the atmosphere. This work aimed to measure emitted exhaust gases from diesel and gasoline light duty vehicles during controlled laboratory experiments using photoacoustic spectroscopy (PAS) method and a commercially available soot sensor (Opacimeter) as a control set up. Diesel and gasoline light duty vehicles were tested with altering engine speed without load (without dynamometer brake). From the experiments it was established that the response of the PAS system in aerosol measurements agreed well with the well-established and commercially available Opacimeter

The applicability of photoacoustic measurement technique for qualitative investigation of diesel emission

In our work parallel measurement of wavelength dependent optical absorption, size distribution and number-concentration were produced using multi wavelength photoacoustic spectrometer (4λ-PAS) and scanning mobility particle sizer (SMPS). For comparative study two different fuel type was tested at three different working points of the engine. The thermal evolution of the emission was also examined using thermodenuder (TD) unit. Bimodal size distribution of emissions at reference temperature was achieved using pure petroleum-based fuel (B0). The OAC values measured at the operating wavelengths of the instrument decreased with increasing rev and rated torque at all wavelengths. The wavelength dependence quantified by Aerosol Angström Exponent (AAE) can be used here for qualitative analysis of carbon emission and showed increased volatility of organic particles towards higher temperatures