Approaches to improve mixing in compression ignition engines

This thesis presents three approaches to suppress soot emissions in compression-ignition (CI) engines. First, a fuel chemistry approach is proposed. A particular class of fuels - cyclic oxygenates - is identified which is capable of significantly reducing engine-out soot emissions. By means of experiments in "closed" and optical engines, as well as on an industrial burner, two possible mechanisms are identified that could account for the observed reduction in soot: a) an extended ignition delay (ID) and b) a longer flame lift-off length (FLoL). Further analysis of the available data suggests that both mechanisms are related to the inherently low reactivity of the fuel class in question. These findings are largely in line with data found in literature. In the second approach, it is attempted to reduce soot by adopting an alternative combustion concept: early direct injection premixed charge compression ignition (EDI PCCI). In this concept, fuel is injected relatively early in the compression stroke instead of conventional, close to top-dead-center (TDC), injection schemes. While the goal of soot reduction can indeed be achieved via this approach, an important draw-back must be addressed before this concept can be considered practically viable. Due to the fact that combustion chamber temperature and pressure is relatively low early in the compression stroke, fuel impingement against the cylinder liner (wall-wetting) often occurs. Consequently, high levels of unburned hydrocarbons (UHC), oil dilution and poor efficiency are observed. Several strategies, combining a limited engine modification with dedicated air management and fueling settings, are investigated to tackle this drawback. All of these strategies, and especially their combination, resulted in significantly lower UHC emissions and improved fuel economy. Although UHC emissions are typically a tell-tale sign of wall-wetting, as mentioned earlier, the relation between these two has long been hypothetical. Therefore, computational fluid dynamics (CFD) calculations of the injection process are performed to confirm whether or not liquid fuel impingement on the combustion chamber walls is indeed reduced as a result of the aforementioned UHC reduction strategies. Combined model and experimental results indicate that, for most strategies, the measured hydrocarbon emissions and predicted spray impingement are well correlated for a conventional DI injector nozzle, supporting the earlier assumption that wall-wetting is responsible for high hydrocarbon emissions in the investigated early injection timing approach. Lastly, in the third approach, a new injector nozzle design is proposed to improve the mixing process; again with the aim of soot abatement. In conventional nozzles, fuel is injected through 5-10 holes with nominal diameters of 100-200 micrometer. From both literature and in-house experiments it is known that mixing can be improved by reducing the nozzle diameter. Unfortunately, in order to preserve the overall flow rate, the number of required holes quadratically increases with a reduction in hole diameter. Alternatively, it is proposed to not drill the holes, but to use a porous medium instead. The utilized medium is a sintered metal permeated by an interconnected network of (continuous) pores with nominal diameters of 10 micrometer. This material is machined into a nozzle like shape and subjected to atmospheric injection tests as well as to experiments in the Eindhoven High Pressure Cell. Macroscopic experimental data (e.g. shorter ignition delay, larger spray volume) suggests that mixing is indeed improved. However, more research is required, preferably in a(n) (optical) engine, to investigate the impact on (soot) emissions and overall engine performance. In addition, the issues of durability and fouling still have to be addressed

Use of a perfume composition as a fuel for internal combustion engines

The present invention relates to fuel compositions containing perfume fractions, that is to say compositions of fragrance materials, and to the use of such perfume fractions containing fuel compositions to provide a fuel for internal combustion engines and burners. According to the present fuel composition for internal combustion engines and burners on basis of ethanol, wherein said fuel composition contains 1 -40 vol. % of a perfume fraction, based on the total fuel composition, said perfume fraction is constituted of one or more additives selected from a group consisting of essential oils, aroma compounds and aromatic oxygenates, the Volumetric Higher Heating Value (HHV), measured according to ASTM D240, of said perfume fraction is higher than or equal to 33,0 MJ/litre

A method for converting C1-C4 alcohols into higher-value hydrocarbon compounds

No abstract available

Spray growth of regular, synthetic, oxygenated and biodiesels in an optical engine

Spray formation has been studied in an optically accessible heavy-duty diesel engine for regular diesel,synthetic, oxygenated and biofuels using a high-speed digital camera. Images are analyzed with custom madealgorithms to obtain spray penetration length and spray cone angle as function of time. Results from 2 out of the 8 nozzle sprays have been used in the data analysis. Variation in spray equilibrium length and angle is observed between the fuels tested. Modelling of the fuel injection, taking great care to account for individual fuel properties, shows good correspondence with experimental results

Cartilage-specific ablation of XBP1 signaling in mouse results in a chondrodysplasia characterized by reduced chondrocyte proliferation and delayed cartilage maturation and mineralization

SummaryObjectiveTo investigate the in vivo role of the IRE1/XBP1 unfolded protein response (UPR) signaling pathway in cartilage.DesignXbp1flox/flox.Col2a1-Cre mice (Xbp1CartΔEx2), in which XBP1 activity is ablated specifically from cartilage, were analyzed histomorphometrically by Alizarin red/Alcian blue skeletal preparations and X-rays to examine overall bone growth, histological stains to measure growth plate zone length, chondrocyte organization, and mineralization, and immunofluorescence for collagen II, collagen X, and IHH. Bromodeoxyuridine (BrdU) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analyses were used to measure chondrocyte proliferation and cell death, respectively. Chondrocyte cultures and microdissected growth plate zones were analyzed for expression profiling of chondrocyte proliferation or endoplasmic reticulum (ER) stress markers by Quantitative PCR (qPCR), and of Xbp1 mRNA splicing by RT-PCR to monitor IRE1 activation.ResultsXbp1CartΔEx2 displayed a chondrodysplasia involving dysregulated chondrocyte proliferation, growth plate hypertrophic zone shortening, and IRE1 hyperactivation in chondrocytes. Deposition of collagens II and X in the Xbp1CartΔEx2 growth plate cartilage indicated that XBP1 is not required for matrix protein deposition or chondrocyte hypertrophy. Analyses of mid-gestation long bones revealed delayed ossification in Xbp1CartΔEx2 embryos. The rate of chondrocyte cell death was not significantly altered, and only minimal alterations in the expression of key markers of chondrocyte proliferation were observed in the Xbp1CartΔEx2 growth plate. IRE1 hyperactivation occurred in Xbp1CartΔEx2 chondrocytes but was not sufficient to induce regulated IRE1-dependent decay (RIDD) or a classical UPR.ConclusionOur work suggests roles for XBP1 in regulating chondrocyte proliferation and the timing of mineralization during endochondral ossification, findings which have implications for both skeletal development and disease

A Sensitive Gel-Based Method Combining Distinct Cyclophellitol-Based Probes for the Identification of Acid/Base Residues in Human Retaining Beta-Glucosidases

Medical Biochemistr