84 research outputs found
Measurements and modeling of piston temperature in a research compression ignition engine during transient conditions
Abstract The knowledge of piston temperature during internal combustion engine operation represents a precious information to evaluate heat losses and engine efficiency. Experimental measurements of piston temperature during engine functioning is very challenging; hence, modeling this process can be very helpful. In the present work, temperature measurements have been collected using a research compression ignition engine, both in motored and fired mode. They have been used to set-up a 1d model of heat transfer through the piston optical window. A good agreement has been obtained. Moreover, the model can provide information not available from experiments
ADHD & Eating Pathology: Is there an association between ADHD & eating disorders?
This dissertation will examine the association between ADHD & eating pathology, a link that has gone unnoticed for decades. Many females tend to internalise ADHD symptoms, most commonly reported in the form of depression, anxiety, and mood disorders; however, the literature review will provide evidence that suggests the development of an eating disorder may be the result of internalising ADHD symptoms. This dissertation will take the form of an autoethnography combined with an extended, critical literature review. I will be reflecting on my personal experience with comorbid ADHD & bulimia nervosa to support claims made in the literature. The relationship between ADHD and multiple forms of eating pathology, including bulimia nervosa, anorexia nervosa, and binge eating disorder will all be examined, as well as the relationship between ADHD and obesity and certain nutritional factors that contribute to ADHD. The literature review will provide evidence that there is a direct association between ADHD & bulimia and binge eating disorder. Possible treatment options, including medication for individuals suffering with comorbid ADHD & an eating disorder will be discussed along with other implications for practice
A spectroscopy study of gasoline partially premixed compression ignition spark assisted combustion
Nowadays many research efforts are focused on the study and development of new combustion modes, mainly based on the use of locally lean air–fuel mixtures. This characteristic, combined with exhaust gas recirculation, provides low combustion temperatures that reduces pollutant formation and increases efficiency. However these combustion concepts have some drawbacks, related to combustion phasing control, which must be overcome. In this way, the use of a spark plug has shown to be a good solution to improve phasing control in combination with lean low temperature combustion. Its performance is well reported on bibliography, however phenomena involving the combustion process are not completely described. The aim of the present work is to develop a detailed description of the spark assisted compression ignition mode by means of application of UV–Visible spectrometry, in order to improve insight on the combustion process.
Tests have been performed in an optical engine by means of broadband radiation imaging and emission spectrometry. The engine hardware is typical of a compression ignition passenger car application. Gasoline was used as the fuel due to its low reactivity. Combining broadband luminosity images with pressure-derived heat-release rate and UV–Visible spectra, it was possible to identify different stages of the combustion reaction. After the spark discharge, a first flame kernel appears and starts growing as a premixed flame front, characterized by a low and constant heat-release rate in combination with the presence of remarkable OH radical radiation. Heat release increases temperature and pressure inside the combustion chamber, which causes the auto-ignition of the rest of the unburned mixture. This second stage is characterized by a more pronounced rate of heat release and a faster propagation of the reactions through the combustion chamber. Moreover, the measured UV–Visible spectra show some differences in comparison with the other stages. The relative intensities in of spectra from different combustion radicals have also been related to the different combustion phases.The authors acknowledge that part of this work was performed in the frame of Project DUFUEL TRA2011-26359, funded by the Spanish Government. The authors also thank GM for technical assistance and its support in other parts of this work.Pastor Soriano, JV.; GarcĂa Oliver, JM.; GarcĂa MartĂnez, A.; MicĂł Reche, C.; Durret, R. (2013). A spectroscopy study of gasoline partially premixed compression ignition spark assisted combustion. Applied Energy. 104:568-575. https://doi.org/10.1016/j.apenergy.2012.11.030S56857510
Application of UV Visible Light Absorption and Scattering technique to low absorption fuels under diesel-like conditions
Light Absorption and Scattering technique (LAS) has been applied for the measurement of fuel vapour distribution
in diesel-type sprays. This technique is usually limited to fuels with relatively high absorptivity,
which are sometimes not commonly used as surrogate fuels. In the present paper, a comparison of fuels
with very different absorptive properties has been made to determine the range of application of the
methodology. A calibration procedure has been applied to n-decane (DEC), a binary blend of n-decane
and n-hexadecane (50DEC) and three blends of n-heptane with a highly-absorpting fuel (HEPB1,
HEPB2 and HEPB3). This methodology enables the in-situ quantification of absorption coefficients at high
pressure and temperature by creating a uniform mixture inside the cylinder. Results have been later
applied for the quantification of fuel vapour distribution in sprays for DEC, 50DEC and HEPB3. Results
obtained with these range of fuels have enabled to establish the limit in terms of absorption coefficient
needed to get consistent results with the technique.This work was partially funded by the Government of Spain through Project TRA2011-26359 and Grant BES-2012-059721. In addition, the authors acknowledge that some equipment used in this work has been partially supported by FEDER project funds (FEDER-ICTS-2012-06), framed in the operational program of unique scientific and technical infrastructure of the Ministry of Science and Innovation of Spain.Pastor Soriano, JV.; GarcĂa Oliver, JM.; LĂłpez, JJ.; MicĂł Reche, C. (2016). Application of UV Visible Light Absorption and Scattering technique to low absorption fuels under diesel-like conditions. Fuel. 179:258-266. https://doi.org/10.1016/j.fuel.2016.03.080S25826617
Study of the auto-ignition phenomenon of PRFs under HCCI conditions in a RCEM by means of spectroscopy
An investigation of the effects of contour conditions and fuel properties on the auto-ignition and combustion
process under HCCI conditions is presented in this study. A parametric variation of initial temperature,
intake pressure, compression ratio, oxygen concentration and equivalence ratio has been carried out
for Primary Reference Fuels in a Rapid Compression Expansion Machine while applying spectroscopy. The
results have also been contrasted with natural chemiluminescence measurements. Additionally, the
experiments have been simulated in CHEMKIN and the results derived from the optical techniques have
been compared with the results from the chemical kinetics of the process, validating the chemical kinetic
mechanism and an additional sub-model of excited OH
. Two different scenarios can be seen according to
the results from the spectrograph. For very lean or very low-temperature combustions no peak of OH is
seen at 310 nm of wavelength, proving that the luminosity came from the CO continuum rather than
from the OH
. However, for more intense combustions (richer equivalence ratios, higher temperatures
or lower EGR rates) spectrography shows a clear peak of OH that has much longer time of life than
the corresponding to the CO continuum. The main chemical reaction that causes this two scenarios
has been identified as H Ăľ HO2 ) 2OH. The increase of relevance of this reaction at high combustion temperatures
causes a higher OH accumulation, which leads to a brighter OH emission. Finally, for low temperature
combustions the CO continuum out-shines the OH radiation so the light emitted by this radical
cannot be detected by means of natural chemiluminescence.
201The authors would like to thank different members of the LAV team of the ETH-Zurich for their contribution to this work. The authors are grateful to the Universitat Politecnica de Valencia for financing the Ph.D. studies of W. Vera-Tudela (FPI SP1 grant 30/05/2012) and his stay at ETH-Zurich (grant 30/12/2014). Finally, the authors would like to thank the Spanish Ministry of Education for financing the Ph.D. studies of Dario Lopez-Pintor (grant FPU13/02329) and his stay at ETH-Zurich (grant EST14/00626).Desantes Fernández, JM.; GarcĂa Oliver, JM.; Vera-Tudela-Fajardo, WM.; LĂłpez Pintor, D.; Schneider, B.; Boulouchos, K. (2016). Study of the auto-ignition phenomenon of PRFs under HCCI conditions in a RCEM by means of spectroscopy. Applied Energy. 179:389-400. https://doi.org/10.1016/j.apenergy.2016.06.134S38940017
ADHD & Eating Pathology: Is there an association between ADHD & eating disorders?
This dissertation will examine the association between ADHD & eating pathology, a link that has gone unnoticed for decades. Many females tend to internalise ADHD symptoms, most commonly reported in the form of depression, anxiety, and mood disorders; however, the literature review will provide evidence that suggests the development of an eating disorder may be the result of internalising ADHD symptoms. This dissertation will take the form of an autoethnography combined with an extended, critical literature review. I will be reflecting on my personal experience with comorbid ADHD & bulimia nervosa to support claims made in the literature. The relationship between ADHD and multiple forms of eating pathology, including bulimia nervosa, anorexia nervosa, and binge eating disorder will all be examined, as well as the relationship between ADHD and obesity and certain nutritional factors that contribute to ADHD. The literature review will provide evidence that there is a direct association between ADHD & bulimia and binge eating disorder. Possible treatment options, including medication for individuals suffering with comorbid ADHD & an eating disorder will be discussed along with other implications for practice
Spectroscopic measurements of premixed combustion in diesel engine
Digital imaging and spectroscopic techniques, with high temporal and spatial resolution, were applied in
order to study the low temperature combustion process. Injection and combustion phases were analysed
by digital imaging. Mixing process, autoignition and pollutants formation were investigated by broadband
ultraviolet–visible extinction spectroscopy and flame emission measurements. Moreover, fuel distribution
and oxidation were studied as well. Liquid fuel and vapour phase, injected around the top dead
centre, were analysed. The liquid diesel fuel was observed by extinction measurements when the liquid
jet reached the bowl rim and aromatic compounds due to fuel decomposition were identified. On the
other side, the vapour fuel was detected about 2ďż˝ after the injection start and liquid fuel disappeared.
Then, radicals and species were detected in the combustion chamber. They are interesting in order to
study the chemical kinetics of low temperature combustion process. The chemiluminescence spectra
of HCCI combustion appeared as well as several distinct peaks corresponding to the emission from
HCO, HCHO, CH, and OH. In particular, this latter was clearly evident during the whole premixed combustion
and dominated the process also after the end of the premixed phase of the heat release. Advancing
the combustion, bright spots due to not homogeneous charge were detected. They were the source of the
very little soot amount detected at the exhaust pipe. Finally, the injection pressure effect on the development
of low temperature combustion was analysed
First and second generation biodiesels spray characterization in a diesel engine
Potential improvement on exhaust emissions, biodegradability and the possibility to reduce dependence
on fossil fuel resources has led to an increasing interest on the use of biofuels for transport application. In
this work, the analysis of the spray behaviour of first and second generation biodiesel in a Euro 5, common
rail transparent diesel engine has been performed. GTL, SME and RME fuels have been used in blends
at 100% and 50% in volume; while reference fuel consisted of commercial diesel. Two engine operating
conditions of the NEDC have been selected: 1500 rpm at 2 bar of brake mean effective pressure (BMEP)
and 2000 rpm at 5 bar BMEP. The injection process has been accurately studied, and the influence of the
combustion process on the spray behaviour has been taken into account. Typical jets parameters such as
penetration and cone angles have been detected and a comparison with theoretical models of Hiroyasu
and Siebers has been performed. A new correlation for the forecasting of the jet penetration has been
obtained starting from Hiroyasu equations. An image-based method has been applied for the identification
of the phenomena that control the spray behaviour during its evolution in the combustion chamber.
First generation biodiesels, pure and blends, show longer penetration with respect to the reference fuel
at both the engine speed analysed. Moreover, they penetrate for a longer time in the combustion chamber,
because of the longer energizing time set, so impingement phenomena can be observed. On the other
hand, the second generation biodiesels penetrate less than reference one, due to its lower density, but
also because the combustion of the pilot injection causes an increase of pressure that obstructs the penetration
in the combustion chamber. Finally, a good agreement between the breakup times computed by
means of the Hiroyasu and Siebers correlations and the ones from the experimental data has been found
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