Long chain alcohols such as 1- and iso-pentanol are foreseen as a suitable replacement for ethanol, due to more favorable physical properties (higher energy density, higher boiling point and lower ...hygroscopicity). The present study presents high accuracy laminar flame speed measurements for iso-pentanol/air and 1-pentanol/air mixtures, at initial temperatures of 353 K, 433 K and 473 K, 1 bar pressure and equivalence ratios ranging from 0.7 to 1.5. Comparisons with previous measurements from the literature are also presented and the observed deviations are discussed in detail. The updated kinetic mechanism for alcohols combustion from the CRECK group at Politecnico di Milano is discussed and used for modeling purposes. For a more complete validation of the oxidation mechanism at high temperature conditions, modeling results are also compared with shock tube ignition delay times from the literature. This study extends the presently sparse and uncertain experimental database for high molecular weight alcohols oxidation in laminar flames, providing high accuracy and reliable experimental data of use for alcohols oxidation mechanism development and improvement.
Experimental and numerical studies are carried out to construct reliable surrogates that can reproduce aspects of combustion of JP-8 and Jet-A. Surrogate fuels are defined as mixtures of few ...hydrocarbon compounds with combustion characteristics similar to those of commercial fuels. The combustion characteristics considered here are extinction and autoignition in laminar non premixed flows. The “reference” fuels used as components for the surrogates of jet fuels are
n-decane,
n-dodecane, methylcyclohexane, toluene, and
o-xylene. Three surrogates are constructed by mixing these components in proportions to their chemical types found in jet fuels. Experiments are conducted in the counterflow system. The fuels tested are the components of the surrogates, the surrogates, and the jet fuels. A fuel stream made up of a mixture of fuel vapors and nitrogen is injected into a mixing layer from one duct of a counterflow burner. Air is injected from the other duct into the same mixing layer. The strain rate at extinction is measured as a function of the mass fraction of fuel in the fuel stream. The temperature of the air at autoignition is measured as a function of the strain rate at a fixed value of the mass fraction of fuel in the fuel stream. The measured values of the critical conditions of extinction and autoignition for the surrogates show that they are slightly more reactive than the jet fuels. Numerical calculations are carried out using a semi-detailed chemical-kinetic mechanism. The calculated values of the critical conditions of extinction and autoignition for the reference fuels and for the surrogates are found to agree well with experimental data. Sensitivity analysis is used to highlight key elementary reactions that influence the critical conditions of autoignition of an alkane fuel and an aromatic fuel.
Purpose
The aim was to evaluate the role of tumor-infiltrating lymphocytes (TIL) in predicting molecular response after preoperative endocrine or cytotoxic treatment for HR+/HER2− patients who do not ...achieve a pathological complete response.
Methods
Stromal (Str) TIL were centrally evaluated on samples from diagnostic core-biopsies of HR+/HER2− patients included in two prospective randomized trials: the LETLOB trial (neoadjuvant endocrine-based treatment) and the GIOB trial (neoadjuvant chemotherapy-based treatment). Pre- and post-treatment Ki67 was centrally assessed.
Results
StrTIL were evaluable in 111 cases (
n
= 73 from the LETLOB trial and
n
= 38 from the GIOB trial). Median StrTIL was 2%. Patients with high StrTIL (StrTIL ≥10%,
n
= 28) had more frequently breast cancer of ductal histology (
p
= 0.02), high grade (
p
= 0.049), and high Ki67 (
p
= 0.02). After neoadjuvant endocrine treatment (LETLOB cohort), a significant Ki67 suppression (
p
< 0.01) from pre- to post-treatment was observed in both the low and high StrTIL groups. High StrTIL patients achieve more frequently a relative Ki67 suppression ≥50% from baseline as compared to low StrTIL patients (55 vs. 35%,
p
non significant). After neoadjuvant chemotherapy (GIOB cohort), a significant Ki67 suppression was observed only for low StrTIL patients (Wilcoxon
p
= 0.001) and not in the high StrTIL group (
p
= 0.612). In this cohort, the rate of patients achieving a relative Ki67 suppression ≥50% from baseline was significantly higher in the high vs low StrTIL group (64 vs. 10%,
p
= 0.003). Geometric mean Ki67 suppression was evaluated in each cohort according to StrTIL: the lowest value (−41%) was observed for high StrTIL cases treated with chemotherapy.
Conclusions
This hypothesis-generating study suggests that in HR+/HER2− breast cancer StrTIL at baseline may influence the achievement of a molecular response after neoadjuvant treatment. Further evaluation in large studies is needed, and interaction with the type of treatment warrants to be explored.
A general and detailed chemical kinetic model has been developed and tested to investigate the interaction between NO and hydrocarbons during the oxidation of a hydrocarbon at low temperatures. The ...model describes the influence of NO and was validated through comparison with several different experimental data sets for various temperatures, stoichiometries and hydrocarbon fuels. The good agreement observed across the whole investigation range confirms the validity of the kinetic assumptions and the reliability of the model. The effect of NO on the oxidation of hydrocarbons and the influence of hydrocarbons on the conversion of NO to NO
2 are discussed. The kinetic scheme also refers to higher temperatures, as typical of reburning, but to reduce the breadth of the work the paper is focused on low temperature interactions. Nevertheless, the paper presents the complete set of reactions in the nitrogen submechanism.
•A strategy to predict pollutants’ formation in turbulent combustion is proposed.•The transport equations of species are solved using a fully-coupled approach.•Accurate prediction of pollutants’ ...emissions through detailed kinetic schemes.•Industrial equipment can be simulated thanks to parallel data distribution.
In this paper we describe and apply a parallel code, named KPPSMOKE, for the prediction of pollutant emissions from combustion devices operating in turbulent conditions. The approach is based on the kinetic post-processing of CFD simulations, which are transformed into equivalent networks of perfectly stirred reactors and solved using a detailed kinetic mechanism (hundreds of species). The numerical algorithm is based on a fully-coupled technique, in which the highly non-linear mass balance equations are solved together, by alternating different resolution methods in order to ensure high accuracy and fast convergence. As a result of KPPSMOKE parallel structure, large reactor networks characterizing industrial devices (105–106 reactors) can be solved in reasonable times (∼hours).
The accuracy and the reliability of the algorithm was demonstrated on a lab-scale burner and on a full-scale industrial device, i.e. a combustor for aircrafts. The numerical performance was also assessed in terms of parallel efficiency and speedup.
The kinetic characterization of the oxidation of ethanol-gasoline mixtures is of interest due mainly to its role in sustainable combustion processes. The aim of this paper is to revise and validate a ...kinetic mechanism of ethanol combustion inside a general scheme able to describe the pyrolysis and oxidation of hydrocarbons. Model predictions and experimental measurements are discussed and successfully compared across a wide range of operating conditions. This study moves from the detailed analysis of species profiles of ethanol oxidation in jet-stirred, flow reactors and laminar flames to global combustion properties (ignition delay times and laminar flame speeds) by referring to a large set of literature data; the analysis is then extended to the effect of ethanol on the combustion of ethanol-gasoline mixtures. The large experimental data set discussed in this paper includes very recent measurements and covers a wide range of operating conditions. The chemical effect of ethanol on the combustion properties of ethanol-gasoline mixtures is also highlighted.
In this paper the extinction of laminar, premixed flames fed with a mixture of methane and hydrogen is numerically modeled in unsteady conditions. The aim of the work is to better understand how the ...oscillations of the flow field and the addition of hydrogen to the fuel mixture affect the extinction limits of the flame.
For this purpose, numerical simulations of laminar, premixed, symmetric counter-flow flames were performed using a detailed kinetic mechanism (∼80 species and ∼1400 reactions). Steady-state conditions were first analyzed and the numerical results were compared with the experimental measurements with satisfactory agreement, showing that the main effect of hydrogen addition is to increase the characteristic extinction limits of the flame.
Then, harmonic oscillations were imposed on the inlet velocities, in order to study the response of the flame (in terms of temperature and species) to the unsteadiness of the flow field. The results clearly showed that, as long as the averaged strain rate is smaller than the steady state strain rate, the oscillating flames can always survive instantaneous high strain rates for sufficiently high frequencies. Moreover, the unsteady flames are able to survive to instantaneous strain rates well beyond the corresponding steady-state extinction conditions, especially when the frequency of oscillations is large. Eventually, it was found that the flame behavior under unsteady conditions can be effectively explained using the Stokes’ number (i.e. the ratio between the frequency of imposed oscillations and the strain rate of the flame), a dimensionless parameter comparing the characteristic times of the flame and of the imposed disturbances.
► Laminar premixed, counter-flow flames fed with CH4/H2 mixtures were numerically modeled. ► The main effect of H2 addition in steady-state conditions is to increase the extinction limits. ► The effects of unsteadiness on the extinction limits were analyzed. ► The unsteady flames survive at strain rates larger than those in steady-state conditions. ► The behavior of unsteady flames can be effectively explained through the Stokes number.
This paper presents a general and detailed chemical kinetic scheme developed and validated to investigate the interactions between NO and simple hydrocarbons during thermal oxidation and reburning. ...In a previous paper
1 the low temperature mechanism was presented. In this work the attention is drawn on the high-temperature conditions, referring typically to the reburning process where the hydrocarbon fragments reduce NO to HCN and N
2. The goal is to obtain a better understanding of the interactions between NO and hydrocarbons, through the development of a general detailed kinetic model, which describes accurately the influence of NO in a wide temperature range, for different fuels and stoichiometry conditions. The model has been validated through the comparison with experimental measurements coming from different research groups, referring to several hydrocarbon fuels in different operative conditions. Even though the characteristic mechanisms are quite different from the low temperature conditions, the observed agreement in the whole investigation range confirms the correctness of the kinetic assumptions and extends the reliability of the model.
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