A numerical study on the ability to predict the heat release rate, equivalence ratio and NO emission using chemiluminescence in counterflow premixed methane flames

Chemiluminesce nce emission from flames ha s been implemented to monitor and control heat release rate (HRR) , local equivalence ratio (ER) and key pollutant emissions in gas turbine c ombustors and automotive engines. In the present study, in order t o simultaneously simulate the chemiluminescence of OH * , CH * (A), C 2 * and CO 2 * (where * denotes the excited state) and to obtain insight on the relation between chemiluminescence, heat release , equivalence ratio and NO emission , numerical studies on 1 - D counterflow premixed methane flames were conducted. A new detailed reaction mechanism, incorporating sub - reaction models for excited state OH * , CH * (A), C 2 * and CO 2 * radicals was assembled in thi s study. T hree detailed reaction mechanisms available in the literature for C1 – C3 hydrocarbons were employed in the current work. Results show that OH * , CH * (A) and CO 2 * chemiluminescence can accurately reproduce the heat release rate trend , while t he OH * /C H * (A) chemi luminescent intensity ratio var ies non - monotonically with the equivalence ratio . Further, it is shown that t he CO 2 * and C 2 * chemiluminescence can be utilized to indicate the levels of NO emissions. However, the choice of the fuel oxidant chemica l mechanism can highly influence the model’s ability to predict the behavior of the aforementioned combustion parameters through chemiluminescence simulations

Analysis of CH2_{2}O x OH as marker for fuel-rich air to pure oxy-fuel flames under higher preheat temperature and elevated pressure

The scope of the present work is a numerical and experimental investigation about the range of validity in terms of applicability of CH$_{2}$OxOH as a marker for the heat release rate (HRR) for fuel-rich air to pure oxy-fuel flames including preheating and elevated pressure. Therefore, laminar, freely propagating 1d CH$_{4}$ flames were calculated, where oxygen content in the oxidizer (from air to pure oxy-fuel combustion), inlet temperature and pressure were varied for a wide range of the equivalence ratios. The preheat temperature and pressure were parametrically changed from 300 K to 573 K and 1 bar to 5 bar, respectively. Different reaction mechanisms were used, namely GRI30, DLR, USC/II, Caltech2.3 and ABF. The performance of the CH$_{2}$OxOH as a marker for HRR is assessed in terms of correlation coefficients of their profiles in laminar flames. The comparison of the obtained correlations of CH$_{4}$/air and CH$_{4}$/O$_{2}$ flames shows that in case of air combustion, the HRR can be accurately estimated by the product of CH$_{2}$OxOH for slightly rich flames (Φ = 1.5), whereas the quality of the correlation degrades with increasing equivalence ratio. In contrary, the correlation coefficient increases with higher equivalence ratios in the fuel-rich domain for enhanced oxygen contents in the oxidizer. For pure oxyfuel combustion, the best correlation is found at an equivalence ratio of approximately Φ = 3.0. Elevated pressure leads in all flames to better correlations at lower equivalence ratios compared to standard inlet conditions, whereas preheating induces the opposite trend and expands the valid regime. A series of CH$_{4}$/air flames were also investigated experimentally in a range of the equivalence ratio between 1 < Φ < 2 at standard inlet conditions. The qualitative CH$_{2}$O (excitation at 355 nm) and OH (excitation at 283 nm) concentration were resolved applying two-dimensional LIF for flames stabilized at a McKenna burner. Comparisons show similar trends for measurements and numerical simulations

Combustion Characterization of Solvents used in Coil Coating Processes: Experiments and Kinetic Modelling

A combined experimental and chemical kinetics modelling approach is presented to account for the combustion behaviour of solvents utilized in coil coating processes. Heating values and laminar burning velocities of typical industrial solvent formulations comprising alcohols, ethers, esters and aromatics are experimentally investigated. Due to the complexity of species participating in the solvent formulations surrogate solvents are introduced, one for each considered formulation. An “in-house” chemical kinetics mechanism has been extended in order to take into account the solvents’ combustion and consists of 321 species participating in 1826 reactions. Its overall performance is validated against the laminar burning velocity measurements. A good qualitative and quantitative reproduction of the experimental curves is depicted with maximum discrepancies observed in the range of 10-15%

Towards identifying flame patterns in multiple, late injection schemes on a single cylinder optical diesel engine

The work investigates the effect of various post-injection strategies on the flame patterns in a Ricardo Hydra optical single cylinder light duty diesel engine, operated in a partially premixed combustion mode (PPC), under low load (IMEP: ca. 2.3 bar) low speed (1200 rpm) conditions. The effect of postinjection fuel amount (12 and 24% of the total fuel quantity per cycle) and post-injection timing (0, 5, 10 deg aTDC) are investigated via pressure trace analysis and optical measurements. Flame propagation is captured by means of high speed flame natural luminosity imaging and of CH* , C2 * and OH* line-of-sight chemiluminescence measurements. Results indicate that post-injections suppress mixture reactivity but enhances oxidation, and that a larger amount of fuel and/or later post injection, leads to higher levels of natural luminosity, indicating possible higher soot-out emissions, while post injection close to the main combustion event appears to have a beneficial effect on the soot oxidation processes

A comparative study on the effect of simulated EGR environment on spray characteristics under engine-like conditions

Abstract Increasing concern over air quality and security of energy supply poses challenges to engine research and manufacturing. Despite improvements in conventional engine design, many alternatives are winning their place in order to further reduce engine-out emissions. Sophisticated operating modes, such as homogeneous charge compression ignition (HCCI) and Partially premixed Charge Compression Ignition (PCCI), often coupled with exhaust gas recirculation and/or aftertreatment are employed for regulating nitric oxide (NO x ) and soot emission levels. However, a totally homogeneous mixture is unachievable in practical engines. Inherent inhomogeneities in fuel concentration and temperature may significantly affect the ignition and combustion processes, hence various control strategies attract research interest. The present work demonstrates the potential of emission reduction in Diesel engines operating under high boost conditions through a combination of multi-injection strategies and high EGR schemes

Opportunities for low indirect land use biomass for biofuels in Europe

Sustainable biofuels are an important tool for the decarbonisation of transport. This is especially true in aviation, maritime, and heavy-duty sectors with limited short-term alternatives. Their use by conventional transport fleets requires few changes to the existing infrastructure and engines, and thus their integration can be smooth and relatively rapid. Provision of feedstock should comply with sustainability principles for (i) producing additional biomass without distorting food and feed markets and (ii) addressing challenges for ecosystem services, including biodiversity, and soil quality. This paper performs a meta-analysis of current research for low indirect land use change (ILUC) risk biomass crops for sustainable biofuels that benefited either from improved agricultural practices or from cultivation in unused, abandoned, or severely degraded land. Two categories of biomass crops are considered here: oil and lignocellulosic. The findings confirm that there are significant opportunities to cultivate these crops in European agro-ecological zones with sustainable agronomic practices both in farming land and in land with natural constraints (unused, abandoned, and degraded land). These could produce additional low environmental impact feedstocks for biofuels and deliver economic benefits to farmer