Narrow Results

This paper presents a numerical method to calculate combustion coupled ejection flow in nozzle processes in Liquid Rocket Motor (LRM). A two-dimensional axi-symmetric numerical simulation for the injector element-combustor-and-nozzle model is carried out using the Finite Different (FD) method. In the simulation, the available Computational Fluid Dynamics (CFD) software FLUENT is employed with three key enhancements for material modelling. Firstly, the influence of the two-phase reacting flow is considered, in which the coupled implicit two-step finite difference method to solve the Re-averaged conjugated N-S equation with component conservative equation is used. Secondly, the 17-component, 12-step finite-rate chemical reaction model is employed. Thirdly, the Baldwin-Lomax model is used as turbulence model. These three enhancements are incorporated into the FLUENT code through its user subroutine capability. For both ignition and exhausted stages, the unsteady flow method is used while the steady flow method is adopted for the normally working stage. The distributions of the flow parameter in the combustor-nozzle system are achieved. In addition, the variations of flow parameter along with the time in different stages are also obtained. The results obtained from the numerical simulation are compared with independently available field tests data. Good agreement is observed.

The Bodmer-Terazawa-Witten hypothesis of absolutely stable quark matter made of up, down, and strange quarks ((u,d,s) matter) is of much astrophysical and fundamental interest. One consequence is a large binding energy release associated with the conversion of a neutron star to a quark star. A quantitative understanding of the dynamic aspect of the conversion is necessary in order to find out whether this energy is released quietly or in an explosive manner. We address numerically (i.e. solving the reaction-diffusion-advection equations for (u,d) to (u,d,s) combustion) the dynamic processes through which the conversion appears. We find fundamentally very different results from semi-analytic calculations, with front speeds that are several orders of magnitude higher for the former. Resolving the hadronic-quark-matter interface is necessary, since approximations like Coll’s condition may quench the burning, while properly resolving the flame can make combustion always thermodynamically favourable if the hypothesis of absolutely stable strange quark matter is true. We find that lepton physics, including weak decays, electron equation-of-state (EoS), neutrino EoS, and neutrino transport are at the very least as important to the physics of the burning front as the EoS of highly dense matter. In concert, these effects induce novel wrinkling instabilities (such as the deleptonization instability) possibly leading to a deflagration-detonation and/or a quark-core collapse Quark-Nova.

Some people think that carbon and sustainable development are not compatible. This textbook shows that carbon dioxide (CO₂) from the air and bio-carbon from biomass are our best allies in the energy transition, towards greater sustainability. We pose the problem of the decarbonation (or decarbonization) of our economy by looking at ways to reduce our dependence on fossil carbon (coal, petroleum, natural gas, bitumen, carbonaceous shales, lignite, peat). The urgent goal is to curb the exponential increase in the concentration of carbon dioxide in the atmosphere and hydrosphere (Figures 1.1 and 1.2) that is directly related to our consumption of fossil carbon for our energy and materials The goal of the Paris agreement (United Nations COP 21, Dec. 12, 2015) of limiting the temperature increase to 1.5 degrees (compared to the pre-industrial era, before 1800) is becoming increasingly unattainable (Intergovermental Panel on Climate Change (IPCC), report of Aug. 6, 2021). On Aug. 9, 2021 Boris Johnson, prime minister of the United Kingdom, declared that coal needs to be consigned to history to limit global warming. CO₂ has an important social cost…

Natural gas consists mainly of methane (CH₄) and ethane (CH₃CH₃) and other hydrocarbons in small quantities. Depending on the source it may also contain CO₂, nitrogen (N₂), hydrogen sulfide (H₂S) and helium (He). It is very abundant and its combustion contributes to the increase of the CO₂ content in the biosphere. Natural gas is a non-renewable fuel (Section 5.1). It is widely used to produce electricity, heat, chemicals including hydrogen, and hydrocarbons (liquid fuels) and as a fuel for motor vehicles…

A new kind of Opposite Axial Piston Engine (OAPE) in small scale specially designed for the portable generating system was presented. The working theory of OAPE was studied, based on which the combustion process was simulated in FLUENT. Then the internal flow field and the variation of temperature and pressure in cylinder were recorded. Results show the flame front is a sphere centered at the spark point. The maximal pressure in power cylinder is 2.13Mpa and maximal pressure in charge cylinder is 0.235Mpa. The work done by power cylinder per cycle is 1.24J, while the charge cylinder consumes 0.22J per cycle.

The characteristics of the flow, the combustion field and NOx emissions in the coal-fired boiler are numerically investigated under different burner layer combination modes for a 660 MW swirling opposed coal-fired utility boiler. The simulation results are relatively close to the actual measured results, with relative errors of less than 10%. The results demonstrate that at the rated load of 5 mills in service, the differences in NOx emissions and carbon contents in fly ash is small in cases of the same-layer burner operating in the front wall and in the rear wall. Stopping upper layer burners enhances air classification and increases the residual time of pulverized coal particles, as compared to stopping the middle layer burners; consequently, the NOx emission and carbon content in the fly ash are reduced by relative values of 9.5% and 9.8%, respectively. In addition, stopping upper layer burners reduces NOx emission and improves combustion efficiency in actual operational conditions.

Through the characteristic experiment, the chromatographic experiments and the thermal analysis experiments, this paper obtains that below 70°C the difference between the curve of CO and CO2 concentration of the organic sample was not significant. The production of CO and CO2 increased rapidly when the temperature rise up to more than 120°C and the maximum production rate of CO and CO2 occurs when the mineral content of organic is 5%. The oxygen consumption of different mineral content in organic samples decreases first and then increases with the increase of temperature. Among them, the maximum oxygen consumption occurs when the mineral content of organic is 5% with the increase of temperature, and the exothermic ox.

Through the investigation on flame-retardant properties of three kinds of inner-spring mattresses, it is found that without flame retardant, the heat release rate (HRR) of spring mattress is up to 600 kW, the concentration of carbon monoxide (CO) and carbon dioxide (CO₂) is 0.08% and 1.5% respectively. Thus, mattress has a very high fire risk. It could cause injuries and deaths through spreading of fire and emitted gases. The mattress with only fabric treated with flame retardant could be ignited, but did not cause the flame spread across a large area, the flame retardant performance satisfied grade B1 in GB 8624-2012. For the mattress which has both fabric and filler being flame retardant, the flame extinguished soon after the ignition sources were removed. Therefore, flame retardant performance for the last mattress was very well.

Since more than a decade, synchrotron-based methods play a major role in combustion chemistry research. This chapter focuses on the use of synchrotron-generated vacuum-ultraviolet (VUV) radiation as an ionization source in mass spectrometric applications. The use of tunable VUV radiation allows for the detection, identification, and quantification of different isomeric structures, thus adding a new dimension to mass spectrometric experiments which has not been previously accessible. In particular, this chapter highlights flame-sampling and kinetic experiments that provided new detailed insights into combustion chemistry processes. Examples are provided that are concerned with soot precursor formation and the combustion of prototypical biofuels.

The combustion and NOx (Nitrogen Oxide) emission characteristics experiment fueled with conventional diesel fuel and four different fuel blends of acidic oil biodiesel (B5, B10, B15 and B20) were conducted in a four-cylinder, electronic controlled high-pressure common-rail, turbocharged diesel engine without any structure modifications. The results showed that operations with acidic oil biodiesel blends had increase in ignition delay, maximum in-cylinder pressure, heat release rate peak in diffusion combustion duration, cumulative heat release and maximum in-cylinder temperature compared with baseline diesel. In addition, the heat release rate peak and in-cylinder pressure rise rate peak in premixed combustion duration of biodiesel blends were decreased and their crank angular positions were lagged obviously. The NOx emission of biodiesel blends increased, especially at high loads.