Burning Velocities, Markstein Lengths, and Flame Quenching for Spherical Methane-Air Flames: A Computational Study

Advances and challenges in laminar flame experiments and implications for combustion chemistry

A comprehensive review of measurements and data analysis of laminar burning velocities for various fuel+air mixtures

Molecular transport effects on turbulent flame propagation and structure

Flame stretch interactions of laminar premixed hydrogen/air flames at normal temperature and pressure

The complex three-dimensional flowfield produced by secondary injection of hot gases in a rocket nozzle for thrust vector control is analyzed by solving unsteady three-dimensional Euler equations with appropriate boundary conditions. Various system performance parameters like secondary jet amplification factor and axial thrust augmentation are deduced by integrating the nozzle wall pressure distributions obtained as part of the flowfield solution and compared with measurements taken in actual static tests. The agreement is good within the practical range of secondary injectant flow rates for thrust vector control applications.

Analysis of performance of a hot gas injection thrust vector control system

Stretch effects extracted from inwardly and outwardly propagating spherical premixed flames

This paper examines afresh features of ammonium-perchlorate (AP) combustion. Here an AP model, which predicts most experimental observations, is proposed. The one-dimensional aero-thermo-chemical field is captured through the solution of mass, energy, and species conservation equations. The unsteady one-dimensional phase heat transfer accounting for regression is solved for in the condensed phase. The uncertain parameters for AP pyrolysis, gas-phase reaction, and extent of surface exothermicity are chosen so that the most certain of the measured parameters of AP combustion, namely, pressure index of stable combustion (0.77 between 2 and 7 MPa), initial temperature sensitivity of burn rate, σp (about 0.0021 to 0.0015 K −1 ), range of surface temperatures measured and suggested in several studies (∼850 to 875 K), and low-pressure deflagration limit (LPDL) at 300 K (∼2 MPa), are correctly predicted. The results obtained show the pressure index of AP combustion to be 0.77 and σp to be 0.0024‐0.0023 K−1. The LPDL is caused by a combination of loss of liquid layer and transient conduction into the condensed phase and not by heat loss.

Revisiting the Modeling of Ammonium-Perchlorate Combustion: Development of an Unsteady Model

This paper is concerned with a study of an operator split scheme and unsplit scheme for the computation of adiabatic freely propagating one-dimensional premixed flames. The study uses unsteady method for both split and unsplit schemes employing implicit chemistry and explicit diffusion, a combination which is stable and convergent. Solution scheme is not sensitive to the initial starting estimate and provides steady state even with straight line profiles (far from steady state) in small number of time steps. Two systems H2-Air and H2-NO (involving complex nitrogen chemistry) are considered in presentinvestigation. Careful comparison shows that the operator split approach is slightly superior than the unsplit when chemistry becomes complex. Comparison of computational times with those of existing steady and unsteady methods seems to suggest that the method employing implicit-explicit algorithm is very efficient and robust.

Time Dependent Operator-split and Unsplit Schemes for One Dimensional Premixed Flames

Bamboo is a fast growing fibrous plant grown in abundance in India. As a consequence to bamboo flowering, it becomes imperative to find additional ways and means of using bamboo within a short span of time. If not put to immediate use the one other way is to extend the shelf life of the bamboo. The current practices of bamboo usage can only consume a part of the excess bamboo generated thereby opening possibility for other usages. Torrefaction of bamboo is seen as one such possibility that apart from energy densification makes the product resistant to fungal attack. Under one of funded project, torrefaction of bamboo has been successfully attempted on a kiln of I ton/day input capacity. Prior to conceiving the design of the kiln, basic studies have been conducted between 180 and 350°C temperature. Furthermore torrefied bamboo has been characterized for calorific value and elemental balance. Based on the analysis it is found that there is an enhancement in energy density by 20% against raw bamboo between torrefaction temperatures of 250 and 260°C. This 1 Ton/hour kiln has completed successful trials at the laboratory is expected to be located in an industry.

PJ Paul

Papers

Analysis of performance of a hot gas injection thrust vector control system

Stretch effects extracted from inwardly and outwardly propagating spherical premixed flames

Revisiting the Modeling of Ammonium-Perchlorate Combustion: Development of an Unsteady Model

Time Dependent Operator-split and Unsplit Schemes for One Dimensional Premixed Flames

Torrefaction of bamboo