Pulse combustor modeling demonstration of the importance of characteristic times

Abstract

A numerical model has been developed to study the sensitivity of a pulse combustor's performance to changes in the relative timing between several of the dominant physical processes. The model is used to demonstrate the importance of the characteristic times associated with acoustics, fluid mixing, and chemical kinetics, which have been identified from both theoretical and experimental evidence. The combination of submodels for acoustics, injection, and combustion produces a pulse combustor model that is dynamic in that it fully couples the injection and mixing processes to the acoustic waves. Comparisons of simulations with experimental results show good agreement, verifying the model over a wide range of operating conditions. Because the model provides more control of the dominant processes than can be obtained in experiments, the parametric study establishes the cause-effect relation between the characteristic times and the resulting combustor performance.

Perturbation analysis of self-sustained oscillations in a pulse combustion model

“…The basic pulse combustor consists of a set of intake valves for air and fuel, a combustion chamber, a tailpipe, and, Table 1a. perhaps, a decoupling chamber. Combustion products are exhausted through the tailpipe while the flow field in the tailpipe of a typical Helmholtz pulse combustor behaves like a solid plug flow which moves under the influence of the oscillating pressure field in the combustion chamber; this tailpipe flow field has been discussed, at length, in [10][11][12][13].…”

Studies on Pulse Jet Engine by Wind Tunnel Testing

“…The oscillation of the gas column in the pipe of a pulse jet engine is driven by the combustion as long as the charging of fresh mixture through the inlet is attenuated (Barr et al, 1990;Zeutzius et al, 1998a,b). Not only the charging but also the strength of the subsequent compression of the charged mixture by the gas column in the tailpipe depends on this pressure drop in the combustion chamber.…”

“…Last wind tunnel tests with pulse jet engines were done in Germany by Schmidt (1950) and Staab (1954), but most of their results were getting lost during the war time. In addition, contemporary work (Barr et al, 1990) concentrates to pulse combustors as gas generators. Therefore, present investigations are focused to the wind tunnel testing and the development of an active control system for pulse jet engines to extend their operating range including ram-and rocket-mode.…”

Acoustic analysis of a liquefied petroleum gas-fired pulse combustor

“…In the numerical model developed by Barr et al. [7], it was mentioned that the acoustic time scale could be either changed by varying the tail pipe length or temperature distribution in the tail pipe and was also demonstrated that stronger pulsations could be obtained by increasing the acoustic time scale. The study presented Margolis [8] is based on the effect of nonlinear dynamics controlling acoustic mode interactions in a typical combustion-driven device and it was claimed that the method developed can be applied to other combustion driven acoustic problems, such as those in rocket motors.…”

“…A few numerical and analytical model have been developed to investigate the acoustic Characteristics of gas-fired pulse combustor Barr et al and Margolis [7,8]. In the numerical model developed by Barr et al.…”