摘要:

This paper describes an investigation of the dependence of the performance of a propane burning Rijke pulse combustor upon the design of a recently developed tangential injection system. Two injection systems were investigated. In one the fuel and air were rapidly premixed before injection into a duct where most of the combustion occurred. In the second air and fuel were injected separately into the duct. In both cases the pulse combustor could be operated for air/fuel ratios a between 0.5 and 1.8. However, when the reactants were premixed, the combustor pulsations were dominated by the fundamental acoustic mode when α was low, and by its first harmonic when 1.1 < α < 1.6. In contrast, the fundamental acoustic mode dominated for all α when the reactants were injected separately. This suggests that this pulse combustor does not behave like a true Rijke tube, at least while operated in the premixed mode. In addition, exhaust flow analyses revealed that the combustor's combustion efficiency practically equals 100 percent when α is slightly above 1.0 and that NOxemissions equal several ppm for both rich and lean operation.

ISSN:0010-2202    

DOI:10.1080/00102209308935300

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ensemble averaged heat release rates and pressures during pulsating combustion have been measured to better understand the operating characteristics for a twin valveless pulse combustor with two aerodynamic valves. An OH chemiluminescence intensity detection system is applied to determine the periodic variations in heat release. Also, the combusting flows have been visualized using high-speed schlieren photography. Based on the well-known Rayleigh criterion, the varying equivalence ratio and mass flux effects on combustion stability are discussed. Results show that the phase relationship between the heat release rate and the pressure significantly affects the pulse combustion stability and operating frequency. Of particular interest is that the pulsating frequency decreases with increasing equivalence ratio. In addition, the phase difference does not depend on the mass flux, but on the equivalence ratio. This fact indicates that the fuel-air mixing rate is a determinant factor in the phase relationship. The importance of fluid dynamic mixing in pulsating combustion is successfully illustrated by the schlieren observations.

ISSN:0010-2202    

DOI:10.1080/00102209308935301

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The provision of a shrouding duct for an aerovalved pulse combustor is, for some applications, essential in that it permits the combustor to both entrain a secondary airflow and operate with a single air inlet and with a single outlet. Results are summarised representing extensive testing of pulse-combustor shroud ducts showing that the geometrical configuration of a shroud duct is relatively critical to performance. A stagnation pressure gain of 4% of the compressor absolute delivery pressure has been demonstrated on a small, low pressure ratio, gas turbine employing a shrouded, aerovalved, pulse combustor. The loadings of shrouded pulse-combustors are compared with loadings of steady-flow combustors. It is shown that when the core pulse combustor is of the single inlet type, shrouded pulse-combustors have relatively low volumetric loadings although it appears to be possible to ameliorate this by substituting a multiple-inlet pulse-combustor for one of the single inlet type.

ISSN:0010-2202    

DOI:10.1080/00102209308935302

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The performance of gas-fired residential sized twin pulse combustors with two aerodynamic valves for residential heating appliances is discussed. Two injection system are tested. Pre-mixed injection resulted in having better stability of anti-phase operating mode between the two combustion chambers which reduced the noise level less than 50 dB(A). The combustor shows NOxemissions of 25 ppm and a thermal efficiency of 93% over a wide turndown from 1,100 to 6,000 W. At a lower heat input region, the combustor can still operate in the anti-phase mode with fuel supply to only one combustor. It is shown that twin-valveless pulse combustors have the potential for compactness, low noise, and efficient operation over a wide turn down ratio for residential use.

ISSN:0010-2202    

DOI:10.1080/00102209308935303

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper describes theoretical and experimental observations of combustion oscillations produced in a continuously mixed, jet-stirred combustion system. This work is distinct from other investigations of pulse combustion, because it is shown both theoretically and experimentally that combustion oscillations can be produced with a steady supply of fuel and air, requiring no mechanical or aerodynamic valves. The theory is a direct extension of thermal theories of combustion in back-mixed reactors, extended to include the unsteady behavior of the combustor and tailpipe. Because of the demonstrated effect of heat transfer on the oscillations, the name thermal pulse combustion is chosen to describe these oscillations. Effects of friction in the combustor tailpipe, heat loss from the combustion zone, and flow rate, are investigated theoretically. Depending on operating parameters, oscillating combustion, steady flames, or blow-out are all predicted. The effects of finite mixing rate are investigated by specifying a mixing time. Results of the simulation are then favorably compared to laboratory observations of a combustor operating with parameters similar to those used in the numeric model. Laboratory observations confirm that large amplitude oscillations can be produced in a jet-mixed combustor with a steady supply of fuel and air. Laboratory observations show qualitative agreement with predictions, and reasonable quantitative agreement at select conditions.

ISSN:0010-2202    

DOI:10.1080/00102209308935304

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Our previous experiments on the dynamics of laminar premixed flames on a circular porous plug burner have revealed periodic modes with different spatial and temporal characteristics. In this paper representative examples of nonperiodic modes will be presented, and it will be argued that these modes fall into two distinct classes. The method of data analysis used to make this identification will be explained and the experimental conditions that are conducive to observing the flame as a dynamical system will be described in detail. Our results suggest that the techniques of nonlinear dynamics are useful in classifying the periodic and chaotic modes of pulsating and cellular premixed flames but are probably not relevant to diffusion flames.

ISSN:0010-2202    

DOI:10.1080/00102209308935305

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

This paper presents the results of an experimental investigation on the mass transport from a sintered cylinder placed inside the tailpipe of a pulse combustor. Evaporation rates were measured at several different oscillating and mean flow conditions. Also measured were time resolved velocity profiles and high speed laser schlieren video at a single operating condition. Velocity data were taken in front of and behind the cylinder as well as through the cylinder boundary layer, providing quantitative information on the temporal flow behavior. Both the velocity data and schlieren video indicate that the momentum field is non-quasi-steady. Over the range and combination of operating conditions studied, the results show that mass transfer rates are strongly affected by the pressure amplitude, weakly affected by the mean flow Reynolds number and unnoticeably affected by frequency.

ISSN:0010-2202    

DOI:10.1080/00102209308935306

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102209308935307

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A new method for convective heat transfer enhancement is described. The technique involves the use of a pulse combustor to generate a transient jet that impinges on a flat plate. Enhancements in convective heat transfer of a factor of up to 2.5, compared to a steady impinging jet at approximately the same Reynolds number, have been obtained. Heat transfer data for several experimental configurations are presented. Flow field visualizations and theoretical calculations are used to suggest an enhancement mechanism.

ISSN:0010-2202    

DOI:10.1080/00102209308935308

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A preliminary study of the convective transfer rates of scalar quantities in a strongly oscillating free jet (+70 m/s to -50 m/s at 100 Hz generated by a pulse combustor) has been performed. This work is described in two parts: This paper discusses the free jet character, whereas the companion paper discusses the impinging jet characteristics associated with the convective heat transfer rate to a plate normal to the jet axis.

ISSN:0010-2202    

DOI:10.1080/00102209308935309

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor