THREE—DIMENSIONAL GAS TURBINE COMBUSTOR PERFORMANCE MODELING

Numerical analysis of three-dimensional(3-D)two-phase reacting flowfield in an annular combustor wity the dump diffuser is developed in arbitrary curvilinear coordi-nates.Combustor performances are estimated by the em-pirical-analytical desing method.Ths influence of three inlet velocity profiles of the prediffuser and two operating conditions on combustor preformance and flow character-istic is predicted.

Kinetic Study of Sulfur Dioxide Elimination by Limestone through the Lab Scale Circulating Fluidized Bed Combustor

Characteristics of sulfur dioxide emission from coal and petroleum coke combustion were examined in a lab scale circulating fluidized bed (CFB) combustor. The rate constant of the first order rate expression for the absorption SO2 on the CaO surface was similar regardless of the origin of the limestone, the particle size and the initial SO2 concentration. However, the total SO2 absorption capacity was different depending on the origin of the limestone. The breakability of the particle which provides new surface for the reaction seems to play a major role in the absorption characteristics.

Effect of Swirl Preset Vorticity on Combustion Performance of Lobe Nozzle Combustor Chamber

To improve the combustor performance of multi-point injection combustion,lobe nozzle design was applied to the aero-engine model combustor,by presetting the swirl through a certain twisted angle of the edge of the lobe outlet.Numerical simulation in combination with modelling test is used in this paper.The effects of swirl vorticity presetting onto the vortex structure,the characteristics of combustion temperature field,the combustor exit temperature field quality,the combustion efficiency,and the NOx emissions of multi-point injection combustion chamber are investigated.Compared with the conventional vortex flow at the lobe outlet edge,the results of numerical simulation and water modelling test of the swirl vorticity presetting show that the swirl presetting can efficiently enhance the range and intensity of the lobe-induced vorticities.Besides,it can improve the uniformity of the combustion temperature in the combustor chamber,together with the reduced emissions of the pollutant NOx.Moreover,compared with the conventional lobe nozzle chamber,the swirl vortex presetting can effectively improve its combustion performance.The flow simulation test results demonstrate the fluid vortex structure in the combustion chamber and validate the simulation results.

Effect of Hole Size on Flow Structure and Mixing Characteristic in a Multi-Hole Baffled Micro Combustor

Flow structure and mixing properties by the baffle shape are numerically studied for a baffled micro combustor. The baffle shape is changed by various fuel and hole sizes. The numerical simulations based on different geometric conditions are performed by using the Reynolds Stress Model. The fuel-air mixing is greatly affected by flow recirculations. The centrally located flow recirculation has an important role for the entire mixing performance. The results show that this feature depends on the baffle configurations, and the baffle with small air holes represents efficient characters.

OPTIMIZATION OF A PULSE COMBUSTOR FOR A DISPERSE DRYING SYSTEM

The paper summarises the development and optimisation of a valveless pulse combus-tor designed as a heating source for drying in disperse systems. The basic research dealt with changing of the pulse combustor geometry, e. g. the volume of a combustion chamber and tail pipe length to obtain smooth trajectory of pressure oscillations and low emission of toxic substances. The pulse combustion mechanism and existing designs of pulse combustors applied in drying have been presented and analysed. Examples of specific applications of this technique are delivered.

Numerical study of convective heat transfer of a supersonic combustor with varied inlet flow conditions

Characteristics of convective heat transfer of a supersonic model combustor with variable inlet flow conditions were studied by numerical simulation in this paper.The three-dimensional flow and wall heat flux at different air inlet Mach numbers of 2.2,2.8 and 3.2 were studied numerically with Reynolds-averaged Navier-Stokes equations with a shear-stress transport(SST)k-ωturbulence model and a three-step reaction model.Meanwhile,ethylene was chosen as the fuel,and the fixed fuel-to-air equivalence ratio is 0.8 in all cases in this paper.The results of the simulations indicate that wall heat flux distribution of the combustor is very non-uniform with several peaks of wall heat flux at varied locations.For the low inlet Mach number of 2.2,a shock train structure is formed in the isolator,and three peaks of wall heat flux are located respectively on the backward face of the cavity,on the side wall near the fuel injection and on the bottom wall near the injection holes,and a maximum wall heat flux reaches 5.4 MW/m2.For the medium inlet Mach number of 2.8,there exists a much shorter shock structure with three peaks of wall heat flux similar to that of Mach number 2.2.However,as the inlet Mach number increased to 3.2,there is no shock structure upstream of fuel injections,and the combustor flow is in a supersonic mode with different locations and values of wall heat flux peaks.The statistical results of wall heat loading show that the change of total wall heat is not monotonic with the increase of inlet Mach number,and the maximum appears in the case of Mach number being 2.8.Meanwhile,for all the cases,the bottom wall takes up more than 50%of the total heat loading.

Evaluating the Energy Efficiency Performance of a Micro Combustor with and without Heat Recuperation

Micro-combustion research works are motivated by development of portable, autonomous power generators such as the micro TPV with improvement in energy density over batteries. Heat recuperation is a technique which contributes to better energy efficiency performance by recovering heat from the exhaust gas. In this paper, a numerical simulation is carried out to study the impact of incorporating recuperation on the performance of micro modular combustor system. The simulation results have been validated by experiments;achieving close agreement between simulated and experi-mental data. It was observed that the mean wall temperature, radiation power and emitter efficiency markedly improved with the incorporation of a heat recuperator. In addition, 25.8% enhancement of total radiation power and 30.6% emitter efficiency could be realized when the hydrogen air equivalence ratio was 0.9.

Studies of a combined way of flame stability in ramjet combustor

numerical simulation was conducted to study the influence of bleeding. The Euler-Lagrange method was used to investigate the two-phase turbulent combustion flow. Standard k-ε turbulent model was adopted in the continuous phase simulation and particle-trajectory model was adopted in the dispersed phase simulation. The results demonstrates: air bleeding can improve the flow field after the strut and the stability of trapped vortex in the cavity; change of bleeding temperature has little effect on the total pressure recovery coefficient and significant effect on combustion efficiency; When fuel-air ratio changes, the combustor performs better in a lean oil state.

PIV MEASUREMENT FOR SWIRLER FLOW FIELD IN GAS TURBINE COMBUSTOR

The characteristics of swirler flow field, including cold flow field and combustion flow field, in gas tur- bine combustor with two-stage swirler are studied by using particle image velocimetry （PIV）. Velocity compo- nents, fluctuation velocity, Reynolds stress and recirculation zone length are obtained, respectively. Influences of geometric parameter of primary hole, arrangement of primary hole, inlet air temperature, first-stage swirler an- gle and fuel/air ratio on flow field are investigated, respectively. The experimental results reveal that the primary recirculation zone lengths of combustion flow field are shorter than those of cold flow field, and the primary reeir- culation zone lengths decrease with the increase of inlet air temperature and fuel/air ratio. The change of the geo- metric parameter of primary hole casts an important influence on the swirler flow field in two-stage swirler com- bustor.

Experimental Investigation of Hydrocarbon-fuel Ignition in Scramjet Combustor

The direct-connected supersonic combustor experiment is finished for kerosene fuel ignition in H_2/O_2 preheated impulse facility. The entrance parameter of combustor corresponds to scramjet flight Mach number 3.5. Kerosene ignition is realized by using hydrogen as pilot flame. Wall pressure distributions of combustion are measured and flame photographs of ultraviolet ray are got. Experiment indicates that it is very difficult for kerosene fuel to realize self-ignition at low entrance temperature (below 900K) in supersonic combustor. Hydrogen pilot flame is one of the efficient methods for realizing kerosene ignition.

Effects of Lobe Peak-to-Trough Width Ratio on Mixing and Combustion Performance in ATR Combustors

The air-turbo-rocket(ATR)engine is a promising propulsion plant for achieving numerous surface and air launched missile missions.The application of lobed mixer in the ATR combustor can promote the mixing of the fuelrich gas and the air,thus improving the engine performance significantly.The numerical simulation method was conducted to explore the effects of lobe peak-to-trough width ratio on mixing and combustion performance in ATR combustors.Results show that:For a given peak lobe width b1,the combustion efficiency and total pressure loss decrease with the increase of trough lobe width b2;For a given b2,the combustion efficiency and total pressure loss decrease with the increase of b1;The fan-type lobed mixer with smaller b2has a better effect on promoting the combustion efficiency in the region near the ATR combustor center line than that with a pair of parallel side walls.The total pressure recovery coefficient reaches more than 0.99 at the exit of combustor in nonreactive combustion while the total pressure loss reaches more than 4%in the reacting combustion.Compared with the mixing process,more than80%of the total pressure loss is caused during combustion.

EXPERIMENTAL STUDIES ON SWIRLING AND RECIRCULATING TWO-PHASE FLOW FIELD IN A COLD MODEL OF DUAL-INLET SUDDEN-EXPANSION COMBUSTOR

The axial and tangential velocities of gas and particle phases and particle concentration for turbulent swirling and recirculating gas-particle (simulating gas-droplet) flows in a cold model of a dual-inlet sudden-expansion combustor with partially tangential central tubes, proposed by the present authors, were measured by using a 2-D LDV system and a laser optic fiber system combined with a sampling probe. The results show that there are both gas and particle strongly reverse flows and swirling flows in the head part of the combustor. The velocity slip between gas and particle phases is remarkable. The particle concentration is higher near the wall and lower near the axis. There are two peaks in the concentration profiles near the inlet tubes. The above-obtained flow characteristics are favorable to ignition, flame stabilization and combustion. The results can also be used to validate the numerical modeling.

Improved Robust Adaptive Control of a Fluidized Bed Combustor for Sewage Sludge

This paper presents a robust model reference adaptive control scheme to deal with un-certain time delay in the dynamical model of a ?uidized bed combustor for sewage sludge. Thetheoretical analysis and simulation results show that the proposed scheme can guarantee not onlystability and robustness, but also the adaptive decoupling performance of the system.

Syngas Fuel Combustion in Re-circulating Vortex Combustor

This paper presents results on the combustion of syngas fuel in re-circulating vortex combustor. The combustion stability is achieved through the use of cavities in which recirculation zones of hot products generated by the direct injection of fuel and air are created and acting as a continuous source of ignition for the incoming main fuel-air stream. CFD （computational fluid dynamics） analysis was performed in this study to test the combustion performance and emissions from the vortex trapped combustor using synthetic gas or syngas fuel produced from the gasification process. The flame temperature, the flow field and species concentrations inside the vortex trapped combustor were obtained. Several syngas fuels with different fuel compositions （H2, CO, CH4, CO2, N2 and H20） and lower heating values were tested in this study. The changes on the flame temperature and species concentrations inside the combustor, the emissions of NOx, CO, CO2 at the exit of the combustor, the combustor efficiency and the total pressure drop for syngas fuels are presented in this paper. The effect of H2/CO ratio and the mass fraction of each constituent of syngas fuels and hydrogen-methane fuel mixtures on the combustion and emissions performances were investigated.

Experimental study on combustion characteristics of supersonic combustor based on alternating-wedge strut

Acetone Planar Lase-Induced Fluorescence(PLIF)and OH-PLIF were employed to capture the fuel distribution and OH distribution downstream for the supersonic combustor based on the alternating-wedge strut.The combustion establishment process and combustion mode in the combustor under different fuel injection methods and different equivalence ratios were analyzed.Combined with the kerosene-PLIF and OH-PLIF results in the cavity combustor,a comparative analysis was conducted to understand the combustion characteristics and combustion modes between the alternating-wedge strut-based combustor and the cavity-based combustor.The results show that the combustor is in weak combustion mode in the case of low equivalence ratio,and the combustor is in intensive combustion mode in the case of high equivalence ratio.The lower limit of the equivalence ratio of the combustor to maintain the intensive combustion mode varies based on different fuel injection methods.The OH distribution under reacting condition has a strong correlation with the fuel distribution under non-reacting condition.The OH fluorescence signal near the injector is weaker when the fuel distribution is more concentrated.The injector position located at the base of the strut rear has better mixing performance,enabling the combustor to be in intensive combustion mode at a lower equivalence ratio.The combustion reaction in the alternating-wedge strut-based combustor is not necessarily dominated by mass transfer due to the mixing enhancement and premixed zone downstream of strut,while the combustion reaction process in the cavity-based combustor is mainly influenced by mass transfer.

火焰筒内环向多孔径向射流的流场研究

环向径向射流对燃烧室火焰筒内的流场有着重要的影响。本文采用三维标准kε湍流模型详细模拟了燃烧室火焰筒内外的等温流场,给出了火焰筒不同截面位置的轴向速度和径向速度分布。并对数值模拟结果与实验数据进行了比较,结果符合较好,同时还分析了数值模拟结果与实验数据的差异。研究了火焰筒内多孔径向射流的流场特性,并比较了不同环向径向射流流量对火焰筒内流场的影响。研究结果表明:在射流孔附近,火焰筒内轴向速度和径向速度沿径向的梯度增大;而在火焰筒外,轴向速度沿径向的梯度变化不大,径向速度变化较大,但随着流体的流动,火焰筒外径向速度很快趋于均匀。当射流流量增加时,火焰筒内射流孔中心截面的两对称旋涡逐渐增大。

Influence of propagation direction on operation performance of rotating detonation combustor with turbine guide vane

Due to the pressure gain combustion characteristics,the rotating detonation combustor(RDC)can enhance thermodynamic cycle efficiency.Therefore,the performance of gas-turbine engine can be further improved with this combustion technology.In the present study,the RDC operation performance with a turbine guide vane(TGV)is experimentally investigated.Hydrogen and air are used as propellants while hydrogen and air mass flow rate are about 16.1 g/s and 500 g/s and the equivalence ratio is about 1.0.A pre-detonator is used to ignite the mixture.High-frequency dynamic pressure transducers and silicon pressure sensors are employed to measure pressure oscillations and static pressure in the combustion chamber.The experimental results show that the steady propagation of rotating detonation wave(RDW)is observed in the combustion chamber and the mean propagation velocity is above 1650 m/s,reaching over 84%of theoretical Chapman-Jouguet detonation velocity.Clockwise and counterclockwise propagation directions of RDW are obtained.For clockwise propagation direction,the static pressure is about 15%higher in the combustor compared with counterclockwise propagation direction,but the RDW dominant frequency is lower.When the oblique shock wave propagates across the TGV,the pressure oscillations reduces significantly.In addition,as the detonation products flow through the TGV,the static pressure drops up to 32%and 43%for clockwise and counterclockwise propagation process respectively.

Emission Characteristics and Axial Flame Temperature Distribution of a Circumferential Reverse Flow Combustor

In partially premixed combustion of gas turbine, the combustion temperature should be lowed in order to reduce NOx. One solution is lean premixed combustion. However, the problem is that large excess air ratio may make the combustion unstable. A novel combustor with circumferential reverse flow of fuel gas is proposed for settling this problem. A 10 kw furnace is established to test performance of this combustor. Three factors such as primary air ratio, position of secondary air, total excess air ratio are studied. The emission characteristics and axial flame temperature distribution are studied. Basing on experimental results, the axial flame temperature and NOr emission increase with primary air ratio and axial length of second stream, and decrease with total excess air ratio. When the total excess air ratio is larger than 1.05, the combustor presents a lower temperature field and much lower NOx emission （less than 10 ppm）.

Numerical investigations on effects of bluff body in flat plate micro thermo photovoltaic combustor with sudden expansion

In order to reveal combustion characteristics of H_2/air mixture in a micro-combustor with and without bluff body, the effects of inlet velocities, equivalence ratios and bluff body's blockage ratios on the temperature field, pressure of the combustor wall, combustion efficiency and blow-off limit were investigated. The numerical results indicate that the sudden expansion plate micro combustor with bluff body could enhance the turbulent disturbance of the mixed gas in the combustion chamber and the combustion condition is improved. Moreover, a low-speed and high temperature recirculation region was formed between the sudden expansion step and the bluff body so that the high and uniform wall temperature(>1000 K) could be gotten. As a result, it could strengthen the mixing process, prolong the residence time of gas, control the flame position effectively and widen the operation range by the synergistic effect of the bluff body and steps. When the blockage ratio ranged from 0.3 to 0.6, it could be found that the bluff body could play a stabilizing effect and expand combustion blow burning limit, and combustion efficiency firstly was increased with the inlet velocity and equivalence ratio, and then was decreased.

Numerical Analysis of Pollutant Formation in a Liquid Spray Sudden Expansion Combustor

A SUE （sudden expansion） combustor is analyzed using CFD （computational fluid dynamics） methods. Corresponding CO and NOx emissions are computed for various operating conditions of the SUE combustor with a can type geometrical configuration. The goal of this work is to see if the SUE combustor is a viable alternative to conventional combustors which utilize swirlers. It is found the can type combustor＇s NOx emissions are quite low compared to other combustor types but the CO emissions are fairly high. Emissions can be improved by providing better mixing of the fuel and oxidizer in the primary combustion zone. The SUE combustor design needs to be further refined in order for it to be a viable alternative to conventional combustors with swirters.