The effect of Fe_(2)O_(3) on the formation of micro glass beads(MGBs)under air staged combustion was studied.The experimental temperature was 1450℃,and Hegang bituminous coal was used as the experimental object.X⁃ray...The effect of Fe_(2)O_(3) on the formation of micro glass beads(MGBs)under air staged combustion was studied.The experimental temperature was 1450℃,and Hegang bituminous coal was used as the experimental object.X⁃ray diffractometer(XRD),ash fusion tester,viscosity formula and scanning electron microscopy(SEM)were used to analyze the fly ash.Nano Measurer 1.2 software was used to measure the diameter of MGBs.The results showed that with the increase of Fe_(2)O_(3) in Hegang coal,the glass phase in fly ash first increased and then decreased.When the amount of Fe_(2)O_(3) was 15%,the content of the glass phase was the highest,which was 51.26%.The ash melting point first decreased and then increased,while the viscosity gradually decreased and the particles gradually became spherical.With the increase of Fe_(2)O_(3),the proportion of MGBs with particle size less than 10μm increased gradually.From the above results,it can be concluded that the addition of Fe_(2)O_(3) is conducive to the formation of MGBs and the reduction of particle size.展开更多
The purpose of this paper is to present the flow field in the 300MW tangential firing utility boiler that used the Low NOx Concentric Firing System （LNCFS）. Using the method of cold isothermal simulation ensures the...The purpose of this paper is to present the flow field in the 300MW tangential firing utility boiler that used the Low NOx Concentric Firing System （LNCFS）. Using the method of cold isothermal simulation ensures the geometric and boundary condition similarity. At the same time the condition of self-modeling is met. The experimental results show that the mixture of primary air and secondary air becomes slower, the average turbulence magnitude the relative diameter of the tangential firing enlarges of the main combustion zone becomes less and when the secondary air deflection angle increases When the velocity pressure ratio of the secondary air to the primary air （p2/p1） enlarges, the mixture of the secondary air and the primary air becomes stronger, the average turbulence magnitude of the main combustion zone increases, and the relative diameter of the tangential firing becomes larger. Because the over fire air （OFA） laid out near the wall has a powerful penetration, the relative diameter of the tangential firing on the section of the OFA is very little, but the average turbulence magnitude is great. When the velocity pressure ratio of the OFA to the primary air POFA/p1 increases, the relative diameter of the tangential firing on the section of the OFA grows little, the average turbulence magnitude becomes larger and the penetration of the OFA becomes more powerful.展开更多
Supersonic model combustors using two-stage injections of supercritical kerosene were experimentally investigated in both Mach 2.5 and 3.0 model combustors with stagnation temperatures of approximately 1,750 K. Superc...Supersonic model combustors using two-stage injections of supercritical kerosene were experimentally investigated in both Mach 2.5 and 3.0 model combustors with stagnation temperatures of approximately 1,750 K. Supercritical kerosene of approximately 760 K was prepared and injected in the overall equivalence ratio range of 0.5-1.46. Two pairs of integrated injector/flameholder cavity modules in tandem were used to facilitate fuel-air mixing and stable combustion. For single-stage fuel injection at an upstream location, it was found that the boundary layer separation could propagate into the isolator with increasing fuel equivalence ratio due to excessive local heat release, which in turns changed the entry airflow conditions. Moving the fuel injection to a further downstream location could alleviate the problem, while it would result in a decrease in combustion efficiency due to shorter fuel residence time. With two-stage fuel injections the overall combustor performance was shown to be improved and kerosene injections at fuel rich conditions could be reached without the upstream propagation of the boundary layer separation into the isolator. Furthermore, effects of the entry Mach number and pilot hydrogen on combustion performance were also studied.展开更多
This paper presents an experimental investigation of the turbulent reacting flow in a swirl combustor with staged air injection. The air injected into the combustor is composed of the primary swirling jet and the seco...This paper presents an experimental investigation of the turbulent reacting flow in a swirl combustor with staged air injection. The air injected into the combustor is composed of the primary swirling jet and the secon-dary non-swirling jet. A three dimension-laser particle dynamic analyzer (PDA) was employed to measure the in-stantaneous gas velocity. The probability density functions (PDF) for the instantaneous gas axial and tangential ve-locities at each measuring location, as well as the radial profiles of the root mean square of fluctuating gas axial and tangential velocities and the second-order moment for the fluctuating gas axial and tangential velocities are ob-tained. The measured results delineate the turbulence properties of the swirling reacting flow under the conditions of staged combustion.展开更多
In order to study the effect of two-stage injection on two-stroke diesel engines, a well characterized research engine equipped with electronically controlled common rail system and scavenging system was constructed. ...In order to study the effect of two-stage injection on two-stroke diesel engines, a well characterized research engine equipped with electronically controlled common rail system and scavenging system was constructed. Through analysis of combustion and emissions, two-stage injection shows its advantages. Compared with the standard injection, it produces less emissions, while compared with single early injection, it expands engine operation range. Further experiments were carried out to study the influence of several injection control parameters on two-stage injection. The fuel in the first injection is used for forming homogeneous mixture. The fuel in the second injection keeps combustion, and it is the main source of smoke emissions. NO_x is formed in both combustion process caused by these two injections, and there is an optimum fuel allocation ration to produce minimum NO_x. The cylinder pressure decreases, and the combustion is depressed with the increasing of scavenging pressure. By optimizing the injection control parameters of two-stage injection, NO_x and smoke can be reduced beyond 30% simultaneously.展开更多
The study focused on the effects of the interaction between axial and radial secondary air and the reductive intensity in reduction region on combustion characteristics and NO_(x) emission in a 30 kW preheating combus...The study focused on the effects of the interaction between axial and radial secondary air and the reductive intensity in reduction region on combustion characteristics and NO_(x) emission in a 30 kW preheating combustion system.The results revealed that the interaction and reductive intensity influenced the combustion in the down-fired combustor(DFC) and NO_(x) emission greatly.For the temperature distribution,the interaction caused the position of the main combustion region to shift down as R_(2-12)(ratio of axial secondary air flow to radial secondary air flow) decreased or λ_(2)(total secondary air ratio) increased,and there was the interplay between both of their effects.As R_(3-12)(ratio of first-staged tertiary air flow to second-staged tertiary air flow)increased,the decrease in the reductive intensity also caused the above phenomenon,and the peak temperature increased in this region.For the NO_(x) emission,the interaction affected the NO_(x) reduction adversely when λ_(2) or R_(2-12) was higher,and the range of this effect was larger,so that the NO_x emission increased obviously as they increased.The decrease in the reductive intensity caused the NO_(x) emission increased under the homogeneous reduction mechanism,while was unchanged at a high level under the heterogeneous reduction mechanism.For the combustion efficiency,the interaction improved the combustion efficiency as λ_(2) increased when R_(2-12) was lower,while reduced it as λ_(2) increased excessively when R_(2-12) was higher.The proper decrease in the reductive intensity caused the combustion efficiency increased obviously,while was hardly improved further when the intensity decreased excessively.In this study,the lowest NO_(x) emission was only 41.75 mg/m^(3) without sacrificing the combustion efficiency by optimizing the interaction and reductive intensity.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">Sensitivity analysis of neural networks to input variation is an important research area as it goes some way to addr...<div style="text-align:justify;"> <span style="font-family:Verdana;">Sensitivity analysis of neural networks to input variation is an important research area as it goes some way to addressing the criticisms of their black-box behaviour. Such analysis of RBFNs for hydrological modelling has previously been limited to exploring perturbations to both inputs and connecting weights. In this paper, the backward chaining rule that has been used for sensitivity analysis of MLPs, is applied to RBFNs and it is shown how such analysis can provide insight into physical relationships. A trigonometric example is first presented to show the effectiveness and accuracy of this approach for first order derivatives alongside a comparison of the results with an equivalent MLP. The paper presents a real-world application in the modelling of river stage shows the importance of such approaches helping to justify and select such models.</span> </div>展开更多
基金Sponsored by the Natural Science Foundation of Shandong Province (Grant No. ZR2020ME190)the Shandong Key Research and Development Plan (Grant No. 2019GSF109004)。
文摘The effect of Fe_(2)O_(3) on the formation of micro glass beads(MGBs)under air staged combustion was studied.The experimental temperature was 1450℃,and Hegang bituminous coal was used as the experimental object.X⁃ray diffractometer(XRD),ash fusion tester,viscosity formula and scanning electron microscopy(SEM)were used to analyze the fly ash.Nano Measurer 1.2 software was used to measure the diameter of MGBs.The results showed that with the increase of Fe_(2)O_(3) in Hegang coal,the glass phase in fly ash first increased and then decreased.When the amount of Fe_(2)O_(3) was 15%,the content of the glass phase was the highest,which was 51.26%.The ash melting point first decreased and then increased,while the viscosity gradually decreased and the particles gradually became spherical.With the increase of Fe_(2)O_(3),the proportion of MGBs with particle size less than 10μm increased gradually.From the above results,it can be concluded that the addition of Fe_(2)O_(3) is conducive to the formation of MGBs and the reduction of particle size.
基金This paper is supported by National Natural Science Foundation of China under Grant No50476050Natural Science Basic Research Plan in Shaanxi Province of China under Grant No2005E221
文摘The purpose of this paper is to present the flow field in the 300MW tangential firing utility boiler that used the Low NOx Concentric Firing System （LNCFS）. Using the method of cold isothermal simulation ensures the geometric and boundary condition similarity. At the same time the condition of self-modeling is met. The experimental results show that the mixture of primary air and secondary air becomes slower, the average turbulence magnitude the relative diameter of the tangential firing enlarges of the main combustion zone becomes less and when the secondary air deflection angle increases When the velocity pressure ratio of the secondary air to the primary air （p2/p1） enlarges, the mixture of the secondary air and the primary air becomes stronger, the average turbulence magnitude of the main combustion zone increases, and the relative diameter of the tangential firing becomes larger. Because the over fire air （OFA） laid out near the wall has a powerful penetration, the relative diameter of the tangential firing on the section of the OFA is very little, but the average turbulence magnitude is great. When the velocity pressure ratio of the OFA to the primary air POFA/p1 increases, the relative diameter of the tangential firing on the section of the OFA grows little, the average turbulence magnitude becomes larger and the penetration of the OFA becomes more powerful.
基金supported by the National Natural Science Foundation of China (10672169, 10621202)
文摘Supersonic model combustors using two-stage injections of supercritical kerosene were experimentally investigated in both Mach 2.5 and 3.0 model combustors with stagnation temperatures of approximately 1,750 K. Supercritical kerosene of approximately 760 K was prepared and injected in the overall equivalence ratio range of 0.5-1.46. Two pairs of integrated injector/flameholder cavity modules in tandem were used to facilitate fuel-air mixing and stable combustion. For single-stage fuel injection at an upstream location, it was found that the boundary layer separation could propagate into the isolator with increasing fuel equivalence ratio due to excessive local heat release, which in turns changed the entry airflow conditions. Moving the fuel injection to a further downstream location could alleviate the problem, while it would result in a decrease in combustion efficiency due to shorter fuel residence time. With two-stage fuel injections the overall combustor performance was shown to be improved and kerosene injections at fuel rich conditions could be reached without the upstream propagation of the boundary layer separation into the isolator. Furthermore, effects of the entry Mach number and pilot hydrogen on combustion performance were also studied.
基金Supported jointly by the National Natural Science Foundation of China (No.59806006) and the Laboratory Open Fund ofTsinghua University.
文摘This paper presents an experimental investigation of the turbulent reacting flow in a swirl combustor with staged air injection. The air injected into the combustor is composed of the primary swirling jet and the secon-dary non-swirling jet. A three dimension-laser particle dynamic analyzer (PDA) was employed to measure the in-stantaneous gas velocity. The probability density functions (PDF) for the instantaneous gas axial and tangential ve-locities at each measuring location, as well as the radial profiles of the root mean square of fluctuating gas axial and tangential velocities and the second-order moment for the fluctuating gas axial and tangential velocities are ob-tained. The measured results delineate the turbulence properties of the swirling reacting flow under the conditions of staged combustion.
基金The National Basic Research Program of China(973 Program)(No.2001CB209208)The National Science Foundation of China(No.50136040)
文摘In order to study the effect of two-stage injection on two-stroke diesel engines, a well characterized research engine equipped with electronically controlled common rail system and scavenging system was constructed. Through analysis of combustion and emissions, two-stage injection shows its advantages. Compared with the standard injection, it produces less emissions, while compared with single early injection, it expands engine operation range. Further experiments were carried out to study the influence of several injection control parameters on two-stage injection. The fuel in the first injection is used for forming homogeneous mixture. The fuel in the second injection keeps combustion, and it is the main source of smoke emissions. NO_x is formed in both combustion process caused by these two injections, and there is an optimum fuel allocation ration to produce minimum NO_x. The cylinder pressure decreases, and the combustion is depressed with the increasing of scavenging pressure. By optimizing the injection control parameters of two-stage injection, NO_x and smoke can be reduced beyond 30% simultaneously.
基金Youth Innovation Promotion Association,CAS (2019148)CAS Project for Young Scientists in Basic Research (YSBR-028)the National Natural Science Foundation of China (No.52006233) are gratefully acknowledged。
文摘The study focused on the effects of the interaction between axial and radial secondary air and the reductive intensity in reduction region on combustion characteristics and NO_(x) emission in a 30 kW preheating combustion system.The results revealed that the interaction and reductive intensity influenced the combustion in the down-fired combustor(DFC) and NO_(x) emission greatly.For the temperature distribution,the interaction caused the position of the main combustion region to shift down as R_(2-12)(ratio of axial secondary air flow to radial secondary air flow) decreased or λ_(2)(total secondary air ratio) increased,and there was the interplay between both of their effects.As R_(3-12)(ratio of first-staged tertiary air flow to second-staged tertiary air flow)increased,the decrease in the reductive intensity also caused the above phenomenon,and the peak temperature increased in this region.For the NO_(x) emission,the interaction affected the NO_(x) reduction adversely when λ_(2) or R_(2-12) was higher,and the range of this effect was larger,so that the NO_x emission increased obviously as they increased.The decrease in the reductive intensity caused the NO_(x) emission increased under the homogeneous reduction mechanism,while was unchanged at a high level under the heterogeneous reduction mechanism.For the combustion efficiency,the interaction improved the combustion efficiency as λ_(2) increased when R_(2-12) was lower,while reduced it as λ_(2) increased excessively when R_(2-12) was higher.The proper decrease in the reductive intensity caused the combustion efficiency increased obviously,while was hardly improved further when the intensity decreased excessively.In this study,the lowest NO_(x) emission was only 41.75 mg/m^(3) without sacrificing the combustion efficiency by optimizing the interaction and reductive intensity.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">Sensitivity analysis of neural networks to input variation is an important research area as it goes some way to addressing the criticisms of their black-box behaviour. Such analysis of RBFNs for hydrological modelling has previously been limited to exploring perturbations to both inputs and connecting weights. In this paper, the backward chaining rule that has been used for sensitivity analysis of MLPs, is applied to RBFNs and it is shown how such analysis can provide insight into physical relationships. A trigonometric example is first presented to show the effectiveness and accuracy of this approach for first order derivatives alongside a comparison of the results with an equivalent MLP. The paper presents a real-world application in the modelling of river stage shows the importance of such approaches helping to justify and select such models.</span> </div>
基金This work was supported by the National Natural Science Foundation of China(No.52206222,No.22227901)State Key Laboratory of Laser Interaction with Matter Foundation(SKLLIM2009).
