Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperatur...Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperature,intake pressure of pre-mixture of methane and air,equivalence ratio and location of the built-in adaptor have been investigated.The whole combustion chamber can be divided into two parts,i.e.the upper combustion chamber and the lower combustion chamber,by the built-in adaptor with through hole.Owing to the built-in adaptor with through hole,jet ignition or compression ignition(auto-ignition) phenomena may occur in the lower combustion chamber,which is helpful to getting higher flame propagation velocity,higher combustion peak pressure,low cycle-to-cycle variation and more stable combustion process.展开更多
A fan-stirred combustion chamber is developed for spherically expanding flames,with P and T up to 10 bar and 473 K,respectively.Turbulence characteristics are estimated using particle image velocimetry(PIV)at differen...A fan-stirred combustion chamber is developed for spherically expanding flames,with P and T up to 10 bar and 473 K,respectively.Turbulence characteristics are estimated using particle image velocimetry(PIV)at different initial pressures(P=0.5-5 bar),fan frequencies(ω=0-2000 r/min),and impeller diameters(D=100 and 114 mm).The flame propagation of methanol/air is investigated at different turbulence intensities(u′=0-1.77 m/s)and equivalence ratios(f=0.7-1.5).The results show that u′is independent of P and proportional toω,which can be up to 3.5 m/s at 2000 r/min.L_(T)is independent of P and performs a power regression withωapproximately.The turbulent field is homogeneous and isotropic in the central region of the chamber while the inertial subrange of spatial energy spectrum is more collapsed to-5/3 law at a high Re_(T).Compared to laminar expanding flames,the morphology of turbulent expanding flames is wrinkled and the wrinkles will be finer with the growth of turbulence intensity,consistent with the decline of the Taylor scale and the Kolmogorov scale.The determined S_(L)in the present study is in good agreement with that of previous literature.The S_(L)and S_(T)of methanol/air have a non-monotonic trend with f while peak S_(T)is shifted to the richer side compared to S_(L).This indicates that the newly built turbulent combustion chamber is reliable for further experimental study.展开更多
The effects of excess air coefficients on the combustion characteristics have been experimentally investigated by means of a constant volume combustion bomb.N-butanol was tested as the research fuel at different air-f...The effects of excess air coefficients on the combustion characteristics have been experimentally investigated by means of a constant volume combustion bomb.N-butanol was tested as the research fuel at different air-fuel equivalence ratios.Through the discussion of the combustion pressure,the combustion temperature,accumulated heat release,ignition delay and combustion duration,the effects of the excess air coefficient on combustion characteristics is clarified.Experimental results show that near the theoretical air-fuel ratio,the combustion rate is the fastest accompanying with shorter combustion duration while the combustion pressure and temperature reach the maximum.With increase or decrease of the excess air coefficient the combustion pressure,the temperature and the heat release reduce.Simultaneously,the combustion timing is deferred and the combustion duration becomes longer.展开更多
A two-dimensional mathematical model was developed to investigate the effects of dielectric barrier discharge (DBD) plasma on CH4-air mixtures combustion at atmospheric pressure.Considering the physical and chemical p...A two-dimensional mathematical model was developed to investigate the effects of dielectric barrier discharge (DBD) plasma on CH4-air mixtures combustion at atmospheric pressure.Considering the physical and chemical processes of plasma-assisted combustion (PAC), plasma discharge, heat transfer and turbulent were simultaneously coupled into simulation of PAC. This coupling model consists of DBD kinetic model and methane combustion model. By comparing simulations and the original reference's results, a high-accuracy of this model was validated. In addition, the effects of PAC actuation parameters on combustion characteristics were studied.Numerical simulations show that with an inlet airflow velocity of 10 m s^(-1), a CH_4-air mixtures' equivalence ratio of 0.5, an applied voltage of 10 kV, a frequency of 1200 kHz, compared to conventional combustion (CC), the highest flame temperature rises by 32 K; outlet temperature distribution coefficient drops by 2.3%; the maximum net reaction rate of CH_4 and H_2O increase by 11.22% and 12.80% respectively; the maximum CO emission index decreases by 14.61%; the mixing region turbulence mixing time reduces by 89 ms.展开更多
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 lob...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.展开更多
Silicon carbide (SiC) ceramics is a good structural ceramics material, which have a lot of excellent properties such as superior high-temperature strength up to a temperature of 1 350 ℃, chemical stability, good resi...Silicon carbide (SiC) ceramics is a good structural ceramics material, which have a lot of excellent properties such as superior high-temperature strength up to a temperature of 1 350 ℃, chemical stability, good resistance to thermal shock and high abrasion resistance. The silicon carbide ceramics material has so far been used widely for manufacturing various components such as heat exchangers, rolls, rockets combustion chamber. Sintering of ceramics structural parts have many technological method, the reaction-bonded is one of important sintering technology of ceramics structural parts. The preparation of reaction-bonded silicon carbide (RBSC) is based on a reaction sintering process, whereby a compacted body of α-SiC and carbon (graphite) powders is heated in contact with liquid silicon or gas silicon, which impregnates the body, converting the carbon (graphite) to β-SiC which bonds the original alpha grain. This process is characterized by low temperature and a short time sintering, and being appropriate to the preparation of large size and complex-shaped components, and so on. Besides, during compacting process of reaction sintering, it can maintain a stable dimension of ceramics parts. Therefore, the method of reaction-bonded silicon carbide ceramics has been identified as a technology suitable for producing complicated and highly exact dimensions’ ceramics parts. In this paper, the method of reaction-bonded silicon carbide was applied to the manufacturing of a complex-shaped spacecraft combustion chamber of SiC ceramics. SiC and carbon powder of 4～30 μm were chosen as the raw materials, green compacts containing appropriate wt.% carbon were formed using the mold press method, sintering was performed in a graphite electric furnace under an argon atmosphere. It was introduced in detail that the technological parameters and technological flow of reaction sintering silicon carbide ceramics. At the same time, physical and mechanical experiments such as bending strength, coefficient of thermal expansion, coefficient of thermal conductivity, gastight property, heat resisting property etc. have been carried out. The results demonstrated that spacecraft combustion chamber made from reaction sintering of silicon carbide ceramics is feasible and the results of experiment is satisfactory. The strength of high-temperature structural parts made by reaction sintered SiC varied with silicon content; Under the this article testing condition, the optimum silicon content is 10.5% for the part investigated. The method of reaction sintered SiC ceramics is suitable for manufacturing of complicated spacecraft parts with a working temperature of 1 500 ℃.展开更多
The laws of heat radiation from black body, the laws of Stefan-Boltzmann, Planck, and Wien are fundamental laws of physics. All in all, a little more than 30 fundamental laws of physics, studied by pupils and students...The laws of heat radiation from black body, the laws of Stefan-Boltzmann, Planck, and Wien are fundamental laws of physics. All in all, a little more than 30 fundamental laws of physics, studied by pupils and students worldwide were disclosed. Scientific disclosure of fundamental laws influences mainly power technology, fuel and energy resources saving. In the late XIX century the laws of heat radiation from gas volumes and the laws of Makarov were disclosed. Since the radiation laws from blackbody are fundamental laws of physics, then the laws of heat radiation from gas volumes are fundamental laws of physics. Effect of using laws of heat radiation from gas volumes on fuel saving, reduction of development pressure on the environment in many countries of the world is shown. Calculation results from heat transfer in combustion chamber of gas-turbine plant are described. The torch in a combustion chamber is modeled by cylindrical gas volumes. Fluxes data from the torch and convective fluxes of cooling air are confirmed by measuring data from chamber-wall temperature.展开更多
The cleanliness of gasoline is related to its components and properties.All commercial gasoline builds up deposits on the engine's injector,intake valve and combustion chamber,which can significantly lower the eng...The cleanliness of gasoline is related to its components and properties.All commercial gasoline builds up deposits on the engine's injector,intake valve and combustion chamber,which can significantly lower the engine performance and influence exhaust gas emissions.In this study,the intake valve deposits (IVD) and combustion chamber deposits (CCD) produced from combustion of fuel containing 21 v%—42 v% of aromatics and 8 v%—31 v% of olefins have been studied using Ford engine tests,and the characteristics of deposits were studied by IR spectroscopy,TGA and elemental analysis instrument.The test results have shown that deposit formation depends on the fuel composition,especially the aromatic content in the fuel.It is also observed that there are differences in the values of IVD and CCD measured by IR spectrometry and elemental analyses.展开更多
New designs and adaptation methods are experimented to ensure compliance to ever increasing emissions and efficiency requirements of modern diesel engines. Piston head structure which influences the mixing rate and ti...New designs and adaptation methods are experimented to ensure compliance to ever increasing emissions and efficiency requirements of modern diesel engines. Piston head structure which influences the mixing rate and timing of the fuel within in the combustion chamber is known to enable increase in combustion efficiency and thus lower emission rates. In this paper, computation analysis of flow within a diesel engine cylinder with a twin swirl combustion chamber design throughout a full cycle is presented. The results obtained indicate that the effect of the twin swirl combustion chamber on the cold flow conditions is noteworthy and further analysis together with experiments may reveal information that may prove to be useful in further new designs.展开更多
In the present paper, the effect of the combustion chamber design parameters on the improvement of combustion efficiency (the heat generated inside the combustion chamber) and the enhancement in the pollution rates (h...In the present paper, the effect of the combustion chamber design parameters on the improvement of combustion efficiency (the heat generated inside the combustion chamber) and the enhancement in the pollution rates (heat emissions) from a four-stroke, spark-ignition engine has been studied experimentally and theoretically. Two different programs, Gaseq and Ansys, were used to simulate the effect of the combustion chamber shape, turbulent kinetic energy, intake temperature, intake pressure, parity ratio, compression ratio, and engine speed on reducing specific fuel consumption in the engine, reducing carbon dioxide emissions, and increasing overall engine efficiency. The results showed increasing the intake temperature increased the amount of heat produced in the combustion chamber. This leads to increases in the overall efficiency of the engine, but leads to increasing the carbon dioxide and nitrogen oxide emissions. Increasing the intake pressure has a positive effect on the combustion temperature and pressure, but it has a negative effect on carbon dioxide and nitrogen oxides. Raising the pressure ratio improved the overall efficiency of the engine by increasing the combustion heat, but increasing specific fuel consumption and emissions. Also, increasing the engine speed above the permissible limit has an adverse effect on the spraying speed due to the piston speed being higher than the flame speed, which leads to a reduction in the engine brake torque. An increase in the compression ratio leads to higher fluid pressure and output capacity, but combustion methods occur. An increase in the kinetic energy of the turbulence leads to good combustion. A bowl in a piston has the highest rate of rotation and rotation compared to flat and hemispherical pistons. That is, the design of the cylinder head of this type leads to an improvement in the combustion efficiency and thus the efficiency of the engine.展开更多
The design of the porous medium combustion ( PMC) system which has been applied to chamber reheating furnaces is presented in this study and its main application effects are described in detail. Porous medium material...The design of the porous medium combustion ( PMC) system which has been applied to chamber reheating furnaces is presented in this study and its main application effects are described in detail. Porous medium materials are mainly ceramic ball sucked granular bed porous media and foam ceramic porous media. This study investigates the foam ceramic porous medium and a schematic diagram of the combustion inside this porous medium. The PMC takes a solid medium as its main heat exchange way,thus greatly improving the heat transfer efficiency. Judging from the application effects,the following conclusions have been made: the PMC technology can save more than 25% of energy with remarkable effects; the furnace temperature uniformity can be significantly enhanced; the porous media combustion technology can make the heating furnace design in a more compact way,reduce the time for heating up the furnace, improve the heating rate and reduce energy consumption.展开更多
Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenie...Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.展开更多
Combustion characteristics of three-tube burner in growth chamber for preparation of single crystal by the Verneuil method were investigated,and the effects of nozzle structure and flow rate on the surface temperature...Combustion characteristics of three-tube burner in growth chamber for preparation of single crystal by the Verneuil method were investigated,and the effects of nozzle structure and flow rate on the surface temperature of molten cap were analyzed.The results showed that hydrogen flowed out from the nozzle diffused with inner and outer oxygen,and two flame produced in the center and near the wall of growth chamber.The surface temperature of molten cap were gradually reduced from the center outward.The temperature of molten cap decreased gradually with increasing the nozzle aperture of inner oxygen,and varied slightly with the diameter of hydrogen and outer oxygen nozzle.The temperature of molten cap decreased gradually with increasing the flow rate of inner and outer oxygen,while increased with the flow rate of hydrogen.展开更多
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China (Grant No 32310790200801)
文摘Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperature,intake pressure of pre-mixture of methane and air,equivalence ratio and location of the built-in adaptor have been investigated.The whole combustion chamber can be divided into two parts,i.e.the upper combustion chamber and the lower combustion chamber,by the built-in adaptor with through hole.Owing to the built-in adaptor with through hole,jet ignition or compression ignition(auto-ignition) phenomena may occur in the lower combustion chamber,which is helpful to getting higher flame propagation velocity,higher combustion peak pressure,low cycle-to-cycle variation and more stable combustion process.
基金supported by the National Natural Science Foundation of China(Grant No.52076171).
文摘A fan-stirred combustion chamber is developed for spherically expanding flames,with P and T up to 10 bar and 473 K,respectively.Turbulence characteristics are estimated using particle image velocimetry(PIV)at different initial pressures(P=0.5-5 bar),fan frequencies(ω=0-2000 r/min),and impeller diameters(D=100 and 114 mm).The flame propagation of methanol/air is investigated at different turbulence intensities(u′=0-1.77 m/s)and equivalence ratios(f=0.7-1.5).The results show that u′is independent of P and proportional toω,which can be up to 3.5 m/s at 2000 r/min.L_(T)is independent of P and performs a power regression withωapproximately.The turbulent field is homogeneous and isotropic in the central region of the chamber while the inertial subrange of spatial energy spectrum is more collapsed to-5/3 law at a high Re_(T).Compared to laminar expanding flames,the morphology of turbulent expanding flames is wrinkled and the wrinkles will be finer with the growth of turbulence intensity,consistent with the decline of the Taylor scale and the Kolmogorov scale.The determined S_(L)in the present study is in good agreement with that of previous literature.The S_(L)and S_(T)of methanol/air have a non-monotonic trend with f while peak S_(T)is shifted to the richer side compared to S_(L).This indicates that the newly built turbulent combustion chamber is reliable for further experimental study.
文摘The effects of excess air coefficients on the combustion characteristics have been experimentally investigated by means of a constant volume combustion bomb.N-butanol was tested as the research fuel at different air-fuel equivalence ratios.Through the discussion of the combustion pressure,the combustion temperature,accumulated heat release,ignition delay and combustion duration,the effects of the excess air coefficient on combustion characteristics is clarified.Experimental results show that near the theoretical air-fuel ratio,the combustion rate is the fastest accompanying with shorter combustion duration while the combustion pressure and temperature reach the maximum.With increase or decrease of the excess air coefficient the combustion pressure,the temperature and the heat release reduce.Simultaneously,the combustion timing is deferred and the combustion duration becomes longer.
基金supported by National Natural Science Foundation of China(No.51436008)
文摘A two-dimensional mathematical model was developed to investigate the effects of dielectric barrier discharge (DBD) plasma on CH4-air mixtures combustion at atmospheric pressure.Considering the physical and chemical processes of plasma-assisted combustion (PAC), plasma discharge, heat transfer and turbulent were simultaneously coupled into simulation of PAC. This coupling model consists of DBD kinetic model and methane combustion model. By comparing simulations and the original reference's results, a high-accuracy of this model was validated. In addition, the effects of PAC actuation parameters on combustion characteristics were studied.Numerical simulations show that with an inlet airflow velocity of 10 m s^(-1), a CH_4-air mixtures' equivalence ratio of 0.5, an applied voltage of 10 kV, a frequency of 1200 kHz, compared to conventional combustion (CC), the highest flame temperature rises by 32 K; outlet temperature distribution coefficient drops by 2.3%; the maximum net reaction rate of CH_4 and H_2O increase by 11.22% and 12.80% respectively; the maximum CO emission index decreases by 14.61%; the mixing region turbulence mixing time reduces by 89 ms.
基金supported by the Natural Science Fund of Liaoning Province Project (No. 201602566)
文摘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.
文摘Silicon carbide (SiC) ceramics is a good structural ceramics material, which have a lot of excellent properties such as superior high-temperature strength up to a temperature of 1 350 ℃, chemical stability, good resistance to thermal shock and high abrasion resistance. The silicon carbide ceramics material has so far been used widely for manufacturing various components such as heat exchangers, rolls, rockets combustion chamber. Sintering of ceramics structural parts have many technological method, the reaction-bonded is one of important sintering technology of ceramics structural parts. The preparation of reaction-bonded silicon carbide (RBSC) is based on a reaction sintering process, whereby a compacted body of α-SiC and carbon (graphite) powders is heated in contact with liquid silicon or gas silicon, which impregnates the body, converting the carbon (graphite) to β-SiC which bonds the original alpha grain. This process is characterized by low temperature and a short time sintering, and being appropriate to the preparation of large size and complex-shaped components, and so on. Besides, during compacting process of reaction sintering, it can maintain a stable dimension of ceramics parts. Therefore, the method of reaction-bonded silicon carbide ceramics has been identified as a technology suitable for producing complicated and highly exact dimensions’ ceramics parts. In this paper, the method of reaction-bonded silicon carbide was applied to the manufacturing of a complex-shaped spacecraft combustion chamber of SiC ceramics. SiC and carbon powder of 4～30 μm were chosen as the raw materials, green compacts containing appropriate wt.% carbon were formed using the mold press method, sintering was performed in a graphite electric furnace under an argon atmosphere. It was introduced in detail that the technological parameters and technological flow of reaction sintering silicon carbide ceramics. At the same time, physical and mechanical experiments such as bending strength, coefficient of thermal expansion, coefficient of thermal conductivity, gastight property, heat resisting property etc. have been carried out. The results demonstrated that spacecraft combustion chamber made from reaction sintering of silicon carbide ceramics is feasible and the results of experiment is satisfactory. The strength of high-temperature structural parts made by reaction sintered SiC varied with silicon content; Under the this article testing condition, the optimum silicon content is 10.5% for the part investigated. The method of reaction sintered SiC ceramics is suitable for manufacturing of complicated spacecraft parts with a working temperature of 1 500 ℃.
文摘The laws of heat radiation from black body, the laws of Stefan-Boltzmann, Planck, and Wien are fundamental laws of physics. All in all, a little more than 30 fundamental laws of physics, studied by pupils and students worldwide were disclosed. Scientific disclosure of fundamental laws influences mainly power technology, fuel and energy resources saving. In the late XIX century the laws of heat radiation from gas volumes and the laws of Makarov were disclosed. Since the radiation laws from blackbody are fundamental laws of physics, then the laws of heat radiation from gas volumes are fundamental laws of physics. Effect of using laws of heat radiation from gas volumes on fuel saving, reduction of development pressure on the environment in many countries of the world is shown. Calculation results from heat transfer in combustion chamber of gas-turbine plant are described. The torch in a combustion chamber is modeled by cylindrical gas volumes. Fluxes data from the torch and convective fluxes of cooling air are confirmed by measuring data from chamber-wall temperature.
基金the PetroChina Corporation Research and Development Project (06-03B-01-01) for financial support
文摘The cleanliness of gasoline is related to its components and properties.All commercial gasoline builds up deposits on the engine's injector,intake valve and combustion chamber,which can significantly lower the engine performance and influence exhaust gas emissions.In this study,the intake valve deposits (IVD) and combustion chamber deposits (CCD) produced from combustion of fuel containing 21 v%—42 v% of aromatics and 8 v%—31 v% of olefins have been studied using Ford engine tests,and the characteristics of deposits were studied by IR spectroscopy,TGA and elemental analysis instrument.The test results have shown that deposit formation depends on the fuel composition,especially the aromatic content in the fuel.It is also observed that there are differences in the values of IVD and CCD measured by IR spectrometry and elemental analyses.
文摘New designs and adaptation methods are experimented to ensure compliance to ever increasing emissions and efficiency requirements of modern diesel engines. Piston head structure which influences the mixing rate and timing of the fuel within in the combustion chamber is known to enable increase in combustion efficiency and thus lower emission rates. In this paper, computation analysis of flow within a diesel engine cylinder with a twin swirl combustion chamber design throughout a full cycle is presented. The results obtained indicate that the effect of the twin swirl combustion chamber on the cold flow conditions is noteworthy and further analysis together with experiments may reveal information that may prove to be useful in further new designs.
文摘In the present paper, the effect of the combustion chamber design parameters on the improvement of combustion efficiency (the heat generated inside the combustion chamber) and the enhancement in the pollution rates (heat emissions) from a four-stroke, spark-ignition engine has been studied experimentally and theoretically. Two different programs, Gaseq and Ansys, were used to simulate the effect of the combustion chamber shape, turbulent kinetic energy, intake temperature, intake pressure, parity ratio, compression ratio, and engine speed on reducing specific fuel consumption in the engine, reducing carbon dioxide emissions, and increasing overall engine efficiency. The results showed increasing the intake temperature increased the amount of heat produced in the combustion chamber. This leads to increases in the overall efficiency of the engine, but leads to increasing the carbon dioxide and nitrogen oxide emissions. Increasing the intake pressure has a positive effect on the combustion temperature and pressure, but it has a negative effect on carbon dioxide and nitrogen oxides. Raising the pressure ratio improved the overall efficiency of the engine by increasing the combustion heat, but increasing specific fuel consumption and emissions. Also, increasing the engine speed above the permissible limit has an adverse effect on the spraying speed due to the piston speed being higher than the flame speed, which leads to a reduction in the engine brake torque. An increase in the compression ratio leads to higher fluid pressure and output capacity, but combustion methods occur. An increase in the kinetic energy of the turbulence leads to good combustion. A bowl in a piston has the highest rate of rotation and rotation compared to flat and hemispherical pistons. That is, the design of the cylinder head of this type leads to an improvement in the combustion efficiency and thus the efficiency of the engine.
文摘The design of the porous medium combustion ( PMC) system which has been applied to chamber reheating furnaces is presented in this study and its main application effects are described in detail. Porous medium materials are mainly ceramic ball sucked granular bed porous media and foam ceramic porous media. This study investigates the foam ceramic porous medium and a schematic diagram of the combustion inside this porous medium. The PMC takes a solid medium as its main heat exchange way,thus greatly improving the heat transfer efficiency. Judging from the application effects,the following conclusions have been made: the PMC technology can save more than 25% of energy with remarkable effects; the furnace temperature uniformity can be significantly enhanced; the porous media combustion technology can make the heating furnace design in a more compact way,reduce the time for heating up the furnace, improve the heating rate and reduce energy consumption.
文摘Current portable power generators are mainly based on internal combustion engine since they present higher values of efficiency comparing to other engines;the main reason why internal combustion engine is not convenient for micro power generation (5 - 30 kW) is because of their heaviness. Micro and ultra micro gas turbine devices, based on a micro compressor and a micro turbine installed on the same shaft, are more suitable for this scope for several reasons. Micro turbine systems have many advantages over reciprocating engine generators, such as higher power density (with respect to size and weight), extremely low emissions and few, or just one, moving part. Those designed with foil bearings and air-cooling operate without oil, coolants or other hazardous materials. Micro turbines also have the advantage of having the majority of their waste heat contained in their relatively high temperature exhaust. Micro turbines offer several potential advantages compared to other technologies for small-scale power generation, including: a small number of moving parts, compact size, lightweight, greater efficiency, lower emissions, lower electricity costs, and opportunities to utilize waste fuels. The object of this study is the experimental tests on a stand-alone gas turbine device with a pre-heated combustion chamber (CC), to validate the fuel consumption reduction, compared to an actual and commercial device, used on air models.
基金This work was supported by the Projects of National Natural Science Foundation of China,No.51872033 and No.51732007by the Project of Dalian Natural Science Foundation,No.2019J12GX044by the Project of Natural Science Foundation of Liaoning Province,No.2019-ZD-0572.
文摘Combustion characteristics of three-tube burner in growth chamber for preparation of single crystal by the Verneuil method were investigated,and the effects of nozzle structure and flow rate on the surface temperature of molten cap were analyzed.The results showed that hydrogen flowed out from the nozzle diffused with inner and outer oxygen,and two flame produced in the center and near the wall of growth chamber.The surface temperature of molten cap were gradually reduced from the center outward.The temperature of molten cap decreased gradually with increasing the nozzle aperture of inner oxygen,and varied slightly with the diameter of hydrogen and outer oxygen nozzle.The temperature of molten cap decreased gradually with increasing the flow rate of inner and outer oxygen,while increased with the flow rate of hydrogen.
