Interaction flow field of the sonic air jet through diamond shaped orifices at different incidence angles （10 degrees, 27.5 degrees, 45 degrees and 90 degrees） and total pressures （0.10 MPa and 0. 46 MPa） with a M...Interaction flow field of the sonic air jet through diamond shaped orifices at different incidence angles （10 degrees, 27.5 degrees, 45 degrees and 90 degrees） and total pressures （0.10 MPa and 0. 46 MPa） with a Mach 5.0 freestream was studied experimentally. A 90 degrees circular injector was examined for comparison. Crosssection Mach number contours were acquired by a Pitot-cone five-hole pressure probe. The results indicate that the low Mach semicircular region close to the wall is the wake region. The boundary layer thinning is in the areas adjacent to the wake. For the detached case, the interaction shock extends further into the freestream, and the shock shape has more curvature, also the low-Mach upwash region is larger. The vortices of the plume and the height of the jet interaction shock increase with increasing incidence angle and jet pressure. 90 degrees diamond and circular injector have stronger plume vorticity, and for the circular injector low-Mach region is smaller than that for the diamond injector. Tapered ramp increases the plume vorticity, and the double ramp reduces the level of vorticity. The three-dimensional interaction shock shape was modeled from the surface shock shape, the center plane shock shape, and crosssectional shock shape. The shock total pressure was estimated with the normal component of the Mach number using normal shock theory. The shock induced total pressure losses decrease with decreasing jet incidence angle and injection pressure, where the largest losses are incurred by the 90 degrees, circular injector.展开更多
This paper presents an experimental study into dynamics of chamber pressure and heat release rate during self-excited spinning and standing azimuthal mode in NTO/MMH (nitrogen tetroxide/monomethylhydrazine) impinging ...This paper presents an experimental study into dynamics of chamber pressure and heat release rate during self-excited spinning and standing azimuthal mode in NTO/MMH (nitrogen tetroxide/monomethylhydrazine) impinging combustion chambers.Nine cases including two combustion chamber configurations were conducted.The operating conditions of all unstable cases were located in the instability region according to Hewitt empirical correlation.The results show that chamber pressure oscillations keep pace with the corresponding OH*chemiluminescence intensity over the whole combustion region in the spinning and standing modes.It is indicated that the Rayleigh index is positive over the whole combustion area in all the unstable cases.A significant supersonic flame front structure of the first-order spinning mode was found in a cylindrical chamber,which means that a detonation wave could exist in the cylindrical chamber without a center body.The pressure and heat release rate oscillations at the pressure node are nonnegligible although their amplitudes are lower than those at the pressure antinode in the first-order standing mode with an annular chamber.Besides,the dominant frequency of pressure and heat release rate oscillations at the pressure node is twice as high as that at the pressure antinode.展开更多
The effects of tabular stratified CO_(2)/O_(2)jet in cross flow on thermoacoustic instability and NO_(x)emission were experimentally studied.To explore the dependence of injection positions on flame stability,two fact...The effects of tabular stratified CO_(2)/O_(2)jet in cross flow on thermoacoustic instability and NO_(x)emission were experimentally studied.To explore the dependence of injection positions on flame stability,two factors were taken:the injection height and the injection direction of CO_(2)/O_(2)gas.Results show that the injection positions seriously affect the control effectiveness.The optimum acoustic amplitude-damped ratio of thermoacoustic instability can reach 76.61%with the first layer of horizontal direction.The sound pressure amplitude declined from 56 Pa to 13.1 Pa.The concentration-damped ratio of NO_(x)emission can achieve 66.67%with the first layer of vertical direction.The concentration of NO_(x)emission declined from 50.4 mg/m^(3)to 16.8mg/m^(3)as the jet in cross flow rate increased.Higher oxygen ratio of stratified CO_(2)/O_(2)jets can produce lower NO_(x)emission but higher combustion instability.The descending gradient of NO_(x)emissions is different among different injection positions.Frequency shifting of the sound pressure and flame CH*chemiluminescence emerged.The oscillation frequency declined as the flow rate of CO_(2)/O_(2)jets increased.The unsteady long and compact flame was dispersed after CO_(2)/O_(2)injection.The macrostructure of flame was characterized as flatter and short under jet in cross flow.The variation curves of the flame length and top view area are similar to the shape of half saddle lines.This research proved the optimal control of thermoacoustic instability and NO_(x)emissions with a passive method,which could be conducive to the realization of clean and secure combustion in industrial lean premixed combustors.展开更多
Rapid mixing and chlorine saving are two important problems that most drinking water industries are focus on, and this paper adopts chemical induction unit to compare with water jet injector to study what merits chemi...Rapid mixing and chlorine saving are two important problems that most drinking water industries are focus on, and this paper adopts chemical induction unit to compare with water jet injector to study what merits chemical induction unit has. The experiment chose coefficient of variability of chlorine concentration to evaluate the mix effect and used chlorine consumption to compare the two equipments. Distribution reservoir experiments show that chemical induction unit can completely mix chlorine less than 6.2 seconds and water jet injector can not completely mix in 3 minutes. Mixing pool experiments show that chemical induction unit can save chlorine compared with water jet injector, and can save more if more chlorine is consumed.展开更多
An experimental study on the Klystron effect of periodic injection modulated by pressure drop fluctuations on subsequent atomization is conducted. Time-resolved atomization backlit images and atomization Mie scatter i...An experimental study on the Klystron effect of periodic injection modulated by pressure drop fluctuations on subsequent atomization is conducted. Time-resolved atomization backlit images and atomization Mie scatter images are captured by using the high speed camera. It is found that periodicity of forced atomization relies on pressure drop fluctuation amplitude and phase differences between atomization and pressure drop fluctuations relate to fluctuation frequencies. This feature of periodic atomization induced by Klystron effect corresponds to periodicities and high amplitudes of pressure fluctuations in unstable combustion chambers and chaos and low amplitudes of pressure fluctuations in stable combustions chambers. Drastically periodic varying of gross surface area of droplets with time was shown in Mie scatter images. The importance of periodic impinging jet atomization modulated by pressure drop fluctuations for acoustic liquid propellant combustion instabilities is illustrated.展开更多
文摘Interaction flow field of the sonic air jet through diamond shaped orifices at different incidence angles （10 degrees, 27.5 degrees, 45 degrees and 90 degrees） and total pressures （0.10 MPa and 0. 46 MPa） with a Mach 5.0 freestream was studied experimentally. A 90 degrees circular injector was examined for comparison. Crosssection Mach number contours were acquired by a Pitot-cone five-hole pressure probe. The results indicate that the low Mach semicircular region close to the wall is the wake region. The boundary layer thinning is in the areas adjacent to the wake. For the detached case, the interaction shock extends further into the freestream, and the shock shape has more curvature, also the low-Mach upwash region is larger. The vortices of the plume and the height of the jet interaction shock increase with increasing incidence angle and jet pressure. 90 degrees diamond and circular injector have stronger plume vorticity, and for the circular injector low-Mach region is smaller than that for the diamond injector. Tapered ramp increases the plume vorticity, and the double ramp reduces the level of vorticity. The three-dimensional interaction shock shape was modeled from the surface shock shape, the center plane shock shape, and crosssectional shock shape. The shock total pressure was estimated with the normal component of the Mach number using normal shock theory. The shock induced total pressure losses decrease with decreasing jet incidence angle and injection pressure, where the largest losses are incurred by the 90 degrees, circular injector.
基金co-supported by the National Natural Science Foundation of China (Nos. 11502186 and 51506157)the National Key Basic Research Program of China
文摘This paper presents an experimental study into dynamics of chamber pressure and heat release rate during self-excited spinning and standing azimuthal mode in NTO/MMH (nitrogen tetroxide/monomethylhydrazine) impinging combustion chambers.Nine cases including two combustion chamber configurations were conducted.The operating conditions of all unstable cases were located in the instability region according to Hewitt empirical correlation.The results show that chamber pressure oscillations keep pace with the corresponding OH*chemiluminescence intensity over the whole combustion region in the spinning and standing modes.It is indicated that the Rayleigh index is positive over the whole combustion area in all the unstable cases.A significant supersonic flame front structure of the first-order spinning mode was found in a cylindrical chamber,which means that a detonation wave could exist in the cylindrical chamber without a center body.The pressure and heat release rate oscillations at the pressure node are nonnegligible although their amplitudes are lower than those at the pressure antinode in the first-order standing mode with an annular chamber.Besides,the dominant frequency of pressure and heat release rate oscillations at the pressure node is twice as high as that at the pressure antinode.
基金supported by The National Science Fund for Distinguished Young Scholars(51825605)。
文摘The effects of tabular stratified CO_(2)/O_(2)jet in cross flow on thermoacoustic instability and NO_(x)emission were experimentally studied.To explore the dependence of injection positions on flame stability,two factors were taken:the injection height and the injection direction of CO_(2)/O_(2)gas.Results show that the injection positions seriously affect the control effectiveness.The optimum acoustic amplitude-damped ratio of thermoacoustic instability can reach 76.61%with the first layer of horizontal direction.The sound pressure amplitude declined from 56 Pa to 13.1 Pa.The concentration-damped ratio of NO_(x)emission can achieve 66.67%with the first layer of vertical direction.The concentration of NO_(x)emission declined from 50.4 mg/m^(3)to 16.8mg/m^(3)as the jet in cross flow rate increased.Higher oxygen ratio of stratified CO_(2)/O_(2)jets can produce lower NO_(x)emission but higher combustion instability.The descending gradient of NO_(x)emissions is different among different injection positions.Frequency shifting of the sound pressure and flame CH*chemiluminescence emerged.The oscillation frequency declined as the flow rate of CO_(2)/O_(2)jets increased.The unsteady long and compact flame was dispersed after CO_(2)/O_(2)injection.The macrostructure of flame was characterized as flatter and short under jet in cross flow.The variation curves of the flame length and top view area are similar to the shape of half saddle lines.This research proved the optimal control of thermoacoustic instability and NO_(x)emissions with a passive method,which could be conducive to the realization of clean and secure combustion in industrial lean premixed combustors.
文摘Rapid mixing and chlorine saving are two important problems that most drinking water industries are focus on, and this paper adopts chemical induction unit to compare with water jet injector to study what merits chemical induction unit has. The experiment chose coefficient of variability of chlorine concentration to evaluate the mix effect and used chlorine consumption to compare the two equipments. Distribution reservoir experiments show that chemical induction unit can completely mix chlorine less than 6.2 seconds and water jet injector can not completely mix in 3 minutes. Mixing pool experiments show that chemical induction unit can save chlorine compared with water jet injector, and can save more if more chlorine is consumed.
基金supported by the National Natural Science Foundation of China (Nos. 11502186 and 51606138)the National Key Basic Research Program of ChinaNational Key Scientific Instrument and the Equipment Development Projects of China (No. 2012YQ04016408)
文摘An experimental study on the Klystron effect of periodic injection modulated by pressure drop fluctuations on subsequent atomization is conducted. Time-resolved atomization backlit images and atomization Mie scatter images are captured by using the high speed camera. It is found that periodicity of forced atomization relies on pressure drop fluctuation amplitude and phase differences between atomization and pressure drop fluctuations relate to fluctuation frequencies. This feature of periodic atomization induced by Klystron effect corresponds to periodicities and high amplitudes of pressure fluctuations in unstable combustion chambers and chaos and low amplitudes of pressure fluctuations in stable combustions chambers. Drastically periodic varying of gross surface area of droplets with time was shown in Mie scatter images. The importance of periodic impinging jet atomization modulated by pressure drop fluctuations for acoustic liquid propellant combustion instabilities is illustrated.
