In this paper,a model predictive control(MPC)solution,assisted by extended state observer(ESO),is proposed for the common rail pressure control in gasoline engines.The rail pressure dynamic,nonlinear with large uncert...In this paper,a model predictive control(MPC)solution,assisted by extended state observer(ESO),is proposed for the common rail pressure control in gasoline engines.The rail pressure dynamic,nonlinear with large uncertainty,is modeled as a simple first order system.The discrepancy of the model from the real plant is lumped as"total disturbance",to be estimated in real-time by ESO and the n mitigated in the nonlin ear MPC,assuming the total disturbance does not change in the prediction horiz on.The non linear MPC problem is solved using the Newton/generalized minimum residual(GMRES)algorithm.The proposed ESO-MPC solution,is compared with the conventional proportional-integral-differential(PID)controller,based on the high-fidelity model provided in the benchmark problem in IFAC-E-CoSM.Results show the following benefits from using ESO-MPC relative to PID(benchmark):1)the disturbance rejection capability to fuel inject pulse step is improved by 12%in terms of recovery time;2)the transient response of rail pressure is improved by 5%in terms of the integrated absolute tracking error;and 3)the robustness is improved without n eed for gain scheduling,which is required in PID.Additionally,in creasing the ban dwidth of ESO allows reducing the complexity of the model implemented in MPC,while maintaining the disturbance rejection performance at the cost of high noise-sensitivity.Therefore,the ESO-MPC combination offers a simpler and more practical solution for common rail pressure control,relative to the standard MPC,which is consistent with the findings in simulation.展开更多
In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion insta...In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion instabilities when operating under lean burning conditions.In this paper,the role of turbulence enhancement in improving the lean combustion of natural gas was investigated in an optical SI engine with high compression ratios.Variable swirl control valves(SCV)were designed and intake tumble and swirl were combined to regulate turbulent motion and turbulent intensity.Particle image velocimetry was employed to measure in-cylinder turbulence,and transient pressure acquisition and high-speed photography were synchronously performed to quantify combustion evolutions.The results show that incylinder turbulent intensity is enhanced significantly through reducing SCV closing angles.Such that flame propagation speed and thermal efficiency are significantly improved with an increment of turbulent intensity,which indicated that mean effective pressures are not sensitive to spark timing.The analysis of flame images shows that the combined turbulence increases in the radial orientation from the spark plug to the cylinder wall,leading to an earlier flame kernel formation and a faster burning rate.Therefore,the combined turbulence has the potential in reducing the cyclic variations of lean combustion in natural gas engines.展开更多
A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different inject...A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.展开更多
The aim of this study was to investigate the oxidation reactivity and behavior of exhaust particulate matter(PM)from diesel engines.PM samples from two diesel engines(1K,CY4102)with different emission levels were coll...The aim of this study was to investigate the oxidation reactivity and behavior of exhaust particulate matter(PM)from diesel engines.PM samples from two diesel engines(1K,CY4102)with different emission levels were collected by a thermophoretic system and a quartz filter.The oxidation reactivity,oxidation behaviors,and physicochemical properties of the PM samples were analyzed using thermogravimetric analysis(TGA),high-resolution transmission electron microscopy(HRTEM),Fourier-transform infrared spectrometry(FTIR),and Raman spectroscopy.The results showed that there was a great difference in the oxidation reactivity of soot particles emitted by the two different diesel engines.A qualitative analysis of the factors influencing oxidation reactivity showed that the nanostructure,degree of graphitization,and relative concentration of aliphatic C—H functional groups were the most important factors,whereas no significant correlation was found between the primary particle size and activation energy of the diesel soot.Based on the oxidation behavior analysis,the diesel soot particles exhibited both internal and surface oxidation modes during the oxidation process.Surface oxidation was dominant during the initial stage,and as oxidation progressed,the mode gradually changed to internal oxidation.Internal oxidation mode of soot particles from the 1K engine was significantly higher than that of CY4102.展开更多
The flame structure of gasoline engine is complicated and has the characteristic of fractal geometry. A fractal combustion model was used to simulate the engine working cycle. Based on this model, the fractal dimensio...The flame structure of gasoline engine is complicated and has the characteristic of fractal geometry. A fractal combustion model was used to simulate the engine working cycle. Based on this model, the fractal dimension and laminar flame surface area of turbulent premixed flames were studied under different working conditions. The experimental system mainly includes an optical engine and a set of photography equipment used to shoot the images of turbulent flame of spark-ignition engine. The difference box-counting method was used to process 2D combustion images. In contrast to the experimental results, the computational results show that the fractal combustion model is an effective method of simulating the engine combustion process. The study provides a better understanding for flame structure and its propagation.展开更多
Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)softwar...Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.展开更多
Understanding the influence of HCl on the NH_(3)-selective catalytic reduction reaction mechanism is crucial for designing highly efficient denitrification catalysts.The formation of chlorate species on the surface of...Understanding the influence of HCl on the NH_(3)-selective catalytic reduction reaction mechanism is crucial for designing highly efficient denitrification catalysts.The formation of chlorate species on the surface of the synthesized SbCeO_(x)catalyst,induced by HCl,significantly enhances low-temperature activity,as evidenced by a 30%increase in NO conversion at 155℃.Furthermore,it improves N_(2)selectivity at high temperatures,with a notable 17%increase observed at 405℃.Both experimental results and density functional theory calculations confirm that chlorate species form at Ce sites.This formation facilitates the creation of oxygen vacancies,boosting the oxygen exchange capacity.It also increases NH_(3)adsorption at the Ce sites,promotes the formation of Sb-OH,and reduces competitive OH adsorption on these sites.Notably,compared with the reaction mechanism without HCl,the presence of chlorate species enhances NH_(3)adsorption and activation,which is vital for subsequent catalytic reactions.展开更多
The emission regulations for heavy-duty diesel engines regarding nitrogen oxide(NO_(x))are becoming increasingly stringent,particularly in relation to cold start cycles.While the twostage selective catalytic reduction...The emission regulations for heavy-duty diesel engines regarding nitrogen oxide(NO_(x))are becoming increasingly stringent,particularly in relation to cold start cycles.While the twostage selective catalytic reduction(SCR)has the potential to achieve ultra-low NO_(x) emissions,several challenges remain,including the accurate prediction of ammonia(NH_(3))storage mass and the co-control of the two-stage SCR.The first step in this study involved the establishment of a rapid control prototype platform to facilitate the development and validation of a two-stage SCR control strategy.Secondly,an initial method for predicting the NH_(3) storage based on the mass conservation law was proposed,which was subsequently improved by filling and emptying experiments.The third step involved the development of a two-stage SCR co-control strategy,including obtaining the steady-state NH_(3) storage target value,dynamic correction for NH_(3) storage target value,regulation of NH_(3) storage,and control of the close-coupled SCR urea injector state.Finally,the two-stage SCR urea injection control strategy was certified under the world harmonized transient cycle(WHTC).The results demonstrate that the composite value of engine outlet NO_(x) emissions under cold and hot start WHTC cycles is 13 g/(kW·h).Meanwhile,the composite value of tailpipe NO_(x) emissions under cold and hot start WHTC cycles is 0.065 g/(kW·h),representing only 14%of the EU VI limit value of 0.46 g/(kW·h).Thus,the findings demonstrate that integrating an accurate NH_(3) storage prediction method with the two-stage SCR co-control function is crucial for heavy-duty diesel engines to achieve ultra-low NO_(x) emissions.展开更多
Vibration signals from diesel engine contain many different components mainly caused by combustion and mechanism operations,several blind source separation techniques are available for decomposing the signal into its ...Vibration signals from diesel engine contain many different components mainly caused by combustion and mechanism operations,several blind source separation techniques are available for decomposing the signal into its components in the case of multichannel measurements,such as independent component analysis（ICA）.However,the source separation of vibration signal from single-channel is impossible.In order to study the source separation from single-channel signal for the purpose of source extraction,the combination method of empirical mode decomposition（EMD） and ICA is proposed in diesel engine signal processing.The performance of the described methods of EMD-wavelet and EMD-ICA in vibration signal application is compared,and the results show that EMD-ICA method outperforms the other,and overcomes the drawback of ICA in the case of single-channel measurement.The independent source signal components can be separated and identified effectively from one-channel measurement by EMD-ICA.Hence,EMD-ICA improves the extraction and identification abilities of source signals from diesel engine vibration measurements.展开更多
The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction（SCR） of NO_x by NH_3. V/Ce/WTi-DP（deposition precipitation） catalyst showed excellent NH...The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction（SCR） of NO_x by NH_3. V/Ce/WTi-DP（deposition precipitation） catalyst showed excellent NH_3-SCR performance, especially the better medium-temperature activity and the less N_2O formation than V/Ce/WTi-IMP（impregnation）. These catalysts were characterized by X-ray diffraction（XRD）, Brumauer-Emmett-Teller（BET）, X-ray photoelectron spectroscopy（XPS）, temperature-programmed reduction（H_2-TPR）, and in situ DRIFTS techniques. The XPS and H_2-TPR results revealed that V/Ce/WTi-DP exhibited more surface Ce species, higher level of Oα and higher reducibility of Ce species. Reflected by in situ DRIFTS results, the deposition precipitation method（DP） contributed to a greater amount of weakly adsorbed NO_2, monodentate nitrate and NH_3 species with better reactive activity. Meanwhile, the cis-N_2O_2^（2-） species, an intermediate for N_2O formation, was very limited. As a result, these advantages brought about the superior SCR activity and N_2 selectivity for V/Ce/WTi-DP.展开更多
La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）...La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）, X-ray photoelectron spectroscopy （XPS）, NO＋O2 -TPD （temperature-programmed desorption）, activated oxygen evaluation and H2 -TPR （temperature-programmed reduction） technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4＋ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.展开更多
To understand the engine main bearings＇ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely consid...To understand the engine main bearings＇ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic（TEHD） reaction on engine main bearings is investigated. The calculated method of main bearing＇s thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic（EHD） and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.展开更多
Nanoparticle of cerium borate with a size of about 50 nm was synthesized via sol-gel precipitation method under micro-emulsion by oleic acid,using Na2B4O7 and Ce（NO3）3 aqueous solution as raw materials,and the morph...Nanoparticle of cerium borate with a size of about 50 nm was synthesized via sol-gel precipitation method under micro-emulsion by oleic acid,using Na2B4O7 and Ce（NO3）3 aqueous solution as raw materials,and the morphology and microstructure of as-prepared particles were characterized by means of scanning electron microscopy（SEM） equipped with an energy-dispersive X-ray spectrometer（EDS）,X-ray diffraction（XRD）,infrared spectroscopy（IR）,and thermogravimetric analysis（TGA）.Two methods to disperse the particles into base oil were employed,and the results derived from the four-ball tribotester indicated that the friction coefficient of the base oil by the addition of the nanoscale cerium borate particles diminished greatly,and the anti-wear properties also depended on the dispersion methods.展开更多
Fatigue fracture is one of the main failure modes of Ti-6A1-4V alloy,fracture toughness and crack closure have strong effects on the fatigue crack growth（FCG）rate of Ti-6A1-4V alloy.The FCG rate of Ti-6A1-4V is inve...Fatigue fracture is one of the main failure modes of Ti-6A1-4V alloy,fracture toughness and crack closure have strong effects on the fatigue crack growth（FCG）rate of Ti-6A1-4V alloy.The FCG rate of Ti-6A1-4V is investigated by using experimental and analytical methods.The effects of stress ratio,crack closure and fracture toughness on the FCG rate are studied and discussed.A modified prediction model of the FCG rate is proposed,and the relationship between the fracture toughness and the stress intensity factor（SIF）range is redefined by introducing a correcting coefficient.Notched plate fatigue tests（including the fracture toughness test and the FCG rate test）are conducted to investigate the influence of affecting factors on the FCG rate.Comparisons between the predicted results of the proposed model,the Paris model,the Walker model,the Sadananda model,and the experimental data show that the proposed model gives the best agreement with the test data particularly in the near-threshold region and the Paris region,and the corresponding calculated fatigue life is also accurate in the same regions.By considering the effects of fracture toughness and crack closure,the novel FCG rate prediction model not only improves the estimating accuracy,but also extends the adaptability of the FCG rate prediction model in engineering.展开更多
Copper-exchanged chabazite（Cu/CHA） catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na＋ ions on Cu/SAPO-34 for ammonia selective catalytic reduction（NH_3-SC...Copper-exchanged chabazite（Cu/CHA） catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na＋ ions on Cu/SAPO-34 for ammonia selective catalytic reduction（NH_3-SCR） are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na＋ ion-exchanges with H＋and Cu2＋of Cu/SAPO-34. The exchange of H＋is easier than that of isolated Cu2＋. The exchanged Cu2＋ions aggregate and form ＂CuAl_2O4-like＂ species.The NH_3-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu2＋and acid sites is responsible for the activity loss.展开更多
Volatile organic compounds(VOCs)with high toxicity and carcinogenicity are emitted from kinds of industries,which endanger human health and the environment.Adsorption is a promising method for the treatment of VOCs du...Volatile organic compounds(VOCs)with high toxicity and carcinogenicity are emitted from kinds of industries,which endanger human health and the environment.Adsorption is a promising method for the treatment of VOCs due to its low cost and high efficiency.In recent years,activated carbons,zeolites,and mesoporous materials are widely used to remove VOCs because of their high specific surface area and abundant porosity.However,the hydrophilic nature and low desorption rate of those materials limit their commercial application.Furthermore,the adsorption capacities of VOCs still need to be improved.Porous organic polymers(POPs)with extremely high porosity,structural diversity,and hydrophobic have been considered as one of the most promising candidates for VOCs adsorption.This review generalized the superiority of POPs for VOCs adsorption compared to other porous materials and summarized the studies of VOCs adsorption on different types of POPs.Moreover,the mechanism of competitive adsorption between water and VOCs on the POPs was discussed.Finally,a concise outlook for utilizing POPs for VOCs adsorption was discussed,noting areas in which further work is needed to develop the next-generation POPs for practical applications.展开更多
To comprehensively consider the effects of strength degeneration and failure correlation, an improved stress–strength interference （SSI） model is proposed to analyze the reliability of aeroengine blades with the fa...To comprehensively consider the effects of strength degeneration and failure correlation, an improved stress–strength interference （SSI） model is proposed to analyze the reliability of aeroengine blades with the fatigue failure mode. Two types of TC4 alloy experiments are conducted for the study on the damage accumulation law. All the parameters in the nonlinear damage model are obtained by the tension–compression fatigue tests, and the accuracy of the nonlinear damage model is verified by the damage tests. The strength degeneration model is put forward on the basis of the Chaboche nonlinear damage theory and the Griffith fracture criterion, and determined by measuring the fatigue toughness during the tests. From the comparison of two kinds of degeneration models based on the Miner’s linear law and the nonlinear damage model respectively, the nonlinear model has a significant advantage on prediction accuracy especially in the later period of life. A time-dependent SSI reliability model is established. By computing the stress distribution using the finite element （FE） technique, the reliability of a single blade during the whole service life is obtained. Considering the failure correlation of components, a modified reliability model of aero-engine blades with common cause failure （CCF） is presented. It shows a closer and more reasonable process with the actual working condition. The improved reliability model is illustrated to be applied to aero-engine blades well, and the approach purposed in this paper is suitable for any actual machinery component of aero-engine rotor systems.展开更多
Gasoline compression ignition (GCI) is one of the most promising combustion concepts to maintain low pollutant emissions and high efficiency. However, low load combustion stability and firing in cold-start operations ...Gasoline compression ignition (GCI) is one of the most promising combustion concepts to maintain low pollutant emissions and high efficiency. However, low load combustion stability and firing in cold-start operations are two major challenges for GCI combustion. Strategies including negative valve overlap (NVO), advanced injection strategies, fuel reforming, and intake preheating have been proposed in order to solve these difficulties;however, the cold start is still an obstacle. The objective of this work is to study effective methods to achieve GCI engine cold start-up. This work combines NVO, in-cylinder fuel reforming, and intake preheating to achieve quick firing under cold-start conditions and the subsequent warmup conditions. The results show that start of injection (SOI) during the intake stroke yields the best fuel economy, and injection during the compression stroke has the potential to extend the low load limit. Furthermore, SOI during the NVO period grants the ability to operate under engine conditions with cold intake air and coolant. With highly reactive products made by in-cylinder fuel reforming and fast heat accumulation in the combustion chamber, the NVO injection strategy is highly appropriate for GCI firing. An additional assisted technical method, such as intake preheating, is required to ignite the first firing cycle for a cold-start process. With the combination of NVO, in-cylinder fuel reforming, and intake preheating, the GCI engine successfully started within five combustion cycles in the experiment. After the firing process, the engine could stably operate without further intake preheating;thus, this method is appropriate for engine cold-start and warm-up.展开更多
Analytical prediction of heteroclinic bifurcation of the strongly nonlinear oscillator is presented by using the extended normal form method. We consider the approximate periodic solution of the system subject to the ...Analytical prediction of heteroclinic bifurcation of the strongly nonlinear oscillator is presented by using the extended normal form method. We consider the approximate periodic solution of the system subject to the quintic nonlinearity by introducing the undetermined fundamental frequency. For the occurrence of heteroclinicity, the bifurcation criterion is accomplished. It depends on the contact of the limit cycle with the saddle equilibrium. As is illustrated, the explicit application shows that the new results coincide very well with the results of numerical simulation when disturbing parameter is of arbitrary magnitude.展开更多
Due to strong synergistic effect of the elements,a series of XEuMnO_(x) ternary oxides(X=Ce,Ni,Co,Sb,Sn,Mo) were synthesized by one-pot co-precipitation method,and composite components were identified and optimized to...Due to strong synergistic effect of the elements,a series of XEuMnO_(x) ternary oxides(X=Ce,Ni,Co,Sb,Sn,Mo) were synthesized by one-pot co-precipitation method,and composite components were identified and optimized to maintain high activity and superior SO_(2)and H_(2)O endurance in selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).NO_(x)conversion of CeEuMnO_(x) ternary oxide catalysts attains more than 90% at 100-250℃,and finally achieves 74%under existence of 50×10^(-6)SO_(2) and 10 vol% H_(2)O at 230℃.The facile electron transfer through redox cycle of Mn^(3+)+Ce^(4+)■Mn4++Ce^(3+) and enhanced oxygen mobility can promote formation of more Mn species in high oxidation state and chemisorbed oxygen,accelerating oxidation of NO and the adsorbed NO_(2) formed can facilitate"fast SCR"reaction to improve low-temperature activity.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)study reveals that addition of Ce to EuMnO_(x)catalyst boosts adsorption of NH_(3)and NO_(x)species.NH_(3)species are activated as crucial intermediate(NH_(2))to promote NH_(3)-SCR reaction.This research provides a novel material for practical deNO_(x)application of stationary source combustion flue gas in the future.展开更多
文摘In this paper,a model predictive control(MPC)solution,assisted by extended state observer(ESO),is proposed for the common rail pressure control in gasoline engines.The rail pressure dynamic,nonlinear with large uncertainty,is modeled as a simple first order system.The discrepancy of the model from the real plant is lumped as"total disturbance",to be estimated in real-time by ESO and the n mitigated in the nonlin ear MPC,assuming the total disturbance does not change in the prediction horiz on.The non linear MPC problem is solved using the Newton/generalized minimum residual(GMRES)algorithm.The proposed ESO-MPC solution,is compared with the conventional proportional-integral-differential(PID)controller,based on the high-fidelity model provided in the benchmark problem in IFAC-E-CoSM.Results show the following benefits from using ESO-MPC relative to PID(benchmark):1)the disturbance rejection capability to fuel inject pulse step is improved by 12%in terms of recovery time;2)the transient response of rail pressure is improved by 5%in terms of the integrated absolute tracking error;and 3)the robustness is improved without n eed for gain scheduling,which is required in PID.Additionally,in creasing the ban dwidth of ESO allows reducing the complexity of the model implemented in MPC,while maintaining the disturbance rejection performance at the cost of high noise-sensitivity.Therefore,the ESO-MPC combination offers a simpler and more practical solution for common rail pressure control,relative to the standard MPC,which is consistent with the findings in simulation.
基金Projects(52076149,51825603)supported by the National Natural Science Foundation of China。
文摘In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion instabilities when operating under lean burning conditions.In this paper,the role of turbulence enhancement in improving the lean combustion of natural gas was investigated in an optical SI engine with high compression ratios.Variable swirl control valves(SCV)were designed and intake tumble and swirl were combined to regulate turbulent motion and turbulent intensity.Particle image velocimetry was employed to measure in-cylinder turbulence,and transient pressure acquisition and high-speed photography were synchronously performed to quantify combustion evolutions.The results show that incylinder turbulent intensity is enhanced significantly through reducing SCV closing angles.Such that flame propagation speed and thermal efficiency are significantly improved with an increment of turbulent intensity,which indicated that mean effective pressures are not sensitive to spark timing.The analysis of flame images shows that the combined turbulence increases in the radial orientation from the spark plug to the cylinder wall,leading to an earlier flame kernel formation and a faster burning rate.Therefore,the combined turbulence has the potential in reducing the cyclic variations of lean combustion in natural gas engines.
基金Supported by National High Technology Research and Development Program ("863" Program) of China (No.2008AA11A114)
文摘A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability.
基金the SINOPEC(124015)and the State Key Laboratory of Engines at Tianjin University(No.K2022-06).
文摘The aim of this study was to investigate the oxidation reactivity and behavior of exhaust particulate matter(PM)from diesel engines.PM samples from two diesel engines(1K,CY4102)with different emission levels were collected by a thermophoretic system and a quartz filter.The oxidation reactivity,oxidation behaviors,and physicochemical properties of the PM samples were analyzed using thermogravimetric analysis(TGA),high-resolution transmission electron microscopy(HRTEM),Fourier-transform infrared spectrometry(FTIR),and Raman spectroscopy.The results showed that there was a great difference in the oxidation reactivity of soot particles emitted by the two different diesel engines.A qualitative analysis of the factors influencing oxidation reactivity showed that the nanostructure,degree of graphitization,and relative concentration of aliphatic C—H functional groups were the most important factors,whereas no significant correlation was found between the primary particle size and activation energy of the diesel soot.Based on the oxidation behavior analysis,the diesel soot particles exhibited both internal and surface oxidation modes during the oxidation process.Surface oxidation was dominant during the initial stage,and as oxidation progressed,the mode gradually changed to internal oxidation.Internal oxidation mode of soot particles from the 1K engine was significantly higher than that of CY4102.
基金Supported by National Natural Science Foundation of China (No. 50876072) Tianjin Municipal Science and Technology Commission (No. 07JCYBJC03900 )
文摘The flame structure of gasoline engine is complicated and has the characteristic of fractal geometry. A fractal combustion model was used to simulate the engine working cycle. Based on this model, the fractal dimension and laminar flame surface area of turbulent premixed flames were studied under different working conditions. The experimental system mainly includes an optical engine and a set of photography equipment used to shoot the images of turbulent flame of spark-ignition engine. The difference box-counting method was used to process 2D combustion images. In contrast to the experimental results, the computational results show that the fractal combustion model is an effective method of simulating the engine combustion process. The study provides a better understanding for flame structure and its propagation.
文摘Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.
文摘Understanding the influence of HCl on the NH_(3)-selective catalytic reduction reaction mechanism is crucial for designing highly efficient denitrification catalysts.The formation of chlorate species on the surface of the synthesized SbCeO_(x)catalyst,induced by HCl,significantly enhances low-temperature activity,as evidenced by a 30%increase in NO conversion at 155℃.Furthermore,it improves N_(2)selectivity at high temperatures,with a notable 17%increase observed at 405℃.Both experimental results and density functional theory calculations confirm that chlorate species form at Ce sites.This formation facilitates the creation of oxygen vacancies,boosting the oxygen exchange capacity.It also increases NH_(3)adsorption at the Ce sites,promotes the formation of Sb-OH,and reduces competitive OH adsorption on these sites.Notably,compared with the reaction mechanism without HCl,the presence of chlorate species enhances NH_(3)adsorption and activation,which is vital for subsequent catalytic reactions.
基金supported by the National Natural Science Foundation of China(No.51921004).
文摘The emission regulations for heavy-duty diesel engines regarding nitrogen oxide(NO_(x))are becoming increasingly stringent,particularly in relation to cold start cycles.While the twostage selective catalytic reduction(SCR)has the potential to achieve ultra-low NO_(x) emissions,several challenges remain,including the accurate prediction of ammonia(NH_(3))storage mass and the co-control of the two-stage SCR.The first step in this study involved the establishment of a rapid control prototype platform to facilitate the development and validation of a two-stage SCR control strategy.Secondly,an initial method for predicting the NH_(3) storage based on the mass conservation law was proposed,which was subsequently improved by filling and emptying experiments.The third step involved the development of a two-stage SCR co-control strategy,including obtaining the steady-state NH_(3) storage target value,dynamic correction for NH_(3) storage target value,regulation of NH_(3) storage,and control of the close-coupled SCR urea injector state.Finally,the two-stage SCR urea injection control strategy was certified under the world harmonized transient cycle(WHTC).The results demonstrate that the composite value of engine outlet NO_(x) emissions under cold and hot start WHTC cycles is 13 g/(kW·h).Meanwhile,the composite value of tailpipe NO_(x) emissions under cold and hot start WHTC cycles is 0.065 g/(kW·h),representing only 14%of the EU VI limit value of 0.46 g/(kW·h).Thus,the findings demonstrate that integrating an accurate NH_(3) storage prediction method with the two-stage SCR co-control function is crucial for heavy-duty diesel engines to achieve ultra-low NO_(x) emissions.
基金supported by National Natural Science Foundation of China (Grant No. 50975192)Tianjin Municipal Natural Science Foundation of China (Grant No. 10YFJZJC14100)
文摘Vibration signals from diesel engine contain many different components mainly caused by combustion and mechanism operations,several blind source separation techniques are available for decomposing the signal into its components in the case of multichannel measurements,such as independent component analysis（ICA）.However,the source separation of vibration signal from single-channel is impossible.In order to study the source separation from single-channel signal for the purpose of source extraction,the combination method of empirical mode decomposition（EMD） and ICA is proposed in diesel engine signal processing.The performance of the described methods of EMD-wavelet and EMD-ICA in vibration signal application is compared,and the results show that EMD-ICA method outperforms the other,and overcomes the drawback of ICA in the case of single-channel measurement.The independent source signal components can be separated and identified effectively from one-channel measurement by EMD-ICA.Hence,EMD-ICA improves the extraction and identification abilities of source signals from diesel engine vibration measurements.
基金supported by the Grant from the China Huadian Science and Technology Institute(CHDI.KJ-20)the National High-Tech Research and Development Program of China(863,2011AA03A405)
文摘The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction（SCR） of NO_x by NH_3. V/Ce/WTi-DP（deposition precipitation） catalyst showed excellent NH_3-SCR performance, especially the better medium-temperature activity and the less N_2O formation than V/Ce/WTi-IMP（impregnation）. These catalysts were characterized by X-ray diffraction（XRD）, Brumauer-Emmett-Teller（BET）, X-ray photoelectron spectroscopy（XPS）, temperature-programmed reduction（H_2-TPR）, and in situ DRIFTS techniques. The XPS and H_2-TPR results revealed that V/Ce/WTi-DP exhibited more surface Ce species, higher level of Oα and higher reducibility of Ce species. Reflected by in situ DRIFTS results, the deposition precipitation method（DP） contributed to a greater amount of weakly adsorbed NO_2, monodentate nitrate and NH_3 species with better reactive activity. Meanwhile, the cis-N_2O_2^（2-） species, an intermediate for N_2O formation, was very limited. As a result, these advantages brought about the superior SCR activity and N_2 selectivity for V/Ce/WTi-DP.
基金Project supported by National High Technology Research and Development Program of China(863Program,2011AA03A405)
文摘La1-x Cax MnO3 （x=0-0.3） perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction （XRD）, Brumauer-Emmett-Teller method （BET）, X-ray photoelectron spectroscopy （XPS）, NO＋O2 -TPD （temperature-programmed desorption）, activated oxygen evaluation and H2 -TPR （temperature-programmed reduction） technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4＋ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.
基金Supported by National Science and Technology Support Program of China:Vibration and Noise Reduction Technology Research and Application of Bulldozers and Other Earth Moving Machinery(Grant No.2015BAF07B04)
文摘To understand the engine main bearings＇ working condition is important in order to improve the performance of engine. However, thermal effects and thermal effect deformations of engine main bearings are rarely considered simultaneously in most studies. A typical finite element model is selected and the effect of thermoelastohydrodynamic（TEHD） reaction on engine main bearings is investigated. The calculated method of main bearing＇s thermal hydrodynamic reaction and journal misalignment effect is finite difference method, and its deformation reaction is calculated by using finite element method. The oil film pressure is solved numerically with Reynolds boundary conditions when various bearing characteristics are calculated. The whole model considers a temperature-pressure-viscosity relationship for the lubricant, surface roughness effect, and also an angular misalignment between the journal and the bearing. Numerical simulations of operation of a typical I6 diesel engine main bearing is conducted and importance of several contributing factors in mixed lubrication is discussed. The performance characteristics of journal misaligned main bearings under elastohydrodynamic（EHD） and TEHD loads of an I6 diesel engine are received, and then the journal center orbit movement, minimum oil film thickness and maximum oil film pressure of main bearings are estimated over a wide range of engine operation. The model is verified through the comparison with other present models. The TEHD performance of engine main bearings with various effects under the influences of journal misalignment is revealed, this is helpful to understand EHD and TEHD effect of misaligned engine main bearings.
文摘Nanoparticle of cerium borate with a size of about 50 nm was synthesized via sol-gel precipitation method under micro-emulsion by oleic acid,using Na2B4O7 and Ce（NO3）3 aqueous solution as raw materials,and the morphology and microstructure of as-prepared particles were characterized by means of scanning electron microscopy（SEM） equipped with an energy-dispersive X-ray spectrometer（EDS）,X-ray diffraction（XRD）,infrared spectroscopy（IR）,and thermogravimetric analysis（TGA）.Two methods to disperse the particles into base oil were employed,and the results derived from the four-ball tribotester indicated that the friction coefficient of the base oil by the addition of the nanoscale cerium borate particles diminished greatly,and the anti-wear properties also depended on the dispersion methods.
基金Supported by the Joint Funds of National Natural Science Foundation of ChinaCivil Aviation Administration Foundation of China(Grant No.U1233201)Science and Technology Support Plan of Tianjin,China(Grant No.13ZCZDGX00200)
文摘Fatigue fracture is one of the main failure modes of Ti-6A1-4V alloy,fracture toughness and crack closure have strong effects on the fatigue crack growth（FCG）rate of Ti-6A1-4V alloy.The FCG rate of Ti-6A1-4V is investigated by using experimental and analytical methods.The effects of stress ratio,crack closure and fracture toughness on the FCG rate are studied and discussed.A modified prediction model of the FCG rate is proposed,and the relationship between the fracture toughness and the stress intensity factor（SIF）range is redefined by introducing a correcting coefficient.Notched plate fatigue tests（including the fracture toughness test and the FCG rate test）are conducted to investigate the influence of affecting factors on the FCG rate.Comparisons between the predicted results of the proposed model,the Paris model,the Walker model,the Sadananda model,and the experimental data show that the proposed model gives the best agreement with the test data particularly in the near-threshold region and the Paris region,and the corresponding calculated fatigue life is also accurate in the same regions.By considering the effects of fracture toughness and crack closure,the novel FCG rate prediction model not only improves the estimating accuracy,but also extends the adaptability of the FCG rate prediction model in engineering.
基金financially supported by the National Key Research and Development program(No.2017YFC0211302)the National Natural Science Foundation of China(No.21676195)+1 种基金the Science Fund of State Key Laboratory of Engine Reliability(No.skler-201714)finical support from GM Global Research&Development(No.GAC1539)
文摘Copper-exchanged chabazite（Cu/CHA） catalysts have been found to be affected by alkali metal and alkaline earth ions. However, the effects of Na＋ ions on Cu/SAPO-34 for ammonia selective catalytic reduction（NH_3-SCR） are still unclear. In order to investigate the mechanism, five samples with various Na contents were synthesized and characterized. It was observed that the introduced Na＋ ion-exchanges with H＋and Cu2＋of Cu/SAPO-34. The exchange of H＋is easier than that of isolated Cu2＋. The exchanged Cu2＋ions aggregate and form ＂CuAl_2O4-like＂ species.The NH_3-SCR activity of Cu/SAPO-34 decreases with increasing Na content, and the loss of isolated Cu2＋and acid sites is responsible for the activity loss.
基金supported by the National Key R&D Pro-gram of China(Nos.2019YFC1904100,2019YFC1904102,2019YFC1903902,and 2016YFC0205300)the National En-gineering Laboratory for Mobile Source Emission Control Technology of China(No.NELMS2017A03)+3 种基金the Natural Na-tional Science Foundation of China(Nos.21503144,21690083)Tianjin Research Program of Ecological Environmental Treat-ment(Nos.18ZXSZSF00210,18ZXSZSF00060)the Tianjin Research Program of Application Foundation and Advanced Technique(No.16JCQNJC05400)Major Science and Tech-nology Project for Ecological Environment Management in Tianjin(No.18ZXSZSF00210)。
文摘Volatile organic compounds(VOCs)with high toxicity and carcinogenicity are emitted from kinds of industries,which endanger human health and the environment.Adsorption is a promising method for the treatment of VOCs due to its low cost and high efficiency.In recent years,activated carbons,zeolites,and mesoporous materials are widely used to remove VOCs because of their high specific surface area and abundant porosity.However,the hydrophilic nature and low desorption rate of those materials limit their commercial application.Furthermore,the adsorption capacities of VOCs still need to be improved.Porous organic polymers(POPs)with extremely high porosity,structural diversity,and hydrophobic have been considered as one of the most promising candidates for VOCs adsorption.This review generalized the superiority of POPs for VOCs adsorption compared to other porous materials and summarized the studies of VOCs adsorption on different types of POPs.Moreover,the mechanism of competitive adsorption between water and VOCs on the POPs was discussed.Finally,a concise outlook for utilizing POPs for VOCs adsorption was discussed,noting areas in which further work is needed to develop the next-generation POPs for practical applications.
基金National Science Foundation of China and Civil Aviation Administration Foundation of China(No.U1233201)National Natural Science Foundation of China(No.60879002)Tianjin Municipal Science and Technology Support Plan of China(No.10ZCKFGX03800)
文摘To comprehensively consider the effects of strength degeneration and failure correlation, an improved stress–strength interference （SSI） model is proposed to analyze the reliability of aeroengine blades with the fatigue failure mode. Two types of TC4 alloy experiments are conducted for the study on the damage accumulation law. All the parameters in the nonlinear damage model are obtained by the tension–compression fatigue tests, and the accuracy of the nonlinear damage model is verified by the damage tests. The strength degeneration model is put forward on the basis of the Chaboche nonlinear damage theory and the Griffith fracture criterion, and determined by measuring the fatigue toughness during the tests. From the comparison of two kinds of degeneration models based on the Miner’s linear law and the nonlinear damage model respectively, the nonlinear model has a significant advantage on prediction accuracy especially in the later period of life. A time-dependent SSI reliability model is established. By computing the stress distribution using the finite element （FE） technique, the reliability of a single blade during the whole service life is obtained. Considering the failure correlation of components, a modified reliability model of aero-engine blades with common cause failure （CCF） is presented. It shows a closer and more reasonable process with the actual working condition. The improved reliability model is illustrated to be applied to aero-engine blades well, and the approach purposed in this paper is suitable for any actual machinery component of aero-engine rotor systems.
基金the National Natural Science Foundation of China (91641203, 51476114, and 91741119)he National Key Research and Development Program of China (2017YFB0103400).
文摘Gasoline compression ignition (GCI) is one of the most promising combustion concepts to maintain low pollutant emissions and high efficiency. However, low load combustion stability and firing in cold-start operations are two major challenges for GCI combustion. Strategies including negative valve overlap (NVO), advanced injection strategies, fuel reforming, and intake preheating have been proposed in order to solve these difficulties;however, the cold start is still an obstacle. The objective of this work is to study effective methods to achieve GCI engine cold start-up. This work combines NVO, in-cylinder fuel reforming, and intake preheating to achieve quick firing under cold-start conditions and the subsequent warmup conditions. The results show that start of injection (SOI) during the intake stroke yields the best fuel economy, and injection during the compression stroke has the potential to extend the low load limit. Furthermore, SOI during the NVO period grants the ability to operate under engine conditions with cold intake air and coolant. With highly reactive products made by in-cylinder fuel reforming and fast heat accumulation in the combustion chamber, the NVO injection strategy is highly appropriate for GCI firing. An additional assisted technical method, such as intake preheating, is required to ignite the first firing cycle for a cold-start process. With the combination of NVO, in-cylinder fuel reforming, and intake preheating, the GCI engine successfully started within five combustion cycles in the experiment. After the firing process, the engine could stably operate without further intake preheating;thus, this method is appropriate for engine cold-start and warm-up.
基金Supported by the Specialized Research Fund for the Doctoral Programme of Higher Education of China and the National Natural Science Foundation of China under Grant Nos 20060056005 and 10372068.
文摘Analytical prediction of heteroclinic bifurcation of the strongly nonlinear oscillator is presented by using the extended normal form method. We consider the approximate periodic solution of the system subject to the quintic nonlinearity by introducing the undetermined fundamental frequency. For the occurrence of heteroclinicity, the bifurcation criterion is accomplished. It depends on the contact of the limit cycle with the saddle equilibrium. As is illustrated, the explicit application shows that the new results coincide very well with the results of numerical simulation when disturbing parameter is of arbitrary magnitude.
基金Project supported by the National Key R&D Program of China(2019YFC1904100,2019YFC1904102,2019YFC1903900,2019YFC1903902)the National Natural Science Foundation of China(U20A20132,52106180,22076136)+1 种基金the Hebei Province Major Scientific and Technological Achievement Transformation Fund Support Project(2021004012 A)the Central Government Guides the Local Science and Technology Development Fund Project(206Z3702G).
文摘Due to strong synergistic effect of the elements,a series of XEuMnO_(x) ternary oxides(X=Ce,Ni,Co,Sb,Sn,Mo) were synthesized by one-pot co-precipitation method,and composite components were identified and optimized to maintain high activity and superior SO_(2)and H_(2)O endurance in selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).NO_(x)conversion of CeEuMnO_(x) ternary oxide catalysts attains more than 90% at 100-250℃,and finally achieves 74%under existence of 50×10^(-6)SO_(2) and 10 vol% H_(2)O at 230℃.The facile electron transfer through redox cycle of Mn^(3+)+Ce^(4+)■Mn4++Ce^(3+) and enhanced oxygen mobility can promote formation of more Mn species in high oxidation state and chemisorbed oxygen,accelerating oxidation of NO and the adsorbed NO_(2) formed can facilitate"fast SCR"reaction to improve low-temperature activity.In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)study reveals that addition of Ce to EuMnO_(x)catalyst boosts adsorption of NH_(3)and NO_(x)species.NH_(3)species are activated as crucial intermediate(NH_(2))to promote NH_(3)-SCR reaction.This research provides a novel material for practical deNO_(x)application of stationary source combustion flue gas in the future.
