Abstract:To accurately measure the uncertainty of formaldehyde emission,factors affecting the uncertainty of formaldehyde emission measurement from heavy-duty methanol engines are analyzed from various aspects,such as man,machine,material,method,and environment.A mathematical model of formaldehyde emission is established,and the relative standard uncertainty of formaldehyde emission is calculated using the world harmonized transient cycle(WHTC)test bench.The results show that the uncertainty of formaldehyde emission is related to the repeatability of measurement,the relative standard uncertainty of formaldehyde mass concentration dilution factor,total volume after exhaust dilution,and the relative standard uncertainty of actual cycle work.Among them,the dilution factor had a greater impact.The average formalhyde emission of the cold WHTC test is 41.6 mg/(kW·h),and the standard uncertainty of formaldehyde emission measurement is 1.29 mg/(kW·h),with an expanded uncertainty of 2.58 mg/(kW·h).This research can provide a technical reference improving the accuracy and reproducibility of emission measurement of unconventional pollutants such as methanol and formaldehyde.

Abstract:To solve the problems of low efficiency,complex design,and unstable noise control in traditional noise reduction systems,a maze-type metamaterial structure is designed based on acoustic metamaterials.The COMSOL software is used to simulate and analyze the influence of the maze-type acoustic metamaterials on the propagation direction of sound waves and sound waves of different frequencies.The influence of the number of metamaterials on the noise sound pressure is verified through experiments.The simulation results show that the maze-type acoustic metamaterials change the propagation direction of sound waves,forming abnormal reflection to reduce the noise sound pressure;the thickness of the metamaterials is related to the frequency of sound waves,and the metamaterial structure can be designed for different frequency noises,which can achieve precise noise control.The experimental results show that when the sound wave frequency is 2 kHz,using maze-type acoustic metamaterials can reduce the root mean square of sound pressure level from 83.47 dB to 74.85 dB,and the noise is significantly reduced;as the number of metamaterials increases,root mean square of the sound pressure level continues to decrease,and the noise reduction effect is better,but too many metamaterials lead to an increase in the overall mass of the,it is recommended to choose a group(2 pieces)or two groups(4 pieces)when used in practice,and the noise reduction effect of metamaterials is better at time.

Abstract:In response to the new requirements of the Euro Ⅶ Emission Standard for brake wear particulate matter emissions,the limit values,testing methods,and testing equipment requirements of the Euro Ⅶ Emission Standard for brake wear particulate matter are deeply interpreted,a brake inertia test bench for the Euro Ⅶ emission standard is designed.The bench integrates particulate matter measurement,automatic control system,and mechanical electric inertia hybrid simulation technology,and proposes an overall laboratory layout that is suitable for different site conditions.The practical application results show that the inertia brake platform can accurately measure the number of solid particles,total particle number PM2.5、PM10.This design scheme not only meets the requirements of Euro Ⅶ Emission Standard,but also improves the accuracy of testing,reduces costs,and optimizes space.

Abstract:In order to improve the heat dissipation performance of square lithium-ion batteries,a new liquid cooling channel structure is designed.Based on Fluent simulation software,a coupled model of battery heat generation and fluid heat transfer is constructed.The influence of coolant flow rate,inlet temperature,and channel thickness on the cooling effect in the new liquid cooling channel structure is simulated and analyzed.The results show that the new flow channel reduce the maximum temperature of the battery pack by 8.26℃.As the flow rate increases,the maximum temperature of the battery decreases,the temperature difference of the battery does not change much,and the pressure difference of the liquid cooling channel increases significantly.The inlet temperature decreases,the maximum temperature of the battery pack decreases,and the temperature difference is within a reasonable range of variation.As the thickness of the flow channel increases,the maximum temperature of the battery pack rises,the pressure difference decreases,and the temperature difference remains within a reasonable range of variation.To achieve the synergistic goal of higher efficiency and lower energy consumption,a balance needs to be sought between heat dissipation performance and pump functional consumption.A flow rate of 0.4 m/s and a channel thickness of 3 mm are the preferred options.

Abstract:In order to accurately assess the reliability of the diesel injection pump,a method of dynamical calculation of the injection pump is proposed,and a dynamical model of a diesel injection pump through AVL Excite software is developed.Taking into account the impact of factors such as fluctuations in speed,fuel pressure,the stiffness of the components,a dynamic analysis is conducted on the thickness of the liner oil film,the strength of the camshaft,and the output torque,and the simulation results are compared with the test results.The results show that the camshaft bushing oil film thickness and camshaft strength calculated using this method correspond to the actual failure condition,the relative error of the simulated calculated output torque of the injection pump is approximately 5％ relative to the average peak of the test results,and the design of the injection pump model can be used to calculate the dynamics of the injection pump.

Abstract:To address the optimization of scavenging performance in a Curtis-type free-piston engine,the horizontal scavenging target point,the inclination angle of the lateral intake ports,and the inclination angle of the intake ports opposite the exhaust port are selected as design variables.An experimental design is constructed using the Box-Behnken response surface methodology,and response surface models are established with charging efficiency,scavenging efficiency,and trapping efficiency as the optimization objectives.On this basis,a desirability function is introduced to achieve multi-objective comprehensive optimization,yielding optimal port geometric parameters that simultaneously account for charging,scavenging,trapping,and short-circuiting losses.Simulation results indicate that when the horizontal scavenging target point is 11.86 mm,the inclination angle of the intake ports opposite the exhaust port is 46.01°,and the inclination angle of the lateral intake ports is 40.37°,the engine achieves the best overall scavenging performance.Under these conditions,the corresponding charging efficiency,scavenging efficiency,trapping efficiency,and delivery ratio are 1.061,0.977,0.331,and 3.205,respectively.The study demonstrates that the integrated response surface-desirability approach provides an effective design framework and parameter selection reference for the multi-objective optimization of scavenging port geometry in free-piston engines.

Abstract:In order to enhance the reliability of diesel particulate filters(DPF)and provide guidance for the active regeneration control,bench tests are conducted to investigate the pressure difference characteristics during the soot accumulation process of DPF and the internal temperature variation patterns during active regeneration.The results indicate significant differences in the pressure difference characteristics of DPF during different soot accumulation stages.The pressure difference of the DPF during the re-accumulation process after regeneration is on average about 2 hPa lower than before regeneration.During normal active regeneration,the axial temperature inside the DPF increases sequentially from the front to the rear,with the highest temperature point occurring at the rear end face of the DPF,reaching 715 ℃.The inconsistency of radial temperature indicate uneven combustion inside the DPF.During active regeneration process under drop to idle(DTI)operating conditions,the internal temperature of the DPF rises rapidly,reaching up to 1 034 ℃.When the soot loading exceeds 4 g/L,the internal temperature of the DPF increases linearly and rapidly with the soot loading.A higher DOC light-off rate causes the internal temperature of the DPF to rise rapidly in a short period of time.When the light-off rate is 6.5 ℃/s,the internal temperature of the DPF reaches 1 076 ℃.DTI operating conditions during active regeneration process,higher soot loading,and a higher DOC light-off rate are the main factors that increase the thermal risk during DPF regeneration,which must be reasonably controlled in practical applications.

Abstract:To analyze the dynamic characteristics of the carbody for a certain fixed-body mining truck,SolidWorks software is used to establish the geometric model of the carbody.Three typical working conditions,namely full-load bending,full-load extreme torsion and full-load braking,are selected for finite element modal simulation,and the simulation results are compared and analyzed with the road excitation frequency to verify the rationality of the dynamic performance of the carbody.The results show that under the three working conditions of full-load bending,full-load extreme torsion and full-load braking,the maximum deformations of the carbody are about 0.079 mm,2.968 mm and 2.493 mm respectively,all meeting the requirements of the maximum deformation limit;corresponding to the three working conditions,the maximum stresses of the carbody are 14.996 MPa,86.108 MPa and 45.663 MPa respectively,all meet the limit regulation that the maximum stress shall not exceed 168 MPa.The road excitation frequency is 14.985 Hz,and the first-order natural frequency of the carbody is 19.161 Hz.The natural vibration frequency of the carbody successfully avoids the external excitation frequency,effectively reducing the occurrence of coupling resonance and ensuring good operational stability of the mining truck carbody.

Abstract:To reduce the mass of leaf springs for light trucks while meeting the curb weight limit requirements,glass fiber-epoxy resin composites are used to replace conventional steel for lightweight design and analysis of leaf springs.A geometric model of the composite leaf spring is established using the 3D modeling software Creo.According to the design stiffness requirement of 150.0(1±5％)N/mm,the fiber layup ratio is determined through finite element simulation,and the strength of the leaf spring under static vertical,braking,and cornering conditions is analyzed.Bench tests are carried out to verify the composite samples fabricated by compression molding.The results show that comparing with the original steel leaf spring,when the layup ratio of composite materials with fiber angles of 0° and 45° relative to the sample length direction is 6∶5,the leaf spring mass is reduced from 26 kg to 10 kg,representing a mass reduction of 61.5％.The simulated stiffness of the leaf spring is 153.1 N/mm,and the measured actual stiffness from bench test is 155.0 N/mm,both within the allowable deviation range of the design stiffness.The safety factors of the composite leaf spring under all working conditions are greater than 1.20,and the fatigue life in bench test reaches 300 000 cycles without failure,which meets the application requirements.

Abstract:To improve the assembly quality and cold test performance of diesel engines,based on the basic dataset of diesel engine assembly and cold testing,three standard datasets,namely Seeds,Wine,and Wdbc,from the University of California Irvine(UCI)machine learning repository are selected.The analysis effects of the support vector machines(SVM)model,the SVM model improved by combined intelligent algorithm,and the Transformer model on abnormal cold test data are compared.The results show that the classification accuracies of the SVM,improved SVM,and Transformer models for normal and abnormal data are 85.20％,92.54％,and 97.94％.Compared with the SVM and improved SVM models,the Transformer model has a significantly higher classification accuracy and can be used to analyze parameter anomalies.Exhaust pressure is closely related to torque,higher exhaust pressure leads to increased torque;an excessively long exhaust valve opening time results in abnormal intake vacuum.The effectiveness of the Transformer model in identifying engine assembly anomalies is verified.

Abstract:In response to the problems of ignition difficulty,low flame speed,narrow flammability range,and high NOx emission during ammonia combustion,this paper reviews the characteristics and preparation methods of ammonia fuel,summarizes the application of ammonia in internal combustion engines,analyzes the mechanism of NOx emission generated by ammonia combustion,explores measures to reduce NOx emission,and proposes the development direction of ammonia fuel internal combustion engines.The results show that ammonia fuel has a higher self-ignition temperature,slower flame propagation speed,and longer ignition delay.By optimizing combustion control and mixing with other fuels,the combustion performance can be improved,and environmental pollution can be reduced.Ammonia can be produced through various methods,such as chemical synthesis,biomass conversion,and water electrolysis.Electrochemical synthesis of ammonia is currently one of the most promising pathways for ammonia synthesis.Mixing combustion and oxygen-enriched fuel can increase the combustion rate of ammonia.The NOx generated during ammonia combustion mainly comes from the nitrogen element in ammonia gas.Through technologies such as selective catalytic reduction,staged combustion,moderate or intense low-oxygen dilution combustion,NOx emission during ammonia fuel combustion can be significantly reduced,and the environmental impact of ammonia combustion can be improved.

Abstract:In order to solve the problem that the traditional mechanical governor can hardly meet the performance requirements of modern diesel engines,a proportional integration differentiation(PID)circuit is constructed through operational amplifiers.The circuit includes speed setting module,PID speed regulation module and power amplification module,a multi-functional zero difference electronic governor controller based on analog PID control is designed.Hardware circuit is used to realize the control of starting oil quantity,the switching of idle/rated working condition and the independent adjustment of PID parameters.The test bench test combined with sudden load and sudden unloading working condition verifies the speed regulator control performance.The test bench results show that the speed fluctuation rate is not more than 0.2％under the sudden load and sudden unloading working condition,the steady-state speed regulation rate is 0,the transient speed regulation rate is less than 7％,and stable time of the sudden negative load working condition is about 6～7 s,and the performance meets the secondary speed regulation performance index.The controller has a simple structure and anti-interference ability,and has certain engineering application value.

Abstract:The mode of the acceleration and deceleration process in the transient state of a certain turbojet aero-engine is analyzed.The transient simulation model is established by using AEAYS-606 software.The acceleration and deceleration fuel control algorithm is realized by adjusting the compressor converted speed.The transient working condition simulation is realized by combining the power extraction method.The influence of different acceleration and deceleration control on the performance of the engine is analyzed.The results show that the design of acceleration and deceleration fuel is aimed at the shortest acceleration and deceleration time,and it is necessary to avoid the acceleration and deceleration process.Each parameter should not exceed or approach the stable boundary of each component for the objective.Comparing different controls,it is found that in order to shorten the acceleration time by 2 s,the maximum vortex temperature needs to be increased by 1.4%,the compressor stability is reduced by 4%,and the engine life and stability are drastically reduced.The appropriate acceleration control law should be selected according to the actual application needs of the engine.Comparing different deceleration controls,it is found that the compressor margin is significantly increased,but when the deceleration time is less than 3 s,the minimum air-fuel ratio the main combustion chamber during deceleration is less than the main combustion chamber extinction air-fuel ratio boundary.There is a risk of misfire in the main combustion chamber.

Abstract:To improve engine combustion efficiency and effectively reduce pollutant emissions,the physicochemical properties of alcohol fuels,such as methanol,ethanol,and butanol,and the impacts of alcohol fuels on the performance of engines and fuel cells are summarized.The analysis results show that alcohol fuels can reduce engine pollutant emissions and improve combustion efficiency.And the impact of alcohol fuels on the performance of dual-fuel engines varies with operating conditions,and the comprehensive performance of engines can be effectively improved by synergistically optimizing the fuel injection strategy and EGR rate.When methanol and ethanol are used as fuel cell fuels,the permeability of the proton exchange membrane needs to be improved.The cost of catalysts should be comprehensively considered when the reformed methanol fuel cell is used.

Abstract:Based on three-dimensional numerical simulations,the effects of injection rate shapes with different boot lengths and intake temperatures on the combustion and emission characteristics of a gasoline/biodiesel reactivity controlled compression ignition(RCCI)engine during the starting process are investigated.The results indicate that increasing the boot length increases the late-stage injection rate promotes the atomization and mixing of biodiesel,thereby increases in-cylinder pressure,peak heat release rate,and indicates mean effective pressure while reduces CO emissions,which leads to increased NO emissions.Under the low intake temperature condition,employing a long boot length can improve combustion efficiency and prevent misfire.A higher intake temperature helps improve combustion stability,mitigates the influence of injection rate shape,and significantly reduces CO emission.

Abstract:In order to meet the increasingly stringent requirements for diesel engine pollutant emissions from constantly upgrading emission standards,AVL Cruise M software is used to establish a simulation model of a dual selective catalytic reduction(SCR)system.Based on the world harmonized transient cycle(WHTC),the impact of close-coupled SCR and under flow SCR volume allocation on NOx and N2O emissions,as well as urea injection,is analyzed.The results show that as the volume of close-coupled SCR decreases,the downstream cumulative NOx emissions first decrease and then increase,the cumulative N2O emissions gradually decrease,and the second stage urea injection advances.The volume of the under flow SCR increases,the NOx specific emissions decrease but the N2O specific emissions increase,and the second stage urea injection is delayed.The optimal volumes of close-coupled SCR and under flow SCR are 1/3 V and V(V is the current volume of SCR in a China Ⅵ engine),respectively.At this time,the corresponding cold WHTC,hot WHTC,and weighted NOx specific emissions are 0.609,0.037,and 0.119 g/(kW·h),respectively;the cold WHTC,hot WHTC,and weighted N2O specific emissions are 0.222,0.218,and 0.219 g/(kW·h),respectively.After optimizing the volume allocation of the dual SCR system,both NOx and N2O emissions are lower.

Abstract:In response to the problems of high fuel consumption,high carbon emissions and pollution in traditional fuel mining trucks,a hybrid power system model for extended range mining trucks is established using a series structure architecture based on diesel mining trucks.A composite power following strategy and advanced equivalent consumption minimization strategies(A-ECMS)based on battery state of charge(SOC)feedback are designed.A vehicle model is built based on AVL Cruise,and the control effects of the two energy management strategies are evaluated through joint simulation using MATLAB/Simulink embedded control strategies.The results show that the simulated vehicle speed of the mining truck under both strategies is highly consistent with the required vehicle speed,and the power system can meet the power demand and energy allocation under different operating conditions.Under the A-ECMS strategy,the final SOC of the battery is closer to the target value than the composite power following strategy,with a deviation of only 0.3％and small fluctuations.The equivalent fuel consumption per 100 kilometers is 2.36 L lower than the composite power following strategy.Taking into account the SOC fluctuations of the power battery and the equivalent fuel consumption of the mining truck,the A-ECMS strategy has more advantages.

Abstract:In view of the problems of complex parameter configuration and poor software upgrade adaptability in the traditional development mode of request-response type messages based on controller area network(CAN)bus J1939 protocol,the composition and attributes of five types of message formats are combined with different protocol data unit(PDU)formats,parameter group number(PGN)request message transmission modes corresponding data response and transmission protocol connection management of broadcast announcement message(BAM),request to send(RTS)messages,clear to send(CTS)messages,end of message acknowledgment(EMA)messages and connection abort(CA)messages.The message data processing procedure is optimized,and four data transmission types,namely single packet response to a specific request message in PDU1 format,global single packet response to a specific request message in PDU2 format,multi-packet to a request message in a specific request connection mode in PDU1 format,multi-packet response to a global request broadcast announcement message in PDU2 format,are used for verification.The results show that the processing procedure of the request-response type message after optimizing the data transmission is more flexible in message data configuration,with less calibration parameters,simplified upgrade process,flexible PGN request message recognition and improved adaptive response capability.

Abstract:To solve the problem of water seepage in the cylinder cover during the bench test of a marine engine,systematic physical and chemical inspection methods including macroscopic analysis,non-destructive testing,mechanical property testing,chemical composition analysis,SEM morphology analysis,EDS energy spectrum analysis,and metallographic analysis are adopted to analyze the causes of water seepage,the improvement measures are proposed.The results show that the presence of nodular slag defects inside the cylinder cover is the main cause of water seepage in the marine engine cylinder cover.Under the cyclic operating conditions of the engine bench test,some dense nodular slag defects form channels penetrating the cylinder head wall.By improving the casting process of the cylinder cover and adding air tightness test in the finished product inspection process,the risk of water seepage in the cylinder cover can be effectively prevented.

Abstract:To address the cavitation issue on the outer wall of the six-cylinder diesel engine cylinder liner returned from market validation,the AVL evaluation method is referenced.Simulation analysis is conducted on the cavitation conditions of 12 measurement points on the main thrust side of the cylinder liner by using Abaqus software and the Joukowsky model.On this basis,the piston skirt profile and water pump performance are optimized,and the resulting solutions are validated through simulation and market testing.The results show that the instantaneous coolant pressure at measurement points 4-12 are all below the saturation vapor pressure,indicating a risk of cavitation on the main thrust side of the cylinder liner,which matches the actual cavitation locations.Following the optimization of the piston skirt profile,the peak fluctuation in piston impact velocity on the cylinder liner is reduced from 0.202 m/s to 0.151 m/s,thereby effectively mitigating cylinder liner vibration.In addition,the improvement in water pump performance leads to a 46 kPa increase in coolant pressure on the outer wall of the cylinder liner.The optimized solution passes market testing.For cylinder liner cavitation issues,in addition to traditional methods,approaches such as optimizing the piston skirt profile to suppress cylinder liner vibration and enhancing water pump performance to increase coolant pressure can be adopted.These two methods working together can effectively mitigate cylinder liner cavitation risks.