Research On Fuel-air-chamber Optimization Matching Of Controllable Intake Swirl Diesel

As the energy crisis and the environmental problems have become increasinglyprominent, the higher requirements of the economy, dynamic property and emission of dieselengine have been brought forward. So that the higher power density, lower fuel consumptionsand lower emissions would be the development orientation of modern diesel engine. There aremany factors impacting the engine performance indicators, and among them the fuel system,the air intake system and the combustion system of diesel engine are the most important.Therefore, the optimized matching technology of the diesel fuel-air-chamber is paid more andmore attention.At present, most of the fuel-air-chamber researches on controllable intake swirl diesel areless focus on comprehensively analyzing the matching and the inner connection between thefuel, air and chamber, but on single system. Especially on the combustion system ofcontrollable intake swirl diesel engine,1D simulation analysis had been carried out mostly inprevious studies, and fully systematic3D combustion analysis was less been done.According to present research situation, this paper took one controllable intake swirldiesel as the study object, proposed the optimization design schemes which were based on thecalculation analysis for the fuel injection system, the air intake system and the combustionsystem, in order to realize the diesel fuel-air-chamber optimized matching. Also the specialtests of the air intake system and the fuel injection system had been done to verify theaccuracy of the calculation analysis. During the process of system analysis and optimizationdesign, to reveal the inner mechanism of each system of the controllable intake swirl diesel,and using the modern analysis technology to optimize and to match the dieselfuel-air-chamber, the system optimization overall the diesel engine was achieved. The mainresearch work includes the following aspects:Firstly, by adopting the specialty software HYDSIM, the fundamental characteristics ofthe pump-tube-nozzle type diesel fuel injection system and the rules of performanceindicators changing with structure parameters have been studied in order to makeoptimization design of the controllable intake swirl diesel engine fuel injection system. Toimprove the injection spray characteristics, the key structure parameters such as the fuelinjection pump plunger diameter, the high-pressure tube diameter and the length-diameterratio of the nozzle holes have been optimized. Meanwhile, by studying the inner influence mechanism of the fuel injection characteristics and spray quality, the results could provide thetheoretical basis and calculated data for the optimization design of the fuel injection systemand the follow-up studies on combustion analysis and injection spray field test in cylinder.Secondly, by using the CFD software FIRE, the calculation analysis on the intake flowfield of the controllable intake swirl diesel engine have been done. The detailed studies are onthe influence rules of the diesel intake flow field impacted by the valve lift, the bafflestructure and the intake airway structure. Analyzing some key performance indicators such asthe swirl ratio, the flow coefficient, the air velocity and pressure of the diesel air intakesystem in operation conditions with different valve lifts and different intake baffle angles is tostudy the formation mechanism of diesel intake swirl. Based on the detailed analysis on theair intake system of the controllable intake swirl diesel, the structure optimizations on thebaffle and the intake port have been done to improve the intake swirl and inlet flow, and toachieve the optimization design of the diesel air intake system.Thirdly, by adopting the combustion analysis software FIRE, the3D burning calculationanalysis and optimization design in cylinder of the controllable intake swirl diesel have beentaken. The influence rules analysis of the swirl ratio impacting the fuel spray situation, thefuel-air mixture and in-cylinder combustion situations have been paid great attention.Comparatively analyzing the different injection laws effecting the in-cylinder combustionperformance indicators, the detailed studies on the influence rules that the injection lawsaffected the emission indicators, spray atomization and fuel-air mixture of the diesel engineare conducted, and obtained the final optimal fuel injection law. By studying the influencerules of the baffle structure and intake port structure of the diesel air intake system effectingthe in-cylinder combustion process, the optimization structure parameters of the baffle andintake port could be gained. Then the optimal matching design of the diesel fuel-air-chamberhave been finished.According to the air intake system physical structures of the controllable intake swirldiesel engine, the steady flow test rig of the air intake system should be built to finish theexperiment design. The key performance indicators of the air intake system such as the swirlratios and the flow coefficients are measured under the conditions of different valve lifts anddifferent baffle angles in the test. The comparative analysis between the measured data andthe calculated data verifies the accuracy of the flow field calculation.A spray test rig of the controllable intake swirl diesel engine with double intake portshave been set up to dynamically measure the injection spray process with the visualizationtechnology and the high speed photography. The detailed study on the influence rules of the intake swirl impacting the penetration, spray angle and fuel-air mixture situations are done toanalyze the effects of different intake swirl ratios in spray macro states. The accuracy of thein-cylinder fuel-air mixture calculation results is validated by the field test data of the spraytest, and the spray test lays the basis of the inner mechanism research on spray atomization ofthe diesel engine.