The Research Of Sequential Turbocharging And Controllable Intake Swirl Composite System Diesel Engine

Sequential turbocharging technology can expand the power operating range of a dieselengine, improve the economy in low conditions and reduce harmful emissions, which is themost effective way to improve the performance of the medium-speed or high-speedhigh-power diesel engine in low condition and being applied for more and more types ofdiesel engine. Based on the original TBD620V16diesel engine with controllable vortexsystem, modification on the sequential turbocharging system is made in this paper, whichmakes the original engine into a compound system with sequential turbocharging system andcontrollable vortex system, the results show that the diesel engine with this compound systemcan improve the low-condition performance, expand the operating range, increase theeconomy. The main contents of this article as follows:1. The study of3D dynamic flow field of these three systems, sequential turbochargingsystem, controllable vortex system and the compound system.3D model of the Intake andexhaust ports-valves-cylinder is established based on the actual structure, in whichunstructured hexahedral is used in grid, the grid movement is the stretch of the prismatic layer,a transient-3D-compressible-viscous flow hypothesis is made, and ak εmodel is chosen tobe the turbulence model, this flow field of this model is calculated by SIMPLE algorithm.After the verification of this model by using the data of the steady flow test, analysis on theflow field is made, which is focus on the flow field of the DC inlet port and spiral inlet port,and also a quantitative analysis on variation of the flow field parameters at the same inlet andexhaust valve position is made, by analyzing and comparing the performance data of thewhole engine, the results show that it is advisable to remove the baffle in controllable vortexsystem and retain the spiral inlet port, so the compound system with sequential turbochargingsystem and controllable vortex system is composed.2. The study of the combustion process of the TBD620V16diesel engine compoundsystem. By comparing the combustion process of the controllable vortex system and thecombustion process of the compound system, it shows that the emissions of the latter systemare significantly reduced. The fuel injection system parameters(injection advance angle, spraycone angle) of the compound system is optimized, the calculation results are in agreement inrated condition, switching point condition and the low condition: the delay of the injection advance angle, lower NOx resultant, more Shoot emissions, so the best injection advanceangle is20。BTDC; the best spray cone angle is155°in original engine, because the spraycone angle impacts the fuel distribution in space.3. The study of empirical formulas of the heat release rate of the TBD620V16dieselengine compound system. Heat release rate of the TBD620V16diesel engine compoundsystem in low condition is analyzed based on the large number of experiment data,mathematical fitting of the curse of heat release rate is made by3-Viebe function, appropriateempirical expression of the characteristic parameters of heat release rate in low condition isderived by simplex method, and the mathematical expression of the variation amongcharacteristics parameters in low condition, load and speed is presented.4. The study of the working process of the TBD620V16diesel engine compoundsystem. A simulation model of the TBD620V16sequential turbocharging diesel engine isestablished in GT-POWER software, in which appropriate3-Viebe characteristic parametersare chosen in combustion model, parameters of fuel injecting system is changed, after theimpacts of the swirl ratio on working process is introduced, simulation of multiple operationconditions in accordance with the standard propeller characteristics is carried out, and theswitching point of TBD234V16diesel engine with compound system is predicted.5. The study of the TBD620V16diesel engine compound system. A morecomprehensive study is carried out, the max running border of the engine is obtained bylimiting characteristic test; the universal characteristic and the operating range of the engineis obtained by load characteristic test in low condition; the performance parameters of theengine in accordance with the standard propeller characteristics is obtained by propellercharacteristic test, and the switching points of the sequential turbocharging is chosen. The testshows that the low-condition performance of TBD234V16diesel engine with compoundsystem can be improved significantly, the operating range is expanded, economy is improveby a single turbocharger when working under low condition.