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Technical Paper

Study of the Injection Control Valve in a New Electronic Diesel Fuel System

At first, the dynamic electromagnetic characteristics of a pulsed solenoid valve is analyzed by experiments. The fast valve response is obtained by material modifications. Then, the intelligent solenoid driving method is discussed. The new techniques of the “active” PWM and the “d2i/dt2” detection are developed for feedback control of the solenoid holding current and the valve closure timing. Finally, the control and diagnosis method for the valve closure duration is investigated. A sensing mechanism utilizing momentary camshaft speed fluctuations of fuel injection pump is presented, which provides the basis for feedback control and diagnosis of the valve closure duration and diesel fuel injection process.
Technical Paper

Control System Design for Variable Nozzle Turbocharger

The electronic control system of the variable nozzle turbocharger (VNT) was designed. The actuator is the electro-hydraulic servo proportional solenoid. The signals of the engine pedal position sensor, the engine speed sensor, the boost pressure sensor, the intake air temperature sensor, and the ambient pressure sensor are sampled and filtered. The engine working condition is estimated. The control algorithm was designed as the closed-loop feedback digital PI control together with the open-loop feed forward control. The gain-scheduled PI control method is applied to improve the robustness. The control system was calibrated at the turbocharger test bench and the engine test bench. The results indicate the designed control system has good performance for the boost pressure control under the steady and transient conditions.
Technical Paper

Study of the Control Strategy of the Plateau Self-adapted Turbocharging System for Diesel Engine

A plateau self-adapted turbocharging system based on variable geometry turbocharger (VGT) technology is proposed to solve the problem of diesel engine operating at plateau. The control strategy of the plateau self-adapted turbocharging system is studied using a GT-Power engine model. The control strategy is based on the optimization of the VGT nozzle vane position at various engine operating conditions and various altitudes. Simulation results show that by optimizing the matching and controlling the VGT, the performance of the engine matched with VGT can be improved significantly compared with the one matched with FGT (fixed geometry turbocharger) at various altitudes. Surge and overspeed phenomena of the turbocharger can also be avoided.
Technical Paper

Integrated System Simulation for Turbocharged IC Engines

An integrated simulation platform for turbocharged internal combustion engines has been developed. Multi-dimensional computational fluid dynamic (CFD) codes are integrated into the system to model the turbocharging circuit, gas circuit, in-cylinder circuit, coolant and oil circuits. As the turbocharger is a critical factor for the IC engine, a turbocharger through-flow model based on mass, momentum, and energy conservation equations has been developed and added in the integrated platform. Compared with the traditional MAP method, the through-flow model can solve the problems of transient matching and lack of numerous experimental maps during the pre-prototype engine design. Partial systems in the integrated platform, such as the in-cylinder flow and combustion circuit, can be modeled by 3-D CFD codes for the investigation of the detailed flow patterns.
Technical Paper

Mixing Effects of Early Injection in Diesel Spray Using LES Model with Different Subgrid Scale Models

Early injection timing is an effective measure of pre-mixture formation for diesel low-temperature combustion. Three algebraic subgrid models (Smagorinsky model, dynamic Smagorinsky model and WALE model) and one-equation kinetic energy turbulent model using modified TAB breakup model (MTAB model) have been implemented into KIVA3V code to make a detailed large eddy simulation of the atomization and evaporation processes of early injection timing in a constant volume chamber and a Ford high-speed direct-injection diesel engine. The results show that the predictive vapor mass fraction and liquid penetration using LES is in good agreement with the experiment results. In combustion chamber, the sub-grid turbulent kinetic energy and viscosity using LES are less than with the RANS models, and following the increasing time, the sub-grid turbulent kinetic energy and viscosity also increase and are concentrated on the spray area.
Technical Paper

Research on Steady and Transient Performance of an HCCI Engine with Gasoline Direct Injection

In this paper, a hybrid combustion mode in four-stroke gasoline direct injection engines was studied. Switching cam profiles and injection strategies simultaneously was adopted to obtain a rapid and smooth switch between SI mode and HCCI mode. Based on the continuous pressure traces and corresponding emissions, HCCI steady operation, HCCI transient process (combustion phase adjustment, SI-HCCI, HCCI-SI, HCCI cold start) were studied. In HCCI mode, HCCI combustion phase can be adjusted rapidly by changing the split injection ratio. The HCCI control strategies had been demonstrated in a Chery GDI2.0 engine. The HCCI engine simulation results show that, oxygen and active radicals are stored due to negative valve overlap and split fuel injection under learn burn condition. This reduces the HCCI sensitivity on inlet boundary conditions, such as intake charge and intake temperature. The engine can be run from 1500rpm to 4000rpm in HCCI mode without spark ignition.
Technical Paper

Relative Impact of Chemical and Physical Properties of the Oil-Fuel Droplet on Pre-Ignition and Super-Knock in Turbocharged Gasoline Engines

A conceptual approach to help understand and simulate droplet induced pre-ignition is presented. The complex phenomenon of oil-fuel droplet induced pre-ignition has been decomposed to its elementary processes. This approach helps identify the key fluid properties and engine parameters that affect the pre-ignition phenomenon, and could be used to control LSPI. Based on the conceptual model, a 3D CFD engine simulation has been developed which is able to realistically model all of the elementary processes involved in droplet induced pre-ignition. The simulation was successfully able to predict droplet induced pre-ignition at conditions where the phenomenon has been experimentally observed. The simulation has been able to help explain the observation of pre-ignition advancement relative to injection timing as experimentally observed in a previous study [6].
Technical Paper

Analysis of Energy Consumption on Typical Main Cylinder Booster Based Brake-by-Wire System

The traditional vacuum booster is gradually replaced by Brake-by-Wire system (BBW) in modern passenger car, especially Electric Vehicle (EV). Some mechanical and hydraulic components are replaced by electronic components in Brake-by-Wire system. Using BBW system in modern passenger vehicles can not only improve the automotive safety performance, reliability and stability, but also promote vehicle maneuverability, comfort, fuel economy and environmental protection. Although vehicle's braking performance is greatly improved by using BBW, the system will inevitably consume some energy of the vehicle power supply, thus introducing unexpected drawback in comparison with the traditional vacuum assist braking system, since it doesn't need any electric power. Therefore, the analysis of energy consumption on typical main cylinder booster based BBW system under typical driving cycles will contribute to advanced design of current advanced braking system.
Technical Paper

Coordinating Control Oriented Research on Algorithm of Engine Torque Estimation for Parallel Hybrid Electric Powertrain System

The internal combustion engine and motor should be controlled coordinately to meet the demand of smooth power transfer and good drivability especially during transient conditions for parallel hybrid powertrain system. This paper presents the essential technology of how to estimate the engine torque by the measurement and processing of instantaneous crankshaft speed. One multi-injection gasoline engine and one turbocharged diesel engine are selected to manifest the algorithm of engine torque estimation and the experiments show fairly good results for both engines. Consequently an engine torque sensor can be easily calibrated and applied to feedback engine torque in coordinating control.
Technical Paper

Improving Combustion and Emission Characteristics in Heavy-Duty Natural-Gas Engine by Using Pistons Enhancing Turbulence

Compressed Natural Gas (CNG), because of its low cost, high H/C ratio, and high octane number, has great potential in automotive industry, especially for heavy-duty commercial vehicles. However, relative slow flame speed of natural gas leads to long combustion duration and low thermal efficiency and tends to cause knock combustion at high load, which will aggravate engine thermal load and reliability. Enhancing turbulence intensity in combustion chamber is an effective way to accelerate flame propagation speed and improve combustion performance. In this study, the flow simulations of several piston bowls with different inner-convex forms were carried out using three-dimensional computational fluid dynamics (3D-CFD) software CONVERGE. The numerical results showed the piston bowls with inner-convex could disturb the charge swirl motion and enhance turbulence of different intensity. A hexagram geometry bowl was proved to have the best function in strengthening turbulence intensity.
Journal Article

Impact of Particle Characteristics and Engine Conditions on Deposit-Induced Pre-Ignition and Superknock in Turbocharged Gasoline Engines

Low Speed Pre-Ignition (LSPI), also referred to as superknock or mega-knock is an undesirable turbocharged engine combustion phenomenon limiting fuel economy, drivability, emissions and durability performance. Numerous researchers have previously reported that the frequency of Superknock is sensitive to engine oil and fuel composition as well as engine conditions in controlled laboratory and engine-based studies. Recent studies by Toyota and Tsinghua University have demonstrated that controlled induction of particles into the combustion chamber can induce pre-ignition and superknock. Afton and Tsinghua recently developed a multi-physics approach which was able to realistically model all of the elementary processes known to be involved in deposit induced pre-ignition. The approach was able to successfully simulate deposit induced pre-ignition at conditions where the phenomenon has been experimentally observed.
Journal Article

Experimental Investigation of the Mechanical Behavior of Aluminum Adhesive Joints under Mixed-Mode Loading Conditions

In recent years, structural adhesives have rapidly become the preferred alternative to resistance spot welding in fabricating stronger, lighter aluminum connections. Connections inevitably undergo and must withstand complex quasi-static and/or dynamic loads during their service life. Therefore, understanding how loading conditions affect the mechanical behavior of adhesive joints is vital to their design and the advancement of structural safety. Quasi-static and dynamic tests are performed to analyze both the strength and failure modes of aluminum 6062 substrates bonded by an adhesive (Darbond EP-1506) for an array of loading directions. An Arcan test device, which enables application of mixed-mode loads ranging from pure peel (mode I) to pure shear (mode II) to the adhesive layer, is employed in quasi-static testing. A self-designed medium-speed test machine is utilized to perform dynamic testing.
Technical Paper

Investigation on Ignition of a Single Lubricating Oil Droplet in Premixed Combustible Mixture at Engine-Relevant Conditions

The ignition of lubricating oil droplet has been proved to be the main factor for pre-ignition and the following super-knock in turbocharged gasoline direct injection engine. In this paper, the ignition process of lubricating oil droplet in combustible ambient gaseous mixture was investigated in a rapid compression machine (RCM). The pre-ignition induction by oil droplet of the ambient gaseous mixture was analyzed under different initial droplet volume and effective temperature conditions. The oil droplet was suspended on a tungsten fiber in the combustion chamber and the ignition process was recorded by a high-speed camera through the quartz window mounted at the end of the combustion chamber. The pressure traces were also obtained by a sensor in order to get the ignition delay and analyze the combustion process in detail.
Technical Paper

Modelling and Simulation of a Magnetorheological Fluid Damper with Multi-Accumulator during Mode Shifting

In continuous controllable damper, there usually exists a compensation chamber with designated initial gas pressure to provide volume compensation while the damper piston is moving up and down. This compensation chamber works as a gas spring to some degree to provide force to the damper rod. In this work, in order to extend the force range of the continuous controllable damper (CCD) and improve the controlling rate, a novel structure of CCD with three additional compensation chambers is proposed. These additional compensation chambers are charged with high, middle and low pressure respectively, with which the damping force range can be rapidly increased or decreased to higher and lower levels through mode shifting. A dynamic model of this novel CCD with coupled effects between the gas and liquid in the damper is developed, and the output force is simulated parametrically in different conditions.
Journal Article

Improved Performance Prediction Model for Turbocharger Compressor

In order to improve centrifugal compressor performance predictive capability, an improved recirculation loss model in two-zone modeling system is presented in this paper. The new loss model correlates Reynolds number of the impeller with the recirculation loss. Performance prediction by the improved model is carried out on two turbochargers with different sizes based on COMPAL mode of the code Concepts. The result shows that predictive performance by improved model is in high accordance with experimental measurement. On the other hand, compared with the larger size compressor, the small one has a performance which is more likely to be influenced by Reynolds number.
Journal Article

Investigation of Flow Structure in a Turbocharger Turbine under Pulsating Flow Conditions

A three-dimensional numerical investigation into aerodynamic feature of the turbocharger turbine under pulsating flow conditions is conducted in this paper. Dual time stepping approach is applied to solve the unsteady Navier-Stokes equations, while the Jameson central scheme is brought in for spatial discretization, and Spalart-Allmaras turbulence model is employed in order to get good viscous resolution, accuracy and computing efficiency. The quasi-steady and unsteady performance of the turbine is given and compared. Five blade passage cross sections are chosen to analyze the structure of the secondary flow at 4 key instants. The developments of different vortex, especially the tip leakage vortex, passage vortex are discussed. The results have shown that the unsteady performance deviates substantially from quasi-steady performance, and the secondary flow structure varies tremendously under the pulsating flow conditions.
Technical Paper

Simulation Research on Engine Speed Fluctuation Suppression Based on Engine Torque Observer by Using a Flywheel ISG

This paper conducts simulation research on engine torque ripple suppression based on the engine torque observer by using a flywheel-ISG (integrated starter generator). Usually, engine torque can be suppressed by using a passive method such as by installing a flywheel or torsional damper. However, failure problems arise in hybrid system because of different mechanical characters of the engine and its co-axial ISG motor. On the prototype test bench, the flywheel of the engine has been removed and replaced by an ISG rotor, namely FISG (flywheel ISG). Besides, the crank and FISG rotor are directly connected, which means no dampers or clutches are installed. If the engine torque ripples can be suppressed by the same level as the flywheel and damper by FISG active torque compensation, the new system can be more compact and economical. Simulation efforts are made to verify its feasibility. Firstly, based on the experimental test bench, which is currently under construction.