Search Results

In this paper, the vibration and noise reduction technology for diesel common rail injection system is studied. The NV problems of the injection system come typically from mechanical contacts (injector needle, pump) or fluid pulsations. They are exciting the injection system, which translates the excitations to the engine through the connection points. But it's not easy to identify the characteristic of internal excitation force exactly, so the simulation model based measurement test is considered at here. In order to predict the vibrations due to excitation related with the injection system of the diesel engine, the 1D/3D simulation models are used and the necessary dynamic tests, which are needed to create and validate the models, are done in the test bench.

A fractional recirculation of cabin air was proposed and studied to improve cabin air quality by reducing cabin particle concentrations. Vehicle tests were run with differing number of passengers (1, 2, 3, and 4), four fan speed settings and at 20, 40, and 70 mph. A manual control was installed for the recirculation flap door so different ratios of fresh air to recirculated air could be used. Full recirculation is the most efficient setting in terms of thermal management and particle concentration reduction, but this causes elevated CO₂ levels in the cabin. The study demonstrated cabin CO₂ concentrations could be controlled below a target level of 2000 ppm at various driving conditions and fan speeds with more than 85% of recirculation. The proposed fractional air recirculation method is a simple yet innovative way of improving cabin air quality. Some energy saving is also expected, especially with the air conditioning system.

In-cylinder flows such as tumble and swirl have an important role on the engine combustion efficiencies and emission formations. In particular, the tumble flow which is dominant in current high performance gasoline engines has an important effect on the fuel consumptions and exhaust emissions under part load conditions. Therefore, it is important to understand the effect of the tumble ratio on the part load performance and optimize the tumble ratio for better fuel economy and exhaust emissions. First step in optimizing a tumble flow is to measure a tumble ratio accurately. In this research the tumble ratio was measured, compared, and correlated using three different measurement methods: steady flow rig, 2-Dimensional PIV (Particle Image Velocimetry), and 3-Dimensional PTV (Particle Tracking Velocimetry). Engine dynamometer test was also conducted to find out the effect of the tumble ratio on the part load performance.

As the use of diesel engines increases in the transportation industry and emission regulations tighten, the implementation of diesel particulate filter systems has expanded. There are many challenges associated with the design and development of these systems. Some of the key robustness parameters include regeneration, efficiency, fuel penalty, engine performance, and durability. One component of durability in a diesel particulate filter (DPF) system is the filter's ability to resist ring-off-cracking (ROC). ROC is described as a crack caused primarily by thermal gradients, differentials, and the resulting stresses within the DPF that exceed its internal strength. These cracks usually run perpendicular to the substrate flow axis and typically result in the breaking of the substrate into separate halves.

Conventional EPS (Electric Power Steering) systems are operated by one type of steering tuning map set by steering test drivers before being released to customers. That is, the steering efforts can't change in many different driving conditions such as road conditions (low mu, high mu and unpaved roads) or some specific driving conditions (sudden stopping, entering into EPS failure modes and full accelerating). Those conditions can't give drivers consistent steering efforts. This paper approached the new concept technology detecting those conditions by using vehicle and EPS sensors such as tire wheel speeds, vehicle speed, steering angle, steering torque, steering speed and so on. After detecting those conditions and judging what the best steering efforts for safe vehicle driving are, EPS systems automatically can be changed with the steering friction level and selection of steering optimized mapping on several conditions.

This paper proposes a reference steering wheel torque map and a torque tracking algorithm via steer-by-wire to achieve the targeted steering feel. The reference steering wheel torque map is designed using the measurement data of rack force and steering characteristic of a target performance of the vehicle at transition steering test. Since the target performance of the vehicle is only tested in nominal road condition, various road conditions such as disturbances and tire-road friction are not considered. Hence, the measurement data of the rack force that reflects the road conditions in the reference steering wheel torque map have been used. The rack force is the net force which consists of tire aligning moment, road friction force and normal force on the tire kingpin axis. A motor and a magnetorheological damper are used as actuators to generate the desired steering feel using the torque tracking algorithm.

Applying BSM (Balance shaft module) is a very common and effective way to reduce the 2nd-order powertrain vibration which is caused by the ill-balanced inertia force due to the oscillating masses inside an engine. However, the adoption of a BSM can also produce undesirable things especially in cost, fuel economy, starting performance, and so on. Therefore, for small vehicles, in which case cost and weight are key factors at the development stage, it is often required to develop competitive NVH performance without the expensive apparatus like a BSM. In this paper, in order to develop interior noise and vibration of a 4-cylinder vehicle without a BSM, we analyzed the contribution of some transfer paths for powertrain vibration, and could reduce interior booming noise by tuning the dynamic characteristic of the engine mount which was one of the largest transfer paths.

In this study, the preliminary validation method of the steering system is constructed and the objective is to satisfy the target performance in the conceptual design stage for minimizing the problems after the detailed design. The first consideration about steering system is how to extract the reliable steering effort for parking. The tire model commonly used in MBD(Multi-Body Dynamics) has limited ability to represent deformations under heavy loads. Therefore, it is necessary to study adequate tire model to simulate the behavior due to the large deformation and friction between the ground and the tire. The two approaches related with F tire model and mathematical model are used. The second is how to extract each link’s load in the conceptual design stage. Until now, each link’s load could be derived only by actual vehicle test, and a durability analysis was performed using only pre-settled RIG test conditions.

As the markets require a more environmentally friendly and high fuel consumption vehicle, we have to satisfy bilateral target. Though many new after-treatment techniques like LNT, SCR are investigated to meet both strong emission regulations and low fuel consumption, high cost of these techniques should be solved to adopt widely. This paper describes how to optimize the dual loop EGR as a tool to reduce CO₂ emission of a HSDI diesel engine in the passenger car application. Focus is not only on the optimization to obtain the maximum CO₂ reduction but also on how to assess and overcome various side effects. As a result of careful optimization, as much as 6% CO₂ reduction was achieved by introduction of low pressure EGR loop, maintaining the same boundary conditions as those with high pressure EGR loop only.

The Representative Interactive Flamelet(RIF) concept has been applied to numerically simulate the combustion processes and pollutant formation in the direct injection diesel engine. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF concept has the capabilities to predict the auto-ignition and subsequent flame propagation in the diesel engine combustion chamber as well as to effectively account for the detailed mechanisms of soot and NOx formation. In order to account for the spatial inhomogeneity of the scalar dissipation rate, the Eulerian Particle Flamelet Model using the multiple flamelets has been employed. Special emphasis is given to the turbulent combustion model which properly accounts for vaporization effects on turbulence-chemistry interaction.

This paper presents NVH optimization procedure for the 2.5L I4 common rail diesel engine. Distinctive design feature is the low noise timing chain system which realized by chain case modification and meshing noise improvement. The former was effective for reduction of sound level and the later was for sound quality. Combustion excitation force, vibration transmission in engine structure were also improved and countermeasured to achieve powerful and comfortable Sports Utility Vehicle.

The 3D measurement of a body displacement on a moving vehicle is a quite challenging process. Well-known displacement measuring device such as a dial gauge and strain gauge can measure the displacement in only limited areas. An accelerometer also can estimate body motion but it has an accumulated error and a bias issue for an acquisition of displacements. However, an optical measuring (Motion Capture) method which uses markers and multiple cameras can read 3D coordinates directly and carry out those measurements well. In this paper, first, we determined how to extract a body displacement from global motion. Then we suggested a combining measurement methodology which uses a motion capture and an accelerometer simultaneously. Though it has failed to compensate each result and exact displacement, we showed an accuracy comparison between a motion capture and an accelerometer to measure a displacement along this process.

Recently, regulations on automobile emission have been significantly strengthened to address climate change. The automobile industry is responding to these regulations by developing electric vehicles that use batteries and fuel-cells. Automobile emissions are environmentally harmful, especially in the case of vehicles equipped with high-temperature and high-pressure diesel engines using compression-ignition, the proportion of nitrogen oxides (NOx) emissions reaches as high as 85%. Additionally, air pollution caused by particulate matter (PM) is six to ten times higher compared to gasoline engines. Therefore, the electrification of commercial vehicles using diesel engines could potentially yield even greater environmental benefits. For commercial vehicles battery electric vehicles (BEVs) require a large number of batteries to secure a long driving range, which reduces their maximum payload capacity.

In the path following problem, a commercial vehicle has a delay of a hydraulic steering actuator and slow steering response accordingly. In addition, there are disturbances due to the harsh driving conditions of commercial vehicles. These disturbances may include uncertainties about actuator dynamic delay, modeling error and steering angle sensor offset. Designing a lateral controller with good performance that can overcome this problem is the key to successfully carrying out autonomous driving of commercial vehicles. Usually, it is difficult to consider disturbances with uncertainties in the geometric based control methods. Therefore, this paper proposed a lateral controller using feedback augmented disturbance observer for the commercial vehicle. First, a dynamics was modeled which can describe delay of the hydraulic actuator of the commercial vehicle. After that, a lateral controller was designed based on this dynamics model.

This paper investigated the influence of the injector nozzle geometry on fuel consumption and exhaust emission characteristics of a light-duty diesel engine with 250 MPa injection. The engine used for the experiment was the 0.4L single-cylinder compression ignition engine. The diesel fuel injection equipment was operated under 250MPa injection pressure. Three injectors with nozzle hole number of 8 to 10 were compared. As the nozzle number of the injector increased, the orifice diameter decreased 105 μm to 95 μm. The ignition delay was shorter with larger nozzle number and smaller orifice diameter. Without EGR, the particulate matter(PM) emission was lower with larger nozzle hole number. This result shows that the atomization of the fuel was improved with the smaller orifice diameter and the fuel spray area was kept same with larger nozzle number. However, the NOx-PM trade-offs of three injectors were similar at higher EGR rate and higher injection pressure.

We analyzed the in-cylinder flow fields of an optical-access single cylinder diesel engine with the PIV and STAR-CD CFD code. The PIV analysis was carried out in the bottom and side view mode during a compression stroke (ATDC 220°-340°) at 600 rpm. The flow pattern traced by the streamlines, the location of vortex center, the generation and disappearance of tumble, and the squish effect agreed well, as visualized by the PIV and CFD. Vorticity and spatial fluctuation intensities abruptly increased from ATDC 310, reflecting more complicated flow pattern as approaching TDC. In a quantitative sense, the velocity magnitudes obtained from the PIV were, on an average, higher than those from the CFD by 1 m/s approximately and the difference in velocity magnitude between them was about 26 %. In the CFD analysis, the standard high Reynolds κ-ε and RNG k-ε model were adopted for calculation with tetra and hexa or their hybrid meshes, to determine the turbulence model dependencies.

Drivers continually require steering performance improvement, particularly in the area of feedback from the road. In this study, we develop a new electrically-assisted steering logic by 1) analyzing existing steering systems to determine key factors, 2) modeling an ideal steering system from which to obtain a desirable driver torque, 3) developing a rack force observer to faithfully represent road information and 4) building a feedback compensator to track the tuned torque. In general, the estimator uses the driver torque, assist torque and other steering system signals. However, the friction of the steering system is difficult to estimate accurately. At high speed, where steering feeling is very important, greater friction results in increased error. In order to solve this problem, we design two estimators generated from a vehicle model and a steering system model. The observer that uses two estimators can reflect various operating conditions by using the strengths of each method.

Diesel engines are the most commonly used power train of the freight and public transportations in the world. From the viewpoint of global warming restraint, however, reduction of exhaust emissions from the diesel engine is urgent demand. Stringent emission regulations are being proposed with growing concern on NOx, PM and CO2 emissions. Future emission regulations require advanced emission control technologies, such as SCR(Selective Catalytic Reduction), LNT(Lean NOx Trap) and EGR(Exhaust Gas Recirculation). The EGR is a commonly used technique to reduce emission. In this study, a LP-EGR(Low Pressure Exhaust Gas Recirculation) system was investigated to evaluate its potential on emission reduction and fuel economy improvement, especially for a passenger diesel engine. A 3.0ℓ diesel engine equipped with the LP-EGR system was tested using an in-house control algorithm.

In order to cope with new exhaust emission regulations, automotive industry is interested in research and development of HSDI (High Speed Direct Injection) diesel engines with common rail systems. Since HSDI diesel engine operates under highly loaded condition due to increased power output, cylinder head of HSDI diesel engine is susceptible to high cycle fatigue cracks. In this study, FE analysis was used to find the mechanism of high cycle fatigue crack in the HSDI diesel cylinder head. In order to improve the durability of HSDI diesel cylinder head, the modifications of cylinder head and head bolt pre-load were investigated. Experiments were performed to prove the existence of residual stress created during the heat treatment of cylinder head. The results of experiments showed that residual stress can affect the durability of HSDI diesel cylinder head.

Charge boosting strategy plays an essential role in improving the power density of diesel engines while meeting stringent emissions regulations. In downsized two-stage turbocharged engines, turbocharger matching is critical to achieve desired boost pressure while maintaining sufficiently fast transient response. A numerical simulation model is developed to evaluate the effect of two-stage turbocharger configurations on the perceived vehicle acceleration. The simulation model developed in GT-SUITE consists of engine, drivetrain, and vehicle dynamics sub-models. A model-based turbocharger control logic is developed in MATLAB using an analytical compressor model and a mean-value engine model. The components of the two-stage turbocharging system evaluated in this study include a variable geometry turbine in the high-pressure stage, a compressor bypass valve in the low-pressure stage and an electrically assisted turbocharger in the low-pressure stage.