Reduction of emissions with propane addition to a diesel engine

Recent studies on dual-fuel combustion in compression-ignition (CI) engines, also known as diesel engines, fall into two categories. In the first category are studies focused on the addition of small amounts of gaseous fuel to CI engines. In these studies, gaseous fuel is regarded as a secondary fuel and diesel fuel is regarded as the main fuel for combustion. The objectives of these studies typically involve reducing particulate matter (PM) emissions by using gaseous fuel as a partial substitution for diesel fuel. However, the addition of gaseous fuel raises the combustion temperature, which increases emissions of nitrogen oxides (NO_x). In the second category are studies focused on reactivity-controlled compression-ignition (RCCI) combustion. RCCI combustion can be implemented by early diesel injection with a large amount of low-reactivity fuel such as gasoline or gaseous fuel. Although RCCI combustion promises lower NO_x and PM emissions and higher thermal efficiency than conventional diesel combustion, it requires a higher intake pressure (usually more than 1.7 bars) to maintain a lean fuel mixture. Therefore, in this study, practical applications of dual-fuel combustion with a low air-fuel ratio (AFR), which implies a low intake pressure, were systemically evaluated using propane in a diesel engine. The characteristics of dualfuel combustion for high and low AFRs were first evaluated. The proportion of propane used for four different operating conditions was then increased to decrease emissions and to identify the optimal condition for dual-fuel combustion. Although the four operating conditions differ, the AFR was maintained at 20 (? approximately equal to 0.72) and the 50% mass fraction burned (MFB 50) was also fixed. The results show that dual-fuel combustion can reduce NO_x and PM emissions in comparison to conventional diesel combustion.     

Investigation of regenerative and Anti-lock Braking interaction

The use of a regenerative braking mode can reduce overall vehicle energy usage for most of the most common drive cycles. However, a number of technical issues restrict the use of regenerative braking for all possible braking situations. These issues are concerned with two key limitations. The first is related to physical limitations of the applied regenerative braking system, e.g. Electric Motor (E-Motor) power limits; energy storage device capacity and vehicle load transfer etc. The second limitation results from the potentially detrimental interaction between regenerative braking and the Anti-locking Braking System (ABS). The first type of limitation can, to some extent, be alleviated by suitable choice of hardware and, as a consequence, will not be discussed further in this paper. The second type of limitation concerns the regenerative braking strategies during an ABS event. Some of the regenerative braking strategies designed and investigated within the Low Carbon Vehicle Technology Project (LCVTP) will be described and analyzed in this paper. A comparison of competing strategies is made and conclusions are drawn together with suggestions for further research. The work has been progressed as a part of a major research programme; namely the LCVTP, which has been conducted within an extensive industrial and academic partnership, mutually funded by the European Regional Development Found and Advantage West Midlands.     

Measurement of roof deformation caused by vehicle rollover

A vehicle rollover is a critical accident that could have many causes. This paper describes a novel vision-based system for measuring vehicle roof deformation due to a rollover accident. A vision-based measurement system offers an overall view of structural deformation simply at low cost. Our measurement system was constructed using a Kinect camera from Microsoft, a battery, and a remote-controlled recording computer. Color images and distance maps can be obtained using two sensors embedded in the Kinect along with customized software, and the distance from the camera lens to a specific object can be calculated with a simple equation. To test our proposed approach, actual vehicle rollover experiments were conducted and the resulting roof deformations were compared to those indicated by our system. Moreover, cross-sectional image of Apillar was analyzed to calculate bending moment of inertia. From the research results, it was able to show that deformation errors were within 13 mm, and roof deformation was correlated with vehicle type, or vehicle curb weight.     

Investigation of engine restart stability after idle stop for a mild type HEV powertrain

Stringent regulations on exhaust emissions and fuel economy for vehicles have become major issues in the automotive industry. Hybrid electric vehicles (HEV) are one of the crucial alternative plans to current conventional vehicles, but they have drawbacks, which include increases in total hydrocarbon (THC) emission from the engine and deterioration of the combustion stability with frequent stopping and restarting of the engine. Intake port fuel film is evaporated up during the deceleration state due to the fuel-cut. The λ (relative A/F ratio) at engine restart is lean because part of injected fuel is used to form the fuel film in the intake port. This study revealed the behavior of a fuel film in engine stop with fuel-cut and in engine restart with a simulation model. To investigate the fuel film characteristics, a simulation model was applied and validated with a single-cylinder engine. The simulation result shows that λ of at least 1.2 is required for a stable engine restart. The minimum injection quantity of the first cycle for stable combustion is suggested to be at least 240% of the steady-state idle condition.     

Assessment of risky driving caused by the amount of time focused on an in-vehicle display system

Korea is currently experiencing a rapidly increasing distribution rate of in-vehicle display devices, such as navigation or DMB displays, owing to remarkable advances in IT. At the same time, the number of traffic accidents and traffic violations is increasing due to the distraction of drivers’ attention by such devices. In particular, in-vehicle display devices such as navigation systems temporarily distract drivers’ visual or cognitive attention when they perform a unit task. Accordingly, it is necessary to prepare adequate standards to regulate in-vehicle display devices, especially in Korea. There are few empirical studies that have employed experiments to support such regulation. In this study, an experiment was conducted using a driving simulator to establish the proper standards regarding the maximum distraction time per unit task that can be allowed without causing any disturbance in safe driving. A total of 25 participants participated in the experiment. The distraction time was controlled by asking participants to perform the two tasks at once: while participants were driving as a primary task, they performed secondary task that count the number of intersections between the start point and the arrival point displayed on the screen. The results showed that the 2.0 second condition differed from the controlled condition in the deviation in the distance from the preceding vehicle, speed, and steering wheel movement, whereas there were no differences between the controlled condition and the 1.0 or 1.5 second condition. Finally, the limitations of the study and the implications of the findings with regard to future studies and application of the Korean version of guidelines for in-vehicle display devices are discussed.     

Optimal fuel-cut driving method for better fuel economy

Eco-drive methods are being applied in modern passenger cars in the form of LCD displays showing real-time fuel consumption rates. The eco-drive is one of the most promising methods to enhance the fuel economy of vehicles. The ecodrive method can be made more effective by using the fuel-cut function. The fuel is not injected when the driver does not depress the gas pedal of a vehicle with engine speeds higher than approximately 1,500 rpm above the mid-vehicle speed range. This function is known as the fuel-cut function, and almost every modern vehicle is equipped with this function. The fuel-cut is most frequently activated on downhill sections of highway. Therefore, the CO₂ exhausted from the vehicle can be zero in this downhill section. In this study, the fuel-cut function is simulated with CRUISE of AVL to find the most effective driving pattern in downhill sections. Simulations with the CRUISE software showed that the lower limit of the vehicle speed for fuelcut should be raised to improve fuel economy on steeper downhill sections. The fuel economy can be optimized when the fuelcut coasting and reacceleration is completed in the downhill part of the road. The simulation result was also compared to previous test results. Fuel consumption was reduced by approximately 4% in both the experimental and simulated results for the West Coast Highway in South Korea.     

Properties of roadway particles from interaction between the tire and road pavement

A large fraction of urban PM₁₀ concentrations is due to non-exhaust traffic emissions, including road dust, particles from tire/road interface, and brake lining particles. Although potential health and environmental impacts associated with tire wear debris have increased, few environmentally and biologically relevant studies of actual tire wear debris have been conducted. Tire wear particles (TWP) are released from the tire tread as a result of the interaction between the tire and the pavement. Roadway particles (RP), meanwhile, are particles on roads composed of a mixture of elements from tires, pavement, fuels, brakes, environmental dust, and the atmosphere. The main objective of the present study is to identify the contribution of tires to the generation of RP and to assess the potential environmental and health impacts of this contribution. First, a mobile measurement system was constructed and used to measure the RP on asphalt roads according to vehicle speed. The equipment of the mobile system provides PM₁₀ concentration by DustTrak DRX, and mass and number size distribution of fine and ultrafine particles by a fast mobility particle sizer (FMPS) and an aerosol particle sizer (APS). The dependence of RP mass and particle number concentration on vehicle speed was observed. It was also found that many particles were generated by rapid deceleration of the vehicle.     

Comparison of driving characteristics between drivers in Korea and in the united states of America based on driver-vehicle interaction field database

Research and development involving intelligent vehicles of today is geared to safe, driver-friendly and sensitive vehicles that provide a driver with a pleasant and convenient driving environment while preventing him or her from possible risks of accident. In developing convenient and safe vehicles, research on drivers’ driving patterns, reactions and state characteristics depending on road conditions in actual field is essential in order to devise more driver-friendly intelligent vehicles. This paper describes how a driver-vehicle interaction (DVI) field database is built in order to obtain a driver’s input in normal road driving condition on highways, country roads, and city roads, and his or her state information, as well as data on the vehicle and traffic conditions. And the newly built database is compared with the RDCW FOT database established by UMTRI of the US for analysis to suggest that the driving tendencies of drivers in Korea and the road driving conditions are not the same as those in the US, reconfirming the need to establish a DVI field database, which will be used for the development of intelligent vehicles suitable for the Korean environment. The DVI data collected from actual driving in field are anticipated to be widely utilized as basic data for research on various intelligent driving safety systems, advanced driver assistance systems (ADAS) and human-vehicle interface (HVI) that are suitable for the driving environment in Korea.     

Design methodology of component design environment for PHEV

In this study, the design methodology for PHEV component design environment is proposed, which consists of power evaluation, component evaluation, component analysis and vehicle performance evaluation environments. First, PHEV simulators were developed based on the dynamic model of the target PHEV powertrain, and a PHEV control algorithm was designed based on the general power-split type PHEV using MATLAB/Simulink. Experimental results were used to validate the constructed PHEV simulators. The power evaluation environment provides the magnitude and direction of the power between components at the vehicle level at any selected time that the user wants to evaluate. The component evaluation environment is designed to evaluate the parameter behaviors of a component using the effort-flow causality relationship. The component analysis environment is designed to investigate component performance according to the variations of component parameters. The vehicle evaluation environment is designed to evaluate equivalent fuel economy at any selected time. It is expected that the design methodology of the PHEV component design environment proposed in this study can be extended to other x-EVs for evaluating and designing vehicle components.     

Numerical analysis of homogeneous mixture formation for a direct injection liquid LPG engine

A method to form a homogeneous mixture using low pressure direct injection of liquid phase LPG, pent-roof combustion chamber, flat-top piston and center-located injector layout is presented. To validate the method, the mixture formation processes in the cylinder were investigated using the CFD code. The effect of different injection timing and engine loads on the mixture formation processes were researched. The simulated results showed that, the intake tumble for high load conditions or the inclined intake swirl for part load conditions would break into small-scale vortex (turbulence) near the end of compression stroke, which enhanced the homogeneous mixture formation. The results also showed that if the liquid phase LPG was injected at 60–80°CA ATDC in intake stroke even at different loads, the homogeneous mixture would be formed under any engine load conditions.