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Since the amount of emitted CO2 is directly related to car fuel economy, attention is being drawn to DISI (Direct-Injection Spark-Ignition) engines, which have better fuel economy than conventional gasoline engines. However, it has been a problem that the rich air-fuel mixtures associated with fuel films during cold starts due to spray impingement produce particulate matter (PM). In predicting soot formation, it is important to predict the mixture field precisely. Thus, accurate spray and film models are a prerequisite of the soot model. The previous models were well matched with low-speed collision conditions, such as those of diesel engines, which have a relatively high ambient pressure and long traveling distances. Droplets colliding at low velocities have an order of magnitude of kinetic energy similar to that of the sum of the surface tension energy and the critical energy at which the splash occurs.

The combustion process using two fuels with different reactivity, known as dual-fuel combustion or RCCI is mainly studied to reduce emissions while maintaining thermal efficiency compared to the conventional diesel combustion. Many studies have proven that dual-fuel combustion has a positive prospect in future combustion to achieve ultra-low engine-out emissions with high indicated thermal efficiency. However, a limitation on high-load expansion due to the higher maximum in-cylinder pressure rise rate (mPRR) is a main problem. Thus, it is important to establish the operating strategy and study the effect of in-cylinder flow motion with dual-fuel combustion to achieve a low mPRR and emissions while maintaining high-efficiency. In this research, the characteristics of gasoline-diesel dual-fuel combustion on different hardware were studied to verify the effect of the in-cylinder flow motion on dual-fuel combustion.

As fuel injection strategies in spark-ignition (SI) engines have been diversified, inhomogeneous mixing of the fuel-air mixture can occur to varying extents during mixture preparation. In this study, we analyzed the effect of inhomogeneous mixing on the knocking characteristics of iso-octane and air mixture under a standardized fuel testing condition for research octane number (RON), based on ASTM D2699. For this purpose, we assumed that both lean spots and rich spots existed in unburned gas during compression stroke and flame propagation and calculated the thermodynamic state of the spots by using an in-house multi-zone, zero-dimensional SI engine model. Then, the ignition delay was measured over the derived thermodynamic profiles by using rapid compression machine (RCM), and we calculated ξ, the ratio of sound speed to auto-ignition propagation speed, based on Zel’dovich and Bradley’s ξ − ε theory to estimate knock intensity.

Characteristics of syngas combustion at various reforming ratios were studied numerically. The syngas was formed by the partial oxidation of methane to mainly hydrogen and carbon monoxide and cooled to ambient temperature. Stiochiometric and lean premixed flames of the mixtures of methane and the syngas were compared at the atmospheric temperature and pressure conditions. The adiabatic flame temperature decreased with the reforming ratio. The laminar burning velocity, however, increased with the reforming ratio. For stretched flames in a counterflow, the high temperature region was broadened with the reforming ratio. The maximum flame temperature decreased with the reforming ratio for the stoichiometric case, but increased for the lean case except for the region of very low stretch rate. The extinction stretch rate increased with the reforming ratio, implying that the syngas assisted flame is more resistance to turbulence level.

In regard to the evaluation of the performance of a hybrid electric vehicle (HEV), there are as many simulation methods as there are developers or researchers. They adopt different operational algorithms and they use diverse techniques to realize their logic. However, the relation among the various simulation methods has not been clearly defined. Thus, it is not easy to choose a method that would bring the best consequences in the most efficient way. Here, we present three types of backward-looking simulation algorithms for evaluating the fuel efficiency of a power-split HEV. Then the results and cost-effectiveness of each algorithm are analyzed using various component ratings over a representative driving mode. Based on the comparative analysis, the algorithm that uses equivalent fuel consumption is shown to be highly cost-effective. Also, an inductive or empirical base is set up with the results for a component sizing methodology using the recommended simulation.

This paper proposes a new screening attenuation evaluation method (PHSA) for hybrid power cables. Hybrid power cables connect battery, inverter and motor. As the noise and shield characteristics of these cables are different from general communication shield wires, new method for evaluating screening attenuation is needed. We considered the radiation direction, noise current path and various load terminations to evaluate the screening attenuation which is different from standard screening attenuation measurement. Feasibility and effectiveness of the proposed method were verified with real experiment results.

A gasoline homogeneous charged compression ignition (HCCI) called the controlled auto ignition (CAI) engine is an alternative to conventional gasoline engines with higher efficiency and lower emission levels. However, noise and vibration are currently major problems in the CAI engine. The problems result from fast burning speeds during combustion, because in the CAI engine combustion is controlled by auto-ignition rather than the flame. Thus, the ignition delay of the local mixture has to vary according to the location in the combustion chamber to avoid noise and vibration. For making different ignition delays, stratification of temperature or mixing ratio was tested in this study. In charge stratification, which determines the difference between the start of combustion among charges with different properties, two kinds of mixtures with different properties flow into two intake ports.

Exterior shape of automobile can be represented by shape function through this study so that aerodynamic shape parameters can be easily controlled and changed. Also ordinary geometric information can be extracted easily from shape function model by simple calculations. It is possible to predict the aerodynamic performance of functional virtual car models which are transformed continually by developing automated program in initial design stage that includes all of above process. Innovative vehicle design process with exterior design guide will be proposed for stylist, engineer and packaging department in order to achieve low aerodynamic drag and high fuel efficiency targets.

CAI engine is well known to be advantageous over conventional SI engines because it facilitates higher engine efficiency and lower emission (NOx and smoke). However, its limited operation range, large cyclic variation, and difficulty in heat release control are still unresolved obstacles. Previous studies showed that a high load range of the CAI engine is limited mainly by the combustion noise caused by a stiff pressure rise (knock), and that a low load range is also limited by the combustion instability caused by the high dilution of residual gas. In this study, the characteristics of each cycle were analyzed to find the cause of the cycle variation at the high load limit of CAI operation. Moreover, to improve combustion stability, we tested the in-cylinder fuel stratification by applying nonsymmetrical fuel injection to the intake port. Experiments were performed on a PFI single cylinder research engine equipped with dual CVVT and low lift (2 mm) cam shaft with NVO strategy.

The technical feasibility of applying anaerobic digestion for reduction and stabilization of the organic fraction of solid wastes generated during space missions was investigated. This process has the advantages of not requiring oxygen or high temperature and pressure while producing methane, carbon dioxide, nutrients, and compost as valuable products. High-solids leachbed anaerobic digestion employed here involves a solid-phase fermentation with leachate recycle between new and old reactors for inoculation, wetting, and removal of volatile organic acids during startup. After anaerobic conversion is complete, the compost bed may be used for biofiltration and plant growth medium. The nutrient-rich leachate may also be used as a vehicle for nutrient recycle. Physical properties of representative waste feedstocks were determined to evaluate their space requirements and hydraulic leachability in the selected digester design.

An LPG engine for heavy duty vehicles has been developed using liquid phase LPG injection (hereafter LPLI) system, which has regarded as as one of next generation LPG fuel supply systems. In this work the optimized piston cavities were investigated and chosen for an LPLI engine system. While the mass production of piston cavities is considered, three piston cavities were tested: Dog-dish type, bathtub type and top-land-cut bathtub type. From the experiments the bathtub type showed the extension of lean limit while achieving the stable combustion, compared to the dog-dish type at the same injection timing. Throughout CFD analysis, it was revealed that the extension of lean limit was due to an increase of turbulence intensity by the enlarged crevice area, and the enlargement of flame front surface owing to the shape of the bathtub piston cavity compared to that of the dog-dish type.

To improve the cold startability of methanol, methanol-butane mixed fuel was experimented. Engine performance and exhaust emissions are obtained with methanol-butane mixed fuel. These characteristics are compared with those of methanol and gasoline. The mixing ratios of methanol and butane are 50:50 (M50), 80:20 (M80), and 90:10 (M90) based on the calorific value. As a result, M90 produces more power than gasoline and more or less than methanol depending on the engine speed and the excess air ratio. Brake horse power of M90 is higher than that of gasoline by 5 - 10 %, and brake specific fuel consumption is smaller than that of gasoline by 17 % to the maximum based on the calorific value. NOx emission concentrations for M90 are lower than those for gasoline and higher than those for methanol because of the effect of butane, CO emission concentrations are somewhat lower than those for methanol and gasoline.

The role of 1D simulation tool is growing as the engine system is becoming more complex with the adoption of a variety of new technologies. For the reliability of the 1D simulation results, it is necessary to improve the accuracy and applicability of the combustion model implemented in the 1D simulation tool. Since the combustion process in SI engine is mainly determined by the turbulence, many models have been concentrating on the prediction of the evolution of in-cylinder turbulence intensity. In this study, two turbulence models which can resemble the turbulence intensity close to that of 3D CFD tool were utilized. The first model is dedicated to predicting the evolution of turbulence intensity during intake and compression strokes so that the turbulence intensity at the spark timing can be estimated properly. The second model is responsible for predicting the turbulence intensity of burned and unburned zone during the combustion process.

Livengood-Wu integration model is acknowledged as a relatively simple but fairly accurate autoignition prediction method which has been widely recognized as a methodology predicting knock occurrence of a spark-ignition (SI) engine over years. Fundamental idea of the model is that the chemical reactivity of fuel under a certain thermodynamic test condition can be represented by inverse of the acquired ignition delay. However, recent studies show that the predictability of the model seems to deteriorate if the tested fuel exhibits negative temperature coefficient (NTC) behavior which is primarily caused by two-stage ignition characteristics. It is convincing that the cool flame exothermicity during the first ignition stage is a major cause that limits the prediction capability of the integration model, therefore a new ignition delay concept based on cool flame elimination is introduced in order to minimize the thermal effect of the cool flame.

Large-eddy simulation (LES) applications for internal combustion engine (ICE) flows are constantly growing due to the increase of computing resources and the availability of suitable CFD codes, methods and practices. The LES superior capability for modeling spatial and temporal evolution of turbulent flow structures with reference to RANS makes it a promising tool for describing, and possibly motivating, ICE cycle-to-cycle variability (CCV) and cycle-resolved events such as knock and misfire. Despite the growing interest towards LES in the academic community, applications to ICE flows are still limited. One of the reasons for such discrepancy is the uncertainty in the estimation of the LES computational cost. This in turn is mainly dependent on grid density, the CFD domain extent, the time step size and the overall number of cycles to be run. Grid density is directly linked to the possibility of reducing modeling assumptions for sub-grid scales.

Natural gas has been considered as an alternative fuel for a heavy duty diesel engine with its lower pollutant and carbon dioxide emissions than its counterpart. However, due to the high auto-ignition temperature of methane, this alternate fuel has been mainly used in spark-ignited engine with relatively lower compression ratio, losing full potential of achieving high efficiency. To overcome these limitations, high-pressure direct injection of the natural gas in a compression ignition engine has been proposed, and there have been several attempts to understand physical behaviors and ignition of methane jet. In this study, auto-ignition characteristics of high-pressure methane jet were investigated both through the experiment and the multi-zone modeling to suggest the applicability to such engine.

Improving fuel efficiency and emission characteristics are significant issues in engine research. Because the engine has complex systems and various operating parameters, the experimental research is limited by cost and time. One-dimensional (1D) simulation has attracted the attention of researchers because of its effectiveness and relatively high accuracy. In a 1D simulation, the applied model must be accurate for the reliability of the simulation results. Because in-cylinder turbulence mainly determines the combustion characteristics, and mean flow velocity affects the in-cylinder heat transfer and efficiency in a spark-ignited (SI) engine, a number of sophisticated models have been developed to predict in-cylinder turbulence and mean flow velocity. In particular, tumble is a significant factor of in-cylinder turbulence in SI engine.

Validation of a vehicle simulation model of the Chevrolet Volt 2016 was conducted. The Chevrolet Volt 2016 is equipped with the new “Voltec” extended-range propulsion system introduced into the market in 2016. The second generation Volt powertrain system operates in five modes, including two electric vehicle modes and three extended-range modes. Model development and validation were conducted using the test data performed on the chassis dynamometer set in a thermal chamber of Argonne National Laboratory’s Advanced Powertrain Research Facility. First, the components of the vehicle, such as the engine, motor, battery, wheels, and chassis, were modeled, including thermal aspects based on the test data. For example, engine efficiency changes dependent on the coolant temperature, or chassis heating or air-conditioning operations according to the ambient and cabin temperature, were applied.

The optimum design process of the low-temperature condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated. The waste heat recovery system consists of a high-temperature (HT) loop in which water as the HT working fluid recovers waste heat only from the exhaust gas of about 700°C and a low-temperature (LT) loop in which a refrigerant as the LT working fluid recovers heat dissipation from the HT loop, and waste heat from the engine coolant of relatively low temperature. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently.

Radiative heat transfer analysis in a finite cylindrical enclosure with non-gray media and internal heat generations have been conducted. Solutions are generated by a recently developed spherical harmonics method for a finite cylindrical configuration with the weighted sum of gray gases model. Numerical solutions are obtained for temperature and heat flux distributions with the variations of optical thickness and wall emissivity. The results show that with an increase in the absorption coefficient, the heat flux distribution along the lateral wall becomes symmetric regardless of the source distributions. The dependence of heat flux on the wall emissivity is reduced as well. The present solution technique seems to be easily extended to the coupled mode of heat transfer with convection in an engine cylinder.