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A detailed comparison of cylinder pressure derived combustion performance and engine-out emissions is made between an all-metal single-cylinder light-duty diesel engine and a geometrically equivalent engine designed for optical accessibility. The metal and optically accessible single-cylinder engines have the same nominal geometry, including cylinder head, piston bowl shape and valve cutouts, bore, stroke, valve lift profiles, and fuel injection system. The bulk gas thermodynamic state near TDC and load of the two engines are closely matched by adjusting the optical engine intake mass flow and composition, intake temperature, and fueling rate for a highly dilute, low temperature combustion (LTC) operating condition with an intake O2 concentration of 9%. Subsequent start of injection (SOI) sweeps compare the emissions trends of UHC, CO, NOx, and soot, as well as ignition delay and fuel consumption.

Experiments were performed with a 4-stroke, natural gas fueled SI engine to investigate the effects of several parameters on engine performance under lean operating condition. A favorable effect of charge swirl on stable lean burn operation was observed at a conventional compression ratio. There was an optimum EGR rate which gave a substantial reduction in NOx emissions with minor penalties in efficiency and UHC emissions. Marginal improvement was noticed with lean operations in a long spark duration ignition system. The flame jet ignition system displayed noticeable capability in extending the lean limit. In addition, shadowgraph visualization tests were performed for combustion diagnostic purposes.

Multi-hole diesel fuel injectors have shown significant transients in spreading angle during injections, different than past fundamental research using single-hole injectors. We investigated the effect of a this transient spreading angle on combustion parameters such as ignition delay and lift-off length by comparing a three-hole nozzle (Spray B) and single-hole nozzle (Spray A) with holes of the same size and shape as targets for the Engine Combustion Network (ECN). With the temperature distribution for a target plume of Spray B characterized extensively in a constant-volume combustion chamber, the ignition delay and lift-off length were measured and compared. Results show that the lift-off length of Spray B increases and grows by approximately 1.5 mm after the initial stages of ignition, in an opposite trend compared to Spray A where the lift-off length decreases with time.

The use of clean gaseous fuel in automotive engines has been continuously increased in order to meet the reinforcing emission regulations and to efficiently utilize limited natural resources. Since the liquid phase LPG injection (LPLI) system has an advantage of higher power and lower emission characteristics than the mixer type fuel supply system, many studies and applications have been conducted. However, the heat extraction, due to the evaporation of liquid LPG fuel, causes not only a dropping of LPG fuel but also icing phenomenon that is a frost of moisture in the air around the nozzle tip. Because both lead to a difficulty in the control of accurate air fuel ratio, it can result in poor engine performance and a large amount of HC emissions. The main objective of this study is to examine the characteristics of icing phenomenon and also aims to improve it through the use of anti-icing injection tip. An experimental investigation was carried out on the bench test rig in this study.

A liquid phase LPG injection (LPLi) system has been considered as one of the next generation fuel supply system, since it has a very strong potential to accomplish the higher power, higher efficiency, and lower emission characteristics than the mixer type that is classified as a second generation technology, whereas the LPLi system is classified as a third generation technology. However, when a liquid LPG fuel is injected into the inlet duct of an engine, a large quantity of heat is extracted due to its high latent heat of evaporation. This leads the moisture in the air to freeze around the nozzle exit, which is called icing phenomenon. It may cause damage to the outlet nozzle of an injector or inlet valve seat. In this work, the experimental investigation of the icing phenomenon was carried out. The results showed that humidity of air rather than the temperature of air in the inlet duct mainly controlled the icing process.

Most passenger vehicles employ manual or automatic transmission in their power train. Recently, some automated geared transmission including the dual clutch transmission is gaining popularity for its fuel efficiency and smooth driving as well as convenience. In this study, we are proposing a new much simplified clutchless geared transmission which may transmit most powerful torque employing the power-merge planetary gear system to the final drive during gear shift with excellent smoothness in the transmitted torque. This transmission might work for the most kinds of vehicles having internal combustion engine including the hybrid vehicles.

A thermophoretic particulate sampling device was used to investigate the detailed morphology and microstructure of diesel particulates at various engine-operating conditions. A 75 HP Caterpillar single-cylinder direct-injection diesel engine was operated to sample particulate matter from the high-temperature exhaust stream. The morphology and microstructure of the collected diesel particulates were analyzed using a high-resolution transmission electron microscope and subsequent image processing/data acquisition system. The analysis revealed that spherical primary particles were agglomerated together to form large aggregate clusters for most of engine speed and load conditions. Measured primary particle sizes ranged from 34.4 to 28.5 nm at various engine-operating conditions. The smaller primary particles observed at high engine-operating conditions were believed to be caused by particle oxidation at the high combustion temperature.

High-powered vehicles offer an advantage of superior fuel economy through use of regenerative braking and lowered transient emissions by reducing the operating portion of the engine to follow load as closely as in a conventional bus. A hybrid bus was designed and a prototype was developed. It has a parallel-type hybrid powertrain system and uses a 6-liter diesel engine which satisfy Euro-5 emission standard. 44-kW-electric motor, AMT (automated manual transmission) and Li-ion-type batteries were applied to this hybrid bus. Total 8 hybrid buses are test-running in 6 cities and the driving performances are monitored in terms of fuel efficiency, emission and convenience. This paper presents the performance, major component features and calibration procedures of hybrid powertrain systems. Test run monitoring result showed a benefit of fuel economy at least 36% by comparing to a conventional diesel-powered bus.

A reduced chemical kinetic mechanism for a gasoline surrogate was developed and validated in this study for CAI (Controlled Auto Ignition) combustion. The gasoline surrogate was modeled as a blend of iso-octane, n-heptane, and toluene. This reduced mechanism consisted of 44 species and 59 reactions, including main reaction paths of iso-octane, n-heptane, and toluene. The ignition delay times calculated from this mechanism showed a good agreement with previous experimental data from shock tube measurement. A rapid compression machine (RCM) was developed and used to measure the ignition delay times of gasoline and surrogate fuels in the temperature range of 890K ∼ 1000K. The RCM experimental results were also compared with the RCM simulation using the reduced mechanism. It was found that the chemical reaction started before the end of the compression process in the RCM experiment. And the ignition delay time of the suggested gasoline surrogate was similar to that of gasoline.

Spray characteristics of diesel fuel injection is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the evaporation of atomized fuel and the onset of combustion is relatively short. An investigation into various spray characteristics from different holes of VCO nozzles was performed and its results were compared to standard sac nozzle. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images which were frozen by an instantaneous photography with a spark light source. For better understanding of spray behavior, SMD of the fuel sprays from each hole in the multi hole nozzles were measured with back light imaging while the sprays from the other holes were covered by a purpose-built nozzle cap.

This paper describes the results of a DOE (design of experiment) applied to an exhaust heat exchanger to lower the exhaust gas temperature mainly under high load conditions. The heat exchanger was installed between the exhaust manifold and the inlet of the close-coupled catalytic converter (CCC) to avoid thermal aging. The DOE evaluates the influence of the selected eight design parameters of the heat exchanger geometry on the performance of the exhaust gas cooling system, and the interaction between these parameters. To maximize the heat transfer between exhaust gas and coolant, fins were implemented at the inner surface of the heat exchanger. The design parameters consist of the fin geometry (length, thickness, arrangement, number of fin), coolant direction, exchanger wall thickness, and the length of the heat exchanger. The acceptable range of each design parameter is discussed by analyzing the DOE results.

The compression ignition combustion fuelled with hydrogen and dimethyl-ether was investigated. Exhaust gas recirculation was applied to reduce noise and nitrogen oxide (NOx) emission. When dimethyl-ether was injected earlier, combustion showed two-stage ignitions known as low temperature reaction and high temperature reaction. With advanced dimethyl-ether injection, combustion temperature and in-cylinder pressure rise were lowered which resulted in high carbon monoxide and hydrocarbon emissions. However, NOx emission was decreased due to relatively low combustion temperature. The engine combustion showed only high temperature reaction when dimethyl-ether was injected near top dead center. When exhaust gas recirculation gas was added, the in-cylinder pressure and heat release rate were decreased. However, it retarded combustion phase resulting in higher indicated mean effective pressure.

Combustion in engines can be controlled by the amount of residual gas, which has high temperature and heat capacity compared with fresh charge. Residual gas also acts like a dilution gas during combustion period. Accordingly, combustion duration increases, while the peak combustion temperature and nitrogen oxides (NOx) decreases. Amount of residual gas is affected by pressure difference between exhaust and intake, valve timing and engine speed. The main objective of this work is to identify the effects of exhaust throttle, valve timing and load conditions on residual gas fraction and engine performance. The intake valve open timing was varied freely under fixed exhaust valve close (EVC) timing. Additionally, exhaust throttle has been installed in the exhaust manifold to build up the exhaust back-pressure allowing extra amount of exhaust gases to be admitted into the cylinder during the valve overlap duration.

Transient tests in a 2.0 liter in-line 4 cylinder downsizing gasoline direct injection engine were conducted under various transient conditions in order to investigate effects of lower rotational inertia of titanium aluminide alloy (TiAl) turbine wheel on engine and turbocharger performances. As a representative result, fast boost pressure build up was achieved in case of TiAl turbocharger compared to Inconel turbocharger. This result was mainly due to lower rotational inertia of TiAl turbine wheel. Engine torque build up response was also improved with TiAl turbocharger even though engine torque response gap between both turbochargers was slightly reduced due to retarded combustion phase. In addition, with advanced ignition timing, fuel consumption became less than that of Inconel turbocharger with similar engine torque response.

The effects of hydrogen ratio and exhaust gas recirculation (EGR) on combustion and emissions in a hydrogen/diesel dual-fuel premixed charge compression ignition (PCCI) engine were investigated. The control of combustion phasing could be improved using hydrogen enrichment and EGR due to the retarded combustion phasing with a higher hydrogen ratio. The indicated mean effective pressure (IMEP) was increased with a higher hydrogen ratio because the hydrogen enrichment intensified the high temperature reactions and thus decreased the combustion duration. Hydrocarbon (HC) and carbon monoxide (CO) emissions were reduced significantly in a hydrogen/diesel dual-fuel PCCI mode with a similar NOx emissions level as that of the diesel PCCI mode.

Intake-generated in-cylinder flow and subsequent combustion characteristics were studied respectively in a 4-valve spark ignition engine. The flow characteristics of four-valve cylinder head were examined under a steady flow condition for intake ports with three different entry angles; θ=15°, 20° and 25°. The velocity and angular momentum distributions in the tumble adaptor were measured with PIV (Particle Image Velocimetry). Subsequent effects of tumble flow generated by various intakes ports on the lean burn characteristics were also investigated. The lean burn performances were examined in a four-valve pentroof engine. The combustion duration under lean mixture conditions was calculated by heat release analysis of the pressure trace. The results show that flow structure is complicated by valve interference at low valve lift.

Diesel fuel injection system is the most important part of the direct-injection diesel engine and, in recent years, it has become one of the critical technologies for emission control with the help of electronically controlled fuel injection. Common rail injection system has great flexibility in injection timing, pressure and multi-injections. Many studies and applications have reported the advantages of using common rail system to meet the strict emission regulation and to improve engine performance for diesel engines. The main objective of this study is to investigate the effect of pilot-, post- and multiple-fuel injection strategies on engine performance and emissions. The study was carried out on a single cylinder optical direct injection diesel engine equipped with a high pressure common rail fuel injection system. Spray and combustion evolutions were visualized through a high speed charge-coupled device (CCD) camera.

Exhaust gas recirculation (EGR) and lean burn utilize the diluents into the engine cylinder to control combustion leading to enhanced fuel economy and reduced emissions. However, the occurrence of excessive cyclic variation with high diluent rates, brings about an undesirable combustion instability within the engine cylinder resulting in the deterioration of both engine performance and emissions. Proper stratification of mixture and diluents could improve the combustion stability under high diluent environment. EGR stratification within the cylinder was made by adopting a fast-response solenoid valve in the midst of EGR line and controlling its timing and duty. With EGR in both homogeneous mode and stratified mode, in-cylinder pressure and emissions were measured. The thermodynamic heat release analysis showed that the burning duration was decreased in case of stratified EGR. It was found that the stratification of EGR hardly affected the emissions.

In order to reduce hydrocarbon emission in gasoline engine, especially during warming-up period, it is necessary to estimate the fuel and fuel product flow rate in the emission gas. The intake airflow rate should also be estimated. A strategy was proposed to estimate air fuel ratio in a spark ignition engine. The mass of air in the cylinder was determined by filling-emptying method, and the fuel in the intake manifold and cylinder was estimated by the “wall-wetting” effect calculation. The use of graphical dynamic system control software is becoming more popular as automotive engineers strive to reduce the time to develop new control systems. The rapid prototype engine controller has been developed by using MATLAB, SIMULINK, REAL TIME WORKSHOP, xPC Target, and WATCOM C++. The sensor data from the engine will be transferred to computer, and the fuel delivery will be calculated.

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.