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In this study, macroscopic spray characteristics of Waste cooking oil (WCO), Jatropha oil, Karanja oil based biodiesels and baseline diesel were compared under simulated engine operating condition in a constant volume spray chamber (CVSC). The high pressure and high temperature ambient conditions of a typical diesel engine were simulated in the CVSC by performing pre-ignition before the fuel injection. The spray imaging was conducted under absence of oxygen in order to prevent the fuels from igniting. The ambient pressure and temperature for non-evaporating condition were 3 MPa and 300 K. Meanwhile, the spray tests were performed under the ambient pressure and temperature of 4.17 MPa and 804 K under evaporating condition. The fuels were injected by a common-rail injection system with injection pressure of 80 MPa. High speed Mie-scattering technique was employed to visualize the evaporating sprays.

Steady and transient tests in a downsizing Gasoline Direct Injection (GDI) in-line 4 cylinders 2.0 liter engine were carried out to investigate characteristics of turbocharger with Titanium aluminide (TiAl) turbine wheel. The density of TiAl material is lower than Inconel 718 (Inconel) which is raw material for conventional turbine wheel. The objective of this study was to investigate the effect of light rotational inertia of turbine wheel on engine performance. Performance of TiAl turbine wheel turbocharger itself was also compared to that of Inconel turbine wheel turbocharger. Except for the turbine wheels, all experimental conditions were matched to be the same load and engine speed conditions. The compressor total-to-total pressure ratio of TiAl turbocharger was higher under part load condition due to higher turbocharger speed of TiAl turbocharger, which was led by lower rotational inertia of TiAl turbine wheel, while the engine performance was not much improved.

A diesel-fueled premixed charged compression ignition (PCCI) combustion technique using a two-stage injection strategy has been investigated in a single cylinder optical engine equipped with a common-rail fuel system. Although PCCI combustion has the advantages of reducing NOx and PM emissions, difficulties in vaporization of a diesel fuel and control of the combustion phase hinder the development of the PCCI engine. A two-stage injection strategy was applied to relieve these problems. The first injection, named as main injection, was an early direct injection of diesel fuel into the cylinder to achieve premixing with air. The second injection was a diesel injection of a small quantity (1.5 mm3) as an ignition promoter and combustion phase controller near TDC. Effects of injection pressure, injected fuel quantity and compression ratio were studied with variation of an intake air temperature.

The application of dual-fuel combustion in the freight transportation sectors has received considerable attention due to the capability of achieving higher fuel efficiency and less pollutant emissions than the conventional diesel engines. In this study, high-speed flame visualization was used to investigate the phenomena of natural gas/diesel dual-fuel combustion in a single-cylinder heavy-duty engine with optical access. To implement diverse fuel blending conditions, diesel injection timing and natural gas substitution ratio were varied under constant fuel energy input. A novel flame regime separation method was implemented based on color segmentation in HSV color space to characterize the spatial distributions of premixed and non-premixed flame regimes. Flame images for larger natural gas substitution showed a significant reduction in the non-premixed flame regime accompanied by flame propagation along the vaporized diesel sprays.

The effect of biodiesel produced from waste cooking oil (WCO) on the soot particles in a compression ignition engine was investigated and compared with conventional diesel fuel. The indicated mean effective pressure of approximately 0.65 MPa was tested under an engine speed of 1200 revolutions per minute. The fuels were injected at an injection timing of −5 crank angle degree after top dead center with injection pressures of 80 MPa. Detailed characteristics of particulate matters were analyzed in terms of transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and elemental analysis. Soot aggregates were collected on TEM grid by thermophoretic sampling device installed in the exhaust pipe of the engine. High-resolution TEM images revealed that the WCO biodiesel soot was composed of smaller primary particle than diesel soot. The mean primary particle diameter was measured as 19.9 nm for WCO biodiesel and 23.7 nm for diesel, respectively.

In this study, premixed charge compression ignition (PCCI) combustion was implemented using an injector that had a narrow injection angle of 70° and a moderately early injection timing of -40° crank angle after top dead center (CA ATDC). In-cylinder pressure measurements and high-speed direct imaging of the flame were performed in an optically accessible single-cylinder diesel engine. Frequency analysis of the acquired in-cylinder pressure data was carried out to obtain the frequency range of diesel knock. Meanwhile, image segmentation and a tracking algorithm based on YCbCr color space were implemented to determine the frequency range of diesel knock from the obtained high-speed image. The results show that the frequency of diesel knock was dominated by the range from 13 kHz to 15 kHz. Still, frequency with low power existed down until 7 kHz. The frequencies of the area movement were shown to be 13 kHz and, in some cases, 8.67 kHz.

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.

Dimethyl Ether (DME) has been considered as one of the most attractive alternative fuels for compression ignition engine. Its main advantage in compression-ignition engine application is high efficiency of diesel cycle with soot free combustion though conventional fuel injection system has to be modified due to the intrinsic properties of the DME. Experimental study of the DME and conventional diesel spray employing a common-rail type fuel injection system with a sac type injector was performed in a constant volume vessel pressurized by nitrogen gas. A CCD camera was employed to capture time series of spray images, so that spray cone angles and penetrations of the DME spray were characterized and compared with those of diesel. Intermittent hesitating DME spray appeared at injection pressures of 25MPa and 40MPa in both atmospheric and 3MPa chamber pressures.

Adaptive valve timing control is one of the promising techniques to accomplish the optimized mixture formation and combustion depending on the load and speed, which is needed to meet the future challenges of reducing fuel consumption and exhaust emissions. The behavior and the effect of adaptive valve timing control system has been investigated by computer simulation, which simulates the gas dynamics in engines. These programs are typically one-dimensional including complex flow features as ‘special’ boundaries. A code adopting 2-step Lax-Wendroff method with artificial damping terms called FCT(Flux Corrected Transport), was developed to investigate the influence of operational and design parameters on the performance of engines. The effects of adaptive valve timing control system on volumetric efficiency or engine torque, and pumping loss were investigated. It increased low end torque by about 6%, and reduced pumping loss drastically at low load, high engine speed conditions.

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.

An experimental study was conducted to investigate the impact of injection parameters on the combustion and emission characteristics in a compression ignition engine fuelled with neat waste cooking oil (WCO) biodiesel. A single-cylinder diesel engine equipped with common-rail system was used in this research. The test was performed over two engine loads at an engine speed of 800 r/min. Injection timing was varied from −25 to 0 crank angle degree (CAD) after top dead center (aTDC) at two different injection pressures (80 and 160 MPa). Based on in-cylinder pressure, heat release rate was calculated to analyze the combustion characteristics. Carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and smoke were measured to examine the emission characteristics. The results showed that the indicated specific fuel consumption (ISFC) of WCO biodiesel was higher than that of diesel. The ISFC was increased as the injection timing was advanced and injection pressure was increased.

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.

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.

Most internal combustion engine makers have adopted after-treatment systems, such as selective catalytic reduction (SCR), diesel particulate filter (DPF), and diesel oxidation catalyst (DOC), to meet emission regulations. However, as the emission regulations become stricter, the size of the after-treatment systems become larger. This aggravates the price competitiveness of engine systems and causes fuel efficiency to deteriorate due to the increased exhaust pressure. Dual-fuel premixed charge compression ignition (DF-PCCI) combustion, which is one of the advanced combustion technologies, makes it possible to reduce nitrogen oxides (NOx) and particulate matter (PM) during the combustion process, while keeping the combustion phase controllability as a conventional diesel combustion (CDC). However, DF-PCCI combustion produces high amounts of hydrocarbon (HC) and carbon monoxide (CO) emissions due to the bulk quenching phenomenon under low load conditions as a huddle of commercialization.

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.

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.

Wall wetting of injected fuel onto the intake manifold and cylinder wall causes unpredictable transient behavior of air-fuel mixing which results in a significant emission of unburned hydrocarbon (HC) emission during cold start operation. Heated exhaust gas oxygen (HEGO) sensors cannot measure the air-fuel ratio (A/F) of exhaust gas during cold start condition. Precise and fast estimation of air/fuel ratio of the exhaust gas is required to elucidate the wall wetting phenomena and subsequent HC formation. Refined A/F estimation can enable the control of fuel injection minimizing HC emissions during cold start conditions so that HC emissions can be minimized. A new estimator for A/F of the exhaust gas has been developed. The A/F estimator described in this study utilizes measured exhaust gas temperature and general engine parameters such as engine speed, airflow, coolant temperature, etc.

Combustion and flame propagation characteristics of the liquid phase LPG injection (LPLI) engine were investigated in a single cylinder optical engine. Lean burn operation is needed to reduce thermal stress of exhaust manifold and engine knock in a heavy duty LPG engine. An LPLI system has advantages on lean operation. Optimized engine design parameters such as swirl, injection timing and piston geometry can improve lean burn performance with LPLI system. In this study, the effects of piston geometry along with injection timing and swirl ratio on flame propagation characteristics were investigated. A series of bottom-view flame images were taken from direct visualization using a UV intensified high-speed CCD camera. Concepts of flame area speed, in addition to flame propagation patterns and thermodynamic heat release analysis, was introduced to analyze the flame propagation characteristics.