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The use of hydrogen as a possible fuel for internal combustion (IC) engines can help build a society with a clean transportation framework. Diluting the in-cylinder mixture can improve the efficiency of the engines. To prove the validity of lean burn in hydrogen IC engines, three different combustion modes are investigated in this study. The engine experiments are conducted in a spray-guided direct-injection (DI) spark-ignition engine with 10 MPa of hydrogen DI. When lean burn is applied to a hydrogen IC engine, the characteristics of pumping and heat transfer loss improve. The improvement in heat transfer loss is more significant than the reduction in negative pumping work for the indicated thermal efficiency. Among the three combustion modes, stratified charge combustion (SCC) develops the maximum indicated mean effective pressure. However, this mode deteriorates the combustion stability slightly. The nitrogen oxide emission is reduced when the excess air ratio is increased.

The combustion and exhaust emission characteristics of a DME fueled HCCI engine were investigated. Different fuel injection strategies were tested under various injection quantities and timings with exhaust gas recirculation (EGR). The combustion phase in HCCI was changed by an in-cylinder direct injection and EGR, due to changes in the in-cylinder temperature and mixture homogeneity. The gross indicated mean effective pressure (IMEPgross) increased and the hydrocarbon (HC) and carbon monoxide (CO) emissions decreased as the equivalence ratio was augmented. The IMEPgross with direct injection was greater than with the port injection due to retarded ignition timing resulting from latent heat of direct injected DME fuel. It was because that most of burn duration was completed before top dead center owing to higher ignitability for DME with high cetane number. However, HC and CO emissions were similar for both injection locations.

Dimethyl-ether combustion with pilot injection was investigated in a single cylinder direct injection diesel engine equipped with a common-rail injection system. Combustion characteristics and emissions were tested with dimethyl-ether and compared with diesel fuel. The main injection timing was fixed to have the best timings for maximum power output. The total injected fuel mass corresponded to a low heating value of 405 joules per cycle at 800 rpm. The fuel quantity and the injection timing of the pilot injection were varied from 8 to 20% of the total injected mass and from 50 to 10 crank angle degrees before the main injection timing, respectively. Ignition delay decreased with pilot injection. The effects of pilot injection were less significant with DME combustion than with diesel. Pilot injection caused the main combustion to increase in intensity resulting in decreased emissions of hydrocarbons, carbon monoxide and particulate matter.

The spray characteristics of a swirl injector for direct-injection spark-ignition (DISI) engines were investigated for the generation of robust and well-atomized swirl spray. A highly-inclined tapered nozzle is applied as a test nozzle and the spray characteristics are compared with conventional nozzle and L-step nozzle. When the taper angle is 70°, an opened hollow cone spray is formed. This spray does not collapse with increasing fuel temperature and back pressure conditions. However, the taper angle should be optimized to avoid forming a locally rich area and to increase the spray volume. The droplet size of 70° tapered nozzle spray shows a value similar to that of the original swirl spray in the horizontal mainstream while it shows an increased value in the vertical mainstream. The deteriorated atomization characteristics of the tapered nozzle spray are improved by applying high fuel temperature injection without causing spray collapse.

Low temperature diesel combustion with a large amount of exhaust gas recirculation in a direct injection diesel engine was investigated. Tests were carried out under various engine speeds, injection pressures, injection timings, and injection quantities. Exhaust emissions and brake specific fuel consumption were measured at different torque and engine speed conditions. High rates of exhaust gas recirculation led to the simultaneous reduction of nitrogen oxide and soot emissions due to a lower combustion temperature than conventional diesel combustion. However, hydrocarbon and carbon monoxide emissions increased as the combustion temperature decreased because of incomplete combustion and the lack of an oxidation reaction. To overcome the operating range limits of low temperature diesel combustion, increased intake pressure with a modified turbocharger was employed.

The effect of the composition of propane (C₃H₈) and butane (C₄H₁₀) in liquefied petroleum gas (LPG) was investigated in a dual-fuel HCCI engine fueled with di-methyl ether (DME) and LPG. The composition of LPG affects DME-LPG dual fuel HCCI combustion due to the difference in the physical properties of propane that and butane such as octane number, auto-ignition temperature and heat of vaporization. DME was injected directly into the cylinder at various injection timing from 160 to 350 crank angle degrees (CAD). LPG was injected at the intake port with a fixed injection timing at 20 CAD. It was found that power output was increased with propane ratio. This gain in power output resulted from increased expansion work due to the better anti-knock properties of propane. However, higher propane ratio made combustion efficiency decrease because of the suppression in low temperature reaction of DME which determines heat release amount of high temperature reaction.

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.

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.

To meet stringent emission standards, a considerable amount of development work is necessary to ensure suitable efficiency and durability of catalyst systems. The main challenge is to reduce the engine cold-start emissions. Close-coupled catalyst (CCC) provides fast light-off time by utilizing the energy in the exhaust gas. However, if some malfunction occurred during engine operation and the catalyst temperature exceeds 1050°C, the catalytic converter becomes deactivated and shows poor conversion efficiency. Close-coupled catalyst temperature was investigated under various engine operating conditions. All of the experiments were conducted with a 1.0L SI engine at 1500-4000 rpm. The engine was operated at no load to full load conditions. Exhaust gas temperature and catalyst temperature were measured as a function of lambda value (0.8-1.2), ignition timing (BTDC 30°-ATDC 30°) and misfire rates (0-28%).

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.

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.

The effect of pilot injection and exhaust gas recirculation (EGR) on premixed charge compression ignition (PCCI) combustion was investigated in a single-cylinder direct-injection diesel engine with low engine speed and low load. The injection timing of PCCI combustion was fixed at 25 ~ 30 crank angle degree before top dead center (°CA BTDC) based on the ignition delay and power output. The level of oxides of nitrogen (NOx) emissions of PCCI combustion was 68% lower than that of conventional diesel combustion owing to the reduction of near-stoichiometric region which is well known as the main source of NOx formation. However, the indicated mean effective pressure (IMEP), hydrocarbon (HC), particulate matter (PM) and carbon monoxide (CO) emissions deteriorated compared with conventional diesel combustion because of early injection, advanced combustion phase and lowered combustion temperature. EGR has been applied to PCCI combustion.

A prototype of a small, spark-ignition free-piston engine combined with a linear alternator was designed to produce electric power for portable usage. It has a bore size of 25 mm and maximum stroke of 22 mm. The engine was fueled with liquefied petroleum gas consisting of 98% propane. The electric power generated by the linear alternator is a function of the piston dynamics and the electric conductance. Therefore, the purpose of current research is to investigate the effects of the basic engine controlling parameters such as the equivalence ratio of the mixture and the spark timing on the piston dynamics and study the relationship with the electric power generation performance. The equivalence ratio of the mixture was varied from 1.0 to 1.72, while the spark timing was varied at 3, 4, and 5 mm away from the maximum top dead center. Operating characteristics, namely, indicated mean effective pressure, electric power output, operating frequency and piston stroke were analyzed.

The More precise control of the multiple-injection is required in common-rail injection system of direct injection diesel engine to meet the low NOx emission and optimal PM filter system. The main parameter for obtaining the multiple-injections is the mechanism controlling the injector needle energizing and movement. In this study, a piezo-driven diesel injector, as a new method driven by piezoelectric energy, has been applied with a purpose to develop the analysis model of the piezo actuator to predict the dynamics characteristics of the hydraulic component (injector) by using the AMESim code and to evaluate the effect of this control capability on spray formation processes. Aimed at simulating the hydraulic behavior of the piezo-driven injector, the circuit model has been developed and verified by comparison with the experimental results.

In this study, single and double post injections were applied to diesel premixed charge compression ignition (PCCI) combustion to overcome the drawbacks those are high level of hydrocarbons (HC) and carbon monoxide (CO) emissions in a single-cylinder direct-injection diesel engine. The operating conditions including engine speed and total injection quantity were 1200 rpm and 12 mg/cycle, which are the representative of low engine speed and low load. The main injection timing of diesel PCCI combustion was set to 28 crank angle degree before top dead center (CAD BTDC). This main injection timing showed 32% lower level of nitric oxides (NOx) level and 8 CAD longer ignition delay than those of conventional diesel combustion. However, the levels of HC and CO were 2.7 and 3 times higher than those of conventional diesel combustion due to over-lean mixture and wall wetting of fuel.

One of the major problems limiting the accuracy of piezoelectric transducers for cylinder pressure measurements in an internal-combustion (IC) engine is the thermal shock. Thermal shock is generated from the temperature variation during the cycle. This temperature variation results in contraction and expansion of the diaphragm and consequently changes the force acting on the quartz in the pressure transducer. An empirical equation for compensation of the thermal shock error was derived from consideration of the diaphragm thermal deformation and actual pressure data. The deformation and the resulting pressure difference due to thermal shock are mainly a function of the change in surface temperature and the equation includes two model constants. In order to calibrate these two constants, the pressure inside the cylinder of a diesel engine was measured simultaneously using two types of pressure transducers, in addition to instantaneous wall temperature measurement.

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.

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.

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.