In this study, effects on a spark ignition engine of pure compressed natural gas (CNG) and mixtures of CNG and Hydrogen (Hythane) have been experimentally considered. In this study, three types of fuel including pure CNG, Hythane with 15% hydrogen and hythane with 30% hydrogen in volume are used. Tests were performed in both of full load and part load conditions. Full load tests contain engine speeds from1500 rpm up to 60000 rpm with step of 500 rpm. Part load tests were performed in engine speed of 2000 rpm and 3000 rpm. In each test, spark timing was set to reach the maximum indicated mean effective pressure. The results showed that volumetric efficiency, power and torque decreased with increase of Hydrogen fraction at full loads but thermal efficiency increased. increase of Hydrogen fraction in Hythane mixture cause Co and HC decrease but NOx increases.

Fuel metering system and controlling fuel-air mixture of spark ignition engines have been the major goals for the researcher. Management in mixture quality and fuel economy have resulted in changing carburetor systems to injection systems. Start of fuel injection position and injection duration play important role in engine performance. In the current work a single cylinder research engine with capability of adjusting spark timing and controlling gasoline injection start position and duration was utilized. Compression ratio, engine speed and injection start position were adjusted to 8, 1800 rpm and breathing top dead center (BTDC), respectively. Injection duration and spark timing were controlled so that to achieve maximum output torque at equivalence ratio of 0.90. Fixing them, the start of injection was only changed in the range of -180 to 180°CA relative to BTDC with a 30°CA increment. For each case, cylinder pressure of 500 successive cycles were recorded and stored. The obtained results showed that the dispersion of indicated mean effective pressure (IMEP) data of the cases with injection position start after BTDC were higher than those of the cases with injection position start before BTDC. Also, the average values of IMEP and peak pressure and their coefficient of variation changed with varying fuelinjection start position; and for the cases of high dispersion in IMEP data, the average values of IMEP and isfc appeared to be high and low respectively.

Nowadays, the homogenous charge compression ignition (HCCI) engine is a new idea to satisfy two main strategies in the design of internal combustion engines: reducing the fuel consumption and emissions. The robust control of combustion phasing in HCCI engines is a main challenge limiting the automotive industry for the mass production. In controlling combustion phasing and the IMEP (as two main controlling parameters) in the HCCI engine, some parameters are more effective than others. Effects of these parameters such as the inlet temperature and pressure, the equivalence ratio, the engine speed and also PRFs on the start of the ignition and the IMEP have been investigated in this study using a thermo-kinetic zero-dimensional model. This model coupled to a full kinetic mechanism of PRFs. The model was validated with a large number of experimental data taken from the Ricardo engine. Results show that the start of the combustion depends on the inlet temperature, the octane number, the engine speed and the equivalent ratio. On the other hand, the IMEP depends on the fuel mass flow rate, the inlet temperature and the equivalent ratio. As a result, a correlation has been presented to predict the start of the combustion and the IMEP; and its accuracy has been checked with some experimental data.

In the development of Homogeneous Charge Compression Ignition (HCCI) engines, simultaneous control of combustion phasing and power output has been a major challenge. In this study, a new strategy is developed to control the engine power output and combustion phasing at any desired operating condition. A single zone thermodynamic model coupled to a full kinetic mechanism of Primary Reference Fuels (PRFs) is developed to predict characteristic parameters such as; Start of Combustion (SOC) and Indicated Mean Effective Pressure (IMEP) and also thermodynamic constant parameters for processes through an HCCI engine cycle. A dynamic interactive control model has been developed for the entire cycle of a HCCI engine to predict combustion phasing and IMEP. The results derived from the developed model are validated against experimental data for a single cylinder Ricardo engine. A two input - two output controller is then designed to track crank angle at which 50% of in cylinder fuel mass is burned (CA50) and IMEP by adjusting the input data. In this study two control models are presented; open loop and closed loop. Performance of the controller is tested on a physical HCCI engine model to evaluate the tracking performance and disturbance rejection properties. Results indicate that the designed controller is capable to accurately tracking both CA50 and IMEP while rejecting the disturbances from variations in the engine speed and the intake manifold temperature.

Reorganizations of cyclic variations, depending on fuel type, equivalence ratio, engine load and speed, and engine geometry, are the major purposes and may cause fluctuations of output power and unburned hydro-carbon. During this study, the effects of gasoline and natural gas (NG) as fuel on cyclic variations were investigated utilizing the recorded cylinder pressure of a research SI engine over more than 400 successive cycles. This work was performed at full load, 1800rpm and compression ratio of 8 with 0.94 equivalence ratio using gasoline-air and NG-air mixtures. Statistical analysis of the obtained results showed that at the above conditions the coefficient of variations (COV) of indicated mean effective pressure (IMEP), peak pressure (Pmax) and the crank angle position of the peak pressure (qPmax) for gasoline-air mixture were 2.4, 1.29 and 1.04 times of those for NG-air mixture, respectively; at the optimum ignition timing, IMEP of gasoline-air mixture is increasing with rising Pmax and decreasing with enhancing qpmax, however, IMEP of NG-air mixture seems to be independent to Pmax and q Pmax.

Alcohols have been used as a fuel for engines since 19th century. Among the various alcohols, ethanol and methanol are known as the most suited renewable, bio-based and ecofriendly fuel for spark-ignition (SI) engines. The most attractive properties of ethanol and methanol as an SI engine fuel are that it can be produced from renewable energy sources such as sugar, cane, cassava, many types of waste biomass materials, corn and barley. In addition, ethanol has higher evaporation heat, octane number and flammability temperature therefore it has positive influence on engine performance and reduces exhaust emissions. In this study, the effects of unleaded iso-octane, unleaded iso-octane-ethanol blend (E10) and isooctane-methanol blend (M10) on engine performance were investigated experimentally in a single cylinder four-stroke spark-ignition engine. The tests were performed by varying the throttle position, engine speed and loads. Three sets of observations were recorded at (1301 rpm, 16.8 Kg load), (1468 rpm, 15.8 Kg load) and (1544 rpm, 10 Kg load) for all tested fuels. The results of the engine test showed that IP, IMEP, Volumetric efficiency and thermal efficiency was higher for the E10 fuel and BSFC was lower. In general, most suited blend for SI engines has been specified as a blend of 10% ethanol. It was also observed that better performance was recorded during second set of observation for all the tested fuels. It was also found that ethanol–gasoline blends allow increasing compression ratio (CR) without knock occurrence.

The aim of this study is to evaluate the effect of hydrogen addition on a heavy-duty diesel engine performance and emission under RCCI combustion fueled with natural gas and diesel fuel. For this purpose, a single-cylinder heavy-duty diesel engine is used to operate at lowload range from 5. 6 to 7. 7 bar gross IMEP, constant engine speed, and a fixed amount of diesel fuel. Furthermore, in order to reduce hydrocarbon fuels consumption, hydrogen is gradually added to natural gas while the total fuel energy content is kept to be constant. The results show that by adding hydrogen to natural gas in the RCCI engine at 5. 6, 6. 3, and 7. 7 bar gross IMEP, the hydrogen energy share could be enhanced up to 35. 7%, 23. 70%, and 9. 93%, respectively. And also, the overall hydrocarbon fuels consumption per cycle can be reduced up to 45. 23%, 29. 26%, and 12. 07%, respectively. Although, CO and UHC emissions decrease drastically, NOx increases significantly with the addition of hydrogen compared to RCCI combustion fueled with natural gas and diesel fuel.

In the current research, a CFD simulation has been carried out to investigate the simultaneous effects of injection pressure and Exhaust Gas Recirculation (EGR) on the engine performance and the amount of pollutant emissions in a modern High Speed Direct Injection (HSDI) diesel engine. For this purpose, the computational results have been firstly compared to the measured data and a good agreement has been achieved in regard to predicting the in-cylinder pressure and the amount of NOx and soot emissions. Then, the effects of injection pressure has been studied at the various EGR rates. The results show, in the case of a constant injected fuel and without using the EGR, decreasing the nozzle diameter causes increase of Indicated Mean Effective Pressure (IMEP) and reduction of Indicate Specific Fuel Consumption (ISFC). However, the amount of NOx emission has been largely increased and the amount of soot emissions has been decreased. By applying the different percentage of EGR rates, a potential to decrease the amount of NOx emission have been provided while the engine operating conditions (including the ISFC and IMEP) remain constant. However, the increase of soot emissions should be considered as a negative parameter in this case.

Spark ignition engines are among the common apparatuses for generating power for various applications. By employing dual-fuel spark ignition engines using gasoline and natural gas and analyzing the variations in burned residual gases within the combustion cycles, the operational efficiency of the engine can be improved. Experimental data were obtained from a one-cylinder spark ignition engine operating at different spark advances, a compression ratio of 9, and a fuel mixture of 60% gasoline by mass and 40% natural gas by mass under stoichiometric conditions. Measurements were taken under both skip-fire and no-skip scenarios. The raw recorded data were processed to derive the in-cylinder pressure versus crank angle diagram and to calculate the Indicated Mean Effective Pressure (IMEP). Analysis of the ensemble average cycle derived from experimental runs at optimal spark advances revealed that the rate of pressure changes within the cylinder before reaching peak pressure is higher under skip fire conditions. Additionally, a difference of 5 degrees in crankshaft angle was observed between the optimum spark advance with and without skip fire mode. The standard deviation and coefficient of variation for the IMEP were found to be lower in the skip fire condition, indicating a reduction in cyclic variation with skip fire. Furthermore, the rate of change of the mass fraction burned was higher under skip fire conditions compared to no skip fire mode, suggesting faster combustion in the skip fire condition.