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Technical Paper

04 Emission Reduction by Cylinder Wall Injection in 2-Stroke S.I. Engines

A direct injection system in which fuel was injected through the cylinder wall was developed and detailed investigation was made for the purpose of reducing short-circuit of fuel in 2-stroke engines. As a result of dynamo tests using 430cc single cylinder engine, it was found that the injector was best attached at a location as close to TDC as possible on the rear transfer port side, and that the entire amount of fuel should be injected towards the piston top surface. Emissions were worsened if fuel was injected towards the exhaust port or spark plug. Although the higher injection pressure resulted in large emissions reduction effects, it did not have a significant effect on fuel consumption. When a butterfly exhaust valve, known to be effective against irregular combustion in the light load range, was applied, it was found to lead to further reductions in HC emission and fuel consumption while also improving combustion stability.
Technical Paper

3-D Modeling of Conventional and HCCI Combustion Diesel Engines

An investigation of the possibility to extend the 3-dimensional modeling capabilities from conventional diesel to the HCCI combustion mode simulation was carried out. Experimental data was taken from a single cylinder engine operating with early injections for the HCCI and a split-injection (early pilot+main) for the high speed Diesel engine operation. To properly phase the HCCI mode in the experiments, high amounts of cooled EGR and a decreased compression ratio were used. In numerical simulation performed using KIVA3-V code, modified to incorporate the Detailed Chemistry Approach the same conditions were reproduced. Special attention is paid on the analysis of the events leading up to the auto-ignition, which was reasonably well predicted.
Technical Paper

3D Numerical Simulation of Fuel injection and Combustion Phenomena in DI Diesel Engines

Recently the analysis of air-fuel mixing and combustion has become important under the stringent emissions regulations of diesel engines. In the case of gasoline engines, the KIVA computer program has been developed and used for the analysis of combustion. In this paper, the calculations of combustion phenomena in DI diesel engines are performed by modifying the KIVA program so as to be applicable to multi-hole nozzles and arbitrary patterns of injection rate. The thermophysical and ther-mochemical properties of gasoline are altered to those diesel fuel. In order to investigate the ability of this modified program, the calculations are compared with the experiments on single cylinder engines concerning the pressure, flame temperature and mass change of chemical species in cylinders. Furthermore, the calculation for the heavy duty DI diesel engine is performed with this diesel combustion program.
Technical Paper

A 3D-Simulation with Detailed Chemical Kinetics of Combustion and Quenching in an HCCI Engine

A 3D-CFD model with detailed chemical kinetics was developed to investigate the combustion characteristics of HCCI engines, especially those fueled with hydrogen and n-heptane. The effects of changes in some of the key important variables that included compression ratio and chamber surface temperature on the combustion processes were investigated. Particular attention was given, while using a finer 3-D mesh, to the development of combustion within the chamber crevices between the piston top-land and cylinder wall. It is shown that changes in the combustion chamber wall surface temperature values influence greatly the autoignition timing and location of its first occurrence within the chamber. With high chamber wall temperatures, autoignition takes place first at regions near the cylinder wall while with low surface temperatures; autoignition takes place closer to the central region of the mixture charge.
Journal Article

A Carbon Intensity Analysis of Hydrogen Fuel Cell Pathways

A hydrogen economy is an increasingly popular solution to lower global carbon dioxide emissions. Previous research has been focused on the economic conditions necessary for hydrogen to be cost competitive, which tends to neglect the effectiveness of greenhouse gas mitigation for the very solutions proposed. The holistic carbon footprint assessment of hydrogen production, distribution, and utilization methods, otherwise known as “well-to-wheels” carbon intensity, is critical to ensure the new hydrogen strategies proposed are effective in reducing global carbon emissions. When looking at these total carbon intensities, however, there is no single clear consensus regarding the pathway forward. When comparing the two fundamental technologies of steam methane reforming and electrolysis, there are different scenarios where either technology has a “greener” outcome.
Technical Paper

A Comparative Study of Performance and Emission Characteristics of CNG and Gasoline on a Single Cylinder S. I. Engine

In this study some experiments were carried out to evaluate fuel consumption and exhaust emissions of carbon monoxide (CO), oxides of nitrogen (NOx)) and hydrocarbons (HC) with compressed natural gas (CNG) and gasoline in a single cylinder engine. Compressed natural gas showed 3 to 5 percent higher thermal efficiency and 15 percent lower specific fuel consumption as compared to gasoline. Also CO emissions were lower by 30-80 percent in rich zone and NOx by about 12 percent at an equivalence of 1.0. At wide open throttle CNG operation resulted in 10 to 12 percent lower power output. However, thermal efficiency and brake specific fuel consumption (bsfc) was better with CNG as compared to gasoline. Dual spark plug operation increased power output by 3 to 5 percent.
Technical Paper

A Comparison Between the Combustion of Isooctane, Methanol, and Methane in Pulse Flame Combustors with Closed Loop A/F Control

CO/H2 (ratios i.e. water gas shift equilibria) in exhaust gases produced from the combustion of pure isooctane, methanol, and methane in a pulse flame combustor were measured. Measured CO/H2 ratios were directionally consistent with C/H ratios of the respective fuels. The average CO/H2 ratios in combusted isooctane, methanol, and methane were found to be 3.8, 1.25, and 2.0, respectively. The effect of these differences on feedback A/F control with a HEGO (heated exhaust gas oxygen) sensor were also examined. Feedback control of isooctane combustion produced operation very near to stoichiometry. On the other hand, the combustion of methanol under feedback control resulted in steady state lean operation while feedback control of methane combustion produced rich operation. For all three fuels, operation shifted in the lean direction as combustion efficiency was degraded.
Technical Paper

A Comprehensive Chemical Kinetic Investigation of the Combustion Processes of Lean Mixtures of Methane and Air

The combustion processes of of lean mixtures of methane in air is examined by employing a detailed chemical kinetic scheme consisting of 178 elementary reaction steps with 41 species. The changes with time in the concentrations of the major relevant reactive species are determined from the preignition reactions to the time near equilibrium conditions. The results of such an approach to the combustion process are considered over a wide range of initial temperatures (1000 K - 1600 K) and equivalence ratios (0.2 - 1.2) while the pressure was kept at atmospheric. Calculated results obtained while using this model tend to be in good agreement with the corresponding experimental values of ignition delay. The ignition delay of methane-air mixture correlated by the following empirical expression in which constants A and B are function of the equivalence ratio while Ti is the initial mixture temperature in °K.
Technical Paper

A Computational Investigation of the Effect of Exhaust Gas Recirculation on the Performance of a Dual Fuel Engine

It is well known the dual fuel operation at lower loads suffers from lower thermal efficiency and higher unburned percentages of fuel. The present work includes a computational investigation to predict the effects of Exhaust gas recirculation (EGR) on the operation of an indirect-injection dual fuel (Ricardo-E6) engine by using a detailed chemical kinetic scheme and a quasi-two zone analytical model. The comprehensive chemical kinetic scheme for methane oxidation consisting of 178 elementary reaction steps with 41 species. A quasi-two zone analytical model is based on the effective energy releases of the pilot diesel fuel while using the detailed chemical reaction kinetic scheme for the oxidation of methane. Through the results, it was shown that, the active species such as H, O and OH produced in the high temperature combustion process and found in the exhaust gases are play a significant role in the preignition reactions.
Technical Paper

A Critical Evaluation of the Geared Hypocycloid Mechanism for Internal Combustion Engine Application

The geared hypocycloid mechanism, a kinematic arrangement that provides a straight-line motion, can be used as the basis for an internal combustion engine. Such an engine would have a number of advantages: Perfect balance can be achieved with any number of cylinders. The straight-line motion eliminates the need for a wrist pin bearing, further allowing a very short piston to be used without danger of cocking. Piston side load is virtually eliminated, and “piston slap” will not occur even with a large piston/cylinder clearance. These features make it particularly attractive for small single cylinder engine applications where vibration is undesirable, and also for the uncooled “adiabatic engines”, in which piston cylinder lubrication and friction are major concerns.
Technical Paper


A comprehensive cycle analysis has been developed for four-stroke spark-ignited engines from which the indicated performance of a single cylinder engine was computed with a reasonable degree of accuracy. The step-wise cycle calculations were made using a digital computer. This analysis took into account mixture composition, dissociation, combustion chamber shape (including spark plug location), flame propagation, heat transfer, piston motion, engine speed, spark advance, manifold pressure and temperature, and exhaust pressure. A correlation between the calculated and experimental performance is reported for one engine at a particular operating point. The calculated pressure-time diagram was in good agreement with the experimental one in many respects. The calculated peak pressure was 10 per cent lower and the thermal efficiency 0.8 per cent higher than the measured values. Thus this calculational procedure represents a significant improvement over constant volume cycle approximations.
Technical Paper

A Detailed Two-Dimensional Numerical Study of Spark Ignition Including Ionization

In this work, the spark-ignition (SI) of a methane/air mixture contained in a constant-volume chamber is investigated by numerical simulations. A cylinder-shaped vessel filled with a methane/air mixture containing two electrodes is used as simulation model. The impact of an electrical discharge at the electrodes on the surrounding gas is simulated, with detailed treatment of the ignition process involvig chemical kinetics, transport phenomena in the gas-phase and electrodynamical modeling of the interaction between spark and fuel/air mixture. For the calculations, a 2D-code to simulate the early stages of flame development, shortly after the breakdown discharge, has been developed. Computational results are shown for ignition of a methane air-mixture.
Technical Paper

A Developing Process of Newly Developed Electromagnetic Valve Actuator - Effect of Design and Operating Parameters

Electromagnetic valve (EMV) actuation system is a new technology for the improvement of fuel efficiency and the reduction of emissions in SI engines. It can provide more flexibility in valve event control compared to conventional variable valve actuation devices. However, a more powerful and efficient actuator design is needed for this technology to be applied in mass production engines. This paper presents the effects of design and operating parameters on the thermal, static and dynamic performances of the actuator. The finite element method (FEM) and computer simulation models are used in predicting the solenoid forces, dynamic characteristics and thermal characteristics of the actuator. Effect of design parameters and operating environment on the actuator performance were verified before making prototypes using the analytical models. To verify the accuracy of the simulation model, experimental study is also carried out on a prototype actuator.
Technical Paper

A Gas Chromatograph-Based System for Measuring the Methane Fraction of Diesel Engine Hydrocarbon Emissions

Investigations have concluded that methane does not appear to be photochemically reactive in the atmospheric system and does not participate in smog formation. Since methane is “nonreactive,” and may in the future be excluded from the total unburned hydrocarbon emissions, an instrument was designed and developed (termed the “methane analytical system”) enabling methane emissions to be quantified separately from total unburned hydrocarbon emissions. The instrument employed gas chromatographic principles whereby a molecular sieve column operating isothermally separated methane from the nonmethane hydrocarbons. Direct on-line sampling occurred via constant volume sample loops. The effluent was monitored with a flame ionization detector. The instrument was fully calibrated (i.e., extremely linear response over a large concentration range) for use with Diesel engines as part of an ongoing alternative fuels research program.
Technical Paper

A High Speed Flow Visualization Study of Fuel Spray Pattern Effect on Mixture Formation in a Low Pressure Direct Injection Gasoline Engine

In developing a direct injection gasoline engine, the in-cylinder fuel air mixing is key to good performance and emissions. High speed visualization in an optically accessible single cylinder engine for direct injection gasoline engine applications is an effective tool to reveal the fuel spray pattern effect on mixture formation The fuel injectors in this study employ the unique multi-hole turbulence nozzles in a PFI-like (Port Fuel Injection) fuel system architecture specifically developed as a Low Pressure Direct Injection (LPDI) fuel injection system. In this study, three injector sprays with a narrow 40° spray angle, a 60°spray angle with 5°offset angle, and a wide 80° spray angle with 10° offset angle were evaluated. Image processing algorithms were developed to analyze the nature of in-cylinder fuel-air mixing and the extent of fuel spray impingement on the cylinder wall.
Technical Paper

A Lambda Sensor Using Intake Mixture of Natural-Gas-Fueled Engines: The Censor

A special combustion chamber is described which burns a small, representative, fraction of the intake mixture of natural-gas-fuelled spark-ignition engines. The combustion end products are led to a lambda sensor which, consequently, will not be deteriorated by lubricating-oil additives and will not be hampered in its operation by unburnt methane. That leads to a largely extended life of the lambda sensor. The paper discusses the construction and control of the special chamber and ends with a discussion on the representativeness of the measured oxygen concentration for the air-to-fuel ratio.
Technical Paper

A Micrographic Study of Deposit Formation Processes in a Combustion Chamber

Growing concern about the impact of combustion chamber deposits (CCD) on engine performance and exhaust emissions has renewed interest in understanding the deposit formation process in a combustion chamber. To provide a true picture of the deposit formation process, an extensive micrographic study of the deposits in a single cylinder engine has been conducted. Four retrievable deposit sampling probes were used. The sampling period for the deposits varied from 15 minutes to 20 hours to show how the deposits evolved with time. The coolant temperature was changed from 50°C to 95°C to observe the effect of surface temperature on deposit morphology. Impacts of deposit control additives on the deposit distribution and deposit morphology were also investigated. Deposits formed in different parts of the combustion chamber differed significantly in their morphology. The differences occur mainly because of variations in surface temperature.
Technical Paper

A Mixing Timescale Model for PDF Simulations of LTC Combustion Process in Internal Combustion Engines

Transported probability density function (PDF) methods are currently being pursued as a viable approach to model the effects of turbulent mixing and mixture stratification, especially for new alternative combustion modes as for example Homogeneous Charge Compression ignition (HCCI) which is one of the advanced low temperature combustion (LTC) concepts. Recently, they have been applied to simple engine configurations to demonstrate the importance of accurate accounting for turbulence/chemistry interactions. PDF methods can explicitly account for the turbulent fluctuations in species composition and temperature relative to mean value. The choice of the mixing model is an important aspect of PDF approach. Different mixing models can be found in the literature, the most popular is the IEM model (Interaction by Exchange with the Mean). This model is very similar to the LMSE model (Linear Mean Square Estimation).
Journal Article

A Multi-Dimensional CFD-Chemical Kinetics Approach in Detection and Reduction of Knocking Combustion in Diesel-Natural Gas Dual-Fuel Engines Using Local Heat Release Analysis

Dual-fuel diesel-natural gas (NG) engine exhibits higher power density and lower specific emissions compared to dedicated diesel engines. However, high intake temperatures, high compression ratios, combined with high engine loads may lead to engine knock. This is potentially a limiting factor on engine downsizing and getting higher power. In the present study, the combustion process under knocking conditions has been investigated in a dual-fuel diesel-NG engine. A comprehensive multi-dimensional simulation framework was generated by integrating the CHEMKIN chemistry solver into the KIVA-3V code. A detailed chemical kinetics mechanism was used for n-heptane and methane as diesel and NG surrogates. Combination of detailed chemical kinetics and detailed fluid dynamics calculation enabled the model to take into account the characteristics of most pronounced knock type in dual-fuel engines, so called end-gas knock.
Technical Paper

A New Approach to Ethanol Utilization: High Efficiency and Low NOx in an Engine Operating on Simulated Reformed Ethanol

The use of hydrogen as a fuel supplement for lean-burn engines at higher compression ratios has been studied extensively in recent years, with good promise of performance and efficiency gains. With the advances in reformer technology, the use of a gaseous fuel stock, comprising of substantially higher fractions of hydrogen and other flammable reformate species, could provide additional improvements. This paper presents the performance and emission characteristics of a gas mixture of equal volumes of hydrogen, CO, and methane. It has recently been reported that this gas mixture can be produced by reforming of ethanol at comparatively low temperature, around 300C. Experiments were performed on a 1.8-liter passenger-car Nissan engine modified for single-cylinder operation. Special pistons were made so that compression ratios ranging from CR= 9.5 to 17 could be used. The lean limit was extended beyond twice stoichiometric (up to lambda=2.2).