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The Lambert-Beer's coefficient K was measured in a wide range of temperatures (400-1200K) and pressures (2-8.2 MPa) in this paper. Based on the measured MAP of K and principle of energy conservation in the sprays mass and transfer, a quantitative presentation of equivalence ratio and temperature in vapor phase sprays at diesel engine like conditions was put forward. The experimental range of temperatures was 800-1100K and 20-100 kg/m₃ for density. It was found that the maximum equivalence ratio of vapor phase spray remained fairly constant at about 3.0 and the maximum equivalence ratio appearance earlier as the ambient density increased, while the ambient temperature in the constant volume vessel was set at 800K. The maximum equivalence ratio of vapor phase spray increased from about 3.0 to about 3.7 as ambient temperature increased from 800 to 1100K.

Reactivity Controlled Compression Ignition (RCCI) has been shown to be an attractive concept to achieve clean and high efficiency combustion. RCCI can be realized by applying two fuels with different reactivities, e.g., diesel and gasoline. This motivates the idea of using a single low reactivity fuel and direct injection (DI) of the same fuel blended with a small amount of cetane improver to achieve RCCI combustion. In the current study, numerical investigation was conducted to simulate RCCI and HCCI combustion and emissions with various fuels, including gasoline/diesel, iso-butanol/diesel and iso-butanol/iso-butanol+di-tert-butyl peroxide (DTBP) cetane improver. A reduced Primary Reference Fuel (PRF)-iso-butanol-DTBP mechanism was formulated and coupled with the KIVA computational fluid dynamic (CFD) code to predict the combustion and emissions of these fuels under different operating conditions in a heavy duty diesel engine.

A versatile liquid dosing device along with its metering theory, which can be applied to both SCR dosing system and DPF regeneration system of IC engine after-treatment system, is presented in this paper. The device is composed of a solenoid driven plunger pump, a nozzle and a pressure tube, and is pump-end controlled by PWM signals. Both electrically resistive and conductive liquids including DEF for SCR system, fuel for DPF regeneration, and gasoline for spark ignition engine, can be dispensed quantitatively with this device. A metering theory determining the liquid discharged per injection is developed by studying the system using a physical-mathematical model. The study shows that the liquid discharge can be well correlated with a measurable variable T3, which is associated with the net output energy. Experimental investigations verified that the metering results were independent of the state changes.

The dual-fuel Reactivity Controlled Compression Ignition (RCCI) combustion could achieve high efficiency and low emissions over a wide range of operating conditions. However, further high load extension is limited by the excessive pressure rise rate and soot emission. Polyoxymethylene dimethyl ethers (PODE), a novel diesel alternative fuel, has the capability to achieve stoichiometric smoke-free RCCI combustion due to its high oxygen content and unique molecule structure. In this study, experimental investigations on high load extension of gasoline/PODE RCCI operation were conducted using late intake valve closing (LIVC) strategy and intake boosting in a single-cylinder, heavy-duty diesel engine. The experimental results show that the upper load can be effectively extended through boosting and LIVC with gasoline/PODE stoichiometric operation.

Combustion processes employing different injection strategies in a High-Speed Direct Inject (HSDI) diesel engine were investigated using a narrow angle injector (70 degree). Whole-cycle combustion was visualized using a high-speed digital video camera. The liquid spray evolution process was imaged by the Mie-scattering technique. Different injection strategies were employed in this study including early pre-Top Dead Center (TDC) injection, post-TDC injection, multiple injection strategies with an early pre-TDC injection and a late post-TDC injection. Smokeless combustion was obtained under some operating conditions. Compared with the original injection angle (150 degree), some new combustion phenomena were observed for certain injection strategies. For early pre-TDC injection strategies, liquid fuel impingement is observed that results in some newly observed fuel film combustion flame (pool fires) following an HCCI-like weak flame.

Biodiesel fuel can be produced from a wide range of source materials that affect the properties of the fuel. The diesel engine has become a highly tuned power source that is sensitive to these properties. The objectives of this research were to measure and predict the key properties of biodiesel produced from a broad range of source materials to be used as inputs for combustion modeling; and second to compare the results of the model with and without the biodiesel fuel definition. Substantial differences in viscosity, surface tension, density and thermal conductivity were obtained relative to reference diesel fuels and among the different source materials. The combustion model revealed differences in the temperature and emissions of biodiesel when compared to reference diesel fuel.

An optically accessible single-cylinder high-speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail injection system was used to study the spray and combustion processes for European low sulfur diesel, bio-diesel, and their blends at different blending ratio. Influences of injection timing and fuel type on liquid fuel evolution and combustion characteristics were investigated under similar loads. The in-cylinder pressure was measured and the heat release rate was calculated. High-speed Mie-scattering technique was employed to visualize the liquid distribution and evolution. High-speed combustion video was also captured for all the studied cases using the same frame rate. NOx emissions were measured in the exhaust pipe. The experimental results indicated that for all of the conditions the heat release rate was dominated by a premixed combustion pattern and the heat release rate peak became smaller with injection timing retardation for all test fuels.

Biodiesel fuels and their blends with diesel are often used to reduce emissions from diesel engines. However, biodiesel has been shown to increase the NOx emissions. Operating a compression ignition engine in low-temperature combustion mode as well as using multiple injections can reduce NOx emissions. Experimental data for biodiesel are compared to those for diesel to show the effect of the biodiesel on the peak pressure, temperature, and emissions. Accurate prediction of biodiesel properties, combined with the KIVA 3V code, is used to investigate the combustion of biodiesel. The volume fraction of the cylinder that has temperatures greater than 2200 K is shown to directly affect the production of oxides of nitrogen. Biodiesel is shown to burn faster during the combustion events, though the ignition delay is often longer for biodiesel compared to diesel.

A numerical study of micro-explosion in multi-component droplets is presented. The homogeneous nucleation theory is used in describing the bubble generation process. A modified Rayleigh equation is then used to calculate the bubble growth rate. The breakup criterion is then determined by applying a linear stability analysis on the bubble-droplet system. After the explosion/breakup, the atomization characteristics, including Sauter mean radius and averaged velocity of the secondary droplets, are calculated from conservation equations. Micro-explosion can be enhanced by introducing biodiesel into the fuel blends of ethanol and tetradecane. Micro-explosion is more likely to occur at high ambient pressure. However, increasing the ambient temperature does not have a significant effect on micro-explosion. There exists an optimal composition in the liquid mixture for micro-explosion.

In-cylinder flow characteristics in a four-stroke diesel engine were studied experimentally by instantaneous measurements of swirl and squish flow velocity distribution with particle image velocimetry (PIV). The triple-exposed PIV films were interrogated on a self-made system to get the velocity distribution. The measured velocities were analyzed by spatially high-pass and low-pass filtering techniques. Vorticity distributions were also calculated using the measured data. As results, vortex structure of the flow field was clearly visualized. Spatially averaged in-cylinder flow energy was found decaying at high rate but the less-scaled flow components at much lower rate. Clearly visualized squish and reverse squish movements around the top dead center (TDC) during the compression stroke were found strongly affecting the swirl flow field. making the in-bowl flow energy increased.

The operation of a small bore high speed direct injection (HSDI) engine with a MVCO injector is simulated by the KIVA 3V code, developed by Los Alamos National Laboratory. The MVCO injector extends the range of injection timings over conventional injectors and it extra flexibility in designing injection schemes. Combustion from very early injection is observed with MVCO injections but not with conventional injection. This improves the fuel economy of the engine in terms of lower ISFC. Even better efficiency can be achieved by using biodiesel, which may be due to extra oxygen in the fuel improving the combustion process. Biodiesel sees a longer ignition delay for the initial injection. It also exhibits a faster burning rate and shorter combustion duration. Biodiesel also lowered both NOx and soot emissions. This is consistent with the general observation for soot emissions.

The KIVA-3V code, developed by Los Alamos National Laboratory, with modifications that improve its capability with biodiesel simulations was used to model the operation of an HSDI engine using blends of soybean biodiesel and diesel. Biodiesel and their blends with diesel are frequently used to reduce emissions from diesel engines, although previous studies showed that biodiesel may increase NOx emission. The paradox may be resolved by running the engine in low temperature combustion mode with biodiesel/diesel blends, as low temperature combustion simultaneously reduced NOx and soot. The modified KIVA code predicts the major combustion characteristics: peak combustion pressure, heat release rate and ignition timing accurately when compared with experimental measurements. It also correctly predicts the trend of NOx emissions. It was observed that the cylinder temperature distribution has a strong effect on emission levels.

Exhaust Gas Recirculation (EGR) is an important parameter for control of diesel engine combustion, especially to achieve ultra low NOx emissions. In this paper, the effects of EGR on engine emissions and engine efficiency have been investigated in a heavy-duty diesel engine while changing combustion control parameters, such as injection pressure, injection timing, boost, compression ratio, oxygenated fuel, etc. The engine was operated at 1400 rpm for a cycle fuel rate of 50mg. The results show that NOx emissions strongly depend on the EGR rate. The effects of conventional combustion parameters, such as injection pressure, injection timing, and boost, on NOx emissions become small as the EGR rate is increased. Soot emissions depend strongly on the ignition delay and EGR rate (oxygen concentration). Soot emissions can be reduced by decreasing the compression ratio, increasing the injection pressure, or burning oxygenated fuel.

Engine experiments and CFD modeling studies have been carried out and shown that high density-low temperature combustion (H Density-LTC) has the potential of realizing high thermal efficiency and very low engine-out emissions at high and full engine loads. Parametric studies were conducted to explore the mechanism of formation of pollutants in high charge density in this paper. It was found that high charge density was normally favorable to spray atomization, evaporation and fuel/air mixing throughout the entire combustion process, but there was a turning value of charge density above which the improvement of thermal efficiency was reduced. The conversion of CO to CO₂ was accelerated and CO emission was decreased with increasing charge density, which was also proved to be beneficial to re-oxidation of soot formed. The oxygen concentration brings a conflict effect to NOx emissions and exhaust soot. The high density combustion relieved the conflict effect of oxygen concentration.

Natural gas is regarded as one of the most potential alternative fuels of engines because of its fruitful storage, good obtainable resources, and high octane value, etc. Compared with port fuel injection (PFI), Gasoline direct injection (GDI) has many advantages on volumetric efficiency improvement, lean-burning, emissions control, etc. A set of measuring and data acquisition system on CNG direct injection spark-ignited engines and the CNG multi-direct injection system are developed in this paper. Based on different injection modes of CNG single DI and compound DI (main injection and auxiliary-Injection), the investigations on combustion process of CNG DI engines has been conducted by the factors of in-cylinder mixture formation, air/fuel ratio, and injection timing, etc. Meanwhile, the three-dimension simulation on mixture formation and combustion principle of low-pressure CNG compound direct injection engines has also been researched.

The use of substances other than petroleum based fuels for power sources is not a new concept. Prior to the advent of petroleum fueled vehicles numerous other substances were used to create mobile sources of power. As the world's petroleum supply dwindles, alternative fuel sources are sought after to replace petroleum fuels. Many industries are particularly interested in the development of renewable fuel sources, or biologically derived fuel sources, which includes ethanol. The use of No. 2 diesel as well as many alternative fuels in compression ignition engines result in injector coking. Injector coking can severely limit engine performance by limiting the amount of fuel delivered to the combustion chamber and altering the spray pattern. Injector tip coking is also one of the most sensitive measures of diesel fuel quality [1]. A machine vision system was implemented to quantify injector coking accumulation when a compression ignition engine was fueled with oxydiesel.

The detailed mechanisms by which oxygenated diesel fuels reduce engine-out soot emissions are not well understood. The literature contains conflicting results as to whether a fuel's overall oxygen content is the only important parameter in determining its soot-reduction potential, or if oxygenate molecular structure or other variables also play significant roles. To begin to resolve this controversy, experiments were conducted at a 1200-rpm, moderate-load operating condition using a modern-technology, 4-stroke, heavy-duty DI diesel engine with optical access. Images of broadband natural luminosity (i.e., light emission without spectral filtering) from the combustion chamber, coupled with heat-release and efficiency analyses, are presented for three test-fuels. One test-fuel (denoted GE80) was oxygenated with tri-propylene glycol methyl ether; the second (denoted BM88) was oxygenated with di-butyl maleate. The overall oxygen contents of these two fuels were matched at 26% by weight.

The ability to categorize, compare and segregate the roll dynamical behavior of various vehicles from one another is a subject of considerable research interest. A number of comparison paradigms have been developed (static stability index, roll couple methods, etc.), but all suffer from lack of robustness: results developed on the basis of a particular comparison metric are often not able to be generalized across vehicle lines and types, etc., or they simply do not segregate vehicles at all. In addition, most models do not describe vehicle dynamics in sufficient detail, and some contain no dynamics at all (e.g., static stability index = t/2h). In the present work, static stability index, a two-degree-of-freedom roll model and a three-degree-of-freedom roll and handling model were used to locate eigenvalues for a sample of 43 vehicles consisting of (1) passenger cars, (2) light trucks, (3) sport/utility vehicles and (4) minivans.

In this work, an efficient and unified combustion model is introduced to simulate the flame propagation, diffusion-controlled combustion, and chemically-driven ignition in both SI and CI engine operation. The unified model is constructed upon a G-equation model which addresses the premixed flame propagation. The concept of the Livengood-Wu integral is used with tabulated ignition delay data to account for the chemical kinetics which is responsible for the spontaneous ignition of fuel-air mixture. A set of rigorously defined operations are used to couple the evolution of the G scalar field and the Livengood-Wu integral. The diffusion-controlled combustion is simulated equivalent to applying the Burke-Schumann limit. The combined model is tested in the simulation of the premixed SI combustion in a constant volume chamber, as well as the CI combustion in a conventional small bore diesel engine.

A numerical simulation was performed to investigate the pilot ignited natural gas combustion process in a direct injection natural gas engine. Various mixture distribution characteristics were compared in terms of the evolution of mixture equivalent ratio distributions and mixture concentration stratifications around top dead center (TDC). Based on above, the pilot injections were specially designed to investigate ignition core formation and its effects on natural gas combustion process. The result shows that pilot ignition sites have great impacts on pilot fuel ignition process and natural gas combustion process. The pilot ignition site on the region with rich NG/Air mixture is disadvantageous to the pilot fuel ignition due to a lack of oxygen, which is not beneficial to ignition core formation.