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As a new type of energy, free-piston linear generator (FPLG) attracts more research on its stable operation and power performance, while less on its combustion and emission performance. So, in this paper, the emission characteristics of FPLG in two different modes are studied through a port fuel injection (PFI) mode which was verified by the experiment and a gasoline direct injection (GDI) mode. The results showed that: both the GDI mode and the PFI mode produced large amounts of nitrogen oxide (NOx) during the working process. But the GDI mode produced before the PFI mode and it produced nearly 2 times than the PFI mode. However, the formation rate of NOx in GDI mode is much lower than that in PFI mode. Meanwhile, in both modes, 90% of NOX was generated in the cylinder at the temperature higher than 1750K, and only about 10% of NOX was generated at a temperature lower than 1750K.

The deformation of injector components cannot be disregarded as the pressure of the system increases. Deformation directly affects the characteristics of needle movement and injection quantity. In this study, structural deformation of the nozzle, the needle and the control plunger under different pressures is calculated by a simulation model. The value of the deformation of injector components is calculated and the maximum deformation location is also determined. Furthermore, the calculated results indicates that the deformation of the control plunger increases the control chamber volume and the cross-section area between the needle and the needle seat. A MATLAB model is established to The influence of structural deformation on needle movement characteristics and injection quantity is investigate by a numerical model. The results show that the characteristic points of needle movement are delayed and injection quantity increases due to the deformation.

With the development of advanced ABE fermentation technology, the volumetric percentage of acetone, butanol and ethanol in the bio-solvents can be precisely controlled. To seek for an optimized volumetric ratio for ABE-diesel blends, the previous work in our team has experimentally investigated and analyzed the combustion features of ABE-diesel blends with different volumetric ratio (A: B: E: 6:3:1; 3:6:1; 0:10:0, vol. %) in a constant volume chamber. It was found that an increased amount of acetone would lead to a significant advancement of combustion phasing whereas butanol would compensate the advancing effect. Both spray dynamic and chemistry reaction dynamic are of great importance in explaining the unique combustion characteristic of ABE-diesel blend. In this study, a semi-detailed chemical mechanism is constructed and used to model ABE-diesel spray combustion in a constant volume chamber.

An opposed piston two-stroke engine is more suitable for use in an unmanned aerial vehicle because of its small size, excellent self-balancing, stable operation, and low noise. Consequently, in this study, based on experimental data for a prototype opposed piston two-stroke engine, numerical simulation models were established using GT-POWER for 1D simulation and AVL-FIRE for 3D CFD simulation. The mesh grid and solver parameters for the numerical model of the CFD simulation were determined to guarantee the accuracy of the numerical simulation, before studying and optimizing the ventilation efficiency of the engine with different dip angles. Furthermore, the fuel spray and combustion were analyzed and optimized in details.

Incomplete-combustion and misfire are the hurdles in internal combustion engines to run on ultra-lean mixture, whereas high thermal efficiency has been achieved at lean mixture. The burning characteristics of n-heptane with 0% and 30% hydrogen additions were studied at 393K-453K and 100kPa-300kPa up to near lean burn limits, λ=0.8-2.0. The flame appeared in spherical shape only by 37-mJ ignition energy (IE) at λ=0.8-1.5, while further lean mixture, ≥1.6, could be ignited only by 3000-mJ with the distorted flame shape. The flame buoyed in the mixture when burning velocity calculated by kinetic mechanism was equal or less than 19.83 cm/s at the initial conditions of λ=1.8, 393K and 100kPa. The thermal instability under impact of initial pressure and temperature was higher at lean mixture than at stoichiometric mixture.

This present paper described an experimental study on the combustion and emission characteristics of a diesel engine at idle at different altitudes. Five altitudes ranging from 550m to up to 4500m were investigated. Combustion parameters including in-cylinder pressure and temperature, heat release, fuel mass burning and so forth, together with emission factors including CO, HC, NOx and PM were tested and analyzed. The result of on-board measurement manifested that in-cylinder pressure descended consistently with the rising of altitude, while both the maximum in-cylinder temperature and exhaust temperature ascended with the altitude. It was found that ignition delay was lengthened at higher altitude, but the combustion duration became shorter. The crank angle towards 90% fuel burnt has hardly changed with the variation of altitude. As for heat release, the difference of slopes observed at different altitudes was quite slight.

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.

One-dimensional combustion performance of a turbocharged V-type eight-cylinder diesel engine was computed by used of WAVE code. The parameters of compress ratio, intake temperature, intake pressure, fuel injection quantity, advance angle of injection, fuel injection rate and fuel injection duration were changed so as to study quantificationally how these parameters affect the power, fuel consume, the max combustion pressure, exhaust temperature and emission of the diesel engine. The computational results could help to accomplish the preliminary optimization of several parameters for combustion matching and supplement experimental experience and exploit new products.

Contact dynamic characteristics of an internal combustion engine structure were studied by the finite element method and experimental verification. Based on theoretical analysis, contact modal calculation of an internal-combustion engine with finite element method is carried out by the ADINA software. Dynamic behavior of the entire engine structure was investigated. Rigid bar connection and coupling connection were introduced for the purpose of comparison with contact analysis and experiment results. The experimental results are in good agreement with the theoretical analysis and FEM results. From the study, it can be demonstrated that dynamic behavior of the engine structure with a large preload shows linear characteristics. Compared with the other models, the procedure presented in this paper is more effective and useful in view of operational time and experience of analysts.

This paper presents the latest results for a new high efficiency clean diesel combustion system – Adaptive PCCI Combustion (a premixed charge compression ignition mixed-mode combustion) using a micro-variable circular orifice (MVCO) fuel injector. Key characteristics of the new combustion system such as low NOx and soot emissions, high fuel efficiency, increased engine torque are presented through KIVA simulation results. While early premixed charge compression ignition (PCCI) combustion reduces engine-out NOx and soot, it's limited to partial loads by known issues such as combustion control, high HC and CO, and high pressure rise rate, etc. Conventional combustion is well controlled diffusion combustion but comes with high NOx and soot. Leveraging the key merits of PCCI and conventional combustion in a practical engine is both meaningful and challenging.

For the application of advanced clean combustion technologies, such as diesel HCCI/LTC, a compressor with high efficiency over a broad operation range is required to supply a high amount of EGR with minimum pumping loss. A compressor with high pitch of vaneless diffuser would substantially improve the flow range of the compressor, but it is at the cost of compressor efficiency, especially at low mass flow area where most of the city driving cycles resides. In present study, an ultra low solidity compressor vane diffuser was numerically investigated. It is well known that the flow leaving the impeller is highly distorted, unsteady and turbulent, especially at relative low mass flow rate and near the shroud side of the compressor. A conventional vaned diffuser with high stagger angle could help to improve the performance of the compressor at low end. However, adding diffuser vane to a compressor typically restricts the flow range at high end.

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.

A single-cylinder Gasoline Direct Injection Engine (GDI) engine with a centrally mounted spray-guided injection system (150 bar fuel pressure) has been operated with stoichiometric and rich mixtures. The base fuel was 65% iso-octane and 35% toluene; hydrogen was aspirated into a plenum in the induction system, and its equivalence ratios were set to 0, 0.02, 0.05 and 0.1. Ignition timing sweeps were conducted for each operating point. Combustion was speeded up by adding hydrogen as expected. In consequence the MBT ignition advance was reduced, as were cycle-by-cycle variations in combustion. Adding hydrogen led to the expected reduction in IMEP as the engine was operated at a fixed manifold absolute pressure (MAP). An engine model has also been set up using WAVE. Particulate Matter (PM) emissions were measured with a Cambustion DMS500 particle sizer.

In this paper the experiments of hydraulic free piston diesel engine is described. The experimental data were obtained from measurement instruments on the free piston diesel engine that has been developed by Beijing Institute of Technology [ 1 ]. This article discusses the influences of compression pressure, injection timing, and combustion process to the free piston diesel engine principle. The compression process experiment shows that the piston velocity, the compression ratio can be controlled by adjusting the compression pressure. With the increasing of the compression pressure, there is a growing a compression ratio and piston velocity. The study on injection timing shows that the injection timing impacts the cylinder pressure peak value and the pressure peak arrival time. The combustion process is quite different from the crankshaft engine because of the unique piston movement characteristics of the hydraulic free piston engine.

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.

A dual fuel engine simulation model was formulated and the combustion process of a diesel/natural gas dual fuel engine was studied using an updated KIVA-3V Computational Fluid Dynamic (CFD) code. The dual fuel engine ignition and combustion process is complicated since it includes diesel injection, atomization and ignition, superimposed with premixed natural gas combustion. However, understanding of the combustion process is critical for engine performance optimization. Starting from a previously validated Characteristic-Timescale diesel combustion model, a natural gas combustion model was implemented and added to simulate the ignition and combustion process in a dual fuel bus engine. Available engine test data were used for validation of both the diesel-only and the premixed spark-ignition operation regimes. A new formulation of the Characteristic-Timescale combustion model was then introduced to allow smooth transition between the combustion regimes.

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.