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The interaction between a combusting diesel spray and a wall was studied by measuring the spray flame temperature time and spatially resolved. The influence of injection sequences, injection pressure and gas conditions on the heat transfer between the combusting spray and the wall was investigated by measuring the flame temperature during the complete injection event. The flame temperature was measured by an emission based optical method and determined by comparing the relative emission intensities from the soot in the flame at two wavelength intervals. The measurements were done by employing a monochromatic and non intensified high speed camera, an array of mirrors, interference filters and a beam splitter. The studies were carried out in the Chalmers High Pressure High Temperature (HP/HT) spray rig at conditions similar to those prevailing in a direct injected diesel engine prior to the injection of fuel.

A series of experimental studies of diesel spray combustion was carried out using non-circular and back-step orifices. The experiments were performed in a single-cylinder engine and in a constant volume combustion chamber. In the engine tests, elliptic orifices with an aspect ratio of approximately 2:1 were compared with circular orifices. The elliptic orifices had sharp inlets and the circular orifices had rounded inlets. Elliptic orifices aligned with either the minor axis or the major axis in the direction of the nozzle tip were tested. The orifice shapes had minor effects on the heat release, ignition delay, and emissions of smoke, CO and HC. However, substantial differences were observed for emissions of NOx: for the vertical elliptic orifices, emissions up to 37.6 percent lower than with circular orifices were observed. In the combustion bomb tests, rectangular and back-step orifices were compared with circular orifices, all with sharp inlets.

In this work, we conducted three-dimensional numerical simulations to investigate the effect of ultra-high injection pressure on diesel ignition and flame under high-boost and medium-load conditions. Three injection cases employed in experiments with a multi-cylinder Volvo D12 engine were applied for validation. The simulations were performed using the KIVA-3V code, with a Kelvin-Helmholz/Rayleigh-Taylor (KH/RT) spray breakup model and a diesel surrogate mechanism involving 83 species and 445 reactions. A range of higher injection pressure levels were projected and the injection rates estimated for the current study. Three different rate shapes of injection were projected and investigated as well. All the projected injection events start at top dead center (TDC). Computations demonstrate that high-pressure injection strongly affects engine ignition and combustion.

A Turbulent Flame Speed Closure Model is modified and implemented into the FIRE code for use in 3D computations of combustion in an SI-engine. The modifications are done to account for mixture inhomogeneity, and mixture compression through the dependency of local equivalence ratio, pressure and temperature on the chemical time scale and a global reaction time scale. The model is also subjected to further evaluation against experimental data, covering different mixture and turbulence conditions. The combustion process in a 4-valve pentroof combustion chamber is simulated and heat release rates and spatial flame distribution are evaluated against experimental data. The computations show good agreement with the experiments. The model has proven to be a robust and time effective simulation tool with good predictive ability.

A novel concept of combined hydrogen production and power generation system based on the combustion of aluminum in water is explored. The energy conversion system proposed is potentially able to provide four different energy sources, such us pressurized hydrogen, high temperature steam, heat, and work at the crankshaft on demand, as well as to fully comply with the environment sustainability requirements. Once aluminum oxide layer is removed, the pure aluminum can react with water producing alumina and hydrogen while releasing a significant amount of energy. Thus, the hydrogen can be stored for further use and the steam can be employed for energy generation or work production in a supplementary power system. The process is proved to be self-sustained and to provide a remarkable amount of energy available as work or hydrogen.

Soot formation and oxidation are complex and competing processes during diesel combustion. The balance between the two processes and their history determines engine-out soot values. Besides the efforts to lower soot formation with measures to influence the flame lift-off distance for example or to use HCCI-combustion, enhancement of late soot oxidation is of equal importance for low-λ diffusion-controlled low emissions combustion with EGR. The purpose of this study is to investigate soot oxidation in a heavy duty diesel engine by statistical analysis of engine data and in-cylinder endoscopic high speed photography together with CFD simulations with a main focus on large scale in-cylinder gas motion. Results from CFD simulations using a detailed soot model were used to reveal details about the soot oxidation.

To elucidate the processes controlling the auto-ignition timing and overall combustion duration in homogeneous charge compression ignition (HCCI) engines, the distribution of the auto-ignition sites, in both space and time, was studied. The auto-ignition locations were investigated using optical diagnosis of HCCI combustion, based on laser induced fluorescence (LIF) measurements of formaldehyde in an optical engine with fully variable valve actuation. This engine was operated in two different modes of HCCI. In the first, auto-ignition temperatures were reached by heating the inlet air, while in the second, residual mass from the previous combustion cycle was trapped using a negative valve overlap. The fuel was introduced directly into the combustion chamber in both approaches. To complement these experiments, 3-D numerical modeling of the gas exchange and compression stroke events was done for both HCCI-generating approaches.

The aim of this study was to examine the influence of computer manikin users' background and knowledge for the results of a computer manikin simulation. Subjects taking part in the study were either production engineers or ergonomists. A manual task that presented production and ergonomics problems was used. The task was simulated prior to the subjects' sessions, using the computer manikin software Jack. During the sessions, the animated simulation was shown to the test subject. Results show that there are differences in how production engineers and ergonomists interpret results from a manikin simulation. Depending on the user's background, certain aspects that are difficult to visualise with the computer manikin were interpreted differently, regarding e.g. detected problems and holistic perspectives.

A validation study of the numerical model of n-heptane spray combustion based on experimental constant-volume data [1] was done, by comparing auto-ignition delays for different pre - turbulence levels and initial temperatures, flame contours, and soot distributions under Diesel-like conditions. The basic novelty of the methodology developed in [2] - [3] is the implementation of the partially stirred reactor (PaSR) model accounting for detailed chemistry / turbulence interactions. It is based on the assumption that the chemical processes proceed in two successive steps: micro mixing, simulated on a sub - grid scale, is followed by the reaction act. When the all Re number RNG k-ε or LES models are employed, the micro mixing time can be consistently defined giving the combustion model a “well-closed” form incorporated into the KIVA-3V code.

Heat transfer to the walls of the combustion chamber is increased by engine knock. In this study the influence of knock onset and knock intensity on the heat flux is investigated by examining over 10 000 individual engine cycles with a varying degree of knock. The heat transfer to the walls was estimated by measuring the combustion chamber wall temperature in an SI engine under knocking conditions. The influence of the air-fuel ratio and the orientation of the oscillating cylinder pressure-relative to the combustion chamber wall-were also investigated. It was found that knock intensities above 0.2 Mpa influenced the heat flux. At knock intensities above 0.6 Mpa, the peak heat flux was 2.5 times higher than for a non-knocking cycle. The direction of the oscillations did not affect the heat transfer.

An engine with variable valve timing was operated in homogeneous charge compression ignition (HCCI) mode. In two sets of experiments, the fuel was introduced directly into the combustion chamber using a split injection strategy. In the first set, lambda was varied while the fuel flow was constant. The second set consisted of experiments during which the fuel flow was altered and lambda was fixed. The results were evaluated using an engine simulation code with integrated detailed-chemistry. The auto-ignition temperature of the air-fuel mixture was reached when residual mass of the previous combustion cycle was captured using a negative valve overlap and compressed together with the fresh mixture charge inducted. When a pilot fuel amount was introduced in the combustion chamber before piston TDC, during the negative valve overlap, radicals were formed as well as intermediates and combustion took place during this overlap provided the mixture was lean.

Many new combustion concepts are currently being investigated to further improve engines in terms of both efficiency and emissions. Examples include homogeneous charge compression ignition (HCCI), lean stratified premixed combustion, stratified charge compression ignition (SCCI), and high levels of exhaust gas recirculation (EGR) in diesel engines, known as low temperature combustion (LTC). All of these combustion concepts have in common that the temperatures are lower than in traditional spark ignition or diesel engines. To further improve and develop combustion concepts for clean and highly efficient engines, it is necessary to develop new computational tools that can be used to describe and optimize processes in nonstandard conditions, such as low temperature combustion.

Today numerical models are a major part of the diesel engine development. They are applied during several stages of the development process to perform extensive parameter studies and to investigate flow and combustion phenomena in detail. The models are divided by complexity and computational costs since one has to decide what the best choice for the task is. 0D models are suitable for problems with large parameter spaces and multiple operating points, e.g. engine map simulation and parameter sweeps. Therefore, it is necessary to incorporate physical models to improve the predictive capability of these models. This work focuses on turbulence and mixing modeling within a 0D direct injection stochastic reactor model. The model is based on a probability density function approach and incorporates submodels for direct fuel injection, vaporization, heat transfer, turbulent mixing and detailed chemistry.

Environmental and economic issues related to the aeronautic transport, with particular reference to the high-speed one are opening new perspectives to pulsejets and derived pulse detonation engines. Their importance relates to high thrust to weight ratio and low cost of manufacturing with very low energy efficiency. This papers presents a preliminary evaluation in the direction of a new family of pulsejets which can be coupled with both an air compression system which is currently in pre-patenting study and a more efficient and enduring valve systems with respect to today ones. This new pulsejet has bee specifically studied to reach three objectives: a better thermodynamic efficiency, a substantial reduction of vibrations by a multi-chamber cooled architecture, a much longer operative life by more affordable valves. Another objective of this research connects directly to the possibility of feeding the pulsejet with hydrogen.

In this paper, the turbulent flow induced by a production side-view mirror assembled on a full-scale production truck is simulated using a compressible k-ω SST detached eddy simulation (DES) approach -- the improved delayed DES (IDDES). The truck configuration consists of a compartment and a trailer. Due to the large size and geometric complexity of the configuration, some simplifications are applied to the simulation. A purpose of this work is to investigate whether the simplifications are suitable to obtain the reasonable properties of the flow near the side-view mirror. Another objective is to study the aerodynamic performances of the mirror. The configuration is simplified regarding two treatments. The first treatment is to retain the key exterior components of the truck body while removing the small gaps and structures. Furthermore, the trailer is shaped in an apex-truncated square pyramid.

Neck injuries in rear-end collisions are usually caused by a swift extension-flexion motion of the neck and mostly occur at low impact velocities (typically less than 20 km/h). Although the injuries are classified as AIS 1, they often lead to permanent disability. The injury risk varies a great deal between different car models. Epidemiological studies show that the effectiveness of passenger-car head-restraints in rear-end collisions generally remains poor. Rear-end collisions were simulated on a crash-sled by means of a Hybrid III dummy with a new neck (Rear Impact Dummy-neck). Seats were chosen from production car models. Differences in head-neck kinematics and kinetics between the different seats were observed at velocity changes of 5 and 12.5 km/h. Comparisons were made with an unmodified Hybrid III. The results show that the head-neck motion is influenced by the stiffness and elasticity of the backrest as well as by the properties of the head-restraint.

This work presents a numerical method for predictions of HC oxidation in the cold turbulent wall jet emerging from the piston top land crevice in an S.I. engine, using a complex chemical reaction model. The method has been applied to an engine model geometry with the aim to predict the HC oxidation rate under engine - relevant conditions. According to the simulation a large amount of HC survives oxidation due to the long ignition delay of the wall jet emitted from the crevice. This ignition delay, in turn depends mainly on chemical composition and temperature of the gas mixture in the crevice and also on the temperature distribution in the cylinder boundary layer.

Computational simulations of the spray combustion and emissions formation processes in a heavy-duty DI diesel engine and in a small-bore DI diesel engine with a complicated injection schedule were performed by using the modified KIVA3V, rel. 2 code. Some initial parameter sets varying engine operating conditions, such as injection pressure, injector nozzle diameter, EGR load, were examined in order to evaluate their effects on the engine performance. Full-scale combustion chamber representations on 360-deg, Cartesian and polar, multiblock meshes with a different number of sprays have been used in the modelling unlike the conventional approach based on polar sector meshes covering the region around one fuel spray. The spray combustion phenomena were simulated using the detailed chemical mechanism for diesel fuel surrogate (69 species and 306 reactions).

The INCOLL or INertia COLLection system described in this paper, should meet the requirements for a short transient test, without using any chassis dynamometer. To prove this point not only the background of its principles are described, but also results from its application both to S I engines with and without catalytic converters and to truck diesel engines. Special interest has been devoted to the oxygen sensor and converter efficiency and their response both during warm up and under transient conditions. The simplification of the analyzing equipment and the direct interpretation of the results, have been dealt with, as well as the repeativity of the results achieved. The INCOLL test may also have a potential use as quality test at the end of the production line and as a tool for reliability development as well as research and development within the field. The cost for an INCOLL test is estimated to be around one (1) percent of a normal FTP certification procedure.

Pre-chamber combustion (PCC) has re-emerged in recent last years as a potential solution to help to decarbonize the transport sector with its improved engine efficiency as well as providing lower emissions. Research into the combustion process inside the pre-chamber is still a challenge due to the high pressure and temperatures, the geometrical restrictions, and the short combustion durations. Some fundamental studies in constant volume combustion chambers (CVCC) at low and medium working pressures have shown the complexity of the process and the influence of high pressures on the turbulence levels. In this study, the pre-chamber combustion process was investigated by combustion visualization in an optically-accessible pre-chamber under engine relevant conditions and linked with the jet emergence inside the main chamber. The pre-chamber geometry has a narrow-throat. The total nozzle area is distributed in two six-hole rows of nozzle holes.