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In this work a new concept for GDI engines is presented. Concerning a stable ignition a main goal of the so called Bowl-Pre-chamber-Ignition (BPI) process is to reduce the influence of varying flow and spray effects. The characteristic signs of the concept are the dual direct injection, a centrally arranged piston bowl and the special pre-chamber spark plug, that partly dips into the bowl at TDC. During that process most fuel is injected early (intake stroke) into the intake manifold or directly into the cylinder to form a homogeneous pre-mixture. Later in the compression stroke, only a small amount of fuel is injected into the piston bowl. So formed locally stratified charge mixture is transported by the piston bowl to the pre-chamber-spark plug, the pre-chamber dips into the bowl and the mixture flows directly to the spark plug electrode. The result is a very stable lean combustion.

This paper describes the numerical results for a simplified underhood buoyancy driven flow. The simplified underhood geometry consists of an enclosure, an engine block and two exhaust cylinders mounted along the sides of the engine block. The flow condition is set up in such a way that it mimics the buoyancy driven flow condition in the underhood environment when the vehicle is parked in a windbreak with the engine shut down. The experimental measurements for temperature and velocity of the same configuration were documented in the Part I of the same title. Present study focuses on the numerical issues of calculating temperature and flow field for the same flow configuration. The predicted temperature and velocity were compared with the available measured data. The mesh sizes, mesh type and the orders of spatial and temporal accuracy of the numerical setup are discussed.

The results of thermal and flow studies for a ¼ scale model of an engine compartment are presented here. Using PIV and thermocouples, the mid-plane flow velocity and temperature of the buoyant underhood flow with engine block average surface temperature of 127°C and exhaust heaters (surface temperature ∼ 600°C) were measured. Thermocouples were also used to measure the steady-state temperature of the engine block surface and the enclosure outside and inside walls. The airflow in the engine compartment is steady, laminar and three dimensional as predicted by the Grashof and Reynolds numbers calculated for different simple geometries comprising the engine block and its exhausts. Three dominant vortices are found to exist at the top corners of the engine compartment. Thermal measurements on the engine block and enclosure surfaces support the temperature gradients expected given the specified geometry and boundary conditions.

Diesel powered underground mining equipment is presently the most productive and efficient type of equipment used in underground mining operations. Uncertainties regarding ventilating air levels, which will minimize the risk to health, focus on the role of diesel particulate, both as a toxic agent itself, and as a carrier for other exhaust constituents such as acid gases. This paper describes the application of Catalytic Trap Oxidizer (CTO) Systems for particulate emission control to a test-bed engine and a mining vehicle in service. Testing procedures and results are presented for both laboratory and in-service evaluations. Gaseous and particulate emissions are compared for baseline and CTO-equipped operation and correlation of laboratory and in-service test results is discussed. The CTO systems demonstrated significant reductions in total particulate emissions, the level of PAH's and Ames mutagenic activity.

This paper will focus on the spray characteristics of a high pressure (up to 155 MPa) accumulator type injector in a high pressure (chosen density) quiescent spray chamber. The injector uses a standard single orifice nozzle which produces a full cone spray. Using this apparatus, we are examining the fundamental aspects of high pressure spray formation under controlled conditions. Experimental data was collected using high speed photography (10,000 frames per second) which used a pulsed copper-vapor laser as a light source. Two photographic techniques are being utilized. Direct attenuation allows measurement of tip penetration, spray cone angle, and injection duration. Scattering from a sheet of laser light perpendicular to the camera field of view is being developed in an attempt to resolve inner spray cone structure. In addition to the quantitative data from the high speed photography, injector accumulator pressure, supply pressure and injection rate histories were recorded.

The results of an optical investigation into the combustion characteristics of GTL (Gas-To-Liquids) diesel fuel are presented. The investigation was carried out using a high pressure, constant volume combustion chamber with optical access, fitted with a modern diesel injection system. Combustion images were captured under conditions which simulate those present in a diesel engine. A low sulphur diesel fuel meeting the European EN590 specification was used as a reference. Image capture and subsequent analysis was performed by means of an AVL Visioscope system which used the two-colour method to yield quantitative information regarding flame temperature and soot concentration. Conditions in the combustion chamber are preset by combusting a pre-charge to generate the necessary pressure, temperature, and residual gas fraction. This allowed the effect of varying oxygen concentration at the start of diesel combustion to be investigated.

Partially Premixed Combustion (PPC) has shown its potential by combining high combustion controllability with emission characteristics that are close to those of an HCCI engine. In order to get PPC the ignition delay needs to be long enough for the fuel and air to mix prior to combustion. This can be achieved by injecting the fuel sufficiently early while running with high EGR. In order to find out where and how PPC occurs a map that shows the changes in combustion characteristics with injection timing and EGR was created. The combustion characteristics were studied in a six cylinder heavy duty engine where the Start of Injection (SOI) was swept from early to late injection over a wide range of EGR levels. The emissions were monitored during the sweeps and in the most promising regions, with low emissions and high efficiency, additional changes in injection pressure and engine speed were applied to get a more versatile picture of the combustion.

The combustion propagation mechanism of homogeneous charge compression ignition combustion was investigated using planar laser Rayleigh scattering thermometry, and was compared to that of spark-ignition combustion. Ethylene and dimethyl ether were chosen as the fuels for SI and HCCI experiments and have nearly constant Rayleigh scattering cross-sections through the combustion process. Beam steering at the entrance window limited the load range for HCCI conditions and confined the quantitative interpretation of the results to local regions over which an effective beam steering correction could be applied. The SI conditions showed a clear bimodal temperature behavior with a well-defined interface between reactants and products. The HCCI results showed large regions that were partially combusted, i.e., at a temperature above the reactants but below the adiabatic flame temperature. Dual-imaging experiments confirm that the burned region was progressing towards the fully burned state.

The tradeoff between NOx emissions and combustion instability in an engine operating in the dual-fuel Reactivity Controlled Compression Ignition (RCCI) combustion mode was investigated using a combination of engine experiments and detailed CFD modeling. Experiments were performed on a single cylinder version of a General Motors/Fiat JTD 1.9L four-cylinder diesel engine. Gasoline was injected far upstream of the intake valve using an air assisted injector and fuel vaporization system and diesel was injected directly into the cylinder using a common rail injector. The timing of the diesel injection was swept from −70° ATDC to −20° ATDC while the gasoline percentage was adjusted to hold the average combustion phasing (CA50) and load (IMEPg) constant at 0.5° ATDC and 7 bar, respectively. At each operating point the variation in IMEP, peak PRR, and CA50 was calculated from the measured cylinder pressure trace and NOx, CO, soot and UHC were recorded.

The combustion mechanism of a fuel droplet cloud was studied by numerical simulation. We investigated how the flame front speed and combustion products changed depending on the equivalence ratio and initial temperature. Modeling was performed using the KIVA-III software package, a three dimensional analysis software used mainly for internal combustion engine applications. The computational domain was a horizontal 1x1x100 cell sector of a spherical combustion chamber and the fuel was n-decane. Results showed that when all the fuel droplets were assumed to have evaporated, the flame front speed increased from 28 cm/s to 152 cm/s as the equivalence ratio increased. The maximum flame front speed was reached at ϕ=1.1, beyond which it decreased (at richer overall equivalence ratios). With a constant equivalence ratio, the flame front speed decreased near the outside region, because the unburned gas was compressed by the expanding burned gas.

Dimethyl Ether (DME) is one of the major candidates for the next generation fuel for compression ignition (CI) engines. It has good self-ignitability and would not produce particulate, even at rich conditions. DME has proved to be able to apply to ordinary diesel engines with minimal modifications, but its combustion characteristics are not completely understood. In this study, the behavior of a DME spray and combustion process of a direct injection CI engine fueled with DME was investigated by combustion observation and in-cylinder gas sampling. To distinguish evaporated and non-evaporated zones of a spray, direct and schlieren imaging were carried out. The sampled gas from a DME spray was analyzed by gas chromatography, and the major intermediate product histories during ignition period were analyzed.

Often the perceived annoyance of noise does not correspond with the A-weighted sound pressure level. The disagreement is because of the unique directional and pattern-recognition properties of human hearing. Therefore the importance of psychoacoustic attributes, such as perceived loudness (considering masking effects) roughness (modulation of tonal components), sharpness (relationship of high-frequency components to low-frequency ones), harmony (distribution of tonal components), spatial selectivity and so on, is becoming appreciated. The correlation of objective measurement and subjective classification of noise can be improved by considering the final receiver, “human hearing”, and developing methods of deriving and analyzing metric data based on human hearing.

In modern compression ignition engines, the dense liquid fuel is directly injected into high pressure and temperature atmosphere, so the spray transitions from subcritical to supercritical conditions. To gain better control of the spray-combustion heat release process, it is important to have a physically accurate description of the spray development process. This work explored the effect of real-fluid thermodynamics in the computational prediction of multiphase flow for two non-ideal situations: the cryogenic nitrogen and non-cryogenic n-dodecane and ammonia sprays. Three real-fluid equations of state (EoS) such as the Soave-Redlich-Kwong (SRK), Peng-Robinson (PR), and Redlich-Kwong-Peng-Robinson (RKPR) coupled with the real-fluid Chung transport model were implemented in OpenFoam to predict the real-fluid thermodynamic properties. Validations against the CoolProp database were conducted.

Advances in instrumentation, equipment, and techniques now allow a more in-depth analysis of cylinder head motions during internal combustion engine operation. Extensive measurements of these motions were taken on a specific bimetal engine. These measurements were taken during both actual and simulated engine operations. Capacitance probes and eddy current sensors were used to measure large scale motion. The eddy current sensors were also used to measure small scale or micro motion. The results of these measurements are discussed.

Measurements of particulate matter (PM) from spark ignition (SI) engine exhaust using dilution tunnels will become more prevalent as emission standards are tightened. Hence, a study of the dilution process was undertaken in order to understand how various dilution related parameters affect the accuracy with which PM sizes and concentrations can be determined. A SI and a compression ignition (CI) engine were separately used to examine parameters of the dilution process; the present work discusses the results in the context of SI exhaust dilution. A Scanning Mobility Particle Sizer (SMPS) was used to measure the size distribution, number density, and volume fraction of PM. Temperature measurements in the exhaust pipe and dilution tunnel reveal the degree of mixing between exhaust and dilution air, the effect of flowrate on heat transfer from undiluted and diluted exhaust to the environment, and the minimum permissible dilution ratio for a maximum sample temperature of 52°C.

Todays tuning of hydraulic vehicle shock absorbers is mainly an empirical iterative process performed in time-consuming and expensive ride tests, whereas the majority of damper simulation models used for investigating vehicle ride behavior is based on an abstract parameterization. For the manufacturing of automotive dampers, however, the valve code is essential. Minor changes in the valve code describing the shim stack in the hydraulic valves may have a noticeable impact on the damper characteristics, while the physical effects are still not sufficiently understood. Therefore, the paper presents a detailed physics-based structural model to investigate the pressure-deflection behavior of shim stacks and the influence of specific discs in the stack. The model includes a variety of effects like friction and preload, and is capable to predict the damper characteristics.

Wet running multi-plate clutches and brakes are important components of modern automotive and industrial powertrains. In the open stage, drag losses occur due to fluid shearing. This can subsequently lead to a perceptible reduction in the overall drivetrain efficiency. Injection or dip lubrication is used, depending on the application and the requirements. For the former a deep fundamental understanding already exists, whereas up until now the latter has not been extensively investigated. This contribution gives a detailed insight into the experimental research of the drag losses of wet running multi-plate clutches at dip lubrication. In a base study, the flow conditions and origins of the drag torque generation were investigated. Built on this, the effects of operating and geometry parameters, such as oil viscosity and level, clearance, groove design, plate size and number of gaps on the drag loss characteristic, were determined based on full factorial testing.

Many authors have investigated the problem of instability and critical speeds of a rotor supported symmetrically between two identical journal bearings. The present investigation extends this work to a rotor situated at any location either in between or outside the two bearings and the bearings themselves can be of different geometry and dimensions. Such an investigation will be of more practical importance, as many rotor bearing systems in actual use do not conform to the idealized symmetric system.

Auto-ignition with SI-compression ratio can be achieved by replacing some of the fresh charge by hot residuals. In this work an engine is run with a negative valve overlap (NVO) trapping hot residuals. By increasing the NVO, thus raising the initial charge temperature it is possible to investigate the intermediate zone between SI and HCCI as the amount of residuals is increased. Recent research has shown the potential of using spark assistance to aid gasoline HCCI combustion at some operating conditions, and even extend the operating regime into regions where unsupported HCCI combustion is impossible. In this work the influence of the spark is studied in a single cylinder operated engine with optical access. Combustion is monitored by in-cylinder pressure and simultaneous high speed chemiluminescence imaging. It is seen that even for large NVO and thus high residual fractions it is a growing SI flame that interacts with, and governs the subsequent HCCI combustion.

This study investigates the effect of Teflon and adhesive coatings on the torque-tension relationship and the self-loosening performance of threaded fasteners. Two Teflon insulation coatings and one locking adhesive are considered. The torque-tension relationship is established for coated and uncoated fasteners for both tightening and loosening. Finally, the fasteners are tested to determine their self-loosening performance under cyclic transverse loads. A computer controlled fastener tightening system is used to establish the torque-tension relationship during tightening. The coefficients of thread and bearing friction, and the overall nut factor are measured. The breakaway loosening torque of tightened bolts, along with the coefficients of thread and underhead friction and nut factor are investigated. A modified Junker machine is used to evaluate the self-loosening performance of fasteners with various coatings.