Time-resolved fuel injector flow characterisation based on 3D laser Doppler vibrometry

In order to enable investigations of the fuel flow inside unmodified injectors, we have developed a new experimental approach to measure time-resolved vibration spectra of diesel nozzles using a three dimensional laser vibrometer. The technique we propose is based on the triangulation of the vibrometer and fuel pressure transducer signals, and enables the quantitative characterisation of quasi-cyclic internal flows without requiring modifications to the injector, the working fluid, or limiting the fuel injection pressure. The vibrometer, which uses the Doppler effect to measure the velocity of a vibrating object, was used to scan injector nozzle tips during the injection event. The data were processed using a discrete Fourier transform to provide time-resolved spectra for valve-closed-orifice, minisac and microsac nozzle geometries, and injection pressures ranging from 60 to 160MPa, hence offering unprecedented insight into cyclic cavitation and internal mechanical dynamic processes. A peak was consistently found in the spectrograms between 6 and 7.5kHz for all nozzles and injection pressures. Further evidence of a similar spectral peak was obtained from the fuel pressure transducer and a needle lift sensor mounted into the injector body. Evidence of propagation of the nozzle oscillations to the liquid sprays was obtained by recording high-speed videos of the near-nozzle diesel jet, and computing the fast Fourier transform for a number of pixel locations at the interface of the jets. This 6-7.5kHz frequency peak is proposed to be the natural frequency for the injector's main internal fuel line. Other spectral peaks were found between 35 and 45kHz for certain nozzle geometries, suggesting that these particular frequencies may be linked to nozzle dependent cavitation phenomena.Comment: 12 pages, 10 figure

A finite element approach for the implementation of magnetostrictive material terfenol-D in automotive CNG fuel injection actuation

Magnetostriction is the deformation that spontaneously occurs in ferromagnetic materials when an external magnetic field is applied. In applications broadly defined for actuation, magnetostrictive material Terfenol-D possesses intrinsic rapid response times while providing small and accurate displacements and high-energy efficiency, which are some of the essential parameters required for fast control of fuel injector valves for decreased engine emissions and lower fuel consumption compared with the traditional solenoid fuel injection system. A prototype CNG fuel injector assembly was designed, which primarily included magnetostrictive material Terfenol-D as the actuator material, 1020 Steel having soft magnetic properties as the injector housing material, AWG copper wire as the coil material and 316 Stainless Steel having non-magnetic properties as the plunger material. A 2D cross-sectional geometry including the injector housing, coil, Terfenol-D shaft, and plunger, was modeled in both Finite Element Method Magnetics (FEMM) and ANSYS for 2D axisymmetric magnetic simulation. The magnetic simulations were performed in order to determine the coil-circuit parameters and the magnetic field strength to achieve the required magnetostrictive strain, and consequently, the injector needle lift. The FEMM magnetic simulations were carried out with four different types of AWG coil wires and four different injector coil thicknesses in order to evaluate the relationship between the different coil types and thicknesses against the achieved strain or injector lift. Eventually, the optimized parameter obtained from FEMM results analysis was verified against ANSYS electromagnetic simulation. Subsequently, a three dimensional replica of the CNG flow conduit was modelled in GAMBIT with the resultant injector lift. The meshed conduit was then simulated in FLUENT using the 3D time independent segregated solver with standard k-ε, realizable k-ε and RSM turbulent models to predict the mass flow rate of CNG to be injected. Eventually, the simulated flow rates were verified against mathematically derived static flow rate required for a standard automotive fuel injector considering standard horsepower, BSFC and injector duty cycle

Ensuring the reliability and performance criterias of crankshafts

The issues of efficiency improvement of manufacturing crankshafts in order to ensure their reliability and performance criteria are the priorities in modern production of internal combustion engines. Using the capabilities of modern special grinding machines can improve the quality of machining and obtain the necessary running characteristics of crankshafts. In work the questions connected with development of a method of calculation of rigidity of crankshafts for increase of accuracy of their machining, reliability and performance criteria’s are considered. Based on the proposed methodology, numerical calculations have performed and the possibility of determining the deflections and crankshafts rigidity in any section have been justified. The original construction of the following grinding steady rest for CNC grinding machines specified for machining the crankshaft main bearing journal and connecting rod journal is proposed. The construction design of the device allows for compensating the influence of the cutting force on the elastic strain of the part, depending on the change in its rigidity. The practical value of the research includes in develop recommendations for determining the optimal parameters for the round infeed grinding cycle of the crank pins from the point of view of productivity and accuracy

Development of in-cylinder injection for a hydrogen-fueled internal combustion engine

Traditional means for converting an engine to operate on hydrogen fuel incorporates port injection. The typical method for controlling emissions on a port injection engine is to operate the engine lean (typical AFR of 70:1) and/or incorporate an EGR system. The result of utilizing these methods is an appreciable reduction in power output. In-cylinder injection of an internal combustion engine provides a reliable method for delivering hydrogen fuel whereby fuel efficiency, power output and emissions levels are improved. Injection of hydrogen directly into the combustion chamber allows control of various factors such as burn rate and combustion timing which influence the production of emissions in the form of NOx. Testing of the converted engines has also shown an increase in power due to an increase in volumetric efficiency and a reduction of emissions at near stoichiometric operation. Details for converting an engine to an in-cylinder hydrogen injection, computer systems control, emissions testing and performance evaluation are given

Theoretical and experimental investigation of a CDI injection system operating on neat rapeseed oil - feasibility and operational studies

This thesis presents the work done within the PhD research project focusing on the utilisation of plant oils in Common Rail (CR) diesel engines. The work scope included fundamental experimental studies of rapeseed oil (RSO) in comparison to diesel fuel, the feasibility analysis of diesel substitution with various plant oils, the definition and implementation of modifications of a common rail injection system and future work recommendations of possible changes to the injection system. It was recognised that neat plant oils can be considered as an alternative substitute for diesel fuel offering a natural way to balance the CO2 emissions. However, due to the differences between diesel and plant oils, such as density, viscosity and surface tension, the direct application of plant oils in common rail diesel engines could cause degradation of the injection process and in turn adversely affect the diesel engine’s performance. RSO was chosen to perform the spray characterisation studies at various injection pressures and oil temperatures under conditions similar to the operation of the common rail engine. High speed camera, Phase Doppler Anemometry and Malvern laser techniques were used to study spray penetration length and cone angle of RSO in comparison to diesel. To study the internal flow inside the CR injector the acoustic emission technique was applied. It was found that for oil temperatures below 40°C the RSO viscosity, density and surface tension are higher in comparison to diesel, therefore at injection pressures around 37.50 MPa the RSO spray is not fully developed. The spray penetration and cone angle at these spray conditions exhibit significant spray deterioration. In addition to the lab experiments, KIVA code simulated RSO sprays under CR conditions. The KH-RT and RD breakup models were successfully applied to simulate the non-evaporating sprays corresponding to the experimental spray tests and finally to predict i real in-cylinder injection conditions. Numerical results showed acceptable agreement with the experimental data of RSO penetration. Based on experimental and numerical results it was concluded that elevated temperature and injection pressure could be the efficient measures to overcome operational obstacles when using RSO in the CR diesel engine. A series of modifications of low- and highpressure loops was performed and experimentally assessed throughout the engine tests. The results revealed that the modifications allowed to run the engine at the power and emission outputs very close to diesel operation. However, more fundamental changes were suggested as future work to ensure efficient and trouble-free long-term operation. It is believed that these changed should be applied to meet Euro IV and V requirements

HIGH INJECTION PRESSURE DME IGNITION AND COMBUSTION PROCESSES: EXPERIMENT AND SIMULATION

With nearly smokeless combustion, Dimethyl Ether (DME) can be pressurized and used as a liquid fuel for compression-ignition (CI) combustion. However, due to its lower heating value and liquid density compared with diesel fuel, DME has a smaller energy content per unit volume. To obtain an equivalent energy content of diesel, approximately 1.86 times more quantity of DME is required. This can be addressed by a larger nozzle size or higher injection pressure. However, the effect of high injection pressure on DME spray combustion characteristics have not yet been well understood. In order to fill this gap, spray and combustion processes of DME were studied extensively via a series of experiments in a constant-volume and optically accessible combustion vessel. In the current study, a hydraulic electric unit injector (HEUI) with a 180 µm single-hole nozzle was driven by an oil-pressurized fuel injection (FI) system to achieve injection pressure of 1500 bar. The liquid and vapor regions of DME jet were visualized using a hybrid Schlieren/Mie scattering at non-reacting conditions. At reacting conditions, high-speed natural flame luminosity of DME combustion was used to capture the flame intensity, and planar laser-induced fluorescence (PLIF) imaging was used to characterize CH2O evolution. Spray and combustion characteristics of DME were compared with diesel in terms of rate of injection (ROI), liquid/vapor penetration and, ignition delay. Flame lift-off length (LOL), flame structure, and formaldehyde (CH2O) formation of DME were also studied through high-speed imaging. The RANS Converge CFD simulation was validated against the experimental and used as a powerful tool to explore the DME spray characteristics under various conditions. Further insights into DME spray and flame structure were obtained through experimentally validated Large Eddy Simulations (LES) simulations