Dynamics of Post-Injection Fuel Flow in Mini-Sac Diesel Injectors Part 1: Admission of 1 External Gases and Implications for Deposit Formation

Samples of unadditized, middle distillate diesel fuel were injected through real-size optically accessible mini-sac diesel injectors into ambient air at common rail pressures of 250 bar and 350 bar respectively. High-resolution images of white light scattered from the internal mini-sac and nozzle flow were captured on a high-speed monochrome video camera. Following the end of each injection, the momentum-driven evacuation of fuel liquid from the mini-sac and nozzle holes resulted in the formation of a vapour cloud and bubbles in the mini-sac, and vapour capsules in the nozzle holes. This permitted external gas to gain entrance to the nozzle holes. The diesel fuel in the mini-sac was observed to rotate with large initial vorticity, which decayed until the fuel became stationary. The diesel fuel remaining in the nozzle holes was observed to move inwards towards the mini-sac or outwards towards the nozzle exit in concert with the rotational flow in the mini-sac. The mini-sac bubbles’ internal pressure differences revealed that the bubbles must have contained previously dissolved oxygen and nitrogen. Under diesel engine operating conditions, this multi-phase mixture would be highly reactive and could initiate local pyrolysis and/or oxidation reactions. Finally, the dynamical behaviour of the diesel fuel in the nozzle holes would support the admission of external hot combustion gases into the nozzle holes, establishing the conditions for oxidation/pyrolysis reactions with surrounding liquid fuel films

Design and development of auxiliary components for a new two-stroke, stratified-charge, lean-burn gasoline engine

A unique stepped-piston engine was developed by a group of research engineers at Universiti Teknologi Malaysia (UTM), from 2003 to 2005. The development work undertaken by them engulfs design, prototyping and evaluation over a predetermined period of time which was iterative and challenging in nature. The main objective of the program is to demonstrate local R&D capabilities on small engine work that is able to produce mobile powerhouse of comparable output, having low-fuel consumption and acceptable emission than its crankcase counterpart of similar displacement. A two-stroke engine work was selected as it posses a number of technological challenges, increase in its thermal efficiency, which upon successful undertakings will be useful in assisting the group in future powertrain undertakings in UTM. In its carbureted version, the single-cylinder aircooled engine incorporates a three-port transfer system and a dedicated crankcase breather. These features will enable the prototype to have high induction efficiency and to behave very much a two-stroke engine but equipped with a four-stroke crankcase lubrication system. After a series of analytical work the engine was subjected to a series of laboratory trials. It was also tested on a small watercraft platform with promising indication of its flexibility of use as a prime mover in mobile platform. In an effort to further enhance its technology features, the researchers have also embarked on the development of an add-on auxiliary system. The system comprises of an engine control unit (ECU), a directinjector unit, a dedicated lubricant dispenser unit and an embedded common rail fuel unit. This support system was incorporated onto the engine to demonstrate the finer points of environmental-friendly and fuel economy features. The outcome of this complete package is described in the report, covering the methodology and the final characteristics of the mobile power plant

Towards design of prognostics and health management solutions for maritime assets

With increase in competition between OEMs of maritime assets and operators alike, the need to maximize the productivity of an equipment and increase operational efficiency and reliability is increasingly stringent and challenging. Also, with the adoption of availability contracts, maritime OEMs are becoming directly interested in understanding the health of their assets in order to maximize profits and to minimize the risk of a system's failure. The key to address these challenges and needs is performance optimization. For this to be possible it is important to understand that system failure can induce downtime which will increase the total cost of ownership, therefore it is important by all means to minimize unscheduled maintenance. If the state of health or condition of a system, subsystem or component is known, condition-based maintenance can be carried out and system design optimization can be achieved thereby reducing total cost of ownership. With the increasing competition with regards to the maritime industry, it is important that the state of health of a component/sub-system/system/asset is known before a vessel embarks on a mission. Any breakdown or malfunction in any part of any system or subsystem on board vessel during the operation offshore will lead to large economic losses and sometimes cause accidents. For example, damages to the fuel oil system of vessel's main engine can result in huge downtime as a result of the vessel not being in operation. This paper presents a prognostic and health management (PHM) development process applied on a fuel oil system powering diesel engines typically used in various cruise and fishing vessels, dredgers, pipe laying vessels and large oil tankers. This process will hopefully enable future PHM solutions for maritime assets to be designed in a more formal and systematic way

Spontaneous ignition delay characteristics of hydrocarbon fuel-air mixtures

The influence of pressure on the autoignition characteristics of homogeneous mixtures of hydrocarbon fuels in air is examined. Autoignition delay times are measured for propane, ethylene, methane, and acetylene in a continuous flow apparatus featuring a multi-point fuel injector. Results are presented for mixture temperatures from 670K to 1020K, pressures from 1 to 10 atmospheres, equivalence ratios from 0.2 to 0.7, and velocities from 5 to 30 m/s. Delay time is related to pressure, temperature, and fuel concentration by global reaction theory. The results show variations in global activation energy from 25 to 38 kcal/kg-mol, pressure exponents from 0.66 to 1.21, and fuel concentration exponents from 0.19 to 0.75 for the fuels studied. These results are generally in good agreement with previous studies carried out under similar conditions

Experimental techniques and numerical models to detect pollutant emission in the transport sector

25th International Conference on Urban Transport and the Environment, Urban Transport 2019; Aveiro; Portugal; 25 June 2019 through 27 June 2019; Code 155807In recent years, the growth of fossil fuel use and greenhouse gases emissions (GHGs) has been promoted by the population increase and development of the industry sector. Due to the increasing attention towards the effects of climate changes on quality of life, recent researches on pollutant formation processes have been developed in different sectors, especially in transportation. The last emission standards on pollutants impose limits on the dimensions and on the particle number of the particulate matter emissions, because of the highly dangerous effect on human health. To fight high concentrations of particulate matter (PM) emissions, a wide number of studies are addressed towards the definition of the most important parameters in effective production of particulate matter, especially in spark ignition engines. Physical processes such as mixture formation, engine operating parameters and fuel chemical properties strongly affect the soot formation in gasoline engines. The heat transfer process between the piston hot surface and the fuel gasoline during the post-injection phase is a key aspect of soot emissions for an engine. This paper is devoted to analyzing the fundamental parameters that are responsible for pollutant formation in the transport sector and the actual experimental and numerical techniques used to predict the environmental impact of engines

Optical fuel spray characterization of hydrotreated vegetable oil (HVO) and ethanol

The global concern about climate change has remarkably increased because of its tangible environmental effects. Transportation being one of the major contributors to greenhouse gas emissions is taking a substantial part in global warming and climate change. Fortunately, the shift of emerging transportation technology towards electric power sources has proven to be a favorable solution towards sustainable and cleaner transportation addressing global climate change. However, some constraints related to battery technologies and charging infrastructure created a necessity of research towards alternative cleaner fuels for internal combustion engines. Ethanol is one of the alternative fuel that has caught much attention because of its remarkably low emissions. The experimental study in this thesis investigated the comparison of HVO and ethanol with EN590 diesel fuel sprays in terms of overall spray geometry and droplet size measurements by analyzing the monochrome spray images. The fuel sprays were injected using two different fuel injectors with different nozzle orifice diameters into a constant volume chamber at varying conditions of injection pressure and gas density. In terms of overall spray geometry and droplet size measurements, HVO and EN590 diesel sprays showed quite similar trends, however, significant differences could be observed for ethanol sprays. Ethanol sprays were characterized with lower penetration, larger opening angles and smaller droplet sizes than HVO and EN590 sprays. A Significant decrease in mean diameters and droplet size distributions could be identified by increasing the injection pressures. Furthermore, the results for the injector with increased nozzle orifice diameter compared with the reference nozzle suggested decrement in spray penetration and increased opening angles for EN590 fuel sprays

Modification of an ignition quality tester and its use in characterizing middle distillate fuels

The Ignition Quality Tester ( IQTTM ) is a constant volume combustion chamber based device which is used to determine the derived cetane number of diesel fuel oils when used in conjunction with ASTM D6890. During a test, the fuel sample is injected into heated, pressurised gas where it combusts. Suitable measurements are made during the combustion event to determine the ignition delay of the fuel and the latter is used with a correlation to determine the derived cetane number of the sample. The IQT offers improved repeatability and reproducibility when compared with the conventional method of determining cetane number, namely ASTM D613. Despite these advantages, the device features a fuel injection system not indicative of the state of the art, in terms of direct injection diesel components and associated fuel spray behavior. Therefore this project sought to make suitable mechanical, electrical and control modifications to incorporate a more technologically appropriate injector. It is believed that by improving the spray characteristics of the IQT along with the incorporation of a flexible control system, that it can be leveraged to a greater extent in a fuels research context. The modifications made to the system included the incorporation of a single hole common rail diesel injector along with a custom control system. The control system allowed flexible control of all variables considered to be significant to the study of auto-ignition delays. Additionally, an optical sensor was added to detect luminous emissions from the reacting fuels. The modified system was used to rate diesel fuels with varied composition including solvents, diesel primary reference fuels, crude derived as well as Low Temperature Fischer Tropsch (LTFT) products. These tests were performed at two temperatures and oxygen concentrations and the resulting data was used to redevelop correlations between the cetane number of the respective samples and their ignition delays in order to surmise the optimal operating conditions of the modified IQT