With increasing demands for lowering emissions from diesel engines, bio fuel has been introduced to the fuel mixture. This fuel is based on vegetable oil with a much smaller carbon footprint than fossil fuel. The chemical composition of bio fuel has lead to deposits forming inside the fuel injector in diesel engines, these deposits are usually denoted as Internal Diesel Injector Deposits (IDID). At Scania CV AB an injector test rig is designed with the goal of creating and investigating IDID. This project has made a theoretical investigation of how IDID are formed and how this affects the mechanics inside the injector. It has also analysed injector components from a worst case scenario perspective in order to find a testing method for creating IDID in the test rig. By analysing performance changes from a build-up perspective, where IDID decreases the tolerances inside the injector, as well as friction, formed when deposits cause injector mechanics to stick together, it has been found that injector performance does hardly change from build-up and that performance changes only occur when friction is introduced. From the injector component analysis it is found that the limiting factors in rig testing come from fuel system components rather than the injector itself. This is the base for a rig running test method presented.

Manufacturers face the challenge of enhancing fuel efficiency, engine performance, and reducing harmful emissions. Novel fuel injection technologies can assist in meeting such demands. This dissertation summarizes the stages in the design, prototyping and experimental analysis of a direct-acting piezoelectric fuel injector concept. In the proposed design, a piezoelectric stack actuator is used to directly control the injection of fuel in order to enhance the injection characteristics by utilizing the fast response time of the actuator. The direct-acting concept was implemented by developing a motion inverter in the form of a disc that reverses the direction of the input and allows the actuator to directly control injections. Tests with input signals similar to those used in diesel engines confirmed the theoretical calculations and verified the prototype’s performance. This design can control the quantity of injected fuel more precisely than currently available commercial injectors.

Manufacturers face the challenge of enhancing fuel efficiency, engine performance, and reducing harmful emissions. Novel fuel injection technologies can assist in meeting such demands. This dissertation summarizes the stages in the design, prototyping and experimental analysis of a direct-acting piezoelectric fuel injector concept. In the proposed design, a piezoelectric stack actuator is used to directly control the injection of fuel in order to enhance the injection characteristics by utilizing the fast response time of the actuator. The direct-acting concept was implemented by developing a motion inverter in the form of a disc that reverses the direction of the input and allows the actuator to directly control injections. Tests with input signals similar to those used in diesel engines confirmed the theoretical calculations and verified the prototype’s performance. This design can control the quantity of injected fuel more precisely than currently available commercial injectors.

A numerical investigation of the performance of two candidate designs for injection into supersonic flow, including a comparison of two renormalized group theory (RNG) based k-epsilon turbulence models with a more conventional k-epsilon model. The chosen designs were an unswept ramp injector with four injection ports and a novel nine-hole injector array. The objectives of the investigation were to provide reliable computational solutions to the flowfields in question using both RNG and standard k-epsilon turbulence models and to compare the solutions to experiment, thereby to judge the relative performance of the turbulence models. A second objective of the investigation was to use the computed data to provide design insights for the nine-hole injector array. This investigation made use of GASP(tm) version 2.2, a commercial computational fluid dynamics code that was augmented by the addition of one RNG-based k-epsilon turbulence model derived by Zhou, et. al. and one variant of Zhou's model, which was derived by the author. Mesh sequencing studies were performed to measure solution quality, with the fine mesh for the injector array containing roughly one million grid nodes and the fine mesh for the ramp injector containing more than six million grid nodes. Results of these studies indicated that the injector-array solution was significantly under-resolved in the farfield, though the quality was better in the vicinity of the injector itself. The ramp-injector solution, while not perfectly grid-resolved, showed much better grid convergence in both the nearfield and farfield. Accordingly, comparison with experiment was better for the ramp injector than for the injector array. For both injectors, the differences between solutions generated with RNG-based k-epsilon and standard k-epsilon turbulence models were negligibly small." Despite inadequate grid resolution in the farfield, the computational investigation of the nine-hole injector array did yield several important design insights. Particularly, the significance to mixing and losses of the placement of the outer injectors of the second and third rows was determined. / Ph. D.

A total number of 849 tests were conducted to investigate the transient response of liquid injectors with various geometries including different taper angles, injection angles and orifice lengths. High-speed videos were analyzed to characterize refill times and back-flow distances of nine different injector geometries subjected to a ethylene-oxygen detonation wave. Water was used as the working fluid and experiments were performed at two different vessel pressure settings (60 and 100 psia). Although a minimal difference was found between plain and angled injectors due to having constant orifice diameter geometry, introduction of taper angle resulted in more agile injectors with less sensitivity to ambient and feed pressures. Several attempts were made to normalize refill times and obtain a general trend for transient response of liquid injectors.

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Currently there is unprecedented social and political pressure to minimise anthropogenic environmental change. It is a result of the paradoxical nature of emissions reduction that lean-burn technology has become the most likely agent by which future emission targets may be met. However, the inclusion of lean-burn technology requires that the flametube depth is increased, to maintain an acceptable level of pressure drop and sufficient residence time. The injector too must increase in diameter as the admission of air via the fuel nozzle is increased. Maintaining traditional dump style architecture and employing these changes creates a number of additional problems. Most notable is the increased non-uniformity which is inherited by the injector flow as a result of the mismatch between the injector and upstream feed. Injector non-uniformity is a parameter symbiotic with emissions performance and it is therefore imperative to minimise the degree of injector non-uniformity if the ambition of the lean-burn system is to be realised.

abstract: Derived from the necessity to increase testing capabilities of hybrid rocket motor (HRM) propulsion systems for Daedalus Astronautics at Arizona State University, a small-scale motor and test stand were designed and developed to characterize all components of the system. The motor is designed for simple integration and setup, such that both the forward-end enclosure and end cap can be easily removed for rapid integration of components during testing. Each of the components of the motor is removable allowing for a broad range of testing capabilities. While examining injectors and their potential it is thought ideal to obtain the highest regression rates and overall motor performance possible. The oxidizer and fuel are N2O and hydroxyl-terminated polybutadiene (HTPB), respectively, due to previous experience and simplicity. The injector designs, selected for the same reasons, are designed such that they vary only in the swirl angle. This system provides the platform for characterizing the effects of varying said swirl angle on HRM performance. / Dissertation/Thesis / M.S. Aerospace Engineering 2013

Fuel mixture formation and spray characteristics are crucial for the advancement of Gasoline Compression Ignition (GCI) engine. For investigations of spray characteristics, a high-pressure high-temperature spray chamber with constant volume has been designed, tested and commissioned at CCRC, KAUST. Back light illumination technique has been applied to investigate the macroscopic spray properties of an outwardly opening piezoelec- tric injector. Three parameters including injection pressure, ambient pressure, and ambient temperature have been involved. A total of 18 combinations of experimental conditions were tested under non-reactive conditions. Through qualitative analysis of spray morphology under different operating conditions, an apparent distinction of spray morphology has been noticed. Spray morphology and propagation have shown strong dependencies on ambient pressure and ambient tempera- ture while injection pressure has a negligible effect on spray shape. Increasingly compact and bushier spray patterns were observed in the cases of high ambient pressure due to in- creasing aerodynamic drag force on spray boundary. It should also be noted that ambient temperature plays a fairly important role in fuel evaporation rate. At 200 °C, oscillating and considerably short spray shape was produced. Also, circumferential ring-like vortices and distinctive string-like structures have been identified for the fuel spray exiting this hollow cone injector. It has been observed that high ambient pressure conditions (Pamb = 4 bar and 10.5 bar) are favorable to the vortices generation, which has also been reported in previous literature. The quantitative description of macroscopic spray properties reveals that ambient pres- sure and ambient temperature are found to be the most influential parameters on liquid penetration length. The rise of ambient pressure results in considerably shorter liquid pen- etration length. Ambient temperature also appears to be a very effective factor of reducing penetration length. Injection pressure contributes to a notable increase of liquid penetra- tion length under ambient pressure of 1 atm. However, the influence of injection pressure is substantially reduced under ambient pressures of 4 bar and 10.5 bar, which indicates that ambient pressure exerts much stronger influence than injection pressure on liquid penetra- tion length. Furthermore, it has been revealed that the increase of injection pressure and ambient pressure are the predominant sources contributing to the enlargement of spray cone angle. The effect of injection pressure on spray cone angle has been amplified by the increase of ambient pressure. With increasing ambient pressure, the penetration of injected fuel tends to propagate axially in a much slower manner that leads to wider fuel distribution in the radial direction. Ambient temperature exerts a similar influence on spray cone angle as on liquid penetration length. The spray cone angle experiences a noticeable decline when ambient gas is increased to 200 °C.

”The Eagle has landed”. With this words, astronaut Neil Armstrong, together with astronaut Edwin ”Buzz” Aldrin, confirmed the safe landing on the Moon of the Apollo11 on July 20th, 1969. This achievement would have never been possible without the engineering behind the construction of the Moon lander. One of the most innovative features installed aboard was the pintle injector, a specific type of injector capable of precise metering of the propellants into the combustion chamber, and capable of throttling. Furthermore, the pintle injector has demonstrated its inherent combustion stability andgood mixing properties over time. The current work serves as a feasibility study for the use of an electric motor as the actuator for the pintle. This paper is the result of a 9-month internship at ArianeGroup GmbH, which is investigating the use of a pintle injector as a back-up option for a future ESA lunar lander mission. A preliminary design of the pintle was already produced, and the scope of this work is the design of the mechanical linkages and the actuation of the injector, with the choice of the method of actuation, the electric motor and the necessary components.