Petros Lappas

External characteristics of unsteady spray atomization from a nasal spray device

The nasal route presents an enormous opportunity to exploit the highly vascularized respiratory airway for systemic drug delivery to provide more rapid onset of therapy and reduced drug degradation compared with conventional oral routes. The dynamics of atomization at low injection pressure is less known as typical spray atomization studies have focused on industrial applications such as fuel injection that are performed at much higher pressure. An experimental test station was designed in house and an alternative method to characterize the external spray is presented. This involved the use of high-speed camera to capture the temporal development of the spray as it is atomized through actuation of the spray device. An image-processing technique based on edge detection was developed to automate processing through the large number of images captured. The results showed that there are three main phases of spray development (prestable, stable, and poststable) that can be correlated by examining the spray width. A comparison with a human nasal cavity is made to put into perspective the dimensions and geometry that the spray atomization produces. This study aimed to extend the current existing set of data to contribute toward a better understanding in nasal spray drug delivery.

CNG Fueling Strategies for Commercial Vehicles Engines-A Literature Review

The paper presents a survey of the opportunities to convert compression ignition heavy duty truck engines to work on single or dual fuel modes with CNG. In one popular option, the compression ignition engine is converted to spark ignition with throttle load control and port injection of the CNG. In another option of increasing popularity, the LNG is directly injected and ignited by direct injection of pilot Diesel. This latter option with direct injection of natural gas and diesel through separate injectors that are fully independent in their operation is determined to be the most promising, as it is expected to deliver better power density and similar part load fuel economy to Diesel.

Natural-Gas Direct-Injection for Spark-Ignition Engines - A Review on Late-Injection Studies

Significant research has been made on traditional pre-mixed charge Spark-Ignition Natural-Gas engines which have seen widespread usage across the automotive sector. Many researchers including those in industry are now exploring the Direct-Injection concept for Natural-Gas Spark-Ignition engines. Direct-Injection has significant performance benefits over port-fuel injection, primarily due to increased volumetric efficiency as a result of injecting the fuel after intake valve closure. This could lead to enhanced driving performance over port-fuel injection comparable to gasoline engines. Furthermore, Direct-Injection with increased compression ratio in conjunction with downsizing concepts has the potential to increase thermal efficiency while exhibiting significantly lower CO2 emissions. Advanced combustion strategies like stratified mixture combustion has been widely studied for gasoline and proven to increase the low load thermal efficiency over homogeneous stoichiometric combustion. If successfully implemented, similar benefits can be expected with Natural-Gas as well. However, currently there is no Direct-Injection Natural-Gas vehicle in production and there are gaps in the literature as research in this area is relatively new. Mixture formation, ignition and combustion processes are not fully understood. Nevertheless, attempts have been made to explore the potential of stratified combustion. This paper provides a comprehensive literature review on such studies and highlights the challenges involved in developing such combustion systems.

Reducing Automobile CO2 Emissions with an Exhaust Heat Recovery System Utilising Thermoelectric Generators and Heat Pipes

Exhaust heat recovery systems are used to make use of otherwise wasted heat from a car engine. The purpose of exhaust heat recovery systems is to reduce the fuel consumption of the car and consequently reduce CO2 emissions. The unique system design described herein utilises thermoelectric generators (TEGs) and heat pipes with its key advantage being it is a passive solid state design. The use of these components creates a few design constraints. For example, both the TEGs and heat pipes have operating temperature limitations. In this paper, a naphthalene heat pipe preheat exchanger is proposed to deal with this problem. Exhaust conditions measured from a representative spark ignition engine were used in a numerical simulation to predict the performance of the exhaust heat recovery system. If 8 modules are used and the engine is producing 8kW of mechanical power, the system is predicted to produce 53.75W of electrical power. The calculated reduction of CO2 emissions is 1.125% under these conditions. If fewer modules are used, less power is produced but the cost per watt decreases.

Flow Characteristics of Compressed Natural Gas Delivery for Direct Injection Spark Ignition Engines

High pressure ratio (PR) compressed natural gas (CNG) jets are studied using optical diagnostics under quiescent but realistic spark-ignited (SI) engine conditions. CNG jets were issued impulsively from a bespoke direct injector. Observations into the delivery characteristics for a large pressure ratio (PR) range were carried out (8.3<PR<400). Non-dimensional scaling laws show that the penetration rate can be represented by a single relationship. The penetration rate is the primary determinant of fuel targeting. Additionally, the jet growth rate and spread angle are also presented. The evolution of the transient underexpanded jet features: the barrel length and Mach disc diameter are detailed and a strong dependency on the injector needle-lift is shown. These nearfield compressible features are recognised as flow structures which influence the mixing rate of a free jet and are also shown to control the size of the incompressible regions. The highly dynamic jet features are captured with high-fidelity schlieren high-speed video. Particle image velocimetry (PIV) maps taken at multiple after start of injection (aSOI) instances detail the flow characteristics within the jet core and the ambient regions. Using the jet core centerline velocity, the Mach disc location (barrel length) is measured to within 7% of schlieren measurements. PIV measurements acquired at late injection (timing) conditions reveal detail on the influence of fuel delivery on the flow within the ignition zone. The mean flow velocity and kinetic energy are consequences of the jets proximity to the ignition region with influences largely originating from the encroaching shear-layer and/or the rolling vortex.

Assessment of the Viability of Vegetable Oil Based Fuels

This paper provides results of extensive trials using a 50/50 blend of unheated vegetable oil and diesel fuel in an unmodified vehicle on roads in Victoria, Australia. The work was inspired by the success of an on-road trial using 100 % waste vegetable oil in 2004 and positive indications in the literature. As well as being a sustainable alternative fuel, vegetable oil has the added safety advantage of having a much higher flash point than any other. Constant routes were used analogous in-part, to using prescribed drive cycles. Results were logged and bar-charts comparing fuel consumption for various fuel blends are presented. There was no clearly discernible difference (within the uncertainty of the measured data) in fuel consumption between the 50/50 blend and diesel fuel.

Engine heat sink thermal energy recovery system

Abstract This research report presents results in the investigation on the combustion engine thermal energy recovery systems (TERS)1−10, with the application of thermoelectric generators (TEG). Joint RMIT University and Defence Science Institute (DSI) research and development project is concentrated on examining thermal heat flux recovery from automotive heat sinks and converting it to the electrical power. One of the TERS systems’ research objectives is to create a sustainable electrical power source by redesigning parts of the combustion engine cooling system so that TEGs could be implemented. Extensive simulations were conducted to explore heat transfer and temperature distribution and ensure that engine working conditions are not changed. The whole system should be capable to store recovered energy and later use it by hybrid vehicle, in the electrical vehicle driving mode (EV)11, or should be used by other subsystems in the vehicle. Our investigation should give contribution to the reduction in the use of fossil fuels, CO2 emission and fuel consumption.

Air Entrainment in Gaseous Fuel Jets Using Particle Image Velocimetry and High Speed Schlieren Photography in a Constant Volume Chamber

The air entrainment process of a compressed natural gas transient fuel jet was investigated in a constant-volume chamber using Schlieren and particle image velocimetry (PIV) techniques. A new method of calculating air entrainment around a gaseous fuel jet is proposed using Schlieren and PIV imaging techniques. This method offers an alternative to calculation of an alternative to calculation of entrainment using LIF technique in gaseous fuel jets. Several Jet-ambient pressure ratios were tested. In each test, nitrogen was used to fill the chamber as an air surrogate before the jet of natural gas was injected. Schlieren high speed videography and PIV experiments were performed at the same conditions. Schlieren mask images were used to accurately identify the jet boundary which was then superimposed onto a PIV image. Vectors adjacent to the Schlieren mask in the PIV image were used to calculate the spatial distribution of the air entrainment at the jet boundary. The effects of ambient density and injection pressure on the air entrainment and contour shape at various parts of the jet are investigated. Results indicate that increase in injection pressure increases the entrainment around the jet. At the same time it was found that ambient density also has a similar relation on entrainment. The air entrainment distribution in gaseous fuel jets was found to be highly sensitive to the jet boundary definition, highlighting the importance of accurately defining the jet boundary.

Delivery Evaluation of High Pressure Natural Gas Fuel Injection

Schlieren high speed videography was employed to ascertain the geometric properties, compressible flow behaviour and the flow field of Compressed Natural Gas (CNG) jets. Axial and radial penetration, velocity, and dispersion have been studied comparatively. Schlieren high speed imaging reveals the dynamic flow behaviour of the delivery event, namely barrel Mach disc formation and mixing at the shear layer alongside other geometrical features; spreading rate, self-similarity, velocity and penetration. New findings of high-pressure gaseous fuel delivery are presented based on observations in a constant-volume chamber that replicates engine conditions. A novel analysis method for characterising structural dynamic properties of the gas jet are also presented alongside a new delivery method.

Assessment of the viability of vegetable oil fuels - species, land, social, environmental, population and safety considerations

This work follows the literature review and on-road trial findings presented at ICSAT 2013 (Thomas et al. Assessment of the viability of vegetable oil based fuels. In: Lecture notes in mobility—sustainable automotive technologies 2013, 2013). In addition, it addresses the availability of non-food oil-producing species and land, the sociological and environmental aspects associated with growing biofuels and the potential increased safety of using vegetable oil fuels and blends. The author claims that it is essentially impossible to provide the world’s current energy needs without fossil fuels unless humanity is prepared to control its population to a sustainable level. Production methods and costings are not addressed as intended and will be the subject of further study. Costs of growing, extracting, purifying and transporting vegetable oil fuel are lower than any alternatives given the simplicity of processes involved, the fact that almost anyone can perform them and the fact that the fuel can be grown and processed close to point of use by small, non-monopolistic enterprises. Readers wishing to consider costings are referred to reports by the EC Joint Research Commission and the International Energy Agency (IEA) (Production costs of alternative transportation fuels—influence of crude oil price and technology maturity; International Energy Agency; Jensen, Unmodified vegetable oil as an automotive fuel; the institute for prospective technological studies of the European commission directorate general joint research centre).