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This paper describes the design process and prototype development of a remotely controlled airship for wireless coverage. The airship is designed to be used as a platform to provide wireless coverage for rural areas. The design process follows a systematic design process for lighter-than-air vehicles, modified to impart slight heaviness to the vehicle. A remotely-controlled, thrust-vectored electric propulsion system offsets the slight vehicle heaviness. The electric propulsion system comprises two tilting rotors for takeoff, cruise, hovering, and horizontal manoeuvring. A rudder-less, rotor-less, cruciform fin design was implemented. A reduced-scale prototype of the airship was developed to prove the design concept. The airship prototype was successfully tested in an indoor environment.

Hybrid rockets provide compelling features for use in atmospheric and space rocket propulsion. One of the prominent applications of hybrid rockets which foster on its characteristics is the propulsion of micro air launch vehicles. In this paper, a set of design options of a hybrid rocket motor is evaluated for propulsion of micro air launch vehicles. In order to evaluate the various design options of a hybrid rocket, we developed design and performance simulation codes. A simulation code is based on a legacy interior ballistic model. MATLAB® environment was used to develop the design and performance analysis codes and to visualize the temporal variation of performance characteristics and grain geometry during burning. We employ the developed codes to assess the replacement of solid rocket motors which are typically used in Air Launch Vehicles by hybrid rocket motors. A typical Micro Air Launch Vehicle mission to launch a 20-kg payload into a 400-km circular polar orbit is assumed. The results show that a hybrid rocket is a suitable candidate for micro air launch vehicles. The performance is improved in terms of specific impulse and thrust with smaller size in the same mission. Several design parameters of hybrid rocket motors were also evaluated and analyzed, including different fuel port geometry, type of fuels and oxidizers, number of ports, nozzle design and initial mass flux. These design parameters bring a significant effect on hybrid rocket performance and size.

A general energy equation of quasi-one-dimensional heat flow in a longitudinal thermoelement (TE) of a curved side that is subjected to an electric field and convection heat transfer on the curved surface is developed. The energy equation is solved for the temperature distribution in two cases; uniform cross-section TE and non-uniform cross-section TE. Analytical solutions for a uniform cross-section TE with uniform electrical and thermophysical properties are obtained, whereas numerical solutions are provided for a non-uniform cross-section TE. Two parameters playing a vital role in the thermal performance of the TE are identified: the heat resistance ratio (HRR) and the energy growing ratio (EGR). The HRR represents the ratio of the longitudinal conduction maximum thermal resistance to the lateral convection maximum thermal resistance. The EGR represents the ratio of Joule’s electrical heating to Fourier’s heat conduction. The effects of varying these two parameters, as well as the TE geometry, have been thoroughly investigated.

This paper introduces and assesses the concept of the recently invented thermoelectrically controlled micronozzle (TECMN). A generalized quasi-one-dimensional model for gas flow, which is influenced by area variation and by wall heat transfer, is considered. In order to assess the merits of wall temperature control in micronozzles, the flow in the micronozzle is solved numerically for cases of convergent wall heating, divergent wall cooling, and a combination of both. Thermal efficiency and specific impulse are affected by heat exchange through the side wall of the micronozzle. By cooling the divergent section, kinetic energy increases, thus improving thermal efficiency. The mass flow rate is decreased in all cases that include convergent section heating, thereby enhancing specific impulse. The combination of convergent section heating with divergent part cooling results in significant performance enhancement in terms of thermal efficiency and specific impulse. To determine the TECMN wall temperature profile, we developed a one-dimensional general energy model for a thermoelement (TE) subject to an electric field as well as for heat convection on the lateral surface. The energy equation is analytically solved for constant properties and for Joule heating equivalent to heat convection. The temperature profile is then imposed on the quasi-one-dimensional flow model, which is solved numerically for various mass flow rates and exit wall temperature (cold junction). As the exit section wall temperature and mass flow rate decrease, the utilization of TEs to control the temperature of micronozzle walls considerably increases the Mach number at exit.

In this paper, we have used the differential evolution to optimize the design of a Micro Air Launch Vehicle and its launch trajectory. Since trajectory design of a launch vehicle requires prior knowledge of the masses and propulsion performance parameters of the Micro Air Launch Vehicle, whereas the vehicle design requires prior knowledge of the required velocity (ΔV) to insert the required payload into the target orbit, a two-step optimization cycle was adopted. A Micro Air Launch Vehicle was designed to launch a 20-kg payload into a 400-km circular polar orbit. The preliminary design of the Micro Air Launch Vehicle was conducted given the required ΔV, which was obtained from trajectory optimization, and then applied in mission analysis to obtain the initial masses. These initial masses were used in the vehicle design to get the performance and geometry parameters. The objective function of the Micro Air Launch Vehicle design optimization is to minimize the initial mass under specified constraints on the insertion orbit. The objective of trajectory optimization is to maximize the payload mass under constraints on orbit specifications and design variables. For the 20-kg payload mass, the optimal initial mass is 1267.8 kg and optimal payload is 20.6 kg, which slightly exceeds the mission requirements.

The demand for submicrosatellites is growing rapidly. A new low-cost launching method is needed to launch these types of satellites. This can be done by launching from airplanes. By implementing air launching, there would be no restrictions on the launch site, the launch angle, and the launch direction. In this paper, trajectory optimization of the micro air-launch vehicle (MALV) is carried out using the particle swarm optimization method. The problem is treated as a parameter optimization problem, and it is formulated as a single objective constraint optimization problem with the explicit objective of maximizing the payload mass. The simulation results show the effectiveness of the proposed technique in solving the nonlinear optimal trajectory problem for MALV.

In this paper, we draw attention to the importance of the lateral convection heat transfer effect on the operation of thermoelements with variable cross-sectional area. The significance of lateral heat convection arises from a new application, in which thermoelements form the walls of a MEMS-based convergent-divergent micronozzle in order to pump heat from the divergent part of the micronozzle to the convergent part to enhance overall performance. To assess the effect of thermoelement, we develop a quasi-one-dimensional model for thermoelements, in which, the physical phenomena of Peltier effect, Joule heating, Seebeck effect, longitudinal heat conduction, and lateral heat convection are considered. The general energy equation of the thermoelement with variable material properties is formulated with heat convection modeled as a lateral heat source. We used the model to study thermoelements with rectangular cross section and uniform thickness, but variable width. The width of the element is maximum at the location forming the micronozzle throat. Several geometries have been investigated; a piece-wise linear, parabolic and piece-wise sine wave. Two parameters which play important role in the thermal performance of thermoelement are identified. These are the thermal resistance ratio; ratio of longitudinal conduction resistance to lateral convection resistance, and heating ratio; ratio of Joule heating to Fourier conducted heat. The effects of varying these two parameters as well as thermoelement geometry have been investigated thoroughly and the results are presented in the form of charts to assist the design and material selection of the thermoelement.

A coordinated experimental and modeling study is carried out to investigate the crossover ion impingement of the accelerator grid for a seven-aperture gridlet. Simulations from a new three-dimensional global gridlet model reveal the differences in beamlet profile and accelerator-grid impingement pattern between the center aperture and an edge aperture on the accelerator grid at near-crossover operating conditions. It is shown that simulation predictions of the accelerator-grid impingement-current characteristics and the crossover limits agree well with those from measurements.

A new model is developed for three-dimensional global simulations of plasma flow in an entire subscale ion optics. This model explicitly includes apertures located near the edge of the grid surface and fully accounts for the effects of multiple ion beamlets and geometric asymmetry. This model is based on a new algorithm, the streamline hybrid-grid immersed-finite-element particle-in-cell. This algorithm is capable of achieving the same accuracy as an unstructured body-fit mesh-based particle-in-cell with a faster computational speed. Simulation results are presented to understand the plasma sheath upstream of the screen grid, direct impingement of beam ions, the crossover limit, the perveance limit, and the electron backstreaming onset.

A parallel three-dimensional electrostatic Particle-In-Cell (PIC) code is developed for large-scale simulations of ion thruster plume-spacecraft interactions on parallel supercomputers. This code is based on a newly developed immersed finite-element (IFE) PIC. The IFE-PIC is designed to handle complex boundary conditions accurately while maintaining the computational speed of the standard PIC code. Domain decomposition is used in both field solve and particle push to divide the computation among processors. A high-resolution simulation of multiple ion thruster plume interactions for a realistic spacecraft using a domain enclosing the entire solar array panel is carried out to demonstrate the capability of the code. A standard finite-difference PIC (FD-PIC) code is also parallelized for comparison. Both the IFE-PIC and FD-PIC run with similar overall speed, and the IFE-PIC achieves a high parallel efficiency of ges 90%

This paper presents a new algorithm for modeling spacecraft-plasma interactions: the hybrid grid immersed finite element particle-in-cell (HG-IFE-PIC) algorithm. This algorithm is extended from IFE-PIC and is designed to efficiently and accurately simulate the interactions between nonuniform plasmas and complex objects. In HG-IFE-PIC, the meshes used by the IFE field solver and PIC are decoupled, and the IFE solver uses a Cartesian-tetrahedral mesh that is stretched according to local potential gradient and plasma density. It is shown that the application of HG-IFE-PIC with a stretched IFE mesh can achieve approximately the same accuracy as IFE-PIC while significantly reducing the memory requirement and computation time required for large-scale PIC simulations of spacecraft-plasma interactions

This paper presents two immersed finite element (IFE) methods for solving the elliptic interface problem arising from electric field simulation in composite materials. The meshes used in these IFE methods can be independent of the interface geometry and position; therefore, if desired, a structured mesh such as a Cartesian mesh can be used in an IFE method to simulate 3-D electric field in a domain with non-trivial interfaces separating different materials. Numerical examples are provided to demonstrate that the accuracies of these IFE methods are comparable to the standard linear finite element method with unstructured body-fit mesh. Copyright © 2005 John Wiley & Sons, Ltd.

A hybrid rocket motor represents a compromise between a solid rocket motor and a liquid rocket motor in terms of its performance. In addition, hybrid rockets are featured by throttling capability, increased safety, moderate cost and benign environmental impact. However, low regression rate is a major drawback of hybrid rocket performance. Adding additives to the hybrid rocket fuel is one possible solution to this matter. To investigate the characteristics of hybrid rocket performance we develop a generic simulation algorithm based on a legacy interior ballistic model. MATLAB® environment was used to develop the design and performance analysis codes, and visualize the temporal variation of performance characteristics. The simulation algorithm is used to predict the performance of hybrid rocket using different types of fuels with varying metallic additive concentrations. To increase heat conduction at localized head, higher additives intensity is doped, giving adequate burning throughout the fuel. This paper also presents experimental results obtained from a laboratory scale hybrid rocket motor which employs paraffin wax fuel doped with metallic additives with varying concentrations along the hybrid rocket motor axis and gaseous oxygen as an oxidizer. Experiments are carried out to investigate how varying the additive concentration affects the regression rate and overall performance. Initial investigation reveals that varying the distribution of metallic additive concentration can improve the regression rate.

Many wind harvesters have a high cut-in speed which is not available in many locations over long periods of time. The average wind speed round the year at most locations is 3-5 m/s. A novel and inexpensive low wind speed harvester design is proposed and tested in this work, winds and artificial airflows with speeds as low as 1 m/s can be harvested to generate usable electric voltage which is fed into a power conditioning and storage circuit. A commercially available micropower step up booster, conditioning and storage circuit is used and the harvester’s ability to integrate is demonstrated. Voltage and power outputs for various wind speeds are studied at different resistive loads

The effect of the recently developed graphene nanoflakes (GNFs) on the polymerase chain reaction (PCR) has been investigated in this paper. The rationale behind the use of GNFs is their unique physical and thermal properties. Experiments show that GNFs can enhance the thermal conductivity of base fluids and results also revealed that GNFs are a potential enhancer of PCR efficiency; moreover, the PCR enhancements are strongly dependent on GNF concentration. It was found that GNFs yield DNA product equivalent to positive control with up to 65% reduction in the PCR cycles. It was also observed that the PCR yield is dependent on the GNF size, wherein the surface area increases and augments thermal conductivity. Computational fluid dynamics (CFD) simulations were performed to analyze the heat transfer through the PCR tube model in the presence and absence of GNFs. The results suggest that the superior thermal conductivity effect of GNFs may be the main cause of the PCR enhancement.

International audience; A detailed description of the vaporization of an isolated droplet has been carried out in this experimental study aimed at investigating ethanol and another aliphatic alcohol, 1-propanol. The characterization of the vaporization phenomenon is necessary for this liquid fuel to develop efficient design of injection systems for propulsion and power generation. Particularly, the vaporization rates and their dependency on temperature, important features for modeling and design, are explored for both ethanol and 1-propanol at intermediate to high temperatures. The experimental setup consists of a pressure chamber in which the furnace, the droplet formation, the droplet support, and motion devices are located. An alcohol droplet is located at the intersection of the cross quartz fiber (diameter of 14 µm) with a controlled initial diameter (range of 300–600 µm). Ambient temperature is varied from 298 to 973 K, at atmospheric pressure. The “quasi-steady” theory has been used to compare and to explain all experimental results. The results show that the d2 law is obeyed and an average vaporization rate is achieved in the case of 1-propanol vaporization. On the other hand, the real impact of the water concentration on the vaporization rate of an ethanol droplet in a large range of temperature is also examined, where two “quasi-steady” periods are observed on the d2 curves, clearly showing that the vaporization of an ethanol droplet is accompanied by the simultaneous condensation of water vapor on the droplet surface and thus the temporal evolution of the droplet squared diameter exhibits an unsteady behavior. The histories of the instantaneous vaporization rates calculated from the d2(t) curves of both 1-propanol and ethanol droplets confirm this phenomenon.

The study of the gasification of a droplet via vaporization, which involves heat, mass and momentum transfer processes in gas and liquid phases, and their coupling at the droplet interface, is necessary for better understanding and modeling of complex spray and mixture formation issues. A detailed description of the vaporization of an isolated droplet has been realized in this experimental study aimed at investigating the impact of the water vapor contained in the surrounding gas on the evaporation of an ethanol droplet. The experimental set-up consists of a heated chamber with a cross quartz fibers configuration as droplet support. An ethanol droplet is located at the intersection of the cross with a controlled initial diameter (300–550μm). Ambient temperature is varied from 350 to 850 K. The real impact of the water concentration on the vaporization rate of an ethanol droplet in a large range of temperature is examined, showing that the vaporization of an ethanol droplet is accompanied by the simultaneous condensation of water vapour on the droplet surface and thus the temporal evolution of the droplet squared diameter exhibits an unsteady behaviour. The histories of the instantaneous vaporisation rates calculated from the d2 (t) curves confirms this non-stationary aspect of the phenomenon.Copyright © 2011 by ASME

A coordinated experimental and modeling study is carried out to investigate ion optics accelerator grid impingement current and the cross-over limit using a 7-aperture gridlet. Simulations from a new three-dimensional global gridlet model reveal the difierences in beamlet proflle and accelerator grid impingement pattern between the center aperture and an edge aperture on the accelerator grid at low beamlet currents near cross-over conditions. It is shown that the simulation model correctly predicts the cross-over limit behavior and reproduces almost exactly the measured accelerator grid impingement current characteristics.

A parallel, three-dimensional electrostatic PIC code is developed for large-scale simulations of ion thruster plume spacecraft interactions on parallel supercomputers. This code is based on a newly developed immersed-flnite-element (IFE) PIC. The IFE-PIC is designed to handle complex boundary conditions accurately while maintaining the computational speed of the standard PIC code. Domain decomposition is used in both fleld solve and particle push to divide the computation among processors. A high-resolution simulation of multiple ion thruster plume interactions for a realistic spacecraft using a domain enclosing the entire solar array panel is carried out to demonstrate the capability of the code. A standard flnite difierence PIC (FD-PIC) code is also parallelized for comparison. Both the IFE-PIC and FD-PIC run with similar overall speed and the IFE-PIC achieves a high parallel e‐ciency of ‚ 90%.

A fully three-dimensional Hybrid-Grid Immersed-Finite-Element Particle-In-Cell (HGIFE-PIC) code has been developed for modelling of an entire subscale ion optics. The code applies a new meshing technique in which the particles are sampled on a uniform Cartesian mesh whereas the electrostatic potential is solved on a stretched Cartesianbased tetrahedral mesh. This meshing technique enhances the computational eciency so simulations may be performed to model an entire subscale ion optics and to resolve the eects of the grid apertures and geometric asymmetry. This paper presents detailed results of ion optics simulations and discusses the eects of aperture geometry and operating conditions on direct ion impingement and electron backstreaming.

A three dimensional ion optics simulation model is developed based on the recently developed hybrid-grid immersed-finite-element particle-in-cell (HG-IFE-PIC) algorithm. This algorithm uses two dierent meshes, a uniform Cartesian mesh for PIC and a stretched Cartesian-based tetrahedral mesh for the field solve. The algorithm is designed to handle the complex boundary condition accurately while maintaining the computational speed of a standard PIC code. Simulations are performed to study the plasma flow inside the ion optics.

A fully three dimensional ion optics simulation model is developed based on the recently developed immersed–finite–element particle–in–cell algorithm (IFE–PIC). The new model is called the Hybrid–Grid IFE–PIC. This model uses two different meshes for the IFE field solver and the PIC code. While the PIC mesh is a uniform Cartesian mesh, the IFE mesh is a stretched Cartesian-based tetrahedral mesh. This new meshing technique is used to enhance the computational efficiency of the IFE–PIC code. The HG–IFE–PIC code is applied to study the whole ion optics of a subscale ion optics gridlet. All simulations were performed on regular PCs in a reasonable computational time.

COLISEUM is a plasma simulation package for modeling electric plume interactions currently being developed by Air Force Research Lab, MIT, and Virginia Tech. One of the major components of COLISEUM is the DRACO code. DRACO, designed to perform firstprinciple based, high fidelity simulations of plume spacecraft interactions, include several simulation modules. As the purpose of DRACO is to simulate real engineering problems, DRACO reads in spacecraft configurations defined by commercial CAD tools. A unique feature of DRACO is that it incorporates the recently developed immersed finite element particle-in-cell (IFE-PIC) algorithm. This method allows one to use a Cartesian mesh to handle realistic spacecraft geometry without scarifying the accuracy in electric field solutions. The computational speed of an IFE-PIC simulation is about the same as that of standard PIC simulation. DRACO is cross platform and runs on Windows, Linux, and Unix. This paper presents an overview of the DRACO code and presents simulation results for simulation of CEX backflow in a vacuum tank as well as plume/spacecraft interaction in the presence of a charged plume shield. The Air Force Research Laboratory (AFRL) is sponsoring the development of a flexible, user-friendly, plasma computational package called COLISEUM. The core library of COLISEUM provides the rudimentary input/output support to several plasma simulation packages. The complexity of the simulation packages ranges from a simple ray-tracing algorith, through a prescribed plume model to several ES-PIC simulation modules. The DRACO module, being developed at Virginia Tech, is described in this paper. Additional information about COLISEUM and its simulation packages is available in Ref. 1-2. DRACO is a multi-purpose electro-static, particle-in-cell (ES-PIC) plasma simulation package. As shown in Fig. I, DRACO allows the user to choose from several Poisson solvers. The quasi-neutral solver obtains the potential by assuming the Boltzmann distribution for the electron density and a constant electron temperature. The quasi-neutral solver is intended for quick calculations and cannot be used to resolve the plasma sheath. The DADI solver uses a standard finite-dierence formulation to solve the electric field. It is designed for problems with relatively simple geometries. The Immersed Finite Element (IFE) is DRACO’s most sophisticated solver. IFE is based on a finite element formulation, and is designed to perform simulations accurately for problems involving complex geometric and material boundary conditions. Instead of using a complex body-fitted mesh, the IFE method uses a structured mesh without consideration of the object surface location. Thus the standard, Cartesian mesh based method for particle-mesh interpolations and pushing particles can be used even in simulations involving complex geometric boundaries. This allows DRACO to retain the computation speed of a standard PIC code. Many of DRACO s subroutines are based on 3-D plasma simulation codes previously developed by J. Wang to simulate ion thruster plume interactions 4 and ion optics plasma flow. 5 The legacy code produced results that were in excellent agreement with data from Deep Space 1 in-flight measurements and the long duration test of the NSTAR thruster.

Modeling and simulation are playing an ever more important role in space environments and effects research activities. In recent years, the sophistication of the models and the capability of state-of-the-art supercomputers have reached such a level that in many cases one can produce simulation results that are in good quantitative agreement with experimental data. For example, the 3-D ion thruster plume model described in Wang et a1.[2001] produced results that are in excellent agreement with data taken from Deep Space 1 in-flight measurements. The recent advance in simulation capabilities suggests that "virtual" experiments using first-principle based models may be used to replace real experiments to quantify spacecraft environment interactions for many applications.

A new technology, which uses thermoelectric elements as side-walls of microthrusters for heating and cooling purpose, is emerging. This technique can improve the performance of low-Reynolds-number microthrusters as a result of increasing the flow momentum forces or decreasing the viscous forces. In the present paper, we focus on the effect of using heated or cooled walls to control the properties of the flow through a micronozzle. Viscous compressible laminar flow is solved in the micronozzle. Different isothermal divergent-wall temperatures are tested to study the impact of wall temperature on the fundamental properties of momentum forces. The temperature difference between the wall and the gas effects the static temperature and static pressure profile, Mach number is increased, density near the wall is increased due to cooling. Alleviation of viscous losses by cooling the supersonic flow in the expander is demonstrated by the reduction of the thickness of the subsonic boundary layer.

Two thermoelements are formed as walls of a micronozzle to perform heating-cooling on a gas flowing between them. The model of heat transfer by conduction opposites to Peltier effect is built, including Joule heating, Seebeck effect and heat dissipation to the flowing gas. A general energy equation of one-dimensional heat flow in a TE subjected to electrical field and heat convection at the lateral side is developed and solved both analytically and numerically. The effects of varying the convection heat transfer coefficient, Joule heating and boundary conditions are tested for constant material properties using the analytical solution. Two parameters which play important roles in the thermal performance of TE are identified; heat resistance ratio and energy growing ratio. The effects of varying these two parameters as well as TE geometry have been investigated thoroughly, and the results are presented in the form of charts to assist the design and material selection of the TE.

In this paper, we investigate the effect of fuel magnetisation on the overall performance of a four-stroke Spark Ignition (SI) engine. To achieve this objective, we have designed a set of experiments using the Mitsubishi 1.5 L (4G15) SI engine. Each experiment is performed in two phases: with and without the fuel magnetisation. The collected data was analysed to assess the overall performance of the engine at several operating conditions. Our study shows that fuel magnetiser can enhance the overall performance of a typical SI engine. However, the enhancement greatly depends on the operating condition of the engine. Specifically, the best-observed performance enhancement in the tested engine owing to the usage of the fuel magnetiser was to reduce the Brake Specific Fuel Consumption (BSFC) by 9%, increase the Brake Power (BP) by 9% and boost the brake thermal efficiency (ηb) from 29% to 31%.

Proton exchange membrane (PEM) fuel cells are considered one of the best potential alternative power sources. It has both high efficiency and high power density. The air supply system dictates the performance of the fuel cell. It is responsible for supplying the correct amount of mass flow rate which is essential for ensuring efficient reaction of hydrogen and controlling the pressure inside the cathode. Pressure has a direct effect on the water balance characteristics and efficiency. In this work, a dynamic model for the air delivery system, including compressor and supply manifold, is developed. The model can capture both flow and inertia dynamics of the compressor. The model is tested by simulating the transient performance of the air supply system for a transportation-size fuel cell. A feedforward control method based on the compressor map is developed. Results show the success of the model in predicting the transient behaviour of the air supply system. The model can be used to implement and test different control strategies.

Claims are furnished in several patents; that swirling the intake air in SI engines can improve fuel economy and reduce environmental impact. In this paper, we investigate the effect of a free rotating air swirling device (FRASD) installed in the air intake hose on the overall performance and emission characteristics of an SI engine. FRASDs with three vane angles were tested; 6, 9 and 12 degrees. The baseline engine was tested without FRASD at selected loads. Then, the engine was tested at the same loads with each FRASD and results were compared with the baseline engine. Experiments show that all tested FRASDs exhibit some degree of enhancement in the overall performance and reduction in exhaust emissions. It was found that enhancement greatly depends on the engine operating condition in addition to the FRASD vane angle. Specifically, best enhancement in performance and highest reduction in emissions was observed with the 9-degrees which reduced specific fuel consumption by 12%, hydrocarbon (HC) emissions by 20% and carbon monoxide emissions by 12%. Suggestions are made to modify the FRASD design to magnify its impact on engine performance.

Modelling of vehicle fuel consumption and emissions has emerged as an effective tool to help develop and assess vehicle technologies and to help predict vehicle fuel consumption and emissions. A review to identify the current state-of-the-art on vehicle fuel consumption and emissions modelling is elucidated. This review categorises vehicle fuel consumption and emissions models into five classifications. The relevant main models to each of these classifications are presented. These models are then compared with regard to assumptions, limitations, merits, drawbacks, characteristic parameters, data collection techniques, accuracy, and relevance to road traffic. The study demonstrates that the trends of vehicle fuel consumption and emissions provided by current models generally do satisfactorily replicate field data trends. In addition, the paper demonstrates that mesoscopic models, empirical models, mean value-based models, and quasi dimensional models strike a balance between accuracy and simplicity and thus are very suitable for transportation and control applications. The study shows as well that no one model as yet fully meets the needs of transportation applications.

International audience; The gasification of a droplet via vaporization is one of the main processes in combustion systems, namely diesel and propulsion engines. In these combustion systems, always the liquid fuel is atomized as a cloud of droplets in the chamber, which then vaporizes, and mixes with the oxidant and burns to release heat. Therefore, to afford a better knowledge especially in modelling complex spray flows and mixture formation issues, the study of the droplet vaporization which involves mass, heat and momentum transfer processes is really vital. Alcohol has been chosen for this particular study due to its potential as an alternative fuel to the current conventional hydrocarbon fuel. However, viability of alcohols as alternate fuels has been limited by their high latent heat of vaporization and low heating value which can deliver difficulty in providing rapid gasification, mixing and ignition. Consequently, the objective of this study is to provide more data and understanding in alcohols vaporization behaviour. Methanol and ethanol have been studied extensively in terms of fundamental issues such as vaporization, in engine performances and pollutants formation. However, the potential is now extended and shifted on propanol, which has a better energy density and lower affinity with water than methanol and ethanol. A detailed description of the vaporization of an isolated droplet has been realized in this experimental study aimed at investigating another aliphatic alcohol, 1-propanol. This investigation extended our previous study on ethanol droplet vaporization to 1-propanol that is known as always less volatile, but holds higher boiling point than ethanol. The characterization of the vaporization phenomenon is necessary for this liquid fuel to develop efficient design of injection systems for propulsion and power generation. Particularly, the vaporization rates and their dependency on temperature, important features for modeling and design, are explored for 1-propanol for the first time at high temperatures. The experimental set-up consists of a pressure chamber in which the furnace, the droplet formation, the droplet support and motion devices are located. To minimize the influence of the droplet supporting system, a cross quartz fibers (14 μm) configuration has been used. A 1-propanol droplet is located at the intersection of the cross with a controlled initial diameter (400 – 600 μm). Ambient temperature is varied from 298 to 973 K, whereas the ambient pressure is maintained at atmospheric pressure. The temporal evolution of the droplet squared diameter of 1-propanol exhibits a quasi-steady behaviour. The result shows that the d2-law is apparently obeyed and a constant vaporization rate is achieved. The histories of the instantaneous vaporisation rates calculated from the d² (t) curves which are almost always a constant confirm this quasi stationary aspect of the phenomenon. However, as the ambient temperature increased beyond 673 K, the instantaneous vaporization rate decreases slightly during the droplet lifetime. It could be said that at higher temperatures, the vaporization of 1- propanol droplet show a slightly different behaviour.