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Electrification of aircraft is on track to be a future key design principal due to the increasing pressure on the aviation industry to significantly reduce harmful emissions by 2050 and the increased use of electrical equipment. This has led to an increased focus on the research and development of alternative power sources for aircraft, including fuel cells. These alternative power sources could either be used to provide propulsive power or as an Auxiliary Power Unit (APU). Previous studies have considered isolated design cases where a fuel cell system was tailored for their specific application. To accommodate for the large variation between aircraft, this study covers the design of an empirical model, which will be used to size a fuel cell system for any given aircraft based on basic design parameters. The model was constructed utilising aircraft categorisation, fuel cell sizing and balance of plant sub-models.

This paper reports on an investigation into the potential for a thermoelectric generator (TEG) to improve the fuel economy of a mild hybrid vehicle. A simulation model of a parallel hybrid vehicle equipped with a TEG in the exhaust system is presented. This model is made up by three sub-models: a parallel hybrid vehicle model, an exhaust model and a TEG model. The model is based on a quasi-static approach, which runs a fast and simple estimation of the fuel consumption and CO2 emissions. The model is validated against both experimental and published data. Using this model, the annual fuel saving, CO2 reduction and net present value (NPV) of the TEG’s life time fuel saving are all investigated. The model is also used as a flexible tool for analysis of the sensitivity of vehicle fuel consumption to the TEG design parameters. The analysis results give an effective basis for optimization of the TEG design.

The application of state-of-art thermoelectric generator (TEG) in automotive engine has potential to reduce more than 2% fuel consumption and hence the CO2 emissions. This figure is expected to be increased to 5%~10% in the near future when new thermoelectric material with higher properties is fabricated. However, in order to maximize the TEG output power, there are a few issues need to be considered in the design stage such as the number of modules, the connection of modules, the geometry of the thermoelectric module, the DC-DC converter circuit, the geometry of the heat exchanger especially the hot side heat exchanger etc. These issues can only be investigated via a proper TEG model. The authors introduced four ways of TEG modelling which in the increasing complexity order are MATLB function based model, MATLAB Simscape based Simulink model, GT-power TEG model and CFD STAR-CCM+ model. Both Simscape model and GT-Power model have intrinsic dynamic model performance.

Thermoelectric generator (TEG) has received more and more attention in its application in the harvesting of waste thermal energy in automotive engines. Even though the commercial Bismuth Telluride thermoelectric material only have 5% efficiency and 250°C hot side temperature limit, it is possible to generate peak 1kW electrical energy from a heavy-duty engine. If being equipped with 500W TEG, a passenger car has potential to save more than 2% fuel consumption and hence CO2 emission reduction. TEG has advantages of compact and motionless parts over other thermal harvest technologies such as Organic Rankine Cycle (ORC) and Turbo-Compound (TC). Intense research works are being carried on improving the thermal efficiency of the thermoelectric materials and increasing the hot side temperature limit. Future thermoelectric modules are expected to have 10% to 20% efficiency and over 500°C hot side temperature limit.

Natural gas as an alternative fuel offers the potential of clean combustion and emits relatively low CO2 emissions. The main constitute of natural gas is methane. Historically, the slow burning speed of methane has been a major concern for automotive applications. Literature on experimental methane-gasoline Dual Fuel (DF) studies on research engines showed that the DF strategy is improving methane combustion, leading to an enhanced initial establishment of burning speed even compared to that of gasoline. The mechanism of such an effect remains unclear. In the present study, pure methane (representing natural gas) and PRF95 (representing gasoline) were supplied to a constant volume combustion vessel to produce a DF air mixture. Methane was added to PRF95 in three different energy ratios 25%, 50% and 75%. Experiments have been conducted at equivalence ratios of 0.8, 1, 1.2, initial pressures of 2.5, 5 and 10 bar and a temperature of 373K.

A 2-stroke combustion cycle has higher power output densities compared to a 4-stroke cycle counterpart. The modern down-sized 4-stroke engine design can greatly benefit from this attribute of the 2-stroke cycle. By using appropriate variable valvetrain, boosting, and direct fuel injection systems, both cycles can be feasibly implemented on the same engine platform. In this research study, two valve strategies for achieving a two-stroke cycle in a four-stroke engine have been studied. The first strategy is based on balanced compression and expansion strokes, while the gas exchange is done through two different strokes. The second approach is a novel 2-stroke combustion strategy - here referred to as 2-stroke Miller - which maintains the expansion as achieved in a 4-stroke cycle but suppresses the gas exchange into the compression stroke.

Extensive research has been performed for on-board hydrogen generation, such as pyrolysis of metal hydrides (e.g., LiH, MgH₂), hydrogen storages in adsorption materials (e.g., carbon nanotubes and graphites), compressed hydrogen tanks and the hydrolysis of chemical hydrides. Among these methods, the hydrolysis of NaBH₄ has attracted great attention due to the high stability of its alkaline solution and the relatively high energy density, with further advantages such as moderate temperature range (from -5°C to 100°C) requirement, non-flammable, no side reactions or other volatile products, high purity H₂ output. The H₂ energy density contained by the system is fully depend on the solubility of the complicated solution contains reactant, product and the solution stabilizer. In this work, an approach based on thermodynamic equilibrium was proposed to model the relationship between the solubility of an electrolyte and temperature, and the effect of another component on its solubility.

New European emissions legislation (Euro5) specifies a limit for Particle Number (PN) emissions and therefore drives measurement of PN during vehicle development and homologation. Concurrently, the use of biofuel is increasing in the marketplace, and Euro5 specifies that reference fuel must contain a bio-derived portion. Work was carried out to test the effect of fuels containing different levels of Fatty Acid Methyl Ester (FAME) on particle number, size, mass and composition. Measurements were conducted with a Cambustion Differential Mobility Spectrometer (DMS) to time-resolve sub-micron particles (5-1000nm), and a Horiba Solid Particle Counting System (SPCS) providing PN data from a Euro5-compliant measurement system. To ensure the findings are relevant to the modern automotive business, testing was carried out on a Euro4 compliant passenger car fitted with a high-pressure common-rail diesel engine and using standard homologation procedures.

Homogenous Charge Compression Ignition (HCCI) combustion phasing and stability provides a challenging control problem over conventional combustion technologies of Spark Ignition (SI) and Compression Ignition (CI). Due to the auto ignition nature of the HCCI combustion there are no direct methods for actuation, the combustion and the phasing relies on indirect methods. This in itself creates a nonlinear dynamic problem between the relationships of control actuators and the combustion behavior. In order to control the process, an accurate feedback signal is necessary to determine the state of the actual combustion process. Ideally to ensure that combustion remains stable and phased correctly an in-cylinder feedback of each cylinder for multi cylinder engines would be preferable. Feedback has been seen in studies using piezoelectric pressure sensors for visually monitoring the pressure in the combustion chamber. This is expensive and requires redesign of the combustion chamber.

A multi-zone Controlled Auto Ignition (CAI) model for simulating the combustion and emissions has been developed and reported in this paper. The model takes into account the effects of the boundary layer, crevice volume, and blowby. In order to investigate the influences of in-cylinder inhomogeneity, the main cylinder chamber has been divided into multiple core zones with varying temperature and composition. Mass and energy transfer between neighbouring zones were modeled. A reduced chemical kinetic mechanism was implemented in each zone to simulate the CAI combustion chemistry and emission formation. An in-house code, the LUCKS (Loughborough University Chemical Kinetics Simulation), was employed to solve the coupled differential equations of the system. The model was validated against experimental results at various Internal Exhaust Gas Recirculation (IEGR) levels and was then used to analyze the thermal and chemical effect of the IEGR on the CAI combustion.

The Otto cycle delivers theoretical maximum thermal efficiency. The traditional design of internal combustion engines using a simple slide-crank mechanism gives no time for a constant volume combustion which significantly reduces the cycle efficiency. In this study, using a high torque, high bandwidth, permanent magnet electric drive system attached to the crankshaft, variable angular velocities of the engine crankshaft were implemented. The system enabled reductions in piston velocity around the top dead centre region to a fraction of its value at constant crankshaft angular velocity typical in conventional engines. A quasi-constant volume combustion has thus been successfully achieved, leading to improvements in engine fuel consumption and power output which are discussed in detail.

Hydrogen crossover and membrane hydration are significant issues for polymer electrolyte fuel cells (PEFC). Hydrogen crossover amounts to a quantity of unspent fuel, thereby reducing the fuel efficiency of the cell, but more significantly it also gives rise to the formation of hydrogen peroxide in the cathode catalyst layer which acts to irreversibly degenerate the polymer electrolyte. Membrane hydration not only strongly governs the performance of the cell, most noticeable through its effect on the ionic conductivity of the membrane, it also influences the onset and propagation of internal degradation and failure mechanisms that curtail the reliability and safety of PEFCs. This paper focuses on how hydrogen crossover and membrane hydration are affected by; (a) characteristic cell geometries, and (b) operating conditions relevant to automotive fuel cells.

Over the past few decades, Homogeneous Charge Compression Ignition (HCCI) or Controlled Auto-Ignition (CAI) if it is fuelled with gasoline type of fuels has shown its potential to overcome the limitations and environmental issue concerns of the Spark Ignition (SI) and Compression Ignition (CI) engines. However, controlling the ignition timing of a CAI engine over a wide range of speeds and loads is challenging. Combustion in CAI is affected by a number of factors; the local temperature, the local composition of the air/fuel mixture, time and to a lesser degree the pressure. The in-cylinder engine charge flow fields have significant influences on these factors, especially the local gas properties, which leads to the influences towards the CAI combustion. In this study, such influences were investigated using a Computational Fluid Dynamics (CFD) engine simulation package fitted with a real optical research engine geometry.

A qualitative FMEA study of Polymer Electrolyte Fuel Cell (PEFC) technology is established and presented in the current work through a literature survey of mechanisms that govern performance degradation and failure. The literature findings are translated into Fault Tree (FT) diagrams that depict how basic events can develop into performance degradation or failure in the context of the following top events; (1) activation losses; (2) mass transportation losses; (3) Ohmic losses; (4) efficiency losses and (5) catastrophic cell failure. Twenty-two identified faults and forty-seven frequent causes are translated into fifty-two basic events and a system of FTs with twenty-one reoccurring dominant mechanisms. The four most dominant mechanisms discussed that currently curtail sustained fuel cell performance relate to membrane durability, liquid water formation, flow-field design, and manufacturing practices.

A dual fuel engine is an internal combustion engine where the primary gaseous fuel source is pre-mixed with air as it enters the combustion chamber. This homogenous air fuel mixture is ignited by a small quantity of diesel known as the ‘pilot’ that is injected towards the end of the compression stroke. The diesel fuel ignites in the same way as in compression ignition (CI) engines, and the gaseous fuel is consumed by flame propagation in a similar manner to spark ignited engines. The motivation to dual-fuel a CI engine is partly economic due to the lower cost of the primary fuel, and partly environmental as some emissions characteristics are improved. In the present study, a direct injection four cylinder CI engine, typically used in genset applications, was fuelled with three different gaseous fuels; methane, propane and butane.

Methyl esters derived from vegetable oils by the process of transesterification (commonly referred as ‘biodiesel’), can be used as an alternative fuel in compression ignition engines. In this study, three different vegetable oils (rape, soy and waste oil) were used to produce biodiesel fuels that were then tested in a four cylinder direct injection engine, typically used in small diesel genset applications. Engine performance and emissions were recorded at five load conditions and at two different speeds. This paper presents the results obtained for measurements of NOx and smoke opacity at the different speed and load conditions for the three biodiesels, and their blends (5 and 50% v/v) with mineral diesel. A simple combustion analysis was also performed where ignition delay, position and magnitude of peak cylinder pressure and heat release rate were examined to asses how the variation of chemical structure and blend percentage affects engine performance.

The control of Homogeneous Charge Compression Ignition (HCCI) (also known as Controlled Auto Ignition (CAI)) has been a major research topic recently, since this type of combustion has the potential to be highly efficient and to produce low NOx and particulate matter emissions. Ion current has proven itself as a closed loop control feedback for SI engines. Based on previous work by the authors, ion current was acquired through HCCI operation too, with promising results. However, for best utilization of this feedback signal, advanced interpretation techniques such as artificial neural networks can be used. In this paper the use of these advanced techniques on experimental data is explored and discussed. The experiments are performed on a single cylinder cam-less (equipped with a Fully Variable Valve Timing (FVVT) system) research engine fueled with commercially available gasoline (95 ON).

Closed-loop electronic control is a proven and efficient way to optimize spark ignition engine performance and to control pollutant emissions. In-cylinder pressure sensors provide accurate information on the quality of combustion. The conductivity of combustion flames can alternatively be used as a measure of combustion quality through ion-current measurements. In this paper, combustion diagnostics through ion-current sensing are studied. A single cylinder research engine was used to investigate the effects of misfire, ignition timing, air to fuel ratio, compression ratio, speed and load on the ion-current signal. The ion-current signal was obtained via one, or both, of two additional, remote in-cylinder ion sensors (rather than by via the firing spark plug, as is usually the case). The ion-current signals obtained from a single remote sensor, and then the two remote sensors are compared.

Homogeneous charge compression ignition (HCCI), combustion has the potential to be highly efficient and to produce low NOx, carbon dioxide and particulate matter emissions, but experiences problems with cold start, running at idle and producing high power density. A solution to these is to operate the engine in a ‘hybrid mode’, where the engine operates in spark ignition mode at cold start, idle and high loads and HCCI mode elsewhere during the drive cycle, demanding a seamless transition between the two modes of combustion through spark assisted controlled auto ignition. Moreover; HCCI requires considerable control to maintain consistent start of combustion and heat release rate, which has thus far limited HCCI's practical application. In order to provide a suitable control method, a feedback signal is required.

The Homogeneous Charge Compression Ignition (HCCI) engine combustion uses heat energy from trapped exhaust gases enhanced by the piston compression heating to auto ignite a premixed air/gasoline mixture. As the HCCI combustion is controlled by the charge temperature, composition and pressure, it therefore, prevents the use of a direct control mechanism such as in the spark and diesel combustion. Using a large amount of trapped residual gas (TRG), is seen as one of the ways to achieve and control HCCI in a certain operating range. By varying the amount of TRG in the fresh air/fuel mixture (inside the cylinder), the charge mixture temperature, composition and pressure can be controlled and hence, the auto ignition timing and heat release rate. The controlled auto ignition (HCCI) engine concept has the potential to be highly efficient and to produce low NOx, carbon dioxide and particulate matter emissions.