R.H. Thring

Alternative Fuels for Spark-Ignition Engines

Toward the end of this century the shortfall of supply below demand of the products of natural crude oil will become severe. Research is already well under way to provide alternative fuels for spark ignition engines which will be independent of natural crude oil. These include fuels from oil shales and tar sands, as well as synthetic fuels, alcohols, and gases; sources include coal, natural gas and biological origins. These fuels will cost two to three times as much in real terms as gasoline from oil does now, so an even stronger emphasis on fuel economy will be required. Most of these alternative fuels are more suited to the spark ignition engine than the compression-ignition engine, and this paper predicts that the changeover to them will cause an increase rather than a decrease in the market penetration of the spark ignition engine. It is concluded that the alternative fuel most likely to gain general acceptance is synthetic gasoline made from coal or natural gas, or in some areas from agricultural by-products.

Polymer electrolyte fuel cell transport mechanisms: a universal modelling framework from fundamental theory:

Abstract A mathematical multi-species modelling framework for polymer electrolyte fuel cells (PEFCs) is presented on the basis of fundamental molecular theory. Characteristically, the resulting general transport equation describes transport in concentrated solutions and also explicitly accommodates for multi-species electro-osmotic drag. The multi-species nature of the general transport equation allows for cross-interactions to be considered, rather than relying upon the superimposition of Ficks law to account for the transport of any secondary species in the membrane region such as hydrogen. The presented general transport equation is also used to derive the key transport equations used by the historically prominent PEFC models. Thus, this work bridges the gap that exists between the different modelling philosophies for membrane transport in the literature. The general transport equation is then used in the electrode and membrane regions of the PEFC with available membrane properties from the literature to compare simulated one-dimensional water content curves, which are compared with published data under isobaric and isothermal operating conditions. Previous work is used to determine the composition of the humidified air and fuel supply streams in the gas channels. Finally, the general transport equation is used to simulate the crossover of hydrogen across the membrane for different membrane thicknesses and current densities. The results show that at 353 K, 1 atm, and 1 A/cm2, the nominal membrane thickness for less than 5 mA/cm2equivalent crossover current density is 30 μm. At 3 atm and 353 K, the nominal membrane thickness for the same equivalent crossover current density is about 150 μm and increases further to 175 μm at 383 K with the same pressure. Thin membranes exhibit consistently higher crossover at all practical current densities compared with thicker membranes. At least a 50 per cent decrease in crossover is chieved at all practical current densities, when the membrane thickness is doubled from 50 to 100 μm.

Gasoline Engine Combustion—Turbulence and the Combustion Chamber

A research programme has been carried out to investigate the effects of operating gasoline engines with different combustion systems. The results showed that at high compression ratios (13:1) compact combustion chambers allowed an increase in compression ratio of between 1 and 2 one-half numbers for a given fuel quality compared to conventional designs. Fuel economy benefits of about 10% could be achieved by using high ratio compact chambers and lean operation.

A polymer electrolyte membrane fuel cell model with multi-species input

Abstract With the emerging realization that low temperature, low pressure polymer electrolyte membrane fuel cell (PEMFC) technologies can realistically serve for power-generation of any scale, the value of comprehensive simulation models becomes equally evident. Many models have been successfully developed over the last two decades. One of the fundamental limitations among these models is that up to only three constituent species have been considered in the dry pre-humidified anode and cathode inlet gases, namely oxygen and nitrogen for the cathode and hydrogen, carbon dioxide, and carbon monoxide for the anode. In order to extend the potential of theoretical study and to bring the simulation closer towards reality, in this research, a 1D steady-state, low temperature, isothermal, isobaric PEMFC model has been developed. The model accommodates multi-component diffusion in the porous electrodes and therefore offers the potential to further investigate the effects of contaminants such as carbon monoxide on cell performance. The simulated model polarizations agree well with published experimental data. It opens a wider scope to address the remaining limitations in the future with further developments.

The Effects of Varying Combustion Rate in Spark Ignited Engines

It has been shown by calculation that, for given engine operating conditions, there should be an optimum rate of combustion for minimum NOx emissions from spark ignited engines. This paper gives experimental results from a single cylinder engine which confirm the theory, and show that, for a particular engine, the normal combustion rate needed reducing at zero exhaust gas recirculation (EGR) and increasing at high EGR rates, in opposition to its natural tendency to decrease. The effect on economy was a small loss at zero EGR, but an appreciable improvement at high EGR. Cyclic variation and octane requirement studies are also included.

Engine Transmission Matching

This paper discusses ways of improving passenger car economy by better matching of the engine and transmission. Vehicle simulation showed that a reduction of 25% in fuel consumed is theoretically possible. Engine development showed that the results of valve timing changes were small, but the four valve cylinder head tested gave better economy than the two valve cylinder head over the whole engine operating range. It is recommended that two wide span transmissions be developed -- a six speed semiautomatic and an eight speed fully automatic.

Analysis of a 50 kWe indirect methanol proton exchange membrane fuel cell (PEMFC) system for transportation application

Abstract Steady state and dynamic models of proton exchange membrane fuel cell (PEMFC) or solid polymer fuel cell (SPFC) systems have been developed for transport and stationary applications. This paper reports the results of a steady state analysis of a methanol-fuelled PEMFC vehicle with a maximum (electrical) power output of 50 kW. The model incorporates a methanol steam reformer, gas clean-up unit, fuel cell stack, compressor, expander, battery pack, and heat exchangers as well as electrical power handling, motor, gearbox, and final drive. Results are given for the reformer as a function of steam-carbon ratio and reformer temperature. A degree of optimization of the system was conducted by (a) the addition of preheat to the reformer and burner reactants and (b) the addition of condensers for the fuel cell exhaust gases. The effect of operating pressure was also investigated. It was concluded that only by proper thermal integration could the target electrical system efficiency of better than 45 per cent at rated power be achieved.

Model Based Investigation of Liquid Water Injection Strategies for Evaporatively Cooled PEM Fuel Cells

Evaporative cooling through liquid water injection directly into the fuel cell flow channels removes the requirement for external humidification and liquid cooling channels within the stack. However, the amount of liquid water injected must be accurately controlled, to prevent on one hand membrane drying due to lack of water vapor and on the other hand flooding due to excessive liquid water.In this paper a one-dimensional, non-isothermal model of an evaporatively cooled proton exchange membrane fuel cell (PEMFC) is produced. The model accounts for changes in relative humidity and temperature along the anode and cathode flow channels, water transfer through the membrane and liquid accumulation within the gas diffusion layers. The model was used to study liquid water injection strategies at both cell and localized level. The influence of current density, operating pressure and inlet humidity were investigated. Results show that provided high humidity is maintained throughout the cell, exhaust gas temperature increase from low to high current densities (0.4–1.4A/cm2) is less than 4.0°C, without the need for active temperature control. Furthermore both temperature regulation and good membrane hydration can be managed by uniform injection of liquid water throughout the cell to maintain a target cathode exhaust humidity.Copyright

Energy economy analysis of the G-Wiz: a two-year case study based on two vehicles

This paper presents the data recorded from two G-Wiz Reva electric vehicles (EVs) over a period of two years and approximately 8000 km on each vehicle. The analysis of the vehicle data demonstrates that the range of the vehicle obtained for a certain state-of-charge (SOC) drop was not consistent. The results show that the main factor affecting the available range was irregular vehicle usage. The recharge energy consumption patterns of the vehicle were identified and it was demonstrated that infrequent vehicle usage increased energy consumed by the vehicle. A maximum range of 66.8 km was achieved when the vehicle was regularly used, but this fell to 42.8 km when it was infrequently used. The energy economy when the vehicle was regularly used was 8.3 km/kWh. Additionally, the analysis results identify the need to determine discharge rate of the vehicle batteries to determine the precise effects on the available range and energy consumption of the vehicle.

The Influence of Knowledge and Persuasion on the Decision to Adopt or Reject Alternative Fuel Vehicles

Alternative fuel vehicles, such as battery electric vehicles and hydrogen fuel cell vehicles, support the imperative to decarbonise the transport sector, but are not yet at a stage in their development where they can successfully compete with conventional fuel vehicles. This paper examines the influence of knowledge and persuasion on the decision to adopt or reject alternative fuel vehicles, a novel and original application of Rogers’ Theory of Diffusion of Innovations. A household questionnaire survey was undertaken with respondents in the Sutton Coldfield suburb of the United Kingdom city of Birmingham. This suburb was previously identified as having a strong spatial cluster of potential early adopters of alternative fuel vehicles. The survey results provide some useful empirical insights around the issues pertaining to the wider adoption of alternative fuel vehicles, even though the data is a bit dated as the survey was conducted in 2013. It is confirmed that respondents have limited knowledge of alternative fuel vehicles and perceptions have led to the development of negative attitudes towards them. The reasons largely relate to three problems: purchase price, limited range and poor infrastructure availability. Most respondents passively rejected alternative fuel vehicles, which confirms that a concerted effort is required to inform the general public about the benefits alternative fuel vehicles.