Modelling cycle to cycle variations in an SI engine with detailed chemical kinetics

This paper presents experimental results and a new computational model that investigate cycle to cycle variations (CCV) in a spark ignition (SI) engine. An established stochastic reactor model (SRM) previously used to examine homogeneous charge compression ignition (HCCI) combustion has been extended by spark initiation, flame propagation and flame termination sub-models in order to simulate combustion in SI engines. The model contains a detailed chemical mechanism but relatively short computation times are achieved. The flame front is assumed to be spherical and centred at the spark location, and a pent roof and piston bowl geometry are accounted for. The model is validated by simulating the pressure profile and emissions from an iso-octane fuelled single cylinder research engine that showed low CCV. The effects of key parameters are investigated. Experimental results that show cycle to cycle fluctuations in a four-cylinder naturally aspirated gasoline fuelled SI engine are presented. The model is then coupled with GT-Power, a one-dimensional engine simulation tool, which is used to simulate the breathing events during a multi-cycle simulation. This allows an investigation of the cyclic fluctuations in peak pressure. The source and magnitude of nitric oxide (NO) emissions produced by different cycles are then investigated. It was found that faster burning cycles result in increased NO emissions compared with cycles that have a slower rate of combustion and that more is produced in the early stages of combustion compared with later in the cycle. The majority of NO was produced via the thermal mechanism just after combustion begins.     

Trends of energy efficiency in Finnish road freight transport 1995–2009 and forecast to 2016

A framework for modeling and analyzing the energy efficiency of road freight transport is presented in this paper. This framework is tested by using the data from the Finnish Goods Transport by Road statistics. The data was enhanced by calculating the fuel consumption for each trip in the data. To calculate this, weight-fuel consumption functions were estimated for each Euro-class vehicles and road type. This is a new method for analyzing the energy efficiency of road freight transport and it could be applied also in other countries gathering freight transport data with continuous company surveys. The analysis show that the energy efficiency of road freight transport in Finland improved during 1995–2002, but has declined since. The major drivers in the development have been the changes in the level of empty running and vehicle fuel efficiency. Extrapolating current statistical trends of factors that influence the energy efficiency show that the target set by the Finnish government for improving energy efficiency by 9% until 2016 will not be achieved. However, the target is possible to be achieved by a combination of small changes to some determinants.     

Colloid-facilitated transport of cesium in variably saturated Hanford sediments

Radioactive 137Cs has leaked from underground waste tanks into the vadose zone at the Hanford Reservation in south-central Washington State. There is concern that 137Cs, currently located in the vadose zone, can reach the groundwater. In this study, we investigated whether, and to what extent, colloidal particles can facilitate the transport of 137Cs at Hanford. We used colloidal materials isolated from Hanford sediments. Transport experiments were conducted under variably saturated, steady-state flow conditions in repacked, 20 cm long Hanford sediment columns, with effective water saturations ranging from 0.2 to 1.0. Cesium, pre-associated with colloids, was stripped off during transport through the sediments. The higher the flow rates, the less Cs was stripped off, indicating in part that Cs desorption from carrying colloids was a residence-time-dependent process. Depending on the flow rate, up to 70% of the initially sorbed Cs desorbed from colloidal carriers and was captured in the stationary sediments. Less Cs was stripped off colloids under unsaturated than under saturated flow conditions at similar flow rates. This phenomenon was likely due to the reduced availability of sorption sites for Cs on the sediments as the water content decreased and water flow was divided between mobile and immobile regions.     

Thermomechanical treatments on high strength Al-Zn-Mg(-Cu) alloys

An investigation was carried out to determine the metallurgical properties of Al-Zn-Mg and Al-Zn-Mg-Cu alloy products processed according to newly developed Final Thermomechanical Treatments (FTMT) of T-AHA type. The results show that these cycles can be utilized to produce wrought products of high purity Al-Zn-Mg(-Cu) alloys characterized by equivalent toughness and ductility and much higher strength than conventionally processed commercial purity materials. Based on transmission electron microscopy studies, it was found that such improved behavior of FTMT material is attributable to the superposition of hardening effects, from aging precipitation and from dislocations. Preliminary stress-corrosion and fatigue tests indicate that these properties are not substantially influenced by T-AHA thermomechanical process. Further work is needed in this area, in order to better understand the directions to follow for developing better alloys.     

Future European gas supply in the resource triangle of the Former Soviet Union,the Middle East and Northern Africa

A steady increase of natural gas demand can be observed in Europe over the last decades. Due to the European obligation to reduce greenhouse gas emissions in the framework of the Kyoto Protocol, the trend toward natural gas is expected to continue in the future. The increased consumption is faced by comparably low indigenous gas resources within Europe, so that the dependency of Europe on gas imports from abroad will rise in the future. In addition to the existing supply sources Russia and Algeria, gas resources from the Middle East and the Caspian and the Central Asian regions may be supply options to cover Europe's gas demand in the future. Against this background, possible natural gas supply options as well as the transport infrastructure to and within Europe are discussed regarding their technical capacity and their costs. With the help of a cost-minimization model of the European gas supply system, the gas flows and the infrastructure capacity development up to the year 2030 are analyzed. In a sensitivity analysis, the impacts of demand variations on the choice of supply sources are studied.     

The application of parabolic trough technology under Jordanian climate

Parabolic trough solar thermal power plants are a proven technology in the utility scale since mid of the eighties. Between 1984 and 1991 nine power plants with an overall capacity of 354 MW have been installed in the Mojave Desert in California. Since, these power plants can be equipped with a thermal storage or a fossil back-up they offer a fully dispatchable electricity generation capacity. This technology will be a very interesting near term option for countries with high solar irradiation levels and small resources of fossil fuels like Jordan.This paper, discusses the use of parabolic trough solar thermal power plants for electricity production under Jordanian climate for two different sites (Amman, and Ma'an). An analysis of the daily power output, direct normal irradiation and the efficiency for the two sites has been carried out. The results showed that Ma'an site would be preferred than Amman site, so that it is recommended to erect the Parabolic Trough Concentrator (PTC) plant in the southern region of Jordan.Also this study aims to encourage the Jordanian government and the private sector to implement the solar thermal power plants for future expansion of power sector due to the increasing electricity demand and environmental degradation.     

Net employment effects of an extension of renewable-energy systems in the Federal Republic of Germany

Renewable-energy potential exists in the Federal Republic of Germany to a great extent, but it is barely used as yet. A change in the power-supply structure seems to be too risky with regard to finance and the sensitive labour market. Nevertheless, an extension of renewable energy systems in the German state North-Rhine Westphalia would lead to improved employment prospects.     

CuIn(Ga)Se2-based devices via a novel absorber formation process

A novel pathway for the formation of copper–indium (gallium) diselenide has been developed. This two-stage process consists of (a) the formation of Cu–In–(Ga)–Se precursors, and (b) subsequent thermal treatment to form CuIn(Ga)Se₂. The morphology, structure and growth mechanism for several different precursor structures prepared under various conditions were studied and correlated to the deposition parameters as well as the structure and morphology of the annealed films. Photovoltaic devices prepared from CuInSe₂ and CuIn_0.75Ga_0.25Se₂ resulted in efficiencies of 10% and 13%, respectively.