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Computer programs that simulate the wave propagation phenomena involved in manifold tuning mechanisms are used extensively in the design and development of internal combustion engines. Most comprehensive engine simulation programs are based on the governing equations of one-dimensional gas flow as these provide a reasonable compromise between modelling accuracy and computational speed. The propagation of pressure waves through pipe junctions is, however, an intrinsically multi-dimensional phenomenon. The modelling of such junctions within a one-dimensional simulation represents a major challenge, since the geometry of the junction cannot be fully represented but can have a major influence on the flow. This paper introduces a new pressure-loss junction model which can mimic the directionality imposed by the angular relationship of the pipes forming a multi-pipe junction. A simple technique for estimating the pressure-loss data required by the model is also presented.

The paper discusses the use of alcohol fuels in high performance pressure-charged engines such as are typical of the type being developed under the ‘downsizing’ banner. To illustrate this it reports modifications to a supercharged high-speed sports car engine to run on an ethanol-based fuel (ethanol containing 15% gasoline by volume, or ‘E85’). The ability for engines to be able to run on alcohol fuels may become very important in the future from both a global warming viewpoint and that of security of energy supply. Additionally, low-carbon-number alcohol fuels such as ethanol and methanol are attractive alternative fuels because, unlike gaseous fuels, they can be stored relatively easily and the amount of energy that can be contained in the vehicle fuel tank is relatively high (although still less than when using gasoline).

In order to reduce the development time involved in optimising the combustion system and valve timing of the internal combustion engine, an electro-hydraulic valve actuation system has been developed. The effects of various combustion strategies, including asymmetrical valve events, on emissions and efficiency, together with their sensitivity to EGR and AFR were investigated. In addition, the influence of the cylinder head design on in-cylinder charge motion and combustion was investigated by correlating airflow, tumble and swirl data to the heat release data obtained during dynamometer testing.

Charge-coolers have a significant effect on the performance of turbocharged internal combustion engines. For a comprehensive simulation of internal combustion engines fitted with such devices it is important to model the whole of the manifold system. A wave-action model of a charge-cooler boundary is proposed, together with a methodology for predicting the heat transfer coefficient of the device. This approach enables the instantaneous effectiveness of the charge-cooler to be predicted as a function of the mass flow rate through the device.

High engine efficiency and low emissions on spark ignition engines can be achieved with a new camshaft profile switching device. This enables the use of two camshaft profiles for inlet and exhaust that can be switched independent of each other by any engine management input. This paper proposes the use of this device to give an excellent torque curve together with reduced emissions, by selecting from two discrete inlet and exhaust camshaft profiles and timings against engine parameters such as speed, load and temperature.

The future exploitation of global energy resources is currently being hotly debated by politicians and by sections of the scientific community but there is little guidance available in the engineering literature as to the full gamut of options or their viability with respect to fuelling the world's vehicles. In the automotive industry extensive research is being undertaken on the use of alternative fuels in internal combustion engines and on the development of alternative powerplants but often the long-term strategy and sustainability of the energy sources to produce these fuels is not clearly enunciated. The requirement to reduce CO2 emissions in the face of accelerating global warming scenarios and the depletion of fossil-fuel resources has led to the widespread assumption that some form of ‘hydrogen economy’ will prevail; this view is seldom justified or challenged.

The paper critiques proposals for de-carbonizing transport and offers a potential solution which may be attained by the gradual evolution of the current fleet of predominantly low-cost vehicles via the development of carbon-neutral liquid fuels. The closed-carbon cycles which are possible using such fuels offer the prospect of maintaining current levels of mobility with affordable transport whilst neutralizing the threat posed by the high predicted growth of greenhouse gas emissions from this sector. Approaches to de-carbonizing transport include electrification and the adoption of molecular hydrogen as an energy carrier. These two solutions result in very expensive vehicles for personal transport which mostly lie idle for 95% of their life time and are purchased with high-cost capital.

The engine of a high performance sports car has been converted to operation on E85, a high alcohol-blend fuel containing nominally 85% ethanol and 15% gasoline by volume. In addition to improving performance, the conversion resulted in significant improvement in full-load thermal efficiency versus operation on gasoline. This engine has been fitted in a test vehicle and made flex-fuel capable, a process which resulted in significant improvements in both vehicle performance and tailpipe CO2 when operating solely on ethanol blends, offering an environmentally-friendly approach to high performance motoring. The present paper describes some of the highlights of the development of the flex-fuel calibration to enable the demonstrator vehicle to operate on any mixture of 95 RON gasoline and E85 in the fuel tank. It also discusses how through detailed development, the vehicle has been made to comply with primary pollutant emissions legislation on any ethanol-gasoline mixture up to E85.

Ever increasing oil prices and emissions legislation have forced automobile manufacturers to investigate new methods and technologies to reduce fuel consumption in Spark Ignition (SI) engines. Two such technologies are Controlled Auto Ignition (CAI) and Cylinder Deactivation (CDA), both of which have the potential to decrease fuel consumption at light load. This paper presents synergies between running engines in CAI and CDA operation. A baseline simulation model of a production intent vehicle incorporating a four-cylinder engine was produced and correlated to measured test data. Experimental results of various CAI and CDA investigations have been projected onto the baseline simulation model and an analysis performed over the New European Drive Cycle (NEDC). It has been found that running an engine in CAI or CDA mode improves efficiency in explicit areas of the fuel map.

Five different fuels, including gasoline, commercial E85, pure methanol and two mixtures of gasoline, ethanol and methanol, (GEM), configured to a target stoichiometric air fuel ratio have been investigated in a fully-optically-accessed engine. The work investigated effects of injection duration, and performed spray imaging, thermodynamic analysis of the combustion and OH imaging, for two fixed engine conditions of 2.7 and 3.7 bar NMEP at 2000 rpm. The engine was operated with constant ignition timing for all fuels and both loads. One of the most important results from this study was the suitability of a single type of injector to handle all the fuels tested. There were differences observed in the spray morphology between the fuels, due to the different physical properties of the fuels. The energy utilisation measured in this study showed differences of up to 14% for the different GEM fuels whereas an earlier in-vehicle study had showed only 2 to 3%.

The paper presents the concept of ternary blends of gasoline, ethanol and methanol in which the stoichiometric air-fuel ratio (AFR) is controlled to be 9.7:1, the same as that of conventional ‘E85’ alcohol-based fuel. This makes them iso-stoichiometric. Such blends are termed ‘GEM’ after the first initial of the three components. Calculated data is presented showing how the volumetric energy density relationship between the three components in these blends changes as the stoichiometric AFR is held constant but ethanol content is varied. From this data it is contended that such GEM blends can be ‘drop-in’ alternatives to E85, because when an engine is operated on any of these blends the pulse widths of the fuel injectors would not change significantly, and so there will be no impact on the on-board diagnostics from the use of such blends in existing E85/gasoline flex-fuel vehicles.

The paper presents vehicle-based test work using tri-component, or ternary, blends of gasoline, ethanol and methanol for which the stoichiometric air-fuel ratio (AFR) was controlled to be 9.7:1. This is the same as that of conventional "E85" alcohol-based fuel. Such ternary blends are termed "GEM" after the first initial of the three components. The present work was a continuation of an earlier successful project which established that the blends were effectively invisible to a car using a virtual alcohol sensor. The vehicle used here employed the other major technology in flex-fuel vehicles to determine the proportion of alcohol fuel in the tank, a physical alcohol sensor. Another aspect of the present work included the desire to investigate ternary blend replacements for E85 having low ethanol concentrations. Evidence from the previous work suggested that under specific conditions, ethanol was required in some amount to act as a cosolvent for the gasoline and methanol in the blend.

Many new technologies are being developed to improve the fuel consumption of gasoline engines, including the combination of direct fuel injection with turbocharging in a so-called ‘downsizing’ approach. In such spark ignition engines operating on the Otto cycle, downsizing targets a shift in the operating map such that the engine is dethrottled to a greater extent during normal operation, thus reducing pumping losses and improving fuel consumption. However, even with direct injection, the need for turbine protection fuelling at high load in turbocharged engines - which is important for customer usage on faster European highways such as German Autobahns - brings a fuel consumption penalty over a naturally-aspirated engine in this mode of operation.

Iso-stoichiometric ternary blends - in which three-component blends of gasoline, ethanol and methanol are configured to the same stoichiometric air-fuel ratio as an equivalent binary ethanol-gasoline blend - can function as invisible "drop-in" fuels suitable for the existing E85/gasoline flex-fuel vehicle fleet. This has been demonstrated for the two principal means of detecting alcohol content in such vehicles, which are considered to be a virtual, or software-based, sensor, and a physical sensor in the fuel line. Furthermore when using such fuels the tailpipe CO₂ emissions are essentially identical to those found when the vehicle is operated on E85. Because of the fact that methanol can be made from a wider range of feed stocks than ethanol and at a cheaper price, these blends then provide opportunities to improve energy security, to reduce greenhouse gas emissions and to produce a fuel blend which could potentially be cheaper on a cost-per-unit-energy basis than gasoline or diesel.

Homogenous Charge Compression Ignition (HCCI) is an alternative to Spark Ignited (SI) combustion, which can provide part-load efficiencies as high as compression ignition engines and energy densities as high as SI engines, without high levels of NOx or Particulate Matter (PM). The principle of operation involves reaching the thermal oxidization barrier of a homogeneous air-fuel mixture. This combustion practice is enabled by diluting then compressing the mixture with the Trapped Residual Gases (TRG) to dilute the initial charge thus keeping combustion temperatures down. Introduction of exhaust gasses in the mixture can be achieved by the use of early exhaust valve closure and late inlet valve opening. The charge is well mixed avoiding particulate emissions, and by using exhaust gasses for load regulation the need for throttled operation is removed allowing the realization of high efficiencies, low pumping losses and a resulting 15 - 20% improvement in fuel economy.

The tumble flow in modern spark ignition engines is assuming an evermore important role for fuel guiding, air/fuel mixing and the generation of turbulence kinetic energy to enhance the combustion process. This paper describes results obtained with laser Doppler anemometry in multiple vertical planes in the cylinder of a motored, tumble flow engine and looks at the post processed data in terms of tumble ratios and mean and turbulence kinetic energies. The tumble results indicate very different flow fields in parallel planes lying in the main tumble direction, showing the complex nature of the flows in the cylinder. A simple method of integrating the tumble ratios from the different planes is suggested, leading to a tumble ratio more in line with those expected from an integrated method of measuring tumble, albeit these results are crank angle dependent. The tumble in a perpendicular plane shows unexpected asymmetries and values for the tumble.

Hybrid electric vehicles offer significant fuel economy benefits, because battery and fuel can be used as complementing energy sources. This paper presents the use of dynamic programming to find the optimal blend of power sources, leading to the lowest fuel consumption and the lowest level of harmful emissions. It is found that the optimal engine behavior differs substantially to an on-line adaptive control system previously designed for the Lotus Evora 414E. When analyzing the trade-off between emission and fuel consumption, CO and HC emissions show a traditional Pareto curve, whereas NOx emissions show a near linear relationship with a high penalty. These global optimization results are not directly applicable for online control, but they can guide the design of a more efficient hybrid control system.

Designers are under increasing pressure to provide powertrain systems which meet tougher market and legislative requirements for:- performance, emissions and economy reliability and durability noise and refinement To meet increasing competition, powertrain products need to be “fast to market and right first time”. This implies the evolution of existing technology, comprising multicylinder reciprocating engines and gear transmissions, drawing on a database of decades of powerplant design experience. It is with this background that CAE has proven engineering value supporting key areas of powertrain engineering to meet these technological challenges in a cost effective and timely manner. This paper follows the analytical engineering of a typical component, the exhaust system. Particular emphasis is given to the manifold and downpipe components which duct gas from the cylinder head to the catalyst.

The pressures on the Automotive Industry from both future legislation and customer requirements mean that major changes in Powertrain and Vehicle Systems matching will be needed. This paper reviews some possible future technologies and describes the process by which the often mutually exclusive total vehicle performance objectives can best be satisfied. In conclusion the paper includes a brief case study showing a proposed solution to a set of possible future vehicle performance and fuel economy objectives. The process is based on empirical data, experience and w-here appropriate, analytical techniques.

Recently [SAE 2001-01-0251], we reported for the first time on using a fully variable valve train (FVVT) to facilitate controlled auto-ignition (CAI) in 4-stroke gasoline engines, with a 23% reduction in fuel consumption and a reduction of up to 95% in emission levels. In this paper we look at the industry trends towards increased control over combustion related processes occurring in modern engines, which signaled the direction towards the CAI work, and review a range of valve train technologies available to meet these trends. Previous key work conducted by industry and academic researchers is also reviewed to establish a minimum specification requirement for the new fully variable valve train systems. The paper then describes two electro-hydraulic valve actuation systems capable of meeting these specifications, the first a research grade system used on single cylinder engines and the second a new production viable system that is aimed at bringing FVVT's to high volume production.