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In order to achieve the required future CO2 reduction targets, significant further development of both gasoline and diesel engines is required. One of the main methods to achieve this with the gasoline engine in the short to medium term is through the application of engine downsizing, which has resulted in numerous downsized engines already being brought to production. It is, however, considered that there is still significant further CO2 reduction potential through continued development of this technology. This paper considers the future development of gasoline engine downsizing in the short to medium term and the various technologies that can be applied to further increase the efficiency of operation. As such this paper covers, among other areas, fundamental engine layout and design, alternative boosting systems, methods of increasing part load efficiency and vehicle modelling, and uses analysis tools and engine test results to show the benefits achievable.

The HAJI (Hydrogen Assisted Jet Ignition) system for S.I. engines utilises direct injection of small amounts of hydrogen to enhance the combustion of a variety of automotive fuels. Although not the primary purpose of HAJI, the hardware, once in place, also lends itself to the possibility of hydrogen-only running during a cold start. Cold-start simulations have been performed using a single cylinder engine. Results are presented, comparing hydrogen-only tests with standard HAJI operation and normal spark-ignition operation. HAJI and spark ignition tests were carried out with gasoline as the main-chamber fuel. Emission levels and combustion stability characteristics were recorded as the engine warmed up. The differences between the various fueling/ignition scenarios are presented and the implications for possible automotive applications are discussed in light of current and proposed emissions legislation.

HAJI (Hydrogen Assisted Jet Ignition) is an advanced combustion initiation system for otherwise standard S.I engines. It utilises the fluid mechanics of a turbulent, chemically active jet, combined with the reliability of spark igniting rich hydrogen mixtures. The result is an extremely robust ignition system, capable of developing power from an engine charged with air-fuel mixtures as lean as λ = 5. Experiments have been performed using a single cylinder engine operating on gasoline in the speed range of 600-1800 r/min. Data are presented in the form of maps which describe fuel efficiency, combustion stability and emissions with respect to load, speed, air-fuel ratio and throttle. The results are incorporated into a model of a known engine and vehicle and this is used to estimate performance over the Federal drive-cycle.

The hydrogen assisted jet ignition system (HAJI) replaces the spark plug of an Otto cycle engine and consists of a very small pre-chamber into which a hydrogen injector and spark plug are installed. The HAJI system allows stable combustion of very lean main-chamber hydrocarbon mixtures, leading to improved thermal efficiency and very much reduced NOx emissions. The current investigation focuses on the application of HAJI to a modern pent-roof, four valve per cylinder automotive engine. The development of a new hydrogen injection system and HAJI pre-chamber based on proprietary gasoline and diesel injectors is described. Results from injector and engine performance testing are presented in detail.

Emissions optimization, particularly for complex engines, relies on developing mathematical correlations or ‘Response Surface Models’ of engine outputs. There is a clear tradeoff between the complexity of the model and its usefulness for a range of optimization tasks. Several current SI engine management systems use a ‘Spark efficiency curve’ to elegantly describe the response of engine torque to spark advance using a prescribed characteristic line that is fitted to a spark sweep with only two degrees of freedom. This provides a powerful method of data reduction. A similar technique has been developed to characterize engine emissions data. A single efficiency curve with only two degrees of freedom can be used to accurately describe the response of, say, hydrocarbon emissions to spark over a wide range of engines and operating conditions. The technique offers similar data reduction advantages for engine management system developers and those optimizing engines using high DoF models.

Lean burn and EGR are two commonly used technologies for improving fuel consumption and controlling emissions. Each has advantages and disadvantages when applied to an engine and, qualitatively at least, these effects are well known. To meet future emissions and fuel consumption constraints, most production engines are likely to use one or the other. This paper describes testing undertaken to quantify the opportunities that each strategy offers on a production engine. The engine used in this test program was a modern, four valve per cylinder l-4, with high charge activity features including one high swirl port per pair and one straight port with a deactivation plate. This engine is designed to operate with mixtures as lean as 24:1 during normal operation. It was tested at a number of part load operating conditions typical of an emissions drive-cycle over a range of air-fuel ratios.

This paper describes the initial development of a 3 cylinder 1.2l technology demonstrator engine from MAHLE. The purpose of this highly turbocharged direct injection engine is to demonstrate production-ready technologies that enable low CO2 emissions via downsizing by 50%. Downsizing is one of the most proven paths to CO2 emission reduction. By using careful design, a 2.4 l engine can be replaced by a 1.2l engine that has superior torque at all speeds and on-road fuel consumption benefits of 25 - 30%. A two-stage turbocharging system has been developed for the engine to enable good transient response and the high torque levels at all engine speeds demanded by a downsizing approach. Several options were tested and the final system exceeds the 30bar peak BMEP target with stoichiometric fuelling. Indeed, lambda = 1.0 fuelling is maintained over the majority of the full-load line and the 144kW peak power requirement is fulfilled at only 6000 rpm.