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The aim of this paper is to compile the state of the art of engine control and develop scenarios for improvements in a number of applications of engine control where the pace of technology change is at its most marked. The first application is control of downsized engines with enhancement of combustion using direct injection, variable valve actuation and turbo charging. The second application is electrification of the powertrain with its impact on engine control. Various architectures are explored such as micro, mild, full hybrid and range extenders. The third application is exhaust gas after-treatment, with a focus on the trade-off between engine and after-treatment control. The fourth application is implementation of powertrain control systems, hardware, software, methods, and tools. The paper summarizes several examples where the performance depends on the availability of control systems for automotive applications.

Homogeneous charge compression ignition (HCCI) technology is promising to reduce engine exhaust emissions and fuel consumption in gasoline engine. However, it is still confronted with the problem of its limited operation range. High load is limited by the tradeoff between the quantity of working charge and dilution charge. Low load is limited by the high residual gas fraction and low temperature in the cylinder. One of the highlights of HCCI combustion research at present is to expand the low load limit of HCCI combustion by developing HCCI idle operation. The main obstacle in developing HCCI idle combustion is too high residual gas fraction and low temperature to misfire in cylinder. This paper relates to a method for achieving the appropriate environment for auto-ignition at idle and the optimal tradeoff between the combustion stability and fuel consumption by employing EIVO valve strategy with an equivalent air-fuel ratio.

Homogeneous charge compression ignition (HCCI) technology is promising to reduce engine exhaust emissions and fuel consumption. However, it is still confronted with the problem of its narrow operation range that covers only the light and medium loads. Therefore, to expand the operation range of HCCI, mode switching between HCCI combustion and transition SI combustion is necessary, which may bring additional problems to be resolved, including load fluctuation and increasing the complexity of control strategy, etc. In this paper, a continuously adjustable load strategy is proposed for gasoline engines. With the application of the strategy, engine load can be adjusted continuously by the in-cylinder residual gas fraction in the whole operation range. In this research, hybrid combustion is employed to bridge the gaps between HCCI and traditional SI and thus realize smooth transition between different load points.

Approximately 50% energy is consumed during the acceleration of a city bus. Fuel consumption during acceleration is significantly affected by driving behavior. In this study, 13 characteristic parameters were selected to describe driving style based on analysis of how driving influences fuel consumption during acceleration. The 100,000 km real-world vehicle running data of six drivers on three city buses in a particular bus line in Tianjin, China were sampled using a vehicle-on-line data logger. Based on the selected characteristic parameters and collected driving data, an evaluation model of the fuel consumption level of a driver was established by adopting the method of decision tree C4.5. For two-level classification, the model has over 85% prediction accuracy. The model also has the advantages of having a few training samples and strong generalization. As an example of the model application, the fuel-saving potential of a driver under optimal operations was analyzed.

A pressure accumulative injection rate controllable unit injector-PAIRCUI is proposed and developed. This unit injector is powered by fuel pressure accumulation controlled by an electronic control unit and its injection rate is shaped by inner valves of the injector. Inherent advantages of an accumulator type unit injector have been carried out in this new design, including sructural simplicity, totally flexible injection timing, medium common rail pressure, tolerable pump size and flow requirement. A number of decisive features have also been realized that are significant for high efficiency and low emissions of engine combustion, including higher mean effective injection pressure(MEIP), pilot injection capability and rapid end of injection. The injection pressure is independent of engine speed, but regulated upon engine load. These characteristics are beneficial in improving engine performance and fuel consumption.

The velocity and turbulence intensity profiles at exit of intake valve from typical SI engine intake ports (horizontal and sloping directed ports) were measured by hot wire anemometry (HWA) in a steady flow rig. The characteristics of velocity and turbulence intensity distribution under different valve lifts and at distances along valve axis were analysed and compared between above two intake ports. Results showed that velocity and turbulence intensity profiles are strongly dependent on intake port form,valve lift and surrounding geometry,they vary not only around valve head periphery but also along valve axis.

Based on 3- dimensional velocity data at intake valve exit area of typical SI engine intake ports (horizontal and sloping directed ports) measured by hot wire anemometry in a steady flow rig, the magnitudes and compositions of inflow angular momentum flux and swirl ratios at the end of induction process generated by each velocity component were computed at different intake valve lifts and distances along valve axis. A microscopic evaluation method was provided for evaluating intake port characteristics according to intake valve exit flow field.

The magnitudes and compositions of in-cylinder tumble ratio generated by each velocity components were computed at different intake valve lifts and distances along the direction of valve axis in this paper, based on the three-dimensional velocity data measured by hot-wire anemometry at intake valve periphery of typical SI engine intake ports (horizontal and sloping directed ports) in a steady flow rig. The effect of velocity profiles at above two intake ports exit on in-cylinder tumble generation was studied, and a microscopic analytical method of evaluating tumble-generating capability of intake ports was developed according to the velocity profiles at intake valve exit area.

It is found that a thin and rich mixture layer on a wall is formed after impingement of a gas jet of fuel on the wall. The measured thickness of the mixture layer is about 2 mm. and its dispersion rate after the end of injection is much lower, compared to that of a space gas jet. This phenomenon in a small D.I. diesel engine is known as “wall wetting” or “wall fuel accumulation” which has an important influence on engine fuel consumption and emissions. This paper presents a technique for enhancing the near wall mixing of an impinging jet by means of a bump on the wall. The development of a wall jet formed after an impingement of a gas jet has been investigated by simultaneously measuring the near wall velocity and concentration distribution. It has been found that a wall jet is stripped off the wall and ejected as a secondary jet when the wall jet encounters a bump of the wall.

To investigate the effects of fuel volatility on combustion and emissions in a diesel engine, a high-volatility fuel of n-heptane was blended into diesel fuel with different volumetric fractions (0%, 40%, 70%, 100%). A wide range of EGR rates from 0% to 65% were investigated, which covered both the conventional diesel combustion and low temperature combustion. Experiments under two engine load conditions, ∼5.2 bar and ∼10.5 bar gross IMEP were performed at 1500 rpm. The injection timing was fixed at 8°CA BTDC for all test cases. Results show that even if the ignition delay and combustion duration are nearly the same for all tested fuels, the premixed combustion fractions are increased for higher volatility fuels due to the improvement on mixing process during the ignition delay period. The indicated specific fuel consumption is decreased as using high-volatility fuels. The effect of fuel volatility on soot emissions depends on engine loads.

In order to minimize short-circuiting of the intake charge in the poppet-valved 2-stroke engine, measures are taken to generate reversed tumble in the cylinder. In this study, five different types of intake ports and three types of pent-roof geometries were designed and analysed of their ability to generate and maintain reversed tumble flows by means of CFD simulation for their intake processes on a steady flow rig. Their flow characteristics were then assessed and compared to that of the vertical top-entry ports. Results show that the side-entry port designs can achieve comparatively high tumble intensity. The addition of flow deflectors inside the side-entry ports does not have much effect on the reversed tumble ratio. The top-entry ports have the highest flow coefficient among all the intake ports examined as well as producing strong reversed tumble. It is also found that the pent-roof at a wider angle helps to strengthen the tumble intensity due to increased air flow rate.