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In order to extend the CAI operation range in 4-stroke mode and maximize the benefit of low fuel consumption and emissions in CAI mode, 2-stroke CAI combustion is revived operating in a GDI engine with poppet valves, where the conventional crankcase scavenging is replaced by boosted scavenging. The CAI combustion is achieved through the inherence of the 2-Stroke operation, which is retaining residual gas. A set of flexible hydraulic valve train was installed on the engine to vary the residual gas fraction under the boosting condition. The effects of spark timing, intake pressure and short-circuiting on 2-stroke CAI combustion and its emissions are investigated and discussed in this paper. Results show the engine could be controlled to achieve CAI operation over a wide range of engine speed and load in the 2-stroke mode because of the flexibility of the electro-hydraulic valvetrain system. Presenter Yan Zhang, Brunel University

In order to extend the CAI operation range in 4-stroke mode and maximize the benefit of low fuel consumption and emissions in CAI mode, 2-stroke CAI combustion is revived operating in a GDI engine with poppet valves, where the conventional crankcase scavenging is replaced by boosted scavenging. The CAI combustion is achieved through the inherence of the 2-Stroke operation, which is retaining residual gas. A set of flexible hydraulic valve train was installed on the engine to vary the residual gas fraction under the boosting condition. The effects of spark timing, intake pressure and short-circuiting on 2-stroke CAI combustion and its emissions are investigated and discussed in this paper. Results show the engine could be controlled to achieve CAI operation over a wide range of engine speed and load in the 2-stroke mode because of the flexibility of the electro-hydraulic valvetrain system.

Controlled Auto Ignition (CAI), also known as Homogeneous Charge Compression Ignition (HCCI), is one of the most promising combustion technologies to reduce the fuel consumption and NOx emissions. Currently, CAI combustion is constrained at part load operation conditions because of misfire at low load and knocking combustion at high load, and the lack of effective means to control the combustion process. Extending its operating range including high load boundary towards full load and low load boundary towards idle in order to allow the CAI engine to meet the demand of whole vehicle driving cycles, has become one of the key issues facing the industrialisation of CAI/HCCI technology. Furthermore, this combustion mode should be compatible with different fuels, and can switch back to conventional spark ignition operation when necessary. In this paper, the CAI operation is demonstrated on a 2-stroke gasoline direct injection (GDI) engine equipped with a poppet valve train.

Controlled Auto-Ignition (CAI) also known as Homogeneous Charge Compression Ignition (HCCI) is increasingly seen as a very effective way of lowering both fuel consumption and emissions. Hence, it is regarded as one of the best ways to meet stringent future emissions legislation. It has however, still many problems to overcome, such as limited operating range. This combustion concept was achieved in a production type, 4-cylinder gasoline engine, in two separated tests: naturally aspirated and turbocharged. Very few modifications to the original engine were needed. These consisted basically of a new set of camshafts for the naturally aspirated test and new camshafts plus turbocharger for the test with forced induction. After previous experiments with naturally aspirated CAI operation, it was decided to investigate the capability of turbocharging for extended CAI load and speed range.

Pumping Mean Effective Pressure (PMEP) is the main factor limiting the improvement of thermal efficiency in a spark-ignition (SI) engine under low load. One of the ways to reduce the pumping loss under low load is to use Cylinder DeActivation (CDA). The CDA aims at reducing the firing density (FD) of the SI engine under low load operation and increasing the mass of air-fuel mixture within one cycle in one cylinder to reduce the throttling effect and further reducing the PMEP. The multi-stroke cycles can also reduce the firing density of the SI engine after some certain reasonable design, which is feasible to improve the thermal efficiency of the engine under low load in theory. The research was carried out on a calibrated four-cylinder SI engine simulation platform. The thermal efficiency improvements of the 6-stroke cycle and 8-stroke cycle to the engine performance were studied compared with the traditional 4-stroke cycle under low load conditions.

Battery temperature is known to have a critical influence on overall battery pack performance, from electrochemical behavior, charge acceptance, power availability, trip efficiency, safety, reliability and life-cycle costs. Temperature monitoring is critical to ensure safe and reliable battery pack operation. Monitoring of cell temperatures in battery packs allows for control and estimation algorithms that can ensure homogenous pack temperature distribution, prevent excessive pack temperature rise and even infer cell core temperature, potentially allowing to both predict and mitigate onset of thermal runaway. The increasing need for improved accuracy requires inclusion of more detail in the modelling stage, leading inevitably to ever larger-scale, ever more complex dynamical systems. Simulations in such large-scale settings lead in turn to unmanageably large demands on computational resources, which is the main motivation for Model Order Reduction.

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 Magma engine concept is characterised by a high compression ratio, central injector combustion system employed in a downsized direct-injection gasoline engine. An advanced boosting system and Miller cycle intake-valve closing strategies are used to control combustion knock while maintaining specific performance. A key feature of the Magma concept is the use of high CR without compromise to mainstream full-load performance levels. This paper focuses on development of the Magma combustion system using a single-cylinder engine, including valve event, air motion and injection strategies. Key findings are that Early Intake Valve Closing (EIVC) is effective both in mitigating knock and improving fuel consumption. A Net Indicated Mean Effective Pressure (NIMEP) equivalent to 23.6 bar Brake Mean Effective Pressure (BMEP) on a multi-cylinder engine has been achieved with a geometric compression ratio of 13:1.

In an era of rapidly increasing vehicle electrification, the gasoline engine remains a vital part of the passenger car powertrain portfolio. Lean-burn combustion is a formidable means for reducing the CO2 emissions of gasoline engines but demands the use of sophisticated emissions control. A 2.0 litre turbocharged direct-injection gasoline engine has been developed with a lean homogeneous combustion system matched to a robust lean and stoichiometric-capable exhaust aftertreatment. The aftertreatment system includes an SCR system and a GPF with filtration down to 10 nm particle size. The engine is equipped with a continuously variable valve-lift system, high-tumble ports and a high-energy ignition system; the boosting system comprises a variable geometry turbocharger and a 48 V electrical supercharger. The work reported formed part of the PaREGEn (Particle Reduced, Efficient Gasoline Engines) project under the Horizon 2020 framework programme.

This paper describes the use of a new probe for direct measurement of particle velocity for an acoustic intensity survey of a test engine at Ricardo UK. The new probe includes both a pressure and a particle velocity transducer in a single package [2], utilising the miniature hot wire principle. This probe enables near-field direct measurement of the acoustic intensity on a test powertrain, and is referred to here as the ‘P-U’ (Pressure- Velocity) Probe. The new technique has significant advantages over the traditional pressure differential acoustic intensity technique that include a wider frequency bandwidth, better rejection of the reverberant sound field and the ability to easily and safely take measurements over a wider range of engine operating conditions. The use of the method for noise source identification is described and the test results are shown to compare well with those obtained from the traditional pressure differential acoustic intensity technique.

The investigation and results presented hereafter are based on the use of a novel technique to improve the performance and emission characteristics of gasoline and diesel engines. The technique involved generating corona discharges within the engine's pre-combustion air stream. These discharges were created by a multi-points charged electrodes. The onset of the discharges facilitated the ionization and excitation process of the neutral air species. New radicals and highly oxidizing species such as atomic oxygen (O) and ozone (O3) were produced and these are known to modify some of the chemical reactions involved in the combustion of hydrocarbon fuels. Measurements of both gasoline and diesel engine torque, speed, various temperatures, fuel consumption and exhaust gas composition were obtained, using a constant throttle position under both normal and coronas operating conditions.

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.

With the introduction in Europe of drive cycles such as RDE and WLTC, transient emissions prediction is more challenging than before for passenger car applications. Transient predictions are used in the calibration optimization process to determine the cumulative cycle emissions for the purpose of meeting objectives and constraints. Predicting emissions such as soot accurately is the most difficult area, because soot emissions rise very steeply during certain transients. The method described in this paper is an evolution of prediction using a steady state global model. A dynamic model can provide the instantaneous prediction of boost and EGR that a static model cannot. Meanwhile, a static model is more accurate for steady state engine emissions. Combining these two model types allows more accurate prediction of emissions against time. A global dynamic model combines a dynamic model of the engine air path with a static DoE (Design of Experiment) emission model.

The 2/4SIGHT engine concept is based on a novel design of combustion system, which makes use of an electric-hydraulic valvetrain and advanced control technologies, enabling automatically controlled dynamic switching of the engine between two- and four-stroke operations. This concept has the potential to improve fuel consumption by up to 30% compared to a conventional gasoline engine. A 3 cylinder GDI engine with two stage boosting system and electro-hydraulic valvetrain is the main application for this project, with 6 cylinder application being studied in simulation. The design of a Control System poses several challenges due to the simultaneous introduction of several innovations such as advanced boost system, electro-hydraulic valvetrain system and two/four stroke operating mode. In order to develop and optimise the design of the control system, an integrated simulation environment has been developed.

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.

The influence of different combustion chamber configuration, intake temperature, and coolant temperature on HCCI combustion processes were investigated in a single-cylinder optical engine. Two-dimensional images of the chemiluminescence were captured using an intensified CCD camera in order to understand the spatial distribution of the combustion. N-heptane was used as the test fuel. Three combustion chamber geometries with different squish lip, salient, orthogonal, reentrant shape, referred as V-type, H-type, and A-type respectively, were used in this study. Intake temperature was set to 65°C and 95°C, while coolant temperature was set to 85°C. The experimental data consisting of the in-cylinder pressure, heat release rate, chemiluminescence images all indicated that the different combustion chamber geometries result in different turbulence intensity in the combustion chamber, and thus affect the auto-ignition timing, chemiluminescence intensity, and combustion processes.

The purpose of this study was to gain a better understanding of the effects of port fuel injection strategies and thermal stratification on the HCCI combustion processes. Experiments were conducted in a single-cylinder HCCI engine modified with windows in the combustion chamber for optical access. Two-dimensional images of the chemiluminescence were captured using an intensified CCD camera in order to understand the spatial distribution of the combustion. N-heptane was used as the test fuel. The experimental data consisting of the in-cylinder pressure, heat release rate, chemiluminescence images all indicate that the different port fuel injection strategies result in different charge distributions in the combustion chamber, and thus affect the auto-ignition timing, chemiluminescence intensity, and combustion processes. Under higher intake temperature conditions, the injection strategies have less effect on the combustion processes due to improved mixing.

A new type direct-injection stratified-charge combustion system for gasoline engines is developed by the authors. In the system, gasoline is directly injected into a cylinder near the end of compression stroke by a nozzle with the injection holes unequally spaced on its tip. The angles among sprays in the vicinity of spark plug are small, and become larger downstream along the direction of air swirl motion. Therefore the circularly concentration stratification form rich to lean of air-fuel mixture is mechanically realized to ensure the reliable ignition and smooth flame propagation in the inhomogeneous mixture after sparking. The selection of main parameters of the system, the performance and the combustion characteristics of the engine after optimization of those parameters are introduced in detail in this paper.

With a view to understanding the air-fuel mixing behavior and the effects of the mixture quality on the emissions formation and engine performance, a new quantitative factor of the in-cylinder air-fuel homogeneity named Homogeneity Factor (HF) has been developed. Its characteristics under various injection conditions and air swirl motions within the cylinder have been investigated with CFD simulation. The results have shown that air-fuel homogeneity is essentially affected by the spatial and temporal fuel distribution within the combustion chamber. Higher injection pressure, longer dwell time and increased pilot fuel quantities can contribute to better mixing quality resulting in increased HF and optimum engine performance with low fuel consumption and soot emissions. With regard to the in-cylinder air motion, increasing swirl ratio enhances the air-fuel mixing quality which has been reflected in the variation of the HF.

Direct injection gasoline engines have the potential for improved fuel economy through principally the engine down-sizing, stratified charge combustion, and Controlled Auto Ignition (CAI). However, due to the limited time available for complete fuel evaporation and the mixing of fuel and air mixture, locally fuel rich mixture or even liquid fuel can be present during the combustion process of a direct injection gasoline engine. This can result in significant increase in UHC, CO and Particulate Matter (PM) emissions from direct injection gasoline engines which are of major concerns because of the environmental and health implications. In order to investigate and develop a more efficient DI gasoline engine, a camless single cylinder DI gasoline engine has been developed. Fully flexible electro-hydraulically controlled valve train was used to achieve spark ignition (SI) and Controlled Autoignition (CAI) combustion in both 4-stroke and 2-stroke cycles.