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The future emission legislations for diesel passenger cars are likely to include more dynamic test cycles than we have today, such as the World harmonized Light duty Testing Cycle (WLTC) and Real Drive Emissions (RDE) in the EU and very challenging SULEV legislations in the USA. In order to meet these emission legislations and challenging CO2 targets, more complex Exhaust Gas After Treatment Systems - EGATS and corresponding calibration strategies are needed. The calibration strategies have to provide the best possible fuel consumption and NOx emissions across the entire engine map for all tested cycles. The aim of this paper is to evaluate the effect of several EGATS configurations and calibrations on tailpipe NOx and CO2 emissions of a D segment vehicle. The experimental results and potential of various EGATS configurations and calibrations for the optimisation of fuel consumption and NOx emissions are presented and discussed.

The open MAHLE Flexible ECU (MFE) was developed and successfully implemented for controlling gasoline, diesel and hybrid engines. The increased demand of new functions development to address future powertrain challenges, such as lower fuel consumption, ever more stringent emissions legislative targets as well as the need to reduce development time and cost at the same time, led to the incorporation of the MFE functions in a co-simulation environment. The co-simulation environment consists of using the virtual engine developed with 1D or 3D numerical simulation tools and the functions of MFE developed with Simulink-Targetlink. This co-simulation approach allows modifying either the engine control or the engine itself. Regarding the engine control and its development, the existing and new functions were tested for the performance, emissions and behaviour changes on several production and prototype engines.

The need for improved emissions and fuel economy are placing increasingly severe performance requirements on compression ignition engines. These are satisfied in part by advanced fuel injection equipment that provide multiple injections and increased injection pressures along with higher operating temperature. Fuel composition is also changing, with increased use of non-traditional feedstocks combined with a range of additive chemistries to restore or enhance fuel quality. Within this environment, a number of worldwide automotive companies have noted a trend towards increased Internal Injector Deposits (IID). Little quantitative information to understand the root cause is available, largely due to difficulty in reproducing the issue under controlled conditions. The present study details the results of an accelerated test methodology, which is used to evaluate the interrelated effects of fuel composition and operating environment.

Current developments in fuels and emissions regulations are resulting in an increasingly severe operating environment for diesel fuel injection systems. The formation of deposits within the holes or on the outside of the injector nozzle can affect the overall system performance. The rate of deposit formation is affected by a number of parameters, including operating conditions and fuel composition. For the work reported here an accelerated test procedure was developed to evaluate the relative importance of some of these parameters in a high pressure common rail fuel injection system. The resulting methodology produced measurable deposits in a custom-made injector nozzle on a single-cylinder engine. The results indicate that fuels containing 30%v/v and 100% Fatty Acid Methyl Ester (FAME) that does not meet EN 14214 produced more deposit than an EN590 petroleum diesel fuel.

An increasing range of conventional and unconventional feed stocks will be used to produce fuel of varying chemical and physical properties for use in compression ignition engines. Fischer-Tropsh (F-T) technology can be used to produce fuels of consistent quality from a wide range of feed stocks. The present study evaluates the performance of F-T fuel in advanced common rail fuel injection systems. Laboratory scale tests are combined with proprietary engine and electrically driven common rail pump hydraulic rig tests to predict long-term performance. The results obtained indicate that the performance of F-T fuel is at least comparable to conventional hydrocarbon fuels and superior in a number of areas. In particular, the lubricity of F-T fuel was improved by addition of lubricity additives or FAME, with minimal wear under a wide range of operating conditions and temperatures.

Partially Premixed Combustion (PPC) is a combustion concept by which it is possible to get low smoke and NOx emissions simultaneously. PPC requires high EGR levels and injection timings sufficiently early or late to extend the ignition delay so that air and fuel mix extensively prior to combustion. This paper investigates the operating region of single injection diesel PPC in a multi cylinder heavy duty engine resembling a standard build production engine. Limits in emissions and fuel consumption are defined and the highest load that fulfills these requirements is determined. Experiments are carried out at different engine speeds and a comparison of open and closed loop combustion control are made as well as evaluation of an extended EGR-cooling system designed to reduce the EGR temperature. In this study the PPC operating range proved to be limited.

Partially Premixed Combustion (PPC) has shown its potential by combining high combustion controllability with emission characteristics that are close to those of an HCCI engine. In order to get PPC the ignition delay needs to be long enough for the fuel and air to mix prior to combustion. This can be achieved by injecting the fuel sufficiently early while running with high EGR. In order to find out where and how PPC occurs a map that shows the changes in combustion characteristics with injection timing and EGR was created. The combustion characteristics were studied in a six cylinder heavy duty engine where the Start of Injection (SOI) was swept from early to late injection over a wide range of EGR levels. The emissions were monitored during the sweeps and in the most promising regions, with low emissions and high efficiency, additional changes in injection pressure and engine speed were applied to get a more versatile picture of the combustion.

The pursuit of new combustion concepts or modes is ongoing to meet future emissions regulations and to eliminate or at least to minimize the burden of aftertreatment systems. In this research, Premixed Low Temperature Diesel Combustion (PLTDC) was developed using a single-cylinder engine to achieve low NOx and soot emissions while maintaining fuel efficiency. Operating conditions considered were 1500 rpm, 3 bar and 6 bar IMEP. The effects of injection timing, injection pressure, swirl ratio, EGR rate, and multiple injection strategies on the combustion process have been investigated. The results show that low NOx and soot emissions can be obtained at both operating conditions without sacrificing the fuel efficiency. Low NOx and soot emissions are achieved through minimization of peak temperatures during the combustion process and homogenization of in-cylinder air-fuel mixture.

Future light, medium and heavy duty diesel engines will need to satisfy the more stringent emission levels (US 2014, Euro 6, etc.) without compromising their current performance and fuel economy, while still maintaining a competitive cost. In order to achieve this, the Fuel Injection Equipment (FIE) together with the pressure charging, cooling system, exhaust after treatment and other engine sub-systems will each play a key role. The FIE has to offer a range of flexible injection characteristics, e.g. a multiple injection train with or without separation, modulated injection pressures and rates for every injection, higher specific power output from the same injector envelope, and close control of very small fuel injection quantities. The aim of this paper is to present Delphi's developments in fuel injection strategies for light and medium duty diesel engines that will comply with future emission legislation, whilst providing higher power density and uncompromised fuel economy.

In order to meet new worldwide emission regulations for heavy-duty diesel engines and to provide high specific power output without fuel consumption penalties there is a requirement for the fuel injection system to have a flexible choice of injection characteristics. Such a fuel injection system has to provide multiple injections, modulated injection pressures and rates for every injection, and possibly variable spray cone angle to accommodate early injection without wall wetting whilst maintaining conventional injection for rated power. The aim of this paper is to present the advanced hybrid electronic unit injector system (EUI). This system incorporates an accumulator rail, which enables high pressure multiple injection events at different injection pressures for a very wide range of injection timings that would not normally be achievable using a conventional EUI system and single lobe EUI camshaft.

In a future ‘hybrid’ mode internal combustion engine capable of running in spark ignition (SI) and controlled auto ignition-CAI (also known as Homogeneous Charge Compression Ignition-HCCI) modes, transition between these modes, during changes in engine load and speed, will play a crucial role. The valve train and engine management system (EMS) must provide a fast and smooth transition between these two very different combustion modes keeping all relevant engine and combustion parameters in an acceptable range. In order to obtain such transition between SI and HCCI and SI, a valve event (duration, timing and lift) has to be variable, which consequently leads to high demands on the valve train and therefore a need for its higher degree of flexibility. Two valve train concepts, one with a Cam Profile Switching (CPS) and phaser system and the other camless using Fully variable Valve Train (FVVT) are presented.

The Homogeneous Charge Compression Ignition (HCCI) engine combustion uses heat energy from trapped exhaust gases enhanced by the piston compression heating to auto ignite a premixed air/gasoline mixture. As the HCCI combustion is controlled by the charge temperature, composition and pressure, it therefore, prevents the use of a direct control mechanism such as in the spark and diesel combustion. Using a large amount of trapped residual gas (TRG), is seen as one of the ways to achieve and control HCCI in a certain operating range. By varying the amount of TRG in the fresh air/fuel mixture (inside the cylinder), the charge mixture temperature, composition and pressure can be controlled and hence, the auto ignition timing and heat release rate. The controlled auto ignition (HCCI) engine concept has the potential to be highly efficient and to produce low NOx, carbon dioxide and particulate matter emissions.

The homogeneous charge compression ignition-HCCI (also to be known as controlled auto ignition-CAI) engine concept has the potential to be highly efficient and to produce low NOx, carbon dioxide and particulate matter emissions. It experiences, however, problems with cold start, running at idle and high loads that together with controlling the combustion over the entire speed/load range limits its practical application. A solution to overcome these problems is to operate the engine in ‘hybrid mode’, where the engine operates in HCCI mode at low, medium and cruising loads and switch to spark ignition (SI) mode (or diesel mode-CI) at a cold start, idle and higher loads. To operate such ‘hybrid mode’ engine, a transition between SI and HCCI and SI modes, as a result of changes in engine speed and load must be seamless in operation, whilst keeping all relevant engine and combustion parameters in an acceptable range.

Homogeneous Charge Compression Ignition (HCCI) engine concept has the potential to be high efficient and to produce low NOx and particulate matter emissions. However, the problem of controlling the combustion over the entire load/speed range limits its practical application. The HCCI combustion is controlled by chemical kinetics of the charge mixture, with no influence of the flame diffusion or turbulent propagation. Therefore, to achieve a successful control of the HCCI process, the composition, temperature and pressure of the charge mixture at IVC point have to be controlled. The use of the variable valve timing strategy that enables quick changes in the amount of trapped hot exhaust gases shows the potential for the control of the HCCI combustion.

Controlled Auto Ignition (CAI) uses compression heat to auto ignite a homogeneous air/fuel mixture. Using internal exhaust gas recirculation (IEGR) as an indirect control method, CAI offers superior fuel economy and pollutant emission reductions. Practically, this can readily be achieved by a method of early exhaust valve closure and late inlet valve opening to trap exhaust gas residuals within the cylinder from one cycle to the next. In order to understand the combustion mechanism, we did a comprehensive investigation on CAI fuelled with iso-octane. Test data was gathered from a single cylinder research engine equipped with Lotus' Research Active Valve Train (AVT) System, and the modelling study was based on detailed chemical kinetics. It was found that CAI can only occur when the thermal energy of the engine charge, which is a mixture of air / fuel and IEGR, reaches a certain level.

Engines with controlled auto-ignition (CAI) combustion offer a number of benefits over conventional spark ignited (SI) and compression ignited (CI) engines, such as much lower NOx emission due to its relatively low combustion temperature, negligible cycle-to-cycle variation due to its self-ignition nature, higher combustion efficiency at part load than its SI counterpart, and low soot emissions since a homogeneous lean air/fuel mixture is being employed. Unlike conventional SI and CI engines, where combustion is directly controlled by the engine management system, the combustion in CAI engines is controlled by chemical kinetics only. Over the past two decades, a number of technologies have been developed to initiate such combustion on both 2 and 4-stroke engines with various fuels, but none of them could maintain the combustion over the wide engine operation range. Remaining problems include control of ignition timing and the heat release rate over the entire engine operation range.