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The main assignment of Controlled Auto Ignition (CAI) operation range expansion is to reduce the burn rate or combustion noise at high load and to minimize misfire at low load. The potential of two principal EGR strategies is well known to initiate CAI in a wide range of operation map by using a variable train system: the Exhaust Port Recirculation (EPR) for higher part load and the Combustion Chamber Recirculation (CCR - also called Negative Valve Overlap) for lower part load. However the detailed comparison of the ignition phenomena with each EGR strategy has not been fully studied yet. In this paper, EPR and CCR were compared with same operational condition (engine speed and load). For the analysis, flame luminescence and Raman scattering method for optical measurement and STAR-CD (CD-adapco) for numerical simulation are used.

Particle size distribution and particle number emissions rather than legislated particulate mass emissions from diesel engines are subject of rising concern especially in the US and several Western European countries [1]*. Recently also particle number emissions from gasoline engines attracted much attention since these engines are supposed to emit very high numbers of ultrafine particles or even nano-sized particles [2]. The work described in this paper focused on the impact of modern diesel exhaust gas aftertreatment systems like diesel oxidation catalysts (DOC) and diesel particulate filter (DPF) on particle number emission. Especially the effect that these aftertreatment systems are supposed to significantly increase ultrafine particle numbers (because they may act like “reactors” actively producing ultrafine solid particles) gave reason for investigating the effects and mechanisms more in detail.

This paper reports the results of theoretical and experimental investigations in the field of variable intake - valve control of spark-ignition engines. Different degrees of freedom for a variable intake profile such as variable intake opening and closing events, variable valve lift, as well as the deactivation of one of the intake valves per cylinder of a multi-valve engine are considered and evaluated concerning their potential to reduce pumping losses, to support mixture formation, and to improve combustion. The investigations show that additional efforts are necessary to convert the potential of minimized pumping losses due to unthrottled SI-engine load control into reduced fuel consumption and good driveability. Increased gas velocities during intake for low engine speed and load and adjusted residual-gas fractions according to the different operating conditions prove to be very efficient parameters to improve engine performance under unthrottled conditions.

All reciprocating engines from the first Diesel engine to turbocharged formula 1 engines require a sealing of the combustion chamber. This sealing is realized by the compression rings. Today a set of two compression rings and one oil control ring is standard, the large variety of available solution demonstrate the continuous effort and attention paid to an optimized system performance since the first engine was started. The complexity of the interactions with the mechanical, thermal, thermodynamic, tribologic, dynamic behavior of the piston still requires mechanical testing of the various components before release to series production. This procedure can be shortened by use of simulation models reflecting the real behavior in detail to select the most promising combinations of components and characteristics.

Geartrain-related noise has become a more dominant noise concern mainly due to the increasing demand for high-pressure injection systems. Engine geartrain noise is mainly caused by torque fluctuations of the crankshaft and the injection system, both leading to tooth impacts between the gears of the geartrain. Gear impacts can generate dominant NVH problems due to the high frequency content of the gear impact forces, although their amplitudes are much lower than those of the combustion forces. If the natural frequencies of the surrounding structure are met, an intensive radiation of the surrounding structure is caused. FEV has developed a simulation method for the analysis of geartrain dynamics aimed at identifying and optimizing potential noise sources. This simulation method is an essential tool for the development process of a technical product. It realizes a minimum effort to set up the model at reduced calculation time.

The IDI diesel engine still offers a substantial development potential. One major advantage is its low fuel consumption and, hence, its low CO2 emission compared to gasoline engines. The disadvantage of its higher noise emission, however, requires particular attention in the development stage. By means of modern signal analysing and signal processing methods in combination with computer simulation methods new tools for the development of low noise Diesel engines are available. The noise emission of IDI diesel engines has on average been reduced by about 5 to 8 dBA within the last 15 years. This trend will continue further despite the introduction of more and more light weight design components. Today's IDI diesel engine is mainly dominated by high noise levels in the frequency range about 1600 to 2000 Hz. In-depth measurements show that this is generally caused by a high combustion excitation (Helmholtz-resonance) and, in addition, structure weaknesses of the crankcase.

At the present time, combustion process effects on vehicle interior noise can be evaluated only when vehicle and engine are physically available. This Paper deals with a new method for the prediction of combustion process induced vehicle interior noise. The method can be applied already in early combustion system development and allows a time and cost efficient calibration optimization of engine and vehicle. After establishing appropriate transfer weighting functions (engine) and structure transfer functions (vehicle), audible vehicle interior noise is generated based on appropriate cylinder pressure analysis. Combustion process effects on interior noise can be judged subjectively as well as objectively. Thus, combustion process development at the thermodynamic test bench is effectively supported to achieve an optimal compromise with respect to fuel consumption, exhaust emission and interior noise quality.

The current direction for Diesel combustion system development is towards homogenization, in order to reduce particulate and NOx emissions. However, a strong increase of carbon monoxide emissions (CO) is frequently noted in combination with enhanced homogenization. Therefore, the current investigation focuses on a detailed analysis of the particulate - CO trade-off using a laser-optical and multidimensional CFD investigation of the combustion process of a swirl HSDI system. The CFD methodology involves reduced kinetics for soot formation and oxidation and a three-step CO model. These models are validated by a detailed comparison to optical measurements of flow, spray penetration and the spatial distribution of soot, temperature and oxygen concentration. The results obtained show that high concentrations of CO occur as an intermediate combustion reaction product. Subsequently, CO and soot are oxidized in large areas of the combustion chamber.

Future boundary conditions for vehicle engine development will be very complex since they are “functions” of parameters that are difficult to predict: increasingly stringent legislation, changing consumer demand, and availability of resources. The main development goals for passenger cars today are the enhancement of performance and reduction of fuel consumption and cost while facing future emission standards. In China for example, drastic changes in emission regulation have forced the automotive industry to speed up the development processes and shorten the product life cycles. In this respect, the Mianyang Xinchen Engine Co. Ltd, part of Brilliance Group, Mianyang China and FEV Motorentechnik, Aachen Germany conducted a joint project to study Mianyang's 2.2L, 2-valve, multipoint fuel injection (MPI) gasoline engine.

Fuel consumption of a modern combustion engine is significantly influenced by the mechanical friction losses. Particularly in typical city driving, the reduction of the engine friction losses offers a remarkable potential in emission and fuel consumption reduction. The analysis of the engine friction distribution of modern engines shows that the piston group has a high share at total engine friction. This offers a high potential to optimize piston group friction. The paper presents results of recent research and development work in the field of the tribological system piston/piston ring/cylinder bore.

An improved plasma reactor has been designed, built and evaluated. It is characterized by a reduced power per area ratio, relative to previous designs, and includes several improvements to run the whole system safely in a car. The new reactor design includes a concentric inner high voltage electrode, a grounded outer electrode, a shielded high-voltage and high temperature resistant electrical connection. A generator controller has been developed for better control of operating conditions as required during the engine cold start phase. The new generator/reactor system was installed in the exhaust pipe of a gasoline direct injection engine. HC emissions could be reduced up to 30 % in the first 40 seconds of a cold start test. In addition to HC treatment the dielectric barrier discharge has also been investigated as a method for regenerating a diesel particulate trap.

The reduction of particulate emissions from diesel engines is one of the most challenging problems associated with exhaust pollution control, second only to the control of NOx from any “lean burn” application. Particulate emissions can be controlled by adjustments to the combustion parameters of a diesel engine but these measures normally result in increased emissions of oxides of nitrogen. Diesel particulate filters (DPFs) hold out the prospect of substantially reducing regulated particulate emissions and the task of actually removing the particles from the exhaust gas has been solved by the development of effective filtration materials. The question of the reliable regeneration of these filters in situ, however, remains a difficult hurdle. Many of the solutions proposed to date suffer from high engineering complexity and/or high energy demand. In addition some have special disadvantages under certain operating conditions.

Fuel additives can contribute to maintaining the performance of diesel engines in a variety of ways. This holds true for current and future engine technology. Fouling of indirect injection engines (IDI) has been studied at length. Fouling of direct injection engines (Dl) is less known and less well understood. Problems associated with Dl fouling and a proposed mechanism for it are discussed. Additive effectiveness in preventing injector fouling is confirmed. Injector hole corrosion/erosion, as experienced in the Cummins N14 engine, can be avoided by the appropriate additive chemistry. Particulate traps can also benefit from ashless additive technology aimed at increasing the time between regeneration steps, hence improving effective trap life.

The reduction of the fuel consumption and the emissions are the two main goals for the development of current and future engines. Both consumption and emissions are highly influenced by the fluid and the material temperatures of the engine. This offers potential especially at low engine speeds and engine loads to reduce the cooling power and increase the material temperatures to a tribologic and thermodynamic optimized level. The cooling system which is able to control the cooling power and the material temperatures, the required control devices and the control strategy are designated as intelligent heat management. The definition of the requirements for the control devices and the definition of the control strategies requires detailed knowledge about the thermal engine behavior.

Combustion noise plays a considerable role in the acoustic tuning of gasoline and diesel engines. Even though noise levels of modern diesel engines reach extremely low values, they are still higher than those of conventional gasoline engines. On the other hand, new combustion procedures designed to improve fuel consumption lead to elevated combustion noise excitations as in case of today's direct injecting gasoline engines whose vibration excitation and airborne noise emissions are slightly increased during stratified operation. The partly conflicting development goals resulting from this can only be realized by integrating the NVH specialists' expertise into every development step from concept to SOP.

A comparison of two different types of NOx reducing catalysts will be worked out. The potential of two De-NOx catalysts using engine out hydrocarbon emissions for NOx conversion will be shown by variation of different engine parameters. An analysis of the hydrocarbon species upstream and downstream catalyst will demonstrate, which components are responsible for the NOx reduction in the exhaust gas of a lean burn engine. By variation of different parameters during adsorbtion and regeneration phases of the adsorber catalyst the efficiency in NOx reduction will be optimized. An assessment of the suitability for lean burn engines will consider the emission reduction efficiency as well as the influence on engine fuel consumption.

This paper describes an alternative catalyst aging process using a hot gas test stand for thermal aging. The solution presented is characterized by a burner technology that is combined with a combustion enhancement, which allows stoichiometric and rich operating conditions to simulate engine exhaust gases. The resulting efficiency was increased and the operation limits were broadened, compared to combustion engines that are typically used for catalyst aging. The primary modification that enabled this achievement was the recirculation of exhaust gas downstream from catalyst back to the burner. The burner allows the running simplified dynamic durability cycles, which are the standard bench cycle that is defined by the legislation as alternative aging procedure and the fuel shut-off simulation cycle ZDAKW. The hot gas test stand approach has been compared to the conventional engine test bench method.

A combined finite element method (FEM), multibody system simulation (MSS), and hydrodynamic (HD) bearing simulation technique can be applied to solve for engine crankshaft and cylinder block dynamics. The cylinder block and crankshaft are implemented in the MSS program as flexible FEM structures. The main bearing oil film reaction is described in the MSS program by a pre-calculated reaction force database. The results are displacements and deformations of the crank train parts and the main bearing reaction forces. Verification of the tool was carried out by comparison of main bearing cap accelerations to measured data.

Based on NVH tests conducted on a heavy-duty turbocharged DI diesel engine, noise relevant differences between steady-state and transient operating condition were investigated. A vehicle drive-by test simulating the effects of vehicle mass and inertia was performed, followed by transient NVH measurements in a semi-anechoic test cell. Steady-state noise was exceeded by 5 dBA during transient operation due to broadband increase of noise excitation combined with structure resonance amplification. Transient noise results mainly from “harsher” combustion as a consequence of enlarged ignition delay indicated by significant increase in maximum cylinder pressure gradient. Variation of geartrain excitation and combustion excitation revealed that geartrain noise is of minor importance in this context.

The distortion of the cylinder liners of internal combustion engines has a significant affect on engine operation. It can affect the lubrication oil consumption, the blow-by, the wear behaviour and due to the friction, the fuel consumption. In order to achieve future requirements regarding exhaust emissions and fuel consumption, the requirements for low cylinder distortion engine blocks will play a significant role. Hence, a new technique to determine liner distortion during fired engine operation was developed.