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This paper presents the results of a study on reasons for the occurrence of pre-ignition in highly supercharged spark ignition engines. During the study, the phenomena to be taken into account were foremost structured into a decision tree according to their physical working principles. Using this decision tree all conceivable single mechanisms to be considered as reasons for pre-ignition could be derived. In order to judge each of them with respect to their ability to promote pre-ignition in a test engine, experimental investigations as well as numerical simulations were carried out. The interdependence between engine operating conditions and pre-ignition frequency was examined experimentally by varying specific parameters. Additionally, optical measurements using an UV sensitive high-speed camera system were performed to obtain information about the spatial distribution of pre-ignition origins and their progress.

Nowadays Spark Ignition (SI) engine efficiency is mainly limited by abnormal combustion (knock) and stability issues at high dilution rate (both EGR and air). Increasing the combustion velocity is a relevant way to overcome these limitations. Main strategy to increase the combustion velocity is to enhance the flow motion in the cylinder (tumble motion) in order to increase the turbulence during the combustion. Such approach is mainly performed by working on intake port design which lead to engine volumetric efficiency penalties. Another approach to increase the combustion velocities is to have multiple ignition kernels in the chamber. This can be obtained thanks to Turbulent Jet Ignition (TJI) which uses a pre-chamber to spread the initial flame kernel throughout the combustion chamber. To achieve pre-chamber optimization a deep understanding of the complex phenomena involved in TJI as well as validated numerical tools is required.

First, several technological problems pertaining to the recycle and closed-cycle diesel engines, but different from the problems of general air environment operation engines, were extracted and the expected engine cycle was discussed from a thermo-dynamic viewpoint. Then, land-based testing equipment for the recycle engine was manufactured for a trial, with intention to develop an underwater power source. With the equipment, experiments were carried out to look into the working and the performance of the engine. Furthermore, the equipment was modified and made into a closed-cycle diesel engine for a trial and experiments were conducted. The test results were compared with the results of the thermodynamic analysis, and the suitability of the analysis method was evaluated. Subsequently on the basis of these data, we succeeded in developing under-water practical power source “HIRUP”.

Automobile OEM's around the world are looking to improve their overall vehicle and engine efficiency in terms of fuel economy and power output. Efficiency improvement is possible by cutting down the engine parasitic loads. Lubrication oil pump is one such source for parasitic loss of multijet diesel engine. One best way of reducing the same is by optimizing the power consumed by the oil pump without appreciably affecting the flow requirements of the engine. This paper describes an effective approach to bring down the power consumption of a fixed displacement oil pump by keying out various factors contributing for the same. Detailed here are the methods used for identifying those factors, modifications carried out in the design, and testing methods employed for the estimation, together with the results achieved. The test results show that it is possible to improve the power consumption of oil pump by 18% as a result of this study.

New Federal and California Regulations present some new challenges for emission testing as low emission variability and different test cell environments through SFTP. One approach to achieve these challenges could be replacing the human driver by a robot driving system. To make a great step forward in the improvement of such robot systems, the German automotive technology research association (FAT) initialized an investigation program in cooperation with three different suppliers. The work was done and reported by the Department of Internal Combustion Engines at the Darmstadt University of Technology. This report summarizes the comparison of the driving style of the human driver to three automatic driving systems from those major manufacturers and some basic optimization work.

Compared with experimental and theoretical approaches modeling of the scavenging process in a two-stroke engine offers great advantages on account of its simplicity and economy. The clear definition of influencing factors and a better physical interpretation of the model laws governing the flow process help to design the model and to determine the test conditions; the model laws also allow the obtained test results to be transferred to the prototype. A relatively simple and inexpensive liquid model presented enables qualitative observations and quantitative evaluations of different port configurations to be made. For the design of port configurations some recommendations are presented. The short circuiting and instabilities in scavenging test results are also mentioned.

In this work the influence of various engine load changes with different engine speeds on the soot particle concentrations and properties was investigated because these operating modes are well known for short but high soot emissions. To derive specific information on emission behavior of particle matters tests were carried out with the Two-Color-Method and the so called RAYLIX technique in a four-cylinder CR-Diesel engine. The Two-Color-Method (2CM) gives crank angle resolved information about soot formation and oxidation processes inside the combustion chamber of a single cylinder. The RAYLIX technique is a combination of Rayleigh-scattering, Laser-Induced-Incandescence (LII) and extinction measurements which enable simultaneous measurements of temporally and spatially resolved soot concentration, mean primary particle radii and number densities in the exhaust gas manifold of the same cylinder investigated by the Two-Color-Method.

Given the fact that, in an endeavor to achieve the goals of engineering for a trade-off between cleaning up exhaust emissions and maximizing fuel economy, two main paths are being followed in advancing and optimizing SI-engine operating strategy in the upper part-load range. On the one hand, homogenization and operation in the compression ignition mode seem to offer a promising means of minimizing NOx emission by keeping the combustion temperature below the formation borderline and accepting a high cylinder-pressure gradient to obtain benefits in fuel economy. On the other hand, there are ambitions to widen the range of stratified operation using a supercharger or turbocharger. This way, efficiency of the engine cycle can be improved by operating at a higher global air-fuel ratio and, with this, a higher polytropic exponent, thereby taking the efficiency chain to a higher level.

Despite the advantages of turbocharging in improved engine performance and reduced exhaust emissions, commercial single-cylinder engines used for automotive applications remain naturally aspirated (NA) and are not generally turbocharged. This is due to the shortcomings with pulsated and intermittent exhaust gas flow into the turbine and the phase lag between the intake and exhaust stroke. In the present study, experimental investigations are initially carried out with a suitable turbocharger closely coupled to a single-cylinder diesel engine. Results indicated that the engine power dropped significantly by 40% for the turbocharged engine compared to the NA version even though the air mass flow rate was increased by at least 1.5 times with turbocharging. A novel approach of decoupling the turbine and the compressor and coupling them separately to the engine is proposed to address these limitations.

The increasing demand of passenger fleet with the depletion of conventional fuels has resulted into a massive research for harnessing the potentials in alternate fuels. Vis-à-vis, compressed natural gas (CNG) has been a proven clean automotive fuel and is playing a vital role towards the development of new engine concepts or in terms of retrofits. With vast CNG reservoirs present in over 90 countries worldwide, CNG as an alternate auto fuel has been drawing a greater attention. CNG has a very high octane rating and hence can be operated to run under the Highest Useful Compression Ratio (HUCR), thus seeming more applicable under both SI and CI mode. CNG engines desire a compact and turbulent combustion chamber owing to its lower laminar flame propagation characteristics and hence desire proper mixing of air and fuel as well for the flame to propagate to the end charge, making it inevitable to develop piston geometries that can develop turbulence inside the combustion chamber.

Friction materials for automotive brakes are known to exhibit a time-dependent tribological behavior. When examining these dynamic effects special demands are made on the measurement device: The influences of the brake system should be minimized and parameters like velocity, contact pressure and temperature should be controlled closely and independently. Furthermore, special test procedures need to be designed. This can ideally be achieved using a scaled tribometer like the High-Load-Tribometer at the Institute of Dynamics and Vibrations in Braunschweig. Former investigations [1] have shown that a kind of memory effect can occur for a low-met brake pad rubbing on a cast iron disk. A variation of the initial disk temperatures has revealed that a temporary increase of the coefficient of friction can occur at slightly elevated temperatures. This effect is memorized by the material as a certain procedure needs to be performed in order to achieve a regeneration.

Investigations on valve recession of a commercial vehicle engine inlet valve are done. Failure analysis of inlet valve of a six cylinder commercial vehicle engine developing power of 155 BHP is carried out using the software tools IDEAS and TYCON. Failed engine valves are investigated and concluded that the mode of failure of most of them is valve recession, the possible factors responsible for the valve failure are analyzed including the metallurgical properties of the valve. Combustion force, impact force during closure of the valve are the major factors responsible for valve recession. The valve seat angle is considered in the analysis to find if the change in this angle is helpful in increasing the life of the valve. The prevailing wear mechanism has been shown related to the critical operating conditions such as valve closing velocity, combustion load, valve misalignment relative to the seat insert and seat insert material choice.

Due to the high amount of valve train noise in multi-valve engines measures were developed to reduce this noise. These measures are dynamically optimized profiles and cam phasing (small angular shift between neighboured cams). Both measures show a drastic reduction in valve train noise and also overall engine noise but do not have any negative effects on performance, economy and costs. Not only overall noise is improved but also sound quality especially impulsiveness characterized by the Kurtosis factor. To assess these design changes with respect to radiated noise in the early design stage an estimation method was used. The estimation method is based on the calculated force and velocity time histories and shows good correlation with the measured data.

Advanced SI engines for passenger cars often use the cylinder deactivation technology for dethrottling and thus achieving a reduction of fuel consumption. The gas exchange valves of the deactivated cylinders are closed permanently by a zero lift of the cams. The solutions for cylinder deactivation can vary in the kind of gas composition included in the deactivated cylinders: charge air, exhaust gas or vacuum. All these strategies have in common the frequent loss of captured charge mass from cycle to cycle. Their two-stroke compression-expansion cycle additionally intensifies this phenomenon. Thus, a significant decrease of the minimum cylinder pressure can cause an undesired entry of lubricant into the combustion chamber. The idea was to ventilate the generally deactivated cylinders frequently to compensate the loss of captured cylinder charge mass. The task was to keep the minimum cylinder pressure above a certain limit to prevent the piston rings from a failure.

This paper covers research findings on digital projections on the road. Data is provided for the root cause analysis of non-existing distraction proven by several studies. The study describes if and in which geometrical space road projections are visible to other road traffic participants. Such participants can be e.g. oncoming, passing drivers or pedestrians standing aside the road. The paper data shows where projections are recognizable and assignable to the original intention of the projection. A grid was created to identify the areas where digital projections could be understood and where the digital projections were just illegible. A dominant factor is the grazing incidence. The photons are distributed over a larger area and only the driver’s view makes a virtual compression of the illuminated area in order to make the signals legible. The results show that distraction for other road participants is unlikely for any position outside very limited areas.

Automotive exhaust mufflers are not only attenuating noise, but can, in fact, along with other exhaust components, generate noise within the exhaust system. This type of noise is commonly called “flow generated noise” to distinguish it from the “pulsation noise” excited by the combustion engine. Flow generated noise is normally very broad band but it can also have tonal regions. This tonal flow noise can sound like a whistle. In this contribution an experimental study of the generation and prevention of such whistle tones will be presented. The study was focused on perforated pipes in mufflers with different perforation patterns, hole sizes and hole shapes. The noise spectra have been measured on a flow bench at room temperature as well as under real (hot) conditions on a vehicle. The results will be correlated in terms of frequency and Strouhal number. Concepts to avoid or suppress these tones will also be discussed.

Magnesium alloy, known for its high strength and lightweight properties, finds widespread utilization in various technical applications. Aerospace applications, such as fuselages and steering columns, are well-suited for their utilization. These materials are frequently employed in automotive components, such as steering wheels and fuel tank lids, due to their notable corrosion resistance. The performance of magnesium alloy components remains unimproved by normal manufacturing methods due to the inherent characteristics of the material. This work introduces a contemporary approach to fabricating complex geometries through the utilization of Wire-Electro Discharge Machining (WEDM). The material utilized in this study was magnesium alloy. The investigation also considered the input parameters associated with the Wire Electrical Discharge Machining (WEDM) process, specifically the pulse duration and peak current.

Performance of a compression ignition engine fuelled with animal fat and its emulsions as fuel is evaluated. A single cylinder air-cooled, direct injection diesel engine developing a power output of 2.8 kW at 1500 rev/min is used. Base data is generated with standard diesel fuel. Subsequently, animal fat is modified into its emulsions using water and methanol. Comparison is undertaken with diesel, neat animal fat and its emulsion as fuels. Results show improved performance with animal fat emulsions as compared to neat fat. Peak pressure and rate of pressure rise are increased with animal fat emulsions due to improved combustion rate. Heat release pattern shows higher premixed combustion rate with the emulsions. Higher ignition delay and lower combustion duration are found with animal fat emulsions than neat fat. Drastic reduction in black carbon smoke and NO are found with the emulsions as compared to neat animal fat and neat diesel.

The objective of this investigation was to evaluate the effects of a variable intake and exhaust valve timing in terms of opening, closing, opening duration, lift curve and number of active valves per pair on a four cylinder direct-injecting SI engine for the catalyst heating idling phase at the beginning of an NEDC emission test procedure. The first step evaluated the engine behavior at a reference point of operation. Its parameters in valve timing were adjusted to match the valve timing of the base production engine. The second step investigated the effects of an earlier exhaust valve opening while the exhaust valve closing time was kept and the exhaust valve opening duration was extended. The third step was to answer the question for the optimum number of exhaust valves in order to minimize the wall heat losses inside the cylinder head. The optimum 3V exhaust valve timing has been defined as the basis for exhaust valve timing for steps four and five.

The carbon-neutral biodiesel is a promising renewable substitute for fossil diesel that renders the traditional oxides of nitrogen-particulate matter (NOx-PM) trade-off into a unidirectional NOx control problem. Low-temperature combustion (LTC) modes such as homogenous charge compression ignition (HCCI) are attractive for obtaining ultra-low NOx and PM emissions. Studies on utilizing biodiesel fuel for HCCI combustion mode are sparsely available. Moreover, biodiesel emulsions in the HCCI combustion mode have not been attempted so far. Based on this premise, the present work explored the potential to utilize biodiesel and its emulsions having 20% and 25% water by volume under HCCI operating conditions. Biodiesel was prepared from a non-edible Karanja oil. The biodiesel emulsions were prepared using a heated magnetic stirrer apparatus with 3% by volume of the raw Karanja oil as a surfactant.