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The European Union (EU) has defined legally-binding targets for the fleet of new cars allowing 95 grams CO2 per kilometer in 2021. It is already under discussion to reduce average emissions of the EU car fleet by further 15% in 2025 and again by 30% in 2030 compared to 2021 goal. Therefore, improvement of fuel economy is becoming one of the most important issues for the car manufacturers. Today’s conventional car powertrain systems are reaching their technical limits and will not be able to meet future fuel economy targets without further development of additional measures. This paper presents the analysis of a Rankine cycle unit applied to improve the overall efficiency of a hybrid electric vehicle (HEV). The authors propose a new concept for recovering a considerable part of exhaust waste heat from an HEV with spark ignition internal combustion engine (ICE) by applying a bottoming Rankine cycle with a Ruths storage tank.

In the low-cost segment for 2-Wheelers legislative, economic and ecologic considerations necessitate a reduction of the emissions and further improvement in fuel consumption. To reach these targets, the commonly used carburetors are being replaced by engine management systems (EMS). One option to provide these systems for acceptable and attractive system costs is to save a sensor device and to substitute its measure by an estimation value. In many motorcycles the rotor of the vehicle's alternator is rigidly attached to the crankshaft. Therefore, the voltage and current signals of the alternator contain information about the engine's speed, which can be retrieved by evaluating these electric signals. After further processing of this information inside the electronic control unit (ECU), the absolute crankshaft position can be obtained. A high-resolution speed signal without mechanical distortions like tooth errors is gained, whose signal quality equals the one of a common speed sensor.

At part load and wide open throttle operation with stratified charge and lean mixture conditions the Direct Injection Spark Ignition (DISI) engine offers similar efficiency levels compared to compression ignition engines The present paper reports on results of recent studies on the impact of the in-cylinder processes in DISI engines e. g. the injection, the in-cylinder flow, the mixture preparation and the ignition on the combustion, the energy conversion and the exhaust emission behavior. The analyses of the spray behavior, of the in-cylinder flow during compression as well as of the flame propagation have been carried out applying advanced optical measurement techniques. The results enable a targeted optimization of the combustion process with respect to engine efficiency and exhaust emissions. The benefits of an increase in fuel injection pressures up to 100 MPa are discussed.

In the Indian two-wheeler market, legislation and customers demand for a reduction of emissions and an increase of fuel efficiency. For two-wheelers with engine management systems, a cost-efficient approach for this trend exploits that the periodical fluctuation of the engine speed of single cylinder engines contains useful information about its operating conditions. The present article focuses on the quality of the estimation of combustion phasing and air-fuel ratio of a 125cc single cylinder motorcycle engine, obtained from the evaluation of these fluctuations. The robustness of an oxygen sensor-less port fuel injection system can be increased by using the estimated air-fuel ratio to adapt the parameters of the fuel injection algorithm.

The investigation of transient engine operation plays a key role of the future challenges for individual mobility in terms of real driving emissions (RDE). A fundamental investigation of the transient engine operation requires the simultaneous application of measurement technologies for an integrated study of mixture formation, combustion process and emission formation. The major prerequisite is the combustion cycle and crank angle resolved analysis of the process for at least several individual consecutive combustion cycles during transient operation. The investigations are performed with a multi cylinder DISI engine at an Engine-in-the-Loop test bench, able to operate the engine in driving cycles as well as within target profiles (e.g. speed and torque profiles). The research project describes the methodology of analyzing elementary transient operational phases, (e.g. different variants of load steps).

In the present paper the results of a set of experimental investigations on LSPI are discussed. The ignition system of a test engine was modified to enable random spark advance in one of the four cylinders. LSPI sequences were successfully triggered and exhibited similar characteristics compared to regularly occurring pre-ignition. Optical investigations applying a high speed camera system enabling a visualization of the combustion process were performed. In a second engine the influence of the physical properties of the considered lubricant on the LSPI frequency was analyzed. In addition different piston ring assemblies have been tested. Moreover an online acquisition of the unburned hydrocarbon emissions in the exhaust gas was performed. The combination of these experimental techniques in the present study provided further insights on the development of LSPI sequences.

Equipping low cost two-wheelers with engine management systems (EMS) enables not only a reduction of emissions but also an improvement in fuel consumption and system robustness. These benefits are accompanied by initially higher system costs compared to carburetor systems. Therefore, intelligent software solutions are developed by Bosch, which enable a reduction of the necessary sensors for a port fuel injection system (PFI) and furthermore provide new possibilities for combustion control. One example for these intelligent software solutions is a model based evaluation of the engine speed. By use of the information contained in the engine speed signal, characteristic features like air charge, indicated mean effective pressure (imep) and combustion phasing are derivable. The present paper illustrates how these features could be used to reduce the system costs and to improve fuel consumption and system robustness.

Cost reduction of engine management systems (EMS) for two-wheeler applications is the key to utilize their potentials compared to carburetor bikes regarding emissions, fuel economy and system robustness. In order to reduce the costs of a system with port fuel injection (PFI) Bosch is developing an EMS without a manifold air pressure (MAP) sensor. The pressure sensor is usually used to compensate for different influences on the air mass, which cannot be detected via the throttle position sensor (TPS) and mean engine speed. Such influences are different leakage rates of the throttle body and changing ambient conditions like air pressure. Bosch has shown in the past that a virtual sensor relying on model based evaluation of engine speed can be used for a detection of leakage air mass in idling to improve the pre-control of the air-fuel ratio. This provides a functionality which so far was only possible with an intake pressure sensor.

Regarding the strongly growing two-wheeler market fuel economy, price and emission legislations are in focus of current development work. Fuel economy as well as emissions can be improved by introduction of engine management systems (EMS). In order to provide the benefits of an EMS for low cost motorcycles, efforts are being made at BOSCH to reduce the costs of a port fuel injection (PFI) system. The present paper describes a method of how to reduce the number of sensors of a PFI system by the use of sophisticated software functions based on high-resolution engine speed evaluation. In order to improve the performance of a system working without a MAP-sensor (manifold air pressure sensor) an air charge feature (ACFn) based on engine speed is introduced. It is shown by an experiment that ACFn allows to detect and adapt changes in manifold air pressure. Cross-influences on ACFn are analyzed by simulations and engine test bench measurements.

Small gasoline engines are used in motorcycles and handheld machinery, because of their high power density, low cost and compact design. The reduction of hydrocarbon emissions and fuel consumption is an important factor regarding the upcoming emission standards and operational expenses. The scavenging process of the two-stroke engine causes scavenging losses. A reduction in hydrocarbon emissions due to scavenging losses can be achieved through inner mixture formation using direct injection (DI). The time frame for fuel vaporization is limited using two-stroke SI engines by the high number of revolutions. A high pressure DI system was used to offer fast and accurate injections. An injection pressure of up to 140 MPa was provided by a common rail system, built out of components normally used in automotive engineering. A standard electromagnetic injector is applied for the fuel injection. This injection unit is dimensioned for multi-point injections in diesel engines.

The two-stroke SI engine is the predominant driving unit in applications that require a high power-to-weight ratio, such as handheld power tools. Regarding the latest regulations in emission limits the main development area is clearly a further reduction of the exhaust emissions. The emissions are directly linked to the combustion processes and the scavenging losses. The optimization of the combustion processes, which represents one of the most challenging fields of research, is still one of the most important keys to enhance the thermal efficiency and reduce exhaust emissions. Regarding future emission regulations for small two-stroke SI engines it is inevitable that the emissions of gases causing the greenhouse effect, like carbon dioxide, need to be reduced. As most small SI engines are carburetted and operate open loop, the mixture formation and the amount of residual gas differs from cycle to cycle [1].

Particle number measurements during different real world and legislative driving cycles show that catalyst heating, cold and transient engine operation cause increased particle number emissions. In this context the quality of mixture formation as a result of injector characteristics, in-cylinder flow, operation & engine parameters and fuel composition is a major factor. The goal of this paper is to evaluate the influence of different biogenic and alkylate fuels on the gaseous and particle number emission behavior during catalyst heating operation on a single-cylinder DISI engine. The engine is operated with a late ignition timing causing a high exhaust enthalpy flow to heat up the catalyst, a slightly lean global air fuel ratio to avoid high hydrocarbon emissions and a late injection right before the ignition to reduce the coefficient of variance of the indicated mean effective pressure.

High frequency ignition (HFI) and conventional transistor coil ignition (TCI) were investigated with an optically accessible single-cylinder research engine to gain fundamental understanding of the chemical reactions taking place prior to the onset of combustion. Instead of generating heat in the gap of a conventional spark plug, a high frequency / high voltage electric field is employed in HFI to form chemical radicals. It is generated using a resonant circuit and sharp metallic tips placed in the combustion chamber. The setup is optimized to cause a so-called corona discharge in which highly energized channels (streamers) are created while avoiding a spark discharge. At a certain energy the number of ionized hydrocarbon molecules becomes sufficient to initiate self-sustained combustion. HFI enables engine operation with highly diluted (by air or EGR) gasoline-air mixtures or at high boost levels due to the lower voltage required.

Modern gasoline direct injection engines with spray-guided combustion processes require a stable and reliable fuel mixture formation as well as an optimal stratification at time of ignition. Due to the limited time for this process the temporal and spatial analysis of the in-cylinder flow field and its influence is of significant interest. The application of a piezo injector with outward opening nozzle and its capability to realize multiple injections within the compression stroke provides additional degrees of freedom for the stratified engine operation. To improve the performance of this combination a detailed knowledge of the in-cylinder flow field and its interaction with the spray propagation during and after multiple injections is essential. The flow field measurements were applied in an optical borescope single-cylinder research engine using a high-speed particle image velocimetry (HSPIV) setup.

The combustion processes optimization is one of the most important factors to enhancing thermal efficiency and reducing exhaust emissions of combustion engines [1; 2]. Future emission regulations for small two-stroke SI engines require that the emissions of gases causing the greenhouse effect, such as carbon dioxide, to be reduced. One possible way to reduce exhaust gas emissions from two-stroke small off-road engines (SORE) is to use biogenic fuels. Because of their nearly closed carbon dioxide circuit, the emissions of carbon dioxide decrease compared to the use of fossil fuels. Also biogenic fuels have a significant influence on the combustion process and thus the emissions of different exhaust gas components may be reduced. Besides greenhouse gases, several other exhaust gas components need to be reduced because of their toxicity to the human health. For example, aromatic hydrocarbons cause dangerous health problems, and can be reduced by using alkylate fuel.

In order to fulfil emission legislation and achieve good drivability of combustion-engine-powered vehicles, information about the air charge and feedback about the engine condition is necessary. In current systems, different sensors are used, e.g. the MAP (manifold air pressure) sensor and a lambda sensor. Aiming at reducing costs, efforts are being made to reduce the number of sensors while still retrieving the necessary information. Various engine speed based functions are state-of-the-art for automotive engines, e.g. for fuel-calibration, misfire-detection etc. Those functions evaluate the engine speed fluctuations during a working cycle induced by combustion. For multiple-cylinder engines, those influences are overlapping, therefore evaluation possibilities are limited. The work presented is based on the effect that at a single-cylinder engine, there is no overlap of combustion influences of various cylinders on the crankshaft.

The emission behaviour of an internal combustion engine under test-bed conditions shows differences to the emission behaviour under real in-use conditions. Because of this fact, the developers of combustion engines and the legislator are focussing on the measurement and optimization of real in-use emissions. To this day, the research, the adjustment of the carburettor and the legislation of small handheld engines is performed under test bench conditions, especially conditioned fuel pressure and temperature, as well as air temperature. Also the engines are laid out for two operation points: rated speed with full open throttle and idle speed. This test-procedure is used for all kinds of handheld off-road applications and does not consider the load profile of the different power tools. Especially applications with transient load profiles, for example chainsaws, work in more than two operating points in real use.

The two-stroke SI engine remains the dominant concept for handheld power tools. Its main advantages are a good power-to-weight ratio, simple mechanical design and low production costs. Because of these reasons, the two-stroke SI engine will remain the dominant engine in such applications for the foreseeable future. Increasingly stringent exhaust emission laws, in conjunction with the drive for more efficiency, have made new scavenging and combustion processes necessary. The main foci are to reduce raw emissions of unburned hydrocarbons via intelligent guidance of the fresh air-fuel mixture and to improve performance to reduce specific emissions. The flow velocity in the electrode gap of the spark plug is of great interest for the ignition of the air-fuel-mixture and the early combustion phase of all kinds of SI engines. In these investigations, the flow velocity in the spark plug gap of a two-stroke gasoline engine with stratified scavenging was measured under various conditions.

Advanced thermal management systems in passenger cars present a possibility to increase efficiency of current and future vehicles. However, a vehicle integrated thermal management of the combustion engine is essential to optimize the overall thermal system. This paper shows results of an experimental heat flux analysis of a state-of-the-art automotive diesel engine with common rail injection, map-controlled thermostat and split cooling system. Measurements on a climatic chamber engine test bench were performed to investigate heat fluxes and energy balance in steady-state operation and during engine warm-up from different engine start temperatures. The analysis includes the influence of the operating point and operating parameters like EGR rate, injection strategy and coolant temperature on the engine energy balance.

Rapeseed oil can be a possible substitute for fossil fuel in Diesel engines. Due to different physical properties of rapeseed oil like higher viscosity and higher compressibility compared to diesel fuel, rapeseed oil cannot be easily used in conventional Diesel engines without modifications. Especially incomplete combustion leads to deposits in the combustion chamber and higher exhaust gas emissions. These unfavorable characteristics are caused primarily by insufficient mixture preparation. The adjustment of the injection system will improve the mixture preparation and the combustion of a Diesel engine, operated with rapeseed oil. The nozzle geometry is the main parameter of the whole injection system chain to realize a better combustion process and so higher efficiency and lower exhaust gas emissions.