Homogeneous charge compression ignition has the potential to significantly reduce NO x emissions, while maintaining a high fuel efficiency. Homogeneous charge compression ignition is characterized by compression-induced autoignition of a lean homogeneous air–fuel mixture. Combustion timing is highly dependent on the in-cylinder state including pressure, temperature and trapped mass. To control homogeneous charge compression ignition combustion, it is necessary to have an accurate representation of the gas exchange process. Currently, microprocessor-based engine control units require that the gas exchange process is linearized around a desired operating point to simplify the model for real-time implementation. This reduces the models’ ability to handle disturbances and limits the flexibility of the model. However, using a field programmable gate array, a detailed simulation of the physical gas exchange process can be implemented in real time. This paper outlines the process of converting physical governing equations to an offline zero-dimensional gas exchange model. The process used to convert this model to a field programmable gate array capable model is described. This model is experimentally validated using a single cylinder research engine with electromagnetic valves to record real-time field programmable gate array gas exchange results and comparing to the offline zero-dimensional physical model. The field programmable gate array model is able to accurately calculate the cylinder temperature and cylinder mass at 0.1 °CA intervals during the gas exchange process for a range of negative valve overlaps, boost conditions and engine speeds making the model useful for future real-time control applications.

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Homogeneous charge compression ignition is a part-load combustion method, which can significantly reduce oxides of nitrogen (NO x) emissions compared to current lean-burn spark ignition engines. The challenge with homogeneous charge compression ignition combustion is the high cyclic variation due to the lack of direct ignition control. A fully variable electromagnetic valve train provides the internal exhaust gas recirculation through negative valve overlap which is required to obtain the necessary thermal energy to enable homogeneous charge compression ignition. This also increases the cyclic coupling as residual gas and unburnt fuel is transferred between cycles through exhaust gas recirculation. To improve combustion stability, an experimentally validated feed-forward water injection controller is presented. Utilizing the low latency and rapid calculation rate of a field programmable gate array, a real-time calculation of residual fuel mass is implemented on a prototyping engine controller. Using this field programmable gate array–based calculation, it is possible to calculate the amount of fuel and the required control interaction during an engine cycle. This controller prevents early rapid combustion following a late combustion cycle using direct water injection to cool the cylinder charge and counter the additional thermal energy from any residual fuel that is transferred between cycles. By cooling the trapped cylinder mass, the upcoming combustion phasing can be delayed to the desired setpoint. The controller was tested at several operating points and showed an improvement in the combustion stability as shown by a reduction in the standard deviation of combustion phasing and indicated mean effective pressure.

CAI (Controlled AutoIgnition) systems, also named HCCI (Homogeneous Charge Compression Ignition), are a promising way to improve gasoline engines. This combustion mode is more efficient than the standard SI (Spark Ignition) combustion and, additionally, it has very low emissions, especially NOx emissions, which represent a source of problems nowadays. The main problem of this combustion mode is the constrained operating range, caused, on the one hand, by the difficulty to ignite the fuel since it has to be autoignited by the control of the mixture reactivity, and, on the other hand, by its high heat release rates, causing high pressure gradients and, in some circumstances, knocking combustion. In this paper, the possibility to use directly injected water into the combustion chamber as a reactivity suppressor in order to extend the constrained load range of CAI operation is evaluated. For

Using life cycle assessment, we explore the conditions under which a fleet-wide blending of OME3–5 with fossil diesel can reduce environmental impacts in terms of CO2, NOx, and soot emissions.

Gasoline Controlled Auto Ignition (GCAI) combustion offers high potential for CO 2 emission reduction, but faces challenges regarding combustion stability and high sensitivity to changing boundary conditions. 1 Combustion chamber recirculation allows a wide operation range, but results in a strong coupling of consecutive cycles 2 due to residuals that are transferred to the subsequent combustion cycle. The cycle coupling leads to phases of unstable operation with reduced efficiency and increased emission levels. 3 State of the art control algorithms use data-driven models of GCAI combustion to achieve cycle-to-cycle control of the process 4 or use offline calibration and optimization. 5 A closed-loop control is proposed and implemented on a rapid control prototyping ECU. The control algorithm continuously calculates the current residual fuel in the combustion chamber. The heat release is observed and compared with the theoretical heat release of the injected fuel mass. The rate of unburned fuel mass transferred to the subsequent cycle is calculated offline by a detailed gas exchange model. Based on this information, the control algorithm adapts the injected fuel quantity for each cycle individually using an inverse injector model. In this article, a concept for decoupling consecutive cycles is presented to reduce the deviations of the indicated mean effective pressure (IMEP) and thus the heat release. Unstable sequences are analyzed in the time domain, and unburned residuals are identified as a strong correlating factor for consecutive cycles. Using real-time cylinder pressure analysis based on a field programmable gate array (FPGA) enables the online calculation of unburned residual fuel. Based on this calculation, the injection of each cycle can be adapted individually to decouple consecutive cycles and avoid unstable operation. The results of the control algorithm and the stabilization of the GCAI combustion are validated using a single cylinder research engine and compared to steady state operation.

The development and validation of detailed simulation models of incylinder combustion, emission formation mechanisms and reaction kinetics in the exhaust system are of crucial importance for the design of future low-emission powertrain concepts. To investigate emission formation mechanisms on one side and to create a solid basis for the validation of simulation methodologies (e.g. 3D-CFD, multidimensional in-cylinder models, etc.) on the other side, specific detailed measurements in the exhaust system are required. In particular, the hydrocarbon (HC) emissions are difficult to be investigated in simulation and experimentally, due to their complex composition and their post-oxidation in the exhaust system.In this work, different emission measurement devices were used to track the emission level and composition at different distances from the cylinder along the exhaust manifold, from the exhaust valve onwards. A fast-FID (FFID) was used to measure the cycle-resolved total-HC (THC) emissions and an ion molecule reaction massspectrometer (IMR-MS) to determine the average concentration of some selected HC components. Conventional exhaust analyzers were used additionally to measure the average levels of the important exhaust gas components (THC, NOx, CO, CO2, O2).The measurements were conducted on a 0.4 l single-cylinder sparkignited (SI) research engine. The effects and cross-effects on emissions of several relevant operating parameters were evaluated. Different result patterns are observed in the different measuring positions. In this work, selected results on the effect of air-to-fuel ratio and spark timing are presented. For the air-fuel-ratio variation, the FFID results show that the THC quenching increases with lean operating condition and the IMR-MS that this increase corresponds to an increase in fuel-HC and a reduction in non-fuel-HC. In the spark timing variation, the trends of THC in the exhaust port and in the exhaust runner suggest the presence of HC oxidation in the exhaust port, due to higher exhaust temperature with retarded combustion. Additionally, the IMR-MS confirm the presence of late and incomplete oxidation with the increase of non-fuel species.