No description available.

No description available.

Variable compression engines are a mean to meet the demand on lower fuel consumption. A high compression ratio results in high engine efficiency, but also increases the knock tendency. On conventional engines with fixed compression ratio, knock is avoided by retarding the ignition angle. The variable compression engine offers an extra dimension in knock control, since both ignition angle and compression ratio can be adjusted. The central question is thus for what combination of compression ratio and ignition angle the maximum efficiency is achieved, considering the set of compression ratios and ignition angles that give a sufficiently low knock intensity. Four knock detection methods are proposed, compared and evaluated with respect to robustness for noise and choices of parameter values. Three of the knock detectors are categorised as on-line, and are designed for giving feedback about knock occurrence to the engine control unit. The methods can determine both whether or not knock is present and the crank angle at knock onset. A study of the relationship between knock oscillation properties and knock-onset is performed. It is concluded that the logarithm of the normalised knock energy depends almost linearly on the rate of knock occurrence. A new formulation of multi-zone engine models is presented. The formulation makes it easy to increase or decrease the number of zones during the simulation. One of many possible applications is the investigation of engine efficiency. An analysis of experimental data shows how the engine efficiency changes with compression ratio and ignition angle. An engine torque model is developed and validated, from which the optimal choice of compression ratio and ignition angle can be calculated with high accuracy.

Surface temperature and heat flux measurements were made in a single cylinder SI engine piston when uncoated and with two different surface coatings: a metal TBC and YSZ. A new thermocouple was developed to accurately measure surface temperatures. The engine was operated in a standard full load mode and a knock promoting mode featuring heated intake air and advanced spark timing. Cylinder pressures were measured to quantify knock. It was found that average heat flux into the piston substrate was 33 % higher with the metal TBC and unchanged with the YSZ relative to the uncoated surface. The increase with the metal TBC was attributed to its surface roughness. However, the metal TBC and YSZ reduced peak heat flux by 69 and 77 %, respectively. Both the metal TBC and YSZ reduced knock compared to the uncoated surface. After testing, the metal TBC was undamaged and the YSZ was slightly chipped.

Surface temperature and heat flux measurements were made in a single cylinder SI engine piston when uncoated and with two different surface coatings: a metal TBC and YSZ. A new thermocouple was developed to accurately measure surface temperatures. The engine was operated in a standard full load mode and a knock promoting mode featuring heated intake air and advanced spark timing. Cylinder pressures were measured to quantify knock. It was found that average heat flux into the piston substrate was 33 % higher with the metal TBC and unchanged with the YSZ relative to the uncoated surface. The increase with the metal TBC was attributed to its surface roughness. However, the metal TBC and YSZ reduced peak heat flux by 69 and 77 %, respectively. Both the metal TBC and YSZ reduced knock compared to the uncoated surface. After testing, the metal TBC was undamaged and the YSZ was slightly chipped.

No description available.

No description available.

This report is a theoretical study of the potential an ICE (internal combustion engine) has when combined with the load case of a high-performance series hybrid drivetrain. It breaks down the different theoretical variables that affect engine efficiency and possible limitations that arise. The report then moves on to specifying the current emerging technologies associated with increasing engine efficiency such as active, and passive prechamber ignition. The different technologies strengths and weaknesses were then compared with each other to decide the best strategies and technologies to move forward with. Here efficiency gain potential was compared to price, performance and complexity. The different technologies were compared in two separate steps firstly the technologies were compared individually, then the best systems were compared to different engine configurations in an iterative process. Here the most balanced solution was found using a passive prechamber to allow higher compression ratio while allowing better timing control. This was later combined with a Miller cycle strategy resulting in a theoretical efficiency improvement of ~8%. This would potentially allow a high performance vehicle to match a midrange diesel engine in fuel economy.

In this work CFD was used to simulate the flow through a novel valve design for internal combustion engines. CFD is numerical method for simulating the behaviour of systems involving flow processes. A FEM was used for solving the equations. Literature on the topic was studied to gain an understanding of the performance limiters on the Internal combustion engine. This understanding was used to set up models that better would mimic physical phenomena compared to previous studies. The models gave plausible results as to fluid velocities and in-cylinder flow patterns. Comsol Multiphysics 4.1 was used for the computations.

The mean value engine model (MVEM) is a mathematical model derived from basic physical principles such as conservation of mass and energy equations. Although the MVEM is based on some simplified assumptions and time averaged combustion engine parameters, it models the engine with a reasonable approximation and gives a satisfactory amount of information about the physics of the fluid energy passing through an engine system. MVEM can predict an engine’s main external variables such as crankshaft speed and manifold pressure, and important internal variables, such as volumetric and thermal efficiencies. Usually, the differential equations used in MVEM will predict fuel film flow, manifold pressure, and crankshaft speed. Because of its simplicity and short simulation time, the MVEM is widely used for engine control development. A mean value engine based on mathematical and parametric equations has recently been developed in the new MapleSim software. The model consists of three main components: the throttle body, the manifold, and the engine. The new MVEM uses combinations of causal and acausal components along with lookup tables and parametric equations. Adjusting the parameters allows the model to be used for new engines of interest. The model is forward-looking and so benefits from both Maple’s powerful mathematical tool and Modelica’s modern equation-based language. A set of throttle angle and mass flow data is used to find the throttle angle function, and to validate the throttle mass flow rates obtained from the model and the experiment.