Search Results

Partially Premixed Combustion (PPC) is a combustion concept which aims to provide combustion with low smoke and NOx with high thermal efficiency. Extending the ignition delay to enhance the premixing, avoiding spray-driven combustion and controlling the combustion temperature at an optimum level through use of suitable lambda and EGR levels have been recognized as key factors to achieve such a combustion. Fuels with high ignitability resistance have been proven to be a useful to extend the ignition delay. In this work pure ethanol has been used as a PPC fuel. The objective of this research was initially to investigate the required operating conditions for PPC with ethanol. Additionally, a sensitivity analysis was performed to understand how the required parameters for ethanol PPC such as lambda, EGR rate, injection pressure and inlet temperature influence the combustion in terms of controllability, stability, emissions (i.e.

In the automotive industry, the piezo-based in-cylinder pressure sensor is getting commercialized and used in production vehicles. For example, the pressure sensor offers the opportunity to design algorithms for estimation of engine emissions, such as soot and NO , during a combustion cycle. In this paper a zero-dimensional NO model for a diesel engine is implemented that will be used in real time. The model is based on the thermal NO formation and the Zeldovich mechanism using two non-geometrical zones: burned and unburned zone. The influence of EGR on combustion temperature was modeled using a well-known thermodynamic identity where specific heat at constant pressure is included. Specific heat will vary with temperature and the gas composition. The model was implemented in LabVIEW using tools specific for an FPGA (Field-Programmable Gate Array).

A diesel engine developed for an international market must be able to run on different fuels considering the diesel fuel qualities and the increasing selection of biofuels in the world. This leads to the question of how different fuels perform relative to a standard diesel fuel when not changing the hardware settings. In this study five fuels (Japanese diesel, MK3, EN590 with 10% RME, EN590 with 30% RME and pure RME) have been compared to a reference diesel fuel (Swedish MK1) when run on three different speeds and three different loads at each speed. The experiments are run on a Scania 13l Euro5 engine with standard settings for Swedish MK1 diesel. In general the differences were not large between the fuels. NO x usually increased compared to MK1 and then soot decreased as would be expected. The combustion efficiency increased with increased RME contents of the fuel but the indicated efficiency was not influenced by RME except for at higher loads.

In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio.

Typically, the combustion in an internal combustion engine is open-loop controlled. The introduction of a cylinder pressure sensor opens the possibility to introduce a virtual combustion sensor. This virtual sensor is a possible enabler for closed-loop combustion control and thus the possibility to counteract the effects of engine part to part variation, component ageing and fuel quality diversity. The extent to which these effects can be counteracted is determined by the detection limits of the virtual combustion sensor. To determine the limitation of the virtual combustion sensor, a virtual combustion sensor system was implemented based on a one-zone heat-release analysis, including the signal processing of the pressure sensor input. The typical error sources in a heavy-duty engine were identified and quantified. The virtual combustion sensor system was presented with flawed signals and the sensor’s sensitivities to the errors were quantified.

The emission control in heavy-duty vehicles today is based on predefined injection strategies and after-treatment systems such as SCR (selective catalytic reduction) and DPF (diesel particulate filter). State-of-the-art engine control is presently based on cycle-to-cycle resolution. The introduction of the crank angle resolved pressure measurement, from a piezo-based pressure sensor, enables the possibility to control the fuel injection based on combustion feedback while the combustion is occurring. In this paper a study is presented on the possibility to control NOx (nitrogen oxides) formation with a crank angle resolved NOx estimator as feedback. The estimator and the injection control are implemented on an FPGA (Field-Programmable Gate Array) to manage the inherent time constraints. The FPGA is integrated with the rest of the engine control system for injection control and measurement.

After-oxidation in Heavy Duty (HD) diesel combustion is of paramount importance for emissions out from the engine. During diffusion diesel combustion, lots of particulate matter (PM) is created. Most of the PM are combusted during the after-oxidation part of the combustion. Still some of the PM is not, especially during an engine transient at low lambda. To enhance the PM oxidation in the late engine cycle, swirl together with high injection pressure can be implemented to increase in-cylinder turbulence at different stages in the cycle. Historically swirl is known to reduce soot particulates. It has also been shown, that with today's high injection pressures, can be combined with swirl to reduce PM at an, for example, engine transient. The mechanism why the PM engine out is reduced also at high injection pressures is however not so well understood.

In-cylinder flow pattern has been examined experimentally in a heavy duty optical diesel engine and simulated with CFD code during the combustion and the post-oxidation phase. Mean swirling velocity field and its evolution were extracted from optical tests with combustion image velocimetry (CIV). It is known that the post-oxidation period has great impact on the soot emissions. Lately it has been shown in swirling combustion systems with high injection pressures, that the remaining swirling vortex in the post-oxidation phase deviates strongly from solid body rotation. Solid body rotation can only be assumed to be the case before fuel injection. In the studied cases the tangential velocity is higher in the centre of the piston bowl compared to the outer region of the bowl. The used CIV method is closely related to the PIV technique, but makes it possible to extract flow pattern during combustion at full load in an optical diesel engine.

Energy dissipation due to micro-slip in joints is the primary source of damping in many vehicle and space structures. This paper presents results on how the surface topology may be modified to increase the energy dissipation in joints. An analytical solution for general forms of contact pressure of a one-dimensional micro-slip problem is presented. The solution indicates how the contact pressure should be distributed to maximize the energy dissipation. Two dimensional contact pressures are optimized using finite element methods in combination with numerical optimization methods and the results are used to modify the surface topology in bolted joints in order to increase the energy dissipation during loading. The predicted increase of energy dissipation is validated with physical testing. A direct result of the study is a washer with varying thickness increasing the energy dissipation in joints and hence the structural damping of joined structures.

Global warming and climate change have led to a greater interest in the implementation of biofuels in internal combustion engines. In spark ignited engines, biofuels have been shown to improve efficiency and knock resistance while decreasing emissions of unburned hydrocarbons, carbon monoxide and particles. This study investigates the effect of biofuels on SI engine combustion through a graphical compilation of previously reported results. Experimental data from 88 articles were used to evaluate the trends of the addition of different biofuels in gasoline. Graphs illustrating engine performance, combustion phasing and emissions are presented in conjunction with data on the physiochemical properties of each biofuel component to understand the observed trends. Internal combustion engines have the ability to handle a wide variety of fuels resulting in a broad range of biofuel candidates.

A method developed in SAE 2019-01-0058 to correct for deviations from quasi-steady exhaust valve flow is implemented on a single-cylinder GT-Power model and the effects on pumping work and blowdown pulse characteristics are investigated. The valve flow area is always reduced compared to the reference quasi-steady case. It decreases with higher pressure ratios over the valve and increases with higher engines speeds. The reduced flow area increases pumping work with load and engine speed, though primarily with engine speed. The magnitude of the blowdown pulse is reduced and the peak is shifted to a later crank angle.

Thermal Barrier Coatings (TBCs) may be used on the inner surfaces of exhaust manifolds in heavy-duty diesel engines to improve the fuel efficiency and prolong the life of the component. The coatings need to have a long thermal cyclic life and also be able to reduce the temperature in the substrate material. A lower temperature of the substrate material reduces the oxidation rate and has a positive influence on the thermo-mechanical fatigue life. A test rig for evaluating these properties for several different coatings simultaneously in the correct environment was developed and tested for two different TBCs and one oxidation-resistant coating. Exhausts were redirected from a diesel engine and led through a series of coated pipes. These pipes were thermally cycled by alternating the temperature of the exhausts. Initial damage in the form of cracks within the top coats of the TBCs was found after cycling 150 times between 50°C and 530°C.

With increasing demands to reduce fuel consumption and CO2 emissions, it is necessary to recover waste heat from modern Heavy Duty (HD) truck engines. Organic Rankine Cycle (ORC) has been acknowledged as one of the most effective systems for Waste Heat Recovery (WHR) due to its simplicity, reliability and improved overall efficiency. The expander and working fluid used in ORC WHR greatly impact the overall performance of an integrated engine and WHR system. This paper presents the effects of volumetric expanders on the ORC WHR system of a long haulage HD truck engine at a steady-state engine operating point chosen from a real-time road data. Performance of a long haulage HD truck engine is analyzed, based on the choice of three volumetric expanders for its WHR system, using their actual performance values. The expanders are: an oil-free open-drive scroll, a hermetic scroll and an axial piston expander with working fluids R123, R245fa and ethanol, respectively.

Typically the combustion in a direct injected compression ignited internal combustion engine is open-loop controlled. The introduction of a cylinder pressure sensor opens up the possibility of a virtual combustion sensor which could enable closed-loop combustion control and thus the potential to counteract effects such as engine part to part variation, component ageing and fuel quality diversity. Closed-loop combustion control requires precise, robust and preferably cheap sensors. This paper presents a virtual cylinder pressure sensor based on the signal from the inexpensive but well proven knock sensor. The method used to convert the knock sensor signal into a pressure estimate included the stages: Phase correcting the raw signal, Filtering the raw signal, Scaling the signal to known thermodynamic laws and provided engine sensors signals and Reconstructing parts of the signal with other known models and assumptions.

Factors influencing pilot-injection combustion were investigated using heat release analysis in a heavy-duty diesel engine fuelled with standard diesel fuel. Combinations of pilot-injection parameters i.e. pilot start of injection, pilot mass, pilot-main injection separation, and rail pressure were studied for various operating conditions and combustion phases. An experiment was designed to investigate the factors influencing the combustion of the pilot. For improved injected fuel-mass accuracy, reference data for the injectors were measured in a spray rig prior to the engine experiments. Results show that cycle-to-cycle variations and cylinder-to-cylinder variations influence pilot autoignition and the amount of heat released. Rail pressure and injected pilot mass affect the obtained variance depending on the chamber conditions. The obtained combustion modes (premixed, diffusive) of pilot combustion were found to be a function of the injected mass and rail pressure.

The European Union’s 2020 target aims to be producing 20 % of its energy from renewable sources by 2020, to achieve a 20 % reduction in greenhouse gas emissions and a 20 % improvement in energy efficiency compared to 1990 levels. To reach these goals, the energy consumption has to decrease which results in reduction of the emissions. The transport sector is the second largest energy consumer in the EU, responsible for 25 % of the emissions of greenhouse gases caused by the low efficiency (<40 %) of combustion engines. Much work has been done to improve that efficiency but there is still a large amount of fuel energy that converts to heat and escapes to the ambient atmosphere through the exhaust system. Taking advantage of thermoelectricity, the heat can be recovered, improving the fuel economy.