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Finding the correct top dead center (TDC) offset for an internal combustion engine is harder than it seems. This paper introduces a novel method to find the TDC offset based on a simple assumption that the heat loss power through the combustion chamber walls is constant for motored cycles in a narrow crank angle interval around TDC. The proposed method uses nonlinear least squares optimization to
It is tractable to increase the torque for an HCCI engine and one way is to add a turbocharger. Operating in HCCI mode requires accurate control of the combustion phasing, CA50. The higher the engine torque, the narrower the CA50 window becomes where HCCI operation is maintained. As the CA50 varies stochastically between cycles this requires improved CA50 control for turbo HCCI engines. The main f
By using a turbo the operating range of the HCCI engine can be increased, but at the expense of increased controller complexity. The dynamics the turbo introduces in the intake and the exhaust manifolds, have a large impact on the in-cylinder mixture temperature, pressure and finally the combustion phasing. To compensate for this and to maintain desired combustion phasing, precise control of the n
For diesel engines the major exhaust problem is particulate matter and NOx emissions. To reduce NOx, exhaust gas recirculation (EGR) is often used. The behavior of the EGR-level will therefore influence the emissions and it is therefore valuable to keep track of the EGR-level. Especially during transients it is difficult to predict how the EGR-level varies. In this paper the CO2-level in the intak
Partially Premixed Combustion (PPC) is a combustion concept by which it is possible to get low smoke and NOx emissions simultaneously. PPC requires high EGR levels and injection timings sufficiently early or late to extend the ignition delay so that air and fuel mix extensively prior to combustion. This paper investigates the operating region of single injection diesel PPC in a multi cylinder heav
In this paper, we review one of the oldest paradigms used in animal cognition: the detour paradigm. The paradigm presents the subject with a situation where a direct route to the goal is blocked and a detour must be made to reach it. Often being an ecologically valid and a versatile tool, the detour paradigm has been used to study diverse cognitive skills like insight, social learning, inhibitory
PhD training in academic labs offers the foundation for the production of frontier knowledge workers, indispensable for the modern knowledge-based society. Nonetheless, our understanding on PhD training has been insufficient due to limited access to the inside of academic labs. Furthermore, early careers of PhD graduates are often difficult to follow, which makes the evaluation of training outcome
I vår artikel vill vi med utgångspunkt i tröskelbegreppet (Perkins 1999) undersöka moment inom grammatiken som är svåra för studenterna att tillägna sig, men som är helt avgörande för förståelse och progression. I första hand utgår vi från en analys av underkända tentamina i ämnet svenska. Analysen pekar ut tre problemområden: svårigheter med att skilja mellan betydelse, form och funktion, med att
In this paper we explore how different ways of training communication skills can be successfully implemented in higher education, and which effects these activities may have on science students’ learning. Using content analysis, we studied a material consisting of 34 reports, written by 70 academic science teachers, as part of a teacher-training course on communication in science higher education.
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 3
Natural gas and hydrogen enriched natural gas has been tested as fuels together with diesel oil and RME in a single cylinder Scania research engine. The gas was introduced as port injection while the diesel was introduced as early direct injection. Because the gas was premixed with air before combustion and the diesel was injected early in the compression stroke, the engine ran close to HCCI mode.
In HCCI you do not have the same control of the combustion like in SI and Diesel engines. Controlling the start of a combustion event is a difficult task and requires feedback from previous cycles. This feedback can be retrieved from ion current measurements. By applying a voltage over the spark gap, ions will lead a current and a signal that represents the combustion in the cylinder will be retri
Utilization of an ethanol driven, combustion-based power generator promises high-efficiency combustion in diesel-like engines and avoids problems connected to shrinking supplies of fossil fuels since fuels like ethanol or dimethyl ether can be produced from renewable resources. Fuel injection into such generator through a piezoelectric micro mass flow controller (MMFC) features low power consumpti
A piezoelectric micro mass flow controller (MMFC) for liquid fuel injection into a mini-HCCI-motor for power generation is introduced. Piezoelectric actuation ensures negligible power consumption for fuel injection allowing self-sustaining operation. A pressurized fuel tank is connected to the MMFC which is designed like a normally-closed, on-/off-operating valve. Integrated piezoresistors are use
Autoignition of a homogeneous mixture is very sensitive to operating conditions, therefore fast control is necessary for reliable operation. There exists several means to control the combustion phasing of an Homogeneous Charge Compression Ignition (HCCI) engine, but most of the presented controlled HCCI result has been performed with single-input single-output controllers. In order to fully operat
Studies of relations binding ruled and ruler over the form and content of revenue assessment during the colonial era are not lacking. Rather, the intellectual challenge lies in ascertaining the degree to which the relevant economic institutions of the subjected regions in southern Asia constituted continuity of tradition, modifications thereof, or completely alien constructs. Meeting that challeng
This work has focused on studying the in-cylinder pressure fluctuations caused by rapid HCCI combustion and determine what they consist of. Inhomogeneous autoignition sets up pressure waves traversing the combustion chamber. These pressure waves induce high gas velocities which causes increased heat transfer to the walls or in worst case engine damage. In order to study the pressure fluctuations a
In this essay, we explore and discuss current practices of source critique. In our empirical analysis of a sample of interview-based studies, we find that few studies show a careful and reflective stance toward their sources. In the majority of cases, we discern a tendency to either ignore basic issues of the trustworthiness of interview material or produce technical descriptions which seem to hav
Studies on the intergenerational transmission of human capital usually assume a one-way spillover from parents to children. However, children may also affect their parents’ human capital. Using exogenous variation in education, arising from a Swedish compulsory schooling reform in the 1950s and 1960s, we address this question by studying the causal effect of children's schooling on their parents’
