Charles McCartan

The technical merits of turbogenerating shown through the design, validation and implementation of a one-dimensional engine model

Turbocompounding is the process of recovering a proportion of an engine’s fuel energy that would otherwise be lost in the exhaust process and adding it to the output power. This was first seen in the 1930s and is carried out by coupling an exhaust gas turbine to the crankshaft of a reciprocating engine. It has since been recognised that coupling the power turbine to an electrical generator instead of the crankshaft has the potential to reduce the fuel consumption further with the added flexibility of being able to decide how this recovered energy is used. The electricity generated can be used in automotive applications to assist the crankshaft using a flywheel motor generator or to power ancillaries that would otherwise have run off the crankshaft. In the case of stationary power plants, it can assist the electrical power output. Decoupling the power turbine from the crankshaft and coupling it to a generator allows the power electronics to control the turbine speed independently in order to optimise the specific fuel consumption for different engine operating conditions. This method of energy recapture is termed ‘turbogenerating’. This paper gives a brief history of turbocompounding and its thermodynamic merits. It then moves on to give an account of the validation of a turbogenerated engine model. The model is then used to investigate what needs to be done to an engine when a turbogenerator is installed. The engine being modelled is used for stationary power generation and is fuelled by an induced biogas with a small portion of palm oil being injected into the cylinder to initiate combustion by compression ignition. From these investigations, optimum settings were found that result in a 10.90% improvement in overall efficiency. These savings relate to the same engine without a turbogenerator installed operating with fixed fuelling.

Application of a Generic Curriculum Change Management Process to Motivate and Excite Students

Abstract The School of Mechanical and Aerospace Engineering at Queen’s University Belfast is committed to enhancing the quality of student learning. A plan to implement curriculum change around this goal has been formulated and is already several years underway. A specific part of the plan involved instigating a first year introductory module to engage the students in the practice of their engineering discipline. The complicated nature of devising this type of module with regard to objectives, resources, timeframe and the number of students involved meant that a very systematic approach had to be adopted. This paper presents the simple but definitive change management process that facilitated the creation of a first year Introduction to Engineering module. The generic nature of this process is described and its application to other facets of curriculum change is discussed. Within this process the importance of collaboration to establish a forward momentum is emphasised. This enables academic staff to progress as a group and build curriculum development based on their own experiences, expertise and established practice.

Investigations Into the Performance of a Turbogenerated Biogas Engine During Speed Transients

Turbogenerating is a form of turbocompounding whereby a Turbogenerator is placed in the exhaust stream of an internal combustion engine. The Turbogenerator converts a portion of the expelled energy in the exhaust gas into electricity which can then be used to supplement the crankshaft power. Previous investigations have shown how the addition of a Turbogenerator can increase the system efficiency by up to 9%. However, these investigations pertain to the engine system operating at one fixed engine speed. The purpose of this paper is to investigate how the system and in particular the Turbogenerator operate during engine speed transients. On turbocharged engines, turbocharger lag is an issue. With the addition of a Turbogenerator, these issues can be somewhat alleviated. This is done by altering the speed at which the Turbogenerator operates during the engine’s speed transient. During the transients, the Turbogenerator can be thought to act in a similar manner to a variable geometry turbine where its speed can cause a change in the turbocharger turbine’s pressure ratio. This paper shows that by adding a Turbogenerator to a turbocharged engine the transient performance can be enhanced. This enhancement is shown by comparing the turbogenerated engine to a similar turbocharged engine. When comparing the two engines, it can be seen that the addition of a Turbogenerator can reduce the time taken to reach full power by up to 7% whilst at the same time, improve overall efficiency by 7.1% during the engine speed transient.Copyright

AN EVALUATION OF ACTIVE LEARNING STRATEGIES APPLIED TO ENGINEERING MATHEMATICS

An engineering mathematics module has been developed and implemented to promote deeper learning using the CDIO methodology. It conforms to several CDIO Standards and also seeks to develop personal, interpersonal and professional skills through an active and interactive learning paradigm. This paper discusses the content, pedagogy and efficacy of the module in relation to student motivation, engagement and attainment over a three year period. It is shown that such an approach is successful in this regard.

Drivetrain Effects on Small Engine Performance

Presented is a study that expands the body of knowledge on the effect of in-cycle speed fluctuations on performance of small engines. It uses the methods developed previously by Callahan, et al. (1) to examine a variety of two-stroke engines and one four-stroke engine. The two-stroke engines were: a high performance single-cylinder, a low performance single-cylinder, a high performance multi-cylinder, and a medium performance multi-cylinder. The four-stroke engine was a high performance single-cylinder unit. Each engine was modeled in Virtual Engines, which is a fully detailed one-dimensional thermodynamic engine simulator. Measured or predicted in-cycle speed data were input into the engine models. Predicted performance changes due to drivetrain effects are shown in each case, and conclusions are drawn from those results. The simulations for the high performance single-cylinder two-stroke engine predicted significant in-cycle crankshaft speed fluctuation amplitudes and significant changes in performance when the fluctuations were input into the engine model. This was validated experimentally on a firing test engine based on a Yamaha YZ250. The four-stroke engine showed significant changes in predicted performance compared to the prediction with zero speed fluctuation assumed in the model. Measured speed fluctuations from a firing Yamaha YZ400F engine were applied to the simulation in addition to data from a simple free mass model. Both methods predicted similar fluctuation profiles and changes in performance. It is shown that the gear reduction between the crankshaft and clutch allowed for this similar behavior. The multi-cylinder, high performance two-stroke engine also showed significant changes in performance, in this case depending on the firing configuration. The low output two-stroke engine simulation showed only a negligible change in performance in spite of high amplitude speed fluctuations. This was due to its flat torque versus speed characteristic. The medium performance multi-cylinder two-stroke engine also showed only a negligible change in performance, in this case due to a relatively high inertia rotating assembly and multiple cylinder firing events within the revolution. These smoothed the net torque pulsations and reduced the amplitude of the speed fluctuation itself.

Camshaft Design for an Inlet-Restricted FSAE Engine

ABSTRACT Restricting the flow rate of air to the intake manifold is a convenient and popular method used by several motor sport disciplines to regulate engine performance. This principle is applied in the Formula SAE and Formula Student competitions, the rules of which stipulate that all the air entering the engine must pass though a 20mm diameter orifice. The restriction acts as a partially closed throttle which generates a vacuum in the inlet plenum. During the valve overlap period of the cycle, which may be as much as 100 volume of exhaust gas therefore increasing high-spe degrees crank angle in the motorcycle engines used by most FSAE competitors, this vacuum causes reverse flow of exhaust gas into the intake runners. This, in turn, reduces the amount of fresh air entering the cylinder during the subsequent intake stroke and therefore reduces the torque produced. This effect is particularly noticeable at medium engine speeds when the time available for reverse flow is greater than at the peak torque speed. The objective of the study described in this paper was to mitigate the reverse flow effect by reducing the duration of the valve overlap period. A thermodynamic model of the Yamaha YZF R6 engine was developed for this purpose and validated using cycle-averaged and crank-angle-resolved test data. The resulting model was then used to find the optimum values of lift, duration and timing for both the intake and exhaust valves. The camshafts required to give these valve lift profiles were designed using valve train analysis software. This process included a consideration of the dynamic forces encountered by the valve train and ensured that the resulting stresses remained within safe limits. The new camshafts increased the torque output by up to 30% at medium engine speeds, without reducing the high-speed torque, and therefore significantly improved the vehicle drivability.

The Transition into University: What Engineering Students Know

The overall aim of this preliminary project is to develop a set of web-based diagnostic and support tools designed to identify more clearly the attributes of students entering engineering programmes in 2010 and to support their transition into university.

Peer Rating for Feedback in Group Projects

Analysis of best practice and introduction of improved procedures for proving feedback to students carrying out group projects. The procedures include a significant amount of peer rating and individual interviews which aim to separate the development of personal and professional skills from the assesment of project deliverables.

Collaborative quality enhancement in engineering education: an overview of operational models at a programme level

ABSTRACT This article discusses the tension between quality assurance and quality enhancement in engineering education at a programme level. It acknowledges that accreditation has evolved for many years, but does not agilely support innovation or implement changes in educational programmes. Existing quality assurance systems, institutional collaboration networks, as well as new innovative quality enhancement models and processes are described, contrasted and synthesised. Quality enhancement is analysed based on its function as a source of inspiration and dissemination of good practice. The article reflects on a novel and more collaborative approach to quality enhancement, built on the foundations of specific pedagogical standards and rubrics (e.g. CDIO). One solution leading to real continuous quality enhancement could be flexible and agile evaluation processes. These are founded on measurement and rating frameworks and complemented with quality assurance for engineering education. Incremental enhancement is based on relevant needs identified collaboratively between programmes.