This work focuses on the cooling of diesel engines. Facing heavy constraints such as emissions control or fossil energy management, political leaders are forcing car manufacturers to drastically reduce the fuel consumption of passenger vehicles. For instance, in Europe, this fuel consumption has to reach 120 g CO2 km by 2012, namely 25 % reduction from today's level. Such objectives can only be reached with an optimization of all engines components from injection strategies to power steering. A classical energy balance of an internal combustion engine shows four main losses: enthalpy losses at the exhaust, heat transfer to the cylinder walls, friction losses and external devices driving. An optimized cooling will improve three of them: the heat transfer losses by increasing the cylinder walls temperature, the friction losses by reducing the oil viscosity and the coolant pump power consumption. A model is rst built to simulate the engine thermal behavior from the combustion itself to the temperatures of thedierent engine components. It is composed by two models with different time scales. First, a thermodynamic model computes the in cylinder pressure and temperature as well as the heat flows for each crank angle. These heat flows are the main input parameters for the second model: the nodal one. This last model computes all the engine components temperatures according to the nodal model theory. The cylinder walls temperature is then given back to the thermodynamic model to compute the heat flows. The models are then validated through test bench measurements giving excellent results for both Mean Effective Pressure and fluids (coolant and oil) temperatures. The used engine is a 1.9l displacement turbocharged piston engine equipped with an in-cylinder pressure sensor for the thermodynamic model validation and thermocouples for the nodal model validation. The model is then used to optimize the coolant mass flow rate as a function of the engine temperature level. Simulations have been done for both stationary conditions with effciency improvement up to 7% for specific points (low load, high engine speed) and transient ones with a heating time improvement of about 2000s. This gains are then validated on the test bench showing again good agreement.

Advances in piston engine technology, coupled with high costs of turbine engines have led many general aviation manufacturers to explore the use of piston engines in their smaller vehicles. However, very few engine models are available to analyze piston engine performance. Consequently, designers using vehicle synthesis programs are unable to accurately predict vehicle performance when piston engines are used. This thesis documents the development of a comprehensive, thermodynamics based performance model that meets that need. The first part of this thesis details the basics of piston engine operation, including component geometry and the four stroke engine cycle. Next, the author analyzes the critical components of engine performance, including engine work and power. In developing the engine performance model the Ideal Engine Cycles are discussed. The cold air and fuel-air working fluid models are discussed, along with the types of combustion models, including the Otto Cycle, Diesel Cycle, and the Dual Cycle. Two performance models are generated using the Constant Volume Ideal Engine Cycle: an Ideal Gas Standard Cycle, and a Fuel-Air Cycle. The Ideal Gas Standard Cycle is useful for parametric analysis but lacks the accuracy required for performance calculations. The Fuel-Air Cycle, however, more accurately models the engine cycle and is selected as the basis for the computer program. In developing the computer program the thermodynamic charts used in the Fuel-Air Cycle calculations must be reproduced. To accomplish this, the NASA Chemical Equilibrium Application (CEA) program is integrated into a parent VBA based computer code to provide thermodynamic state point data. Finally, the computer program is correlated to the performance of an existing aviation engine to validate the model.

The present research investigates the details of mixture preparation and combustion in a two-stroke, small-scale research engine with a numerical methodology based on large eddy simulation (LES) technique. A major motivation to study such small-scale engines is their potential use in applications requiring portable power sources with high power density. The investigated research engine has a rectangular planform with a thickness very close to quenching limits of typical hydrocarbon fuels. As such, the combustor has a high aspect ratio (defined as the ratio of surface area to volume) that makes it different than the conventional engines which typically have small aspect ratios to avoid intense heat losses from the combustor in the bulk flame propagation period. In most other aspects, this engine involves all the main characteristics of traditional reciprocating engines. A previous experimental work has identified some major design problems and demonstrated the feasibility of cyclic combustion in the high aspect ratio combustor. Because of the difficulty of carrying out experimental studies in such small devices, resolving all flow structures and completely characterizing the flame propagation have been an enormously challenging task. The numerical methodology developed in this work attempts to complement these previous studies by providing a complete evolution of flow variables. Results of the present study demonstrated strengths of the proposed methodology in revealing physical processes occurring in a typical operation of the high aspect ratio combustor. For example, in the scavenging phase, the dominant flow structure is a tumble vortex that forms due to the high velocity reactant jet (premixed) interacting with the walls of the combustor. LES gives the complete evolution of this flow structure, from its beginning to its eventual decay after the scavenging period is over. In addition, LES is able to predict the interaction between the bulk flow at top dead center (TDC) and the turbulent flame propagation. The success of this depends on the ability of the model in predicting turbulent flow structure including its length and velocity scales.

A rolling piston engine, operating according to a novel thermodynamic cycle is designed. Thermodynamic and structural analysis of this novel engine is carried out and thermodynamic and structural variables of the engine were calculated. The losses in the engine, friction and leakage were calculated and their effects on the engine were demonstrated.

People today increasingly use software utilities which help create ‘to-do’ lists or reminders to stay efficient and productive. This has spurred a new industry into designing products for Business Management, Project Planning and Schedule Management on web and device platforms. However, these tools are either designed for novices or industrial level managers. A large number of individuals fall in between; their projects require intensive planning but not at the level of industrial projects. To address this category of users, I propose BusyBeeTaskManager, a web-based application that helps visually plan projects and efficiently communicate progress within the team. The user interface is designed for novice users but features such as document sharing, task dependency graph and automatic task updates allow users to carry outsophisticated team-based projects. / text

This study examined the performance of a residential micro–cogeneration system based on a Stirling engine and fuelled by diesel and ethanol. An extensive number of engine tests were conducted to ensure highly accurate and reproducible measurement techniques. Appropriate energy efficiencies were determined by performing an energy balance for each fuel. Particulate emissions were measured with an isokinetic particulate sampler, while a flame ionization detector was used to monitor unburned hydrocarbon emissions. Carbon monoxide, nitric oxide, nitrogen dioxide, carbon dioxide, water, formaldehyde, acetaldehyde and methane emissions were measured using a Fourier transform infrared spectrometer. When powered by ethanol, the system had slightly higher thermal efficiency, slightly lower power efficiency and considerable reductions in emission levels during steady state operation. To further study engine behaviour, parametric studies on primary engine set points, including coolant temperature and exhaust temperature, were also conducted.

This study examined the performance of a residential micro–cogeneration system based on a Stirling engine and fuelled by diesel and ethanol. An extensive number of engine tests were conducted to ensure highly accurate and reproducible measurement techniques. Appropriate energy efficiencies were determined by performing an energy balance for each fuel. Particulate emissions were measured with an isokinetic particulate sampler, while a flame ionization detector was used to monitor unburned hydrocarbon emissions. Carbon monoxide, nitric oxide, nitrogen dioxide, carbon dioxide, water, formaldehyde, acetaldehyde and methane emissions were measured using a Fourier transform infrared spectrometer. When powered by ethanol, the system had slightly higher thermal efficiency, slightly lower power efficiency and considerable reductions in emission levels during steady state operation. To further study engine behaviour, parametric studies on primary engine set points, including coolant temperature and exhaust temperature, were also conducted.

An innovative two-stroke engine has been under development at Queen’s University. Traditional crankcase-scavenged two-stroke engines have laboured to meet emissions standards and achieve fuel economy comparable to four-stroke engines. The engine in question makes use of a modified Eaton-type supercharger to enable air-only scavenging, with this it utilizes direct fuel injection which occurs after the exhaust ports have closed, these two elements combine to eliminate the combustion of lubricating oil in the cylinder and short-circuiting of the fuel-air mixture into the exhaust. By having passive check valves in the cylinder head to regulate the inflow of scavenging air, and exhaust ports located near bottom centre this results in a top-down uniflow-scavenged configuration, as well as retaining a simplistic engine design. In the two-stroke cycle, using the intake charge to replace the combustion products with fresh air during scavenging is critical to engine performance. In this engine the scavenging charge is produced by a set of passive intake check valves, and because of this the scavenging timing is important. These valves are important because they govern the volume of combustion products that are forced out of the cylinder during scavenging, and hence the efficiency of combustion in the engine. To evaluate the engine design criteria, a validated computational fluid dynamic (CFD) model was used to offer insight into how the in-cylinder flow developed during scavenging. The CFD model of this engine was used to test different check-valve geometries to see how they affect the scavenging flow in the cylinder. The goal of this is to assist in entraining more of the combustion products which would result in more being exhausted from the cylinder. A more favourable design was found, and a design produced to be taken onto the next step of testing. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2010-07-12 17:09:58.81

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