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Full-Text Articles in Engineering Science and Materials
Emission Reduction In Small Displacement Diesel Engines Using Cooled Exhaust Gas Recirculation, Chris Simoson
Emission Reduction In Small Displacement Diesel Engines Using Cooled Exhaust Gas Recirculation, Chris Simoson
All Theses
A reduced-order dynamic model is presented and experimentally validated to demonstrate the use of cooled exhaust gas recirculation to alleviate the tradeoff between nitric oxide reduction and performance preservation in a small displacement diesel engine. Exhaust gas recirculation (EGR) is an effective method for internal combustion engine oxides of nitrogen (NOx) reduction, but its thermal throttling diminishes power efficiency. The capacity to cool exhaust gases prior to merging with intake air may achieve the desired pollutant effect while minimizing engine performance losses.
Simulation and experimental results revealed significant NOx reductions throughout all testing scenarios using EGR, but also experienced a …
Modeling Of The Transient Behavior Of Heat Pipes With Room-Temperature Working Fluids, Pascal Brocheny
Modeling Of The Transient Behavior Of Heat Pipes With Room-Temperature Working Fluids, Pascal Brocheny
All Dissertations
The heat pipe is a capillary-driven and two-phase flow device, capable of transporting and converting large amounts of energy with minimal losses. As a means of thermal management, uses of heat pipe technology not only include thermal control of satellites and spacecrafts in aerospace applications, but also the cooling of electronic components for ground applications. Recently, there has been a flourishing interest in exploring the use of heat pipe technology in the automotive field. However, in many thermal control applications, heat pipes using room-temperature working fluids, such as water or ammonia, with operating temperatures between 200 K (-73ºC) and 550 …
Simulation And Characterization Of Tire Nonuniformity-Induced Steering Nibble Vibrations Through Integrated Subsystems Modeling, Derek Mangun
All Theses
Periodic force variations produced by nonuniform tire/wheel assemblies are known root causes of torsional steering wheel vibrations known as 'nibble'. Previous studies have sought to investigate this issue through modeling or experimentation involving the entire vehicle or specific subsystems, however a direct link between objectively measured tire force variations and the vibration levels perceived by vehicle occupants has yet to be established. Analytical models of a nonuniform tire, double-wishbone suspension system, and rack and pinion steering system are sourced from literature and integrated into a single subsystem-level model validated against experimental data obtained as part of a collaborative effort. The …
A Robust Conjugate Heat Transfer Methodology With Novel Turbulence Modeling Applied To Internally-Cooled Gas Turbine Airfoils, William York
A Robust Conjugate Heat Transfer Methodology With Novel Turbulence Modeling Applied To Internally-Cooled Gas Turbine Airfoils, William York
All Dissertations
Computational fluid dynamics and heat transfer (CFD) has become a viable, physics-based analysis tool for complex flow and/or heat transfer problems in recent years due, in large part, to rapid advances in computing power. CFD based on the Reynolds-averaged Navier-Stokes (RANS) equations is starting to enter the mainstream design environment in certain industries where rapid and reliable predictive capability is necessary. One such application is the gas turbine industry, where thermal management of airfoils at extremely high temperatures is one of the most critical components in engine design for reliability. The problem is complicated by the need for advanced airfoil …
Modeling And Simulation Of Friction-Limited Continuously Variable Transmissions, Nilabh Srivastava
Modeling And Simulation Of Friction-Limited Continuously Variable Transmissions, Nilabh Srivastava
All Dissertations
Over the last few decades, a lot of research effort has increasingly been directed towards developing vehicle transmissions that accomplish the government imperatives of increased vehicle efficiency and lower exhaust (greenhouse gaseous) emissions. These exhaust emissions can be regulated or lowered by increasing the fuel economy of a vehicle, and CVTs (continuously variable transmissions), indubitably, play a crucial role in this plan to improve the fuel economy. A continuously variable transmission is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. A CVT offers numerous advantages over the conventional multi-step gear transmissions such as …
Investigation Of The Effects Of Subgrid-Scale Turbulence On Resolvable-Scale Statistics, Qinglin Chen
Investigation Of The Effects Of Subgrid-Scale Turbulence On Resolvable-Scale Statistics, Qinglin Chen
All Dissertations
The effects of the subgrid-scale (SGS) turbulence on the resolvable-scale statistics and the effects of SGS models on large-eddy simulation (LES) are studied. It is shown that the SGS turbulence evolves the resolvable-scale joint probability density function (JPDF) through the conditional means of the SGS stress, the SGS scalar flux, and their production rate, which must be reproduced by the SGS model for LES to predict correctly the one-point resolvable-scale statistics, a primary goal of LES. This necessary condition is used as the basis for studying SGS physics and for testing SGS models. Theoretical predictions, measurements data obtained in a …
The Effects Of Viscoelastic Behavior On The Operation Of A Delayed Resonator Vibration Absorber, John Cowans
The Effects Of Viscoelastic Behavior On The Operation Of A Delayed Resonator Vibration Absorber, John Cowans
All Theses
Delayed resonators have proven to be effective vibration absorbers (VAs) for tracking and canceling the effects of harmonic excitations on a structure. The Delayed Resonator (DR) is selfcontained, as no information from outside of its substructure is required for proper operation. It adjusts for variations in frequency using time-delay and gain as control parameters.
This thesis examines the relationship between viscoelastic (VE) loss mechanisms in systems with DR and the choice of modeling method used to calculate control parameters and determine system stability. It is hypothesized that a VE loss mechanism approximated by a single viscous dashpot may lead to …
Internal Combustion Engine Cooling Strategies: Theory And Test, John Chastain
Internal Combustion Engine Cooling Strategies: Theory And Test, John Chastain
All Theses
Advanced internal combustion engine thermal management systems can enhance overall engine performance through the use of computer controlled cooling system actuators. Existing ground vehicle cooling systems generally have performance limitations due to the fixed behavior of the wax-based thermostat valve and crankshaft dependent operation of the coolant pump and radiator fan. Upgrading the traditional thermostat valve, water pump, and radiator fan with actuators permit real time computer control for improved temperature tracking and reduced power consumption. In this paper, the benefits associated with advanced automotive cooling systems are experimentally investigated. A 4.6L engine with a real-time data acquisition and control …