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.

Digital Clay is a tactile array of linear fluidic actuators which provide distributed sensing and position control through the use of an embedded position sensor. The actuator implementation is achieved by two-way hydraulically-driven pistons which are integrated with computer controlled valves. Each actuator is connected to an underlying base plate which is in fluidic communication with high and low pressure reservoirs. The research focuses on the aspects of the fluidics necessary to operate the actuators and control actuation of Digital Clay. The main objectives of this work are the characterization of the fluid flow through the system and the design and implementation of an embedded inductance-based position sensor. Each actuator in Digital Clay is individually addressable and is controlled through the use of a closed-loop proportional integral controller with position feedback from the embedded inductance-based sensor. Also presented in this work is the characterization of an individual fluidic actuator and the realization of a 5x5 tactile array of actuators.

This thesis describes detailed investigations of two different problems in gas-liquid two-phase flow, namely, a study of interfacial stability in a partially filled cylinder subjected to vertical oscillations and a study of heat and mass transfer from hot spray droplets injected into an closed vessel. The interfacial instability study considers experimental data taken from the author's previous work. Cylinders of various diameters, partially filled with water, ethanol or glycerol were subjected to a sinusoidal vertical motion. The critical acceleration, causing the interfacial wave to grow unstable, was found to be approximately constant for a given cylinder diameter, independent on the amplitude of the forcing oscillations. The experiments also indicate that the critical Acceleration always decreases with increasing cylinder diameter. A mathematical analysis of the interfacial instability is based on a stability investigation of a Mathieu equation. It is shown that the experimental data fall into unstable regions for a single, first mode of oscillations. This finding is supported by the experimental analysis given by Cilliberto and Gollub. The analysis shows the effects of the liquid column height on the interfacial instability to be dependent on tanh (k..l.). This multiplier is equal to 1 for the column heights of 250mm, 500 mm and 750 mm, investigated, and a given cylinder diameter, thus having no effect on the results. Computational analysis of the interfacial problem is developed which is based on the simplified MAC method incorporating the Continuum Surface Force (CSF) model for simulating the effects of surface tension. Computational experiments were run for water and glycerol, the two liquids of significantly different properties. The results are presented in the form of time sequenced plots showing the interfacial positions and graphs relating the interfacial wave amplitude and time. Stability of the interface is found to be dependent on the initial surface disturbance. Growth of the interfacial wave is observed in some cases. In the range of situations investigated, surface tension effects are found to have only a small influence both on the stability and frequency of the interfacial oscillations. The period of interfacial oscillations with no forcing vibrations is found to be in good agreement with the period predicted by mathematical analysis. Influence of the initial disturbance profile was also investigated. The results indicate that the interfacial wave adopts oscillatory behaviour similar to the other cases. The oscillation frequency of the interfacial wave undergoing forcing vibrations is found to match the findings of the mathematical analysis. The wave oscillates with an angular velocity equal to the multiples of the half the forcing vibration angular velocity, co/2. In the second investigation a testing rig was constructed to investigate the heat and mass transfer processes in dense hot sprays injected into an enclosed cylindrical vessel. Heat and mass transfer rates were investigated indirectly from the measurements of the gas - vapour mixture pressure rise in the cylinder. The experiments covered different combinations of the parameters influencing the processes. The number and size of spray nozzles, the vessel volume, the type of gas and the initial pressure level in the cylinder were investigated. The experimental results indicate that, for the range of solid cone nozzles tested, the heat and mass transfer characteristics are, to a first approximation independent of the size of the nozzles. The results also show that the rise of spray chamber internal pressure is directly proportional to liquid temperature and flowrate. An analysis, based on energy balances for the whole cylinder, has yielded a new dimensionless group incorporating the important parameters of droplet heat transfer namely the droplet velocity and radius, spray chamber dimensions, gravity, conductivity and convectivity. A good match has been found between the analytical results and experimental findings. An improved analysis, incorporating the effect of evaporation from drops, is also presented. It is based on simultaneous solution of energy and mass balance equations for a single droplet. Again, good agreement with the experimental results is found. Both analyses indicate that, for this particular case of dense, evaporative spray, the Nusselt number tends to have a value equal to I.

Thesis (M.S.)--Ohio University, August, 1993. / Title from PDF t.p.

No description available.

A High percentage of fuel consumption worldwide is in internal combustion engines which has led environmental organizations and authorities to put further pressure on the engine industries to reduce CO2 emissions and enhance engine efficiency. However, historically, the effect of the compression ratio on increasing thermal efficiency of the engine is well known, hence; numerous technical solutions have been proposed to implement a variable compression ratio concept. A new first-class engineering solution to use a hydraulic piston was initially patented by BICERA (British Internal Combustion Engine Research Association) , then improved by Continental and Daimler Benz. A Hydraulic variable compression ratio piston is a hydraulically actuated piston that provides a practical method of obtaining a variable compression ratio piston. In this literature, a hydraulic variable compression ratio piston for a Volvo D13 diesel engine was designed, analyzed, modeled and discussed. This analysis was accomplished by first performing kinematic and dynamic analyses for the piston motion and acceleration based on the crank-slider mechanism. Following this the oil flow characteristics were defined in every mechanical element transferring the oil in its journey from the engine pump to the piston. Moreover, two different designs were proposed in an attempt to predict the compression ratio by modeling the hydraulic, dynamic and engine execution simultaneously. Additionally, stress on the piston was analyzed using Finite Element Analysis (FEA) to assure piston sustainment and rigidity against the harsh combustion chamber environment. In conclusion, the best design was successfully selected and finalized to reach a wide compression ratio range under a boosted inlet pressure based on the selected design, dimensions, check valves and relief valves.

The aim of this thesis is to design Husqvarna FE 501 turbocharged engine piston for Formula Student competition using bioethanol as its fuel. Proposed concept originates in background research on design solutions of modern combustion engine pistons. FEM simulations are used for piston design.

No description available.

The project consists of controlling a mechanical piston and thermal resistance using an Arduino’s microcontroller. The piston and the thermal resistance take part of an existing project. This project, known as The electronic nose, has the purpose to measure the aroma of different products. In order to achieve this purpose, this tool is a combination of various sensors used to detect gases by generating signals for an analysis system. The project can be divided in different parts; electrical circuit design of piston and thermal resistance, design mechanical parts and components needed, develop a software able to control the piston and the thermal resistance and communication between software. The piston is installed on the bottom part of hollow cylindrical case and the thermal resistance is located inside a cylindrical base. This base, where the sample for smelling is put up, is bound on the top of the piston. Arduino controls the piston up and down movement and the temperature in the sample’s base. On the other hand, the electronic nose is installed at the top of the case. Through its sensors, The electronic nose is able to measure the aroma of some products. The aroma comes from the gases of the sample and they can be detected by the sensors. The purpose of installing the piston in the electronic nose is to get a pulse signal during the measure of these gases. Moreover, is very important keep the temperature of the sample under control, therefore the software is based on a on/off controller. A on/off controller calculates continuously the difference between a desired temperature set point and the temperature measured during process. In order to minimize this difference value the controller turn on or off the resistance during a specific instant time.

<p>The valve plate/cylinder block interface in an axial piston pump is often subject to extreme pressures, which can cause wear of the valve plate and ultimately, failure of the pump. The purposes of this study were to: a) experimentally investigate the film thickness generated between a floating valve plate and cylinder block in situ using proximity probes, b) develop a model which can predict the motion, film thickness and pressures of the floating valve plate and corroborate with experimental results, c) investigate surface pockets to provide additional lubricant at the valve plate interface by measuring the flow velocities and cavitation areas in a thrust washer bearing, d) numerically investigate surface modifications of the floating valve plate to observe any changes in lubricant pressure, temperature, cavitation, or valve plate deformation. Two different test rigs were designed, developed and used to investigate the performance of axial piston pumps and surface pockets. The axial piston pump test rig (APTR) was designed to operate and measure the steady state conditions of an axial piston pump. The APTR utilizes three non-contact proximity probes to measure the valve plate motion and film thickness between the cylinder block at various speeds and pressures. A thrust washer test rig (TWTR) was developed to measure the cavitation areas and flow velocities of lubricant in a pocketed thrust washer using μPIV. Through a novel interpolation approach, the depths of the micro-particles in the bearing pocket were determined using an analytical model. Using this approach, the μPIV measured 2D velocity field was employed to develop a 3D velocity field, which illustrates the fluid motion inside a pocketed thrust bearing at various speeds and viscosities. A dynamic lubrication model was developed using the thermal Reynolds equation augmented with the JFO boundary condition and the energy equation to determine the pressure, cavitation regions and temperature of the lubricant at the valve plate cylinder block interface. The lubricating pressures were then coupled with the equations of motion of the floating valve plate to develop a dynamic lubrication model. The stiffness and damping coefficients of the floating valve plate system used in the dynamic lubrication model were determined using a parametric study. The elastic deformation of the valve plate was also considered using the influence coefficient matrix approach. The experimental and analytical motion of the valve plate were then corroborated and found to be in good agreement. 4 and 8 pocket designs were then added as surface modifications to the floating valve plate in the dynamic lubrication model. The addition of surface modifications improved the lubricating conditions at the valve plate/cylinder block interface and resulted in increased minimum film thicknesses and lowered lubricant temperatures at the same operating conditions.</p>