VTechWorks Repository :: Browsing by Author "Jones, J. B."

Browsing by Author "Jones, J. B."

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A critical study of various types of exhaust gas analyzers for gasoline engines
Dilworth, John L. (Virginia Tech, 1940-05-05)
It is quite common practice in automotive and aircraft engine maintenance, operation, and research to employ any one of several types of instruments now on the market for determining the air-fuel ratio by exhaust gas analysis. It was the purpose of this investigation to determine the most important operating characteristics, especially range and accuracy, of each of these types of instruments. The theory underlying the operation of this kind of apparatus was studied critically, and certain tests were performed on representative makes in order to observe the operation of each type under service conditions. These tests consisted essentially of connecting the analyzers to the exhaust pipe of a single-cylinder engine and comparing the analyazer readings with the true air-fuel ratio determined by accurately measuring the air and fuel supplied to the engine while the instruments were being observed. This procedure was repeated for a number of different carburetor settings, all other factors being kept as nearly constant as possible during a given series of runs. The effect of variations in engine spark advance and the pressure of the gas supplied to the instruments was also investigated. The test revealed several interesting facts. Study of the operating principles of the several instruments indicated that they were limited te air fue1 ratios below about 14 to 1, and this has been conclusively proved by these experiments. This limitation applies to thermal conductivity, hot-wire catalytic, and relative density types. W While the most expensive makes of instruments were not tested, it was found that, in general, the limit of accuracy is not greater than one-half of one air-fue1 ratio, regardless of the operating principle employed. Large variations in the pressure and rate of flow of the exhaust supplied to the analyzers were found to cause considerable deviations in those instruments which did not employ some kind of device to insure a steady and uniform supply. Certain features of design and construction which effect the reliability of the various types of exhaust gas analyzers are also reviewed in this thesis, and some of the more important chemical methods of analysis are treated briefly.
The design and test of a high speed engine indicator
Lindamood, Benton Brown (Virginia Tech, 1955-05-15)
The indicator provided accurate data for that portion of the engine cycle where the operation of the indicator was not affected by extraneous electrical interference.
An economic justification of using a small turbine rather than pressure reducing valves between the high pressure header and high pressure heating lines of V.P.I. Power Plant
Chatterjee, Anil Kumar (Virginia Tech, 1953-06-05)
Generally it is believed that in a power station when there is a demand for process steam and also demand for heating, most of the auxiliaries of the plant should be arranged to be driven by steam rather than using electrical energy for them. This is, however, a general remark and a correct selection can be made only after a detailed study is made of all factors involved. The V. P. I. central heating and power plant works mainly as a heating station, generation of electrical energy, being a by-product. So this problem is completely different from the standpoint of a general power station. This station supplies heating steam to the college through two different pressure lines. One is the low pressure, and the other is the high pressure line.
An economic study of a proposed 2000-KW turbo-generator unit in the Virginia Polytechnic Institute central heating and power plant
McMurrer, James Emmet (Virginia Tech, 1952-06-05)
The chief function of the Virginia Polytechnic Institute Central Heating and Power Plant is to provide steam for heating the various building: on the campus. The plant also furnishes the campus and the community of Blacksburg with a portion of their power requirements, the campus with hot water, and the college laundry with soft water The basic function of the plant, however, is the generation cf steam to be used for heating most of the buildings located on the oampus.The electric energy is generated as a by-product of the basic heating function of the plant.
An economic study of a proposed high-pressure boiler and turbo-generator unit in the central heating and power plant of the Virginia Polytechnic Institute
Anderson, Victor Fontaine (Virginia Tech, 1953-06-03)
Through this thesis evidence will be collected to determine the need of a proposed turbo-generator and boiler unit adequate for future requirements of the campus and community of Blacksburg.
The effect of chromium plating on the endurance limit of 4340 steel
Cabble, George M. (Virginia Tech, 1952-06-05)
The percentage of reduction in fatigue limit of AISI 4340 steel due to one chromium plating was 21 percent, based on the fatigue limit of unplated AISI 4340 steel.
Efficiency test of the dust collector on No.6 boiler in the V.P.I. power plant
Truitt, James Linford; Riel, Richard H. (Virginia Tech, 1951-05-31)
From the tests run it was observed that load variations have a pronounced effect both on size analysis and concentration of the flyash.
An implicit numerical solution of the turbulent three-dimensional incompressible boundary-layer equations
Klinksiek, William Frederick (Virginia Tech, 1971-06-05)
A method of solving the three-dimensional, incompressible turbulent boundary-layer equations was developed using a Crank-Nicholson implicit finite-difference technique, with the turbulent stress terms modeled with an eddy-viscosity model obtained from mixing length theory. The method was applied to two three-dimensional flow geometries for which experimental data exists and a comparison with this data showed excellent agreement. The complete computer program was sufficiently generalized for application to two-dimensional laminar and turbulent flows with arbitrary pressure gradients. The method was applied to several such test cases and the solutions agreed well with both theory and experiment. An analysis was presented to determine the conditions for which the finite difference equations were stable and convergent. The results of this analysis demonstrated that the equations are generally stable and convergent. However, care must be exercised when writing the finite difference approximation to the continuity equation, because certain finite difference formulations of the continuity equation can lead to an instability when the initial values for the distribution of the velocity normal to the bounding surface cannot be accurately specified.
An integral analysis of two-phase annularmist condensing flows
Berry, Maurice Robert (Virginia Tech, 1970-08-19)
In this investigation of the two-phase, annular-mist flow of a condensing vapor, the following significant conclusions are drawn. The conclusions are based on the numerical results obtained from the theoretical analysis. Where appropriate, recommendations for future studies are included: 1. The analytical model accurately predicts the condenser length necessary for complete condensation and, with a reasonable degree of accuracy, the dynamic quality, heat transfer characteristics, and static pressure distribution. 2. An integral analysis is presented for which the assumed velocity and enthalpy profiles are the power-law type. For the range of temperatures and pressures encountered in this investigation, varying the profile shapes has a negligible effect on the dynamic quality and static pressure distributions at all except high vapor velocities. 3. The analysis accounts for the slip between the entrained particles and the vapor in the gas core. A constant entrainment slip ratio (SE) is assumed. Reducing the ratio below unity has an effect of the static pressure drop. The effect, however, is comparatively small. 4. Due to the lack of entrainment flow rate data available for two-phase, annular-mist, condensing flows, a variable entrainment correlation is included in the analysis.
A Model for Abrasive Polymer Wear
Herold, John Henry (Virginia Polytechnic Institute and State University, 1980)
The abrasive mechanism of polymer wear is dominant in the startup, or "breakin", stage of polymer/steel sliding systems. This mechanism controls the polymer wear rate until the voids in the hard metal surface are filled, much like the filling observed with a file when used on soft metals. This regime of polymer wear is modeled on an event-by-event basis. The model utilizes a digitized profile of the metal surface, bulk polymer properties such as flow pressure and elongation at break, and a few system parameters such as load and slider geometry. The predictions of the model are compared with experimental data. The predicted wear rates are within a factor of 3 of the measured wear rates for polymers with glass transition temperatures, Tg, above the interfacial temperature (rigid PVC and PCTFE). The validity of the model is shown to be related to the ductile or brittle behavior of the sliding polymer.
A numerical analysis of turbulent flow along an abruptly rotated cylinder
Aguilar, Felix (Virginia Tech, 1975-12-15)
Great progress has been achieved over the past fifteen years in the computation of two-dimensional turbulent flows. The proceedings of the 1968 Stanford Conference (1) attest to the success of several methods in predicting skin friction and heat transfer coefficients, mean velocity and temperature fields, and to a lesser degree boundary layer separation. This success is due less to the fact that the physics of turbulence is well understood (it is not) than to the fact that the existent two-dimensional data obtained within pipes and on external surfaces have lent themselves to correlation. It is these correlations (particularly near-wall similarity or the law-of-the-wall) which serve as the empirical foundation of the mixing length and eddy viscosity "theories" of turbulence. The term mathematical model may more aptly describe the mixing length/eddy viscosity approach to turbulence than the word theory, for these concepts take into account little of the basic dynamics of turbulence (its production, intensity, frequency, and dissipation). Yet these methods are significant precisely because they do predict with uncanny accuracy the gross consequences of turbulence in a number of two-dimensional flows of practical interest. Mixing length/eddy viscosity models are attractive to the engineer because these models are agreeably simplistic. That is, their formulation is algebraic and does not involve differential equations or additional turbulent transport equations. The monograph (2) of Launder and Spalding presents an excellent review and evaluation of current mathematical models of turbulence. On account of their simplicity, the mixing length/eddy viscosity models are relatively straightforward to implement and economical to use. Thus they are ideally suited for industry. The present work is an investigation of the suitability of the eddy viscosity approach for the prediction of three-dimensional turbulent flows. The eddy viscosity formulation employed is essentially an extended two-dimensional model. Unfortunately, endeavors to correlate three-dimensional turbulent data have not been as successful as with the two-dimensional case. White (3) has neatly summarized the more significant postulations of a three-dimensional law-of-the-wall. All are patterned after the two-dimensional near-wall similarity hypothesis, and of course none can be confirmed without direct measurement of wall shear stress. No such measurements have been performed to date with the exception of the data of Pierce and Krornmenhoek (4), who did not specifically study the question of near-wall similarity in three-dimensional flows. Thus the present analysis is necessarily a simplistic one. It is based on the fact that every turbulent flow is actually three-dimensional and on the supposition that a correlation which succeeds with a two-dimensional mean velocity field may well succeed in the calculation of a three-dimensional field.
The possibility of increasing compression ratios by using water as an anti-detonant
Haines, Raymond G. (Virginia Tech, 1936-05-05)
Conclusions (1) Water 1s a knock suppressor. (2) Water does not act as an anti-detonant by slowing down the rate of flame propagation, but merely removes a portion of the heat of combustion. (3) Increasing the compression ratio requires a decrease in spark advance.
Prediction of the running torque of instrument ball bearings at high speed under combined radial and axial loads
Clarke, George Edward (Virginia Tech, 1968-08-05)
The purpose of this investigation was to develop an expression to represent the torque versus speed behavior of instrument ball bearings between 1000 and 40,000 rpm with various combinations of radial and axial load ranging between 0 and 200 grams. Because of the lack of experimental data for instrument bearings over any range of speeds, loads and sizes, it was necessary to construct a suitable bearing tester and accumulate the required data. The testers used were based on previous work by H.H. Mabie at Sandia Corporation and G.E. Clarke at V.P.I. The driving source was a small air turbine developed by Mabie which performed smoothly and reliably between 0 and 50,000 rpm. The torque measuring system employed strain gages on a very small beam which was used to sense forces on the stationary outer race of the bearing while the inner race was driven at speed. Each test was conducted from 0 to 40,000 rpm. The radial load took on va1ues of 50, 100, and 200 grams. The axial load was 0, 50, 100, and 200 grams. All combinations of these loads were used for each size bearing. The sizes tested were R-2, R-3, R-4. Six bearings of each size were used with all six bearings of each size undergoing the same test program in order to yield statistically reasonable averages. Investigation of analytical methods of predicting the running torque indicated that production tolerances of ball bearings rendered such an approach impractical. This led to the development of an empirical expression to predict the running torque within the same range of sizes, loads, and speeds for which experimental test data was obtained. Such an empirical expression was successfully developed and the reSUlting torque predictions compared with the experimental values of torque. The empirical expression proved capable of predicting the running torques within the envelope of the sample standard deviations for a given bearing size and loading in most cases. During the investigation of supplementary topics, it was determined that frictional heating was insignificant during the conduct of the torque tests which had a duration of approximately two minutes. All tests were at ambient temperature. All tests conducted were with oil lubricant and ribbon retainer ba1l bearings. There was no evidence that the empirical expression for friction torque developed here was valid when extrapolated beyond the limits of size, load, and speed used in its development.
Some problems in the axially symmetrical bending of a thick circular plate resting on an elastic foundation
Ho, Hung-Ta (Virginia Tech, 1955-08-05)
From the results of the cases discussed, it can be concluded that the neglect of transverse-shear deformation and normal stress results in expressions for bending moments and deflection which may be seriously in error. /
Transfer matrix analysis of an electrohydraulically driven rotary- vibratory drilling system
Ohanehi, Donatus Chukwubueze (Virginia Tech, 1980)
This research develops transfer matrix model for the longitudinal vibratory component of a rotary-vibratory drilling (RVD) system driven with an electrohydraulic inertial mass exciter. The RVD system is a hybrid drilling system consisting of a conventional rotary drilling system assisted by forced harmonic vibrations. The model includes a drill string with continuously distributed inertia, stiffness, internal material, and external fluid damping. These properties were introduced through a new continuum transfer matrix for a damped pipe element. The model allows for the inclusion of realistic geometrical representations for the drill string, and the inclusion of masses, springs, dashpots, and other axial structural elements. The force exerted on the drill string by the drilling fluid was included using the theory of a flat plate oscillating in a newtonian fluid. The force had an inertia and a viscous damping component. These were incorporated into the inertia and external fluid damping terms in the new continuum transfer matrix. The exciter had force and power limits. The rock-rock bit boundary was represented as a structurally damped spring.
The vibration of instrument ball bearings in a controlled environment and the effect of the resulting fretting corrosion on bearing torque
Hite, Gregory Charles (Virginia Tech, 1970-08-05)
Fretting corrosion is a form of wear which occurs at the interface of two contacting solid materials as the result of small, relative vibratory motion. It is generally identified by the presence of a red oxide, Fe203. Previously, the majority of the investigators studied the fretting corrosion between two flat specimens or between a single ball and a flat plate held in contact by a normal force. There are a number of interrelated influencing factors involved in fretting corrosion including: the vibration frequency and amplitude, the environmental conditions, the characteristics of the material, and the type of lubrication. The present investigation was conducted in order to investigate the effects of frequency and amplitude of axial vibration and the consequent accelerations acting to produce fretting damage within an unlubricated instrument ball bearing. The effect of bearing axial play on the fretting damage was also examined. The reproducibility of the damage resulting from these variables was determined.

Browsing by Author "Jones, J. B."

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