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RESEARCH PAPERS

J. Eng. Power. 1970;92(3):207-215. doi:10.1115/1.3445343.

This article presents a method of evaluating the three losses of charging, leakage and “warm-up” involved in operating the five different types of rotary displacement compressors. A comprehensive method of determining the compression efficiency, volumetric efficiency and discharge temperature is included. The limiting tip speeds, compression ratios and sizes are presented categorically. Typical application examples are given.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):217-230. doi:10.1115/1.3445346.

Magnetohydrodynamic electrical power generation is a promising new technique for upgrading the efficiency of converting heat into electricity. The concept has been explored intensively but on a small scale during the past ten years, and the initial enthusiasm in it has been confirmed. Its utilization in base-load plants, in addition to increasing overall efficiency, can also lead to important reductions in the adverse environmental effects of thermal and air pollution. The projected efficiencies of large dual cycle systems are initially in the range of 47–50 percent, and improvements in technology could later increase this to 60 percent. In an MHD system, energy is extracted from a flowing electrically conducting fluid. The fluid may be either a seeded plasma or a liquid metal. Various MHD power cycles and systems are therefore under consideration. The status of these systems will be reviewed with emphasis on their application to large central-station commercial systems. The major technological problems and progress in the three major cycles (open cycle, closed-cycle plasma, and closed-cycle liquid metal) will be discussed in depth. In the open-cycle system, the engineering solutions that have been proposed for the major problems in the generator and auxiliary equipment will be detailed. In addition, the experience gained from the operation of a succession of generators will be summarized. In the case of the closed-cycle plasma system, the progress that has been made toward developing a generator with the requisite conversion efficiency will be cited. Recent cycle analyses that have established the conditions for matching these systems to current heat sources will also be reviewed and their implications noted. The potential of developing liquid-metal MHD systems for commercial application will be explored in the light of recently obtained experimental and analytical performance information. In particular, promising new techniques that can lead to improved efficiencies will be detailed.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):231-238. doi:10.1115/1.3445347.

A method of thermodynamic analysis of power cycles incorporating more complete expansion and turbocharging with after-cooling is presented; it predicts the performance of constant volume combustion engines under detonation-free conditions. The analysis involves expressing the detonation limit in terms of the firing pressure and a theoretical adiabatic end-gas temperature. Expressing the detonation limit in this form, the performance map for any constant volume combustion engine can be predicted. The map yields detonation-free operation over a wide range of bmep and bsfc by identifying the required combinations of fuel-air ratio, compression ratio, expansion ratio, and blower pressure ratio. The analysis requires information on the combustion characteristics of the specific engine, namely, the deviations of the thermal efficiency and the firing pressure from those derived from the equivalent fuel-air cycle. Analysis showed that a significant gain of engine output can be realized without detonation occurring by employing higher blower pressure ratio and firing pressure. The lower limit of fuel consumption is determined directly by the performance of the turbocharger and indirectly by the heating of the inlet air and the detonation limit. Tests performed on a 17-in-bore single cylinder gas engine at two different expansion ratios verified the analytical prediction of detonation-free operation over a wide range of bmep, from 135 to 346 psi. The type of performance map resulting from this analysis is useful in the selection of engine performance and engine parameters for the development of new engines.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):239-251. doi:10.1115/1.3445348.

The Refuse Disposal plant being erected at Edmonton for the Greater London Council is the first of its kind to be built in the United Kingdom. It is designed to handle automatically 1333 tons (2240 lb per ton) of crude refuse every 24 hr, untouched by hand. The refuse is used as a fuel to produce steam for the generation of about 30 mw of electric power, the exact amount depending on the throughput and calorific value of the fuel. A brief description of the plant is followed by the reasons and economic considerations associated with the overall concept. Later a more detailed explanation is given of those aspects of the design which were influenced by problems peculiar to refuse handling and incineration. The roller type incineration grates and combustion chambers, which are suitable for handling metallic objects as large as bedsteads, are described and their combustion principles explained. The boilers, of which the grates and combustion chambers are an integral part, presented some problems in designing for satisfactory availability of the gas side of heating surfaces and for an economically justifiable life of certain critical parts; these problems are described and reference is made to the somewhat limited large-scale experience available at the time of establishing the design. Other parts of the plant are also described where novel in design or application.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):252-256. doi:10.1115/1.3445349.

In 1951 Ainley and Mathieson published a method of predicting the design and off-design performance of an axial turbine (British ARC, R & M 2974). The flow and hence the losses were calculated at a single “reference diameter” for each blade row. This method has been widely used ever since. A critical review of the method has been made, based on detailed comparisons between the measured and predicted performance of a wide range of modern turbines. As a result, improvements have been made in the formulas for secondary loss and tip clearance loss prediction. The accuracy of the improved method has been assessed. Despite its relatively simple approach, it is believed that it will remain of great value in project work and preliminary design work.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):257-266. doi:10.1115/1.3445350.

Using the integral form of the laminar boundary layer thermal energy equation, a method is developed which permits calculation of thermal boundary layer development under more general conditions than heretofore treated in the literature. The local Stanton number is expressed in terms of the thermal convection thickness which reflects the cumulative effects of variable free stream velocity, surface temperature, and injection rate on boundary layer development. The boundary layer calculation is combined with the wall heat transfer problem through a coolant heat balance which includes the effect of axial conduction in the wall. The highly coupled boundary layer and wall heat balance equations are solved simultaneously using relatively straightforward numerical integration techniques. Calculated results exhibit good agreement with existing analytical and experimental results. The present results indicate that nonisothermal wall and axial conduction effects significantly affect local heat transfer rates.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):267-274. doi:10.1115/1.3445351.

The paper presents two-dimensional cascade results which have been obtained in transonic and supersonic cascade windtunnels. The upstream Mach number range is 1,0 ≤ M 1 ≤ 1,4. Tests have been carried out with three different blade shapes; these are double-circular-arc and wedge profiles. The influence of solidity on the performance of these cascades has been investigated. A detailed analysis and calculation of the shock losses shows the great influence of profile shape on the total pressure loss coefficient. The profile losses are roughly constant in the investigated Mach number range. In addition, some measurements for different back pressures are presented. These results are analyzed with the aid of a simple calculation, which shows that the axial velocity-density ratio has to be considered as an important parameter in supersonic cascade measurements.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):275-286. doi:10.1115/1.3445352.

Relations are derived for the boundary layer momentum thickness growth in channels with adverse pressure gradients and for the maximum allowable momentum thickness to avoid flow separation. These data are obtained by integrating the Truckenbrodt equation stepwise and by extending the Gruschwitz-Schmidbauer separation criterion. Fair agreement between calculated data and test information is demonstrated.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):287-300. doi:10.1115/1.3445353.

The flow conditions in a mixed flow rotor are investigated for a “pressure balanced” flow path design. Boundary layer arguments are applied to calculate the losses in the rotor as well as in the subsequent diffuser section. The resulting efficiency data imply a comparatively high efficiency potential for mixed flow compressors with multiple cascaded components, designed on the premise of a “pressure balanced” rotor flow path.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):301-309. doi:10.1115/1.3445354.

The computation of power cycles employing carbon dioxide as working fluid and extending down to the critical region requires the knowledge of the thermodynamic properties of CO2 within a wide range of pressures and temperatures. Available data are recognized to be insufficient or insufficiently accurate chiefly in the vicinity of the critical dome. Newly published density and specific heat measurements are employed to compute thermodynamic functions at temperatures between 0 and 50 deg C, where the need of better data is more urgent. Methods for the computation of thermal properties from density measurement in the low and in the high temperature range are presented and discussed. Results are reported of the computation of entropy and enthalpy of CO2 in the range 150–750 deg C and 40–600 atm. The probable precision of the tables is inferred from an error analysis based on the generation, by means of a computer program of a set of pseudoexperimental points which, treated as actual measurements, yield useful information about the accuracy of the calculation procedure.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):310-314. doi:10.1115/1.3445355.

The radiation heat load assumes an important role in gas turbine life and performance as firing temperatures and pressures are increased. This first phase of a program for assessing radiant heat loading was mainly concerned with devising measurement techniques. An experimental method for measuring the temperature of luminous flames with a two-color pyrometer and radiant intensity by means of a total radiation pyrometer is described. Emittance data from two combustion liner configurations is included for chamber pressures of from 2 to 7.5 atmospheres over the turbine inlet temperature range of 900 to 1950 deg F.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):315-329. doi:10.1115/1.3445356.

The paper gives details of the experimental and theoretical work of the author on the above-mentioned subject. The first part of the paper deals with the experimental investigations of plane rotating disks whose rotational symmetry is disturbed by notches of any shape such as U-type notches, splining, keyways, and eccentric holes. The method of the stroboscopic photoelastic procedure will be described in detail, as well as the various results shown in numerous diagrams and photographs taken of the test arrangements and fringe patterns of the models. The offered material will give detailed information on the improvements of the stroboscopic photoelastic method made by the author. The second part of the paper is concerned with the application of integral equations to the stress calculation in plane rotating disks without rotational symmetry. Based on the source-like representation of the plane state of stress by Weinel, the stress problem of rotating disks without rotational symmetry is solved. The solution of the integral equations of Fredholm’s type on digital computers is carried out according to a well-known method of Oellers. The results obtained for some examples, such as the determination of the tangential stresses in the rim of plane rotating disks with variously curved boundary, are shown in diagrams.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):330-334. doi:10.1115/1.3445357.

A systematic analysis is made of the potential instability of branched diffuser systems such as are inherent to the annular combustor systems of gas turbine engines. The system is modeled to include diffusion in each branch with pressure recovery characteristics which are a simple function of the fraction of total flow into the branch. Also included in each branch is a volume (i.e., an accumulator) and a resistance representing the combustor shells before the two branched streams rejoin. Analysis of the system equations is carried out in two perspectives. First, the equations are linearized and simple generalized criteria for stability are derived. Then the full nonlinear equations are programmed for digital computation in a form where they can be integrated with respect to time, and the full dynamic behavior of flows and pressure described. The computation is carried out several times for system variations of shell resistance, accumulator volumes, and diffuser characteristics, so that general conclusions may be drawn of the effects of these parameters on the frequency, wave form, and amplitudes of the systems’ oscillations.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):335-341. doi:10.1115/1.3445358.

This paper describes an experimental study of an air-cooled gas turbine disk using the model of a disk rotating near a shrouded stator. Measurements of pressure distribution, frictional moment, and the cooling air flow necessary to prevent the ingress of hot gases over the turbine disk are described for a range of rotational speeds, mass flow rates, and different geometries. The pressure distribution is shown to be calculable by the superposition of the pressure drop due to the shroud and the unshrouded distribution. Moment coefficients are shown to increase with increasing mass flow rate and decreasing shroud clearance, but are little affected by the rotor/stator gap. Applying Reynolds analogy to the moment coefficients, it is estimated that heat transfer from the rotor will be controlled primarily by rate of radial cooling flow at low rotational Reynolds numbers, and will be governed primarily by Reynolds number at large rotational speeds.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):342-348. doi:10.1115/1.3445359.

An experimental study of the heat transfer characteristics of flows between a high speed rotating disk and a parallel stationary shroud is presented. Flow and disk heat transfer rates have been determined for various combinations and rates of freely induced and forced flows supplied at both the hub and rim of the disk. The study models a practically important class of turbine rotor cooling problems where small flow rates similar in magnitude to the disk pumping flows are of interest. The experimental facility and procedures are described in detail. They have been designed to facilitate rapid and economical acquisition of rotor cooling characteristics in situations where the particular rotor-shroud geometry makes existing correlations inadequate.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1970;92(3):215-216. doi:10.1115/1.3445345.
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Abstract
Commentary by Dr. Valentin Fuster

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