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RESEARCH PAPERS

J. Eng. Power. 1974;96(3):161-164. doi:10.1115/1.3445787.
Abstract
Topics: Ducts
Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):165-168. doi:10.1115/1.3445788.

An original air-conditioning system was developed which requires considerably less power than conventional systems while providing identical cooling and dehumidification. The 50 percent (depending on application) power reduction is accomplished by off-peak compressor operation and storage of chilled water. The full cooling and dehumidification is accomplished by means of a new thermodynamic cycle involving two evaporators with an intermediate condenser operating with the stored chilled water. The system was built, instrumented, and operated reliably. Evaluation of performance data confirmed the theory and verified the power reduction, cooling, and dehumidification performance calculations.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):169-174. doi:10.1115/1.3445789.

The objective of this paper is to investigate the nature of the failure rates of redundant repairable hardware. The analysis considers the case of two nominally identical, functionally independent parts. Part failures are assumed to occur randomly, with the time to failure taken to be exponentially distributed with constant failure rates. Part repair times are assumed to be constant. It is shown that the instantaneous failure rate, of the two-part redundant system is essentially constant for all but a short initial period and that the average failure rate quickly approaches a constant asymptotic value.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):175-180. doi:10.1115/1.3445790.

This paper presents a method to quantify in terms of probabilistic availability the effects of testing and maintenance schedule on the performance of a standby safety system and it describes the mathematical rationale which lies behind it. The purpose of periodic testing and maintenance is to detect any unannounced failures in the system, repair them, and thus ensure the readiness or availability of the equipment. A scheme is given to model generally any complex system in terms of easily visualized equivalent block diagrams such that the formulas developed in this paper or similarly developed formulas can be easily applied. Also presented is a method for incorporating the field failure data to refine á priori assumed failure rates which were used in the initial computations.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):181-184. doi:10.1115/1.3445791.

To investigate the sources of acoustic radiation from a gas turbine exhaust, a one-seventh scale model has been constructed. The model geometrically scales the flow path downstream of the rotating parts including support struts and turning vanes. A discussion and comparison of different kinds of aerodynamic and acoustic scaling techniques are given. The effect of the temperature ratio between model and prototype is found to be an important parameter in comparing acoustical data.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):185-188. doi:10.1115/1.3445792.

A low-nitrogen fuel, ASTM Jet A aviation kerosene, was doped with increasing amounts of pyridine as a means of increasing the content of chemically bound nitrogen, then burned at a rate of 50 lb/hr in a compact combustor incorporating staged air admission with a rich primary zone, and water cooling of the walls. Each increase in fuel nitrogen content resulted in a significant increase in NOx in the combustion products, and it is estimated that as much as 90 percent of the fuel nitrogen was converted to NOx at very low nitrogen levels, decreasing to 55 percent conversion at higher levels. These results are consistent with data reported for large steam boilers and for small residential boilers. It appears that emission standards requiring very low levels of NOx emission will require use of fuels with very low nitrogen content.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):189-200. doi:10.1115/1.3445793.

The 1-MWt Heat Transfer Model (HTM-1) test program was directed to the development of techniques to predict, and thereby avoid, water-side instabilities in sodium-heated once-through and recirculating steam generators. Water-side performance instabilities in steam generators have been an underlying problem through decades of experience. This subject is of particular concern to sodium-heated units due to the severe performance deterioration that can result from such instability. The 1-WMt test model contains nine 0.50 in. OD 130 ft long serpentine tubes. Thermocouples and low-pressure-drop orifice flow meters were installed at the feedwater inlet end of each of the three active tubes to disclose instabilities. These measurements were recorded on a high-speed oscillograph. Instabilities were deliberately induced in order to determine the inception condition of instability. The model was dynamically stable for a range of operating conditions. The model was statically stable (uniform static feedwater flow distribution) at all steam outlet conditions tested. The model was generally more stable than predicted especially at higher loads.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):201-208. doi:10.1115/1.3445794.

A method is given for analyzing the vibrations of turbine blades subjected to flows at high negative incidence angles. The conditions for the existence of self-excited vibrations and the stability of these vibrations are derived for free-standing or grouped blades which are of tapered and twisted form. The technique given extends the analysis of Sisto [1] to the case in which any mode of vibration may be considered and in which the aerodynamic forces and moments taken on a quasi-steady basis are functions of Mach number as well as instantaneous angle of attack. Results are given for a group of four lashed blades and some experimentally observed behavior is reported.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):209-215. doi:10.1115/1.3445795.

Efficient condensing surfaces are highly desirable in the design of solar sea power plants utilizing the ocean temperature difference. This paper examines a number of surface designs and presents a convenient method for optimizing the design. In particular, the various parameters of a Gregorig surface are optimized.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):216-222. doi:10.1115/1.3445796.

Chlorides play an important role in corrosion of heat-transfer surfaces and wet-scrubbers in municipal incinerators. The nature of the deposits and the extent of corrosion have been investigated in a combined field and laboratory study. Corrosion by flue gases and accumulated deposits has been measured by probes exposed in large municipal incinerators. The corrosion rates of various metals by incinerator scrubber waters also have been determined. Parallel laboratory experiments were conducted to provide additional data under controlled environments for interpretation of corrosion reactions. General surface wastage, pitting, or stress-corrosion cracking was observed in different samples, depending on the exposure conditions.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):223-227. doi:10.1115/1.3445797.

Obtaining an estimate of the precision realized in heat rate testing is discussed in this paper. Heat rate precision depends largely on the scatter of the most important measurements, so we examine their scatter. All solutions proposed are based on the assumption that the data arise from a normal population, although answers are also useful for near-normal distributions. We propose a three-part procedure designed to ensure the gathering of data of a given precision with a given confidence. The procedure should fit easily into the test engineer’s routine.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):228-234. doi:10.1115/1.3445798.

Modern aero-engine fans (without inlet guide vanes) produce a tone at blade passing frequency by interacting with the inlet flow distortion. Because the distortion is altered by forward motion of the aircraft the tone is also different under static and inflight conditions. At low tip relative Mach numbers (less than about 0.85) the significant source of distortion is the intake wall boundary layer. At higher tip Mach numbers the principal distortion under static conditions is the atmospheric turbulence drawn into the intake, but in flight this reduces and other forms of distortion may then dominate.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):235-239. doi:10.1115/1.3445799.

The effect of EGR (Exhaust Gas Recirculation) on the emission of NOx , CO, and HC from two compact, low-emission burners sized for use in automotive Rankine-cycle engines was studied experimentally. One burner was a lean-primary design, and the other was a rich-primary design. Both had been developed to meet 1976 Federal Emission Standards for automobiles. It was shown that EGR resulted in significant reduction of NOx emission from both burners, with negligible effect upon emission of HC and CO. The effect of EGR was additive to the effect of excess air, staged air admission, and wall cooling.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):240-246. doi:10.1115/1.3445800.

A semiempirical technique for predicting the NOx emission index from the combustion of distillate type fuels with air was developed. This technique was devised to help evaluate combustion modification procedures for lowering NOx emissions. Equilibrium calculations, generally used to obtain directional estimates of pollutant concentration, can lead to errors. Some possible pitfalls in using equilibrium calculations are illustrated. The semiempirical technique is based on chemical kinetics and neglects fluid-dynamic effects. The kinetics are based on the modified Zeldovich chain mechanism for NO production from hot air and Fenimore’s data for “prompt NOx ”. The resulting expression lends itself to hand calculation provided the nitric oxide equilibrium value is known at the temperature and pressure of interest. Excellent agreement was obtained with experimental results from gas turbines. The apparent time required to produce NOx was the only adjustable parameter used to fit the data. A large volume of data from aircraft gas turbines was correlated by assuming an apparent residence time of 0.5 millisec. The effectiveness of water addition in minimizing NOx emissions was predicted for a model of an industrial gas turbine using 2 millisec residence time. These residence times are somewhat short but physically reasonable. The calculations predict that the maximum NOx emission index shifts from stoichiometric combustion to lean combustion as air preheat temperature is lowered. This prediction has not been confirmed experimentally.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):247-254. doi:10.1115/1.3445801.

In a previous paper [1], the analysis of pump suction pressure decay utilizing the varying condensate temperature approach was first introduced. Although the paper provided power plant engineers with an accurate analytical method for determining the magnitude of feedwater pump suction pressure decay, no protective method to prevent or alleviate the pressure decay under instant turbine load rejection was mentioned. As unit size has rapidly increased in recent years, the power plant deaerator requires not only a larger storage capacity but also must be elevated higher to protect the boiler feed pumps against suction pressure decay under load rejection. Since this trend is expected to continue, the cost of supporting the power plant deaerator may soon become prohibitive. Several protective methods have been previously introduced. However, the evaluation of the methods was invariably based on the constant-condensate-temperature approach, which is not suitable for central station regenerative cycle units. This paper reevaluates those methods in general and recommends the on-off type deaerator bypass system as the most effective and economical method. The use of this protective method will not only reduce deaerator storage capacity to the absolute minimum as required solely for surge, but will also largely preclude the provision of additional static head for instant load reduction. As a result, enormous savings can be expected both from the deaerator itself and its supporting structures. The magnitude of savings in supporting structures alone may amount to more than a half million dollars for a 750 MW fossile unit. Based on the varying condensate temperature approach, mathematical equations expressing the deaerator pressure decay as well as design parameters required for designing the protective system have been derived. The paper also presents a detailed description of the recommended protective system and discusses some advantages of this system over the others. Finally, a few engineering examples are included to illustrate the application in system design.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):256-266. doi:10.1115/1.3445804.

A theoretical study of the correlation between droplet stream structure and steam turbine blading erosion is presented. To this end a simplified description of the motion of the individual droplet within the axial gap of a turbine stage has been used. It’s validity has been checked in an earlier paper [1]. The structure of the droplet stream has been defined by a distribution function assumed to depend, at a given gas velocity, on the droplet radius only. The family of these functions has been established by some experimental data; more knowledge in this field, however, is needed. The formulas for the mean values of some selected parameters of droplet impact have been developed, and some results of numerical calculations for two typical rotor blade profiles are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):267-273. doi:10.1115/1.3445805.

A feasibility study has been made of the use of a two-temperature, gas-particle suspension as the conducting medium in MHD generators. Large gas-particle temperature differences following nozzle expansions have been calculated, and the power generated by the use of these suspensions in MHD generator ducts has been investigated. Although relatively low gas temperatures have been considered, high electrical conductivities can be achieved by means of thermionic emission of electrons from high temperature particles. It is shown that total output power increases as gas temperature is decreased by means of continued nozzle expansion. Output power is also increased through the use of relatively large particles.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):274-282. doi:10.1115/1.3445806.

Earlier analyses of the laminar radically outward flow of Newtonian incompressible fluid between parallel corotating disks have been used to calculate the performance of multiple-disk pumps using such flow passages as the rotor. Such pumps are characterized by certain dimensionless parameters and a large number of computerized calculations have enabled preparation of pump performance maps for pumps idealized as having no losses external to the rotor; these maps show the quantitative dependence of pump efficiency, pressure change and required power on the pump geometry, speed, and on fluid properties. Conventional loss information for the pump entrance and diffuser flows, and conventional bearing, seal, and “disk friction” loss information, must be applied in the design process to provide prediction of actual pump performance and comparison with conventional pumps. The design information is also applicable to low-pressure gas blowers.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):283-291. doi:10.1115/1.3445807.

The purpose of this paper is to provide a method for estimating the deposition rate of the salt ejected in drift drops from a cooling tower in which salt water is circulated. The surface over which the salt will be distributed depends upon the wind speed, the maximum height the drops can reach, and the drop fall velocities. The drop fall velocity changes because of the evaporation in the air outside of the plume. The rate and extent of the evaporation is a function of the drop size, salt concentration, and ambient relative humidity. Three degrees of evaporation have been considered: (1) no evaporation; (2) evaporation to saturated solution and (3) evaporation to dry salt particles. For each degree of evaporation a graph was constructed that permits determination of the distance from the tower at which the salt contained in given drop size will fall. To use these graphs, the salt concentration, wind speed, and the maximum height a drop can reach must be known. The choice of the graph to be used for a particular case is made on the basis of humidity data for the site and the drift drop size. Corrections to compensate for the errors introduced by some of the assumptions are presented.

Commentary by Dr. Valentin Fuster
J. Eng. Power. 1974;96(3):292-306. doi:10.1115/1.3445808.

Eastern Europe is the world’s largest and most tightly knit multinational economic bloc. It is largest in population although its per capita energy output and industrial production lag considerably behind that of other industrial countries. Originally comprised of eight Soviet satelite states welded together by a common political-economic system patterned after that of the Soviet Union, Eastern Europe now includes Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania, which are members of the SEV (Soviet Ekonomicheskoy Vzaimopomoshchi, known as Comecon-Council for Mutual Economic Assistance), a highly integrated multinational group. Albania and Yugoslavia, both socialist economies of widely divergent philosophies, are not members of the SEV, although Yugoslavia’s specific status is defined by agreement formalized in 1964. The agreement laid the foundation for Yugoslav participation within the group (it has observer status in half of the Comecon’s 24 Commissions) and cooperation.

Commentary by Dr. Valentin Fuster

DISCUSSIONS

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster

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