Contains report on status of research for two research projects.U. S. Air Force (Research and Technology Division) under Contract F33615-67-C-1148 with the Air Force Aero Propulsion Laboratory, Wright-Patterson Air Force Base, Ohi

Kerrebrock, J. L.

Contains a report on status of research.U.S. Air Force (Research and Technology Division) under Contract F33615-67-C-1148 with the Air Force Aero Propulsion Laboratory, Wright-Patterson Air Force Base, Ohi

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XIV. ENERGY CONVERSION RESEARCHAcademic and Research StaffProf. J. L. KerrebrockProf. G. C. OatesGraduate StudentsR. DecherM. L. HougenG. W. Zeiders, Jr.A. STATUS OF RESEARCH1. ALKALI-METAL VAPOR STUDIESOur studies of the condensing plasma, both theoretical and experimental, indicatethat probably it will not be feasible to maintain a state of nonequilibrium ionization ina wet vapor. This conclusion follows from two facts.a. At moderate current densities, the moisture increases the slope of the curve oflog a versus log j to greater than unity. With this characteristic, the plasma isunstable to current concentration.b. At higher current densities, the flux of energy to the liquid droplets is such asto evaporate them quite rapidly.Thus we are forced to the conclusion that an alkali-vapor MHD generator shouldoperate with dry vapor. Our evaluation of the system potential will proceed on thisbasis.2. LARGE NONEQUILIBRIUM GENERATORDuring this quarter, the large generator was operated twice with a pre-ionizer. Inthe first run, load resistances from 100 to 3 ohms per electrode pair were used. Pres-sure distributions along and across the channel were taken. Although the data are stillbeing analyzed two points can be made.a. When the pre-ionizer was operating, the pressure distribution in the channel wasnearly independent of load resistance. When the pre-ionizer was turned off, the pres-sure rose throughout the channel, the increase being approximately 30%o at the entranceand a factor of two at the exit. This may indicate a large increase in dissipation whenthe pre-ionizer is off.b. The performance of the channel appeared to improve slightly with time duringThis work was supported by the U.S. Air Force (Research and Technology Division)under Contract F33615-67-C-1148 with the Air Force Aero Propulsion Laboratory,Wright-Patterson Air Force Base, Ohio.QPR No. 85 217(XIV. ENERGY CONVERSION RESEARCH)the run. Because of this, the second run was made with a fixed-load resistance of3 ohms, in an attempt to define the time dependence of the performance. The data fromthis run have not yet been analyzed.3. INSTABILITIESA general theoretical study of MHD instabilities is being made, which encompassesboth magnetoacoustic and electrothermal waves, and accounts for interaction betweenthe two. It also includes the effects of radiative heat loss.J. L. KerrebrockQPR No. 85 218

Energy Conversion Research

Contains research objectives.U. S. Air Force (Research and Technology Division) under Contract F33615-67-C-1148 with the Air Force Aero Propulsion Laboratory, Wright-Patterson Air Force Base, Ohi

XXVI. ENERGY CONVERSION RESEARCH*Academic and Research Staff- --Prof. J.Prof. M.Prof. A.L. KerrebrockA. HoffmanSolbesR. DecherH. J. DeJongGraduate StudentsM. L. HougenE. D. RileyRESEARCH OBJECTIVES AND SUMMARY OF RESEARCHOur research is a continuing study of advanced concepts in energy conversion. Theobjectives of this program are to identify promising new methods of energy conversion,and to carry out the research required to demonstrate their technical feasibility.We have been exploring the feasibility of Rankine-cycle space power systems incor-porating nonequilibrium magnetohydrodynamic generators. At present, the major effortis directed toward obtaining a basic understanding of the behavior of such generators,by operating and analyzing a generator of realistic size.We are also exploring the system aspects of nuclear-MHD power systems.Our major effort during the past quarter has been the analysis of the data obtainedfrom the generator runs of the previous quarter. The doctoral thesis of Reiner Decherhas been completed.Some attention has been given to the design of an improved preionizer. It appearsthat a magnetically spun discharge just upstream of the nozzle throat is the best choice.Such a device will be constructed.J. L. KerrebrockThis work is supported by the U. S. Air Force (Research and Technology Division)under Contract F33615-67-C-1148 with the Air Force Aero Propulsion Laboratory,Wright-Patterson Air Force Base, Ohio.QPR No. 88 231

XVI. ENERGY CONVERSION RESEARCH*Academic and Research StaffProf. J. L. KerrebrockProf. G. C. OatesProf. A. SolbesGraduate StudentsR. DecherM. L. HougenG. W. Zeiders, Jr.A. STATUS OF RESEARCH1. ALKALI-METAL VAPOR STUDIESAs we have noted in Quarterly Progress Report No. 85 (page 217), we have con-cluded that it is not feasible to attain nonequilibrium ionization by electron heating in awet alkali vapor. A further conclusion which has been drawn from recent theoreticalwork is that such ionization strongly inhibits nucleation, and hence condensation, in asupersaturated vapor. Essentially, this is due to the tendency of the droplet tempera-ture to equilibrate with the electron temperature, rather than with the gas temperature.2. NONEQUILIBRIUM GENERATORSeveral experiments have been conducted with pre-ionization during this quarter.Although there has been some difficulty in obtaining reliable pre-ionizer performance,the results are very encouraging. The transverse current per electrode pair at shortcircuit increased from approximately 1 amp (. 14 amp/cm 2 ) at the inlet to 27 amp(4 amp/cm2) beyond the center of the channel. The Hall electric field was everywheremuch less than the ideal value, but increased from 200 vm-I at open circuit to 600 vm-as short circuit was approached. Correcting for this small Hall field, we find a scalar-1conductivity of approximately 200 mho m-1 near the center of the channel. The value-1expected at inlet to the channel with pre-ionization was approximately 10 mho m- , andthis is consistent with the measured currents in the first few electrode pairs.J. L. KerrebrockThis work was supported by the U. S. Air Force (Research and Technology Division)under Contract F33615-67-C-1148 with the Air Force Aero Propulsion Laboratory,Wright-Patterson Air Force Base, Ohio.QPR No. 86 193

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Energy Conversion Research

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