Variation Of Gas Temperature Research Articles

LDV measurements of axial drop velocity in evaporating, dense sprays

The axial component of the drop velocity was measured by laser Doppler velocimetry (LDV) within steady hexane-into-nitrogen sprays from a cylindrical nozzle at gas temperatures from 300 to 500 K. Also varied were the injection velocity and the gas-to-liquid density ratio. It was found that the gas temperature had no effect on the mean centerline velocity for distances smaller than 200 and greater than 650 nozzle diameters. At short distances, the core of the spray is not sensitive to the gas temperature; at long distances, the large amount of entrained gas renders inconsequential the degree of vaporization. Beyond 300 nozzle diameters, so much gas has been entrained that the mean axial velocity approaches the fully developed incompressible jet structure. The approach is accelerated by higher gas temperatures and gas-to-liquid density ratios. The axial drop velocity fluctuation amplitude responds to variations in gas temperature similarly to the mean axial drop velocity. Skewness and flatness indicate nearly Gaussian distributions near the axis and rapid increases beyond the half-radius and differ somewhat from those of incompressibl e jets, possibly because small drops vaporize fast and large ones do not follow the flow as closely as the small ones.

Gas temperatures and Penning collision rates in hollow-cathode metal-ion lasers

Gas temperatures along the axis of a hollow-cathode He-Cd laser have been measured. The effect of gas temperature variations on calculations of both the excited-state number densities and the heavy-body Penning collision rates are assessed. Implications on the gas kinetics of these discharge types, in particular, on the role of Penning collisions in populating the 5s2 2D5/2 level of the cadmium ion are discussed.

Measurement of the high combustion gas temperature in spark ignition engines

A new method ofmeasuring combustion gas temperatures has been developed, which is precise and easy to carry out. In this method, the output waveform of the radiant energy from the combustion chamber is graduated in terms oftemperature through calibration by means ofthe spectralD-line reversal method. Using the new method of measurement , the authors clarify the variation in the high combustion gas temperature, including that during abnormal combustion in a spark ignition engine.

The calibration of an aspirating conductivity-probe for thermal pollution experiments

This paper discusses the calibration and use of the Thermo-Systems Inc. aspirating probe in a particular application where temperatures of a hot gas plume are estimated from measurements on a dynamically similar helium—air plume. The probe is used as a constant-temperature hot-film anemometer but, being enclosed in series with a choked orifice, it responds primarily to variations in gas conductivity and temperature. T theoretical analysis of the response of the instrument in a helium—air mixture shows that a normalised calibration curve can be found, in which temperature effects are isolated at the all-helium and all-air reference points. The experimental calibration curves are similar to the theoretical form. The aspiring probe has poor resolution compared with more conventional gas-sampling instruments and is therefore not sufficiently sensitive for measurements of chemical pollution. Nevertheless, in the present application it is capable of resolving temperature differences of 0.3°C with a high frequency response and is therefore a valuable tool in the exploration of plume trajectories near the source in a turbulent wind.

Buoyant plumes of large-scale pool fires

A series of large-scale pool fire tests were conducted to investigate the variation of plume gas temperature and velocity. Three pool diameters: 1.219 m, 1.737 m and 2.438 m, were selected; four fuels with drastically different heat release rates were employed. In each test, measurements were made of plume gas temperatures and velocities and weight loss of the fuel pool. The measured plume temperature profiles at several elevations were fitted with Gaussian distributions in order to determine plume centerline position and centerline values of gas temperatures and velocities. The plume convective heat flux was then determined from the fitted profiles of plume temperatures and velocities. The plume centerline temperature followed the 2/3 power of the convective heat flux, Q c , and the −5/3 power of the pulme height with respect to the virtual source location, z-z o , down to the level where intermittent flames were found; the centerline gas velocity varied as the 1/3 power of Q c and −1/3 power of z-z o . The virtual source locations were found to be related to the flame heights. For large values of the ratio of flame height versus pool diameter, the distance from the flame tip to the virtual source is proportional to the 2/5 power of the convective heat flux and the virtual source location correlates well with a parameter 10 sed for flame correlation. For small flame-height to pool-diameter ratios, in several tests, the virtual source locations were below the pool surface; however, the virtual source moved upward as the pool diameter increased or the convective heat flux per unit pool surface increased.

Electron thermalization in gases. I. Helium

A theory is presented for the thermalization of subexcitation electrons in a monoatomic gas and calculations performed for helium. Evolutions of both the velocity and the position distribution functions are considered in an approximate manner. Of particular interest are the time scale for thermalization and width of the spatial distribution at thermalization. Satisfactory agreement has been obtained with experiments and earlier calculations, where comparison is possible. Additionally, time-dependent relaxation rates, diffusion coefficient and distributional widths have been introduced and evaluated. At a given gas temperature thermalization parameters are not sensitive to initial energy within the subexcitation range. Variation of gas temperature, on the other hand, produces significant changes in these quantities. Momentum transfer cross sections for lower energies have been taken from swarm drift data and, for higher energies, constructed from phase shifts measured by Andrick and Bitsch. Calculated thermal electron mobilities agree well with experiment at different temperatures.

ガス温度変化に対する熱線流速計の出力補正

ガス温度変化に対する熱線流速計の出力補正

Asymptotic theory of chemically unstable layer close to a perfectly catalytic wall

The statement and asymptotic solution of the problem of ionization equilibrium deviation near a perfectly catalytic wall in a weakly ionized gas is considered.Ratios of the unperturbed recombination length to the gas temperature variation scale and of the characteristic temperature of gas to the ionization potential are taken as the small parameters. The nonequilibrium layer is analyzed in detail using the method of merging asymptotic expansions in a small parameter. The physical meaning of obtained results is discussed.

A New Transducer for Respiratory Monitoring: A Description of a Hot‐wire Anemometer and a Test Procedure for General Use

A respiratory transducer based on the constant temperature anemometry principle has been developed for respiratory monitoring, and as a tool for bedside evaluation of pulmonary function. The transducer is characterized by a dynamic range from 0-2.5 1/s and an upper limiting frequency of 50 Hz. It is designed with a view to a low pressure drop of 2.5 mbar/1/s and a minimum dead space of 5 ml. The transducer has been tested using a generally applicable procedure which includes both static and dynamic test set-ups. The influence of variation in gas composition, temperature and pressure, together with variations in tidal volume and respiration rate, have been investigated. The results show that the transducer registers the immediate value of gas flow-rate with a mean error less than 5-10% in all situations which are predictable in clinical use. The mean error can be reduced to less than 5% when systematic errors are eliminated.

The thermal disturbance produced by an arc in a model gas-blast circuit-breaker

The properties of the thermal region surrounding the electrical core of a gas-blast arc have been measured using laser shadowgram and deflection mapping techniques. The arcs burned in an 11 mm long, 19 mm diameter orifice and were sustained by peak currents of 3 or 8 kA at a frequency of 85 Hz. The gas blast was driven by air stored at 7.8 bar in an upstream reservoir. Tests have been performed to investigate the influence upon the thermal region of different upstream electrode gaps, upstream electrode materials and geometries, and peak arc currents. Axial and temporal variations in the position of the thermal region boundary have been recorded throughout the arcing cycle, including the current zero period, and the transient variations of gas density and temperature within the thermal region have been determined. The results presented should enable empirical laws to be derived which form the basis of a boundary layer integral analysis of gas-blast arc behaviour.

Direct measurements of nighttime thermospheric winds and temperatures, 3. Monthly variations during solar minimum

We used a high-resolution Fabry-Perot spectrometer at Fritz Peak Observatory (39.9°N, 105.5°W) to determine the nighttime variation of thermospheric temperatures and winds from the line profiles and Doppler shifts of the O I 15,867-K (6300 A) line emission. With data obtained during the period April 1975 through March 1976 we examined the variation of the nighttime neutral gas temperature, zonal winds, and meridional winds at F layer heights throughout the year during solar cycle minimum. We compare our observed temperatures to predictions made by the MSIS (mass spectrometer and incoherent scatter) empirical model of neutral temperature and composition in the thermosphere. The calculated nighttime variation of thermospheric temperature is about 100°–150°K lower than measurements for summer and equinox months and about 50°–75°K lower than measurements for winter months. We compare the observed winds to the zonal and meridional winds, which we calculate from a three-dimensional semiempirical dynamic model of the thermosphere by using the pressure gradients specified by the MSIS model. The calculated nighttime winds are in general agreement with observed winds; both reveal a systematic monthly variation during geomagnetic quiet times. The nighttime equatorward meridional winds are greater in summer than in winter. The zonal winds are eastward throughout most of the night during winter; however, as the season progresses toward summer, a transition develops in the early morning hours from eastward to westward winds. This transition occurs earlier in the night as summer approaches. We use model predictions of the diurnal variations of winds and temperatures to calculate diurnal averages of the zonal and meridional wind components over Fritz Peak Observatory. The seasonal variation of these zonal mean values is presented.

The interdependence of droplet growth and concentration. I. Theory of droplet growth and applications on condensation nuclei counters

This paper reports theoretical investigations on droplet growth in monodisperse droplet ensembles. Computations are based on diffusion theory of single droplet growth. The mutual influence of growing droplets is taken into account by introducing slowly varying gas temperature and vapor pressure. The time course of droplet radius, gas temperature, and saturation ratio is evaluated numerically. As expected, stoppage of droplet growth at a terminal size is predicted dependent on droplet concentration and initial supersaturation. Gas temperature rises and saturation ratio decreases during droplet growth due to vapor consumption and heat production by the growing droplets. Based on computed droplet growth curves the response of condensation nuclei counters is investigated. Conditions for minimal counting losses and linear response are given.

Seasonal variations in the thermosphere above Millstone Hill

Incoherent scatter radar measurements gathered since 1969 at Millstone Hill (42.6°N, 71.5°W) are used to study the seasonal variations of the neutral gas temperature, composition and wind velocity in the thermosphere. Between 110 and 120 km, the mean temperature is found to oscillate with a 20 K annual amplitude, 10 K semiannual amplitude, and maxima in July; the mean density oscillates with an annual amplitude of 13% of the mean and a semiannual amplitude of 6% of the mean with maxima in November. Similarly, the mean daily exospheric temperature possesses a 100 K amplitude variation with a maximum in summer; the semiannual component is only about 10 K. Moreover, a weak winter maximum characterizes the neutral density at 400 km, and the neutral wind at 300 km is found to blow northward for a longer period during the day in winter than in summer. The amplitude and phase of the daily semidiurnal tides in the lower thermosphere do not vary systematically with season but a large variability is observed from day to day, particularly in the phase of the oscillation during winter. In contrast, the semidiurnal harmonic of the exospheric temperature varies seasonally in amplitude and phase and reflects the controlling influence of the length of the day on the shape of the daily temperature oscillation. In the middle thermosphere, the neutral composition ratio O/N2 is larger in winter than summer, with a rapid transition at the equinox.

Magnetic storm characteristics of the thermosphere

Energy and diffusive mass transport associated with the thermospheric circulation are considered in a self-consistent, though mathematically relatively simple form to describe in a three-dimensional two-constituent model magnetic storm characteristics in composition (N2, O, and He), temperature and mass-density. It is shown that during disturbed conditions the latitudinal variations of composition and gas temperature T sub g reflect the local nature of the magnetic storm heat input assumed to be primarily confined to the auroral zones. Thereby T sub g and N2 increase, He decreases and O remains constant through the auroral zones at exospheric heights (due to the superposition of temperature and diffusion effects) in agreement with OGO-6 mass spectrometer measurements. In contrast, the magnetic storm response in the total mass density is characterized by a strong world-wide component and a relatively insignificant increase toward the poles with the density peak occurring between two (poles) and eight (equator) hours after the maximum energy input, in substantial agreement with satellite drag data.

Gas-temperature measurement in pulsed H2O laser discharges

A spectroscopic technique of temperature measurement with submicrosecond time resolution, using ultraviolet OH emission, is described. The time varying gas temperature was measured during a 4-μsec 150-A current pulse through H2O. The gas temperature rose to 2000°K during the current pulse in pure H2O but to only 550°K in H2O–He discharges. The 2ν2 mode, which contains several lower laser levels, is pumped due to the gas heating. This tends to switch off the gain, attenuate the laser pulse, and make the medium lossy in the afterglow. Helium alleviates these problems by maintaing a low gas temperature.

Development of a Method for Measuring Rapidly Varying Gas Temperatures and Velocities

Development of a Method for Measuring Rapidly Varying Gas Temperatures and Velocities

Measurement of Combustion Gas Temperature of Internal Combustion Engine by Use of Ultrasonic Wave

The frequency of a sound wave is changed from the original one by passing through the rapidly temperature changing gas. The new technique for measuring the varying gas temperature by detecting the frequency change of the passing ultrasonic wave was applied to the temperature measurement of combustion gas in a four cycle reciprocating engine. For the check of the measured temperature using this new technique, the measured sound velocity was compared with that by the conventional direct sound velocity measuring method. As a result of the experiment, it was concluded that the new measuring technique was reliable.

Dual Mode Microwave Cavities for Dispersion Measurement

A technique has been developed for making precise measurements of refractive index dispersion in gases. The instrument, termed ``dispersometer,'' uses a cavity resonating in two modes simultaneously to measure the difference in index at two frequencies. Since the gas sample is common to both modes, effects of variations in gas pressure, temperature, and composition between samples are removed. In an early model, the precision of the measured dispersion was a few parts in 108 (of refractive index). The method has been used to date for a study of the 0.74 cm−1 water vapor line (reported separately) and should be equally applicable to other spectral regions, limited only by the available generation and detection devices.

Simulation of a thermal regenerator under conditions of variable mass flow

The naturally periodic characteristics of the regenerative heat exchanger are exhibited by the cyclic variation of the exit gas temperature. If it is required that the regenerator system should supply preheated gas at a constant temperature, then this can be achieved by the inclusion of a by-pass. The proportion of gas passing through the by-pass and the regenerator is then so controlled as to enable the preheated gas to be presented at constant temperature. This paper describes how the differential equations can be solved for such non-linear behaviour. The method developed can also accommodate the temperature dependence of the heat-transfer coefficients and the gas and solid specific heats.

Turbine-bucket temperatures with periodic variation in gas temperature

The turbine-bucket temperature is determined for a sinusoidal variation in the gas temperature. It is demonstrated that the bucket temperature varies with the same frequency as the temperature of the gas, with the amplitude of bucket-temperature fluctuations being smaller than the amplitude of gas-temperature fluctuation.