Steam Jet Research Articles

Investigation of high speed steam jet effect on combustion of substandard liquid hydrocarbons

Combustion of liquid hydrocarbon fuel dispersed by superheated steam jet was experimentally studied. Characteristics of the combustion process (heat release, emission of toxic products, flame temperature) were investigated in a laboratory direct-flow atmospheric burner (capacity up to 20 kW) at different operating systems with waste transmission automotive oil as fuel example. Regimes were found which provoke stable combustion of non-quality liquid hydrocarbons. It was shown dependences of heat, flue gas parameters on superheated steam flow rates, fuel flow rates, flame temperatures.

Numerical analysis of the water steam jet gasdynamic parameters influence on the hydrocarbon fuel combustion in a pilot burner

On the basis of the conserved scalar approach with constrained-equilibrium chemistry model, variant numerical simulation of aerodynamics, heat transfer and the vaporized diesel fuel combustion processes, including soot formation and its effect on radiative heat transfer, has been performed in the pilot burner designed according to a concept of a hydrocarbon fuel combustion enhancement by axial injection of superheated water steam high-speed jet. The aerothermochemical structure of multicomponent reacting flow inside the burner has been analysed for the three cases of numerical study, including two regimes of the water steam axial injection with different jet velocity, and one regime of air injection through the same axial nozzle. The dependencies of the burner flame characteristics and its ecological performance on the given gasdynamic parameters of the discharged steam or air jet have been obtained. Also the numerical study has confirmed the low-NOx features of the burner operational regimes with water steam injection.

Investigating substandard liquid hydrocarbons spraying by a steam jet

Using the shadow photography (SP) method and the interferometric method (IPI), a two-phase gas-droplet flow was experimentally investigated when the spent transmission oil was sprayed by a jet of superheated steam. In a wide range of operating parameters, data on the dispersed composition of the steam-fuel jet have been obtained. The dependences of droplet sizes in the flow on the studied regime parameters have been established.

Physical characteristics of instanised cocholate powder sweetened with sucrose produced using continuous and batch type steam jet agglomerator: A preliminary study

Physical properties of instanised chocolate powder are not only determined by processing method, but also influenced by its ingredients. Thus, proportion of ingredients in cocoa drink should be also highly considered. This work investigated the impact of steam jet type and proportion of sucrose on the solubility and appearance of instanised chocolate powder. In this study, two types of steam jet agglomerator, namely continuous and batch type and three levels of sucrose proportion, namely, 15%, 30%, 45% were used as variables. The results showed that the type of Steam jet agglomerator, sucrose proportion and their interaction influenced the parameters investigated. In general, the solubility of instanised chocolate powder produced with continuous type is slightly higher than the solubility of instanised chocolate powder produced with batch type steam jet agglomerator. With regard to the appearance, it can be observed that the brightness of the cocoa drink produced with batch type is slightly lower than that of the cocoa drink produced with continuous type.

Numerical simulation of liquid hydrocarbon fuel burning in a direct-flow evaporation burner in a jet of superheated steam

In this work, the process of diesel fuel combustion in a laboratory sample of an original evaporation-type burner with superheated steam supply to the reaction zone was investigated by numerical simulation. Fuel burning in such a burner occurs in a steam jet flowing through the nozzle. In the framework of research, a mathematical model was developed, the influence of various models of turbulence, approaches to simulation of combustion, and response schemes were investigated.

CABARET scheme for modelling the stratification erosion in gas mixtures in hydrogen mitigation experiments for reactor safety

Experiments on atmosphere mixing and stratification in the large scale experimental facility (PANDA), where the initial helium stratification in a vessel is eroded by a vertical jet of steam, were simulated with the CABARET scheme. Good agreement between calculated and measured gas temperature and concentrations has been achieved by refining the mesh and adding the model of radiative heat transfer. The simulation results are presented and discussed.

Investigating characteristics of diesel fuel spray in a perspective burner

Gas-droplet flow at diesel fuel spraying by superheated steam jet has been experimentally investigated in this work with the use of interferometric method (IPI). Data on the dispersed composition of the steam-fuel jet have been obtained in a wide range of operating parameters (steam and fuel flow rates) corresponding to the area of stable operation of the burner. Dependences of droplet sizes in the flow on the regime parameters have been established.

Investigating the performance of Steam Jet Agglomerator as a mean to produce Instanised Cocoa Drink

Popularity of cocoa-based drink has been growing since long time ago in tropical countries. Iced cocoa drink is highly consumed due to the fact that the ambient temperature in the tropical region is relatively high. This condition stimulates cocoa drink industries to continuously improve the quality of their products. This work investigated the performance of small-scale steam jet agglomerator used to produce instanised cocoa powder. This small-scale machine is designed to increase the solubility of cocoa powder, thus cocoa powder will be easily solubilised in cold water. In this study, a small-scale steam jet agglomerator was manufactured. Afterwards, the impact of three drying times, namely 60°C, 80°C, 100°C and three levels of agglomeration process cycle, namely 1,2,3 cycles as well as their interaction on the solubility and colour of the products was investigated. The results showed that the solubility increased as the number of agglomeration process cycle increased. With regard to the colour, the brightness level decreased as the drying temperature and number of agglomeration process cycle increased.

Numerical study on mechanism of condensation oscillation of unstable steam jet

Submerged steam jet condensation is widely used in many industries. However, this process may cause damage to equipment due to pressure oscillation, especially at low steam mass flux. The dynamic process of steam bubble and different pressure oscillation types were investigated in this numerical study. Five typical stages were observed, which were bubble growth stage, bubble slow necking stage, bubble rapid necking stage, bubble detachment stage and secondary bubble oscillation stage. Two pressure oscillation types were found by the synchronization analysis of bubble pattern and pressure field. The mechanisms of condensation oscillation of unstable steam jet were revealed. As for the first type, two pressure peaks existed in the fluctuation process of secondary bubble volume. The higher pressure peak was generated when secondary bubble was oscillated to its minimum volume, and the other was generated when secondary bubble was collapsed. As for the second type, only one pressure peak existed and secondary bubble was quickly contracted without volume fluctuation. Pressure peak was generated when secondary bubble was quickly contracted to its minimum volume. Moreover, analyses of flow field pressure at different locations were carried out. Results indicated that the pressure fluctuation was mainly induced by the condensation oscillation of secondary bubble for both types. The trends of pressure at different locations were the same as that of secondary bubble internal pressure.

A quantification of penetration length of steam jet condensation in turbulent water flow in a vertical pipe

An experimental research is performed to investigate the penetration length of steam jet condensation in turbulent water flow in a vertical pipe. The penetration length of the condensing jet, with steam mass velocities ranging from subsonic to supersonic, was measured via utilizing a visualization window and a high-speed camera. At low steam flow rate a steam bubble plume forms, while at relatively high flow rate the bubbles in the plume coalesce and a steam jet is produced. Quantitative analyses of the interface behavior of the condensing jet are performed by exploring the transient and statistical characteristics of the jet penetration length. The waveforms of the transient jet penetration length exhibit that in the bubbling regime the period is approximately constant, while in the jetting regime the period varies a lot. The statistical analysis of the transient jet penetration length confirms that significant variations of the power distribution function (PDF) and power spectrum density (PSD) between the bubbling and jetting regimes occur at the transonic condition. The ratio of steam mass flux to critical steam mass flux at ambient pressure is found to have good linearity with the mean of the jet penetration length. And a linear correlation is fitted with a maximum absolute deviation of 5.5% between the measured and predicted values of mean of the jet penetration length. The relative unsteadiness of jet penetration length, defined as the ratio of the standard deviation to mean of transient penetration length, is approximately invariable in the bubbling and jetting regime. The bubbling regime contains more relative unsteadiness, while the jetting regime yield less relative unsteadiness. Because absolute instability exists in the subsonic region while no absolute instability occurs in the supersonic region, the transition from the bubbling to jetting regime occurs in the transonic region.

Experimental investigation on interfacial behavior and its associated pressure oscillation in steam jet condensation in subcooled water flow

An experimental study is performed to investigate mechanisms of the interfacial behavior and their associated pressure oscillations in steam jet condensation in subcooled water flow in a vertical pipe. The transient interfacial behavior of the condensing jet is first captured by a high speed camera, and then its parameters are quantitatively computed by using digital image processing technology. Pressure oscillations associated with jet interfacial evolutions are acquired by flush mounted pressure transducers with high frequency response on the wall. The interfacial behavior of the jet at two typical condensation regimes, i.e., bubbling regime and jetting regime, and their corresponding quantitative temporal and spatial evolutions of radial and axial interfaces and pressure oscillations are analyzed. With increase of steam mass flux, interfacial oscillations and pressure oscillations reach local maximum near the sonic point, and they remain almost unchanged after entering the supersonic region. Dominant frequencies of radial and axial interfacial oscillations and those of pressure oscillations are almost the same at subsonic and sonic conditions, while the dominant frequency disappears at supersonic conditions. Very strong correlations between interfacial oscillations and pressure oscillations are quantified through the oscillation intensity and correlation coefficient and also the power spectrum density, which confirms quantitatively that pressure oscillations are induced by interfacial oscillations of the jet.

Uphill quenching to reduce residual stress in a heat treatable aluminium alloy

ABSTRACTThree rectilinear blocks of the aluminium alloy 7449 were characterised using neutron and X-ray diffraction. One block was heat treated normally and two blocks were subject to uphill quenching from −196°C to 100°C. Boiling water and steam were used to rapidly increase the temperature of the blocks to reverse the thermal gradients introduced by cold water quenching. It was possible to detect the beneficial influence of uphill quenching on residual stress using either fluid. The influence of steam was very effective but localised and limited to the surface in close proximity to the steam jet. For more uniform stress relief, multiple steam jets will be required to ensure the entire surface receives a significant thermal input.

Visualization study on direct contact condensation characteristics of sonic steam jet in subcooled water flow in a restricted channel

Steam jet in subcooled water is a typical mode of direct contact condensation (DCC) where condensation occurs on the interface between steam and water. A visualization study of sonic steam jet condensation in subcooled water flow in a restricted channel has been performed for a convergent nozzle over a wide range of operating conditions. The DCC characteristics, including steam plume shapes, penetration length and average heat transfer coefficient, were discussed in detail. Method of digital image processing using MATLAB software was employed to evaluate steam plume shapes, penetration length, interface area and contours of gas volume fraction. Using a high-speed camera, five different steam plume shapes were typically observed, i.e. hemispherical, conical, contraction–expansion-contraction, ellipsoidal and divergent shapes, which are described in a three-dimensional map of plume shapes depending on steam mass flux, subcooled water temperature and Reynolds number of water flow. The measured data of dimensionless penetration length and average heat transfer coefficient are found to be in the range of 0.8–4.5 and 1.6–5.5 MW/(m2·K), respectively. By means of fitting 140 groups of measured data, the empirical correlations for dimensionless penetration length and average heat transfer coefficient as a function of dimensionless steam mass flux, condensation driving potential and Reynolds number of water flow were proposed. Both of the measured data and predictions show a good agreement with each other, which are suggested to predict the condensation characteristics of sonic steam jet in water flow in a restricted channel.

Modelling the Optimal Schemes of Population Vaccination Using Epidemiological Data

Condensation upon direct contact of the phases can be divided into the following types: condensation of the steam stream in the volume of unheated liquid; condensation of vapor bubbles in liquid; condensation of steam by liquid droplets (dispersed liquid); vapor condensation on a jet of liquid.In visual experiments, the study of the process of condensation of the jet of steam in space was noted by the presence of a white emulsion at the collision of steam with liquid, due to the crushing of a jet of steam into small bubbles. The high intensity of the heat transfer process was explained by the sharp increase in the contact surface. When considering the structure of the flow taking into account the two-phase region, it can be noted that there is a smooth conical surface of the separation between the phases and the formation of dispersed bubbles and droplets in the flow. This allows to determine the dependence of the geometry of the contact zone of the phases on the temperature head.An increase in the surface area of the contact phase can be achieved by dispersing one of the contacting phases. Existing liquid spraying machines have significant energy costs as a result of doing some work to overcome the surface tension that causes the liquid to reduce the free surface.So the heat transfer between a liquid drop and a saturated vapor is determined by the heat distribution along the drop radius. The vapor condenses on the surface of the liquid droplet, and the released heat condensation must be discharged inside the droplet. According to the equation of thermal conductivity under the relevant conditions of the problem under consideration, the intensity of condensation is determined by the rate of heat runoff per drop. Studies of heat exchange on dispersed jets of liquid have proven high intensity of the process.Condensation on a jet of liquid is used in many industrial devices (deaerators, condensers of mixing type, jet heaters).Theoretical and experimental studies of this type of condensation are scarce. Studies of heat exchange during condensation of a dispersed steam stream on a swirling stream of water are absent at all. The results of the experiments of heat exchange at the contact condensation of steam on jets of water, consisting of a continuous section and a section that falls into drops, are represented by the criterion equation. Recent studies are related to the development of a mathematical model for the calculation of jet condensation and analysis of past developments with its application.

Study of liquid hydrocarbons atomization by supersonic air or steam jet

In this work, the gas-drop two-phase flow characteristics in a perspective atomizing burner were measured with respect to operating conditions. The liquid fuel (diesel fuel and waste engine oil) was sprayed by a superheated steam or air jet. Data on the main parameters of such a gas-fuel jet (dispersed composition, carrier and dispersed phase velocity, jet opening angle) were obtained for various operating conditions (steam/air and fuel temperatures and flow rates) using modern optical flow diagnostics methods (SP, IPI, PIV, PTV). The flow structure, characteristic of a supersonic submerged jet with an opening angle of 20°, was registered near the nozzle. Characteristic diameter of the identified drops in all investigated modes is 10–20 µm, which is sufficient for efficient fuel combustion that proves the advantages of the investigated method of liquid fuel atomization. It has been established that operating conditions (such as gas or fuel temperature and fuel rates, ratio of flow rates) in the studied range slightly affects the change in the droplet size distribution. The research results showed that the size distribution of fuel droplets depends weakly on the choice of atomizing phase (steam or air).

Studying the diesel flame structure in superheated water vapor jets by using IR thermography

The use of water and water vapor in fuel combustion positively affects both environment parameters and the device stability. This is effective in the disposal of low-grade liquid hydrocarbons. The work is devoted to the experimental study of thermal characteristics of flame (effective emissivity and temperature) during the combustion of liquid fuel sprayed by a superheated steam jet, which is to supplement information on the steam effect on key parameters of fuel combustion. The measurements were carried out in a new burner at different operating parameters (fuel and steam mass flow rates and steam temperatures). During the first step of the research, high-quality liquid hydrocarbon (diesel fuel) is chosen, which is usually used in burners. In the study, we used a JADE J530SB FLIR thermal imaging camera and a type B platinum-rhodium-platinum-rhodium thermocouple. Instantaneous and average temperature fields were obtained; the peak flame temperature attained 1440 °C. It is found that the effective emissivity value (ε = 0.3 ÷ 0.4) depends on the steam and fuel flow rate that is connected with the completeness of fuel combustion and soot concentration in the flame. An increase in the steam flow rate decreases the flame temperature by more than 200 °C, which prevents the formation of thermal nitrogen oxides. The thermal imaging measurements well agree with thermocouple data (within 9%).

Synthesis of a CFD benchmark exercise based on a test in the PANDA facility addressing the stratification erosion by a vertical jet in presence of a flow obstruction

The benchmark exercise discussed in this paper was conducted within the OECD/NEA project HYMERES. The specific experiment in the PANDA facility chosen for the present benchmark addresses the stratification erosion in a vessel where the upper region contained initially a mixture of steam and helium, and the remaining volume was filled with steam. The mixing is induced by a vertical steam jet, which originates from the exit of a circular pipe located below the bottom of the helium-rich layer. The stratification erosion process is somewhat slowed down by a small circular plate above the jet source. The exercise consisted of a blind phase, and an open phase. Two sets of blind simulations were requested: one set obtained using a “common model”, and a second set produced by a “best estimate” model. For the “common model”, a list of recommendations was given, whereas for the “best estimate” model, each participant was free to choose the modelling approach. The submitted results for the erosion times were in a large band, and especially the large differences in the results with the “common model” were not expected. The results of the best estimate simulations showed that the combination of mesh and modelling approach can lead to a wide spread of results. The most important difficulty in interpreting the results and finding the reason of the large deviations was the lack of information on the velocity field downstream of the obstruction. Therefore, for the open phase extended data from auxiliary, “zero” tests (for similar conditions but without helium layer) were provided to the participants to permit a more basic validation of their models, using a “multi-step approach”. The step-by-step validation permitted some progress with respect to some of the items identified in the blind benchmark. However, large discrepancies with data in the final analyses of the test are observed, which cannot be easily attributed to specific model deficiencies or insufficient detail of the mesh. These results raised some questions in relation to best practice guidelines for the use of Computational Fluid Dynamic (CFD) codes for containment analysis and indicated needs for further CFD-grade experiments.

Experimental and theoretical study of pressure oscillation of unstable steam-air jet condensation in water in a rectangular channel

Pressure oscillation occurs during the steam jet condensation in water, notably in unstable flow pattern region. Consequently, pressure oscillation may risk the thermal system. In this work, we introduce a method of reducing the pressure oscillation intensity by adding a small amount of air into steam in unstable flow pattern region. The effects of the air content on the unstable flow patterns and pressure oscillation characteristics were studied experimentally. Notably, the air layer showed a periodic accumulation-and-dispersion phenomenon around the steam–water interface. This phenomenon resulted in a periodic and dramatic fluctuation of the interface at a relatively low air mass fraction. When the air mass fraction increased to a critical value, the flow pattern became stable due to a sharp reduction in condensation rate. Accordingly, the pressure oscillation intensity increased and then dropped at the critical air mass fraction, showing a convex-shaped distribution. The air mass fraction should exceed the critical value if air is added into steam to reduce the pressure oscillation intensity. Otherwise, the air could lead to a much stronger pressure oscillation. A theoretical model for the critical air mass fraction was established and could predict the critical air mass fraction within a deviation of ±14%.

Combustion of Substandard Liquid Hydrocarbons in Atmosphere Burners with Steam Gasification

In this research we experimentally investigated the process of liquid hydrocarbon combustion at spraying by a jet of superheated steam, using waste automobile transmission oil as an example. In the laboratory burner model (up to 20 kW) we studied the effect of mode parameters on the characteristics of the combustion process in the presence of superheated steam, namely, heat release and composition of combustion products, and flame temperature. The possibility of combustion of substandard liquid hydrocarbons in a straight-flow atmospheric burner at 10 kW is shown. Dependences of the main thermotechnical and environmental characteristics of the burner on temperature and flow rate of superheated steam and fuel consumption are found. The fuel combustion efficiency reaches 97%, observing minimal concentrations of toxic combustion products: {CO} = 20 mg/kWh{NO}x = 60 mg/kWh, which corresponds to class 3 of EN 267.

Characteristics of interfacial oscillation caused by condensation of steam jet in subcooled water flow

An experimental study is conducted to investigate interfacial characteristics of direct contact condensation of steam jet in counter-current subcooled water flow in confined conditions. A customized visualization window and a high-speed camera are combined together to capture and record the dynamical interface behavior of the condensing jet. The transient interface behavior of the jet is analyzed and discussed quantitatively by utilizing digital image processing technology. With increase of steam mass flux, the bubbling and jetting regime appear successively at subsonic conditions and sonic or supersonic conditions, respectively. The transient radial interface position along all axial locations downstream of the jet is obtained quantitatively for these two typical condensation regimes. The probability distribution function and power spectrum density of the radial interface position along all axial locations of a certain jet follow almost the same principles in the time-frequency domain. Significant variations of the probability distribution function and power spectrum density between the bubbling and jetting regimes happen at transonic condition. With increase of axial distance away from the nozzle exit, the probability of the pinch-off events first rise and then drops in subsonic and sonic conditions. While the jet interface is very stable and no pinch-off events occur in supersonic condition.