Radial Spray Research Articles

An ammonia flash break-up model based on bubble dynamics with force and energy analysis on droplet

Ammonia flash break-up model was developed using bubble dynamics based on force analysis of surface tension and pressure forces in this study. The initial bubble radius was calculated by modifying bubble number density equation considering the superheat degree with assuming a single bubble in the droplet. The Rayleigh–Plesset equation with compressibility factor was employed to calculate bubble growth in the liquid ammonia droplet. Droplet disintegration was predicted by force analysis. The velocity change by flash break-up was assumed to be a product of the surplus energy between the surface-energy change and the pressure work, and the bubble growth rate. The simulation results were compared to results in a previous experimental study of ammonia spray behavior. The time constant of the thermodynamic breakup model was added to simulate the flash boiling condition that induces rapid spray changes. In this study, the time constant 12 is used through the verification process. Compared with previous experimental results of ammonia flash boiling spray, the proposed flash breakup model was superior in predicting radial spray development by the flash boiling compared to the conventional aerodynamic breakup model.

Quantitative investigation of the evaporation and resistance characteristics of inlet jet precooling

Abstract A quantitative study is carried out to explore the air/mist-coupled cooling in the cooling section incorporating a spray device, aiming to conduct a comparative simulation on the effects of two radial spray arrangements (Apparatus A and Apparatus B) on the change of flow field. The results show that an even spray arrangement leads to improved flow performance owing to the large temperature drop in the cooling section. Compared with Apparatus A, Apparatus B enables a 1.60–2.25% higher temperature drop coefficient and a 1.1–3.0% higher water evaporation rate. Six high-altitude conditions are simulated to find that the spray device and water injection are the main factors causing flow loss, whereas the additional mass flow caused by water vapor reduces the amount of loss. The highest temperature drop coefficient is observed for Case 6 (27.3%), in which there is a more uniform nozzle arrangement. A slight difference in terms of total pressure drop coefficient between Apparatus A and Apparatus B is observed. Moreover, the highest total pressure drop coefficient (5.8%) at the location of the spray system is observed for Case 6, which has the largest injection rate and highest inlet air Mach number.

Experimental study on spray diffusion characteristics at various biodiesel-butanol blended ratios and ambient conditions

The depletion of fossil fuels and stringent emission regulations have encouraged the development of renewable fuels, especially biodiesel and alcohols fuels. The aim of the investigation is to explore the spray diffusion characteristics at different biodiesel-butanol blended ratios (0, 10%, 30%, and 50%), ambient temperatures (600 K, 700K, and 800 K), and pressures (1 MPa, 3 MPa, and 5 MPa). The experiment was carried out in a constant volume combustion chamber. The liquid- and vapor-phase spray images were captured by backlight illumination and schlieren imaging technique, respectively. The axial, radial, and spatial diffusion characteristics were analyzed, including spray penetration, cone angle, area, R-parameter, and perimeter ratio. Results show that in the case of biodiesel mixed with 10% n-butanol, for liquid-phase spray, the liquid-core spray with high concentration has the largest impact on axial diffusion, and for vapor-phase spray, axial dispersion is slower and radial diffusion is faster. The fuel density and ambient temperature have a more significant impact on the liquid-phase axial dispersion at the steady state compared with ambient pressure and injection pressure. At lower ambient pressures, increasing the injection pressure can accelerate the radial diffusion and increase the spray cone angle, which is opposite of the variation law at higher ambient pressures. The radial spray has a faster diffusion with adding a small or middle proportion of n-butanol, and the maximum values of liquid- and vapor-phase cone angles appear at biodiesel blended with 30% and 10% n-butanol, respectively. Moreover, the axial diffusion plays a dominant role in the spray spatial dispersion.

Transient radial spray from electrified viscous jets

An applied radial electric field can influence the instability and breakup behavior of a liquid jet. Particularly, when the electric field is sufficiently strong, a multi-cone-jet structure can be formed: a number of Taylor cones arise transiently at the equator of the most deformed droplet in the jet; from the tip of each cone, a fine secondary jet is emitted, which quickly breaks up into micrometer-sized progeny droplets. This tip streaming phenomenon is experimentally investigated for finitely conducting, viscous liquid jets in the present work. Different regimes are distinguished in the Be (the electric Bond number)-We (the Weber number) plane and also in the Be-We-Oh (the Ohnesorge number) space. The results show that both viscosity and inertia have a suppression effect on the formation of a multi-cone-jet structure. Moreover, the number of secondary jets can be greatly reduced by increasing viscosity or inertia. Increasing electrical conductivity leads to intense spray of secondary jets. In addition, some interesting phenomena like the coalescence of secondary jets and the coexistence of axisymmetric and non-axisymmetric instability are observed.

Development and test of an autonomous air-assisted sprayer based on single hanging track for solar greenhouse

Manual spray operations of conventional pesticides in the greenhouse are highly dependent on labor and have been associated with potential health risks. To overcome the constraints the narrow crop space and the complexity of auxiliary facilities impose on ground autonomous sprayers, this study developed an autonomous air-assisted sprayer based on a single hanging track for solar greenhouses. The spray distribution from the boom and spray patterns were evaluated. Laboratory tests were conducted to investigate the airflow distribution and static spray distribution of the boom. The sprayer was tested on cucumber crops in a solar greenhouse to evaluate the performances of two spray patterns: spraying during boom rising-traveling (P1) and during traveling-falling (P2). The coefficient of variation of the static axial spray distribution was 33% based on liquid collection. The coefficient of variation of axial and radial spray distribution of P1 and P2 (based on coverage rate) were 37.2% and 58.3%, as well as 46.3% and 69.4%, respectively. This confirmed that the motion direction of the boom strongly influenced the spray distribution. The structure of the airflow also affected the radial spray distribution. Moreover, the axial spray distributions of both spray patterns had high correlation coefficients of 0.921 and 0.889 with a static distribution detected in the laboratory. Optimizing the configuration of the nozzles and airflow of the boom is expected to further improve the uniformity of the radial and axial spray distributions. This autonomous air-assisted sprayer based on single hanging track provides a predictable solution for plant protection in solar greenhouses.

Investigation of the Spray Development Process of Gasoline-Biodiesel Blended Fuel Sprays in a Constant Volume Chamber

This study investigated gasoline–biodiesel blended fuel (GB) subjected to a fuel spray development process on macroscopic and microscopic scales. The four tested fuels were neat gasoline and gasoline containing biodiesel (5%, 20%, and 40% by volume) at three different ratios. The initial spray near the nozzle revealed that the spray penetration and spray tip velocity both decreased with decreasing biodiesel blending ratio. In addition, the different spray tip velocities at the start of spraying result in different atomization regimes between the fuels. The GB fuels with a low biodiesel blending ratio were disadvantaged in terms of spray atomization due to their lower spray penetration and tip velocity. The macroscopic spray penetration changes were similar to those observed in the microscopic spray. The fuel with the lower biodiesel blending ratio had a larger spray cone angle, indicating increased radial spray dispersion.

Experimental study of diesel fuel atomization performance of air blast atomizer

In this study, the spray performance of airblast atomizer is experimentally investigated under different operating conditions and different internal atomizer geometry. The used airblast atomizer is designed so that, the atomizing air is issuing from the atomizer with swirling motion. The swirling of the air blast is formed as passing the through a vane swirler fixed around the fuel exit. The investigated parameters are: the atomizing air swirler angle, the atomizing air to fuel mass ratio and the distance between the fuel nozzle exit and the atomizing air exit orifice. Four air swirlers with vane angels: 0°, 15°, 30°, and 45° are used. The distance between the fuel nozzle exit and the atomizing air exit orifice is changed from 0 to 3 mm. The fuel spray characteristics are studied then represented as spray shape and spray droplets intensities which are photographed using digital camera of particle image velocimetry (PIV). The radial spray concentrations are measured by using the tubes patternator technique. The spray cone angle is also measured under different operating conditions. The fuel used in this study is commercial diesel oil. The results indicate that, the spray cone angle increases with increasing the atomizing air to fuel mass ratio and also by increasing the atomizing air swirler angle while it decreases by increasing the distance between the fuel nozzle exit and the atomizing air exit orifice. The results also show, the spray concentration have its maximum values at the center line and decreases by moving radially outward. The spray intensities are clearly radially decreased. The spray cone angle is increased by about 142% (17°), 120% (18°), 123% (21°) and 120% (24°) for atomizing air swirler angle of 0°, 15°, 30° and 45°, respectively at constant value of the distance between the fuel nozzle exit and the atomizing air exit orifice ratio of zero.

Experimental study on the internal flow field and spray characteristics of hollow nozzle

In this paper, the internal flow field and atomization mechanism of a hollow nozzle under different inlet pressures were experimentally studied. The 3D print technology was used to develop a transparent hollow nozzle for visualization research. Variations in the spray cone angle, flow rate and radial spray density were also obtained under different working conditions. The results show that with the increase of inlet pressure, the growth rate of flow rate tends to be slower, and the air flow field in the nozzle swirl chamber is squeezed but with a more stable shape. In addition, the atomization is caused by the broken liquid film at the nozzle outlet. Furthermore, the spray cone angle was determined by the angle of the divergent section at the nozzle outlet under normal operating conditions, and the spray of the hollow nozzle exhibit a regular shape of annulus. As the inlet pressure increases, the effective spray area extends to the center as a whole, and the peak value of spray density also increases obviously. The effect of the increasing spray height is contradictory to that of increasing inlet pressure.

Variable air assistance system for orchard sprayers; concept, design and preliminary testing

Conventional air-assisted sprayers with hydraulic nozzles generate large radial spray plumes which produce significant off-target losses and can consume high power (20–30 kW). Also, it is not uncommon to see these machines treating dwarf orchards, where the spray losses at the full leaf stage may be over 80% of applied spray volume. Significant reductions in spray losses can be obtained with targeted and wind-oriented airflow adjustment. The objectives of the presented studies were to develop an energy saving variable air assistance (VAA) system with continuous real-time adjustment of air volume and with spraying systems mounted on both sides of the sprayer. The system is based on a double axial fan system which allows for remote adjustment of air volume. The nominal air output was 20,000 m3 h−1, for use in typical dwarf and semi-dwarf orchards, and this was designed to be obtained with 10 kW power consumption. The system used variable speed impellers with fixed blades which showed greater suitability than a method with adjustable pitch blades working at constant speed because it provided a wider range of air volumes (±35%). The air volumes produced could be continuously adjusted to obtain airflow profiles, on both sides of the sprayer that were almost symmetrical. The results obtained in tests appear to meet the objectives and, therefore, the VAA system can be considered as a suitable prototype platform for variable rate technology and future intelligent orchard sprayers.

Analysis of the repeatability of fuel spray indexes in a spray-guided direct-injection spark-ignition engine

The development and research works on liquid fuel injection in spark-ignited direct injection (SIDI) engines, apart from so common in recent years simulation methods, still have a significant cognitive substrate. This is related to experimental research on repeatability of combustion process using multi- and mono-cylinder test engines and Rapid Compression Machines. The repeatability of preparation and delivery processes has immediate impact on repeatability of combustion process. Except for the necessity of obtaining the repeatability of fuel amounts, the repeatability of injected fuel spray is required. The penetration range and spray area in combustion chamber have direct impact on mixture creation and formation. The optical research on fuel injection has been made in order to determinate its repeatability. The research on unrepeatability of fuel spray propagation has been conducted using piezoelectric injectors of outward-opening type, being primary elements of the spray-guided combustion systems. The results of research were presented in the form of index of variation of the selected parameters. The evaluation of the results of the optical research concerns radial spray penetration and fuel spray velocity. Unrepeatability has been presented with coefficient of variation of radial penetration in relation to the time of injection duration. It has been observed that the coefficients of various parameters are lower with longer times of fuel injection.

Numerical and experimental investigation of induced flow and droplet–droplet interactions in a liquid spray

An Euler–Lagrange model is presented that describes the dynamics of liquid droplets emerging from a high-pressure spray nozzle in a relatively large volume (of the order of almost a cubic meter). In the model, the gas phase is treated as continuum, solved on an Eulerian grid, and the liquid phase is treated as a dispersed phase, solved in a Lagrangian fashion, with interphase coupling through state-of-the-art drag relations obtained from direct numerical simulations. The droplets are introduced into the system at high velocities, leading to a turbulent self-induced gas flow which is solved using large eddy simulation. Despite the relatively low liquid volume fraction in the spray, the number density of droplets at the nozzle is still more than 1010m−3, which is why we employ a highly efficient stochastic Direct Simulation Monte Carlo approach to track collisions between droplets. The droplet collision frequency is calculated on the basis of local droplet number density, droplet size and relative velocities of neighbouring droplets within a dynamically adapting searching scope, as described in Pawar et al. (2014. Chem. Eng. Sci. 105, 132–142). We use known correlations from literature to determine the outcome of a binary droplet collision, which depending on characteristic dimensionless numbers can be coalescence, bouncing or, for high velocity impacts, stretching or reflexive separation leading to formation of satellite droplets. Our simulation model is compared with droplet velocities and size distributions obtained from phase Doppler interferometry experiments on an industrial scale hollow-cone pressure swirl nozzle spray. We find semi-quantitative agreement for spray characteristics such as the axial and radial spray velocity, spray jet width, and the dependence of the droplet size distribution on position within the spray. The simulation model enables us to study the relative importance of different droplet collision events occurring in the spray volume.

Visual characterization of heated water spray jet breakup induced by full cone spray nozzles

The present work with specific objectives places a greater emphasis on measurements of the breakup lengths and phenomenological analysis of a hot water jet under reduced pumping pressures in still environment. Therefore, visual and comparative studies are conducted on full cone jet disintegration of heated water for low pumping pressures. A further analysis of the grabbed images confirms the strong influence of the input processing parameters on full cone spray patternation. It is also predicted that the heated liquids generate a dispersed spray pattern by utilizing partial evaporation of the spraying medium. The radial spray cone width and angle do not vary significantly with increasing Reynolds and Weber numbers at early injection phases, leading to enhanced macroscopic spray propagation. The discharge coefficient, mean flow rate, and mean flow velocity are significantly influenced by the load pressure, but less affected by the temperature. The fine scale image analysis also predicts toroidal-shaped vortex formation in the spray structure near the water boiling point.

Effect of turbulence non-isotropy modeling on spray dynamics for an evaporating Acetone spray jet

The effect of turbulence closure on spray dynamics is studied for three dilute Acetone spray jets using an Eulerian–Lagrangian approach with two-way coupling. A stochastic random walk algorithm is employed to model the droplets’ dispersion. Simulations using different turbulence closure models (i.e. the isotropic SST-k-ω, and the k-∊ realizable models, and the non-isotropic Reynolds Stress Model (RSM)) are compared with the Sydney spray measurements for SP2,SP6, and SP7 spray conditions (Gounder et al., 2012). The experimental mass flow rate, spray mean and rms data are injected for each available size bin during the numerical simulations. Overall, the simulations show good comparisons with the mean and rms spray measurements. The turbulence closure non-isotropy modeling shows relatively weak effect on the spray mean velocity and size profiles predictions, where the RSM predictions was slightly better at the centerline at x/D=10 and x/D=20 for the SP2 mean axial velocity, with similar predictions to the k models for the SP6 and SP7. The RSM, however, consistently predicts better rms axial and radial spray velocity distribution, which indicates more realistic droplet dispersion than the isotropic SST-k-ω and the k-∊. The RSM gas phase shear stresses show that close to the nozzle (i.e. at x/D=5 and x/D=10) the turbulence non-isotropy increases as we approach the centerline and is maximum at the shear layer location at x/D=5. On the other hand, at the downstream locations at x/D=30 the turbulence field non-isotropy increases at the jet edge. A conical region of large size mean droplets (D10>26μm) is observed around the SP2 jet edge. This region disappears quickly for the SP6 and SP7 after the inflow section. The data analysis exhibits that the RSM predicts higher Stokes number than the SST-k-ω due to faster mixing time scales. For the impact on dynamics, at the centerline the SST-k-ω and k-∊ models, predict higher droplets’ slip velocity, higher drag force, and faster droplet’s response than the RSM. The droplets’ tendency for cross-stream dispersion is also found to vary with the turbulence model. The fan spreading phenomenon is observed at the down stream locations away from the nozzle. The results show that the spray turbulence is non-isotropic and lags the gas phase rms values, especially at the centerline. This discrepancy decreases downstream and towards the jet edge. The study shows the importance of non-isotropy modeling on the droplets dispersion and spray dynamics predictions.

Characterization of Modified Tapioca Starch Solutions and Their Sprays for High Temperature Coating Applications

The objective of the research was to understand and improve the unusual physical and atomization properties of the complexes/adhesives derived from the tapioca starch by addition of borate and urea. The characterization of physical properties of the synthesized adhesives was carried out by determining the effect of temperature, shear rate, and mass concentration of thickener/stabilizer on the complex viscosity, density, and surface tension. In later stage, phenomenological analyses of spray jet breakup of heated complexes were performed in still air. Using a high speed digital camera, the jet breakup dynamics were visualized as a function of the system input parameters. The further analysis of the grabbed images confirmed the strong influence of the input processing parameters on full cone spray patternation. It was also predicted that the heated starch adhesive solutions generate a dispersed spray pattern by utilizing the partial evaporation of the spraying medium. Below 40°C of heating temperature, the radial spray cone width and angle did not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The discharge coefficient, mean flow rate, and mean flow velocity were significantly influenced by the load pressure but less affected by the temperature.

Characterizing Diesel Fuel Spray Cone Angle From Back-Scattered Imaging by Fitting Gaussian Profiles to Radial Spray Intensity Distributions

Quantifying fuel spray properties including penetration, cone angle, and vaporization processes sheds light on fuel-air mixing phenomenon, which governs subsequent combustion and emissions formation in diesel engines. Accurate experimental determination of these spray properties is a challenge but imperative to validate computational fluid dynamic (CFD) models for combustion prediction. This study proposes a new threshold independent method for determination of spray cone angle when using Mie back-scattering optical diagnostics to visualize diesel sprays in an optically accessible constant volume vessel. Test conditions include the influence of charge density (17.6 and 34.9 kg/m3) at 1990 bar injection pressure, and the influence of injection pressure (990, 1370, and 1980 bar) at a charge density of 34.8 kg/m3 on diesel fuel spray formation from a multi-hole injector into nitrogen at a temperature of 100 °C. Conventional thresholding to convert an image to black and white for processing and determination of cone angle is threshold subjective. As an alternative, an image processing method was developed, which fits a Gaussian curve to the intensity distribution of the spray at radial spray cross-sections and uses the resulting parameters to define the spray edge and hence cone angle. This Gaussian curve fitting methodology is shown to provide a robust method for cone angle determination, accounting for reductions in intensity at the radial spray edge. Results are presented for non-vaporizing sprays using this Gaussian curve fitting method and compared to the conventional thresholding based method.

Structure of evaporating single- and multicomponent fuel sprays for 2nd generation gasoline direct injection

In the present paper the effect of fuel properties on spray formation and evaporation was investigated for a hollow-cone spray of a piezoelectric injector for Direct Injection Spark Ignition (DISI) engines. Late injection timing in a high-pressure atmosphere (1.5 MPa, 200 °C) was simulated in an injection chamber. Liquid and vapor phase structure of the hollow-cone spray were studied with 2D-Mie scattering, laser-induced fluorescence (LIF) as well as phase-Doppler anemometry (PDA). The spray structure was investigated for several alkanes with high and low volatility ( n-hexane, n-heptane, iso-octane, n-decane) and a three-component mixture of the n-alkanes with similar fuel properties like a multicomponent gasoline fuel. It is found that the rapid evaporation of high volatility fuels can lead to spray destabilization, whereas low volatility single-component fuels overestimate radial spray propagation and vortex formation. For iso-octane the droplet size distribution is shifted to smaller droplets and the spray appeared to be less dense compared to n-heptane despite almost identical boiling behavior. However, the much higher viscosity of iso-octane determines the internal nozzle flow which results in a reduced injected fuel mass and changed atomization. A well defined three-component fuel models the global spray characteristics as well as the droplet size, droplet momentum distribution and evaporation behavior of the used multicomponent gasoline fuel very precisely. Small amounts of low volatility fractions delay the droplet evaporation and support the overall spray stability also for multicomponent mixtures. This leads to an increased spray width as well as larger droplet sizes and momenta. The evaporation characteristic of multicomponent fuels at increased ambient pressure is complex. At the studied injection conditions it is situated between the two limiting cases of distillation-like behavior and coevaporation of the components. Moreover, the results in comparison with theoretical estimations indicate a demixing of light and heavy boiling fractions in the three-component and multicomponent fuel under conditions which are typical for DISI strategies with late injection.

PRESSURE—SWIRL ATOMIZATION OFWATER-IN-OIL EMULSIONS

The pressure−swirl atomization of surfactant stabilized and natural, unstable water-in-oil emulsion fuel injected into an ambient environment is investigated experimentally. Fuel flow conditions are typical of large-scale gas turbine applications. A specialized setup generates controlled emulsions stabilized by addition of surfactants. The emulsion generation process allows control over the discrete phase (water) droplet size distribution within the emulsions. The spray droplet sizes are measured using laser diffraction and the spray pattern is evaluated using imaging and mechanical patternation. A statistically designed experimental test matrix was executed and the results were subjected to the analysis of variance. We find that emulsification can reduce or increase the average droplet size in the spray depending upon the added amount of water fraction. The atomization process itself can change the size distribution of the discrete phase depending upon the initial sizes present and the injector pressure differential. The fractions of oil and water phases were observed to vary with radial spray angle for the stabilized cases considered. For the conditions studied, the stabilized emulsions performed very similarly to natural unstable emulsions as long as the unstable emulsion was produced shortly prior to atomization (i.e., <1 sec) with sufficient shear as to result in a fine discrete phase droplet size. Overall, the results provide insight into how the emulsion properties influence their atomization. Findings show that injection pressure and emulsion discrete water fraction affect the spray droplet size distribution most substantially, while the fine emulsion water droplet distributions play a less significant role. The composition of the emulsion spray appears to vary spatially and temporally when emulsions are coarse. Stabilized and naturally unstable emulsions demonstrate similar breakup behavior during atomization.

Correlations between the two-phase gas/liquid spray atomization and the Stokes/aerodynamic Weber numbers

The The effects of air-to-liquid ratio (β) and void fraction (α) on Sauter mean diameter (SMD or D32), arithmetic mean diameter (D10), surface mean diameter (D20), volume mean diameter (VMD or D20), and radial velocity profiles were experimentally investigated for a two-phase gas/liquid (TPGL) nozzle with a hybrid design of classical twin-fluid and effervescent nozzles. Radial spray profiles were measured using a Phase-Doppler-Particle-Anemometer (PDPA) system on 15Dn, 30Dn, 60Dn, 120Dn;(Dn represents nozzle diameter = 3.10,mm) axial distances. In addition, the effects of spray break-up patterns were analyzed with changing axial distances. The average void fraction in the feeding conduit (FC) was measured by a pneumatic controlled quick-closing-valve (QCV). The experiments were performed using mixtures of air with water at water flow rates of 1.50 to 7.50 kg/min and air-to-liquid mass ratios (β) of 0.30 to 10;%. The length and diameter of the FC was 36.8,cm and 6.35,mm, respectively. Result indicates that as the St number reaches the value of one, no more break-up continues, thus the droplets start to coalesce each other forming bigger droplets (higher D10 values) with increasing radial distances. Knowledge from this study will provide better understanding that ensures an increase in plant efficiency and product yield in oil sands bitumen upgrading.

Water efficiency in leisure centres

Overall use of water in an urban indoor leisure centre can be high, so that there are significant incentives to save water, both for direct cost reduction and for indirect saving through the reduction of embedded energy. In addition, both privately owned- and local authority-run leisure centres need to show savings in order to manage drought requirements. Analysis of the temporal patterns and volumes of water used in the different activities with a leisure centre, such as swimming pools, showers, toilets and others can point to where cost-effective saving measures can be implemented. This paper will focus on the factors that must be considered when attempting to reduce the use of water in ‘power showers’ and is derived from a programme commissioned by United Utilities Plc at Liverpool John Moores University, aimed at reducing domestic water consumption. The results of focus group studies, laboratory trial and home trials can easily be extrapolated to the leisure centre. In order to persuade the user to accept a lower water use it is essential to sustain the ‘shower experience’ to maintain user satisfaction. A range of commercially available domestic showerheads was examined to determine flow characteristics, (pressure–volume) radial spray distributions at different flow-rates, direct and indirect measures of ‘skin pressure’ and measurements of vertical temperature profiles. Some simple correlations were derived but it is not easy to relate these to user satisfaction.

Saving water in showers

This project is part of a programme aimed at reducing water consumption. Power showers are water inefficient, but in order to persuade the user to accept a lower water use it will be necessary to sustain the "shower experience" to maintain user satisfaction. Previous work has indicated that users' requirements include temperature stability, adequate water volume and distribution, and skin pressure, all of which are substantially controlled by the showerhead. In the present phase of the project several commercially available domestic showerheads have been examined to determine pressure-volume characteristics, radial spray distributions at different flow rates, direct and indirect measures of "skin pressure" and measurements of vertical temperature profiles. Part of the practical work at LJMU has supported extensive theoretical studies by CFD carried out by staff at Arup (consulting engineers) for the Market Transformation Programme. A future phase will study user satisfaction in their own homes where user satisfaction will be surveyed and linked to the physical performance of the shower.