Spray Plume Research Articles

Influence of the initial droplet distribution on the prediction of spray dynamics in Eulerian-Lagrangian simulations

Liquid fuel atomisation is largely affected by in and near nozzle phenomena. In this paper we establish a link between the initial droplet distribution at the nozzle exit, used as an input parameter in Lagrangian solvers, and the effect that this selection has on the subsequent predicted spray physics. Three initial PDFs with similar mean but different variance are tested in order to represent different aspects of the injection physics. Results are validated against an extensive range of experimental data from the Engine Combustion Network for the mildly cavitating Gasoline Spray G. Gasoline Direct injectors present high complexity both due to the importance of the near-nozzle phenomena for the fuel-air mixing, as well as due to the spray plume to plume interactions further downstream. Thus, they provide a well suited benchmark case for our study. We conclude that a correctly selected initial mean droplet size in combination to standard evaporation and break up models can provide reasonable predictions for a range of quantities including liquid and vapour penetration. Different droplet distribution models though exhibit differences in their prediction accuracy in terms of droplet dynamics depending on the initial droplet size variation around the mean. We demonstrate that these differences affect the coupling between the Lagrangian and the Eulerian dynamics through a Stokes numbers analysis close to the nozzle. We also analyse the effects that the stripping and catastrophic break up mechanisms have on the evolution of the droplet PDF at different axial locations depending on the selected initial droplet sizes. Overall, our results allow for a better understanding of the influence of the Lagrangian model input parameters on the global spray development on a numerical level, but can also help the optimisation of the design of new injectors by improving the understanding of the link between initial droplet distributions and the physics of the spray further downstream.

Computational fluid dynamic simulation of a pulse-width modulated spray nozzle

Computational fluid dynamics (CFD) is a useful tool used by engineers in many industries to study fluid flow. A relatively new industry to adopt the use of CFD is the agricultural industry. A spray nozzle commonly used in agricultural spraying, the Teejet 110-degree nozzle (TeeJet Technologies, 2020), was simulated. A method was developed to pulse the spray. A user-defined function was used to define the velocity at the inlet of the nozzle to pulse the spray. The domain was then extended to allow the examination of a slice 20 inches below the nozzle. The simulation results were compared to experimental results collected from a sprayer testbed. The effect of frequency was then investigated by changing the frequency of the pulses. Results from these studies show that a userdefined function can be used to pulse the spray. CFD can be used to model spray nozzles, but the validity of the results are strongly related to the computational resources available, and increasing the frequency of the pulses results in a higher concentrated spray toward the center of the spray plume. The simulations were carried out using a commercial code (CD-Adapco, 2019).

Numerical Simulation of the Electrostatic Coating Process: the Effect of Applied Voltage, Droplet Charge and Size on the Coating Efficiency

<div class="section abstract"><div class="htmlview paragraph">Electrostatic Rotary Bell Sprayers (ERBSs) have been widely used in the painting industry, especially in the automotive and aerospace industries, due to their superior performance. The effects of the applied voltage and paint droplet charge values on the spraying pattern and coating Transfer Efficiency (TE) in the ERBS, including a high-voltage ring for spray cloud control, have been studied numerically in a wide range of droplet size distribution. A 3D Eulerian-Lagrangian numerical analysis is implemented under the framework of the OpenFOAM package. The fluid dynamics of turbulence, primary and secondary breakup procedures are modeled using a large eddy simulation (LES) model, Rosin-Rammler distribution, and modified TAB approach, respectively. Compared to the conventional ERBSs, in the current work an exhaustive exhibition of the airflow dynamic and spray pattern characteristics around the ERBS with outer high-voltage control-ring field pattern, i.e., velocity, vorticity, electric potential field, overspray, film thickness are reported. Our findings indicate that the control-ring around the rotary bell rim improves the coating procedure TE and produces a more harmonized and narrower spray plume. Our in-depth investigation clearly shows the importance of the droplet charge values, voltage quantity, and considered droplet size range on the film thickness and its corresponding quality that is obtained from the workpiece.</div></div>

Numerical analysis of charged droplets size distribution in the electrostatic coating process: Effect of different operational conditions

This paper presents a numerical performance evaluation of the electrostatic rotary bell sprayer (ERBS) with a particular focus on droplet charge, electric field, and ambient conditions through the implementation of a high-voltage control-ring field pattern effect into the fully turbulent airflow and by including the atomized droplets discrete phase. The simulation shows that the inclusion of droplet charging and electric field coupling, with different parametric values, significantly impacts the atomized droplet distribution over the spray plume and the deposition rate. This analysis was conducted using a three-dimensional (3D) Eulerian–Lagrangian model to describe the two-phase spraying flow by extending the base OpenFOAM package. The procedure includes an unsteady compressible Navier–Stokes solver combined with a large Eddy simulation approach to model turbulence effects on the air flowfield. This is coupled to the spray dynamics by including droplet trajectory tracking, wall film dynamics, and electric field charge. The approach is further extended to include the evaporation phenomenon and the transport of its products. Compared to a conventional ERBS, herein, we provide an in-depth analysis of the fluid dynamic characteristics around the ERBS with a control-ring field pattern for vorticity, velocity, and electrical fields. The results indicate that the control-ring operation improves the performance and transfer efficiency of the ERBS, and it also helps to harmonize the direction of the charged paint droplets. For the first time, finding a balance between the effect of the inside bell cup surface and control-ring voltage and charged droplet has been conducted.

Simulation of Liquid Film Spreading on Tip of Spray Injector

The behaviors of fuel films adhering to the tip of a fuel injector for automotive gasoline direct-injection engines was simulated by the computational fluid dynamics. Liquid film adhering to the tip of the fuel injector is a source of carbon deposits; the film spreads on the surfaces of the tip and remains there under certain wetting conditions. The deposit build-up can clog the injector nozzles, which can alter the spray pattern, furthermore, deposits on the tips of injectors are a source of particulate matter (PM) discharged from the engine. In order to prevent air pollution, it is essential to develop a technology to reduce PM. The spread of fuel adhering to the tip of a fuel injector was simulated using the moving particle semi-implicit method, and a previously developed particle/grid hybrid method was used to study the effects of spray plumes. The simulated distribution of the film qualitatively agreed with the measured distribution of carbon deposits. Fuel film formed on the concave and convex wall surfaces. The fuel film and carbon deposits were unevenly distributed in the air flow direction. Investigation of the behaviors of floating droplets around the tip between fuel injections revealed that the droplets were pulled toward the tip wall due to a reverse air flow generated by the fuel plumes ejected by the injector nozzles. These droplets then merged as a part of the fuel film, which spread toward the injection nozzles due to the air flow directed at the nozzles. Some of the film was sucked into the spray plumes and then re-injected into the air region again. The simulated fuel film behaviors on the tip qualitatively agreed with the measured ones. Furthermore, the simulation showed that optimizing the surface shape of the fuel injector tip, particularly the concave portion, is important for reducing particulate matter.

Superheated metastable water atomization: fine atomized water plumes diagnostics and disperse characteristics; summary of results, applications in power generation and new techniques.

Complex experimental investigation of superheated flow and dispersion characteristics of sprays in atomizing nozzles of various types is made. The comparative analysis of experimental and calculating investigations of thermo physic and hydro- gas-dynamic flow and disperse characteristics was carried out for various types of spray nozzles. It has shown that the main process, which determine peculiarities of superheated metastable water flow and phase transformation in spray nozzles, is quick (explosive) boiling up. And the optimal variant for superheated water atomization and achieving the most fine spray plumes, which contain mainly submicron droplet fraction, at initial temperature 240°C (and higher) is atomization by means of contracting-expanding nozzles. In such nozzles the explosive boiling is accomplished by quick transformation of foamed liquid into vapor-droplet flow. Diagnostic peculiarities are considered for these optically dense spray plumes; the auxiliary measurement methods were worked out for estimation superheated water high atomization level. The experimental and calculating data dimensionless treatment was made for achieving extremely fine (mainly submicron) superheated water spray. The dimensionless parameter, which determines necessary water (or some other liquids, for example – fuels) superheating level was derived. The possible technical applications of superheated water sprays are described, and up-to-date state of corresponding projects is given.

A genetic algorithm-based approach for numerical solution of droplet status after Coulomb fission using the energy

As a droplet moves, due to evaporation at the surface, the droplet size is gradually reduced. Due to decreasing the size of the droplets moving in the spray core, the surface charges become closer and the repulsive force between the charges increases. When the Coulombic force overcomes the surface tension force (Rayleigh instability) the droplet breaks into smaller droplets (Coulomb fission). The present study predicts droplet Coulomb fission and droplets trajectories of steady spray plume in a monodisperse Electrohydrodynamics (EHD) spray within a Lagrangian framework. Droplet fission is simulated based on the principle of minimum free energy using the Genetic Algorithm (GA) and droplet trajectories are predicted using the Lagrangian single-droplet dynamic tracking method. The numerical model is validated by comparing the model predictions with the experimental and previous modeling results. In the current method, an optimization method for minimizing the energy in the minimum energy principle is utilized to avoid any simplifying assumptions, such as number of sibling droplets and charge distribution on their surfaces which may affect the physics of the problem. According to the process of the present solutions and results, it is clearly seen that the developed method has sufficient accuracy and precision.

Determination of Spray Pattern and Plume Geometry of Combined Budesonide and Formoterol Fumarate pressurized Metered Dose Inhalation Aerosol

Budesonide and formoterol fumarate pressurized metered-dose inhaler (pMDI) is combined aerosol dosage form. The label claim of this combined dosage form is 100 mcg of Budesonide and 6 mcg of Formoterol Fumarate per actuation. It is prescribed for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Formoterol fumarate is an anti-asthmatic drug (Bronchodilator), and Budesonide is Anti Inflammatory drug (Glucocortico steroid).The objective of plume geometry and spray pattern study is to monitor the consistency and quality of a device when actuated. The plume and pattern study aims to develop a formulation with robust device which can deliver an accurate amount of drug directly to the lungs of a patient. The chemistry manufacturing and controls (CMC) guideline outlined the basic data required for spray pattern and plume geometry measurement for different pMDI devices. In 2013, draft guidance on bioavailability and bioequivalence (BABE) of pMDI published, which provides details on plume geometry and spray pattern, image collection and evaluation.In the present study, the spray patterns were collected at 2 distances 3 and 6 cm from the actuator device's exit. The spray pattern Ovality results at 3 cm show 2.52% variation and at 6 cm results show 4.31% variation. Method precision, ruggedness and robustness study for Spray pattern also performed at 6 cm distance from actuator orifice. The plume geometry was collected at 6 cm distance from the exit of an actuator device. Plume geometry results show that Plume height is found in the range 16.20 cm to 18.98 cm, Plume angle is found from 17.7–24.9°, and Plume width is found between 3.68 to 4.57 cm.

Hole-to-hole variations in coupled flow and spray simulation of a double-layer multi-holes diesel nozzle

In diesel engines, double-layer multi-holes nozzles contribute significantly in making spray injection uniform in both the circumferential and axial directions; they further ensure that minimal or no interactions are encountered among the spray jets emerging from the nozzle holes and positively affect fuel atomisation and enhance mixing during engine operation. In this study, the variation in internal flow characteristics and spray patterns from the upper and the lower layer nozzle holes were investigated experimentally and computationally. A double-layer 8-hole heavy-duty diesel engine injector nozzle was utilised for the characterisation of hole-to-hole variation on spray formation. The actual nozzle geometry was derived from X-ray scans obtained at the third generation X-ray imaging and biomedical beamline station in SSRF, revealing all geometrical differences between the individual injection holes. The momentum fluxes from each holes were obtained together with spray tip penetration under non-evaporating conditions. These data were used to validate the computational fluid dynamics (CFD) model suitable to describe the relevant flow processes. Initially, an Eulerian-Eulerian two-phase flow model was utilised to predict the internal nozzle flow under cavitating conditions. This model was weakly coupled with a Lagrangian spray model predicted the subsequent atomisation and penetration of all individual spray plumes. The results show that cavitation development within the upper layer holes is more intense than those formed within the lower layer nozzle holes; this is leading to higher injection rates from the lower layer nozzle holes that they also exhibit less cycle-to-cycle variations in the observed spray patterns.

Flash boiling combustion of isomeric butanol and gasoline surrogate blends using constant volume spray chamber and GDI optical engine

Flash boiling spray has been regarded as a promising fuel injection technology. Many investigations have been focused on spray physics and mechanisms of flash boiling spray, but information on flash boiling of alcohols in GDI engines is very limited. In this paper, the spray characteristics, flame propagation, combustion analysis, and PN emissions of butanol isomers under flash boiling spray have been studied. A constant volume chamber with a high-speed camera used to investigate the flash boiling spray of butanol isomers and gasoline surrogate blends. The flash boiling spray was tested at 180 °C and compared to subcooled spray at 25 °C. The tested gasoline surrogates are primary reference fuel (PRF) and toluene primary reference fuel (TPRF). The flash boiling leads to the collapse of the spray six plumes into a single extended spray plume with longer spray penetration compared to subcooled injection. The spray study then extended to study the effects of flash boiling injection on flame development and PN emissions of the GDI optical engine. The results reveal that flash boiling injection leads to lower apparent flame speed and flame area compared to subcooled injection due to the lean-like burn condition, and yellow flame spots are diminished. The peak in-cylinder pressure and apparent heat release rate are reduced with longer ignition delay when the flash boiling injection is applied. The flame lasted longer under flash boiling conditions with improved late combustion phase, which results in higher heat released. The PN emissions reduced with flash boiling spray compared to subcooled conditions.

Coupled in-nozzle flow and spray simulation of Engine Combustion Network Spray-G injector

A coupled Eulerian-Lagrangian approach was employed to Engine Combustion Network (ECN) Spray-G simulations. The Eulerian in-nozzle flow simulation was conducted with a small plenum attached to the nozzles, and the results were fed to the Lagrangian spray simulation. For Eulerian simulation, the homogeneous relaxation model (HRM) coupled with the volume of fluid (VOF) method was used. HRM proved to be good at predicting the phase change phenomena due to vaporization mechanisms, that is, both cavitation and flash boiling. As a one-way coupling, quantities such as rate of injection (ROI), mass injected through each hole, discharge coefficient, spray plume angle and half cone angle predicted from the Eulerian simulations were used as the initial and boundary conditions for the subsequent Lagrangian spray simulations using the blob injection model. Non-flashing (Spray-G1) and flashing (Spray-G2) spray was simulated, and the results were validated quantitatively against the published data in terms of the liquid and vapor penetration lengths, and good agreements were obtained. Furthermore, the simulation predicted the liquid and gas axial velocity and sauter mean diameter for Spray-G1 condition in agreement with the droplet size and particle image velocimetry (PIV) measurements from literature.

Computational Study of a Multiple Fuel Injector Concept under High-Load and High-EGR Conditions

<div class="section abstract"><div class="htmlview paragraph">A new concept utilizing multiple fuel injectors was proven effective at reducing heat transfer losses by directing spray plumes further away from the combustion chamber walls. In this concept, two injectors are mounted close to the rim of the piston bowl and point in opposite directions to generate swirling in-cylinder bulk motion. Moreover, a new flat-bowl piston design was also proposed in combination with the multiple fuel injectors for even larger improvements in thermal efficiency. However, all tests were performed at low-to-medium load conditions with no significant EGR. Modern engine concepts, such as the double compression-expansion engine (DCEE), have demonstrated higher thermal efficiency when operated at high-load conditions with a large amount of EGR for NOx control. Thus, this study aims to assess the effectiveness of the multiple-fuel-injector system under such conditions. In this study, a number of 3-D CFD simulations are performed using the RANS technique in CONVERGE. The computational domain is based on the modified Volvo D13 engine geometry that is used as a combustor unit of the DCEE. The results of this study show that the injection strategies used previously with the multiple-fuel-injector concept perform poorly at high-load conditions due to inadequate mixing. Moreover, the flat-bowl piston design proposed previously does not seem to improve heat transfer losses at these conditions. Thus, several alternative piston bowl designs are investigated, some of which are shown to reduce heat losses and improve mixing. Finally, a number of perspective strategies are recommended to be implemented with the multiple-fuel-injector concept for efficiency maximization.</div></div>

Spatio-temporal identification of plume dynamics by 3D computed tomography using engine combustion network spray G injector and various fuels

Understanding of plume direction and mixture quality in a combustion chamber is crucial to improve engine performance. While a variety of diagnostics using laser and x-ray facilities have been applied to identify plume direction, most applications require sophisticated experimental setup as well as troubleshooting for light attenuation or scattering issues. In this study, we acquire temporally and spatially resolved liquid volume fraction by three-dimensional tomographic reconstruction of ensemble-averaged extinction images to produce unique information on plume movement and growth in the midst of a multi-plume spray. Measurements were carried out in a constant-flow spray vessel coupled with high-speed Mie-scattering, diffused back-illumination extinction, and schlieren imaging. Four different fuels, a single component iso-octane, a multi-component surrogate with di-isobutylene, a multi-component fuel with olefinic molecular structure, and a 70% standardized gasoline 30% ethanol (e30) blend were injected using Engine Combustion Network (ECN) Spray G injector under ECN G2 (50 kPa absolute), G3 (100 kPa absolute), and G3HT (G3 with 393 K ambient temperature) conditions. Planar slices, available from the tomographically reconstructed extinction data, confirmed greater plume-to-plume interaction for the flash-boiling G2 iso-octane condition with an approximately 6° smaller plume direction angle relative to the injector axis, compared to the nozzle drill angle. The olefinic and e30 fuels, which have broader distillation curves, exhibited stronger plume growth and eventual complete spray plume collapse and longer time for evaporation. Using the 3D dataset, we show that factors that increase plume growth also create more interaction between plumes to ultimately reduce the plume direction angle.

A general-purpose spray coating deposition software simulator

In this work the coating thickness from a high kinetic energy spray process is predicted as a function of the gun and object kinematics. The developed simulation package is capable of handling complex parts of arbitrary geometry, in the form of triangulated surfaces. Supported features include object rotation, simultaneous 5 DOF gun movement, uniform and Gaussian radial profile of spray plume intensity, identification of triangles hidden from the plume and adaptive time-stepping methods. Advanced visualization of the results is also provided. The resulting coating thickness for each elementary triangle on the surface of an object is computed from interpolated look-up tables that contain coating parameter information such as the impact angle, stand-off distance and spot surface speed. The accuracy of the simulator is validated by comparing the predicted coating thickness with experimental measurements on equivalent and representative substrates.

Spray characteristics of direct injection injectors with different nozzle configurations under flash-boiling conditions

This investigation utilized four gasoline direct injection (GDI) injectors with different nozzle lengths and step hole diameters to analyze the influences of nozzle structure on the superheated plume and spray collapse under different superheat degrees. The spray behaviors of were recorded by using high-speed shadowgraphs. In addition, the spray concentration distribution, spray development, and spray swelling characteristics under different superheat conditions were analyzed. The experimental results showed that hole length and step hole diameter affected the widths of the spray plumes, which then affected the spray characteristics. Wider spray plumes enhance plume interactions and promote reduced spray penetration. This causes spray to enter the transition regime at a lower degree of superheat. In addition, the transition regime exhibits better spray characteristics than the subcooled and flare flash boiling regimes. Injector with smaller hole length and larger step hole diameter exhibits stronger adaptability while utilizing the remarkable spray characteristics in the transition regime, owing to the greater length of the spray transition regime.

Preliminary study on extinguishing shielded fire with water mist

Fires in commercial and industrial areas, such as large warehouses containing goods on shelves, are inevitably shielded by nearby objects that act as obstacles, making such fires difficult to extinguish. Water mists, as an alternative to the halon fire-extinguishing agent, are capable of bypassing obstacles owing to the small size of the water particles. Therefore, by varying the distance between a plate obstacle and the nozzlefire source, half-scale experiments were performed under different working pressures to determine the critical condition of shielded sand-burner fire extinguishment. The flame temperature and radiant heat flux were measured using thermocouples and a radiometer. The interaction between a water mist spray and a shielded fire was visualized via laser light sheet illumination. The fire-extinguishing capability was analyzed based on the plate obstacle block ratio and the plume–spray thrust ratio. The results indicate that an empirical linear correlation can be adopted to predict the critical plume–spray thrust ratio required for fire extinguishment under different block ratios. In addition, Fire Dynamics Simulator was used to simulate the spray–plume interaction under the shielding conditions employed. The experimental and numerical results show a similar suppression tendency in cases with a low block ratio and fire size. This preliminary study may provide some raw data on shielded fire suppression with a water mist, in addition to serving as a reference for the optimal design of water mist systems.

Flash boiling macroscopic spray characteristics of multi-hole direct injection injectors with different hole arrangement

The spray characteristics of two direct-injection gasoline injectors with different hole arrangement under flash boiling conditions were studied. The spray development and spray characteristics, such as the spray tip penetration, spray angle, rate of collapse, and spray area during the injection process of the two injectors were studied via high-speed shadowgraph techniques. The sprays were divided into three regions based on the rate of collapse at room temperature and atmospheric pressure, that is, the subcooled region, and flash boiling region (transition region and flare flash boiling region). In addition, the spray characteristics of injector N under different superheated degree and ASOI were determined in detail. The experimental results showed that the spray plumes of the injector (N) with small hole spacing easily interacted, causing the earlier collapse of the spray structure. Injector (N) with small hole size had a good effect on atomization, and the effect of flash boiling on spray characteristics was low. The flashing spray characteristics are not only affected by the degree of superheat, but also by the ambient pressure alone. The spray characteristics of injector N and injector W in the transition region are ideal for the GDI engine. This may provide new opportunities for the GDI engine combustion system and injection strategy design.

Characteristics of spray and wall wetting under flash-boiling and non-flashing conditions at varying ambient pressures

Flash-boiling in Direct Injection Spark Ignition (DISI) engines is very common. Flash-boiling atomization is one of the most effective ways to generate fully developed atomization and homogeneous mixtures. However, despite the positive effects of flash-boiling, this phenomenon may also lead to negative effects such as longer spray penetration, piston wall wetting, and increased soot emissions, due to increased interactions among the spray plumes which can result in spray collapse and the aforementioned problems. In this study, high-speed direct photography and Refractive Index Matching (RIM) were utilized to investigate the characteristics of n-hexane sprays and impingement using a constant volume vessel. Under low-pressure conditions, flash-boiling drives the collapsed spray to a quick impingement and small spray area. Through the volume distribution of the liquid fuel film acquired by RIM and the spray outline derived from the morphology of images, it was again confirmed that the spray collapse took place not only at a high degree of superheating, but also under conditions of high ambient pressure without flash-boiling. The spray collapse under high pressure conditions is characterized by a late-phase impingement and large spray-swept area. Varying fuel-film behavior was observed following spray-impingement. Under high-density conditions with spray collapse, the fuel film evaporated slowly after the injection, but the higher ambient pressures reduced the total impingement. At low-density conditions with flash-boiling, the resultant fuel-films evaporated more quickly, and reduced ambient pressures reduced the total fuel-film volumes, although flash-boiling could not completely inhibit spray impingement.

An investigation on the impact of small-scale models in gasoline direct injection sprays (ECN Spray G)

The work presents a numerical investigation of gasoline direct injection and the resulting early development of spray plumes from an eight-hole injector (Engine Combustion Network Spray G). The objective is to evaluate the impact on the droplet size distribution (DSD) statistics from the assumed model physics, particularly for the small scales. Two modelling approaches are compared: Eulerian–Lagrangian spray atomisation with adaptive mesh refinement and a stochastic fields transported probability density function method. The two models simulate the small scales and sub-grid droplet physics with different approaches, but based on the same concept of transport of liquid surface density. Both approaches predict similar liquid distributions in the near-field comparable to experimental measurements. The spray break-up patterns are very similar and both models reproduce quasi-log-normal droplet distributions, with same overall Sauter mean diameters. The Eulerian–Lagrangian spray atomisation with probability density function approach shows different break-up behaviour between droplets originating from the dilute region and those originating from the dense core region. The transition from Eulerian to Lagrangian can be observed in the Eulerian–Lagrangian spray atomisation with adaptive mesh refinement predicted distribution with an abrupt change in the DSD. Both methods are able to produce similar DSD below filter width/grid size resolution.

The Addition of Polar Organic Solvent Vapors During the Analysis of Proteins by DESI-MS.

Exposure of electrospray droplets to organic vapors was shown to dramatically reduce alkali-metal adduction on protein ions and shift protein charge states. Since DESI-MS is affected by similar adduct species as ESI-MS and shares similar ionization mechanisms, polar organic vapor additives should likewise also improve the DESI-MS analysis of proteins. Here the DESI spray was exposed to a variety of polar organic vapor additives. Head space vapors of polar organic solvents were entrained in nitrogen gas and delivered to the atmosphere inside a semi-enclosed plastic enclosure surrounding the spray plume. The vapors of acetone, acetonitrile, ethyl acetate, methanol, and water were investigated. Vapor dependent effects were observed with respect to changes in protein charge state distributions and signal intensities. With ethyl acetate vapor addition, the signal intensities of all proteins investigated were significantly increased, including proteins larger than 25 kDa such as carbonic anhydrase II and bovine serum albumin.