Papers by Örjan Johansson
Mekmassainitiativet för energieffektivitet, e2mp-i
Projektet har drivits som ett program for finansiering av forskning som ska utveckla ochdemonstre... more Projektet har drivits som ett program for finansiering av forskning som ska utveckla ochdemonstrera tekniker som reducerar elenergiforbrukningen med 50% vid tillverkning avTMP och CTMP med bibehall ...
The project aims to use ultrasound controlled cavitation to achieve a more energy efficient leach... more The project aims to use ultrasound controlled cavitation to achieve a more energy efficient leaching process. Locally, collapsing cavitation bubbles cause an extremely high pressure, shock waves an ...
Sensitivity analysis of transfer function estimation in inverse methods
Acta Acustica United With Acustica, 2005
Sound intensity measurements of transient noise in presence of extraneous noise
Acoustic optimization of a flow through sonicator for fibrillation of cellulose fibers
Chemical Engineering and Processing, Nov 1, 2022
Comparison of Different Concepts of UltrasoundReactors Using Numerical Simulations
Sonochemical reactors are used for process intensification based on efficientenergy transfer due ... more Sonochemical reactors are used for process intensification based on efficientenergy transfer due to ultrasound in order to cause transient cavitation in the medium.Ultrasonic reactors are extensive ...
PLOS ONE, 2020
Ultrasound has many uses, such as in medical imaging, monitoring of crystallization, characteriza... more Ultrasound has many uses, such as in medical imaging, monitoring of crystallization, characterization of emulsions and suspensions, and disruption of cell membranes in the food industry. It can also affect microbial cells by promoting or slowing their growth and increasing the production of some metabolites. However, the exact mechanism explaining the effect of ultrasound has not been identified yet. Most equipment employed to study the effect of ultrasound on microorganisms has been designed for other applications and then only slightly modified. This results in limited control over ultrasound frequency and input power, or pressure distribution in the reactor. The present study aimed to obtain a well-defined reactor by simulating the pressure distribution of a sonobioreactor. Specifically, we optimized a sonotrode to match the bottle frequency and compared it to measured results to verify the accuracy of the simulation. The measured pressure distribution spectrum presented the same overall trend as the simulated spectrum. However, the peaks were much less intense, likely due to non-linear events such as the collapse of cavitation bubbles. To test the application of the sonobioreactor in biological systems, two biotechnologically interesting microorganisms were assessed: an electroactive bacterium, Geobacter sulfurreducens, and a lignocellulose-degrading fungus, Fusarium oxysporum. Sonication resulted in increased malate production by G. sulfurreducens, but no major effect on growth. In comparison, morphology and growth of F. oxysporum were more sensitive to ultrasound intensity. Despite considerable morphological changes at 4 W input power, the growth rate was not adversely affected; however, at 12 W, growth was nearly halted. The above findings indicate that the novel sonobioreactor provides an effective tool for studying the impact of ultrasound on microorganisms.
Acoustic cavitation in fluids using high powered ultrasound has been of great interest in industr... more Acoustic cavitation in fluids using high powered ultrasound has been of great interest in industries and bio-medical engineering. The need for high-intensity focused ultrasound (sound with frequencies between 20kHz to 10 MHz) and modeling of such systems has drawn great attention in engineering. Ultrasound excitation has found recent application in terms of replacing the existing dynamic mechanical systems that use high energy with low levels of efficiency. The proposed thesis work focuses on an application of acoustic cavitation and on adaptive control of resonance amplification to be used in the paper pulp industry. The primary objective is to keep a system of coupled and tuned resonances stable, and by that obtain high cavitation intensity in a water filled beaker. The secondary aspect is to numerically model and experimentally evaluate a prototype beaker, where the adaptive control scheme is implemented to attain high and stable cavitation intensity. The characteristic control p...
Energy Efficient Fibrillation of Cellulose Fibers using an Ultrasound Reactor
The pulp and paper industry is in continuous need for energy-efficient production processes. Ther... more The pulp and paper industry is in continuous need for energy-efficient production processes. Therefore, there is a focus in reducing electrical energy use in the production of paper. The most energy demanding processes are related to fibrillation, which in some cases use up to 80% of required electrical power, with a net efficiency of 1%. The presented work focus on ultrasound controlled cavitation in concentrating the processing energy to provide an energy efficient development of cellulose fibers. The objectives are to develop a scalable cavitation reactor to obtain energy-efficient fibrillation of cellulose fibers aiming at reducing the energy use by 50%. Our goal is to develop a methodology based on multiphysic simulation for the design of an alternative refiner based on ultrasound cavitation. The reactor concept is of a flow through type where cavitation bubbles are initiated in the fiber suspension by the pressure release when the pulp flow through a venturi nozzle. The induced cavitation bubbles are collapsed by high intensity ultrasound at resonant frequencies. The collapsing bubbles and their associated shock waves modify the fiber wall properties which enables fibrillation. Energy efficient fibrillation of cellulose fibers is therefore possible to achieve through an optimized combination of hydrodynamic and ultrasonic controlled cavitation. Initial results shows a positive effect on fiber quality. However, further optimization of process parameters like temperature and static pressure is required
Proceedings of the ICA congress, 2019
This study investigate the impact of high-intensity ultrasound treatment on the mechanical proper... more This study investigate the impact of high-intensity ultrasound treatment on the mechanical properties of pulp fibers. The pulp fiber samples are sonicated in an acoustically optimized beaker where high-intensity ultrasound is generated using a tuned sonotrode device. The idea is to create a controlled resonance to efficiently enhance the sound pressure in the beaker. Input power was 90 W. The objective is to define the difference between freely suspended fibers in a beaker compared to keeping fibers in a fixed position. The hypothesis is that fiber treatment at a specific input power will be more efficient in the case when fibers are kept in a high pressure zone. Since the fiber wall is a layered structure, it is likely to delaminate internally which will affect the mechanical properties of the fiber. The effect on fiber properties is verified by measuring the ultrasound attenuation spectra for the treated fibers. The attenuation measurements are based on measurements of a low-intensity ultrasound pulse-echo technique. On a macroscopic scale, changes in the attenuation spectra relates to a change in mechanical properties of the fiber wall, since the suspended fibers more or less retain their diameter and length distributions.
Product sound usually consists of a mix of several sources. Models for prediction of sound qualit... more Product sound usually consists of a mix of several sources. Models for prediction of sound quality based on combinations of psychoacoustic metrics like loudness, sharpness and roughness have limita ...
Fluids, 2020
A new model for turbulent fibre suspension flow is proposed by introducing a model for the fibre ... more A new model for turbulent fibre suspension flow is proposed by introducing a model for the fibre orientation distribution function (ODF). The coupling between suspended fibres and the fluid momentum is then introduced through the second and fourth order fibre orientation tensors, respectively. From the modelled ODF, a method to construct explicit expressions for the components of the orientation tensors as functions of the flow field is derived. The implementation of the method provides a fibre model that includes the anisotropic detail of the stresses introduced due to presence of the fibres, while being significantly cheaper than solving the transport of the ODF and computing the orientation tensors from numerical integration in each iteration. The model was validated and trimmed using experimental data from flow over a backwards facing step. The model was then further validated with experimental data from a turbulent fibre suspension channel flow. Simulations were also carried ou...
Ultrasonics Sonochemistry, 2021
The primary purpose of this study is to investigate the effects of hydrodynamic and acoustic cavi... more The primary purpose of this study is to investigate the effects of hydrodynamic and acoustic cavitation (HAC) on the leaching efficiency of tungsten. The aim is to reduce energy use and to improve the recovery rate. The goal is also to carry out a leaching process at a much lower temperature than in an autoclave process that is currently used in the industry. Energy-efficient initiation and collapse of cavitation bubbles require optimization of (i) vibro-acoustic response of the reactor structure, (ii) multiple excitation frequencies adapted to the optimized reactor geometry, and (iii) hydrodynamic cavitation with respect to orifice geometry and flow conditions. The objective is to modify and apply a previously in house developed high power cavitation reactor in order to recover tungsten by leaching of the dissolution of scheelite in sodium hydroxide. In this process, various experimental conditions like dual-frequency excitation, different orifice geometry have been investigated. The numerically optimized reactor concept was excited by two frequencies 23 kHz and 39-43 kHz in various flow conditions. The effects of leaching time, leaching temperature, ultrasonic power and geometry of orifice plates have been studied. The leaching temperature was varied from 40 • C to 80 • C. The concentration of leaching reagent sodium hydroxide (NaOH) was 10 mol/L.The results were compared to conventional chemical leaching. Energy supplement with acoustic cavitation of 130 kWh/kg concentrate resulted in a leaching recovery of tungsten (WO 3) of 71.5%, compared to 36.7% obtained in absence of ultrasound. The results confirm that the method developed is energy efficient and gives a recovery rate potentially better than current autoclave technology.
Proceedings of the ICA congress, 2019
Energy-efficient process intensification is a key aspect for a sustainable industrial production.... more Energy-efficient process intensification is a key aspect for a sustainable industrial production. To improve energy conversion efficiency high intensity cavitation is a promising method, especially in cases where the material to be treated is valuable and on the micro meter scale. Transient collapsing cavitation bubbles gives powerful effects on objects immersed in fluids, like cellulose fibers, mineral particles, enzymes, etc. The cavitation process needs optimization and control, since optimal conditions is a multivariate challenge. This study focuses on different design principles to achieve high intensity cavitation in a specific volume in a continuous flow. The investigation explores some potential design principles to obtain energy efficient process intensification. The objective is to tune several different resonance phenomena to create a powerful excitation of a flowing suspension (two-phase flow and cavitation bubbles). The reactor is excited by sonotrodes, connected to two coupled resonant tube structures, at the critical frequency. Finally cavitation bubbles are initiated by a flow through a venturi nozzle. The acoustically optimised reactor geometry is modelled in Comsol Multiphysics®, and excited by dedicated ultrasound signals at three different frequencies. The effect of the high intensity cavitation is experimentally evaluated by calorimetric method, foil tests and degree of fibrillation on cellulose fibers.
International Journal of Industrial Ergonomics, 2001
One of the problems associated with listening to binaurally recorded sound events is localization... more One of the problems associated with listening to binaurally recorded sound events is localization confusions. The main objective of this investigation was to find out whether a short training session prior to listening to binaural recordings through headphones would facilitate correct spatial perception of the sound field. Focus was on the localization of the sound stimuli in median plane. Sound signals were recorded with an artificial head in three different conditions namely, anechoic, highly reverberant and moderately reverberant. Fourteen subjects participated in the listening tests. All subjects were required to localize all virtual sound stimuli under two different conditions. The first condition had a short training session binaurally recorded in the same environments as preceeding sound stimuli, and only sound stimuli recorded in the same environment were presented. The second condition did not have a training session, and sound stimuli recorded in different environments were presented. Results showed that a short training session prior to listening to binaurally recorded sounds through headphones was useful as it facilitated localization performance. The biggest effect was in reduced amount of sounds perceived inside the head. It was most pronounced for sound stimuli recorded in anechoic environment.
Acta Acustica united with Acustica, 2009
Specifications of product sound qualities may contain both perceptual and acoustical descriptions... more Specifications of product sound qualities may contain both perceptual and acoustical descriptions. The perceptual descriptions are most helpful when they contain adequate detail and utilises understandable wording. To facilitate the product design process the descriptions should also be interpretable as acoustical quantities. The objectives of the study reported upon here were to investigate how musicians use verbal descriptions of sound and to interpret these descriptions in terms of commonly used acoustical quantities. Musicians' use of verbal descriptions of saxophone sound was investigated through interviews. The most frequently used words were evaluated through listening tests. The subjects were asked to judge how well the words described the timbre of test sounds. To find the most significant perceptual dimensions for the test sounds Principal Component Analysis was used. Four significant dimensions were found and described by 9 words. To interpret the perceptual dimensions in terms of physically measurable indices, models for how acoustical quantities relate to the perceptual dimensions were developed. Dimension 1 was described by full-toned/warm/soft. The psycho-acoustical quantity sharpness correlated negatively with this dimension. Dimension 2 was described by the term [o]-like. Sharpness and specific roughness (9-11 Bark) correlated negatively with this dimension. Dimension 3 was described by sharp/keen/rough. Sharpness and roughness correlated with this dimension. Dimension 4 was described by the term [e]-like. No model for prediction of this dimension was found. To validate the models the effect of a changed design of the tone holes of a saxophone was predicted with the model and validated with new listening tests.
Design of a high-intensity ultrasound reactor
Design, and optimization of ultrasonic reactors are important objectives in sonochemical processi... more Design, and optimization of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research areas all faces the problem of scaling up from laboratory results to industrial purposes. A traditional ultrasonic reactor usually has several issues, such as low effectiveness as well as complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study addresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound. Some important factors like pressure, material, flow and geometry are considered in the design. Numerical optimization as well as experimental investigations are performed to reach an optimized, energy-efficient and controlled ultrasound cavitation reactor. Results from numerical modeling are used for acoustic optimization of the reactor, which is driven with th...
Analysis of excitation signal characteristics associated with energy-efficient acoustic cavitation
2021 IEEE International Ultrasonics Symposium (IUS)
Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17), Aug 1, 2017
In order to lower the energy consumption of the fibrillation stage for the pulp and paper industr... more In order to lower the energy consumption of the fibrillation stage for the pulp and paper industry, a new technology need to be innovated and developed. The current research work deals with a new innovative concept based on creating cavitation in the pulp flow. A venturi nozzle is designed and optimized, where hydrodynamic cavitation is achieved by the so called Venturi effect. This paper focuses on the development of an automatic method for venturi shape optimization. The process of cavitation is hard to control and can cause high mechanical wear, therefore an optimization study of the venturi shape is performed with two main objectives. Firstly, to achieve cavitation that is sustained for as long as possible downstream and secondly to avoid cavitation at the walls. The developed method is a type of two-level optimization based on neural networks and evolutionary optimization. A number of simulations are executed and the optimization is then performed on a solver approximation instead of the real solver, which considerably reduces computation time. The obtained results show the optimal venturi configuration and the relative importance of each shape parameter. The optimal configuration is a clear improvement of the baseline configuration and an improvement also compared to all of the tested samples, thereby validating the optimization method.
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Papers by Örjan Johansson