Maunu Kuosa - Academia.edu (original) (raw)

Papers by Maunu Kuosa

The goal of this paper is to present results of analysing the functionality of a power transmissi... more The goal of this paper is to present results of analysing the functionality of a power transmission system. In the present case study the power is input from a motor to a hydrodynamic torque converter. It actuates a machinery consisting of a variator, a compound gear train, a planetary gear train, clutch alternatives and a load machine. The purpose of the converter is to obtain high startup torque. The aim of the variator is to obtain stepless speed transmission. Various clutch alternatives are considered and possibilities of an optimal synthesis to obtain optimal transmission of power and speed. Electro-rheological fluid power and clutch components are studied for obtaining optimal torque transmission. The design variables of the ER-clutch are number of activated plates, disk spacing and the shear stress of the fluid. The torque capacity of the ER-clutch depends on the ER-shear stress of the fluid which depends on the electric field and temperature. Dry and wet friction clutches ar...

The deceleration dynamics and tnbology of a high speed rotor system are studied. The rotor is ver... more The deceleration dynamics and tnbology of a high speed rotor system are studied. The rotor is vertical and normally supported by magnetic bearings. In emergencies it is stopped upon retainer bearings. Feasible tribological material pairs are tested by simulation for selecting the best ones for field tests. Dynamic behaviour of the rotor bearing system is studied using analytical modelling and simulation solution and also using a multibody 3D dynamics program. The selected specimens are experimentally tested and the wear damage is characterized with high performance analytical Instruments. These observations are used to formulate physical models for explaining the observations and to develop better simulations to explain the surface wear damage at high speeds.

Some liquids can be kept in a supercooled or supersaturated metastable state for substantially lo... more Some liquids can be kept in a supercooled or supersaturated metastable state for substantially long periods. Such liquids can be applied as long-term heat storage where the latent heat can be released when needed. As xylitol possesses a relatively high value of latent heat and as it can be easily supercooled, it has promising properties for this application. However, the speed of the crystallization of xylitol is low, leading to a low release rate of latent heat.

This paper presents a preliminary evaluation of the affecting factors when converting an exsting ... more This paper presents a preliminary evaluation of the affecting factors when converting an exsting gas-fired Stirling engine into using biomass fuel. The engine is in combined heat and power generation. To determine the performace of the Stirling engine, a commercial Stirling analysis tool is applied together with models that have been developed for the heat transfer in the heater, cooler, and regenerator of the engine. The simulated performance is presented for the studied engine in gas use. The performance of the heater is preliminary evaluated for using biomass fuels instead of natural gas. In the evaluation, some selected geometry and calculation methods are applied. The results suggest that the power level of the heater cannot be maintained. As a result, new and more efficient heater surface geometries must be developed. In the development process, the use of a separate test heat exchanger for the heat transfer is not recommented. Instead, the new heater goemetry must be installe...

The deceleration dynamics and tribology of a high speed rotor system are studied. The rotor is ve... more The deceleration dynamics and tribology of a high speed rotor system are studied. The rotor is vertical and in normal operation it is supported by magnetic bearings. In emergency braking cituations it should be stopped fast with minimal radial and axial damage to a ring sliding bearing. A list of feasible tribological material pairs are tested by simulation for selecting the best ones for field tests. Wear rates and wear volumes under various assumptions are estimated and also power consumptions and temperature rises. Dynamic behaviour of the rotor bearing system is studied using analytical modelling and simulation solution and also using a multibody 3D dynamics program Working Model. The simulations are used to design the experimental testing. There is a need for more quantitive material models and interdisciplinary design when designing tribological advanced high speed products. Present tools give reasonable results but integrated design tools are needed.

New technologies are applied to utilize biofuels in district heating. These applications are ofte... more New technologies are applied to utilize biofuels in district heating. These applications are often rather small in unit size and will be distributed to urban areas near residential buildings. The utilization of biofuels sets restrictions and demands for the applied technology. Here the governing factors are the environmental effects, maintainability and fuel logistics of the plant. Combined heat and power (CHP) production is a commonly used means to improve the energy economy of district heating. In combined production it is necessary to bring the power plant as near the consumer as possible. With respect to electricity production it is also advantageous if the energy is produced and consumed in the same area. As a preliminary work for the research, an evaluation was performed for costeffective utilization of biofuels in energy production. The increase in the use of bioenergy was found to be most efficient in distributed solutions where the transport paths remain relatively short. T...

Energy and Buildings, 2014

Plate heat exchangers (PHE) have consolidated their position as key components of modern heating ... more Plate heat exchangers (PHE) have consolidated their position as key components of modern heating processes. They are widely accepted as the most suitable design for heat transfer applications in various processes, including the field of energy-efficient district heating (DH). This study refers to new DH coupling and control applied to a consumer substation. The concept introduces a new mass flow control model optimising the primary and secondary water streams to achieve remarkably higher temperature cooling in a new low temperature programme with diminished pressure losses. Here the operation of the ring network and the mass flow control in the substation are studied theoretically. A calculation procedure and transient models were constructed for the DH network, building structures, and heating heat exchangers. The PHE and its operation in the substation were studied by means of a corrugated plate model with five vertical parts and 10 elements. Variations in the flow rates, pressure losses, and overall heat transfer coefficients were received for the selected days. As a result almost equal heat capacity flows were found between the hot and cold sides of the PHE with maximum temperature cooling. The key performance factors of the heat exchanger, NTU and effectiveness, were monitored and the mean values obtained were 9.2 and 0.9, respectively. (M. Kuosa), martin.aalto@aalto.fi (M. Aalto), m.assad@ack.edu.kw (M. El Haj Assad), tapio.makila@energianhallinta.com (T. Mäkilä), markku.lampinen@aalto.fi (M. Lampinen), risto.lahdelma@aalto.fi (R. Lahdelma). be proprietary in nature although many new design approaches have been published in recent years. According to Gut and Pinto [2], there are no rigorous design methods for PHEs in the open literature, as there are for shell-and-tube exchangers. The design methods of PHEs are mostly owned by equipment manufacturers and are suited only for the exchangers that are marketed [3]. An exception is provided by Shah and Focke [4]

Applied Thermal Engineering, 2015

The Open Fuels & Energy Science Journal, 2009

In the present study, a direct-mode glucose fuel cell with a neutral-state and near-neutral-state... more In the present study, a direct-mode glucose fuel cell with a neutral-state and near-neutral-state aqueous electrolytes is studied. The near-neutral state electrolytes are important for two reasons. Firstly, the pH of the electrolytes would be near the pH of liquid in living cells. Secondly, the neutral electrolyte would enable good corrosion resistance of catalyst materials. Three different catalyst materials, i.e. Pt-Pd, Raney-Ni and Ni-porphyrin complex, are tested in an anode half-cell configuration with one neutral-state (battery water) and with two near-neutral-state aqueous electrolytes, i.e. modified Krebs-Ringer (K-R) and phosphate, both buffered to a pH value of 7.4. Pt-Pd catalyst in the aqueous K-R electrolyte maintains the negative voltage of the anode half cell with higher current densities that the nickel catalysts do. To estimate the operation of the direct-mode glucose fuel cell, the K-R electrolyte from the anode half-cell tests is tested also in the cathode half-cell with combined catalyst of cobalt porphyrin complex and of spinel. The open circuit voltages and polarisation curves are measured. Also, preliminary results and oxidation degrees of glucose in the tests are shown. Based on our half cell measurements, there are high development demands for the electro-catalysts, which could work efficiently in the near-neutral-state electrolytes.

The Open Fuel Cells Journal, 2008

This paper is a study about a direct mode fuel cell with a near-neutral-state and alkaline electr... more This paper is a study about a direct mode fuel cell with a near-neutral-state and alkaline electrolytes. The aim of study was to develop a fuel cell, which operates directly by mixing the fuel with the electrolyte. This arrangement helps to avoid inserting membranes and additional bacterial cultures in fuel cell. The target is also to create a fuel cell with a capacity of few mWcm -2 with the starch as a fuel. Also, glucose and sorbitol have been tested as fuel for the fuel cell.

This paper discusses the conditions to develop a micro-cogeneration plant based on biomassfuelled... more This paper discusses the conditions to develop a micro-cogeneration plant based on biomassfuelled rotary steam engine (RSE). The use of RSE in micro-cogeneration is justifiable due to relatively high electrical efficiency, capability of applying versatile thermal sources and low operational temperatures and pressures. At steam temperatures 200…300ºC, the electrical efficiency of 20 % may be obtained with the electrical power varying between 1…20 kW e . The other advantages of an RSE are that it is lubricant free and the noise level is low. In residential applications, an RSE may be considered a new and compact alternative for Stirling Engines and internal combustion engines, when integrated into a hydronic heating system and electrical grid. Another promising adaptation is desalination. A solar-powered RSE micro-cogeneration system would provide an inexpensive option to supply fresh water and electricity for the rural areas in developing countries that have access to sea water. A 10 kW e RSE plant combined with a oncethrough multi-stage flash (MSF) distillation plant is estimated to have potential of producing pure water from 150 to 600 kg/h.

The Open Fuel Cells Journal, 2009

This study deals with the R&D regarding the direct glucose fuel cell with a capacity of increasin... more This study deals with the R&D regarding the direct glucose fuel cell with a capacity of increasing the power density with glucose as a fuel. The direct-mode fuel cell in which the fuel and the alkaline electrolyte are mixed with each other is tested at room temperature. The direct-mode fuel cell is exposed to an externally generated electromagnetic field with 4 GHz sine signals between electrodes to cause both the splitting of the fuel molecule and the electrochemical oxidation. As a result from the use of the higher frequency signals, a maximum current density of 15 mAcm -2 has been achieved with the total voltage of 0.5 V.

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations, 1998

ABSTRACT The aim of this study was to make a computer program that simulates a standard refrigera... more ABSTRACT The aim of this study was to make a computer program that simulates a standard refrigeration process, and a process provided with a bubble intercooler. A further object of the study was to establish the suitability of a turbocompressor for small refrigeration plants. Firstly the fundamentals of refrigeration machines and industrial refrigeration systems are discussed. An iteration procedure of steady state refrigeration process calculation is introduced. Fluid properties are calculated with the program units created for the modelling of an ORC power plant. Specific input files were made for 6 process fluids R134a, R123, isopentane, isobutane, toluene and ammonia. The compressor program is linked to the refrigeration process simulation program in order to model single stage and two stage radial compressors. The Turbo Pascal program made for microcomputers is modular, which makes it possible to develop and test the program unit by unit. The maximum deviations of fluid properties from those in tables was found to be less than 1 per cent. To simulate tailor-made refrigeration plants, a simple model is required. On nominal loads the program estimates an optimum intermediate pressure for the bubble process and optimum rotational speed for the radial compressor(s). The lowering of the rotational speed by an inverter gives high COP-values on partial loads of the plant. Based on the example calculation, a two stage turbocompressor calculated with isopentane as the working fluid, a cooling capacity of 1200 W seems to be feasible.

Journal of Thermal Science, 2004

This work deals with the cooling of high-speed electric machines, such as motors and generators, ... more This work deals with the cooling of high-speed electric machines, such as motors and generators, through an air gap. It consists of numerical and experimental modeling of gas flow and heat transfer in an annular channel. Velocity and temperature profiles are modeled in the air gap of a high-speed test machine. Friction and heat transfer coefficients are presented in a large velocity range. The goals are reached acceptably using numerical and experimental research. The velocity field by the numerical method does not match in every respect the estimated flow mode. The absence of secondary Taylor vortices is evident when using time averaged numerical simulation.

ABSTRACT A rotary steam engine (RSE) is a simple, small, quiet and lubricant-free option for micr... more ABSTRACT A rotary steam engine (RSE) is a simple, small, quiet and lubricant-free option for micro-cogeneration. It is capable of exploiting versatile thermal sources and steam temperatures of 150–180 °C, which allow operational pressures less than 10 bar for electrical power ranges of 1–20 kWe. An RSE can be easily integrated in commercially available biomass-fired household boilers. In this paper, we characterize the boiler-integrated RSE micro-cogeneration system and specify a two-control-volume thermodynamic model to conduct performance analyses in residential applications. Our computational analysis suggests that an RSE integrated with a 17 kWth pellet-fueled boiler can obtain an electrical output of 1.925 kWe, in the design temperature of 150 °C, the electrical efficiency being 9% (based on the lower heating value of the fuel, LHV) and the thermal efficiency 77% (LHV). In a single-family house in Finland, the above system would operate up to 1274 h/y, meeting 31% of the house's electrical demand. The amount of electricity delivered into the grid is 989 kW h/y. An economic analysis suggests that incremental costs not exceeding € 1500 are justifiable at payback periods less than five years, when compared to standard boilers.

Applied Thermal Engineering, 2014

Energy-efficiency of a novel DH ring network and mass flow control is examined. Optimal supply an... more Energy-efficiency of a novel DH ring network and mass flow control is examined. Optimal supply and return water temperatures of a case study are found. Heat losses, pumping, and surplus energy from the heat recovery are included. Average energy losses are reduced compared to the traditional network design.

Materials Science Forum, 2010

... Ltd, Minkkikatu 1-3, FI-04430 Järvenpää, Finland a jukka-pekka.spets@tkk.fi, b maunu.kuosa@ t... more ... Ltd, Minkkikatu 1-3, FI-04430 Järvenpää, Finland a jukka-pekka.spets@tkk.fi, b maunu.kuosa@ tkk.fi, c tom.granstrom@tkk.fi, d yohannes@kth.se, e jyri.rantanen@hydrocell.fi, f markku.lampinen@tkk.fi, g kari.saari@tkk.fi ... 9] Yao SJ, Appleby AJ, Geisel A., Cash HR and Wolfson ...

Journal of Power Sources, 2010

In this study a direct-mode fuel cell in which the fuel and electrolyte are mixed with each other... more In this study a direct-mode fuel cell in which the fuel and electrolyte are mixed with each other is tested. An alkaline electrolyte is used. The direct-mode fuel cell is exposed to an externally generated electromagnetic field between electrodes to cause both the splitting of the fuel molecule into smaller units (i.e. electrochemical reforming) and an increase in the activity of catalyst materials on the fuel before electrochemical oxidation. The target is to create a fuel cell with a capacity range of a few mW cm −2 with glucose as a fuel. In the selected fuel cell type with glucose as the fuel, a maximum current density of 13 mA cm −2 was obtained. On the basis of the tests it seems to be possible to use the glucose-fuelled cell in small-scale applications, e.g. in small electronic devices.

Experimental Thermal and Fluid Science, 2010