Partial Load Modes Research Articles

A comparative investigation of the operating performance and emission characteristics of various diesel engines driving the firefighting pump

The investigation of engines with different performances driving the same load-consuming device is necessary for practical applications. In this paper, three diesel engines with varying capacities for driving the same firefighting pump for high-rise residential buildings were studied and compared for their performance, combustion parameters, and emissions by the simulation method. The AVL BOOST software is utilized to establish theoretical combustion models for these engines. The operating balance point of each engine is determined, and the appropriate transmission ratio of the drive train system is proposed to be applied. The results show that the working partial load modes of Model 1 at 91 % engine load and 2970 rpm, Model 2 at 74 % engine load and 2960 rpm, and Model 3 at 57 % engine load and 2490 rpm. The engine works in its higher load mode, producing higher brake specific fuel consumption (BSFC), higher NOx and CO emissions, lower soot formation, and vice versa. The engine operates at its lower load, resulting in decreased BSFC, less NOx and CO emissions, and more soot generation. The results suggest that Model 2 in the present work is the option that can balance the factors of engine power, initial investment cost, fuel consumption economics, and emissions. The findings obtained from this work are the scientific foundations to support the design of the firefighting pump systems when considering comprehensive factors of technical technology, investment cost, and environmental consideration.

To the question of the description of the internal combustion engine in the mathematical model of the lifting system of the hovercraft (on the example of the ZMZ-51432.10 CRS engine)

Introduction. It is known that about one third of the total capacity of the power plant of the hovercraft (SVP) is spent on the creation of an air cushion that ensures the rise of the main hull of the vessel. At the same time, in SVP, the source of mechanical energy, as a rule, is a diesel internal combustion engine (ICE). This article discusses one of the issues related to the creation of a mathematical model of the lifting system of the SVP, using: ICE, hydraulic transmission, axial fans and an air cushion nozzle scheme. Since in the vast majority of cases, the internal combustion engine performs its work in partial load modes, it becomes necessary to effectively control the power of the internal combustion engine in order to achieve its high efficiency in partial load modes.
 AIMS. The purpose of this study is to develop a mathematical description of the operation of the internal combustion engine both in external and partial modes of operation, for use in a mathematical model of the operation of the lifting system of the SVP.
 Methods. In this study, a ZMZ-51432.10 CRS diesel engine is used for the lifting system of the hovercraft.
 Results. Using the data obtained using the DIESEL-RK program for this ICE, in the Microsoft Excel environment, the corresponding trend lines were obtained for them by approximating the points that identify the partial characteristics of the engine with fourth-order polynomials, as well as the dependence of the coefficients of these polynomials on the control parameter of the ICE operation mode .
 Conclusion. The developed mathematical description of engine operation can be integrated with various load models when simulating real systems using internal combustion engines as energy sources. This means that it can also be used in mathematical modeling of the SVP lifting system in the MATLAB Simulink package.The approach proposed in this article makes it possible to build mathematical models of various systems using internal combustion engines, simplifying the study and saving computational time. Also, the results obtained can be of reference value.

Features of low-temperature corrosion protection of cylinder sleeves of ship low-speed engines

The article examines the specifics of solving one of the problems of low-speed marine engines, during which low-temperature corrosion of cylinder liners occurs during operation at minimum and partial load modes. An overview of the cooling systems of ship's main engines was conducted and possible prospects for improving the cooling systems of ship's diesel engines were considered. Attention is paid to the causes and methods of combating low-temperature corrosion of ship's main engines. The methods of regulating the cooling system of marine diesel engines were considered, and it was determined that the modern concept of regulation in the cooling system should include both automatic regulation of operational parameters due to the installation of frequency-regulated cooling system pumps, and regulation of the water-chemical parameters of the cooling system. Methods of regulating the operating parameters of the pumps in the cooling system of the ship's main engine were also considered, which use the principle of frequency regulation of centrifugal pumps to ensure the modes of operation with the highest efficiency. Thus, frequency regulation is an energy-efficient way of regulating centrifugal pumps with variable coolant flows in ship engine cooling systems and one of the ways to maintain an optimal temperature state. The possibility of modernizing the cooling system of cylinders of low-speed engines according to the principle of the LDCL system to reduce the impact and occurrence of low-temperature corrosion was considered

Amount of heat available from a prosumer of a 5th generation district heating and cooling (5GDHC) system: Case study of a data center

The research problem is no method to estimate the specifications of a data center when no design data is available. The aim is to check capacities and temperature levels to supply energy to a 5th generation district heating and cooling (5GDHC) system. The methodology includes studying satellite images and design documents of similar projects. Ventilation chambers, roof-top units (RTUs), dry coolers, and free cooling chillers are recognized on satellite images. We study the layout of the heating, ventilation, and air-conditioning (HVAC) system, technological limitations, and server and cooling loads. The results suggest excluding RTUs, adding adjusting factors to dry coolers, and investment costs for the conversion from air to water cooling. Chillers and fan coil units operate in partial load mode to ensure the reliability level. Waste heat varies, although server power consumption remains constant. The configuration to utilize the waste heat is suggested. It includes a separate free-cooling heat exchanger, which allows turning off the compressors when the outdoor temperature drops. Variable supply and return temperatures compensate for the variation in outdoor temperature. In summer, the return temperature is high enough to supply heat directly to the 5GDHC network. In winter, heat pump boosting is necessary; the preferable outdoor temperatures are 0–10 °C. The implication is that water cooling increases data center feasibility as a prosumer for 5GDHC. The novelty is a method to assess how much energy is possible to recuperate; specific energy consumption/production is justified. The value is the solution to further decarbonize the energy industry and increase energy efficiency is suggested.

Evaluation of the possibility of using artificial neural networks for self-diagnosis of an internal combustion engine with cylinder deactivation

BACKGROUND: Engine and vehicle control systems must have means of objective control in the form of self-diagnosis. This is especially true for new designs and technologies for controlling a gasoline internal combustion engine, such as deactivating cylinders in partial load mode. The paper gives an assessment of the possibility of self-diagnosis of cylinder shutdown in an automobile crank-guide engine without connecting rods using artificial neural networks.
 AIMS: Determination of the possibility of creating an artificial neural network that recognizes which cylinders are currently in operation and which are disabled, based on the nature of the change in the signals from the sensors installed on the engine mounts and independent on the crankshaft speed.
 METHODS: The study considered artificial neural networks of the LSTM and BiLSTM topology. An engine simulation model made in Simulink was used in order to obtain sensor signals. The conducted numerical experiments made it possible to obtain data, which simulates the sensors readings, and to train artificial neural networks to determine the order numbers and quantity of deactivated cylinders. Numerical experiments were carried out on the basis of full-factorial design. Various designs of experiments were used for training and testing of artificial neural networks, which made it possible to test the network on data that differed from the training data significantly. Testing took place on a large number of random sequences of cylinder deactivation modes.
 RESULTS: The obtained results show a high degree of recognition of the order numbers of deactivated cylinders just after several tens of degrees of the crankshaft rotation while switching to the corresponding mode. For the LSTM network, mode detection accuracy was above 99% in both the data sequence transfer mode and the data streaming mode. Accuracy of the BiLSTM topology was over 99.9% in the data sequence transfer mode, but significantly decreased in the data streaming mode.
 CONCLUSIONS: The use of considered types of networks in engine and car control systems is promising.

DEVELOPMENT OF METHODS FOR EVALUATION OF TECHNICAL CONDITION OF ENGINES ACCORDING TO THE RESULTS OF INDICATION OF WORKING PROCESS ON MODES DIFFERENT FROM NOMINAL

Technical condition assessment of marine internal combustion engines by the parameters and nature of the workflow is a common practice in their operation. Taking and analysis of indicator diagrams is a mandatory procedure provided by the rules of technical operation for the main range of large and medium-sized marine engines. There is a whole arsenal of indication means for such evaluation: from classical mechanical systems to electronic means of periodic or continuous action. The rapid development of electronic control systems and changes in approaches to logistics operations in maritime transport have imposed a number of limitations, somewhat narrowing the possibilities of using these methods. Most of the vessels that form the basis of the world merchant fleet were built 10...15 years ago. Information about the results of the indication of the engines of such vessels during bench tests is presented in the form of raster images. This complicates the process of using them as the reference needed to compare them with the actual diagrams obtained in operation by means of electronic control systems, which have replaced mechanical indicators over the past few years. In addition, tendencies to reduce the speed of vessels complicate, and often make it impossible to indicate the engines in the specified operating modes. As a result, the efficiency of using indicator diagrams to assess the current technical condition is sharply reduced. In this regard, there is an objective need to compare different methods of obtaining and storing information about the results of indication and in a unified method of presenting this information, convenient for processing and analysis. In addition, there is a need to develop methods for obtaining reference diagrams for nonspecific modes on the basis of processing the results of acceptance and commissioning bench tests of a particular engine to assess its technical condition by the results of indication on the partial load modes. This study is devoted to the comparison of different methods of presenting information and obtaining reference indicator diagrams for non-specific operating modes of engines.

Experimental validation of a dynamic modelling of a Reversible Solid Oxide Cells (rSOCs)

The integration of Hydrogen technologies in different end-uses such as transport, electric microgrids, residential and industrial applications, will increase exponentially soon. Hydrogen as energy carrier allows more favourable energy conversion than other conventional systems and is crucial in worldwide decarbonize end uses. The production of green hydrogen, using RES, is a key area for the evolution of this technology. In this context, SWITCH is a Horizon 2020 European Project that aims to design, build and test an in-situ fully integrated and continuous multisource hydrogen production system, based on solid oxide cell technology. Reversible Solid Oxide Cell (rSOCs) technologies allow to convert renewable energy as hydrogen in the power-to-gas application (P2G) and in reversible mode is able to produce electricity from hydrogen stored, power-to-power application (P2P). rSOCs are really interesting to stabilize the random nature of RES because a combined electrolysis and fuel cell system should be able to switch between the two modes as quickly as possible in order to optimize the integration and the use of RES. However, rSOCs need a complex BoP from the thermal point of view, able to guarantee high efficiency even at partial load mode as well as easy start-up and shutdown procedures. In this work, a Stack Box Module dynamic model was developed in Modelica environment as a dynamic tool for the definition and optimization of BoP requirements. Stack model was validated in SOFC (Solid Oxide Fuel Cell) and SOE (Solid Oxide Electrolyser). The results of the simulation provide verification of the technical/thermodynamic behaviour and flexibility of a stack box of 70 cells. Dynamic modelling allows to evaluate the effect of the reagent inlet temperatures on the operation and hydrogen production/consumption in terms of yield as well as the transients between the different operative modes. Model has been validated by experimental measurements performed in the laboratory. In particular, the kinetics of the reactions governing steam methane reforming (SMR) was considered from data found in the literature, while the ASR (Area Specific Resistance) value was calibrated according to experimental data. The results of the dynamic model show as model can be a useful design and optimization tool for the SOCs technology.

REMOVAL OF TECHNICAL AND ECONOMIC INDICATORS OF THE D-240 ENGINE WHEN USING BIOFUELS BY APPLYING THE DIESEL-RK SOFTWARE COMPLEX

Ukraine is one of the energy-deficient countries because it covers its needs in fuel and energy resources from domestic reserves by only 53% (imports 75% of the required natural gas and 85% of crude oil and petroleum products). Dependence on oil imports is seen by most developed countries as a matter of national and energy security, and the use of petroleum products as energy sources poses a significant environmental risk. According to the analysis of the state of the world engine industry, the most effective measures to improve the design of the engine are: development and implementation of a new workflow with effective methods of mixing and combustion; development and creation of the design of the system of automatic regulation of diesel rotation. frequency to improve fuel economy And to reduce toxicity in partial load mode, some cylinders are switched off at idle. To strengthen the requirements for fuel consumption standards and the level of toxicity of exhaust gases, as well as to increase the reliability and efficiency of agricultural power engines, it is necessary to formulate measures to improve its design. The choice of a fuel should be determined by the optimal combination of environmental and economic performance of the engine. Prospects for the use of a particular fuel of plant origin are noted. If for fuels of petroleum origin the improvement of its properties is determined by special processing, then oils with the set characteristics can be received already in "field" by selection of the corresponding grades of plants, use of fertilizers, agronomic actions, etc. The problem of reducing the consumption of diesel fuel at idle and low load can be solved by excluding from its operation part of the cylinders (this method is widely used) and closing the cycle of one cylinder. A comparative analysis of the main technical and environmental performance of the D-240 diesel engine when working on traditional and alternative fuels using the computer program Diesel-RK.

Development of a three-zone combustion model for stratified-charge spark-ignition engine

A thermodynamic model for calculating the operating process in the cylinder of a spark-ignition engine with internal mixture formation and stratified air-fuel charge based on the volume balance method was developed. The model takes into account the change in the working fluid volume during the piston movement in the cylinder. The equation of volume balance of internal mixture formation processes during direct fuel injection into the engine cylinder was compiled. The equation takes into account the adiabatic change in the volume of the stratified air-fuel charge, consisting of fuel-air mixture volume and air volume. From the heat balance equation, the change in the fuel-air mixture volume during gasoline evaporation in the fuel stream and from the surface of the fuel film due to external heat transfer was determined. Basic equations of combustion-expansion processes of the stratified air-fuel charge were derived, taking into account three zones corresponding to combustion products, fuel-air mixture and air volumes. The equation takes into account the change in the working fluid volume due to heat transfer and heat exchange between the zones and the walls of the above-piston volume. Dependences for determining the temperature in the three considered zones and pressure in the cylinder were obtained. Graphs of changes in the volumes of the combustion products, fuel-air mixture and air zones with the change of the above-piston volume in partial load modes (n=3,000 rpm) were plotted. With increasing load from bmep=0.144 MPa to bmep=0.322 MPa, at the moment of fuel ignition, the volume of the fuel-air mixture increases from 70 % to 92 % of the above-piston volume. At the same time, the air volume decreases from 30 % to 8 %. Analysis of theoretical and experimental indicator diagrams showed that discrepancies in the maximum combustion pressure do not exceed 5 %

Chemical Kinetics Modeling and Analysis of Monomethylamine for Power Plants Selective Non-Catalytic Reduction (SNCR) Systems

A study was performed to investigate monomethylamine (MMA) as an alternative or supplementary reagent for selective non-catalytic reduction (SNCR) of nitrogen oxides (NOx) for power plants especially the coal-fired type. A detailed chemical kinetics mechanism for MMA, related to the SNCR NOx reduction process, was modeled using a simplified plug flow reactor (PFR) approach using the CHEMKIN software. Model validation results were in line with reported experimental results. A model sensitivity analysis showed that the normalized MMA/NO stoichiometric ratio (NSR) and the initial NOx concentration are the most critical parameters that significantly affect MMA-based process performance. Additionally, a reduced reaction mechanism and its mechanism tree for this particular process are proposed, consisting of only 18 reactions and 21 species. Simulation comparisons with three other reagents (ammonia, urea, and cyanuric acid), under similar process conditions, indicate that MMA-based SNCR NOx reduction process has a superior performance at much lower temperatures (under 800 K) than conventional SNCR processes, with the added benefit that it does not suffer from ammonia slip problems. The MMA-based SNCR NOx removal system could be applied in cascade mode with other post-combustion NOx removal approaches to extend NOx control to lower temperatures and eliminate the temperature window limitation and potential ammonia slip of conventional SNCR systems. The cascade design is a perfect solution for coal power plants especially at partial load modes of operation which provides more flexibility in performance for such plants. The results of the simulations in this study show that the potential of MMA for SNCR NOx reduction systems at full-scale power plants has significant merit.

Анализ рабочего процесса дизельного двигателя при отключении цилиндров

The effect of cylinder deactivation as a method of controlling a diesel engine working in partial load modes is usually justified based on the characteristics corresponding to the engine performance without cylinder deactivation. However, the results obtained through theoretical analysis and in practice have significant differences, since the working processes of activated and deactivated cylinders run in different ways. In this paper, a simulation method is used to analyze the working process of the diesel engine under cylinder deactivation. The working processes in activated and deactivated cylinders are calculated using a computer model, and energy losses determining engine fuel efficiency are estimated. It is shown that the valve system in deactivated cylinders has a significant effect on the specific fuel consumption. The engine performance in partial load modes at different rotational speeds and torques and with a varying number of deactivated cylinders is investigated. The results obtained demonstrate the characteristics of the engine working process under cylinder deactivation and enable a more accurate estimation of the effect of this engine control method.

Improving the efficiency of an induction capacitor motor at partial load modes

Improving the efficiency of an induction capacitor motor at partial load modes

An Automated Flow Traversing Measurement System in the Last Stages of Large-Capacity Steam Turbines

The article presents the results from putting a new automated flow traversing measurement system (AFTMS) in an experimental turbine intended for testing steam paths of the low-pressure cylinders (LPC) of large-capacity steam turbines into use. Modern computerized facilities have been used in developing the system. Such an approach has been implemented for the first time in the full-scale test bench available at PJSC Power Machines in carrying out experimental investigations of an LPC double stage compartment (on a 1 : 1 scale) equipped with a new, ultimately long last stage blade (LSB) developed for a steam turbine plant for ultrasupercritical steam conditions. The investigations were aimed at confirming the effectiveness of the developed system in measuring the flow parameters in the last LPC stage. The necessity of making a shift from nonautomated and semiautomatic systems to the use of automated measurement systems is substantiated. The article describes a system that makes it possible, with automated setting of the gas dynamic probe head position on the traversing line, to determine the steam flow direction; to measure the stagnation pressure, static pressure, and stagnation temperature; and to record the measures indicators with exactly assigned time tags. The results from measurements of flow parameters upstream of the last LPC stage in a partial load mode are given. A comparison between the experimental and calculated flow parameter distribution data over the stage radius in the control section is shown.

Partial load efficiency analysis of a CCHP plant with RICE and H2O-LiBr absorption chiller

This paper presents a model for calculating and analyzing the global efficiency of a trigeneration system (CCHP) using 3 reciprocating internal combustion engines (RICE) as prime mover for heat and electric loads. RICE operate simultaneously and at the same load. The CCHP plant delivering energy for the office buildings of an economic operator includes also 2 absorption chillers with water-lithium bromide solution for air conditioning. The system has been analyzed for RICE partial load operation mode, linking the thermal energy output to the cooling power generation. The amount of thermal energy production is influenced by the required energy for cooling. The total cooling load in the summer is determined by both the indoor office-rooms cooling load and the data center cooling load (the energy dissipated by the data center’s components and electrical circuits). An vapor-compression chiller is operated for cooling peak load. During yearly thermal load variation, RICE are switched on or off, operate at nominal capacity or in partial load mode. The thermal efficiency of each engine changes according to the demanded heating load, determining the global efficiency variation of the trigeneration system.. The electrical efficiency of the system is also dependent on the RICE operating load that leads the electric generators. The EER factor for the absorption chillers results accordingly at partial or nominal load operating mode. The functioning graphics for each system equipment were developed based on the thermal load curve of the RICEs and the global efficiency variation graph of the trigeneration system was plotted. Finally, conclusions resulted regarding the optimal functioning of the studied trigeneration system.

Characteristics of Early Flame Development in a Direct-Injection Spark-Ignition CNG Engine Fitted with a Variable Swirl Control Valve

An experimental study was conducted to investigate the effect of the structure of the induction flow on the characteristics of early flames in a lean-stratified and lean-homogeneous charge combustion of compressed natural gas (CNG) fuel in a direct injection (DI) engine at different engine speeds. The engine speed was varied at 1500 rpm, 1800 rpm and 2100 rpm, and the ignition timing was set at a 38.5° crank angle (CA) after top dead center (TDC) for all conditions. The engine was operated in a partial-load mode and a homogeneous air/fuel charge was achieved by injecting the fuel early (before the intake valve closure), while late injection during the compression stroke was used to produce a stratified charge. Different induction flow structures were obtained by adjusting the swirl control valves (SCV). Using an endoscopic intensified CCD (ICCD) camera, flame images were captured and analyzed. Code was developed to analyze the level of distortion of the flame and its wrinkledness, displacement and position relative to the spark center, as well as the flame growth rate. The results showed a higher flame growth rate with the flame kernel in the homogeneous charge, compared to the stratified combustion case. In the stratified charge combustion scenario, the 10° SCV closure (medium-tumble) resulted in a higher early flame growth rate, whereas a homogeneous charge combustion (characterized by strong swirl) resulted in the highest rate of flame growth.

Increasing the efficiency of rotary piston engines by the use of the diesel cycle

The article deals with the task of increasing the efficiency of rotary piston engines by implementing an economical diesel cycle in a module with a three-arc epitrochoid and an external gearing kinematics scheme. The necessity of the diesel cycle is caused by the need of reducing specific fuel consumption in rotary piston engines that are currently widely used in light aviation, mostly for remotely piloted aircraft. The Wankel rotary piston engine with a two-arc epitrochoid, though having a number of advantages over traditional piston engines, is inferior to them in efficiency, particularly in partial load modes. The implementation of the diesel cycle in а cycloidal piston engine with a three-arc epitrochoid makes it possible to reduce specific fuel consumption by 30% while retaining the listed positive qualities, as well as to use diesel fuel which is preferable for high-altitude aircraft due to lesser tendency to gas formation in pipelines. The engine stator inner loop is made up by three arcs of the epitrochoid that form three working chambers equally-spaced along the perimeter, which provides a decrease of the stator thermal deformation during the operation of the engine. A method is developed to determine the geometric parameters of a rotary piston engine with a three-arc epitrochoid, and design work is carried out in the КОМPAS-3D code for a 50 h. p. diesel engine to be used in light aviation and as a drive of electrical generators, pumps and compressors for ground application.

A Dual-Side Controlled Inductive Power Transfer System Optimized for Large Coupling Factor Variations and Partial Load

In this study, a 3-kW inductive power transfer system is investigated, specifically intended for contactless vehicle charging. A series-series-compensated topology with dual-side power control and a corresponding control strategy is proposed to significantly increase the overall efficiency, especially for systems with large coupling factor variations and in partial load mode. The topology, which is closely related to the dual-active bridge converter, enables the dual-side power control without adding additional dc/dc converters to the system, and thus keeping the additional hardware effort minimal. A detailed analysis of the proposed topology is provided, and the benefits of the dual-side control are demonstrated both theoretically and experimentally. A hardware prototype is built and a peak dc-to-dc efficiency of 95.8% at 100 mm air gap and a minimal efficiency of 92.1% at 170 mm air gap is measured, including the power electronic components. The partial load efficiency at 500 W output power is still as high as 90.6% at 135 mm air gap. Overall, the proposed topology provides a practical method to overcome the main drawback of most single-side controlled inductive power transfer systems, which is a significant efficiency drop outside the nominal operating point.

Performances on engine-out emissions and combustion of ethylene glycol monobutyl ether palm oil monoester as a newtype biodiesel

In order to enhance the effect of traditional biodiesel in reducing engine-out smoke formation, the introduction of other ether group into its molecule was attempted. Now a novel biodiesel named ethylene glycol monobutyl ether palm oil monoester is developed, which owns more environment-friendly than the traditional biodiesel. The fuel was synthesized with palm oil and ethylene glycol monobutyl ether, structurally identified through FT-IR, P1PH NMR and GPC analyses. Engine test results show that when a tested diesel engine is fueled with this biodiesel(B100) and its mixture with diesel fuel(B25) in place of 0# diesel fuel(B0), engine-out smoke emissions for B100 can be significantly decreased by 9%–54.6%, while CO, NOx, and unburned hydrocarbon emissions are also lessened 50.0%–66.7%, 25.7%–37.1%, and 45.5%–58.3%, respectively, compared with B0 under partial load modes. The similar situation was also adequate to B25. In the area of combustion performances, B100 is ignited earlier during diesel engine operation, so utilization of the new biodiesel can remarkably improve engine brake thermal efficiency. Because of certain amount of oxygen contained in the new biodiesel resulting in the low calorific value, the higher cetane number and shorter ignition delay, both engine in-cylinder pressure and its changing rate with crankshaft angle are increased to some extent for ethylene glycol monobutyl ether palm oil monoester, and the combustion of it can lead to a little higher heat release rate than diesel fuel.

Design of thermal self supported 700 W class, solid oxide fuel cell module using, LSGM thin film micro tubular cells

Thermal self supporting SOFC module was studied under various conditions for high energy conversion efficiency. In order to achieve high energy conversion efficiency even under partial load condition, SOFC module and system was designed to operate at intermediate temperature by using LaGaO 3 based oxide film electrolyte. Heat loss, Q heatloss is requested to be diminished as much as possible by decreasing heat radiation and exhaust gas heat from module. SOFC module with 700 W was successfully demonstrated in thermal self-supported state under various conditions. SOFC module can be thermally self-supported within a limited temperature range (841–886 K) but energy conversion efficiency decreases with decreasing current density, because of the limited fuel and air utilization from heat value requested for thermal self-support. In this study, the energy conversion efficiency of the 700 W module shows ca. 47% low heat value (LHV) at 700 W output power with fuel utilization of 75% and even at 250 W partial load, efficiency is ca. 30% achieved. For achieving the high energy conversion efficiency in partial load mode and self-thermal supported condition, decrease in heat loss, in particular, 400 W is strongly requested.