Two-stroke Diesel Engine Research Articles

Numerical analysis of mixing and combustion characteristics of a lateral swirl combustion system in OP2S diesel engines

Opposed-Piston, Two-Stroke (OP2S) diesel engine is a potential powertrain to achieve efficient and clean combustion. However, its non-uniformity of mixing and combustion restricts performance improvement. To solve this problem, this work proposed a lateral swirl combustion system (LSCS) for the OP2S diesel engine. Applying CFD simulation, this work studied the effects of different combustion chamber parameters on the mixing and combustion performance, power, and emissions of the LSCS of the OP2S diesel engine. Furthermore, the combustion parameters were optimized by sensitivity analysis and parameter normalization methods. The results show that the LSCS helps improve the non-uniformity of mixing & combustion of the OP2S diesel engine, accelerate burning, improve the power of the OP2S diesel engine and reduce soot emissions. Besides, under certain fuel supply conditions, it is necessary to make good use of the space of the axial and radial sections of the combustion chamber and make the convex edge height realize the split-flow effect. Therefore the performance of the LSCS can be improved effectively in the OP2S diesel engine.

ANALYSIS OF EXISTING SUPERCHARGING SYSTEMS AND PERSPECTIVES OF APPLICATION OF ELECTRIC DRIVE IN SUPERCHARGING UNITS

The article analyzes modern solutions for increasing engine power by improving the air supply system. Single-stage and multi-stage pressurization schemes with gas, mechanical and combined connection in several variations are considered, their positive and negative sides for modern mechanical engineering are revealed.
 The simplest and most common is the turbocharging system, in which the turbine rotates only under the exhaust gases and this drives the compressor. Consideration should be given to the features of the working process of two-stroke diesel engines. At low speeds, there is not enough energy from the exhaust gases to drive the turbocharger. The second option is schemes in which the turbine and compressor shafts are connected to the engine shaft using a mechanical transmission. Another scheme is also possible in which the compressor and turbine can be separately connected to the crankshaft. Such solutions ensure synchronous operation of the compressor and reciprocating engine in all modes, improve the gas exchange process, improve performance in transient conditions and improve starting properties. One successful solution for two-stroke diesel engines is the development of a combined supercharging system with an intercooler, which are already considered multi-stage systems. They are generally divided into two schemes, in the first scheme the drive compressor is a high pressure degree, and the turbocharger is low pressure, the second scheme is vice versa. It is the first option that is more often used for two-stroke diesel engines, since the power consumption for driving the compressor is less, which causes a slightly higher engine efficiency. Injectivity is close to engines with conventional gas turbine supercharging.
 Over the past 7 years, the approach to improving the pressurization system has undergone some changes, Electric Boosting Systems for civilian vehicles have appeared. One of the first companies were Audi, Daimler, Land Rover, which began to equip their vehicles with electric supercharging. Currently, such large companies as BorgWarner and Garrett can be considered ambassadors of this technology. For example, AMG, together with Garrett, developed and introduced serial electric turbocharging. The problem of using an electric drive in boost systems has been lately gaining more publicity, it is already possible to conclude that there is great potential and the possibility of using such developments for domestic two-stroke diesel engines.

Modeling and Optimization of Ship Waste Heat Utilization System Based on Genetic Algorithm and Sensing

In order to solve the optimization problem of ship waste heat utilization system, the modeling and optimization method of ship waste heat utilization system based on genetic algorithm and sensing is proposed. The 6S50ME-C8.2 volume method model was established based on Matlab/Simulink simulation platform. According to the test data of the 6S50ME-C8.2 diesel engine, the simulation value is very close to the test value, which verifies the accuracy of the simulation model. The experimental results show that the thermal efficiency of high-power medium and low-speed two-stroke diesel engines is high, the exhaust temperature of the main engine is generally maintained at about 230°C, and the energy content of exhaust gas is relatively low. If no other measures are taken, the waste gas is directly channeled into the waste heat boiler, which cannot effectively recover the heat in the waste gas. Conclusion. The model can well simulate the actual working condition of the diesel engine, and the exhaust temperature has reached 298°C. The energy quality of waste gas at the inlet of the waste heat boiler is improved to meet the requirements of the waste heat recovery system.

An efficient approach to improve thermal efficiency on a low-speed two-stroke marine diesel engine

To increase the intensity of the swirl motion and further optimize the combustion characteristics, an efficient approach named cylinder gas recirculation (CGR) is proposed in this study. The effects of the CGR strategy on the swirl motion, process of fuel/air mixing, combustion characteristics, and energy distribution are investigated. Compared to the original case, the simulation results show that the CGR strategy can increase the swirl ratio with a 131.8 % increase at TDC, and the mass of cylinder recirculated gas only accounts for 3.65 % of the total mass of the charge in the cylinder. The enhanced swirl motion can improve the fuel/air mixing effect, and further optimize subsequent combustion characteristics. On the one hand, the STD value of the cases using the CGR strategy becomes smaller compared to the original case, showing the better mixing process of the fuel and surrounding charge in the cylinder. On the other hand, the enhanced swirl motion accelerates the combustion rate, specifically, the duration of CA50 ∼ CA90 of the CGR case and CGR-optimal case is reduced by 42.96 %, and 51.96 %, respectively. In the end, compared to the original case, the gross indicated work under the CGR and CGR-optimal case is increased by 0.61 % and 2.4 %, and the effective power output increases by 1.24 % and 4.84 %, respectively, which proves that the CGR strategy has great potential in improving thermal efficiency and reducing fuel consumption.

Design of Container Ship Main Engine Waste Heat Recovery Supercritical CO2 Cycles, Optimum Cycle Selection through Thermo-Economic Optimization with Genetic Algorithm and Its Exergo-Economic and Exergo-Environmental Analysis

In the present study, energy and exergy analyses of a simple supercritical, a split supercritical and a cascade supercritical CO2 cycle are conducted. The bottoming cycles are coupled with the main two-stroke diesel engine of a 6800 TEU container ship. An economic analysis is carried out to calculate the total capital cost of these installations. The functional parameters of these cycles are optimized to minimize the electricity production cost (EPC) using a genetic algorithm. Exergo-economic and exergo-environmental analyses are conducted to calculate the cost of the exergetic streams and various exergo-environmental parameters. A parametric analysis is performed for the optimum bottoming cycle to investigate the impact of ambient conditions on the energetic, exergetic, exergo-economic and exergo-environmental key performance indicators. The theoretical results of the integrated analysis showed that the installation and operation of a waste heat recovery optimized split supercritical CO2 cycle in a 6800 TEU container ship can generate almost 2 MW of additional electric power with a thermal efficiency of 14%, leading to high fuel and CO2 emission savings from auxiliary diesel generators and contributing to economically viable shipping decarbonization.

Techno–Economic and Risk Evaluation of Combined Cycle Propulsion Systems in Large Container Ships

Owing to the stringent regulations on pollutant emissions that are imposed by the International Maritime Organization and increasing fuel prices, there has been significant research on developing cleaner fuels and novel propulsion systems. This study presents a techno-economical and risk assessment method for evaluating alternative propulsion technologies and cleaner fuels as substitutes for heavy fuel oil and two-stroke diesel engines in marine transportation. This analysis was carried out for two different journeys. Accordingly, we evaluated the economic benefits of using an enhanced intercooler/reheat combined gas and steam cycle or simple and intercooler/reheat combined gas and steam cycles that were fueled by marine diesel oil or liquified natural gas instead of a two-stroke diesel engine that was fueled by MDO as the propulsion system in a large container ship, considering different shipping routes. The results highlighted the advantages of implementing the simple, intercooler/reheat, and enhanced combined gas and steam cycles as propulsion systems. A sensitivity analysis was performed to investigate the effects of the fuel cost, capital cost, and hull fouling resistance on the economic analysis. For the routes that were considered herein, compared to a two-stroke diesel engine that was fueled by MDO, the simple, intercooler/reheat, and enhanced gas and steam combined cycles that were fueled by LNG increased the net present value by 78.3%, 78.5%, and 76.4%, respectively, and reduced the payback period by 38.8%, 38.9%, and 35%, respectively. Furthermore, the fuel and capital costs had a significant influence on the overall economic profit.

An Optical Engine Used as a Physical Model for Studies of the Combustion Process Applying a Two-Color Pyrometry Technique

This work describes an experimental installation for the investigation of the combustion and injection processes. This installation is based on a two-stroke direct injection diesel engine with a total displacement of 3 L and a cylinder head equipped with three quartz windows. The windows are optical accesses that allow studying the process of injection, the atomization and evaporation of the fuel jet in an inert atmosphere (nitrogen), and the combustion process in a reactive atmosphere (ambient air). Additionally, the application of a two-color pyrometry technique to measure soot formation in this facility is presented. A methodological study is carried out regarding the influence of the dynamic range of the detectors and the wavelengths used. Maps of KL2C, flame temperature, and error probability are presented. The use of cameras with high dynamic range provides better results since the system seems to be less sensitive to measurement noise, and fewer points are obtained with a non-physical solution. Moreover, an appropriate combination of interference filters can improve the reliability of the solution. The greater the difference between the wavelengths of both interference filters, the fewer points with a non-physical solution, which improves the reliability of results.

Techno-Environmental Mission Evaluation of Combined Cycle Gas Turbines for Large Container Ship Propulsion

The stringent regulations set by the International Maritime Organization on pollutant emissions combined with the rise in fuel prices have stimulated research on cleaner fuels and new propulsion systems. This study describes a new method for evaluating alternative technologies and cleaner fuels that can be utilised in the marine sector to replace heavy fuel oil and diesel engines, and thus improve their performance while lowering carbon dioxide and nitrogen oxide emissions. The proposed techno-environmental technique allows consistent evaluation of simple intercooler/reheat gas and steam combined cycles fuelled by marine diesel fuel and liquefied natural gas, instead of a two-stroke diesel engine fuelled by marine diesel fuel, as a propulsion system of a large container ship. The implementation of the enhanced combined gas and steam cycles, and combined gas and steam cycles, fuelled by liquefied natural gas, increases the engine’s efficiency by 11% as compared with that of two-stroke diesel engines that run on marine diesel oil, while decreasing carbon dioxide and nitrogen oxide emissions by 44.7% and 76.3%, respectively. In addition, the advantages of using a gas and steam combined cycle to burn LNG over the gas and steam combined cycle for burning marine diesel oil are demonstrated.

Identification and analysis of the factors to realizing variable intake/exhaust phases in opposed-piston two-stroke diesel engines

The opposed-piston, two-stroke (OP2S) diesel engine is a potential power system to promote thermal efficiency, but the engine has an inferior scavenging performance. Through variable intake/exhaust times, the combustion process can be effectively facilitated. For example, the VVT technology is used in traditional engines. However, this technology has not been applied to OP2S diesel engines. This present work analyzed parameters influencing the intake/exhaust times to find a way to realize variable intake/exhaust times in OP2S diesel engines. These parameters affecting intake/exhaust times were mainly focused on, for example, crank to link ratio (CLR), piston phase difference (PPD), and port height (PH). Through investigating their influence on IMEP, scavenging efficiency, and trapping efficiency, we evaluated the different schemes from performance, intake/exhaust phases, and realization cost. The results show that the PH scheme significantly precedes the PPD and CLR schemes for realizing the variable intake/exhaust times. The PH scheme owns a more extensive phase adjustment range of 31°CA, the IMEP of 0.75 MPa, and the scavenging efficiency of 0.74. To achieve better power and scavenging performance, the EPH should be 37.5% higher than IPH, and the PPD should be kept below 15°CA.

Study on Engine Performance and Combustion System Optimization of a Poppet-Valve Two-Stroke Diesel Engine

Two-stroke engines have higher power density than traditional four-stroke engines, and therefore are suitable for engine downsizing. In this work, a four-stroke single-cylinder diesel engine is modified for two-stroke operation, and the combustion system is designed and optimized using a 3D simulation. Three different combustion chamber profiles and injection spray angles are compared to determine an optimized combustion system. The engine test results show that the two-stroke engine equipped with the newly designed combustion system is able to achieve the same effective power output at a much lower speed than the original four-stroke engine, as well as obtain a better indicated thermal efficiency. This indicates that the poppet-valve two-stroke engine could be an effective technical approach for engine downsizing.

Investigation of future low-carbon and zero-carbon fuels for marine engines from the view of thermal efficiency

The use of low-carbon and zero-carbon alternative fuels on marine engine is the main measure to achieve carbon neutrality for shipping sector, thus attracting numerous research on fuel techno-economics, fuel safety and fuel production chains. However, among the factors that determine whether a fuel can finally be successfully marketed, the thermal efficiency of the fuel is very important as one of the cores in determining the operation cost. To evaluate the thermal efficiency of marine alternative fuels, a new theoretical engine cycle, Miller–Sabathe cycle, is proposed to identify thermal efficiency optimization potential of fuels under certain constraints. The Miller–Sabathe cycle can simultaneously optimize the combustion process and gas exchange process, offering a more comprehensive comparison of fuel thermal efficiency. Compared with technologies based on specific engine design or operation conditions, the Miller–Sabathe cycle analysis provides broader thermal efficiency optimization guidance, and is easy to generalize to different types of engines under different operating conditions. Based on the Miller–Sabathe cycle, a zero-dimensional model is built to further consider the influence of actual losses on thermal efficiency. Then the brake thermal efficiency of various alternative fuels under the Miller–Sabathe cycle is compared using a marine two-stroke diesel engine specifications. The theoretical Miller–Sabathe cycle analysis results shows that under a certain Miller cycle strength and an appropriate ratio of constant volume combustion, the maximum thermal efficiency is capable to increase to 71.17%. The results of 0-D model suggests that the brake thermal efficiency of the marine diesel engine is capable to reach 53.09% by balancing the power performance and actual losses. At last, the results of the alternative fuels calculation suggests that among several alternative fuels, the overall thermal efficiency of ammonia has significant advantages, which makes it a very economical zero-carbon fuel. These results may contribute to the future design of low-carbon emissions and high thermal efficiency engines.

Simulation about the Effect of the Height-to-Stroke Ratios of Ports on Power and Emissions in an OP2S Engine Using Diesel/Methanol Blends

Zero carbon emissions will dominate the future of internal combustion engines (ICEs). Existing technology has pushed the performance of ICEs operating on traditional working principles to almost reach their limit. The new generation of ICEs needs to explore new efficient combustion modes. For new combustion modes to simplify the emission after treatment, the opposed-piston, two-stroke (OP2S) diesel engine is a powertrain with great potential value. Combined with dual-fuel technology, the OP2S diesel engine can effectively reduce carbon emissions to achieve clean combustion. Hence, methanol/diesel dual fuel was burnt in the OP2S engine to create a clean combustion mode for future demands. In the present work, a 1D simulation model of an OP2S diesel engine was established and verified. We investigated the influence of port height to stroke ratio (HSR) on power and emission performances of the OP2S diesel engine under different methanol ratios. The results show that the methanol ratio extremely influences the indicated power (IP) with the HSR of intake ports increasing. The IP decreases by about 1.8–2.0% for every 5% increase in methanol. Correspondingly, the methanol ratio extremely influences the indicated thermal efficiency (ITE), with the HSR of exhaust ports increasing. The ITE increases by about 2.1–3.1% for every 5% increase in methanol. The increasing methanol ratio reduces the HSR of ports for the optimal IP and ITE. To balance power performance and emission performance, the methanol ratio should be kept to 10–15%.

Multi-factors of fuel injection pressure peak of the pressure amplification common rail fuel system for two-stroke diesel engines

In this study, the fuel injection pressure peak of the pressure amplification common rail fuel system for two-stroke diesel engines was investigated in detail. A prediction model of the fuel injection pressure peak, which takes cubic cross-terms into account, was proposed utilizing the fully validated AMESim model. The Pearson correlation, determination and adjusted determination coefficients of the prediction model are 0.998, 0.997, and 0.984, respectively, indicating an excellent predictive ability. Meanwhile, the maximum relative error between the observed and predicted samples within the training group is only 3.82%, the accuracy of the model was further proved. Then the analysis of variance (ANOVA) was performed upon the developed prediction model, the P-value of each term was used to determine whether it was statistically significant. The results show that the hydraulic piston diameter, fuel plunger diameter, high-pressure fuel tube (HPFT) diameter, and the flow capacity of the pressure amplification control valve (PACV) are significant single factors. For the square terms, the squares of diameters of the fuel plunger and the HPFT impact the fuel injection pressure peak obviously. Among the quadratic terms, the interactions between the diameters of hydraulic piston and HPFT, between the diameters of fuel plunger and HPFT, between the diameter of HPFT and flow capacity of PACV, and between the diameter of fuel plunger and the length of HPFT contribute to the change of fuel injection pressure peak significantly. As for cubic terms, the interaction among fuel plunger diameter, the diameter and length of HPFT is the only one that significantly affects the fuel injection pressure peak. In contrast, the other factors have little impact on the fuel injection pressure peak. Finally, the influence of the significant elements on the fuel injection pressure peak was researched in detail.

Effect of boundary conditions and n-heptane on methyl decanoate HCCI combustion and emission based on two-stroke diesel engine

The initial boundary conditions, combustion, and emission characteristics of methyl decanoate (MD) mixed with different proportions of n-heptane (N-Hep) for homogeneous charge compression ignition (HCCI) are studied in this work. MAN B&W 6S70MC two-stroke diesel engine was used as the engine model of the reactor. The results showed that, when the equivalence ratio is 0.48, the NO emissions in the MD and N-Hep HCCI combustion process decrease with the decrease of the initial temperature. The initial temperature is determined to be 380 K. At the same time, NO emissions decrease with the increase of initial pressure, and the initial pressure is determined to be 1.3 atm. The results also indicate that, at a certain initial temperature, the initial pressure and total mole fraction of fuel, CO2, NOx reaction rates, and emissions are reduced significantly with the increase of N-Hep percentage in MD and N-Hep mixing combustion.

Influence of the Port Height to Stroke Ratio on the Performance of an OP2S Engine Fueled with Methanol/Diesel

Zero carbon emission is a mainstream trend in the development of internal combustion engines (ICEs) in the future. ICEs need to constantly surpass the existing working mechanism, especially in order to explore the possibility of new combustion methods. Dual-fuel combustion is a good way to reduce carbon emissions and achieve clean combustion. However, the traditional internal combustion engine is limited by its own structure, restricting its performance improvement. The opposed-piston, two-stroke (OP2S) diesel engine is a potential power system with a high degree of structural adjustability. Therefore, this work attempted to apply methanol/diesel dual-fuel to OP2S engines in order to explore efficient and clean combustion modes in the future. In this work, a one-dimensional simulation model of an OP2S diesel engine was established and verified. The effect of the port height to stroke ratio on the performance of the OP2S diesel engine was mainly studied for different methanol blending ratios. The results show that the methanol blending ratio does not affect the port height to stroke ratio where the optimal values of the MIP and scavenging efficiency appear. The optimal methanol blending ratio for the power performance of OP2S diesel engines is 5~15%. There is a trade-off relationship between the MIP/scavenging efficiency and trapping efficiency. For the optimization of an OP2S methanol–diesel engine, priority should be given to ensuring an optimal MIP and scavenging efficiency, and then to the appropriate consideration of the trapping efficiency.

Optimization study of oil-feed parameters to improve the ring pack lubrication performance for a two-stroke marine diesel engine

The piston ring pack is one of the crucial moving parts of two-stroke marine diesel engines because it has essential functions such as lubrication, sealing, and heat conduction. An oil injection lubrication mode for the ring pack through an independent oil-feed system is remarkable for two-stroke marine diesel engines. This study established a lubrication model for the ring pack. The model coupled ring dynamics, ring mixed/boundary lubrication, inter-ring gas dynamics, and asperity contact, especially considering this specific lubrication mode. The influence of lubricating oil-feed parameters (preliminary oil film thickness, oil-feed amount, oil-feed width, oil-feed position, and oil-feed ratio) on the lubrication characteristics of the ring pack was evaluated by the minimum oil film thickness and friction loss power. Finally, the orthogonal analysis method was used to optimize the lubrication characteristics.

Optimization of Marine Two-Stroke Diesel Engine Based on Air Intake Composition and Temperature Control

The influence of gas intake temperature, composition and the volume concentration of each gas component on diesel engine combustion, emission and the output power was studied by building a calculation model of the B&W 6S35ME-B9 marine two-stroke low-speed diesel engine, followed by a comprehensive optimization exploration. The results showed that under 295 K and 18.5% O2 of intake gas, the engine’s NOx emission is only 4.5 g/kWh and reduced to 58% from the normal air gas intake condition. Moreover, their power output is very similar. In addition, the effect of CO2 or H2O added into the intake of the diesel engine on the performance of the diesel engine can be compensated by reducing the intake temperature. At the intake temperature of 295 K, the engine’s NOx emission with 20.58% O2, 77.42% N2 and 2% H2O is 8.62 g/kWh, and 9.06 g/kWh under 20.79% O2, 78.21% N2 and 2% CO2. It is lower than 11.77 g/kWh, which is under normal intake conditions (315 K, 21%O2 and 79%N2). The power output is also similar to the normal intake condition. Therefore, the comprehensive optimization of gas intake temperature, composition and concentration can effectively optimize the diesel engine’s performance in terms of combustion, emission and power output. The research results have an important reference value for the optimization of diesel engine performance.

Effect of Combustion Boundary Conditions and n-Butanol on Surrogate Diesel Fuel HCCI Combustion and Emission Based on Two-Stroke Diesel Engine

The combustion and emission characteristics of surrogate diesel fuel homogeneous charge compression ignition (HCCI) with different combustion boundary conditions and n-butanol (NB) mixing ratios are studied in this work. Engine data of a two-stroke low-speed direct-injection marine diesel engine were selected for the reactor. HCCI combustion was achieved by compressing a completely homogeneous mixture of fuel and air. The results show that NO emissions decrease slightly with the increase of initial boundary pressure at a constant equivalence ratio and initial temperature. In addition, the different initial boundary temperature has little effect on NO emission. The results also indicate that the ignition delay time of the mixed fuel rises with the increase of n-butanol mixing ratio. The emissions and reaction rate of NOx reduce significantly with the increase of n-butanol percentage in surrogate diesel fuel and n-butanol mixing combustion at a constant equivalence ratio and total mole fraction. Meanwhile, CO2 emissions also decrease significantly with the increase of n-butanol mixing ratio.

Mean value first principle engine model for predicting dynamic behaviour of two-stroke marine diesel engine in various ship propulsion operations

Analysis of ship propulsion system performance is often performed using detailed hydrodynamic models to assess load changes, which are subsequently compared to static engine limits, or by detailed engine models that are rarely integrated with sufficiently detailed propulsion models for load change estimation. To investigate the dynamic engine (overloading) behaviour and ship propulsion performance under various heavy operating conditions, a Mean Value First Principle Parametric (MVFPP) engine model is integrated into a ship propulsion system model in this paper. An upgraded thermodynamic-based MVFPP model for two-stroke marine diesel engines is presented, in particular a newly developed MVFPP gas exchange model. Based on the integrated propulsion system model of a benchmark ocean-going chemical tanker, the engine dynamic behaviour during ship acceleration, deceleration and crash stop has been investigated. Results show that, during dynamic processes, the engine could be thermally overloaded even if the engine power trajectory is inside the static engine operating envelope. The paper contributes to finding proper indicators for thermal overloading of modern two-stroke marine diesel engines. It is demonstrated that when matching the engine with the propeller and designing the ship propulsion control system, not only the static engine operating envelope, but also the dynamic engine behaviour should be considered. • Mean Value First Principle Parametric (MVFPP) model for 2-stroke marine diesel engine. • Novel approach to two-zone modelling of scavenging process. • MVFPP model is balanced choice to predict engine behavior in drive system simulation. • Static performance maps & limits inadequate for prediction of engine dynamic behavior. • MVFPP model can provide deeper understanding of thermal overloading of engines.

Research on thermoeconomic fault diagnosis for marine low speed two stroke diesel engine.

To satisfy the requirements of low fuel consumption, low emission, and high efficiency of the shipping industry, marine diesel engines are developing in the direction of automation and energy-saving, which increases the possibility and complexity of marine diesel engine failures. A one-dimension thermodynamic model for the marine diesel engine is built with AVL Boost software. The model is applied to a low-speed two-stroke 6S50MC diesel engine, and the error between the main performance parameters obtained by simulation and the test bench data is less than 3% under 100% and 75% load. Based on the model, 6 typical single faults and many typical double faults concomitant phenomena of diesel are reproduced. Based on the second law of thermodynamics, the exergy flow among the components and the external environment is analyzed. The thermoeconomic model of a marine diesel engine is established where the "fuel" and "product" of the components are defined according to their function. The fault diagnosis results show that the effects of faults generally propagate through the diesel engine system and affect the behavior of several components, resulting in induced malfunction in normal components. Therefore the malfunction MFi of each component is the superposition of the intrinsic malfunction and the induced malfunction according to the malfunction and dysfunction analysis. The thermoeconomic fault diagnosis method can be used to narrow the search range of abnormal components though it cannot accurately locate the fault.