Exhaust Valve Research Articles

A method to quantify the advantages of a variable valve train for CI engines

Today’s CI engines are subject to strict regulations of pollutant emissions and ambitious fuel consumption targets. Therefore, the interaction between the engine and the exhaust aftertreatment system (ATS) has become increasingly important. Numerous studies have shown that a variable valve train (VVT) improves the interaction between engine and ATS. However, most of these studies either quantify the advantage on a specific engine or only present complex CFD models, such that the results are not easily transferable to different engines. Thus, engine manufacturers cannot directly use these results to assess the advantage of various VVT strategies for their engines. In this paper, we propose a cycle-discrete cylinder model based on first principles which allows to simulate various VVT strategies. In contrast to present methods based on CFD, the proposed cylinder model can be realized with the equations presented. Furthermore, the model is identified with measurement data of an engine without a VVT. A separate engine, which is retrofitted with a fully VVT, is used to validate the proposed modeling approach. Using the identified model in combination with a mean-value model of the air path, we are able to simulate the effects of early intake valve closing, early exhaust valve opening, and cylinder deactivation for a complete CI engine that has no VVT installed. The model is then used to highlight the advantage of a VVT for two scenarios at part-load operation. At cold start, where the temperature of the ATS must be increased quickly, variable valve timing achieves higher enthalpy flows to the ATS while also lowering engine-out NOx emissions when compared to a standard engine strategy. If the ATS is at the operating temperature, cylinder deactivation achieves significantly higher enthalpy flows which prevents the ATS from cooling down. In addition, cylinder deactivation also lowers fuel consumption and engine-out NOx emissions.

Experimental Study of the Influences of Operating Parameters on the Performance, Energy and Exergy Characteristics of a Turbocharged Marine Low-Speed Engine

With appropriate strategy of EVC timing and fuel injection, the engine NOx emission could be reduced with acceptable deterioration of fuel consumption. However, for the mechanism of these favorable results, few studies focus on improving the fuel economy from the perspective of energy and exergy analysis, which could be helpful for providing a deeper comprehensive to researchers. Therefore, an experimental study for the combination of EVC timing and fuel injection strategy is conducted based on a marine low-speed engine with 340 mm bore, then the energy and the exergy analysis are separately carried out according to the obtained experimental results. The experimental results show that delaying the exhaust valve closing (EVC), complemented with an appropriate injection strategy, could improve the marine low-speed diesel engine brake specific fuel consumption (BSFC) with the NOx emission almost kept constant. The following energy balance analysis demonstrates that the losses from exhaust gas and heat transfer account for about 50% of total energy. However, from the perspective of exergy analysis, an opposite conclusion could be obtained; the proportion of exhaust gas and heat transfer exergy could reach about 15%, and the ratio of heat transfer could be higher relatively. The losses caused by irreversibility is the biggest source of all, and the irreversibility from combustion could takes about 70% of the total irreversibility. Finally, the reduction of total irreversibility could reach about 4% by optimizing the parameters of marine low-speed engines.

Performance research and optimization of marine dual-fuel engine based on RSM and NSGA-II

ABSTRACT In order to improve the economic efficiency of the ship when sailing and reduce the engine optimization cost. We propose the Response Surface Methodology (RSM) combined with NSGA-II to optimize the engine parameters. First, a simulation model of a marine four-stroke dual-fuel engine is established in AVL-BOOST software. Then, control parameters such as engine speed, exhaust valve opening (EVO) and compression ratio (CR) are planned by design of experiments. The response surface model was established in Design-Expert software. The significant influence of control parameters on performance parameters was studied by analysis of variance (ANOVA). Finally, with the output power, indicated fuel consumption rate and nitrogen oxide emissions as the optimization objectives. Non-dominated Sequential Genetic Algorithm (NSGA-II) is used to optimize the parameters to improve engine performance and reduce emissions. The results show that the established response surface model has good prediction accuracy. The response surface model visualizes the mathematical relationship between the control parameters and the optimization targets. The ANOVA results show that engine speed, EVO and CR have significant effects on engine performance and emissions. The optimization results show that the engine speed is 793 rpm, the EVO is 145°CA, and the CR is 12.3. Compared to standard settings, the optimized data shows a 3.4% increase in power, a 0.3% reduction in ISFC, and a 6.2% reduction in nitrogen oxide (NOx) emissions. The combination of response surface analysis and NSGA-II algorithm to optimize engine performance and emissions is thereby a feasible method.

Impacts of Charge Air Parameters on Combustion and Emission Characteristics of a Diesel Marine Engine

In this study, the operating processes of a four-stroke diesel marine engine from the intake valve closing (IVC) to the exhaust valve opening (EVO) at numerous different charge air conditions were simulated with the AVL FIRE code. The CFD models were validated with engine shop-test technical data. The results showed that increasing the charge air pressure without cooling decreased the actual amount of air supplied to the cylinder. As a result, the combustion process was suboptimal, resulting in a reduction in engine power and an increase in specific fuel oil consumption (SFOC). In addition, less air to cool the combustion chamber coupled with elevated charge air temperatures increased the in-cylinder peak temperature, leading to a significant increase in thermal nitric oxide (NO) emissions. In contrast, by cooling the charge air after turbocharging, the actual amount of air entering the engine cylinders was increased. The abundant charge air helped to cool the combustion chamber better, significantly reducing the in-cylinder peak temperature and then the thermal NO formation. Better combustion also increased engine power, which, in turn, reduced SFOC. In addition, carbon dioxide (CO2) and soot emissions were also reduced.

THE COMPOSITION OF THE PNEUMATIC SYSTEM FOR LOCAL MULTI-CIRCUIT COOLING ON AUTO TRACTOR DIESEL PARTS JUSTIFICATION

A series of motor bench and non-motorized experiments conducted at the Department of Engines and Hybrid Power Plants of NTU "KhPI" showed the high efficiency of local air cooling of heat-stressed parts of internal combustion engines, in particular, parts of the exhaust valve assembly of the gas distribution mechanism in an automated mode. However, in the tests carried out, a stationary air compressor powered by a ~220 V mains was used with air accumulation in a large-capacity cylinder. The implementation of a local cooling system on power plants, mainly powerful trucks, requires the inclusion in the automatic control system of autonomous cooling, a pneumatic compressor installed on the vehicle with an electric drive, powered by the on-board power supply and accumulating air in a receiver with compact dimensions.
 A review of design solutions and analysis of the component composition of pneumatic systems of autotractor vehicles was carried out. The requirements for the quality and safety of pneumatic systems of vehicles and their elements are considered. The technical characteristics of air compressors are presented. The scheme of the pneumatic system of local multi-circuit cooling on autotractor diesel parts has been chosen. On the example of the selected air compressor with an electric drive Maximum Performance 24V from ARB (Australia), estimates were made of the operating time up to a working pressure in the receiver of 10 bar. The electrical load on the 24 V on-board network of the vehicle was determined in the form of an average current consumption per filling cycle. The maximum current consumption by the compressor is determined, the current consumption per hour is estimated under the condition of a proportional alternation of the cycles of filling the receiver and emptying it.

Optimizing Air Compressor Productivity in Supporting Operational Activities on The Mt Ship. Gamalam

Air compressors are auxiliary machines on board that can produce high pressure air. This research was conducted because the productivity of the air compressor was less than optimal, causing air production and the performance of the air compressor to be less than optimal and disrupting operational activities on the ship. The impact that occurs when air production is reduced in the air compressor, the ship cannot operate according to the contract specified by the company, because the initial start of the main engine or main engine on board requires compressed air. Many factors can cause reduced production of air produced by air compressors, including the lack of performance of the suction valve and exhaust valve on the high pressure section which causes less maximum or longer time for filling air into the air bottle, low flow of the lubrication system on the piston which causes no compression to produce air. This research was carried out with the aim of identifying and analyzing the causes of the lack of performance of the suction and exhaust valves on high pressure sections and low flow of the piston lubrication system which results in less optimal performance of the air compressor when filling into air bottles. The method used in this study uses a qualitative descriptive method using primary and secondary data collection approaches and techniques. The lack of performance of the inlet and exhaust valves can be corrected by cleaning the carbon deposits on the valves and leveling the valve surfaces. The low flow of the lubrication system on the piston can be done by checking the lubricating oil pump, cleaning the lubricating oil filter, changing the lubricating oil periodically according to the instruction manual book, and adding lubricating oil according to the specifications of the air compressor.

Exhaust gas recirculation in a compression-ignition engine with nano coated Al2O3-TiO2 and ethanol fuel

Ethanol is a fuel that is sustainable, made from biomaterials, and oxygenated. It has the potential to lower the amount of particle emissions produced by diesel engines, as well as the amount of CO2 produced during its life cycle. Even though it was indicated by the exhaust gas recirculation (EGR) approach, the pistons, valves, and cylinder heads of the CI engine were coated in a ceramic compound composed of Al2O3 and TiO2. The exhaust gas recirculation (EGR) technology allows for the cooling and redirection of exhaust gas that has been removed from the cylinders of the exhaust system. Following the application of thermal coating to the piston, the performance of the engine's combustion system improved. The elimination of carbon monoxide, hydrocarbons, and smoke is a direct result of the addition of ethanol. According to the findings, there is a decrease in the amount of NOX emissions up to 11.72 g/kWh and 9.49 g/kWh produced by the cooled EGR engine.

Catalyst-heating operation in compression-ignition engines: A comprehensive understanding using large eddy simulations

Catalyst-heating operation in compression-ignition engines is critical to ensure rapid light-off of exhaust catalysts during cold-start. This is typically achieved by using late post injections for increased exhaust enthalpy, where retardability is constrained mainly by emissions due to inactivity of the oxidation catalyst at these conditions. Comprehensive understanding of formation mechanism of pollutant emissions is needed to optimize engine performance and minimize tailpipe harmful emissions. In this study, a computational fluid dynamics model of a medium-duty compression-ignition engine is developed and validated against with catalyst-heating operation experimental data using large eddy simulations. The engine is fueled with a full boiling-range diesel fuel and uses an optimized five-injections strategy that consists of two pilots, one main, and two post injections. Results show that, significant amounts of unburned hydrocarbons (UHCs) and oxygenated UHCs (OUHC) are formed by the pilot injections, which may persist until exhaust valve opening. UHCs accumulate mainly in the outer-upper part of the cylinder guided by the piston lip, in the inner-bowl due to the bowl geometry, near the injector nozzle by the fuel from the end-phase of injection, and in the space between spray plumes transported by the swirl motion. The main injection exhibits a short ignition delay and rapidly consumes most of UHC and OUHC, except for the central part of the chamber near the injector nozzle. The 1st post injection counteracts the expansion effect on temperature, plays a key role in increasing the exhaust enthalpy and reducing the harmful emissions by promoting combustion associated with the 2nd post injection. The fuel delivered by the 2nd post injection penetrates through the flame of the 1st post injection, creating cool flame clouds beyond the flame that eventually transition to a diffusion flame. Finally, a unique phenomenological model is proposed to better visualize the interactions of post injections.

Impact of variable exhaust valve timing on diesel engine characteristics fueled with waste cooking oil biofuel blends: A numerical analysis

The quantity of the conventional sources of energy such as petroleum, coal, and the deposits of hydrocarbon are limited in nature. The rapid growth is observed in the industrial and transportation section due to increase in population that has compelled the mankind to look for an alternative to conventional fuels. Biodiesel can be a potential substitute due to its ease of availability, accessibility, lower cost, and nontoxic characteristics. In this study, waste cooking oil (WCO) as the feedstock for biodiesel due to its abundance and low prices is chosen. It has been observed that the high prices of cooking oil have compelled people to reuse it multiple times, which can have negative health consequences such as inflammation, cholesterol issues, diabetes, and cancer. However, if people can obtain WCO at a reasonable cost, they will refrain from reusing it repeatedly. This article presents a numerical method that investigates the effects of variable exhaust valve timing on the performance, emissions, and combustion parameters of WCO and its different blends in a conventional mechanical fuel injection system diesel. The study was conducted using a single-cylinder, water-cooled, in-line diesel engine running at a constant speed. As, it is not possible to determine the values of engine performance, emissions, and combustion parameters for different valve timings experimentally, a numerical method has been adopted. The valve timing range was taken as 46–66° before bottom dead center (BDC) for exhaust valve opening and 6–20° after top dead center (TDC) for exhaust valve closing and the inlet valve opening and closing are constant at 16° b TDC and 33° a BDC, respectively.

PENGARUH VARIASI BERAT KATUP BUANG DAN KETINGGIAN INPUT PADA KINERJA POMPA HIDRAM

The hydram pump comes from the word Hydraulic Ram, which is a pump that works by relying on the beat of a hydraulic system that can work without using electricity or fuel. Hydram pumps work by harnessing the potential energy in water in a straight pipe and then turning it into dynamic pressure which results in the creation of a water strike resulting in high pressure in the pump. The purpose of this study was to determine the effect of variations in exhaust valve weight and input height on the performance of the hydram pump. The exhaust valve weight variables used in this study were 0 gram, 40 gram, 50 gram and 60 gram, with the input height from the surface of 190 cm and 240 cm. The analysis technique is carried out by examining the data obtained from the research results, where the results are in the form of quantitative data made in tabular form and displayed in graphical form. The results of the study showed the highest efficiency of 52.47% at a height of 240 cm, and at a height of 190 cm the highest efficiency was obtained at 40.75%, and the highest yield water discharge at a valve weight of 50 grams was 6.51 l/minute at a height of 240 cm. and at a height of 190 cm, the resulting water discharge is 3.80 l/minute with a valve weight of 50 grams.

The Effect of Ceramic Coating on Performance and Emission of Diesel Engine Operated on Diesel Fuel and Biodiesel Blends

In this work, the effect of ceramic coating on performance, exhaust gas temperature and gases emissions of diesel engine operated on diesel fuel and biodiesel blends was investigated. A conventional four stroke, direct injected, single cylinder, diesel engine was tested at constant speed and at different load conditions using diesel fuel and biodiesel blends. The inlet and exhaust valves, the head of piston and cylinder head of the engine were coated by ceramic materials. Ceramic layers were made of (210-240) μm of Al2O3 and (30-60) μm of 4NiCr5Al as a bond coat for inlet and exhaust valves and (350-400) μm of YSZ and (50-100) μm of 4NiCr5Al as a bond coat for head of piston and (280-320) μm of Sic and (40-80) μm of 4NiCr5Al as a bond coat for cylinder head. The coating technique adapted in this work is the flame spray method. The engine with valves, piston and cylinder head ceramic coated research was tested for the same operation conditions of the engine (without coating). The results showed that a reduction in brake specific fuel consumption of 19.29%, 15.91%, 14.65% and 7.06%, an increase in brake thermal efficiency of 23.68%, 19.77%, 16.51% and 6.32%, the increase in exhaust gas temperature of 9.01%, 7.22%, 15.7% and 11.42%, the reduction of CO emission of 18.57%, 20%, 20.5% and 27.77%, the reduction of HC emission of 28.97%, 43.9%, 38.88% and 36.41% for diesel, B5,B10 and B100 respectively.

Study on the performance characteristics and failure analysis of exhaust valves

Abstract Exhaust valves are a type of valve that can commonly be found in the top section of the cylinder block in an engine. When failures occur on the exhaust valve, the engine has a high possibility to result engine failure or breakdown. This will affect the user where the user requires to spend a huge amount on repairing costs or engine replacement. Thus, this research aims to investigate the effect of the exhaust valve’s material on its performance and identify the appropriate material which could increase its fatigue life in a four-stroke internal combustion diesel engine. A three-dimension (3D) Computer-aided design model of the exhaust valve was generated by using SOLIDWORKS and undergo static structural analysis as well as thermal analysis. The measure variables are von-mises stress, total deformation, temperature, total heat flux and directional heat flux by using ANSYS Finite Element Analysis. Stainless steel 304 alloy and Aluminium-Silicon Carbide (Al-Sic) materials are the manipulated variable that was applied to the 3D CAD model exhaust valve to undergo all the analyses. Before performing all the analyses, the appropriate mesh method and mesh sizing was identified by referring to the mesh metrics spectrum and performing a mesh independence test. The results from the analysis were collected and tabulated for comparison and discussion purposes. From the analysis, the maximal thermal stress was determined in the valve stem region. By appointing Stainless Steel 304 alloy on the exhaust valve, the durability and the fatigue life are improved as the material can achieve a smaller value of temperature distribution, total heat flux, total deformation, and higher von-mises stress. This research provided a better understanding of the effect of an exhaust valve material on its performance characteristic.

Assessment of engine valve materials

This paper presents an analysis of six sets of engine valves, each set consisting of one exhaust valve and one intake valve. Each pair of valves was used in an engine with different displacement and mileage. The valves were subjected to microscopic analysis, hardness measurement and chemical composition analysis using a glow discharge spectrometer and energy dispersive spectroscopy (EDS). The design and materials of the valves showed that both the intake and exhaust valves in their present form would be a strength of the engine.

The effect of intake port shape on in-cylinder flow field and turbulence distribution in a high-tumble production engine with endoscope accesses

Three cylinder heads with varied intake port shapes are experimentally investigated to evaluate intake flow structures and their influence on near top dead centre (TDC) flow fields and turbulence distributions in a motored high-tumble engine. The endoscopic high-speed particle image velocimetry (eHS-PIV) is implemented in multi-cylinder engines with two laser endoscopes and a camera endoscope installed in the cylinder head. For a range of engine load and speed conditions, particle seeded and laser illuminated high-speed movies are recorded for 100 cycles with which ensemble-averaged flow fields and spatial-filtered high-frequency flow magnitude distributions are analysed. The results show that a straighter intake port producing a more lateral flow direction results in a larger swinging arc, which is related to enhanced flow later in the compression stroke. The tumble vortex shows an asymmetric structure; the flow field during the compression stroke exhibits higher magnitude vectors at the leading head. This surging flow head becomes stronger with a straighter intake port, which leads to enhanced tumble vortex formation near TDC. As it becomes very strong, the flow vectors originally directed towards the exhaust valves bounce back towards the intake valves, causing a very complex flow structure involving multiple flow components. The result is enhanced turbulence throughout the late compression stroke including the spark timing. However, the impact of the straighter intake port shape on TDC turbulence becomes less significant at lower engine load and speed conditions as the lower intake air momentum limits the enhancement.

Physics-Based Modelling for On-Line Condition Monitoring of a Marine Engine System

The engine system is critical for a marine vehicle, and its performance significantly affects the efficiency and safety of the whole ship. Due to the harsh working environment and the complex system structure, a marine system is prone to have many kinds of novelties and faults. Timely detection of faults via effective condition monitoring is vital for such systems, avoiding serious damage and economic loss. However, it is difficult to realize online monitoring because of the limitations of measurement and health monitoring methods. In this paper, a marine engine system simulator is set up with enhanced sensory placement for static and dynamic data collection. The test rig and processing for static and dynamic data are described. Then, a physics-based multivariate modeling method is proposed for the health monitoring of the system. Case studies are carried out considering the misfire fault and the exhaust valve leakage fault. In the misfire fault test, the exhaust gas temperature of the misfired cylinder dropped from the confidence interval 100–150 °C to 70–80 °C and the head vibration features decreased from the confidence interval 900–1300 m/s2 to around 200–300 m/s2. For the exhaust valve leakage fault, the engine body vibration main bearing impact RMS increased nearly 10 times. Comparisons between the model-predicted confidence interval and measured data reveal that the proposed model based on the fault-related static and dynamic features successfully identified the two faults and their positions, proving the effectiveness of the proposed framework.

Chemical Modeling of Constant-Volume Combustion of the Mixture of Methane and Hydrogen Used in Spark Ignition Otto Cycles

This paper develops a chemical model for a closed constant-volume combustion of a gaseous mixture of methane and hydrogen. Since the combustion is strongly dependent on temperature, pressure and fuel composition, these had chosen the actual corresponding thermodynamic systems in this kind of combustion, i.e., spark ignition (SI) reciprocating engines, to assess combustion parameters and flue gas composition. The actual cycles impose extra restrictive operational conditions through the engine’s-volumetric-compression ratio, the geometry of the combustion volume, the preparation method of the mixture of methane and hydrogen, (e.g., one fueling way of a homogeneous mixture obtained in a specific device or by two separate fueling ways for components), the cooling system and the delivered power. The chemical model avoided the unknown influences in order to accurately explain the influence of hydrogen upon constant-volume combustion and flue gas composition. The model adopted hypotheses allowing to generalize evaluated results, i.e., the isentropic compression and expansion processes, in closed constant-volume combustion caused by two successive steps that obey the energy and mass conservation laws, and the flue gas exhaust, which is also described by two steps, i.e., isentropic expansion through the flow section of exhaust valves followed by a constant pressure stagnation (this process, in fact, corresponds to a direct throttling process). The chemical model assumed the homogeneous mixtures of gases with variable heat capacity functions of temperatures, the Mendeleev—Clapeyron ideal gas state equation, and the variable chemical equilibrium constants for the chosen chemical reactions. It was assumed that the flue gas chemistry prevails during isentropic expansion and during throttling of exhaust flue gas. The chemical model allowed for evaluation of flue gas composition and noxious emissions. The numerical results were compared with those recently reported in other parallel studies.

Enhanced Exhaust after-Treatment Warmup in a Heavy-Duty Diesel Engine System via Miller Cycle and Delayed Exhaust Valve Opening

The exhaust after-treatment (EAT) threshold temperature is a significant concern for highway vehicles to meet the strict emission norms. Particularly at cold engine start and low loads, EAT needs to be improved above 250 °C to reduce the tailpipe emission rates. Conventional strategies such as electrical heating, exhaust throttling, or late fuel injection mostly need a high fuel penalty for fast EAT warmup. The objective of this work is to demonstrate using a numerical model that a combination of the Miller cycle and delayed exhaust valve opening (DEVO) can improve the tradeoff between EAT warmup and fuel consumption penalty. A relatively low-load working condition (1200 RPM speed and 2.5 bar BMEP) is maintained in the diesel engine model. The Miller cycle via retarded intake valve closure (RIVC) is noticeably effective in increasing exhaust temperature (as high as 55 °C). However, it also dramatically reduces the exhaust flow rate (over 30%) and, thus, is ineffective for rapid EAT warmup. DEVO has the potential to enhance EAT warmup via increased exhaust temperature and increased exhaust flow rate. However, it considerably decreases the brake thermal efficiency (BTE)—by up to 5%—due to high pumping loss in the system. The RIVC + DEVO combined technique can elevate the exhaust temperature above 250 °C with improved fuel consumption—up to 10%—compared to DEVO alone as it requires a relatively lower rise in pumping loss. The combined method is also superior to RIVC alone. Unlike RIVC alone, the RIVC + DEVO combined mode does not need the extreme use of RIVC to increase engine-out temperature above 250 °C and, thus, provides relatively higher heat transfer rates (up to 103%) to the EAT system through a higher exhaust flow rate. The RIVC + DEVO combined method can be technically more difficult to implement compared to other methods. However, it has the potential to maintain accelerated EAT warmup with improved BTE and, thus, can keep emission rates at low levels during cold start and low loads.

APPLICATION OF FE3AL INTERMETALLIC PHASE FILLER METAL IN VALVE SEATING FACE HARD FACING

The exhaust valve seat face is a surface that degrades slowly as a result of mechanical and thermal stresses. There is extensive research on new materials for valves and for the improvement of valve production technology. This paper discusses the method of obtaining a filler metal made of Fe3Al intermetallic phase and the method of TIG hard-facing on a valve seating face made of H9S2 steel, evaluating the effects of essential hard-facing parameters. The resulting hard-facing build up was assessed in terms of quality using industrial radiography testing (RT).

Uji Pengaruh Beban Klep Buang Serta Ketinggian Input Dan Output Terhadap Efisiensi Pompa Hidram

Water is a natural material that is very important for humans, animals and plants. Apart from being used as consumption, water can also be used as an energy source, with the need for water use which is very important for humans, it needs to be supported by an increase in water supply. Water supply usually uses a pump that functions to raise water from a lower place to a higher place. However, there are still many people who still have difficulty meeting their water needs due to the weak purchasing power of the people to buy pumps, especially in rural areas. Therefore, it is necessary to design a hydraulic ram pump which is one solution to overcome this problem because it is cheap and simple to manufacture and maintain. A hydraulic ram pump is a pump that can raise water from a low place to a higher place using energy that comes from the water flow itself. To find out the performance of the hydraulic ram pump, a pump efficiency test was carried out with the treatment of different heights of water flow sources, different heights of water lifted and different exhaust valve loads. The results of efficiency testing are obtained that the higher the water flow source the greater the efficiency, the lower the water lift the greater the efficiency and the lightest load on the exhaust valve has the greatest efficiency. Keywords: water, pump, hydraulic ram pump, efficiency

Construction of Nitrogen Content Observer for Fuel Cell Hydrogen Circuit Based on Anode Recirculation Mode

The anode recirculation mode is increasingly being adopted in today’s fuel cell systems. The recycling of hydrogen gas can effectively improve fuel utilization and the wider economy. However, using the purge strategy for the recirculation exhaust has a significant impact on the operational performance and economic efficiency of fuel cell systems.Experiments have shown that, when the purge interval increases from 6 s to 10 s, the recirculation pump power increases by about 20%, the nitrogen content in the exhaust gas increases, and the stack voltage shows a 10 V attenuation. The accumulation of nitrogen permeation in the anode circuit leads to the degradation of the fuel cell performance. Therefore, it is necessary to discharge the accumulated nitrogen through the purge valve in a timely manner. However, opening the exhaust valve with excessively high frequency can result in the unreacted hydrogen being discharged, which reduces the economic efficiency of the fuel cell. This paper is based on the principle of mass conservation and models each subsystem of the anode circuit in the recirculation pump mode of the fuel cell separately, including the proportional valve model, the hydrogen consumption model of the fuel cell, the nitrogen permeation model of the fuel cell, the neural network model of the circulating pump, and the purge valve model. These submodels are integrated to construct a nitrogen content observer for the hydrogen circuit, which can estimate the nitrogen content. The accuracy of the model is validated through experimental data. The estimation error is less than 5.5%. The nitrogen content in the anode circuit can be effectively estimated, providing a model reference for purge operations and improving hydrogen utilization.