Pub Date : 2023-08-18DOI: 10.1177/09576509231196268
S. Owen, F. Taremi, M. Uddin
To better understand the effect of vortex shedding on the nature of the trailing edge shock system during airfoil limit loading a computational fluid dynamic investigation was performed for a transonic turbine airfoil at sublimit, limit and supercritical conditions. Four modeling strategies were employed: steady state RANS, unsteady RANS, DDES, and turbulence model free. The influence of transient modeling approaches on the predicted mass-flow averaged total pressure loss coefficient, mass-flow averaged flow angles, and on the limit loading pressure ratio were found to be insignificant with the exception of the URANS model during critical loading. It was found that the URANS modeling approach failed to predict the transition from near trailing edge dominated vortex formation to base pressure vortex formation resulting in a drastic rise in predicted total pressure loss. Surface isentropic Mach distributions were predicted similarly for all modeling strategies, with the exception of the trailing edge base pressure region and points of shock impingement along the suction surface. A detailed review of the boundary layer states at the trailing edge was performed. It was found that all of the modeling approaches predicted laminar boundary layer profiles along the pressure surface trailing edge and turbulent profiles along the suction surface. The predicted base pressure distributions were also reviewed, showing the base pressure to decrease with increasing pressure ratio. The unsteady simulation approaches consistently predicted lower average surface pressures than the steady state RANS simulations. Qualitative images of the numerical Schlieren contours were presented and reviewed showing large differences in the prediction of vortex shape, size, and subsequent shock influence.
{"title":"A characterization of unsteady effects for transonic turbine airfoil limit loading","authors":"S. Owen, F. Taremi, M. Uddin","doi":"10.1177/09576509231196268","DOIUrl":"https://doi.org/10.1177/09576509231196268","url":null,"abstract":"To better understand the effect of vortex shedding on the nature of the trailing edge shock system during airfoil limit loading a computational fluid dynamic investigation was performed for a transonic turbine airfoil at sublimit, limit and supercritical conditions. Four modeling strategies were employed: steady state RANS, unsteady RANS, DDES, and turbulence model free. The influence of transient modeling approaches on the predicted mass-flow averaged total pressure loss coefficient, mass-flow averaged flow angles, and on the limit loading pressure ratio were found to be insignificant with the exception of the URANS model during critical loading. It was found that the URANS modeling approach failed to predict the transition from near trailing edge dominated vortex formation to base pressure vortex formation resulting in a drastic rise in predicted total pressure loss. Surface isentropic Mach distributions were predicted similarly for all modeling strategies, with the exception of the trailing edge base pressure region and points of shock impingement along the suction surface. A detailed review of the boundary layer states at the trailing edge was performed. It was found that all of the modeling approaches predicted laminar boundary layer profiles along the pressure surface trailing edge and turbulent profiles along the suction surface. The predicted base pressure distributions were also reviewed, showing the base pressure to decrease with increasing pressure ratio. The unsteady simulation approaches consistently predicted lower average surface pressures than the steady state RANS simulations. Qualitative images of the numerical Schlieren contours were presented and reviewed showing large differences in the prediction of vortex shape, size, and subsequent shock influence.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76205205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-12DOI: 10.1177/09576509231195222
Jia Liu, Fan Zhang, Mengbin Song, Lufeng Zhu, Desmond Appiah, S. Yuan
To reveal the energy loss mechanism of the centrifugal pump, numerical simulation and experimental investigation are conducted to obtain the complex flow field of a single-stage centrifugal pump under various flow conditions. Particular emphasis is focused on the qualitative and quantitative analysis of the distribution and variation characteristics of irreversible loss in the pump model. The results show that the energy loss in the centrifugal pump mainly originates from the entropy generation caused by the turbulent dissipation and wall friction, which are typically generated in the volute and impeller domains. It is worth noticing that the energy loss in the volute is closely associated with non-uniform velocity distribution and the evolution of the shedding vortices from the impeller exit whilst the energy loss in the impeller are greatly affected by unstable flow phenomena such as flow separation, backflow, and jet-wake pattern. At the overload operating conditions, the wall entropy generation possesses a substantial influence on energy loss, which is mainly related to the wall shear stress. Meanwhile, the influence of the rotor-stator interaction and inflow impacting on the energy loss is enhanced with increasing flows. Finally, the omega method captured the vorticity structures near the tongue at partial flow conditions, thereby, revealing the relationship between the high magnitude of flow loss and the evolution of different scales of strong vorticity sheets.
{"title":"Effects of unstable flow structures on energy transfer mechanism in a centrifugal pump","authors":"Jia Liu, Fan Zhang, Mengbin Song, Lufeng Zhu, Desmond Appiah, S. Yuan","doi":"10.1177/09576509231195222","DOIUrl":"https://doi.org/10.1177/09576509231195222","url":null,"abstract":"To reveal the energy loss mechanism of the centrifugal pump, numerical simulation and experimental investigation are conducted to obtain the complex flow field of a single-stage centrifugal pump under various flow conditions. Particular emphasis is focused on the qualitative and quantitative analysis of the distribution and variation characteristics of irreversible loss in the pump model. The results show that the energy loss in the centrifugal pump mainly originates from the entropy generation caused by the turbulent dissipation and wall friction, which are typically generated in the volute and impeller domains. It is worth noticing that the energy loss in the volute is closely associated with non-uniform velocity distribution and the evolution of the shedding vortices from the impeller exit whilst the energy loss in the impeller are greatly affected by unstable flow phenomena such as flow separation, backflow, and jet-wake pattern. At the overload operating conditions, the wall entropy generation possesses a substantial influence on energy loss, which is mainly related to the wall shear stress. Meanwhile, the influence of the rotor-stator interaction and inflow impacting on the energy loss is enhanced with increasing flows. Finally, the omega method captured the vorticity structures near the tongue at partial flow conditions, thereby, revealing the relationship between the high magnitude of flow loss and the evolution of different scales of strong vorticity sheets.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86830137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The forward-curved multi-blade centrifugal fan, also termed as Sirocco fan, is characterized by its complex characteristics of internal flow within the impeller and volute. Currently most of the fans are designed with modifications or optimizations for certain geometric parameters which could not ensure the well compatibility of flow in the impeller and volute, thus it is difficult to improve the aerodynamic performances of the fans. In this paper, we performed a multi-parameter design of a Sirocco fan with optimizations on the geometric parameters of the impeller and volute. The geometric parameters of the volute were designed based on analysis of the internal flow patterns, and the influence from the impeller is also considered. Optimization on the geometric parameters was carried out using the steepest descent method to improve the static pressure rise and efficiency under the designed flow rate by taking into account the relevance of flow in the impeller and volute. The effect of the parametric optimization is evaluated and analyzed by large-eddy simulation (LES). It was found that the static pressure rise and efficiency of the optimized model increase by 1.8% and 5.0% compared with the baseline model, respectively. The static pressure rise fluctuates in a regularly periodic manner. The optimized model reduces the area of low-pressure recirculating flow at the center of the fan and the separated flow on the suction surface of the blades. The near-wall flow on the volute surface is more stable, and the pressure fluctuation around the volute tongue is reduced. The outflow of the volute exhibits better uniformity than the baseline model.
{"title":"Orthogonal optimization design of a Sirocco fan and numerical analysis on the internal flow characteristics","authors":"Zhengfeng Liu, Zhengdao Wang, Shouhua Du, Hui Yang, Yi-kun Wei, Wei Zhang","doi":"10.1177/09576509231195120","DOIUrl":"https://doi.org/10.1177/09576509231195120","url":null,"abstract":"The forward-curved multi-blade centrifugal fan, also termed as Sirocco fan, is characterized by its complex characteristics of internal flow within the impeller and volute. Currently most of the fans are designed with modifications or optimizations for certain geometric parameters which could not ensure the well compatibility of flow in the impeller and volute, thus it is difficult to improve the aerodynamic performances of the fans. In this paper, we performed a multi-parameter design of a Sirocco fan with optimizations on the geometric parameters of the impeller and volute. The geometric parameters of the volute were designed based on analysis of the internal flow patterns, and the influence from the impeller is also considered. Optimization on the geometric parameters was carried out using the steepest descent method to improve the static pressure rise and efficiency under the designed flow rate by taking into account the relevance of flow in the impeller and volute. The effect of the parametric optimization is evaluated and analyzed by large-eddy simulation (LES). It was found that the static pressure rise and efficiency of the optimized model increase by 1.8% and 5.0% compared with the baseline model, respectively. The static pressure rise fluctuates in a regularly periodic manner. The optimized model reduces the area of low-pressure recirculating flow at the center of the fan and the separated flow on the suction surface of the blades. The near-wall flow on the volute surface is more stable, and the pressure fluctuation around the volute tongue is reduced. The outflow of the volute exhibits better uniformity than the baseline model.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90100167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-10DOI: 10.1177/09576509231193195
Moda Geetha Rani, Rajaraman Rangasamy
Thermal management is a crucial design aspect for the safety and performance of the Lithium-ion battery pack used in electric vehicles. Phase change material (PCM) based battery thermal management is one of the appropriate passive or hybrid thermal management. The present paper highlights the selection of PCM depends on various factors related to application operating conditions like ambient temperature, the heat released by the battery, and the type of battery pack design. In selecting PCM, a thorough understanding of various PCMs requires an overall review of multiple types and properties of organic and inorganic PCM, using phase change equilibrium diagrams to comprehend phase change transformations. Further, the present work summarizes the various studies on PCM durability, different thermal performance enhancement techniques, and methodology for selecting PCM; as a result, assisting the researchers and engineers in choosing the appropriate PCM for the various EV battery thermal management applications in terms of chemical, thermal, and economic aspects
{"title":"Review of phase change material application in thermal management of electric vehicle battery pack","authors":"Moda Geetha Rani, Rajaraman Rangasamy","doi":"10.1177/09576509231193195","DOIUrl":"https://doi.org/10.1177/09576509231193195","url":null,"abstract":"Thermal management is a crucial design aspect for the safety and performance of the Lithium-ion battery pack used in electric vehicles. Phase change material (PCM) based battery thermal management is one of the appropriate passive or hybrid thermal management. The present paper highlights the selection of PCM depends on various factors related to application operating conditions like ambient temperature, the heat released by the battery, and the type of battery pack design. In selecting PCM, a thorough understanding of various PCMs requires an overall review of multiple types and properties of organic and inorganic PCM, using phase change equilibrium diagrams to comprehend phase change transformations. Further, the present work summarizes the various studies on PCM durability, different thermal performance enhancement techniques, and methodology for selecting PCM; as a result, assisting the researchers and engineers in choosing the appropriate PCM for the various EV battery thermal management applications in terms of chemical, thermal, and economic aspects","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90427776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-01DOI: 10.1177/09576509221148231
B. Rawlins, R. Laubscher, P. Rousseau
An integrated data-driven surrogate model and one-dimensional (1-D) process model of a 620 [MWe] utility scale boiler is presented. A robust and computationally inexpensive computational fluid dynamic (CFD) model of the utility boiler was utilized to generate the solution dataset for surrogate model training and testing. Both a standard multi-layer perceptron (MLP) and mixture density network (MDN) machine learning architectures are compared for use as a surrogate model to predict the furnace heat loads and the flue gas inlet conditions to the convective pass. A hyperparameter search was performed to find the best MLP and MDN architecture. The MDN was selected for surrogate model integration since it showed comparable accuracy and provides the ability to predict the associated uncertainties. Validation of the integrated model against plant data was performed for a wide range of loads, and critical results were predicted within 5–8% of the measured results. The validated model was subsequently used to investigate the effects of using a poor-quality fuel for the 100% maximum continuous rating load case. The uncertainties predicted by the surrogate model were propagated through the integrated model using the Monte Carlo technique, adding valuable insight into the operational limits of the power plant and the uncertainties associated with it.
{"title":"An integrated data-driven surrogate model and thermofluid network-based model of a 620 MW e utility-scale boiler","authors":"B. Rawlins, R. Laubscher, P. Rousseau","doi":"10.1177/09576509221148231","DOIUrl":"https://doi.org/10.1177/09576509221148231","url":null,"abstract":"An integrated data-driven surrogate model and one-dimensional (1-D) process model of a 620 [MWe] utility scale boiler is presented. A robust and computationally inexpensive computational fluid dynamic (CFD) model of the utility boiler was utilized to generate the solution dataset for surrogate model training and testing. Both a standard multi-layer perceptron (MLP) and mixture density network (MDN) machine learning architectures are compared for use as a surrogate model to predict the furnace heat loads and the flue gas inlet conditions to the convective pass. A hyperparameter search was performed to find the best MLP and MDN architecture. The MDN was selected for surrogate model integration since it showed comparable accuracy and provides the ability to predict the associated uncertainties. Validation of the integrated model against plant data was performed for a wide range of loads, and critical results were predicted within 5–8% of the measured results. The validated model was subsequently used to investigate the effects of using a poor-quality fuel for the 100% maximum continuous rating load case. The uncertainties predicted by the surrogate model were propagated through the integrated model using the Monte Carlo technique, adding valuable insight into the operational limits of the power plant and the uncertainties associated with it.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78134316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-28DOI: 10.1177/09576509231192140
O. Mohamed
Coal power plants have been a major source of undesirable emissions. Despite the technological advancements in renewable energies, coal units are still in-service in many developed and developing countries due to their reliability, adequacy, and flexibility for power delivery. There are some promising technologies for cleaner operation during power production from coal, including supercritical boiler (SC) design and carbon capture and storage (CCS), however, the challenging in innovating effective methods is still open to expand the boundary of knowledge in this speciality. This paper introduces a novel and simple method for reducing CO2 emissions and improving the dynamic responses of a 600 MW SC coal power plant by Artificial Neural Network (ANN) technique. A wide-range data-driven feedforward ANN model has been identified and verified for the various operations recorded as closed-loop data-sets, which covers all situations of startup, once-through mode, and even emergency shutdown of the unit. The closed-loop SC plant model has been augmented with an inverse multivariable coordinate NN controller, developed by analogous learning algorithm to improve the plant automation. With precisely selected setpoints, as operational rules, of temperature, pressure, and earliest possible power demand signals, the automated SC plant has been capable to operate with lower coal consumption - and thus lower emissions – than the existing operation strategy during startup, normal operation, and emergency shutdown modes. The improvement in dynamic responses have been quantified through simulations with comparison with existing performance, which have resulted in an overall average reduction of 2.143 Kg/s in coal consumption.
{"title":"Reduction of emissions and improvement of dynamic responses of a supercritical clean coal generation unit via neural network inverse control strategy","authors":"O. Mohamed","doi":"10.1177/09576509231192140","DOIUrl":"https://doi.org/10.1177/09576509231192140","url":null,"abstract":"Coal power plants have been a major source of undesirable emissions. Despite the technological advancements in renewable energies, coal units are still in-service in many developed and developing countries due to their reliability, adequacy, and flexibility for power delivery. There are some promising technologies for cleaner operation during power production from coal, including supercritical boiler (SC) design and carbon capture and storage (CCS), however, the challenging in innovating effective methods is still open to expand the boundary of knowledge in this speciality. This paper introduces a novel and simple method for reducing CO2 emissions and improving the dynamic responses of a 600 MW SC coal power plant by Artificial Neural Network (ANN) technique. A wide-range data-driven feedforward ANN model has been identified and verified for the various operations recorded as closed-loop data-sets, which covers all situations of startup, once-through mode, and even emergency shutdown of the unit. The closed-loop SC plant model has been augmented with an inverse multivariable coordinate NN controller, developed by analogous learning algorithm to improve the plant automation. With precisely selected setpoints, as operational rules, of temperature, pressure, and earliest possible power demand signals, the automated SC plant has been capable to operate with lower coal consumption - and thus lower emissions – than the existing operation strategy during startup, normal operation, and emergency shutdown modes. The improvement in dynamic responses have been quantified through simulations with comparison with existing performance, which have resulted in an overall average reduction of 2.143 Kg/s in coal consumption.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89200841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-15DOI: 10.1177/09576509231188554
Yongxue Zhang, Zhihao Wang, Bohui Lu, Mengxi Luo
The installation of fins offers an effective solution for addressing the poor thermal conductivity of phase change materials (PCMs) in latent heat thermal energy storage (LHTES) systems. This paper aims to investigate the combined effects of unequal fin length arrangements and the inclination angle of fins on the performance of an LHTES system during the charging process. The LHTES system consists of a cylindrical container filled with paraffin (RT55) serving as the PCM. Numerical models are established and validated, followed by simulating various fin structures to analyze the complete melting time of the PCM. The characteristics of the melting process are further examined in four representative cases, including the full melting time, evolution of the melt fraction, average maximum velocity, streamline contours, temperature uniformity, and average Nusselt number. The results reveal that the optimal case, featuring unequal length and downward annular fins, achieves a significant 49.8% reduction in the complete melting time of the PCM compared to the benchmark case with ordinary annular fins. Moreover, the optimal configuration increases the largest average maximum velocity of the PCM by 35.36%, resulting in a more uniform temperature distribution and a higher Nusselt number.
{"title":"Effect of fin length and angle on the melting process of phase change materials in vertical latent heat storage unit","authors":"Yongxue Zhang, Zhihao Wang, Bohui Lu, Mengxi Luo","doi":"10.1177/09576509231188554","DOIUrl":"https://doi.org/10.1177/09576509231188554","url":null,"abstract":"The installation of fins offers an effective solution for addressing the poor thermal conductivity of phase change materials (PCMs) in latent heat thermal energy storage (LHTES) systems. This paper aims to investigate the combined effects of unequal fin length arrangements and the inclination angle of fins on the performance of an LHTES system during the charging process. The LHTES system consists of a cylindrical container filled with paraffin (RT55) serving as the PCM. Numerical models are established and validated, followed by simulating various fin structures to analyze the complete melting time of the PCM. The characteristics of the melting process are further examined in four representative cases, including the full melting time, evolution of the melt fraction, average maximum velocity, streamline contours, temperature uniformity, and average Nusselt number. The results reveal that the optimal case, featuring unequal length and downward annular fins, achieves a significant 49.8% reduction in the complete melting time of the PCM compared to the benchmark case with ordinary annular fins. Moreover, the optimal configuration increases the largest average maximum velocity of the PCM by 35.36%, resulting in a more uniform temperature distribution and a higher Nusselt number.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139358987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-14DOI: 10.1177/09576509231189774
Abdelbasset Lachraf, Mohamed Si Ameur
In this numerical study, the impact of equidistant trapezoidal ribs on the characteristics of premixed H2-air micro-combustion was investigated, with a specific focus on the rib height. The study comprehensively examined flame structure, flame front position, flame speed, and combustion efficiency. A comparative analysis was performed between a backward-facing step micro combustor (MCSD) and micro combustors with varying rib heights: MCRD1 (0.5 mm), MCRD2 (0.6 mm), and MCRD3 (0.7 mm). The incorporation of trapezoidal ribs resulted in the creation of elongated and evenly distributed recirculation zones, significantly enhancing mixing and promoting flame stability, particularly at higher rib heights. The recirculation zones played a critical role in influencing the chemical reaction rate and the species distribution, leading to higher flame speed and greater combustion intensity. The findings highlight the outcomes of incorporating ribs in terms of combustion efficiency. The combustion efficiency values for MCRD1, MCRD2, and MCRD3 were recorded as 96.95%, 96.75%, and 96.61%, respectively, while the MCSD had a combustion efficiency of 97.14%. Hence, the recommended range of rib height is considered advantageous in ensuring an optimal balance between improved flame stabilization and maintaining a satisfactory level of combustion efficiency. The findings provide valuable insights for optimizing micro-thermophotovoltaic systems.
{"title":"Numerical investigation of H2/Air fueled micro combustion characteristics with trapezoidal ribs for micro thermophotovoltaic applications: Effect of rib height","authors":"Abdelbasset Lachraf, Mohamed Si Ameur","doi":"10.1177/09576509231189774","DOIUrl":"https://doi.org/10.1177/09576509231189774","url":null,"abstract":"In this numerical study, the impact of equidistant trapezoidal ribs on the characteristics of premixed H2-air micro-combustion was investigated, with a specific focus on the rib height. The study comprehensively examined flame structure, flame front position, flame speed, and combustion efficiency. A comparative analysis was performed between a backward-facing step micro combustor (MCSD) and micro combustors with varying rib heights: MCRD1 (0.5 mm), MCRD2 (0.6 mm), and MCRD3 (0.7 mm). The incorporation of trapezoidal ribs resulted in the creation of elongated and evenly distributed recirculation zones, significantly enhancing mixing and promoting flame stability, particularly at higher rib heights. The recirculation zones played a critical role in influencing the chemical reaction rate and the species distribution, leading to higher flame speed and greater combustion intensity. The findings highlight the outcomes of incorporating ribs in terms of combustion efficiency. The combustion efficiency values for MCRD1, MCRD2, and MCRD3 were recorded as 96.95%, 96.75%, and 96.61%, respectively, while the MCSD had a combustion efficiency of 97.14%. Hence, the recommended range of rib height is considered advantageous in ensuring an optimal balance between improved flame stabilization and maintaining a satisfactory level of combustion efficiency. The findings provide valuable insights for optimizing micro-thermophotovoltaic systems.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139359315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-10DOI: 10.1177/09576509231188812
Tawfiq Al-Mughanam, A. Khaliq
A significant part of energy of fuel supplied is lost in internal combustion engines in the form of atmospheric discharge of engine exhaust gases which are considered as a big source of engine inefficiency and formation of pollutant emissions. To address this issue, a bottoming cycle combining the transcritical CO2 (T-CO2) refrigeration cycle and the supercritical CO2 (sCO2) power cycle is employed, aiming to produce cooling for food preservation by utilizing the exhaust heat of homogeneous charge compression ignition (HCCI) engine powering the refrigerated truck. The operative variables and their effect on thermal and exergetic efficiency of HCCI engine and the combined system are investigated. At the base case operative conditions, the thermal and exergy efficiencies of natural gas fueled HCCI engine are improved significantly from 48.69% to 61.28% and from 41.14% to 42.79%, respectively, after employing the sCO2 powered T-CO2 refrigeration cycle. Promotion of equivalence ratio from 0.3 to 0.9 enhances the thermal and exergy efficiencies of HCCI engine from 47.44% to 49.54% and from 40.14% to 42.12%, respectively. Increasing of engine speed from 1400 r.p.m to 2200 r.p.m provides marginal improvement in HCCI engine efficiencies but the efficiencies of combined cycle are significantly improved from 57.67% to 65.18% and from 40.64% to 45.06%, respectively. Finally, exergy analysis applied to determine the sources of non-idealities within the system revealed that out 361 kW (100%) fuel exergy supplied to the system, HCCI engine destroys 93.31 kW (25.85%), catalytic convertor destroys15.49 kW (4.29%), and the in-cylinder heat transfer losses and system exhaust losses are found as 35.72 kW (9.91%) and 16.61 kW (4.61%), respectively.
{"title":"Investigation on novel natural gas fueled homogeneous charge compression ignition engine based combined power and cooling system","authors":"Tawfiq Al-Mughanam, A. Khaliq","doi":"10.1177/09576509231188812","DOIUrl":"https://doi.org/10.1177/09576509231188812","url":null,"abstract":"A significant part of energy of fuel supplied is lost in internal combustion engines in the form of atmospheric discharge of engine exhaust gases which are considered as a big source of engine inefficiency and formation of pollutant emissions. To address this issue, a bottoming cycle combining the transcritical CO2 (T-CO2) refrigeration cycle and the supercritical CO2 (sCO2) power cycle is employed, aiming to produce cooling for food preservation by utilizing the exhaust heat of homogeneous charge compression ignition (HCCI) engine powering the refrigerated truck. The operative variables and their effect on thermal and exergetic efficiency of HCCI engine and the combined system are investigated. At the base case operative conditions, the thermal and exergy efficiencies of natural gas fueled HCCI engine are improved significantly from 48.69% to 61.28% and from 41.14% to 42.79%, respectively, after employing the sCO2 powered T-CO2 refrigeration cycle. Promotion of equivalence ratio from 0.3 to 0.9 enhances the thermal and exergy efficiencies of HCCI engine from 47.44% to 49.54% and from 40.14% to 42.12%, respectively. Increasing of engine speed from 1400 r.p.m to 2200 r.p.m provides marginal improvement in HCCI engine efficiencies but the efficiencies of combined cycle are significantly improved from 57.67% to 65.18% and from 40.64% to 45.06%, respectively. Finally, exergy analysis applied to determine the sources of non-idealities within the system revealed that out 361 kW (100%) fuel exergy supplied to the system, HCCI engine destroys 93.31 kW (25.85%), catalytic convertor destroys15.49 kW (4.29%), and the in-cylinder heat transfer losses and system exhaust losses are found as 35.72 kW (9.91%) and 16.61 kW (4.61%), respectively.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89351174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-10DOI: 10.1177/09576509231188183
Liuxi Cai, Jiawei Yao, Y. Hou, Shunsen Wang, Yun Li, Z. Feng
To more accurately understand and predict the deposition behavior of catalyst particles in the flue gas turbine cascade, test and numerical combined study is performed in this paper. Based on the systematic analysis of the deposition process and physical mechanism of the catalyst particles, the traditional DRW model, critical velocity particle deposition model and removal model were corrected with the user defined function custom function and validated with the actual deposition morphology. On this basis, the effects of the particle Stokes number and flue gas parameters on the particle deposition characteristics of the flue gas turbine cascade were detailed investigated. The results show that the revised DRW model, critical velocity and removal model can more accurately predict the deposition location and deposition rate of particles in the turbine cascade. With the increase in the Stokes number of particles, the average particle impact rate on the blade surface gradually increased, while the average deposition rate showed a trend of first increasing and then decreasing. The average deposition rate of particles in the rotor blade surface is roughly twice as high as that in the stator surface. With the increase of the flue gas expansion ratio, the deposition rate of particles less than 3 μm gradually increases, while the deposition rate of particles greater than 3 μm tends to decrease. In addition, the change in the flue gas expansion ratio has no obvious effect on the particle deposition distribution in different size ranges.
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