A kipufogó- és hangtompító zaj egy kihívást jelentő probléma a gépjárműiparban. Noha a rendszer fő célja a motorból származó akusztikus impulzusok intenzitásának csökkentése, az ilyen rendszerek által kiváltott ellennyomást a lehető legkisebbre kell csökkenteni, hogy garantálják a motor maximális teljesítményét. Ez a tanulmány egy hatékony eljárást mutat be egy Formula Student versenyautó (FS) reaktív hangtompítója átviteli veszteségének optimalizálására analitikai módszerek alkalmazásával. Ennek során létrehoztuk a hangtompító CAD modelljét, majd ezt az AVL BOOST-ban és más fejlett kereskedelmi forgalomban elérhető tervező szoftver (SolidWorks 2017) segítségével egy végeselemes akusztikai (FEA) modellé alakítottuk. A modell segítségével az áramlási tulajdonságokat, a nyomást és a sebességet vizsgáltuk. A modell ellenőrzése után elvégeztük a tervezési paraméterek érzékenységvizsgálatát a hangtompító hangnyomásszintjének (SPL) optimalizálása érdekében. Javaslatokat tettünk egy egyenletesebb SPL görbe elérésére.
Investigation of fracture behavior and mechanical properties of epoxy composi...Barhm Mohamad
Adding of a multi-walled carbon nanotubes (MWCNTs) to epoxy resin has shown
promising results in improving fracture toughness in bulk epoxy and carbon fiber-reinforced
epoxy composites (CFRP). using a hand layup proceeding followed by the so called vacuum
bagging process method, carbon fiber-reinforced polymer multi-wall carbon nanotubes
(MWCNTs) was added to an epoxy resin with a weight percentage mixing of 1% wt., 1.25% wt.,
and 1.5 % wt. MWCNTs. Furthermore, the specimen underwent analysis via Fourier-Transform
Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) spectroscopy, the composites were
subjected to a microscopic examination using a Scanning Electron Microscope (SEM). FTIR and
XRD verified the folding and unfolding of the polymer, in addition, the mechanical properties
including tensile strength, bending stress, and impact behavior were investigated as well as the
hardness test. The obtained results showed a significant improvement of about (40 %) in tensile
strength, (53 %) in bending stress at 1 % wt. MWCNTs, and (70 %) percentage increment in the
strength of Impact at 1.25 % wt. MWCNTs. And the gained hardness was about 40.5 HV which
were compared with a reference substance named Carbon Fiber (CF) without any addition of nano
materials. Carbon nanotubes have demonstrated their potential to enhance the mechanical
properties of fiber-reinforced polymers, so this investigative study employs comprehensive
characterization techniques, and demonstrates significant improvements in mechanical properties
for the modified polymeric composite materials supported with nano materials.
Characterization of a flat plate solar water heating system using different n...Barhm Mohamad
Flat-plate solar collectors (FPSCs) are the most effective and environmentally friendly heating systems available. They are frequently used to convert solar radiation into usable heat for a variety of thermal applications. Because of their superior thermo-physical features, the use of Nano-fluids in FPSCs is a useful technique to improve FPSC performance. Nano-fluids are advanced colloidal suspensions containing Nano-sized particles that have been researched over the last two decades and identified a fluid composed of strong nanoparticles with a diameter of smaller than (100 nm). These micro-particles aid in improving the thermal conductivity and convective heat transfer of liquids when mixed with the base fluid. The current study provides an in-depth review of the scientific advances in the field of Nano-fluids on flat-plate solar collectors. Previous research on the usage of Nano-fluids in FPSCs shows that Nano-fluids can be used successfully to improve the efficiency of flat-plate collectors. Though several Nano-fluids have been reviewed as solar collector operatin fluids. Nano-fluids have greater pressure drops than liquids, and their pressure drops andhence pumping power rise as the volume flow rate increases. Additionally, the article discusses the concept of Nano-fluids, the different forms of nanoparticles, the methods for preparing Nano-fluids, and their thermos-physical properties. The article concludes with a few observations and suggestions on the usage of Nano-fluids in flat-plate solar collectors. This article summarizes the numerous research studies conducted in this region, which may prove useful for future experimental studies.
A review of aerodynamic analysis of commercial automotive-materials and methodsBarhm Mohamad
This paper explores the role of the computational fluid dynamics (CFD) modeling technique in the aerodynamic design and propulsion system of the formula 1 car. It provides a study of Reynolds number influences on the state of the boundary layer, unstable and steady flow, time-dependent wake structure, interacting shear layer and separate flows through literature review. As pointed out in is paper, the aerodynamics analysis is conducted to decrease the drag force. Using the computational fluid dynamics (CFD) tools, the analysis was carried out. The major objective of this review article will be to increase the car stability and reduce drag. The efficiency of the track would also increase the air resistance of the vehicle. The ideas of dimensional analysis and uniformity of flows are used to demonstrate that commercial ground cars' aerodynamics are only dependent on the transitional and trans-critical flow regimes.
Book of Abstracts from 9th International Scientific Conference on Advances in...Barhm Mohamad
This document provides an overview of the 9th International Scientific Conference on Advances in Mechanical Engineering held in Debrecen, Hungary. It includes the welcome message from the conference chair, Tamás Mankovits, as well as information about the conference committees, program, and 202 attendees from 12 countries. The conference included 110 presentations and 49 posters on topics related to mechanical engineering. The theme of the plenary lectures was artificial intelligence and material testing. The conference also included a MATLAB workshop and an exhibition of creative mechanical engineers.
A REVIEW OF AERODYNAMIC ANALYSIS OF COMMERCIAL AUTOMOTIVE-MATERIALS AND METHODS Barhm Mohamad
This paper explores the role of the computational fluid dynamics (CFD) modeling technique in the aerodynamic design and propulsion system of the formula 1 car. It provides a study of Reynolds number influences on the state of the boundary layer, unstable and steady flow, time-dependent wake structure, interacting shear layer and separate flows through literature review. As pointed out in is paper, the aerodynamics analysis is conducted to decrease the drag force. Using the computational fluid dynamics (CFD) tools, the analysis was carried out. The major objective of this review article will be to increase the car stability and reduce drag. The efficiency of the track would also increase the air resistance of the vehicle. The ideas of dimensional analysis and uniformity of flows are used to demonstrate that commercial ground cars' aerodynamics are only dependent on the transitional and trans-critical flow regimes.
An Experimental Artificial Neural Network Model: Investigating and Predicting...Barhm Mohamad
The present study establishes a new estimation model using an artificial neural network (ANN) to predict the mechanical properties of the AISI 1035 alloy. The experiments were designed based on the L16 orthogonal array of the Taguchi method. A proposed numerical model for predicting the correlation of mechanical properties was supplemented with experimental data. The quenching process was conducted using a cooling medium called “nanofluids”. Nanoparticles were dissolved in a liquid phase at various concentrations (0.5, 1, 2.5, and 5 % vf) to prepare the nanofluids. Experimental investigations were done to assess the impact of temperature, base fluid, volume fraction, and soaking time on the mechanical properties. The outcomes showed that all conditions led to a noticeable improvement in the alloy's hardness which reached 100%, the grain size was refined about 80%, and unwanted residual stresses were removed from 50 to 150 MPa. Adding 5% of CuO nanoparticles to oil led to the best grain size refinement, while adding 2.5% of Al2O3 nanoparticles to engine oil resulted in the greatest compressive residual stress. The experimental variables were used as the input data for the established numerical ANN model, and the mechanical properties were the output. Upwards of 99% of the training network's correlations seemed to be positive. The estimated result, nevertheless, matched the experimental dataset exactly. Thus, the ANN model is an effective tool for reflecting the effects of quenching conditions on the mechanical properties of AISI 1035.
Experimental study of nano-composite materials on vibration responsesBarhm Mohamad
This paper present of experimental and numerical study of nano Al2O3 cantilever beam for forced vibration, addressing an unexplored area in the existing literature. The proposed nano composite cantilever beam is modeled with hole and crack. The study is based on history loading calculation and composite morphology a global parameter, the transverse crack in nano composite cantilever beam was studied and analyzed experimentally using a four-channel dynamic signal acquisition (NI 9234) module for making high-accuracy measurements and its ideal for vibration applications. The relationship between the dispersion and interaction of the alumina nanoparticles within the cantilever beam and morphology of the solid, hole and crack composite has been identified. Furthermore, the influence of particles Al2O3 at different concentrations (0%, 1%, 3% and 4%) have been studied respectively. Supporting results proved that the crack and hole depth increases with increases of history loading. Nanoparticles dispersed within the specimen can increase energy dissipation during vibration, leading to improved damping characteristics. For future work, it is recommended to utilize statistical frequency domain input, such as Power Spectral Density (PSD), for assessing the structural response instead of employing time history loading.
Entropy generation and heat transfer rate for MHD forced convection of nanoli...Barhm Mohamad
This document summarizes a numerical study that investigates magnetohydrodynamic forced convection of nanofluid in a rectangular channel with an extended surface and three cylindrical blocks. The study examines the effects of Reynolds number, Hartmann number, Eckert number, and nanoparticle volume fraction on temperature distribution, stream function, entropy generation, and mean Nusselt number. Governing equations for steady, incompressible, laminar, two-dimensional flow are presented. Thermophysical properties of water, copper nanoparticles, and the nanofluid are provided.
Investigation of fracture behavior and mechanical properties of epoxy composi...Barhm Mohamad
Adding of a multi-walled carbon nanotubes (MWCNTs) to epoxy resin has shown
promising results in improving fracture toughness in bulk epoxy and carbon fiber-reinforced
epoxy composites (CFRP). using a hand layup proceeding followed by the so called vacuum
bagging process method, carbon fiber-reinforced polymer multi-wall carbon nanotubes
(MWCNTs) was added to an epoxy resin with a weight percentage mixing of 1% wt., 1.25% wt.,
and 1.5 % wt. MWCNTs. Furthermore, the specimen underwent analysis via Fourier-Transform
Infrared (FTIR) spectroscopy, and X-ray Diffraction (XRD) spectroscopy, the composites were
subjected to a microscopic examination using a Scanning Electron Microscope (SEM). FTIR and
XRD verified the folding and unfolding of the polymer, in addition, the mechanical properties
including tensile strength, bending stress, and impact behavior were investigated as well as the
hardness test. The obtained results showed a significant improvement of about (40 %) in tensile
strength, (53 %) in bending stress at 1 % wt. MWCNTs, and (70 %) percentage increment in the
strength of Impact at 1.25 % wt. MWCNTs. And the gained hardness was about 40.5 HV which
were compared with a reference substance named Carbon Fiber (CF) without any addition of nano
materials. Carbon nanotubes have demonstrated their potential to enhance the mechanical
properties of fiber-reinforced polymers, so this investigative study employs comprehensive
characterization techniques, and demonstrates significant improvements in mechanical properties
for the modified polymeric composite materials supported with nano materials.
Characterization of a flat plate solar water heating system using different n...Barhm Mohamad
Flat-plate solar collectors (FPSCs) are the most effective and environmentally friendly heating systems available. They are frequently used to convert solar radiation into usable heat for a variety of thermal applications. Because of their superior thermo-physical features, the use of Nano-fluids in FPSCs is a useful technique to improve FPSC performance. Nano-fluids are advanced colloidal suspensions containing Nano-sized particles that have been researched over the last two decades and identified a fluid composed of strong nanoparticles with a diameter of smaller than (100 nm). These micro-particles aid in improving the thermal conductivity and convective heat transfer of liquids when mixed with the base fluid. The current study provides an in-depth review of the scientific advances in the field of Nano-fluids on flat-plate solar collectors. Previous research on the usage of Nano-fluids in FPSCs shows that Nano-fluids can be used successfully to improve the efficiency of flat-plate collectors. Though several Nano-fluids have been reviewed as solar collector operatin fluids. Nano-fluids have greater pressure drops than liquids, and their pressure drops andhence pumping power rise as the volume flow rate increases. Additionally, the article discusses the concept of Nano-fluids, the different forms of nanoparticles, the methods for preparing Nano-fluids, and their thermos-physical properties. The article concludes with a few observations and suggestions on the usage of Nano-fluids in flat-plate solar collectors. This article summarizes the numerous research studies conducted in this region, which may prove useful for future experimental studies.
A review of aerodynamic analysis of commercial automotive-materials and methodsBarhm Mohamad
This paper explores the role of the computational fluid dynamics (CFD) modeling technique in the aerodynamic design and propulsion system of the formula 1 car. It provides a study of Reynolds number influences on the state of the boundary layer, unstable and steady flow, time-dependent wake structure, interacting shear layer and separate flows through literature review. As pointed out in is paper, the aerodynamics analysis is conducted to decrease the drag force. Using the computational fluid dynamics (CFD) tools, the analysis was carried out. The major objective of this review article will be to increase the car stability and reduce drag. The efficiency of the track would also increase the air resistance of the vehicle. The ideas of dimensional analysis and uniformity of flows are used to demonstrate that commercial ground cars' aerodynamics are only dependent on the transitional and trans-critical flow regimes.
Book of Abstracts from 9th International Scientific Conference on Advances in...Barhm Mohamad
This document provides an overview of the 9th International Scientific Conference on Advances in Mechanical Engineering held in Debrecen, Hungary. It includes the welcome message from the conference chair, Tamás Mankovits, as well as information about the conference committees, program, and 202 attendees from 12 countries. The conference included 110 presentations and 49 posters on topics related to mechanical engineering. The theme of the plenary lectures was artificial intelligence and material testing. The conference also included a MATLAB workshop and an exhibition of creative mechanical engineers.
A REVIEW OF AERODYNAMIC ANALYSIS OF COMMERCIAL AUTOMOTIVE-MATERIALS AND METHODS Barhm Mohamad
This paper explores the role of the computational fluid dynamics (CFD) modeling technique in the aerodynamic design and propulsion system of the formula 1 car. It provides a study of Reynolds number influences on the state of the boundary layer, unstable and steady flow, time-dependent wake structure, interacting shear layer and separate flows through literature review. As pointed out in is paper, the aerodynamics analysis is conducted to decrease the drag force. Using the computational fluid dynamics (CFD) tools, the analysis was carried out. The major objective of this review article will be to increase the car stability and reduce drag. The efficiency of the track would also increase the air resistance of the vehicle. The ideas of dimensional analysis and uniformity of flows are used to demonstrate that commercial ground cars' aerodynamics are only dependent on the transitional and trans-critical flow regimes.
An Experimental Artificial Neural Network Model: Investigating and Predicting...Barhm Mohamad
The present study establishes a new estimation model using an artificial neural network (ANN) to predict the mechanical properties of the AISI 1035 alloy. The experiments were designed based on the L16 orthogonal array of the Taguchi method. A proposed numerical model for predicting the correlation of mechanical properties was supplemented with experimental data. The quenching process was conducted using a cooling medium called “nanofluids”. Nanoparticles were dissolved in a liquid phase at various concentrations (0.5, 1, 2.5, and 5 % vf) to prepare the nanofluids. Experimental investigations were done to assess the impact of temperature, base fluid, volume fraction, and soaking time on the mechanical properties. The outcomes showed that all conditions led to a noticeable improvement in the alloy's hardness which reached 100%, the grain size was refined about 80%, and unwanted residual stresses were removed from 50 to 150 MPa. Adding 5% of CuO nanoparticles to oil led to the best grain size refinement, while adding 2.5% of Al2O3 nanoparticles to engine oil resulted in the greatest compressive residual stress. The experimental variables were used as the input data for the established numerical ANN model, and the mechanical properties were the output. Upwards of 99% of the training network's correlations seemed to be positive. The estimated result, nevertheless, matched the experimental dataset exactly. Thus, the ANN model is an effective tool for reflecting the effects of quenching conditions on the mechanical properties of AISI 1035.
Experimental study of nano-composite materials on vibration responsesBarhm Mohamad
This paper present of experimental and numerical study of nano Al2O3 cantilever beam for forced vibration, addressing an unexplored area in the existing literature. The proposed nano composite cantilever beam is modeled with hole and crack. The study is based on history loading calculation and composite morphology a global parameter, the transverse crack in nano composite cantilever beam was studied and analyzed experimentally using a four-channel dynamic signal acquisition (NI 9234) module for making high-accuracy measurements and its ideal for vibration applications. The relationship between the dispersion and interaction of the alumina nanoparticles within the cantilever beam and morphology of the solid, hole and crack composite has been identified. Furthermore, the influence of particles Al2O3 at different concentrations (0%, 1%, 3% and 4%) have been studied respectively. Supporting results proved that the crack and hole depth increases with increases of history loading. Nanoparticles dispersed within the specimen can increase energy dissipation during vibration, leading to improved damping characteristics. For future work, it is recommended to utilize statistical frequency domain input, such as Power Spectral Density (PSD), for assessing the structural response instead of employing time history loading.
Entropy generation and heat transfer rate for MHD forced convection of nanoli...Barhm Mohamad
This document summarizes a numerical study that investigates magnetohydrodynamic forced convection of nanofluid in a rectangular channel with an extended surface and three cylindrical blocks. The study examines the effects of Reynolds number, Hartmann number, Eckert number, and nanoparticle volume fraction on temperature distribution, stream function, entropy generation, and mean Nusselt number. Governing equations for steady, incompressible, laminar, two-dimensional flow are presented. Thermophysical properties of water, copper nanoparticles, and the nanofluid are provided.
ANALYSIS OF THE MECHANICAL CHARACTERISTICS OF DATE SEED POWDER-BASED COMPOSIT...Barhm Mohamad
The document analyzes the mechanical properties of carbon fiber-reinforced epoxy (CFRE) composites reinforced with different weight percentages of date seed powder granules (DSGP). Tensile, flexural, impact, and hardness tests were performed on CFRE composites with 0%, 15%, 25%, and 35% DSGP. The results showed that the 15% DSGP composite had the highest breaking force in tensile testing. The 35% DSGP composite had the highest maximum bending force in flexural testing. The 25% DSGP composite had the highest energy absorption capacity in impact testing and hardness. Overall, the optimal composition for mechanical properties was found to be 15-25% DSGP.
Thermodynamic analysis and optimization of flat plate solar collector using T...Barhm Mohamad
Solar energy's efficiency and environmental benefits attract academics. In Kirkuk, Iraq, the thermal efficiency, exergy, and entropy of solar collectors were calculated. The experiment involved two glass-topped collectors, fluid transfer tubes, and aluminum heat-absorbing plates. Glass wool insulation minimized heat loss. A 0.5% TiO2/Water nanofluid was created using a mechanical and ultrasonic stirrer. Results showed that solar radiation increased thermal efficiency until midday, reaching 48.48% for water and 51.23% for the nanofluid. With increasing mass flow rates from 0.0045 kg/s to 0.02 kg/s, thermal efficiency improved from 16.26% to 47.37% for water and from 20.65% to 48.76% for the nanofluid. Filtered water provided 380W and 395W of energy in March and April, while the nanofluid increased it to 395W and 415W during these months. Mass flow generated energy, and the Reynolds number raised entropy. The noon exergy efficiency for nanofluids was 50-55%, compared to 30% for water. At noon, the broken exergy measured 877.53 Watts for the nanofluid and 880.12 Watts for water. In Kirkuk, Iraq, the 0.5% TiO2/Water nanofluid outperformed water in solar collectors.
MODELLING AND TESTING OF ADVANCED INTAKE AND EXHAUST SYSTEM COMPONENTS FOR RA...Barhm Mohamad
In this research, it hasibeen shownithat the gas flow iniintake system effects on the FS
engineiperformance and acousticibehaviour. The proposedicalculationimethodsiare tested
numericallyiand byimeasurements. The team fromiUniversity of Miskolc improvedithe
car’s air intakeisystem usingi1D-AVL Boostiwithinithe parametric Fireisoftware
Workbenchienvironment. FS regulationsilimit the minimumidiameter of the restrictor to
20 mm, whichiregulatesithe maximumiintake mass flowirate. The plenum, downstreamiof
theirestrictor, directly influencesithe amount of freshiair reaching theicylinders. A plenum
that isitooilargeicausesithe motorito reactitoo slowlyito the acceleratoriand, in combination
withishortisuctionipipes, triggersithe engine to developisufficientitorqueionly atihigh
rotationispeeds. A too small plenumibehaves oppositely. Usingithe equationifor the intake
runnerilength, the lengthiof the idealirunner was determinedito be approximatelyi 250 mm
andiwith aidiameteriof 32 mm. Hence,idesign II of FormulaiStudent Racingi is aibetteri
choice.
Several calculation techniques were done to calculate transmission loss in different cases
for the muffler, white planewaveipropagationiwas applied from generator using two-load
method for transmission loss result validation of muffler. Theseican beiconsideredias an
accurateicheckiof theianalysisicarried out in thisiwork. It is worthipointingioutithatithis
workimayialso serve as aibenchmarkisolutioniforiapproximateiand numericalitechniques
used foridealing withihybrid muffleriproblems.
REMAPPING AND SIMULATION OF EFI SYSTEM FOR SI ENGINE USING PIGGYBACK ECUBarhm Mohamad
The document describes remapping and simulating the electronic fuel injection (EFI) system of a BMW engine using a piggyback ECU. An experimental EFI system was reconstructed using a piggyback ECU and the control algorithms were simulated in LabVIEW. The simulation results were compared to experimental results for different engine loads and speeds. The piggyback ECU evaluation showed it can independently control fuel dose without depending on the factory ECU, with advantages of low cost and easy installation compared to remapping the factory ECU.
Evaluation of Shell and Tube Heat Exchanger Performance by Using ZnO/Water Na...Barhm Mohamad
To examine and investigate the impact of nanofluid on heat exchanger performance, including the total heat transfer, the effect of friction factor, the average Nusselt number, and the thermal efficiency, the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically. The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021. The nanoparticles volume fractions adopted are 0.2% and 0.35% that used in numerical computations under 200 to 1400 Reynolds numbers range. The increasing of temperature is approximately 13% from the bottom to the top of heat exchanger, while the maximum enhancement of Nusselt number is about 10%, 19% for volume fractions 0.2% and 0.35% respectively. The elevated values of the friction factor at the volumetric ratios of 0.2% and 0.35% are 0.25% and 0.47% respectively. The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.
Enhancement of Double-Pipe Heat Exchanger Effectiveness by Using Porous Media...Barhm Mohamad
This document summarizes a study that investigated heat transfer enhancement in a double-pipe heat exchanger using porous media and TiO2 nanofluid. The study used steel balls as porous media packed in the inner pipe and TiO2-water nanofluid flowing through the inner pipe at various flow rates and nanoparticle volume fractions. Hot water flowed through the outer pipe. Results showed that using porous media and a 0.003 TiO2 nanofluid volume fraction improved heat transfer by 35.4% and improved effectiveness and NTU by 24% and 12.4%, respectively, compared to using just water. The porous media increased surface area for contact while the nanofluid improved thermophysical properties. Optimal design of porous media and nanofluid parameters can
In many cases, the drying of mater
ials is the fina l operation i n manufac turing process
carried out immediately prior to pack ag ing and dispatch . Drying refer s to final
removal o f water, and the operation follow s e vapo ration , filtration or crystallization .
Gas absorption in packed tower with Raschig rings packingsBarhm Mohamad
Gas absorption is mass transfer operation where one or more species is removed from
a gaseous stream by dissoluti on in a l iquid. Packed tower with Raschig Rings
packings is used in the experiment The component that is extracted from the gaseous
stream is known as solute and the component that extracting the solute is known as
solvent. Packed column is one of the com m only use d gas absorption equipment.
Packed column can be operated in co current as well as counter currently.
Counter current flow is preferable since the contact time between the liquid and gas is
greater. This equipment usually consists of a cylindrical column c ontaining a gas inlet
and distributing space at the bottom, a liquid inlet and a packing or filing in the tower.
Estimate the evaporation rate of water (water loss) for the cooling towerBarhm Mohamad
This document describes an experiment to estimate the evaporation rate of water in a cooling tower. The experiment measures temperatures and flow rates to calculate properties like enthalpy and the tower characteristic. Students are asked to determine evaporation rate, analyze how approach and range vary with conditions, calculate the tower characteristic using different methods, and consider how valid the assumption of negligible evaporation is based on their results. References include sections of Perry's Chemical Engineers' Handbook and papers on computer controlled cooling towers.
There are three modes for heat transfer: convection, conduction, and radiation. The convection heat transfer plays an important role in many industrial applications. The convection heat transfer is usually subdivided into free and forced convection. In the forced convection, the fluid is blown or pumped past the heated surface using a pump or a fan, while in the natural (or free) convection, fluid flow is naturally achieved by buoyancy effects, i.e., density variation in the fluid.
Thermal conductivity is heat flow per second per unit area per unit temperature gradient. Heat conduction / Heat energy is the transferred from the hot end of heat conductor to the cold end consider a cylindrical conductor as shown in fig. 1, where the temperature at T1 is greater than at T2, the heat energy flows from the hotter end at temperature T1 to cooler end at temperature T2.
Temperature Measurements and CalibrationBarhm Mohamad
In a glass thermometer, the relative expansion of a liquid compared to the content of the bulb is measured. The majority of the liquid is in a spherical or cylindrical-shaped bulb that forms the thermometers actual sensing element (1), the bulb opens into the long thin glass capillary tube (2). Practically all liquids can be used in thermometers here a differentiation is made between wetting (organic) and non-wetting liquids (mercury) wetting liquids cause additional errors as the temperature drops, the organic liquids must be colored so that it is visible in the capillary tube and the reading of the temperature made easier. Liquid containers for mercury are larger than for other liquids due to the smaller coefficient of expansion.
1) The document provides an introduction to basic fluid mechanics including the three branches of fluid mechanics: fluid statics, fluid kinematics, and fluid dynamics.
2) It discusses key topics in fluid mechanics including pressure, density, viscosity, Bernoulli's equation, and flow rate. Common fluid mechanics applications are also highlighted such as in mechanical engineering, petroleum engineering, and chemical engineering.
3) Equations for pressure, density, Bernoulli's equation, and the continuity equation are presented along with example problems demonstrating their application. Key concepts such as absolute pressure, gauge pressure, and laminar flow are also explained.
Fluid mechanics is a science in study the fluid of liquids and gases in the cases of silence and movement and the forces acting on them can be divided materials found in nature into two branches.
ANALYSIS OF THE MECHANICAL CHARACTERISTICS OF DATE SEED POWDER-BASED COMPOSIT...Barhm Mohamad
The document analyzes the mechanical properties of carbon fiber-reinforced epoxy (CFRE) composites reinforced with different weight percentages of date seed powder granules (DSGP). Tensile, flexural, impact, and hardness tests were performed on CFRE composites with 0%, 15%, 25%, and 35% DSGP. The results showed that the 15% DSGP composite had the highest breaking force in tensile testing. The 35% DSGP composite had the highest maximum bending force in flexural testing. The 25% DSGP composite had the highest energy absorption capacity in impact testing and hardness. Overall, the optimal composition for mechanical properties was found to be 15-25% DSGP.
Thermodynamic analysis and optimization of flat plate solar collector using T...Barhm Mohamad
Solar energy's efficiency and environmental benefits attract academics. In Kirkuk, Iraq, the thermal efficiency, exergy, and entropy of solar collectors were calculated. The experiment involved two glass-topped collectors, fluid transfer tubes, and aluminum heat-absorbing plates. Glass wool insulation minimized heat loss. A 0.5% TiO2/Water nanofluid was created using a mechanical and ultrasonic stirrer. Results showed that solar radiation increased thermal efficiency until midday, reaching 48.48% for water and 51.23% for the nanofluid. With increasing mass flow rates from 0.0045 kg/s to 0.02 kg/s, thermal efficiency improved from 16.26% to 47.37% for water and from 20.65% to 48.76% for the nanofluid. Filtered water provided 380W and 395W of energy in March and April, while the nanofluid increased it to 395W and 415W during these months. Mass flow generated energy, and the Reynolds number raised entropy. The noon exergy efficiency for nanofluids was 50-55%, compared to 30% for water. At noon, the broken exergy measured 877.53 Watts for the nanofluid and 880.12 Watts for water. In Kirkuk, Iraq, the 0.5% TiO2/Water nanofluid outperformed water in solar collectors.
MODELLING AND TESTING OF ADVANCED INTAKE AND EXHAUST SYSTEM COMPONENTS FOR RA...Barhm Mohamad
In this research, it hasibeen shownithat the gas flow iniintake system effects on the FS
engineiperformance and acousticibehaviour. The proposedicalculationimethodsiare tested
numericallyiand byimeasurements. The team fromiUniversity of Miskolc improvedithe
car’s air intakeisystem usingi1D-AVL Boostiwithinithe parametric Fireisoftware
Workbenchienvironment. FS regulationsilimit the minimumidiameter of the restrictor to
20 mm, whichiregulatesithe maximumiintake mass flowirate. The plenum, downstreamiof
theirestrictor, directly influencesithe amount of freshiair reaching theicylinders. A plenum
that isitooilargeicausesithe motorito reactitoo slowlyito the acceleratoriand, in combination
withishortisuctionipipes, triggersithe engine to developisufficientitorqueionly atihigh
rotationispeeds. A too small plenumibehaves oppositely. Usingithe equationifor the intake
runnerilength, the lengthiof the idealirunner was determinedito be approximatelyi 250 mm
andiwith aidiameteriof 32 mm. Hence,idesign II of FormulaiStudent Racingi is aibetteri
choice.
Several calculation techniques were done to calculate transmission loss in different cases
for the muffler, white planewaveipropagationiwas applied from generator using two-load
method for transmission loss result validation of muffler. Theseican beiconsideredias an
accurateicheckiof theianalysisicarried out in thisiwork. It is worthipointingioutithatithis
workimayialso serve as aibenchmarkisolutioniforiapproximateiand numericalitechniques
used foridealing withihybrid muffleriproblems.
REMAPPING AND SIMULATION OF EFI SYSTEM FOR SI ENGINE USING PIGGYBACK ECUBarhm Mohamad
The document describes remapping and simulating the electronic fuel injection (EFI) system of a BMW engine using a piggyback ECU. An experimental EFI system was reconstructed using a piggyback ECU and the control algorithms were simulated in LabVIEW. The simulation results were compared to experimental results for different engine loads and speeds. The piggyback ECU evaluation showed it can independently control fuel dose without depending on the factory ECU, with advantages of low cost and easy installation compared to remapping the factory ECU.
Evaluation of Shell and Tube Heat Exchanger Performance by Using ZnO/Water Na...Barhm Mohamad
To examine and investigate the impact of nanofluid on heat exchanger performance, including the total heat transfer, the effect of friction factor, the average Nusselt number, and the thermal efficiency, the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically. The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021. The nanoparticles volume fractions adopted are 0.2% and 0.35% that used in numerical computations under 200 to 1400 Reynolds numbers range. The increasing of temperature is approximately 13% from the bottom to the top of heat exchanger, while the maximum enhancement of Nusselt number is about 10%, 19% for volume fractions 0.2% and 0.35% respectively. The elevated values of the friction factor at the volumetric ratios of 0.2% and 0.35% are 0.25% and 0.47% respectively. The findings demonstrate that the performance efficiency of shell and tube heat exchanger is enhanced due to the increase in Nusselt number.
Enhancement of Double-Pipe Heat Exchanger Effectiveness by Using Porous Media...Barhm Mohamad
This document summarizes a study that investigated heat transfer enhancement in a double-pipe heat exchanger using porous media and TiO2 nanofluid. The study used steel balls as porous media packed in the inner pipe and TiO2-water nanofluid flowing through the inner pipe at various flow rates and nanoparticle volume fractions. Hot water flowed through the outer pipe. Results showed that using porous media and a 0.003 TiO2 nanofluid volume fraction improved heat transfer by 35.4% and improved effectiveness and NTU by 24% and 12.4%, respectively, compared to using just water. The porous media increased surface area for contact while the nanofluid improved thermophysical properties. Optimal design of porous media and nanofluid parameters can
In many cases, the drying of mater
ials is the fina l operation i n manufac turing process
carried out immediately prior to pack ag ing and dispatch . Drying refer s to final
removal o f water, and the operation follow s e vapo ration , filtration or crystallization .
Gas absorption in packed tower with Raschig rings packingsBarhm Mohamad
Gas absorption is mass transfer operation where one or more species is removed from
a gaseous stream by dissoluti on in a l iquid. Packed tower with Raschig Rings
packings is used in the experiment The component that is extracted from the gaseous
stream is known as solute and the component that extracting the solute is known as
solvent. Packed column is one of the com m only use d gas absorption equipment.
Packed column can be operated in co current as well as counter currently.
Counter current flow is preferable since the contact time between the liquid and gas is
greater. This equipment usually consists of a cylindrical column c ontaining a gas inlet
and distributing space at the bottom, a liquid inlet and a packing or filing in the tower.
Estimate the evaporation rate of water (water loss) for the cooling towerBarhm Mohamad
This document describes an experiment to estimate the evaporation rate of water in a cooling tower. The experiment measures temperatures and flow rates to calculate properties like enthalpy and the tower characteristic. Students are asked to determine evaporation rate, analyze how approach and range vary with conditions, calculate the tower characteristic using different methods, and consider how valid the assumption of negligible evaporation is based on their results. References include sections of Perry's Chemical Engineers' Handbook and papers on computer controlled cooling towers.
There are three modes for heat transfer: convection, conduction, and radiation. The convection heat transfer plays an important role in many industrial applications. The convection heat transfer is usually subdivided into free and forced convection. In the forced convection, the fluid is blown or pumped past the heated surface using a pump or a fan, while in the natural (or free) convection, fluid flow is naturally achieved by buoyancy effects, i.e., density variation in the fluid.
Thermal conductivity is heat flow per second per unit area per unit temperature gradient. Heat conduction / Heat energy is the transferred from the hot end of heat conductor to the cold end consider a cylindrical conductor as shown in fig. 1, where the temperature at T1 is greater than at T2, the heat energy flows from the hotter end at temperature T1 to cooler end at temperature T2.
Temperature Measurements and CalibrationBarhm Mohamad
In a glass thermometer, the relative expansion of a liquid compared to the content of the bulb is measured. The majority of the liquid is in a spherical or cylindrical-shaped bulb that forms the thermometers actual sensing element (1), the bulb opens into the long thin glass capillary tube (2). Practically all liquids can be used in thermometers here a differentiation is made between wetting (organic) and non-wetting liquids (mercury) wetting liquids cause additional errors as the temperature drops, the organic liquids must be colored so that it is visible in the capillary tube and the reading of the temperature made easier. Liquid containers for mercury are larger than for other liquids due to the smaller coefficient of expansion.
1) The document provides an introduction to basic fluid mechanics including the three branches of fluid mechanics: fluid statics, fluid kinematics, and fluid dynamics.
2) It discusses key topics in fluid mechanics including pressure, density, viscosity, Bernoulli's equation, and flow rate. Common fluid mechanics applications are also highlighted such as in mechanical engineering, petroleum engineering, and chemical engineering.
3) Equations for pressure, density, Bernoulli's equation, and the continuity equation are presented along with example problems demonstrating their application. Key concepts such as absolute pressure, gauge pressure, and laminar flow are also explained.
Fluid mechanics is a science in study the fluid of liquids and gases in the cases of silence and movement and the forces acting on them can be divided materials found in nature into two branches.
1. Multidiszciplináris tudományok, 9. kötet. (2019) 4 sz. pp. 548-555 https://doi.org/10.35925/j.multi.2019.4.58
548
HANGTOMPÍTÓ AKUSZTIKAI TERVEZÉSE HIBRID MÓDSZERREL
Barhm Mohamad
PhD hallgató, Miskolci Egyetem, Gép- és Terméktervezési Intézet
3515 Miskolc, Miskolc-Egyetemváros, e-mail: pywand@gmail.com
Jálics Károly
egyetemi docens, Miskolci Egyetem, Gép- és Terméktervezési Intézet
3515 Miskolc, Miskolc-Egyetemváros, e-mail: machijk@uni-miskolc.hu
Andrei Zelentsov
egyetemi docens, Bauman Moscow State Technical University, Piston Engine Department
105005 Moscow, Russia, e-mail: Zelentsov.aa@gmail.com
Absztrakt
A kipufogó- és hangtompító zaj egy kihívást jelentő probléma a gépjárműiparban. Noha a rendszer fő
célja a motorból származó akusztikus impulzusok intenzitásának csökkentése, az ilyen rendszerek által
kiváltott ellennyomást a lehető legkisebbre kell csökkenteni, hogy garantálják a motor maximális telje-
sítményét. Ez a tanulmány egy hatékony eljárást mutat be egy Formula Student versenyautó (FS) reaktív
hangtompítója átviteli veszteségének optimalizálására analitikai módszerek alkalmazásával. Ennek so-
rán létrehoztuk a hangtompító CAD modelljét, majd ezt az AVL BOOST-ban és más fejlett kereskedelmi
forgalomban elérhető tervező szoftver (SolidWorks 2017) segítségével egy végeselemes akusztikai
(FEA) modellé alakítottuk. A modell segítségével az áramlási tulajdonságokat, a nyomást és a sebessé-
get vizsgáltuk. A modell ellenőrzése után elvégeztük a tervezési paraméterek érzékenységvizsgálatát a
hangtompító hangnyomásszintjének (SPL) optimalizálása érdekében. Javaslatokat tettünk egy egyenle-
tesebb SPL görbe elérésére.
Kulcsszavak: Formula Student, hangtompító, hangnyomásszint, 3D szimuláció
Abstract
Exhaust and muffler noise are a challenging problem in the industry. While the main purpose of the
system is to reduce the intensity of the acoustic pulses originating from the engine exhaust valves, the
back pressure induced by these systems must be kept to a minimum to guarantee maximum performance
of the engine. This study presents an efficient process to optimize the transmission loss of Formula
Student race car (FS) reactive muffler by using analytical methods. CAD file of the muffler was estab-
lished for developing the FEA model in AVL BOOST and another commercial advanced design software
(SolidWorks 2017). The flow properties, pressure and velocity were moitored. After the model was ve-
rified, sensitivity studies of design parameters were performed to optimize the sound pressure level
(SPL) of the muffler. Recommendations are made for obtaining smoother SPL curves.
Keywords: Formula Student, muffler, SPL, 3D simulation
1. Bevezetés
A kipufogó hangtompító kialakítása fontos szerepet játszik egy Formula Student versenyautó teljes
akusztikai teljesítményében. Általában a hangtompító beillesztési és átviteli veszteségét használják az
2. Mohamad, B., Jálics, K., Zelentsov, A. Hangtompító akusztikai tervezése hibrid módszerrel
549
akusztikai „teljesítménye” becslésére. Számos publikáció érhető el a hangtompítók akusztikus kialakí-
tásáról és mérési módszereiről. A piacon három hangtompító típus létezik: visszaverődés elvén alapuló
(reaktív), a hangelnyelés elvén alapuló (disszipatív) és hibrid.
Az első típusban a zajcsökkentést a hanghullámok visszaverődése miatt bekövetkező részleges kiol-
tás éri el. Ez alacsony frekvenciatartományban működik jól. A második típusú jó hangelnyelő anyagokat
alkalmaz a zajcsökkentéshez. Az akusztikus energia hővé alakul, majd elnyelődik. Ezt a típust a közepes
és magas frekvenciákon alkalmazzák.
A harmadik típus a visszaverődéses és az abszorpciós kombinációja. A hibrid hangtompító széles
frekvenciatartományban használható. Ennek a cikknek a célja a Formula Student versenyautó kipufogó
rendszer érzékenységének elemzése három kulcsfontosságú tervezési paraméter alapján, azaz a válaszfal
(perforált cső) elhelyezkedése, a kamra térfogatának változása és a hangelnyelő anyag beillesztése a
reaktív kipufogóba. Mohamad és társai a 2017. évi áttekintésben mutatták be az iparban használt hang-
tompítókat, és ez az áttekintés az áramlási és hőmérsékleti eloszlást szemlélteti a csővezeték hossza
mentén. Leírták a kipufogódob tervezésében alkalmazott, kísérleti, gyakorlati módszereket és bemutat-
ták az átviteli veszteség jellemzésére használt mérőszámokat.
Az 1D akusztikai számítások sokkal gyorsabbak, és még mindig jó közelítést nyújtanak a vizsgált
rendszerről. A Mohamad és Amroune 2019-ben számítástechnikai CFD eszközöket alkalmaztak a motor
hangtompítójának akusztikus teljesítményére gyakorolt áramlási hatások leírására. Ez bemutatja az át-
viteli veszteség alakulását különböző frekvenciákon az 1D szimuláció használatával. Mohamad et al
2019-ben az átviteli mátrix módszerét (TMM) mutatta be a kipufogódob átviteli veszteségének számí-
tásához. Az algoritmus a kipufogórendszer más részeire is alkalmazható. Egy létező hangtompító ilyen
vizsgálatának eredményét összehasonlították a járművön elvégzett. mérés adataival. A hangtompító át-
viteli veszteségét optimálva egy új hangtompító kialakítást javasoltak. A validálásban nagy szerepet
játszott más irodalmi forrásokból vett eredmények. A Mohamad 2019-ben számos új technikát tanulmá-
nyozott kipufogórendszerek akusztikus teljesítményének szempontjából irodalomkutatás segítségével.
Megmagyarázza mindkét elméleti megközelítés mögött meghúzódó alapelveket, valamint egy zajforrás
leírási módszert, amely felhasználható a két módszer összekapcsolására.
2. A módszer
A kiinduló hangtompító geometria a jelenlegi versenyautó reaktív hangtompító prototípusa alapján va-
lósult meg a SolidWorks 2017 fejlett tervezőszoftverrel. A modell tartalmazza a bemeneti, kimeneti, a
perforált csövet és a kamrát. A perforált csövet a kipufogódob hengeres alakú kamrájának közepére
helyeztük. A kipufogódob keresztmetszetét és méreteit az 1. ábra tartalmazza. A hangtompító elneve-
zése a továbbiakban PPiP lesz.
Számos eljárást készítettünk a modellezés CFD ezközök segítségével történő elvégzésére, valamint
az optimális kialakítás elkészítéséhez az AVL BOOST v 2017 felhasználásával történő vizsgálatokhoz.
A hangtompító titánötvözetből készült, és az áramló gáz tulajdonságait közvetlenül mindkét szoftver
adatbázisból választottuk ki. Az áramlás akusztikai elemzésénél figyelembe vett peremfeltételek repre-
zentatívak a kipufogórendszerre több motorfordulatszám esetén is.
Az AVL Boost-ban létrehozott 1D modell az egydimenziós akusztikai megközelítést alkalmazza a
dugattyús motor szívó- és kipufogórendszereiben lezajló folyamatok leírására. A probléma egydimen-
ziós megközelítése lehetővé teszi a csövek és csatornák méreteinek (átmérők, hosszúságok, a lekerekí-
tési sugarak) a gázáramra gyakorolt hatásának becslését. A teljes hengert egyetlen térfogatnak tekinti,
amelyben a szívás, a sűrítés, az égés, a kiterjedés és a kiáramlás folyamata történik. Ez a térfogat, a
háromdimenziós megközelítéstől eltérően, nem oszlik altartományokra (kontroll vagy véges térfogatok).
3. Mohamad, B., Jálics, K., Zelentsov, A. Hangtompító akusztikai tervezése hibrid módszerrel
550
Az egyenletrendszer (energia, kontinuitás, gázállapot) csak egy olyan térfogatra van felírva, amely az
időben változik (háromdimenziós megközelítésben - az egyenletrendszert minden egyes kontrolltérfo-
gatra megoldják).
1. ábra. A versenyautó módosított hangtompítójának (PPiP) felépítése
3. Matematikai analízis
A matematikai modell a háromdimenziós instacionér tömegáram alapvető egyenletein alapszik: az im-
pulzus (Navier-Stokes), az energia (Fourier-Kirchhoff) és a kontinuitás egyenletein, amelyek Reynolds-
féle formájában jelennek meg a Favre - módszer szerinti átlagolás után:
𝜌̅
𝑑𝑊ⅈ
̅̅̅̅
𝑑𝑡
= 𝐺ⅈ
̅ −
𝜕𝑃̅
𝜕𝑥ⅈ
+
𝜕
𝜕𝑥𝑗
[𝜇 (
𝜕𝑊ⅈ
̅̅̅̅
𝜕𝑥𝑗
+
𝜕𝑊̅𝑗
𝜕𝑥ⅈ
−
2
3
𝛿ⅈ𝑗
𝜕𝑊̅ 𝑘
𝜕𝑥 𝑘
) − 𝜌̅ 𝑊′
ⅈ
̅̅̅̅̅ 𝑊′̅̅̅̅𝑗], (1)
𝜌
𝑑𝐻
𝑑𝑡
= 𝐺𝑗 𝑊𝑗 +
𝜕𝑃
𝜕𝑡
+
𝜕
𝜕𝑥ⅈ
(𝜏ⅈ𝑗 𝑊𝑗) +
𝜕
𝜕𝑥𝑗
(𝜆
𝜕𝑇
𝜕𝑥𝑗
− 𝑐 𝑝 𝜌𝑇′ 𝑊′̅̅̅̅𝑗), (2)
𝜕𝜌̅
𝜕𝑡
+
𝜕
𝜕𝑥𝑗
(𝜌̅ 𝑊̅𝑗) = 0, (3)
ahol W a sebesség; p a nyomás, Gi a térfogati erők sűrűségvektorának vetítése egy derékszögű koordi-
nátarendszer Oxi tengelyére, H a teljes fajlagos energia, T a hőmérséklet, μ a dinamikus viszkozitás, cp a
hőkapacitás állandó nyomáson, 𝜏̅ⅈ𝑗 az átlagos Reynolds feszültség, λ a hővezető képesség, ρ a sűrűség,
δij a Kronecker delta; és ∂/∂t a differenciál operátor.
A transzport egyenletek rendszerét Reynolds formában (1, 2, 3. sz. egyenletek) a k-ζ-f turbulencia
modell zárja le. Ezt a modellt speciálisan fejlesztették ki és ellenőrizték a belsőégésű dugattyús motorok
4. Mohamad, B., Jálics, K., Zelentsov, A. Hangtompító akusztikai tervezése hibrid módszerrel
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áramlási viszonyainak, égési és hőátadási folyamatainak leírására (Tatschl et al, 2005 és Tatschl et al,
2006). A k-ζ-f modellnek három egyenlete van: a turbulencia k kinetikus energiájára, az energia ε elosz-
lási sebességére és a normalizált sebességi 𝜁 = 𝑊̅ 2
/𝑘 egyenleteire (Hanjalič et al, 2004).
Ún. „hibrid falfüggvényeket” (Popovać és Hanjalić, 2005) használtunk a gázáram és a határrétegbe
történő hőátadás paramétereinek meghatározására. Merker és társai, 2019, Basshuysen és Schäfer, 2007
és Kavtaradze et al, 2009 hangsúlyozzák, hogy ez a matematikai modell alkalmazható a dugattyús mo-
torokban lezajló folyamatok CFD-számításaira.
A motorok kipufogórendszerében található hangtompítók esetében a különböző hangtompító-felépí-
tések és paraméterek nyilvánvalóan eltérő hatással vannak a zaj csökkentésére. A hangtompítóban le-
zajló komplex munkafolyamat miatt a kutatók folyamatosan vitatták a hangtompítók belső felépítésé-
nek, elméleti számításának és kialakításának módszereit. Az hangelnyelő anyag és a belső cső porozitá-
sának a hangnyomásszintre gyakorolt hatását az alábbi egyenlettel lehet leírni:
Anyag porozitás = 1 - (térfogat sűrűség) / (anyag sűrűség) [2]
Az anyagjellemzők, pl. sűrűség értéket a szoftver adatbázisból származnak.
4. Eredmények
4.1. 3D szimulációk
A 2. ábra a hangtompítón belüli áramlási sebesség eloszlását mutatja. Mint látható, a legnagyobb áram-
lási sebesség a perforált csövet tartalmazó hangtompító kimeneténél található könyökben volt, a legna-
gyobb nyomás pedig a bementnél volt, ahogy azt a 3. ábra mutatja.
2. ábra. A sebességeloszlás a bemenettől (jobb oldal) a kimenetig (bal oldal) a PPiP hangtompítóban
A perforált csöves hangtompítóba bejutó gáz nagy része közvetlenül a perforált csőből jut a hang-
tompító belső térfogatába. A perforált cső furatainak átmérője 3 mm volt. A nagy áramlási ellenállás
miatt a gáz energiája jelentősen csökken, amikor a furatokon keresztüláramlik.
Háromdimenziós CFD számítások alapján meghatároztuk a kipufogó nyomásesésének értékét, fi-
gyelembe véve a belső perforált cső jelenlétét is. A háromdimenziós modellek lehetővé tették az anyag-
porozitás értékének tisztázását is. Ezeket az értékeket tovább használtuk az 1D kipufogórendszer-modell
kalibrálásához az AVL Boost rendszerben.
5. Mohamad, B., Jálics, K., Zelentsov, A. Hangtompító akusztikai tervezése hibrid módszerrel
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3. ábra. Nyomáskontúr (áramlási irányvonalak) a perforált csőben és a hangtompító térfogati rész-
ében (bal oldal: bemenet, jobb oldal kimenet)
4.2. A motor teljesítményének változása
A további vizsgálatokhoz a hangtompító következő paramétereit használtuk, ill. variáltuk: átmérő
(Dm_in), a perforált belső cső furatának átmérője (Dm_hole), a hangtompító héj külső átmérője (Dm_out),
valamint a hosszát (Lm). A paraméterek változtatásával és az AVL BOOST szoftver segítségével figyel-
tük, hogy a motor teljesítménye mennyiben változik. Különböző típusú kipufogó hangtompító alkalma-
zása az aktuális Formula Student motornál csak kevéssé befolyásolja a teljesítményt, mivel nincs kata-
lizátor, vagy közbenső hűtő, amely magas ellennyomást hozna létre.
4.3. A hangtompító típusának, geometriájának és felépítésének hatása a zajra
Amint azt a 4. ábra mutatja, a módosított (PPiP) hangtompító lehetővé teszi a zajszint csökkentését, de
n > 3000 1/min érték fölött a zajszint továbbra is magasabb, mint a csak kamrás hangtompító esetén. Ez
a cikk a hangtompító össz-hangnyomásszintjének optimalizálására irányult, ahelyett, hogy azt minden
egyes frekvencián vizsgálná. A módosított hangtompítóban olyan hatások érvényesülhetnek, amelyek
csak bizonyos frekvencián fejtik ki hatásukat, viszont megnövelik az össz-hangnyomásszintet.
4. ábra. A Honda CBR 600RR (PC 37) versenyautómotor hangnyomásszintjének összehasonlítása tér-
fogat és PPiP hangtompítók esetén
6. Mohamad, B., Jálics, K., Zelentsov, A. Hangtompító akusztikai tervezése hibrid módszerrel
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A hangtompító geometriai paramétereinek a zajcsökkentésre gyakorolt hatását is tanulmányoztuk.
Az 5. ábra a motor zajszintjének összehasonlítását mutatja 1 m távolságra a hangtompító kimeneti nyí-
lásától, alap és módosított hangtompító alkalmazása esetén. Az kipufogógáz áramlási zaj terjedésének
szimulálása és az azt befolyásoló tényezők tárgyalása, ennek a kombinációs elméletnek a hatékonyságát
tükrözi gyakorlati körülmények között, mivel a hangtompító motor általi gerjesztési forrása inkább a
nyomásváltozás, szemben a rezgési sebességgel, amikor a hangtompítót az autó motorjához csatlakoz-
tatjuk.
A motor működési paramétereinek, beleértve a zajszintet, a kimeneti cső hosszától való jelentős füg-
gését a cső nyitott végéből hátrafele terjedő hullámok határozzák meg. Ennek eredményeként a motor
teljesítményének fenntartása mellett a legalacsonyabb zajszintet érjük el, ha Dm_out = 126 mm és
Lm = 436 mm.
5. ábra. A Honda motor akusztikus teljesítménye kiinduló geometriájú PPiP hangtompító (Dm_hole =
3 mm, Dm_in = 47 mm, Dm_out = 116 mm, Lm = 426 mm) és módosított geometriájú PPiP hangtompító
(Dm_hole = 3 mm, Dm_in = 47 mm, Dm_out = 126 mm, Lm = 436 mm) esetén
Vizsgáltuk továbbá hangelnyelő anyag alkalmazásának hatékonyságát is a hangtompító zajcsökken-
tésének szempontjából. Hangelnyelő anyag peremfeltételeit alkalmaztuk a szimulációban tényleges fi-
zikai vastagság nélkül. Ilyen módon hangelnyelő anyagot „helyeztünk” a külső héj belső oldalára (PPiP
w AM in OP), a perforált cső külső oldalára (PPiP w AM in IP), valamint számításokat végeztünk az
előző két eset kombinációjára is (PPiP w AM in IP & OP).
A 6. ábra mutatja, hogy a hangelnyelő anyag alkalmazása lehetővé teszi a hangnyomásszint 15-20% -
kal történő csökkentését a teljes motorfordulatszám tartományban. A motor teljesítményét számítva
azonban észrevehetjük, hogy növekszik a kimeneti áramlási ellenállás, ezáltal csökken a motor teljesít-
ménye.
Ezen kívül a motor működése közben a hangelnyelő anyag eltömődhet a kipufogógázokban lévő
koromrészecskékkel, ami további növeli az áramlási ellenállást és a motor működési körülményeinek
további változását, leginkább romlását okozza.
A fő hangtompítónak nemcsak könnyebb tömege volt, hanem ahhoz is szüksége volt, hogy biztosítsa
a minimális hangnyomásszintet a kimenetnél, ami többcélú optimalizálási probléma. Az összes optima-
lizálási folyamatot a kereskedelmi forgalomban elérhető szoftverrel hajtottuk végre.
A hangelnyelő anyag használata lényegesen nagyobb csökkenést eredményez a motor zajszintjében
hasonló méretű hangtompítók alkalmazása esetén. A hangelnyelő anyag paraméterei: porozitás σ = 0,9,
7. Mohamad, B., Jálics, K., Zelentsov, A. Hangtompító akusztikai tervezése hibrid módszerrel
554
áramlási ellenállás R = 10000 Ns/m4
. Az anyag porozitása a levegőnek az anyagon belüli hányadát kép-
viseli (0-1). Esetünkben a 0.9 anyagporozitás azt határozza meg, hogy a térfogat 10% -a anyag, és
90% - a levegővel töltött.
6. ábra. A Formula Student versenyautó motor hangnyomás szintje különféle kialakítású hangtompító-
val
5. Összefoglalás
A vizsgált motor akusztikai problémáját ezek alapján hangelnyelő anyag felhasználásával oldhatjuk
meg. Ez a zajszint további csökkentésének lehetséges lépése. Ezek után a hangtompító megfelelhet a
kipufogó zaj a versenyszabályzatban foglalt előírásainak. Az 1D és 3D szimulációk használata a kipu-
fogórendszerben jelentősen csökkentheti a kipufogórendszerek optimális méretének kiválasztásához
szükséges időt és költségeket. Esetünkben az eredmények nagyban hozzájárulhatnak ahhoz, hogy vers-
anyautó tervezői, használói sikeresen kiválasszák a kipufogódob megfelelő felépítését méretét és ab-
szorpciós anyagát úgy, hogy a versenyautó, nemcsak akusztikai szempontból, versenyképes legyen.
6. Köszönetnyilvánítás
A cikkben ismertetett kutató munka az EFOP-3.6.1-16-2016-00011 jelű „Fiatalodó és Megújuló Egye-
tem – Innovatív Tudásváros – a Miskolci Egyetem intelligens szakosodást szolgáló intézményi fejlesz-
tése” projekt részeként – a Széchenyi 2020 keretében – az Európai Unió támogatásával, az Európai
Szociális Alap társfinanszírozásával valósul meg.
Irodalom
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