scholarly journals Design and evaluating efficiency of gas exhaust system silencer of outboard motor SEA PRO 2.5

2021 ◽  
Vol 2021 (1) ◽  
pp. 81-87
Author(s):  
Mikhail Nikolaevich Pokusaev ◽  
Konstantin Evgenievich Khmelnitsky ◽  
Alexei Alekseevich Kadin ◽  
Alexei Viktorovich Sergeev
Keyword(s):  
Noise Reduction ◽  
Noise Level ◽  
Aerodynamic Drag ◽  
Exhaust System ◽  
Water Layer ◽  
Sound Level ◽  
Low Frequencies ◽  
Full Speed ◽  
Made In China ◽  
Exhaust Systems

The article presents the results of developing and evaluating the effectiveness of the silencer of outboard motor SEA PRO 2.5 made in China. The experiments were carried out in a large experimental pool of Astrakhan State Technical University, with the use of a noise meter-spectrum analyzer Ecophysics-110 of the first class, with the software Signal+3G Light. In the theoretical analysis of the development, it has been suggested that the efficiency of silencers of exhaust systems of outboard motors could have a smaller effect than with cars, since at underwater exhaust the noise reduction will occur from the water layer when the motor is submerged. It has been proved that using a silencer in underwater exhaust systems of outboard motors can increase the aerodynamic drag for gases and reduce power. To test the theoretical assumptions, there was made a silencer for the gas exhaust system of the outboard motor SEA PRO 2.5 from stainless steel perforated sponge. It was determined that the net effect of the silencer (excluding water silencing) could be heard at low frequencies (up to 125 Hz) and makes up to 12.7 dba at full speed of the motor. The average equivalent sound level is reduced up to 4.5 dba at low speed, and at full speed of the outboard motor is practically not evident. In addition, the outboard motor noise level was reduced by water and made at full speed up to 22 dba for frequencies over 2000 Hz; for average equivalent noise level it made 15 dba. The combination of noise reduction by water and by a silencer helps to reduce noise at low and high sound frequencies, which is a positive effect of the developed device.

Paper 16: A Study of Tractor Noise Control

1969 ◽  
Vol 184 (17) ◽  
pp. 149-169
Author(s):  
J. Matthews ◽  
J. D. C. Talamo
Keyword(s):  
Hearing Loss ◽  
Diesel Engine ◽  
Noise Reduction ◽  
Noise Level ◽  
Exhaust System ◽  
Low Noise ◽  
Acoustic Features ◽  
Noise Levels ◽  
Engine Design ◽  
High Incidence

A high incidence of hearing loss has been encountered among tractor drivers, and noise levels are shown to be further increased by the addition of cabs, particularly those which are structurally strong to resist crushing if the vehicle overturns. Some reductions in the noise level of the operator's environment can be obtained by covering the engine or by exhaust system modifications, while possible future improvements to diesel engine design may effect a significant improvement. However, it is proposed that noise reduction is likely to be achieved by attention to acoustic features of the operator's cab. The inclusion of resilient mounts, substantial floors and bulkheads, and acoustically absorbent linings are all shown to provide worthwhile improvements and, in combination, these measures can reduce noise levels from more than 100 dBA to 90 dBA or less. Where the tractor is fitted with a safety frame only, a low noise fabric cladding is shown to be feasible.

scholarly journals Analysis of frequency spectrum of outboard motor Hangkai 4.0 noise when nosing

2020 ◽  
Vol 2020 (3) ◽  
pp. 33-39
Author(s):  
Mikhail Nikolaevich Pokusaev ◽  
Konstantin Evgenievich Khmelnitsky
Keyword(s):  
Frequency Spectrum ◽  
Noise Level ◽  
External Noise ◽  
Sound Level ◽  
Structural Elements ◽  
Small Vessels ◽  
Measuring Devices ◽  
Full Speed ◽  
Level Meter ◽  
Average Noise Level

The article deals with the results of experiments on measuring the Hangkai 4.0 outboard motor when using various types of noise-insulating hoods. The tests were carried out in accordance with GOST ISO 14509-1-2015 “Small Vessels. Noise measurement of small motor pleasure craft. Part 1. Noise of a passing ship” at full speed with the engine speed 4500 rev/min and motor power 4 HP. Measurements were carried out when the vessel was at a distance of 25 metres both sides with different options covering outboard motor. The average noise level and its frequency spectrum were measured, and the effectiveness of various types of hoods was evaluated. In the course of the experiment there was used a standard plastic hood of the Hangkai 4.0 engine, a noise-insulating hood (plastic hood, glued inside with automotive foil noise insulation) and an author's combined noise-insulating hood Kaponistr. Description and structural elements of Kaponistr are presented; it has been stated that the hood design was patented as a useful model in 2019. In the result of conducted experiments it has been inferred that the external noise level of the Hangkai 4.0 outboard motor (without hood) does not exceed 74.3 dBA, but is at the level of the permissible value of 75 dBA, so, when operating, the motor needs a standard hood. The prevailing frequency range of an outboard boat motor is within 300 - 2500 Hz. It has been inferred that each type of nosing (standard, sound-proof, combined, without hood) reduces the noise level of the outboard motor. The greatest effect of reducing external noise is observed when using a combined hood Kaponistr at a frequency of 800 Hz by 19.4 dBA or by 27%. In the research there were used the control and measuring devices (sound level meter, vibrometer, spectrum analyzer Ekofizika-110 (white); acoustic calibrator AK-1000) and software (Signal+3G Light manufactured by PKF Digital Instruments, LLC).

Study of Jet Noise Reduction on Separated Exhaust System Using Chevron Nozzles

2014 ◽  
Vol 1078 ◽  
pp. 228-234
Author(s):  
Wan Ren Shao ◽  
Xi Hai Xu ◽  
Jing Yu He ◽  
Fei Wu
Keyword(s):  
Noise Reduction ◽  
Jet Noise ◽  
Exhaust System ◽  
Scale Model ◽  
Low Frequencies ◽  
Chevron Nozzles ◽  
Field Noise ◽  
Bypass Ratio ◽  
Computational Predictions ◽  
Noise Spectra

The jet noise reduction of chevron nozzles was investigated on high bypass ratio turbofan engine separated exhaust system using both computational predictions and scale model experiments. Six different exhaust nozzles are designed including one baseline nozzle and five different chevron nozzles. The jet noise experiments were carried out in the anechoic chamber. Tam and Auriault’s jet noise prediction theory and MGBK theory were used to predict the noise spectra of different exhaust nozzles. The results show that the far-field noise spectra as well as the noise reduction benefits of chevrons are predicted correctly by the two theories although some discrepancies occur at the high frequency range, and Tam and Auriault’s jet noise theory can give relatively more accurate prediction results. chevron nozzles reduce jet noise at the low frequencies, but increase it at high frequencies.

Detection and identification of illegal-modified private cars through frequency band analysis

2021 ◽  
Vol 263 (5) ◽  
pp. 1765-1772
Author(s):  
Hok Man Joyce Chow ◽  
Sau Cheong Cheung ◽  
Kit Wing Cheng ◽  
Chee Kwan Lee ◽  
Terence Tsang ◽  
...  
Keyword(s):  
Exhaust System ◽  
Noise Spectrum ◽  
Sound Level ◽  
Vehicle Exhaust ◽  
Late Night ◽  
Detection And Identification ◽  
Single Vehicle ◽  
Level Meter ◽  
Post Purchase ◽  
Exhaust Systems

Post-purchase-illegal-modification of road vehicles' exhaust systems by vehicle fanatics for loudness has caused an upsurge in nuisances to local residences when driven and rallied during late night and early mornings. Traditional enforcement measures rely on setting up roadblocks by the Police at rallying hotspots. These measures involve the judgement of individual police officer and can be subjective. With the aid of noise monitoring equipment, the accuracy and efficiency of on-site exhaust system-modified vehicle detection can be enhanced. Since the sound profile of a single-vehicle exhaust cannot be captured by simple roadside noise level measurements alone, segregation and analysis of the noise spectrum are employed to identify vehicles with modified exhaust systems. The paper presents the findings of investigating the feasibility and accuracy of off-the-shelf devices for detecting vehicles fitted with modified exhaust systems, with private cars being the primary target. A pilot test by roadside noise monitoring has been conducted with a sound level meter and an acoustic camera and revealed an on-site accuracy of up to 75%. Data collected during the tests were further used to explore the applicability of integrating artificial intelligence with traditional noise monitoring devices.

AN IMPROVED ARMORED VEHICLE KRAZ “FIONA” NOISE SILENCER

2019 ◽  
pp. 21-26
Author(s):  
Volodymyr Fedorov ◽  
Vasyl’ Yanovsky ◽  
Dmytro Kovalshuk
Keyword(s):  
Noise Reduction ◽  
Speed Of Sound ◽  
Acoustic Waves ◽  
Noise Level ◽  
Combustion Engine ◽  
Environmental Aspect ◽  
Exhaust Gases ◽  
Ecological Requirements ◽  
On The Road ◽  
Armored Vehicle

Ecological requirements for cars grow from year to year, both in the world as a whole, and in Ukraine in particular. This is especially true of noise pollution. Additionally, noise reduction becomes relevant, taking into account the conduct of military operations during the last 5 years on the territory of Ukraine. The war has caused a special need for military vehicles for which masking properties are vital. Noise is a serious disincentive factor. Therefore, its reduction for a military vehicle, apart from the environmental aspect, is of a purely military nature, that is, it is extremely important. The car has many sources of noise there are many ways to deal with them. One of the most powerful source of noise is the sleeping bag. This kind of noise is reduced by means of silencers of noise. The vast majority of silencer data in the basis of its design has a reactive (or resonant) muffler. To calculate the jet silencer you must know the speed of sound in the sleeping bags. In order to increase the acoustic efficiency of reactive and resonant mufflers of exhaust gases noise of the ICE of cars, an experimental method was proposed for determining the speed of sound in the sleighs. Implementation of the method is carried out by measuring the attenuation of acoustic waves. The noise level of the bedrooms is measured without silencer and silencer. Based on the data obtained, the noise reduction performance of the residual is established. From the well-known formula, based on the calculation of the efficiency of the silencing of a jet muffler, a formula is obtained for calculating the speed of sound in the sleeping quays. In this formula, all parameters are known: the level of silencer efficiency, the noise level of the sleeping, the ratio of areas of cross sections of the muffler and the inlet pipe and the length of the muffler. The sound speed thus established can continue to be used not only for engines of the type for which measurements and calculations were made, but also with a certain approximation for some other types of engines. This method provides high accuracy for determining the required parameter. In the given work on the example of the armored car KrAZ “Fiona” the calculation of efficiency increase of the reactive silencer is made due to the above-mentioned method. Also, the projected decrease in the external noise level of the KrAZ Armored Vehicle “Fiona” is considered by determining the speed of sound in the recesses on the trunk cycle on the road with acceleration up to speed of 50 km/h (75 km/h) and the movement with this speed, as well as when driving at a speed of 45 km/h. Keywords: transport, armored car, internal combustion engine, exhaust, exhaust gases, noise, source, acoustic efficiency, acoustic efficiency, speed of sound, jet muffler.

DEPENDENCE OF THE NOISE LEVEL OF DRY FAN COOLING TOWERS ON THE POWER OF THERMAL POWER PLANTS

2021 ◽  
Author(s):  
Владимир Борисович Тупов ◽  
Айнур Булатович Мухаметов
Keyword(s):  
Noise Level ◽  
Power Plants ◽  
Thermal Power ◽  
Electrical Power ◽  
Sound Level ◽  
Thermal Power Plants ◽  
Cooling Towers ◽  
Surrounding Area ◽  
Fan Cooling

Сухие вентиляторные градирни тепловых электрических станций могут быть источником превышения санитарных норм на территории станции и в окружающем районе. В статье проведен анализ уровня шума сухих вентиляторных градирен в зависимости от мощности тепловых электрических станций. Получена формула позволяющая определить изменение уровня звука сухих вентиляторных градирен в зависимости от электрической мощности тепловых электрических станций. Dry fan cooling towers of thermal power plants can be a source of exceeding sanitary standards on the territory of the plant and in the surrounding area. The article analyzes the noise level of dry fan cooling towers depending on the power of thermal power plants. A formula has been obtained that makes it possible to determine the change in the sound level of dry fan cooling towers depending on the electrical power of thermal power plants.

Application of compact silencers as a noise barrier to a naturally ventilated double-skin façade

2021 ◽  
Vol 69 (3) ◽  
pp. 220-228
Author(s):  
Jeehwan Lee ◽  
Jae D. Chang ◽  
Robert Coffeen
Keyword(s):  
Noise Reduction ◽  
Surface Area ◽  
Natural Ventilation ◽  
Experimental Investigations ◽  
Test Case ◽  
Open Surface ◽  
Low Frequencies ◽  
Noise Barrier ◽  
Double Skin ◽  
Air Vent

A prior study of the acoustical performance of a double-skin facade (DSF) as a noise barrier was carried out based on the percentage of the air vent open surface area, shading louver configurations, and shading louver surface materials. Earlier research findings led to experimental investigations of the acoustical performance capabilities of compact silencers to replace DSF air vents as both noise barriers and air channels because DSF air cavities, which contribute to natural ventilation performance (e.g., wind-driven or buoyancy-driven performance), are acoustically vulnerable to noise transmitted through the air vents. This experimental investigation aims to explore noise reduction (NR) through compact silencers applied to DSF air vents. Double-skin facade mock-up test cases were designed based on three test scenarios of a ventilation open surface area: (1) a 100%air vent open surface area (open mode), (2) a 0% air vent open surface area (closed mode), and (3) a compact silencer. From a data analysis of DSF mock-up test results, the overall NR values of a DSFmock-up ranged from20 to 37 dB(A) depending on the number of compact silencers and the shading louver orientation used. Configurations of compact silencers and shading louvers helped the DSF mock-up achieve additionalNR values of 5 to 10 dB(A) depending on the test case. Moreover, applying compact silencers to a naturally ventilated DSF mock-up led to significant noise reduction at low frequencies (125Hz).

Comparison of Noise Reduction Performance Evaluation Methods for Low-Noise Pavement in Korea- Part

2021 ◽  
Vol 263 (4) ◽  
pp. 2930-2939
Author(s):  
Byungchae Kim ◽  
Hyunjin Kim ◽  
Wonuk Kang
Keyword(s):  
Noise Reduction ◽  
Noise Level ◽  
Measurement Method ◽  
Road Traffic ◽  
Low Noise ◽  
Management Standards ◽  
Close Proximity ◽  
Porous Pavement ◽  
Reduction Effect ◽  
Measurement Location

In Korea, road noise is assessed as a measurement method of exterior noise emitted by road vehicle for management standards by the National Institute of Environmental Sciences. In this method, the noise felt at the actual pickup point is measured as LAeq (the roadside equivalent noise level). Recently, to clarify the standard for measuring noise on low-noise pavements, the CPX (ISO11819-2; Close-proximity method) was first introduced in the Porous Pavement Guidelines of the Ministry of Land, Infrastructure and Transport. According to ISO, the CPX adopts the side microphone as a mandatory measurement location, and the rear optional. The side location has been a mandatory due to its high correlation with SPB (ISO 11819-1, Statistical Pass-by method). However, according to our previous study on the correlation evaluation between L and CPX rear microphone noise level, both noise reduction effect was about 9-12 dB(A) showed a high correlation in Korea where heavy road traffic is common. The following study aims to show the consistent correlation between the L and CPX rear noise level. Furthermore, it is intended to be helpful in selecting the location of the CPX microphone that can most effectively represent the actual noise on the low-noise pavement in Korea.

Methods to Improve Combustion Stability, Efficiency, and Power Density of a Small, Port-Injected, Spark-Ignited, Two-Stroke Natural Gas Engine

2017 ◽  
Author(s):  
Derek Johnson ◽  
Mahdi Darzi ◽  
Chris Ulishney ◽  
Mehar Bade ◽  
Nima Zamani
Keyword(s):  
Natural Gas ◽  
Power Density ◽  
Low Cost ◽  
Exhaust System ◽  
Combustion Stability ◽  
Liquid Fuels ◽  
Delivery Ratio ◽  
Resonance Theory ◽  
Indicated Mean Effective Pressure ◽  
Exhaust Systems

Two-stroke engines are often used for their low cost, simplicity, and power density. However, these engines suffer efficiency penalties due to fuel short-circuiting. Increasing power density has previously been an area of focus for performance two-stroke engines — such as in dirt bikes. Smaller-displacement engines have also been used to power remote controlled cars, boats, and aircraft. These engines typically rely on gasoline or higher-octane liquid fuels. However, natural gas is an inherently knock-resistant fuel and small natural gas engines and generators could see increased market penetration. Power generators typically operate at a fixed frequency with varied load, which can take advantage of intake and exhaust system tuning. In addition, stationary engines may not be subject to size restrictions of optimal intake and exhaust systems. This paper examines methods to improve combustion stability, efficiency, and power density of a 29cc air-cooled two-stroke engine converted to operate on natural gas. Initial conversion showed significant penalties on delivery ratio, which lowered power density and efficiency. To overcome these issues a tuned intake pipe, two exhaust resonators, and a combustion dome were designed and tested. The engine was operated at 5400 RPM and fueling was adjusted to yield maximum brake-torque (MBT). All tests were conducted under wide-open throttle conditions. The intake and exhaust systems were designed based on Helmholtz resonance theory and empirical data. The engine utilized a two-piece cylinder head with removable combustion dome. The combustion dome was modified for optimal compression ratio while decreasing squish area and volume. With all designs incorporated, power increased from 0.22 kW to 1.07 kW — a factor of 4.86. Efficiency also increased from 7% to 12%. In addition to these performance gains, the coefficient of variation (COV) of indicated mean effective pressure (IMEP) decreased from just above 11% to less than 4%.

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