Seyir dirençlerinin tespiti ve dinomometre simülasyonu için taşıt datalarının hazırlanması
Determination of road resistances and vehicle data preparation for dynamometer simulation
- Tez No: 21988
- Danışmanlar: DOÇ. DR. AHMET GÜNEY
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1992
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 71
Özet
ÖZET Bu çalışmada, düz yolda düzgün doğrusal bir hareket yapan bir taşıta etki eden seyir dirençleri bir bilgisayar programı ile tesbit edilmiştir. Çalışmanın amacı şasi dinamometresi için taşıt datalarını oluşturmaktadır. Öncelikle seyir dirençlerinin neler olduğu hakkında bilgiler verilmiş ve kısaca oluşum nedenleri açıklanmıştır, Deney düz yolda ve doğrusal hareket eden bir taşıt için yapıldığı için, ivme direnci ve yokuş direncinden çok diğer seyir dirençlerine daha çok önem verilmiştir. Kısaca hazırlanan bu tez iki aşamadan ibarettir. Birinci kısımda, deney yapılır ve veriler oluşturulur. Oluşturulan bu veriler ikinci kısımda bilgisayar programına da ta olarak girilir, seyir dirençleri saptanır. Deney düz yolda tur çiftleri halinde (gidiş-dönüş) yapılmalıdır. Çift halinde yapılmasının sebebi, hataları ortadan kaldırmaktadır. Deneyde taşıt düz yolda 70 mil/saat (113 km/saat) hız dan serbest yavaşlamaya bırakılır, her 5 sn. de hızlar oku nur. Okuma sayısını keyfi seçilir. Deneyde oluşan tüm veriler bir bilgisayar programına kaydedilir. Bu program her türün ayrı ayrı analizinin istenmesine ve metrik veya İngiliz sisteminin seçilmesine göre altı ayrı sonuç üretir. Ayrıca sonuçları daha iyi anlamak amacıyla sonunda bir sonuç için hız-zaman-seyir diren ci grafiği çizilmiştir.
Özet (Çeviri)
DETERMINATION OF ROAD RESISTANCES AND VEHICLE DATA PREPARATION FOR DYNAMOMETER SIMULATION SİMÖLATİON SUMMARY In this study, the road furces for the velude, movedas linear motion, have been deteriminated bya com puter programme. The purpose of the study is to set the vehicle datas for the chasis dynamometer. Setting the road load forces are effected to the vehicle by the equipments during the experiment of the chasis dynamometer. After the experiment, the results may not be perfect but they will be acceptable. In this thesis, the chasis dynamometer practice will not be done. It will be only set the parameters required for that practice. In this thesis, firstly, it has been informations about the road load forces and has been explained how they have been occurred. The coastdowm test is realized at the flat surface as linear motion. So, it has not be paid aftention for acceleratin resistance occurred by speed-up or slow down and it has not be pasd attention for the slope resistance occurred by the slope of the road. Mostly it has been paid more atten tion for the wind resistance occurred by air forcis. It is accepted that the rolling resistance are the same for four whell when the rolling resistance is deter minated. Briefly, this prepared thesis has two stafes. In the first stage, it is done a coastdown witha vehicle. The recommended coasdown practice provides uniform testing procedures for measuring the road load forces on a vehicle as a function of vehicle velocity and for simulation of that roacl load force at 50 mph (80 km/h) on a chasis dynamemeter. vmThis procedure covers measurement of vehicle road load on a straight, level road at speeds less than 70 mph (113 km/h). All tools and instrumentations must be calibrated sensitive. The instrumentations used in this practice are as follows : 1- Speed-time-An. Instrument tomeasure vehicle speed as a function of elepsed time is used in this procedure. The accuracy of the instrument must be very goods. 2- Temperature- The temperature indicating devices must have a resalution of 1 C and an accuracy of + 1 C. The sensing elemant must be shielded from radiant heat sources. 3- Atmospheric Pressure- A barometer with an accuracy of 0.7 kPA is necessary. 4- Wind - Wind Speed and direciton during the test Should be continously monitored. Wind measurements should permit the determination of average longitudinal (and cross wind components to within (+ 1.6 km/h). 5- Vehicle Weight - Vehicle werght should be measured to an accuracy of + 5 kg peraxle. 6- Tire pressure - should be measured to an accuracy of + A kpa. The test materials used in this practice are also as follows. The test vehicle should be uniquely described on the vehicle-Road-test-data sheet. In particular, ony modifications from the normal configuration of the vehicle should be noted. IXDuring the test, the conditions are as follows 1- Ambient temperature - Tests should be conducted, at ambient temperatures between -1°C and 32°C. Data obtained at temperatures outside this range cannot be relrably adjusted t to standart canditions. 2- Fag- Tests may not be run during foggy concditions 3- Winds - Tests may not be anducted when wind speeds a verage more than 16 km/h (or when peak wind speeds are more than 20 km/h. The overage of the component of the wind velocity perpendicular to the test road maynot exceed 8 km/h 4- Road conditions - Roads must be dry, clean smaath and must not exceed 0.5 % grade, In addition, the grade should be constant and the road should be shraight since variations in grade or straightness can segnif icantly affect results. The road surface should be. Concrete br rolled asphalt (or lgulvalent) in good condrtions since rough roads can signif icastly affect rolling resis tance. 5- Coastdown speed range. The range of speeds over which the vehicle is coasted should be as long as passible cansidering the length of the starghalway. The speed interval must include 80 km/h and should incilude the range of 100-40 km/h Before the test, the vehicle should be prepared. The preparation should as follows. 1- The test vehicle should have accumulated a minumum of 500 km prior to testing. The tires should have accumu lated a minumum of 160 km and should have at test %75 of the original thread depth remaning. In addition, ifa twin rail dynamometer is to be used, the drive axles tires should have a minumum of lh, at 80 km)h on the dynamometer rolls before conducting the dynamometer road load simulation portion of this procedure. All tire break in should be performed on the test vehicle or under load conditions simular to these imposed by test vehicle. 2- Vehicle Check-m. The following items should be compared to manufactures ve comenda tions and recorded on the vehicle road Test data zhcet prior to the test.a) Tiretype, seza ünd cold in flation pressure b) 'tfhell size, canditions and presence of wheel covers c) Broke Adjusment d) Lubricants in the drivetrain and in the non-driving wheel bearings. e) Vehicle suspension heights. 3- The speed-time measuring device and other necessary equipment must be in stalled so thet they donot hinder vehicle operation ar alter the operating of the vehicle. 4- Pre-test weight-The weight of the vehicle pnor to testing should be appropriçte for the vehicle repsesented; for example~consideration should be given to the effect of the added weight of the test instrumentation. 5- The pressure-Inflate the tires of the test vehucle to the manufacturer's recomended cold inflation pressure, corrected for the temperature difference (.fany) between the vehicle tires anel test area. The tire pressure should be increased 1 psi for each 13°C that the vehucle preparation area temperature is asave the test area tem perature or for each celsius degree. Revard the ectual inflation pressure and preparation area temperatuer on the vehicle Road Test data sheet. 6- Vehicle frantal Area-The vehicle frantal area must be known, measured or estimated and the value recoro- led on the vehicle Road Test Data Sheet. 7- Vehicle Warm-Up-The vehicle must be driven a minumum of 30 min at an average speed of 80 km/h immedia tely pri orto the test. At the end of the worm-Up period and prior to the stest of data acquisition, brietly stop the vehicle and rotate the steening wheel from lock to lock. Briefly, duning the test the follouring items should be done. 1- A minumum of 10 runs are made in amternating directions. The runs must be paired for the data reduction process in order to reduce error. XI2- The vehicle windows must be closed. At the start of each rum, accelerate the vehicle to a speed 8 km/h above the lugh point of the coastdown speed range, start the recerding exuipment, and shuf into neutral and let the engine idle. The vehicle clusteh must be engaged. Ata speed less than the lower point of the coastdown Speed range, stop the recording equipment, engage the transmission and prepare for the nextrun. 3- While coasting, lane changes should beavoided xf at all possible. If hecessary, they should be done as slowly as posible and over a distance of at least a half kilometer if such a gradual change cannot be made, abort the run. 4- Record the direction and number of each run in such a way that the speed time data can be seperated by run number. Record the ambient temperature and atmosp heric, pressure after the worm-up and after the test. Average the two values to determine the vaue to be used in the data reduction. The total wind and either the wind direction or the crosswind compenent of the total wind must be recorded. The wind guantities should be recarded, scresed for gusts exceeding the ambrent condition. Limits and avera ged. Record the results on the vehicle Road Test Data Sheet. 5- After the coastdown run, weight the vehicle to determine the vehicle test weight ormass. Include the weight of the fifth wheel driver, and all instrumentation used. 6- Measure each axle except with the fifth whell in the operating position and off the scale. During the test, there is a data reduction section This section prescribes the technigue for analyzing a set of coastdown data and the correction factors amplayed in the determination of the coefficient of the road load force equation. These corrected coefcients are used to calculate the time reguired to freely decelareet from 88 to 72 km/h an a chasis dynomometer. The coefficients of the road load force equation are determined for each individual V(+) coastdown and are then averaged over all pairs of coastdowns in each data set. Corrections are applied for wind, for temperature Xlldependen a of rolling resistance and for the density- dependence of aerodynamic elarg. The corrected coeffici ents are then used to construct the vehicle force-velocity equation characteristics of the vehicle under standard ambient conditions with no wind. Thrs force is then cor rected for inertial difference between the road test configuration and the dynamometer test figuraiton and the resul tant foree is used to calculate the time to coast from 88 to 72 km)h on a chasis dynamometer. After the test, xt should be done that if the resul tant datas are acceptable or not by data acceptability critena. Experience has shown that the criteria of this section are necessory and sufficient to provide accurate and precise test results. Data which exceed these criteria generally arise from wind gusts ordnver inputs which violate the assumption that the forces on the vehrele are depicded. Analyze each individual coastdown V(+) in the set of paired runs. A computer programme whicle performs this task applied with a sumple data set and the corresponding output. Using the equation, compare each indiridual V(+) trace and ıtz analytical counterpart V(fo,f2,t). If the roat-mean-square difference exceeds 0.40 km)h an any individual run, discard that run and the paired run in the opposite direction if less than three pairs comply with this criterion, the test run in invalrd. The standard deviation of eu the fo must be less then UN or %5 of the mean. If thes value is exceeded, discard the run and its pair with fo farthest from the mean and recompute the standard deviation until complrance is obta ined oruntil the remaining paris number lest than three. The standart deviation of al the f2 must be less than 0-011 N or %3 of the mean-if this value is exceeded, discard the run and its pair with f2 farthest from the, mean and recompute the standord deviation until compliance is obta ined or until the remaining Paris number less than three. If less than these pairs remain, the test run is invalid. Average f o ' s and f2's of all remaining runs to determine an fo and f2. The average fo and f 2 values must now be corrected to a standard set of ambient conditions. The standard conditions are; Temperature-20 C, Atmospheric pressure- Xlll98.2 k.Pa, Zero wind, The effect of humidity on air density- may be ignored. After deing all of the conditions given above the chasis dynamometer simulation of the vehicle road load is realized. This portion of the procedure, covers meansurement of total load on the vehicle as a function of dynamometer absorber horsepower when the vehicle is mounted on a chesis dynamometer. This procedure is written to determine the total load on the vehicle at 80 km/h. It may also be extended to determine the load on the vehicle at other speeds. All outputs vecorded during the test put in a computer programme. This programme is printed in quic basic. It produces six seperate results (output) acording to the unit systems and analysis of pairs. Also, xnorder to know better the results the speer tiem and road load forces duagram is drawn for an output. xxv
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