This thesis deals with road loads, coastdown tests and evaluation of measured data. Thesis consists of two main parts: theoretical and computational. The first part describes road loads with focus on aerodynamic drag and lift force. In the second part, a software tool for processing the measurement per ISO 10521-1 is designed and lift force measured with running resistance method is calculated.

This thesis deals with the effect of the aerodynamic forces on a vehicle. It contains the description of the test run of the vehicle, the proposal on how to process the measurements, the processing of the measurements themselves, and the final assessment of the results as to their accuracy and the possibility of repeating the experiment. Furthermore, this thesis contains the comparison of the effect of the individual aerodynamic features on the race car.

This thesis deals with appraising aerodynamic characteristics of vehicle based on road testing, specifically on coastdown tests and straight-line tests.

Development of a fuel economy model for light-duty and heavy-duty vehicles is part of the Texas Department of Transportation’s “Estimating Texas Motor Vehicle Operating Costs” project. A literature review for models that could be used to predict the fuel economy of light-duty and heavy-duty vehicles resulted in selection of coastdown coefficients to simulate the combined effects of aerodynamic drag and tire rolling resistance. For light-duty vehicles, advantage can be taken of the modeling data provided by the United States Environmental Protection Agency (EPA) for adjusting chassis dynamometers to allow accurate determination of emissions and fuel economy so that compliance with emissions standards and Corporate Average Fuel Economy (CAFE) regulations can be assessed. Initially, EPA provided vehicle-specific data that were relevant to a physics-based model of the forces at the tire-road interface. Due to some limitations of these model parameters, EPA now provides three vehicle-specific coefficients obtained from vehicle coastdown data. These coefficients can be related back to the original physics-based model of the forces at the tire-road interface, but not in a manner that allows the original modeling parameters to be extracted from the coastdown coefficients. Nevertheless, as long as the operation of a light-duty vehicle does not involve extreme acceleration or deceleration transients, the coefficients available from the EPA can be used to accurately predict fuel economy. Manufacturers of heavy-duty vehicles are not required to meet any sort of CAFE standards, and the engines used in heavy-duty vehicles, rather than the vehicles themselves, are tested (using an engine dynamometer) to determine compliance with emissions standards. Therefore, EPA provides no data that could be useful for predicting the fuel economy of heavy-duty vehicles. Therefore, it is necessary to perform heavyduty coastdown tests in order to predict fuel economy, and use these tests to develop vehicle-specific coefficients for the force at the tire-road interface. Given these coefficients, the fuel economy of a heavy-duty vehicle can be calculated for any driving schedule. The heavy-duty vehicle model developed for this project is limited to pre-2007 calendar year heavy-duty vehicles due to the adverse effects of emissions components that were necessary to comply with emissions standards that went into effect January 2007. / text

Orientador: Prof. Dr. Pedro Carajilescov / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2016. / Os estudos sobre transitórios em bombas de refrigeração de um reator são importantes para a análise de segurança de uma central nuclear. Uma análise precisa do decaimento da vazão de refrigerante no circuito primário durante uma eventual falha das bombas principais de refrigeração, evento conhecido como coastdown, é requerida tanto para pelos critérios de segurança estabelecidos como para a especificação e fabricação das bombas. Neste trabalho, o estudo é realizado utilizando um modelo matemático para simular transiente de vazão durante o período de coastdown em reatores nuclear do tipo PWR, no qual a equação de conservação da quantidade de movimento linear é utilizada de uma forma adimensional. Informações detalhadas sobre as características da bomba centrífuga não são necessárias. Como resultado, o decaimento da vazão é determinado a partir da razão entre dois parâmetros: a energia cinética do fluido refrigerante no circuito e a energia cinética armazenada nas partes rotativas da bomba. Em estudos anteriores, essa razão, denominada razão de energia efetiva, é mantida constante durante todo o evento de coastdown. Neste trabalho, foram propostas três correções para a melhoria dos resultados, a saber: a consideração de uma razão de energia efetiva variável durante o transitório, das variações na eficiência da bomba durante o transitório e das perdas mecânicas internas devido ao atrito e viscosidade no interior da bomba para baixas rotações. Para implementação do modelo proposto foi desenvolvido um programa, denominado de COREP-flow, cujos resultados foram comparados com dados experimentais obtidos na literatura. As comparações mostraram uma melhoria na reprodução desses resultados em relação aos modelos de referência. No Modelo 5 desenvolvido neste trabalho, os resultados obtidos apresentaram menor discrepância quando comparados com os dados experimentais. Para vazões superiores a 20 % da vazão inicial, a vazão de refrigerante calculada pelo Modelo 5 apresentou uma discrepância relativa média de 1,8 %, enquanto que o modelo proposto por Gao et al. (2011) apresentou uma discrepância relativa média de 4 %. Para vazões de refrigerantes inferiores a 20 % da vazão inicial, a discrepância relativa média para a vazão de refrigerante do Modelo 5 foi de 10,3 %, enquanto que a de Gao et al. (2011) foi de 50,6 %. / The transient studies in reactor cooling pumps (RCPs) are important for the nuclear power plant security analysis. An accurate analysis of flow coastdown in the primary cooling loop system during an eventual failure of the RCPs is required both for the established security criteria, and for the pumps specification and manufacturing. In this work, the study is performed using a mathematical model to simulate the flow rate transient in PWR reactor type during flow coastdown period, in which the conservation of linear momentum equation is non-dimensional. The detailed information of the centrifugal pump characteristics are not required. As result, the coastdown is determined from the ratio between two parameters: the kinetic energy of the coolant in the circuit and the kinetic energy stored in the rotating parts of the pump. In previous studies, the ratio, known as energy ratio, is kept constant during the whole coastdown period. In this work, it was proposed three corrections aiming the improvement of the results, to know: the consideration of an energy ratio variable during the transient, of the efficiency variations of the pumps during the transient and of the internal mechanical losses due to friction and viscosity inside the pump for low rotations. For the model implementation, a program was developed, the COREP-flow, whose results were compared to the experimental data obtained in the literature. The comparison showed an improvement in the reproduction of the results in relation to the reference models. In Model 5, developed in this work, the obtained results presented less discrepancy when compared to the experimental data. For flow rates higher than 20% of the initial flow, the coolant flow calculated by Model 5 presented a mean relative discrepancy of 1.8%, while the model proposed by Gao et al. (2011) presented a mean relative discrepancy of 4%. For coolant flow rates less than 20% of the initial flow, the mean relative discrepancy for the coolant flow of Model 5 was of 10.3%, while the one from Gao et al. (2011) presented a mean relative discrepancy of 50.6%.

An operating vehicle requires energy to oppose the subjected driving resistances. This energy is supplied via the fuel combustion in the engine. Decreasing the opposing driving resistances for an operating vehicle increases its fuel efficiency: an effect which is highly valued in today’s industry, both from an environmental and economical point of view. Therefore a lot of progress has been made during recent years in the area of fuel efficient vehicles, even though some driving resistances still rises perplexity. These resistances are the air drag Fd generated by the viscous air opposing the vehicles propulsion and the rolling resistance Frr generated mainly by the hysteresis caused by the deformation cycle of the viscoelastic pneumatic tires. The energy losses associated with the air drag and rolling resistance account for the majority of the driving resistances facing an operating vehicle, and depends on numerous stochastic and ambient parameters, some of which are highly correlated both within and between the two resistances. To increase the understanding of the driving mechanics behind the energy losses associated with the complexity that is rolling resistance, a set of complete vehicle tests has been carried out. These tests were carried out on the test track Malmby Fairground, using a Scania CV AB developed R440 truck equipped with various sensors connected in one measurement system. Under certain conditions, these parameters can allow for an investigation of the rolling resistance, and a separation of the rolling resistance and air drag via explicit subtraction of the air drag from the measured traction force. This method is possible since the aerodynamic property AHDVCd(β) to some extent can be generated from wind tunnel tests and CFD simulations. Two measurement series that enable the above formulated method of separation were designed and carried out, using two separate measurement methods. One which enables the investigation of the transient nature of rolling resistance as it strives for stationarity, where the vehicle is operated under constant velocities i.e. no acceleration, and one using the well established method of coastdown, where no driving torque is applied. The drive cycles spanned a range of velocities, which allowed for dynamic and stationary analyses of both the tire temperature- and the velocity dependence of rolling resistance. When analysing the results of the transient analysis, a strong dependence upon tire temperature for given constant low velocity i.e. v ≤ 60 kmh−1 was clearly visible. The indicated dependency showed that the rolling resistance decreased as the tire temperature increased over time at a given velocity, and vice versa, towards a stationary temperature and thereby rolling resistance. The tire temperature evolution from one constant velocity to another, took place well within 50 min to a somewhat stationary value. However, even though the tire temperature had reached stationarity, rolling resistance did not; there seemed to be a delay between stationary tire temperature, and rolling resistance. The results did not indicate any clear trends for v ≥ 60 kmh−1, where the results at v = 80 kmh−1 were chaotic. This suggests that some additional forces were uncompensated for, or that the compensation for air drag was somehow wrongly treated at higher velocities. Several factors ruled out any attempts at proposing a new rolling resistance model. These included: the chaotic results for v = 80 kmh−1, the delayed rolling resistance response upon tire temperature stabilization, and the lack of literature support for the observed tendency. The results from the coastdown series on the other hand, showed good agreement with a dynamical model suggested in literature. The stationary temperature behaviour for the considered velocity range at assumed constant condition is also supported in literature. Finally, an investigation of the aerodynamic property AHDVCd inspired by ongoing work in ACEA (European Automobile Manufacturers’ Association), was carried out assuming both zero and non-zero air drag at low velocities. The results indicated surprisingly good agreement with wind tunnel measurements, especially when neglecting air drag at low velocities: as suggested by ACEA. / För att övervinna de motstånd som ett fordon utsätts för under drift krävs energi, vilket levereras genom förbränningen av bränsle. Genom att minska de körmotstånd som ett fordon utsätts för under drift, kan man öka dess energieffektivitet. Denna potential är idag högt värderad i fordonsindustrin, både ur ett miljömässigt och ekonomiskt perspektiv. På senare år har stora framsteg gjorts inom området energieffektiva fordon, men fortfarande råder det förvirring kring de energiförluster som förknippas med luftmotstånd Fd och rullmotstånd Frr, där luftmotståndet skapas av den omkringliggande viskösa luften, medan rullmotståndet genereras av hysteresen som uppstår när fordonets viskoelastiska pneumatiska däck utsätts för deformation. De energiförluster som förknippas med luft- och rullmotstånd motsvarar den största delen av de motstånd som ett fordon påverkas av, och beror på en mängd stokastiska och yttre parametrar, varav vissa är starkt korrelerade både inom och mellan nämnda motstånd. För att förbättra förståelsen kring dessa energiförluster, med fokus på förståelsen av rullmotstånd, har ett antal helfordonstest genomförts. Dessa genomfördes på provbanan Malmby Fairground med en R440 lastbil från Scania CV AB, utrustad med en mängd sensorer sammankopplade i ett mätsystem. Det uppbyggda mätsystemet möjliggjorde samtida mätningar av bl.a. drivande moment, motorvarv, fordonshastighet, däcktemperatur, omkringliggande lufts hastighet och dess riktning. Under specifika förhållanden kunde dessa parametrar möjliggöra analys av rullmotstånd genom en explicit subtraktion av luftmotstånd från den uppmätta drivande kraften. Denna metod är möjlig tack vare en förhållandevis bra modell av ekipagets aerodynamiska egenskap AHDVCd(β), som generats från vindtunneltest och CFD simuleringar. Två körcykler som möjliggjorde ovan formulerade separation designades och genomfördes. Dessa använder två skilda mätmetoder, varav den ena möjliggör analys av rullmotståndets övergående förlopp från dynamiskt till stationärt genom att hålla konstant hastighet. Den andra studerade det dynamiska förloppet genom den väletablerade metoden utrullning, dvs. utan något drivande moment. Dessa körcyklar genomfördes, för ett antal hastigheter, vilket möjliggjorde analys av både hastighets- och däcktemperaturberoendet hos rullmotstånd, under dynamiska såväl som stationära förlopp. Analysen av rullmotståndets dynamik i strävan mot stationära förhållanden visade på ett starkt temperaturberoende vid låga hastigheter dvs. v ≤ 60 kmh−1. Beroendet visade på att rullmotståndet avtog med ökande däcktemperatur och vice versa, tills dess att en någorlunda stationär temperatur för given hastighet uppnåtts. Däcktemperaturen stabiliserades till ett nytt stationärt värde inom 50 min från att hastigheten ändrats. Resultaten tyder dock på att även om stationär däcktemperatur uppnåtts finns det en fördröjning i rullmotståndets tidsspann innan rullmotståndet stabiliserat sig. För högre hastigheter, dvs. v ≥ 60 kmh-1, var dock inga klara trender synliga, varken i hastighet eller temperatur och resultaten vid v = 80 kmh-1 var kaotiska. Detta antyder att man missat att kompensera för någon kraft vid höga hastigheter, alternativt att man på något sätt kompenserar fel för luftmotståndet vid högre hastigheter. Flera faktorer hindrade försök att föreslå någon ny rullmotståndsmodell. Dessa faktorer inkluderar det kaotiska resultatet vid v = 80 kmh-1, tidsfördröjningen mellan stationärt rullmotstånd och däcktemperatur samt att resultatet för antagna stationära värden inte finner stöd i litteraturen. Resultatet från utrullningsprovet överstämmer dock bra med tidigare föreslagen dynamisk modell, samt att resultaten av beteendet hos stationär temperatur för olika hastigheter även de överensstämmer med och finner stöd i litteraturen. Slutligen har en studie kring den aerodynamiska egenskapen AHDVCd, inspirerad av pågående arbete inom ACEA (European Automobile Manufacturers’ Association) utförts både med antagandet av ett noll- skilt och med ett försumbart luftmotstånd vid låga hastigheter. Resultatet visar på en överraskande god överensstämmelse med vindtunnelmätningar, framför allt under antagandet av försumbart luftmotstånd vid låga hastigheter i enlighet med förslagen metod från ACEA.

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