Dissertations / Theses on the topic 'Brake efficiency'

The air hybrid engine absorbs the vehicle kinetic energy during braking, stores it in an air tank in the form of compressed air, and reuses it to start the engine and to propel a vehicle during cruising and acceleration. Capturing, storing and reusing this braking energy to achieve stop-start operation and to give additional power can therefore improve fuel economy, particularly in cities and urban areas where the traffic conditions involve many stops and starts. In order to reuse the residual kinetic energy, the vehicle operation consists of 3 basic modes, i.e. Compression Mode (CM), Expander Mode (EM) and normal firing mode, as well as stop-start operation through an air starter. A four-cylinder 2 litre diesel engine has been modelled to operate in four air hybrid engine configurations so that the braking and motoring performance of each configuration could be studied. These air hybrid systems can be constructed with production technologies and incur minimum changes to the existing engine design. The regenerative engine braking and starting capability is realised through the employment of an innovative simple one-way intake system and a production cam profile switching (CPS) mechanism. The hybrid systems will allow the engine to be cranked by the compressed air at moderate pressure without using addition starters or dedicated valves in the cylinder head. Therefore, the proposed air hybrid engine systems can be considered as a cost-effective regenerative hybrid powertrain and can be implemented in vehicles using existing production technologies. A novel cost-effective pneumatic regenerative stop-start hybrid system, Regenerative Engine Braking Device (RegenEBD), for buses and commercial vehicles is presented. RegenEBD is capable of converting kinetic energy into pneumatic energy in the compressed air saved in an air tank using a production engine braking device and other production type automotive components and a proprietary intake system design. The compressed air is then used to drive an air starter to achieve regenerative stop-start operations. The proposed hybrid system can work with the existing vehicle transmission system and can be implemented with the retro-fitted valve actuation device and a sandwich block mounted between the cylinder head and the production intake manifold. Compression mode operation is achieved by keeping the intake valves from fully closed throughout the four-strokes through a production type variable valve exhaust brake (VVEB) device on the intake valves. As a result, the induced air could be compressed through the opening gap of intake valves into the air tank through the intake system of proprietary design. The compressed air can then be used to crank the engine directly through the air expander operation or indirectly through the action of an air starter in production. A single cylinder camless engine has been set up and operated to evaluate the compression mode performance of two air hybrid concepts. The experimental results are then compared with the computational output with excellent agreement. In order to evaluate the potential of the air hybrid engine technologies, a new vehicle driving cycle simulation program has been developed using Matlab Simulink. An air hybrid engine sub-model and methodology for modelling the air hybrid engine’s performance have been proposed and implemented in the vehicle driving cycle simulation. The NEDC analysis of a Ford Mondeo vehicle shows that the vehicle can achieve regenerative stop-start operations throughout the driving cycle when it is powered by a 2.0litre diesel engine with air hybrid operation using a 40litre air tank of less than 10bar pressure. The regenerative stop-start operation can lead to 4.5% fuel saving during the NEDC. Finally, the Millbrook London Transport Bus (MLTB) driving cycle has been used to analyse the effectiveness of RegenEBD on a double deck bus powered by a Yuchai diesel engine. The results show that 90% stop-starts during the MLTB can be accomplished by RegenEBD and that a significant fuel saving of 6.5% can be obtained from the regenerative stop-start operations.

Магістерська дисертація містить пояснювальну записку на 91 сторінках формату А4, 40 ілюстрацій, 25 таблиці, 31 літературне джерело, 1 додаток. В даній роботі розглянуті ресурсні характеристики реверсивного п’єзоелектричного двигуна на прикладі двигуна РМ-20Я8. Головною характеристикою п’єзоелектричних двигунів, яка дозволяє порівняти їх з іншими електродвигунами є коефіцієнт корисної дії (ККД). Оцінка цього параметру для п’єзоелектричних двигунів досить складна, оскільки ККД залежить від конструкції цих двигунів, сили і кута притиску штовханів до ротора та матеріалу самого ротора. Але основним параметром, який змінюється в процесі ресурсних іспитів двигуна і від якого залежить його ККД, є зміна його моменту самогальмування. Саме тому в основі ресурсної моделі повинні бути покладені експериментальні залежності моменту самогальмування двигуна від кількості напрацьованих ним обертів. Об’єктом дослідження є ресурсні характеристики п’єзоелектричного двигуна, предметом дослідження - реверсивний п’єзоелектричний двигун. Досліджено ресурсні характеристики реверсивних п’єзоелектричних двигунів конкретного типу. Побудовано ресурсну модель ККД реверсивного п’єзоелектричного двигуна в основу якої покладено експериментальні залежності моменту самогальмування від кількості напрацьованих обертів. В результаті виконання дисертаційної роботи визначено елементи, що мають відношення до ресурсної надійності двигуна. Ресурсна модель залежності ККД п’єзоелектричного двигуна від моменту самогальмування дає можливість вдосконалити його ресурсні характеристики, забезпечивши цим самим надійність і раціональність використання таких двигунів.<br>The master’s thesis contains an explanatory note on 91 A4 pages, 40 illustrations, 25 tables, 31 literary sources, 1 appendix. This paper discusses the resource characteristics of a reversible piezoelectric motor using the example of the RM-20Y8 engine. The main feature of piezoelectric motors that compares them to other electric motors is the efficiency. The estimation of this parameter for piezoelectric motors is quite difficult, since the efficiency depends on the design of these motors, the force and the angle of pressure of the pushers against the rotor and the material of the rotor itself. But the main parameter that changes in the process of engine resource tests and on which its efficiency depends, is the change in its torque. That is why the resource model should be based on the experimental dependence of the moment of self-deceleration of the engine on the number of revolutions it has produced. The subject of the study is the resource characteristics of the piezoelectric motor and the subject of the study is the reversible piezoelectric motor. The resource characteristics of reversible piezoelectric motors of a particular type are investigated. A resource model of the efficiency of a reversible piezoelectric motor is constructed, which is based on the experimental dependences of the moment of self-deceleration on the number of revolutions worked. As a result of the dissertation, the elements related to the engine resource reliability were determined. The resource model of the dependence of the piezoelectric motor efficiency on the moment of self-deceleration makes it possible to improve its resource characteristics, thus ensuring the reliability and rational use of such motors.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.<br>Includes bibliographical references (leaves 106-108).<br>Locomotion assistive devices can be broadly classified as either being passive or powered. Both have been created to aid in the leg's generation of a ground reaction force which supports the torso during locomotion, yet their inherent design has limited their functional growth to date. While many differing gait simulations have demonstrated stable solutions for lossless gait cycles, passive orthoses only diminish the user's impediment, and though powered gait exoskeletons can augment strength and endurance, they are limited by their energy demanding actuators. In response to these two extremes, an energy efficient locomotion assist device was developed from the basis of lossless gait models that did not require external power, and augmented locomotion by harvesting the inherent energy associated with the gait cycle. The simplest anthropomorphic leg can be modeled with a peg-leg shank, a knee, a thigh and a point mass for the head, arms and torso. Using a tuned non-linear hardening torsion spring at the knee joint, the torso support that is required between the ground and pelvis for lossless gait simulations can be generated; allowing the close physical realization of the theoretical. It was found that a single torsion spring can generate the leg thrusts necessary for a realistic range of walking and running gait velocities without the addition of any external power. While frictional losses do inhibit the locomotion assist device's efficiency, since the device functions in parallel with the user's leg, any losses can be supplemented with minimal muscular activity. These results give strong indication that a new avenue of gait assistive and gait augmenting devices that require minimal actuation energy is feasible.<br>by Andrew Williams Carvey.<br>S.M.

Чередник, І. П. Проект вантажного автомобіля з дослідженням технологічного процесу відновлення головного гальмівного циліндру : випускна кваліфікаційна робота : 274 "Автомобільний транспорт" / І. П. Чередник ; керівник роботи В. М. Скляр ; НУ "Чернігівська політехніка", кафедра автомобільного транспорту та галузевого машинобудування. – Чернігів, 2021. – 138 с.<br>Робота охоплює в собі комплексний розрахунок параметрів автомобіля УРАЛ-4320, його параметрів, навантажень, потіжності двигуна, предавальних чисел коробки перемикання передач, визначення навантажень на двигун при рівномірному русі та ін. Визначення паливної економічності та розрахунок гальмівної системи автомобіля, що плавно перетікає в основний розділ роботи. Останнім розділом в роботі є процес дослідження відновлення головного гальмівного циліндру, що дозволяє нам, як власникам в експлуатації цього авто робити висновок, що тце здешевлює обслуговування та ремонт вантажівки. Для виконання розрахунків та графічної частини використовувались такі програми: “Компас 3D”,“Paint”, “Mathcad”.<br>Work includes a comprehensive calculation of the parameters of the car URAL-4320, its parameters, loads, engine power, gear ratios, determining the load on the engine with steady motion and not. Determination of fuel economy and calculation of the brake system of the car, which flows smoothly into the main section of the work. The last section of the master's work is the process of researching the restoration of the master brake cylinder, which allows us, as owners in the operation of this car to conclude that it is cheaper to maintain and repair the truck. The following programs were used to perform calculations and graphics: "Compass 3D", "Paint", "Mathcad".