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Technical Paper

Specific Analysis on Electric Vehicle Performance Characteristics with the Aid of Optimization Techniques

In this paper the effects of design parameters on the performance of an electric vehicle are presented. A detailed mathematical model was established using governing vehicle dynamics equations. Ideal energy storage systems were modelled with high order polynomial equations and represented graphically in the form of Ragonne curves. This was followed by the development of a simulation program which was utilized to optimize the design parameters, such as specific energy and mass of the storage system, electric motor operating voltage and electric drive final gear ratio. The effects these parameters had on the objective functions, namely range, acceleration, specific consumption, battery cycle life and cost were investigated. The outlined optimization process is presented in a manner which enables the designer to optimize electric or hybrid electric vehicles.
Technical Paper

Optimization of Natural Gas Storage System for Vehicles Equipped with Direct Injection System

In our earlier papers on thermocontrolled tank storage system, we presented the basic concept of storing natural gas and the results from optimization of the vessel design. In this paper we are presenting optimization results of the entire storage system, assuming that the vehicle is running in a certain pre-scheduled pattern. Two kinds of vehicles have been considered for investigation, a city bus with a continuous running schedule and a car with a short run-park schedule. The initial waiting time, parking time, safe pressure ratio and range of the two vehicles have been investigated and then optimized to define the performance requirements.
Technical Paper

Investigation on Dynamic Response of a Closed Fuel Injector in a Diesel Engine at Low Speed

Contemporary high speed diesel engines require a compromise regarding the size of fuel nozzle orifices which should be small enough to assure a good fuel atomization at low engine speed, and large enough to provide the engine with high fuel dose at maximum power. Calculations were made to predict the dynamic response of a closed diesel injector within its unstable operation range. The pressure in the seat chamber under the needle was established as the key factor to simulate the injector's behaviour. It was measured at different flow conditions and used in calculations. After applying an optimization method, it was possible to predict how the design parameters of an injector should be changed in order to obtain the best dimentional configuration which improves the fuel atomization at low engine speed.
Technical Paper

Optimization of Electronically Controlled Injectors for Direct Injection of Natural Gas in Diesel Engines

An attempt is made to develop solenoid operated injectors for diesel engines, to inject natural gas directly into the combustion chamber at high pressure. These new injectors have the size of conventional diesel injectors with small but powerful solenoids located in the former spring chamber, and the spring is moved to a location closer to the nozzle. To provide fast opening and closing of the nozzle, a multiobjective optimization method is used to select the design variables of the injector. The mathematical model used for optimization is developed with the help of experimental results obtained from the solenoid force measurements at transient conditions. The optimization results did show good dynamic performance of the injector, despite the use of a small size solenoid actuator.
Technical Paper

Simulation, Testing and Optimization of Natural Gas On-Board Storage System for Automotive Applications

To increase the operational range of the vehicle equipped with direct injection gas supply and to eliminate the problems associated with the cryogenic pumps, a composite high pressure vessel is proposed for use as a thermocontrolled tank in vehicles. The test results showed that the liquefied natural gas can be brought from atmospheric pressure to the high pressure required for direct injection in a reasonable time period. Based on these results a mathematical model for the heat transfer to the natural gas was developed and simulated. Three different aspects of gas storage, namely, the initial operational temperature, the gas to vessel mass ratio and the gas weight to vessel volume ratio have been investigated and formulated as objectives for optimization. Due to the presence of different conflicting objectives, the problem was formulated as a nonlinear multi objective optimization problem and then solved.
Technical Paper

Simulation, Testing and Optimization of a New Low Cost Electronic Fuel Control Unit for Small Gas Turbine Engines

The potential benefits of digital electronic controls, including increased flexibility and lower cost, have not yet been fully applied to the small gas turbine engines of remotely piloted vehicles. For these applications, the need for low cost is a strong factor in design. To address this situation, a new, simple and inexpensive electronically controlled metering system for small gas turbine engines is proposed. The system incorporates a diaphragm type valve keeping a constant differential pressure across a stepper motor actuated metering valve. To optimize the design, mathematical models were created for computer simulation. Experimental tests performed on a prototype showed that it can adequately meet the fuel schedules of small gas turbines. The simulation models were validated against the test results and were used in design optimization.