Search Results

This paper investigates the performance of a double actuator electronic fuel control unit, when installed on a gas turbine engine. The validated mathematical model of the unit is linked to a quasi-linear engine mathematical model. A combination of two operating modes of the unit is used to improve the fuel delivery characteristics. Acceleration and maximum speed governing of the engine are simulated. Two control strategies are investigated. In the first, the fuel flow rate and the engine speed are used as feedback signals. In the second, the N-Dot control, which eliminates the need for fuel flow feedback during engine acceleration, is studied.

There is a need in the gas turbine industry for an inexpensive fuel control unit for the new breed of high performance small gas turbine engines. To answer this demand, it is proposed to couple an automotive type fuel pump with a stepper motor driven in microstepping mode. The speed of the motor and the fuel flow rate can be controlled by the frequency signal from the computer. This concept is particularly well suited for the gas turbine engine fuel supply where the fuel pressure at low speed is low and the fuel leakage in the pump is not high. The stepper motor driven by a microstepping driver can reach high speeds of several thousands rpm. The unit can be installed inside the fuel, supply tank, as is the case with electric fuel pumps found in automobiles. Prototypes have been made and tested. Both steady state and transient response are showing an impressive performance of such an electronic fuel metering pump.

A new electronically controlled fuel system is proposed for direct injection of natural gas in diesel engine. It consists of the solenoid controlled injectors interfaced with a metering valve under stepper motor control. This system proved to operate well in different configurations with metering valve being located at various distances from the injector; two injectors interfaced by one metering valve were also tested. In all cases, the required maximum and minimum gas doses were obtained, either by the change of the metering valve flow area or the injector opening time. The gas dose was measured using a special closed chamber. The conclusions drawn from these tests were used for the proposal of improvement of the injector design in order to reduce its size and weight and obtain more reliable operational characteristics.

New regulations adopted by some North America states, to reduce pollution from vehicles, are forcing the auto-industry to introduce hybrid electric cars as a temporary solution, before the “clean” electric vehicles would become ready for consumer use. The FutureCar concept introduced by the USA government, in cooperation with the “Big Three” automotive manufacturers, is the first step to solve the future energy shortage and pollution problems associated with today's vehicles. The paper presents a proposal towards development of a low-cost, high efficiency and low emission mid-size car with an acceptable driveability. The choice of the IC engine, electric motor, drivetrain and control system are described. A demonstration project initiated in parallel should contribute to the validity of this proposal.

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.

Typical fuel metering systems for small gas turbine engines consist of a metering valve and a bypass valve which is maintaining a constant differential pressure across the metering valve orifice. The metering valve is operated by the compressor pressure signal and the bypass valve acts automatically. It is proposed to bring both the metering and the bypass valves under the control of two digital linear actuators. The first one would move the metering plunger according to the compressor pressure and the second would move the bypass plunger in such a way, that the differential pressure across the metering orifice would be maintained constant only during steady state engine operation. During the engine transient processes, however, it would be increased or decreased as required, to speed up the change in the nozzle flow rate and consequently the engine dynamic response.

A new family of low cost electronic fuel control units is being proposed for small gas turbine engines of remotely piloted vehicles and auxiliary power units. It has a modular design incorporating an electronically actuated metering valve which can be matched with various types of differential pressure valves controlling the pressure drop across the metering valve. Four different configurations are proposed: metering valve only, metering valve with diaphragm type differential pressure valve, metering valve with bypass valve and double valve configuration, the latter with a back-up capability. These configurations can satisfy various demands from gas turbine engine producers. Some components of automotive fuel injection system could be used to reduce the cost of these units as well as components from the DP-F2 fuel control which has been in production for a long time. This adds to the confidence of the reliability and durability of this new design.

Optimization of diesel injection system using computer aided design involves complex high speed, high pressure hydraulic transient process calculation. To find the fuel discharge characteristic from injector, the fuel pumping process is first computed based on the design parameters of the injection pump. Then, knowing the forward propagating pressure wave, the dynamic response of the injector is calculated resulting in the fuel discharge process. However, if the forward pressure wave could be precisely measured instead of being calculated, and then substituted into the computer program the total calculation procedure would be substantially reduced. In this paper, a computer controlled data acquisition system with high sampling rate was used to record the fuel pumping process in a specially made long pipe to avoid distortion by the reflected pressure wave. This method is convenient, quite accurate and can save the time of computer simulation.

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.

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.

A new concept of a semicryogenic tank for storage and supply of natural gas into the cylinders of an internal combustion engine is presented. It allows the gas to be pressurized before injection and uses the heat entering the tank as the means to evaporate the natural gas introduced in a liquid phase to the tank. To limit the heat transfer to the tank and the gas pressure increase, the semicryogenic tank has to be well insulated. However, it has to be also preheated to accelerate the gas pressure increase, as required. To maintain the right pressure and temperature of natural gas an electronic control of the semicryogenic tank is needed. The gas preheating system uses the waste heat of engine exhaust gases and, therefore, contributes to the increase of the thermal efficiency of the engine through the injection of hot natural gas.

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.

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.

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.

The Montreal area has a well developed aerospace industry with a continuous need for young engineers broadly educated in aircraft propulsion. To fulfil this requirement, three Montreal universities: Concordia University, École Polytechnique, and McGill University, with the cooperation of interested industrial enterprises, launched a joint Master of Engineering (Aerospace) program. It included several courses directly related to aircraft propulsion such as: Advanced Turbomachinery and Propulsion, Gas Turbine Design, Fuel Control Systems for Combustion Engines, Vibration Problems in Rotating Machinery, etc. They were supported by prerequisite basic courses. Some of these courses have also been made as electives to these undergraduate students in Mechanical Engineering Program who want to specialise in Aeronautics. The paper gives a more detailed description of courses and laboratories from the point of view of aircraft propulsion teaching.