Power plants – Combustion products used as motive fluid
Reexamination Certificate
1999-05-07
2001-03-13
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
Reexamination Certificate
active
06199365
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a piezoelectric ignition device for a combustion system and more particularly to a device wherein the piezoelectric element is responsive to changes of pressure in the combustion system.
BACKGROUND OF THE INVENTION
Many combustion processes require either pilot flames or complicated controllers to control ignition and combustion. For example, a gas stove requires either a pilot light or an electric starter. Complex electronics control intermittent spark release in a gas turbine engine to regulate the stability of combustion. While piezoelectric materials have been developed for a variety of ignition systems, in most cases, generation of a voltage across the materials has been controlled almost independently of the flow of the material to be ignited.
For example, Home, in U.S. Pat. No. 5,375,585, teaches a piezoelectric igniter and safety valve for a gas stove. However, the safety valve is controlled by a thermocouple. The igniter is controlled by a knob connected to a valve and a metal striker. As the knob is turned, it first opens the valve, allowing gas to flow, and then causes the striker to hit a piezoelectric element. A voltage is produced across the piezoelectric element, which is then conducted to an electrode, whereat a spark is produced which ignites the gas. A similar process is disclosed by Nelson in U.S. Pat. No. 4,954,078. Nelson discloses an igniter for a propane torch or like device, wherein the igniter is contained within the torch. A valve is opened to permit gas flow, and a trigger is pressed to actuate a spring-loaded plunger which impacts a piezoelectric element. Suzuki, in U.S. Pat. No. 3,986,061, describes an ignition system for cigarette lighters and similar devices in which voltage is generated across a piezoelectric element in response to a bending stress. Again, this voltage is eventually used to generate a spark and ignite a combustible material.
Nelson, in U.S. Pat. No. 5,536,990, describes a system in which one combustion process initiates a subsequent process. The first process includes a detonation which impacts a piezoelectric element. The voltage generated across the element is used to initiate a second process.
SUMMARY OF THE INVENTION
The invention comprises an igniter that is activated by the fluctuation of the pressure in some part of a combustion system or process. The igniter exploits the piezoelectric properties of an element to generate the voltage, charge, and energy required for ignition in response to the pressure in the system or process. The piezoelectric element generates electrical energy in response to the mechanical energy supplied by the fluctuation in pressure in a certain part of the system or process. The electrical energy generated by the element is relayed to the combustion chamber of the system or process, where it can initiate or sustain combustion of liquids or gases. Ignition is thus achieved in response to the change in pressure in some part of the system or process.
In one aspect, this invention comprises an ignition device for a combustion system containing a piezoelectric element which can generate electrical energy in response to pressure. The electrical energy generated is sufficient to ignite a combustible material. The combustible material may comprise a liquid or plurality of liquids, a gas or plurality of gases, or a mixture of liquids and gases. For example, the system may ignite a chemical combustion process, turbine engines, or a propellant for space propulsion. A combustible material is introduced by means whereby a change in the amount of the material being introduced results in a change in pressure exerted on the piezoelectric element. This invention also comprises a piezoelectric element which, in response to pressure, generates enough electrical energy to ignite a combustible material. The piezoelectric element is electrically coupled to an igniter. The invention may further comprise a switch and a controller, which, by opening and closing the switch, controls the conduction of electrical energy from the piezoelectric element to the igniter. In addition, the invention may further comprise a capacitor, enabling ignition delay, or the ignition delay capability may be included in the controller.
This invention also comprises a combustion process comprising a feedline for introduction of a combustible material and means to increase the pressure on a piezoelectric element in response to the introduction of that material. In response to the increased pressure, the piezoelectric element generates enough electrical energy to ignite the combustible material. The invention also comprises means for conducting the electrical energy to an igniter whereat the combustible material is ignited.
The invention also comprises a method of igniting a combustible material. Material is introduced from a reservoir, resulting in a change in pressure applied to a piezoelectric element. In response, the piezoelectric element generates electrical energy sufficient to ignite the material, which is conducted to an igniter to ignite the combustible material. The invention may further comprise controlling the conduction of the electrical energy to the igniter.
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Pretorius Jacob van Reenen
van Schoor Marthinus Cornelius
Choate Hall & Stewart
Mide Technology Corp.
Rodriguez William
Thorpe Timothy S.
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