Patent Grant
11448141
This is a US national phase patent application that claims priority from PCT/FI2018/050925 filed 14 Dec. 2018, that claims priority from Finnish Patent Application No. 20176153, filed 22 Dec. 2017.
The present invention relates to a method of generating power and to power generating system.
In a gas turbine the first zone is exposed to temperature produced in a combustion chamber. Temperature of input gas to the gas turbine therefore restricts efficiency of the gas turbine. In a piston engine combustion is periodic which allows use of very high temperatures during combustion. However the reciprocating pistons and crank mechanism restrict running speed of a piston engine.
A typical engine system of the prior art consists of a fuel tank and a combustion engine. An internal combustion engine comprises a set of cylinders with a corresponding set of reciprocating pistons. One of the problems associated with the above arrangement is that the moving pistons and other moving parts have to be constantly lubricated with oil which has a significant impact on running temperature of the combustion engine. Consecutively, the running temperature is a significant factor when considering the efficiency. The moving parts require constant lubrication and thus the above mentioned engine withstands running temperature of less than 100 degrees Celsius without a significant deterioration of durability. Large portion of the produced heat is waste heat which in relatively low temperature which in turn makes it difficult to utilize the waste heat for energy production or other purposes.
U.S. Pat. No. 2,095,984 (H. Holzwarth) discloses an explosion turbine plant. The explosion turbine plant comprises an impulse rotor, pistonless explosion chambers for generating explosion gases and nozzles for expanding and directing the gases to a rotor being driven exclusively by intermittent puffs of said gases.
An object of the present invention is thus to provide a method and a system for implementing the method so as to alleviate the above disadvantages. The objects of the invention are achieved by a method and a system which are characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on the idea of arranging a combustion chamber outside a gas turbine and providing compressed air to the combustion chamber in order to carry out a combustion process in controlled and optimal conditions and use residue heat from the process. A heat source is used for boiling a liquid to achieve high pressure gas flow. Said gas flow is used for powering a turbocharger providing compressed air into the combustion chamber and/or for rotating the gas turbine. The heat source can be for example an external heat source, internal heat source, auxiliary heat source or any combination thereof.
An advantage of the method and system of the invention is that the controlled combustion process enables timed cyclical combustion which produces high average temperature. Pistons and crank mechanism are not needed. During the timed cyclical combustion pressure rises which reduces need for raising the pressure with a compressor which would need mechanical energy. According to the present invention, heat is exhausted from the system in relatively high temperature similar to a typical gas turbine. This high temperature exhaust creates favourable conditions for utilizing the exhaust heat and in addition available heat sources are utilized efficiently.
In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which
Referring to a simple example of
The system can also comprise a turbocharger 60, preferably a high pressure turbocharger, which turbocharger 60 is preferably powered with circulation 64 of fluid which is boiled using turbocharger heat exchanger 62. Instead of a turbocharger, a pressure wave supercharger can also be used. The boiling causes rapid increase in volume and/or pressure during phase change from liquid to gas. The heat needed for boiling the fluid can come from an external heat source 65, internal heat source, auxiliary heat source or a combination of heat sources thereof. The heat can be in form of a flow of heated fluid and/or exhaust from turbine 22 can be circulated through the turbocharger heat exchanger 62. Depending on the fluid used in circulation 64 powering the turbocharger 60, the boiling point of the fluid can be altered and external heat sources having output temperature even below 100° C. can be utilized. The turbocharger 60 increases air flow and pressure of air input 68 and the compressed air flow from the turbocharger 60 can be directed into the combustion chamber 10 or mixed into an output flow from the combustion chamber 10 flowing into the turbine 22. In an embodiment, the compressed air flow from the turbocharger 60 is input into an air chamber 27. Similar turbocharger arrangement can be used with any other embodiment of this disclosure.
Preferably the combustion inside the combustion chamber is deflagration combustion, not detonating combustion. Detonating combustion is an unwanted phenomenon as the pressure tends to rise to levels which can damage the system, especially controlled valves. Deflagration combustion is fundamentally different from detonation combustion which is unwanted in the context of the present power generating system.
The electric generator system also comprises a combustion chamber 10 which is arranged to receive compressed air from the compressor 24, air chamber 27, the air tank 32 and/or turbocharger 60 and fuel from a fuel tank 30 to initiate a combustion process. The compressed air is released from the air tank into the combustion chamber 10 by means of a controllable valve. Preferably the turbocharger 60 provides compressed air into the combustion chamber via a controllable valve. The compressed air, either from the turbocharger or the air tank, can be preheated before entering the combustion chamber with a heat recovery unit 40 which conveys heat from the combustion chamber to the compressed air. A regenerator can be used after the last compressor to heat up the compressed air before it is fed to the combustion chamber or to a by-pass duct which bypasses the combustion chamber. The regenerator may use waste heat from e.g. exhaust gas or combustion chamber for heating up the compressed air. The compressed air may also be preheated with other means, for example electrically with a resistor, when the system is started and the combustion chamber is at room temperature.
In an embodiment the system comprises one or more air chambers 27, each comprising a cylinder defining a volume inside it and a movable piston for changing the volume inside the cylinder, the volume being defined by the cylinder and the piston. The cylinder comprises input and output for air and said input and output are preferably controlled by one or more valves. The piston preferably comprises a valve, such as a clap valve or a flap valve, for enabling a flow of air in to the space defined by the cylinder and the piston. The cylinder preferably comprises one or more air ducts on it or in its walls for heating or cooling the cylinder and its contents by running hot or cold air, respectively, through the one or more air ducts. In this case hot air means hotter than the cylinder and cold air means colder than the cylinder. Compressed air from the compressor or from any stage of the serially connected compressors can be arranged to flow into the one or more air chambers. In an embodiment the system comprises one air chamber for each stage of serially connected compressors so that a flow of compressed air from each compressing stage is arranged to flow into a dedicated air chamber. In an embodiment the air pressure in a single air chamber can be raised gradually by arranging a flow of compressed air after each stage of serially connected compressors to said air chamber.
The air chambers can be operated in steps which comprise cooling down the air chamber, filling the air chamber gradually, heating up the air chamber and its contents, and finally, exhausting the compressed and heated air from the air chamber. The process repeats itself in a cycle having a certain cycle time. The heated air from the air chamber is exhausted preferably via heat exchanger to the combustion chamber. The heat exchanger can be a part of the air chamber or in connection with the air chamber. In an embodiment the air ducts of the cylinder of the air chamber form the heat exchanger.
The cooling step in the operation of the air chamber can be realized by arranging a flow of a fluid such as steam or ambient air or some other gas through the air chamber or through the air ducts of the air chamber. The cooling air can be in atmospheric pressure, i.e. approximately 100 kPa. The cooling step may take for example 7.5% or 6 to 10% of the time of the cycle, for example 9 seconds in a 120 second cycle.
In the filling step each air chamber is filled with air from dedicated compressing stage or in case of a single air chamber, it is gradually filled with air from one or more compressors until a desired pressure within the air chamber is reached. The input valve to the air chamber is opened and compressed air is arranged to flow into the air chamber. The gradual filling is preferably achieved by arranging a flow of compressed air from more than one stage of serially connected compressors. The desired pressure may vary but it is higher than the atmospheric pressure. In an embodiment the desired pressure can be for example at least 1.5 Mpa, 2 Mpa, 3 Mpa, 4 Mpa or some other pressure. The filling step may take for example less than 1% or 0.5 to 2% of the time of the cycle, for example 1 second in a 120 second cycle.
The heating step is realized by arranging a flow of hot air, e.g. from a heat exchanger, through the air ducts of the air chamber. The heating of the air chamber and thus the air within the air chamber further increases the pressure of the air within the air chamber. The heating step may take for example 40% or 30 to 60% of the time of the cycle, for example 50 seconds in a 120 second cycle.
In the exhausting step the output valve of the air chamber is opened and the compressed and heated air is arranged to flow into the combustion chamber. Preferably the heated air flows through a heat exchanger 25 before entering the combustion chamber. The exhausting of the compressed and heated air may be facilitated with the piston of the air chamber. The exhausting step may take for example 50% or 40 to 60% of the time of the cycle, for example 60 seconds in a 120 second cycle.
Fuel is released or pumped from the fuel tank and injected into the combustion chamber or mixed with air before introduction to the combustion chamber. The fuel is preferably diesel or liquid natural gas (LNG). In an embodiment, the fuel is gasoline, natural gas, ethanol, biodiesel or a mixture of two or more the preceding fuels. In an embodiment, the fuel comprises hydrogen and carbon monoxide mixture which is a by-product of a soda recovery unit. In an embodiment water or steam may be injected with fuel into the combustion chamber. In an embodiment the fuel comprises coal dust or brown coal dust as such or mixed to natural gas, diesel or some other suitable fuel.
The fuel injected into the combustion chamber ignites due to high pressure and temperature inside the combustion chamber or it is ignited by a dedicated ignition system. The high pressure in the combustion chamber is arranged by releasing air from the air tank to the combustion chamber. In addition to the preheating, the heat of the combustion chamber heats up the released air inside the combustion chamber and builds up even higher pressure. The ignition may be continuously triggered by a dedicated energy source or when the system is started and the combustion chamber has not yet reached its running temperature. The dedicated energy source for ignition can be e.g. an ignition coil, a condenser, a pre-combustion chamber, a glow plug, a pre-glow arrangement, a heater arrangement, plasma ignition and laser ignition. In an embodiment the system comprises an antechamber or a pre-combustion chamber. A fuel mixture can be ignited in the pre-combustion chamber to initiate the combustion process. The combustion process produces heat which heats up the combustion chamber and keeps the combustion process running by heating the fuel and the compressed air which are introduced into the combustion chamber. In an embodiment the ignition is also used during the combustion cycle after the system is started. In an embodiment the heat recovery unit 40 or other means of heat extraction is used to convey heat from the combustion chamber or combustion process to water or steam and generate high pressure steam. The high pressure steam is injected into the combustion chamber between the expansion phases of the combustion process. The steam is injected in short, high pressure pulses and the amount of pulses between two expansion phases may be for example 1 to 10, 2 to 8, 3 to 6 or some other amount, such as 4, 5, 7 or 8.
In an embodiment the system comprises means, such as heat exchangers, for producing heat to a district heating system. Some of the thermal energy that the electric generator system produces can be extracted from the system and transferred with heat exchanger to heating water of a district heating system. This combined production of electrical and thermal energy raises the overall efficiency of the system.
In an embodiment the system comprises means, such as heat exchangers, for using the thermal energy of the electric generator system to run an absorption cooling system. Some of the thermal energy that the electric generator system produces can be extracted from the system and transferred with heat exchanger to absorption cooling system which in areas of warm climate may raise the overall efficiency of the system.
The combustion chamber 10 is preferably a hollow container with input means for fuel and compressed air and an output for combustion products i.e. exhaust gas. The inputs and the output are controllable and may be closed and opened in specific phases of a combustion cycle in order to build up pressure into the combustion chamber before the ignition of the fuel and to expel combustion products after the ignition. Input and output can be understood as an inlet and an outlet, respectively, but the terms input and output are used throughout this text.
One or more valves can be used to control flow to and from the combustion chamber. In an embodiment one or more of the input and/or output valves are so called radial valves i.e. located radially around the combustion chamber cover. The input valves can be fixed to an inclined position to the combustion chamber i.e. not perpendicular to the combustion chamber wall. In an embodiment one or more input valves functionally connected to the combustion chamber 10 for controlling the combustion process are fixed to an inclined position to the normal of the combustion chamber wall so that an input of gas produces a controlled whirl of gas to the combustion chamber. The inclined position of a valve produces a whirl of gas in the combustion chamber when the gas is injected through the inclined valve. This type of whirl can be controlled with the inclined valves whereas random whirls produced by perpendicularly positioned valves are very difficult if not impossible to control. The input valves can be used to control the whirl by selecting suitable inclination angles and/or by timing openings of the valves.
The combustion process in the combustion chamber is a cycle process which at least resembles Diesel cycle. Preheated compressed air from the air tank is introduced into the combustion chamber and fuel is injected into the combustion chamber until the air-fuel mixture ignites. Unheated or preheated compressed air from the turbocharger 60 can be introduced to the combustion chamber prior to introducing said compressed air from the air tank or both can be introduced simultaneously. Said turbocharger 60 can raise the pressure inside the combustion chamber to a certain level, such as 200 to 600 kPa or 300 to 500 kPa, or higher, so that less air is needed from the air tank which lowers energy consumption of the compressor 24. The combustion of the air-fuel mixture expands its volume so the combustion products and the compressed air are expelled through the output when output valve is opened. Running speed of the combustion cycle is controlled by controlling the input and output valves. The running speed may be chosen freely within certain limits which are defined by the properties of the system. Such properties that may limit the running speed may be for example operation speed of the valves, the air pressure in the air tank, fuel type, etc. However, the running speed may be adjusted for optimal performance in each system because it is not restricted by moving pistons or similar physical limitations of moving mass.
The combustion chamber has preferably a simple form, most preferably a sphere or a cylinder, for enabling a quick, clean and complete combustion process. The simple form enables higher running temperatures which increases efficiency and decreases the amount of harmful particles and gases produced during the combustion process. In an embodiment, the combustion chamber 10 has an active part in which gas flows are controlled with the described valves. Fuel is also input to the active part, ignited in the active part and most of the combustion process takes place in the active part. In addition to the active part, the combustion chamber also comprises a passive part which has different flow characteristics than the active part. The combustion process is finished off in the passive part.
In an embodiment, the combustion chamber comprises one or more input valves and one or more scavenging valves. The combustion chamber has preferably a form designed to facilitate scavenging of the combustion chamber and ignition with whirl of air and/or gas mixtures prior to or during ignition. In an embodiment, operation of the valves can be improved with a cam shaft having one, two or more cams per valve during a single rotation of the cam shaft. This cam shaft arrangement with multiple cams in one rotation improves lifetime of the cams thereby reducing maintenance needs due to slower rotation speed of the cam shaft.
In an embodiment, the air introduced into the combustion chamber through said one or more scavenging valves is heated and preferably the air introduced into the combustion chamber through said one or more input valves is not heated. The heating of scavenging air is realized preferably with recuperation, i.e. heat recovery, of the combustion chamber. Preferably, the combustion chamber is surrounded by a casing defining an air gap between the combustion chamber 10 and said casing. As fuel is combusted in the combustion chamber, air in the air gap is heated and can be used for scavenging. Also other internal and external sources of heat can be used for heating the scavenging air. For example, compressed air from the air tank or from the compressor can be transferred to the scavenging valves through the air gap between the combustion chamber and its casing. Thus, the scavenging air is heated and its volume (or pressure) increases during heating and less scavenging air has to be produced with the compressor. This improves efficiency of the system by reducing work done by the compressor. When the air fed through the input valves to be used in combustion process is not heated, the expansion during combustion is greater than with heated air. This also increases efficiency of the system.
In an embodiment, the combustion chamber 10 comprises an open pre-combustion chamber which is in directly in connection with the combustion chamber, i.e. without a tight passage between the pre-combustion chamber and the combustion chamber. The pre-combustion chamber of this embodiment is formed of a recess or a hollow within the combustion chamber. The pre-combustion chamber has a fuel input valve for introducing fuel into the pre-combustion chamber. The fuel in the pre-combustion chamber is ignited which initiates combustion in the combustion chamber as the combustion rapidly spreads from the pre-combustion chamber. Said pre-combustion chamber is preferably located opposite to input(s) of fuel and/or air to the combustion chamber.
Use of the open pre-combustion chamber increases ignition energy by first igniting the air-fuel mixture within the pre-combustion chamber which then ignites the air-fuel mixture within the whole combustion chamber. Since the systems of the present disclosure are all based on a pistonless combustion chamber, the air-fuel mixture experiences turbulence which, in the context of this disclosure, can not be controlled with a piston and this can lead to unstable combustion. The increased ignition energy achieved with the described pre-combustion chamber solution facilitates ignition and combustion thus ensuring more stable combustion.
The combustion chamber is arranged to function in high temperatures. In addition to the simple form, also the material of the combustion chamber has to withstand high temperatures without significant deterioration of performance or durability. The material of the combustion chamber may be ceramic, metal, alloy or preferably a combination of two or more materials. For example, the combustion chamber may comprise an alloy encasing with a ceramic inner coating. The alloy encasing withstands high pressure and strong forces while the ceramic inner coating withstands high surface temperatures. The construction of the combustion chamber is preferably arranged to withstand running temperature of 400 degrees of Celsius. In an embodiment the combustion chamber is arranged to withstand running temperature of 500, 600, 700 or 800 degrees of Celsius or more. The combustion chamber itself does not comprise any moving parts so it is relatively simple task to design the combustion chamber to withstand high temperatures. The moving parts that experience the highest thermal stress are the valves at the input and output ports of the combustion chamber. The input valves are not subjected to such high temperatures as they are cooled during each inlet cycle by incoming air. However, there are valves readily available that are designed to operate in these temperatures and therefore it should be relatively easy task to design and realize a durable valve system.
The output of the combustion chamber 10 leads a stream consisting of the combustion products and the compressed air from the combustion chamber into the turbine 22. Due to the high pressure in the combustion chamber, the stream is expelled with high velocity when the output is opened. The expelling of the combustion products may be enhanced by having the output and the air input open simultaneously for a certain period of time. The turbine 22 comprises a rotor which rotates when the stream flows through the turbine. The rotating rotor drives the transmission 20 which in turn drives the power shaft 51 and the compressor 24 as stated earlier. The stream is guided to exhaust pipe 90 after the turbine and the exhaust gas 98 is released from the system. The power shaft 51 provides the output of the system and it can be connected to e.g. a drivetrain of a vehicle or an electric generator for converting the mechanical work into electric energy.
The combustion chamber 10 is preferably a separate unit outside the turbine 22. The combustion products expelled from the combustion chamber 10 are guided to the turbine 22 with a pipe, tube or some other channel connecting the combustion chamber 10 and the turbine 22. In an embodiment the system comprises multiple combustion chambers. In that case each combustion chamber has a pipe, tube or some other channel connecting that combustion chamber to the turbine 22. Preferably the multiple combustion chambers are arranged to expel their combustion products sequentially, i.e. not all at the same time, to provide a steadier flow of combustion products to the turbine 22. In an embodiment, the steadier flow to turbine 22 is accomplished with short, high pressure steam pulses which are injected into the combustion chamber between the expansion phases of the combustion process. In an embodiment two or more combustion chambers are arranged to expel their combustion products simultaneously in order to produce a high peak of energy to the turbine.
In an embodiment a generator driven by the power shaft 51 feeds an electric storage system which comprises one or more capacitors, super capacitors or batteries for storing the electrical energy produced by the generator. This type of system can be used in vehicular applications for producing and storing electrical energy for electrical motors of a vehicle. Also in vehicular applications the system can comprise an additional air tank or it may be connected to an air tank of the vehicle using it as a hybrid air tank for two purposes. The additional air tank may be filled with compressed air from a compressor of the electric generator system or a compressor of the vehicle. Energy from braking of the vehicle can be converted in to compressed air with the compressor of the vehicle and stored in to the additional air tank. The vehicle may also comprise an exhaust brake which can also be connected to the additional air tank for increasing the pressure of the additional air tank. The compressed air of the additional air tank can be supplied to the compressors of the electric generator system where the pressure of the air is increased to final desired level.
Now referring to
The steam is arranged to flow from the steam tank 34 to the heat recovery unit 40. The heat recovery unit 40 is in thermal connection with the combustion chamber 10 so that the combustion chamber heats up the heat recovery unit in which the heat is conveyed to the steam flowing through the heat recovery unit. The heat recovery unit may be a separate unit having a thermal connection to the combustion chamber or it may be a fixed part of the combustion chamber. In an embodiment the heat recovery unit may even a pipework inside the combustion chamber or tubing on the surface of the combustion chamber. When the heat from the combustion chamber is conveyed to the steam flowing through the heat recovery unit, the steam rapidly heats up and expands. The steam flow is then directed to the turbine 22 wherein the steam flow rotates the rotor of the turbine 22 simultaneously with the combustion products and compressed air which are expelled from the combustion chamber 10 into the turbine 22.
In an embodiment a heat pump can be used to produce steam. Heat pumps are known to be effective when needed temperature difference is small. A heat pump is therefore a good alternative for adding thermal energy to water which is at or near its boiling point. For example an air-to-water or water-to-water heat pump can be used for producing steam from water that is preheated to near or at its boiling point. The steam production can be assisted with other energy sources, including those already mentioned, in addition to the heat pump. In an embodiment steam of exhaust flow is condensed into water and the heat released from the condensing is used as a heat source for the heat pump. The temperature where the condensing takes place depends on the pressure of the exhaust gas and steam. Said temperature is 100 degrees Celsius in atmospheric pressure but in higher pressure it can be for example as high as 200, 300, 400 or even 500 degrees Celsius. The heat pump uses the heat to vaporize water for providing fresh steam to the system. In an embodiment heat provided by one or more intercoolers of the system is used as a heat source for the heat pump.
In an embodiment the heat recovery unit 40 is replaced with heat insulating material and time-dependent steam injections to the combustion chamber 10 maintain a stable running temperature of the combustion chamber. The time-dependent steam injections are preferably short, high pressure steam pulses injected into the combustion chamber between expansion phases of the combustion process. The injected high pressure steam pulses need only a reduced amount of steam due to their short pulse type length. After injection the steam exits the combustion chamber and enters into the turbine 22.
In an embodiment the system comprises an additional burner for increasing the amount and/or the temperature of the steam in the system. The burner preferably uses the same type of fuel as the rest of the system. The fuel is burned in the burner for producing heat which then heats steam and/or the burning fuel heats water to produce steam. The additional burner can be used in systems which do not produce enough “waste heat” to produce an adequate amount of steam. The system is also adapted to use other external heat sources and thus heat as such or converted into compressed air or steam can be input to the system from external sources. The external source can use the same fuel or a different fuel than the combustion chamber of the system. Examples of usable heat energy from external sources can be e.g. waste heat of a heavy machine process, waste heat of a vehicle's engine or brake system, geothermal energy, etc. In an embodiment where the system produces excess heat, a portion of the heat produced by the system can be converted in an external process e.g. in Rankine process or Stirling process to mechanical work. The use of the additional burner ensures that a desired amount of steam in a desired temperature and pressure can be achieved.
In an embodiment, the steam is not directed into the same turbine 22 as the combustion products. In that embodiment the system comprises a second turbine which is dedicated to the steam stream while the (first) turbine 22 is dedicated to the stream of combustion products and compressed air. The stream of combustion products and compressed air may even be arranged to flow through an additional heat exchanger after the turbine 22 to heat up the steam stream before that stream enters the second turbine. The arrangement of the second turbine may be similar to known combined cycle power plants.
From the turbine a stream of steam, compressed air and combustion products flows through the heat exchanger 42 to the condenser 50 wherein the steam is condensed into water and the compressed air and the combustion products are guided out of the system through exhaust pipe 90. In the embodiment of the second turbine the stream of combustion products and compressed air is arranged to flow through heat exchanger 42 directly to exhaust pipe and the steam stream is arranged to flow through the heat exchanger 42 and the condenser 50 to the water tank 36.
Condensing water from the exhaust flow may cause accumulation of impurities to the system which is undesirable. In an embodiment this is solved by feeding the condenser with fresh, atmospheric air from which relatively clean water can be condensed to the system.
The water condensed from the steam and/or from the atmospheric air flows into the water tank 36 or is pumped in there. An ion exchanger 52 may be arranged between the condenser 50 and the water tank 36 for purifying the water before it enters the cycle again. The water tank 36 accumulates water which is then guided or pumped to the heat exchanger 42. The heat exchanger conveys the heat from the stream of steam, compressed air and combustion products to the water flowing through the heat exchanger. The heat of the heat exchanger vaporizes the water into steam which is then guided to flow back into the steam tank 34. From the steam tank 34 the high pressure steam can be released in short bursts to create short, high pressure pulses to the combustion chamber.
In an embodiment the system also comprises an adjustable nozzle and a valve in connection with the ejector 12 and the output of the combustion chamber 10 for adjusting the expelling of combustion products from the combustion chamber 10. The nozzle has a certain design and a form which may be altered. The nozzle is within the ejector in a by-pass flow of the steam flowing from the heat recovery unit 40 to the turbine 22. The form of the nozzle has a significant impact to the expelling of the combustion products from the combustion chamber when the valve in the output is open. By altering the form of the nozzle the expelling of the combustion products may be increased with help of the by-pass flow of the steam.
In an embodiment a portion of the combustion products, i.e. the exhaust gas, is guided to a low temperature/pressure region of the turbine 22 or to a low pressure turbine when the exhaust gas is exhaust from the combustion chamber. An ejector or ejectors 14a, 14b can be omitted in this embodiment since the pressure in suction side is higher than the pressure in low temperature/pressure region.
Each combustion chamber 10a, 10b comprises one or more inputs 101, 102 which can be controlled with or without input valves and one or more outputs 111, 112 which can be open or controlled with output valves. The inputs and the outputs may be controlled without valves by controlling the pressure of the inputs and outputs because gases tend to flow from a higher pressure region to a lower pressure region. In an embodiment at least some of the inputs and outputs are controlled with gas vibrations or oscillations instead of valves. Movement of gas in a pipeline tends to oscillate with a frequency or a plurality of frequencies which is/are specific to the pipeline and the gas, so called eigenfrequencies. The pulse action is created by the periodic combustion and fortified by the eigenfrequencies of the flow system. Specific oscillation frequencies can be exploited by controlling the periodic combustion process to match the frequency of the specific gas oscillation so that these amplify each other. In an embodiment the combustion cycle is matched with the specific oscillation frequency of the compressed air flowing in the system. In an embodiment valve actuation is optimized to harmonize with the desired periodical operation of the pulse turbine. In an embodiment the combustion cycle, the specific oscillation frequency of the compressed air flowing in the system and a specific oscillation frequency of the steam flowing in the system are all matched to the same phase so that they amplify each other. The specific oscillation frequencies of the steam and the compressed air flows can be matched with pipeline design. In an embodiment the combustion cycle is matched with the specific oscillation frequency of the compressed air flowing in the system and with the specific oscillation frequency of the steam flowing in the system but the specific frequencies of the steam and the compressed air are not matched with each other. Preferably the flow system is optimized such that the flow losses are minimized.
In an embodiment the system comprises compressors connected in series to produce high pressure compressed air to the combustion chamber. A typical way is to feed compressed air from the first compressor to the second compressor and from the second compressor to the third compressor, and so on. The pressure of the compressed air builds up in each compressor stage and finally the compressed air from the last compressor of the series of compressors is released to the combustion chamber or to the air chamber. This is energy consuming as the amount (mass) of compressed air is the same in each compressing stage. A compressing stage can be a single compressor or a number of compressors in parallel connection i.e. each having common input and output. In an embodiment serially connected screw compressors can share a common shaft so that successive compression stages are partitioned along the common shaft and intercoolers are provided between each compression stages to extract heat from the compressed gas. Compressed air from any compression stage can be directed to flow into a combustion chamber 10, air chamber, air tank 32 or some other part of the system. In an embodiment a portion of the mass of the compressed air is released to the combustion chamber and the remaining portion of the mass of the compressed air is released to the following compressor in the series of compressors. The pressure within the combustion chamber rises gradually as the compressed air is released to the combustion chamber between compressing stages. Heat can be extracted from the compressed air between the compressing stages by using one or more intercoolers. Also the amount of air to be compressed diminishes in subsequent compressing stages as part of the air is released to the combustion chamber between the compressing stages. A plurality of pressure tanks can be used for storing compressed air in various pressures between atmospheric pressure and the highest pressure from the last compressor. A further advantage is that the gradual air feeding allows the other inputs to be fed to the combustion chamber during a desired pressure. For example the combustion chamber could first receive a first release of compressed air, then a fuel input, then a second release of compressed air, then a steam input and finally a third release of compressed air to a desired final pressure. The order and timing of the inputs can be optimized based on the system variables.
In an embodiment the combustion chamber is arranged to work in two alternating cycles. The first cycle may be any of the combustion cycles, i.e. a topping cycle, where fuel is fed to the combustion chamber as described within this document. The second cycle is a cooling cycle, i.e. a bottoming cycle, wherein the combustion chamber is cooled by means of arranging a flow of fluid, such as ambient air, steam or some other gas, through the combustion chamber. Cooling the combustion chamber transfers thermal energy from the combustion chamber to the fluid flowing through the combustion chamber and thus makes the combustion chamber less warm. Both cycles may take an equal amount of time. In an embodiment the first cycle is longer than the second cycle or the first cycle is shorter than the second cycle.
In an embodiment each combustion chamber comprises an output controlled by a main exhaust valve 111. In an embodiment each combustion chamber comprises two outputs, one output being controlled by a main exhaust valve 111 and one output being controlled by an auxiliary exhaust valve 112. In an embodiment each combustion chamber comprises an open output which is not controlled by valve. In an embodiment each combustion chamber comprises an input 101 for fuel. In an embodiment each combustion chamber comprises inputs 101, 102 for fuel and pressurized air. In an embodiment each combustion chamber comprises inputs for fuel, pressurized air and steam. In an embodiment each combustion chamber comprises inputs for one or more of the following: fuel, pressurized air, steam and water. The steam may be produced at least partially using waste heat of the combustion process of the system. In an embodiment, the steam is injected in the form of short, high pressure steam pulses which are injected into the combustion chamber between the expansion phases of the combustion process. In this embodiment, the exhaust valves may be omitted as the pressure and temperature conditions of the combustion chamber are controlled with the steam pulse injections. In an embodiment steam is injected into combustion chamber and/or to the ejector 12 and to the turbine 22. When both combustion chambers outputs are closed, steam can be injected directly into the ejector 12. In an embodiment, an ORC turbine or a Stirling engine can be used after the heat exchanger for cooling the exhaust gas and steam in a temperature range of about 200 degrees Celsius.
A combustion cycle in the system of
In an embodiment including the main exhaust valve, after closing the main exhaust valve 111 the ejector can be sprayed with liquid water and/or water vapour i.e. steam via valve 103 which raise the pressure in the ejector 12, for example to 6.5 MPa. At a certain pressure in the ejector 12, for example 6.5 MPa, the main exhaust valve 111 of the second combustion chamber 10b opens and releases combustion products to the ejector 12 and from there to the turbine 22. At the same time the secondary exhaust valve 112 of the first combustion chamber 10a is kept open to ventilate the residue combustion products from the first combustion chamber 10a. The ventilation can be enhanced by introducing pressurized air or steam via the inputs 101, 102 to the combustion chamber. The secondary exhaust valve 112 may lead the residue combustion products to the turbine 22 via one or more second ejectors 14a, 14b. In an embodiment steam is injected into combustion chamber and/or to the ejector 12 and to the turbine 22. When both combustion chambers outputs are closed, steam can be injected directly into the ejector 12. In an embodiment a single second ejector can comprise multiple inputs so that it can be used with two combustion chambers. Once the first combustion chamber 10a is ventilated and the pressure has dropped to a sufficiently low level, for example to 2, 1, 0.5 or 0.2 MPa, the secondary exhaust valve 112 is closed and the next cycle of the combustion cycle can begin.
In an embodiment the second ejector 14a, 14b is arranged to receive motive steam or motive gas via input 114. The motive gas is preferably pressurized water vapour for example in 6, 8 or 10 MPa pressure. The motive gas is directed through the second ejector 14a, 14b and discharged to the ejector 12 via valve 104. When the motive gas goes through the second ejector it creates a suction effect drawing residue combustion products from a combustion chamber 10a, 10b when output valve 112 connecting the combustion chamber to the second ejector is open. The valve 104 is preferably a control valve. The throughput and/or opening direction of the valve 104 can be adjusted. In an embodiment all excess steam produced within the system can be fed to the turbine via the valve 104 and/or the second ejector 14a, 14b.
In an embodiment a back flow from the turbine 22 using an intermediate steam tapping can be introduced to a third ejector. The back flow or the intermediate steam from the turbine may comprise steam or combustion products or a mixture of steam and combustion products which are introduce to the third ejector. The pressure of the intermediate steam at the third ejector is raised to a sufficient level by using valves and introducing gas such as water vapour to the third ejector. The steam and the combustion products increase the volume of the gas and decrease the temperature of the gas. The mixture of gases is introduced from the third ejector to the ejector 12 for example via the second ejector 14a, 14b and valve 104, or to some other input valve of the system. In an embodiment, an output using an intermediate steam tapping can also be introduced right after the heat exchanger.
In an embodiment the turbine is arranged to rotate a by-pass fan in an aviation application for example replacing turbofan engines of commercial airplanes. In an embodiment the system comprises an oxygen tank connected to the combustion chamber and controlled with a valve. The combustion chamber can be used as a combustion chamber of rocket engine using rocket fuel from the fuel tank and oxygen from the atmosphere in the lower atmosphere so that the oxygen from the oxygen tank can be used in the upper atmosphere where the amount of oxygen is not sufficient for the combustion.
The output to the turbine can be maintained in an elevated level with the injection of water, steam and air. This elevated level is illustrated with dashed line 201 in
In an embodiment the pressure within the ejector 12 is kept always over for example 2, 3, 4 or 5 MPa. In an embodiment the amount of injected water, steam and air and point of time at which those are injected are determined based on measured quantities of the system. Such measured quantities can be for example temperature, pressure, humidity, gas composition, state of a valve or some other process quantity. Said quantities can be measured with e.g. sensors. In an embodiment the amount of injected water, steam and air and point of time at which those are injected are determined based on the phase of the combustion cycle. The time dependent injection of water, steam also increases the reliability of the turbine 22 by controlling the temperature of the gas which is introduced to the turbine 22. The injection of water and steam lowers the average temperature of the gas introduced to the turbine and therefore it allows for higher pressure (and thus higher temperature) to be used in the combustion chamber.
In an embodiment the power generator system is used together with a turbocharged combustion engine. The power generator system can feed supplemental energy, for example exhaust from the combustion chamber 10, to the turbocharger of the combustion engine which can be beneficial in three ways. First, the pressure ratio of the turbocharger can be controlled regardless of running speed (rpm) and/or load of the combustion engine. This is beneficial in controlling emissions and pollutants of the combustion engine and it also improves load response of the combustion engine. Also the compressor belonging to the pulse turbine system can be used for supplying the input of air. Second, the system may provide output of mechanical power from a shaft of the turbocharger or the turbine of the power generator system which provides an additional power which depends on the amount of additional energy fed to the system. Third, the power generator system can use at least part of the exhaust flow of the combustion engine s an energy source. Also the input of air to the combustion chamber can be arranged with air supply system of the combustion engine as such or supplemented with additional air supply pump, such as Roots blower. Also a compressor of the power generator system can be used for supplying the input of air. In an embodiment, the exhaust from the combustion chamber 10 flows first through a supplemental turbine which e.g. rotates an electric generator for converting the energy of the exhaust into electrical energy. The electrical energy can be stored in batteries and/or consumed by operating a compressor or other electrical devices, Said compressor can compress air e.g. to be fed into the combustion chamber. After the supplemental turbine the exhaust flow can e.g. power the turbocharger with its remaining energy. After that, the exhaust flow has lost most of its energy in form of pressure and/or velocity but heat of the exhaust can still be extracted with a heat exchanger to heat e.g cabin of a vehicle.
As described in detailed description about
In an embodiment, circulation 64 is an open circulation in which water or some other fluid is boiled and the resulting steam or some other gas first powers the turbocharger 60. The turbocharger 60 uses some of the energy of the gas flowing through the circulation, effectively decreasing the pressure of the gas. The gas flow of the circulation 64 after the turbocharger can be led to turbine 22 and to possible subsequent low pressure turbine s after that. In an embodiment, circulation 64 is an open circulation in which water or some other fluid is boiled and the resulting steam or some other gas is led directly to turbine 22 and to possible subsequent low pressure turbine after that. In an embodiment either a continuous or intermittent burner is located between the turbine 22 and a subsequent low pressure turbine. An air dispersion nozzle can be used in the burner.
In an embodiment the compressed air flow from the turbine, or another compressed air flow, steam flow or gas flow, is ejected into the conduit connecting combustion chamber 10 and the turbine 22. An ejector is preferably used for directing said compressed air flow, steam flow or gas flow towards the combustion chamber 10 or the turbine 22. Said compressed air flow, steam flow or gas flow towards the combustion chamber 10 facilitates pressure build up within the combustion chamber as said flow restricts output from the combustion chamber 10. Said compressed air flow, steam flow or gas flow towards the turbine 22 increases flow through the turbine 22, thereby increasing output of the turbine 22.
In an embodiment, a power generating system has
a turbine 22 in connection with one or more compressors 24 for converting energy fed to the turbine 22 into mechanical energy of a rotatable power shaft and to compress air with one or more compressors 24,
a combustion chamber 10 arranged to receive fuel from a fuel tank 30 and compressed air to initiate a cyclic combustion process comprising a compression phase and an expansion phase and to output combustion products into the turbine 22 for rotating the rotor of the turbine and thereby rotating the power shaft, and
one or more fuel input valves 101 for providing the fuel to the combustion chamber 10,
one or more air input valves 102 for providing the compressed air to the combustion chamber 10,
a control unit for controlling said one or more fuel input valves 101 and the one or more air input valves 102 in order to control the combustion process. It is characterizing for this embodiment that the combustion chamber 10 comprises a recess defining a pre-combustion chamber for increasing ignition energy to ignite a fuel mixture in the pre-combustion chamber to initiate the combustion process in the combustion chamber 10. Preferably the pre-combustion chamber comprises one or more air input valves for providing air to the pre-combustion chamber and one or more fuel input valves for providing fuel to the pre-combustion chamber. Preferably the pre-combustion chamber is located opposite to at least one of the one or more air input valves of the combustion chamber and/or opposite to at least one of the one or more fuel input valves of the combustion chamber. Preferably the system comprises a turbocharger arrangement disclosed in this disclosure. Any feature presented within this disclosure may be used in the system of this embodiment.
It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.
While the present invention has been described in accordance with preferred compositions and embodiments, it is to be understood that certain substitutions and alterations may be made thereto without departing from the spirit and scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20176153 | Dec 2017 | FI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FI2018/050925 | 12/14/2018 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/122514 | 6/27/2019 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3796045 | Foster-Pegg | Mar 1974 | A |
| 20150260053 | Eramaa | Sep 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 2017085359 | May 2017 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20200392911 A1 | Dec 2020 | US |
