The present invention relates to an internal combustion engine operating on the basis of the direct-power-cycle, and more particularly to an improvement on the reduction of the compression loss and heat loss from internal combustion engine.
The present invention can be used in the field of transportation vehicle and power generation.
The present invention is an internal combustion engine operating with the direct-power-cycle for improving the fuel efficiency to above 30% and power-to-weight ratio of the engine system.
The fuel efficiency of the present invention is increased by performing a three-stage compression and a control airflow to the combustion chambers by both adjusting the compression-capacity of the intermediate-compressor and shifting the actuation-timing of the servo-intake-valve.
The three-stage compression of the present invention comprises the initial-compression-process, the intermediate-compression-process, and the final-compression-process.
The initial-compression-process is performed by a turbocharger system because the turbocharger system cannot provide a constant pressure boost to the ambient air, however, the turbocharger system is capable of recovering about 35% of the remained expansion energy in the exhaust gas through the turbine, thereby outputting a flow of low-boost air of about 1.5 bar to 5 bar from the compressor of the turbocharger system during the initial-compression-process.
The intermediate-compression-process is performed by an intermediate compressor of a screw type, a rotary type, a gear type, or scroll type, wherein the compression-capacity (compression speed) is adjusted by a transmission means, such that the intermediate-compressor takes in said flow of initial-boost air and outputs a flow of intermediate-boost air to the cooling-tank, since this intermediate-compression-process can adjust the compression-capacity in a boarder range, the air-pressure in the cooling-tank is maintained at a preset optimum pressure in any load condition (about 5 bar to 20 bar depending on the cooling-tank volume and the material strength); a built-in pressure sensor is included in the cooling-tank or the distributor-manifold to feedback the airflow data tot the engine control unit.
The cooling-tank lowers the temperature of the intermediate-boost air with the built-in cooling-circulation to prevent the knockings during the final-compression-process.
For the cost consideration, the gasoline or similar fuel can be supplied to mix with the intermediate-boost air in the distributor-manifold with a fuel injector or a carburetor, thereby forming an air-fuel mixture before entering the combustion chambers.
For the best performance with highest fuel efficiency, a GDI (gasoline direction injection) injector should be employed in each combustion chamber as the fuel supplying means (most of the disclosure of the present invention will be explained with the GDI injector).
The final-compression-process is performed in the combustion chamber, wherein the maximum compression pressure in the combustion chamber is about 200% to 400% of the air-pressure of the cooling-tank in heavy load operation, whereas the maximum compression pressure of the combustion will be about 150% to 200% of the air-pressure of the cooling-tank in medium load operation.
In comparison to the split-cycle engine or other two-stroke engines, the conventional engine has a high energy loss resulted from compression-stroke, the present invention provides a constant high power output with the minimum compression loss, and the power output is determined by the setting of the compressor-transmission and the servo-intake-valve, instead of the conventional throttle or variable valve timing system.
In comparison to the split cycle engine or other two-stroke compound engines, the present invention will have a much higher power-to-weight ratio and a lower manufacturing cost.
It is the main objective of the present invention to provide a controlled-compression direct-power-cycle engine that can operate with a high fuel efficiency and light weight engine structure.
It is the second objective of the present invention to provide a controlled-compression direct-power-cycle engine that can control the engine power output by shifting the open-time and the shut-time of the servo-intake-valve to adjust the actual-pressure-ratio of the final-compression-process.
It is the third objective of the present invention to provide a controlled-compression direct-power-cycle engine that can minimize the energy loss of air-compression by multi-stage compression, wherein the initial-compression-process is performed with a compressor of the turbocharger system, the intermediate-compression-process is performed with an intermediate-compressor, and the final-compression-process is performed with the pistons of the combustion chambers.
It is the fourth objective of the present invention to provide a controlled-compression direct-power-cycle engine that adjusts the compression capacity of the intermediate-compressor with transmission means to maintain a preset optimum pressure in the cooling-tank, thereby compensating the unstable air-pressure of initial-boost air from the compressor of the turbocharger.
It is the fifth objective of the present invention to provide a highly efficient air-assistance system for storing the brake power as a compressed air in the cooling-tank with the intermediate-compressor during the braking process.
The pistons in the combustion chambers of the direct-power-cycle will perform a down-stroke and an up-stroke, wherein the TDC of the piston (top dead centre) is referred as 0 degree or 360 degree of the crankshaft reference angle, the BDC of the piston (bottom dead centre) is referred as 180 degree of crankshaft reference angle.
The direct-power-cycle consists of the initial-compression-process, the intermediate-compression-process, the cooling-process, the servo-intake-process, the final-compression-process, the combustion-process, and the turbine-exhaust-process; wherein the servo-intake-process, the final-compression-process, the combustion-process and the turbine-exhaust-process are performed in the combustion-chambers of the direct-power-cycle engine.
The ratio of the maximum compression pressure of the combustion chamber to the air-pressure of the cooling-tank is referred as the actual-pressure-ratio of the final-compression-process, wherein this actual-pressure-ratio is controlled by shifting both the actuation-timing and the shut-timing of the servo-intake-valve.
As shown in
The servo-intake-process, the final-compression-process, the combustion-process and the turbine-exhaust-process is performed in the combustion-chamber, wherein a circular process chart in
The initial-compression-process is the first process of the direct-power-cycle, which is to compress the ambient air with the compressor 122 of the turbocharger system, thereby providing a flow of initial-boost air at about 1.5 bar to 5 bar into the intermediate-compressor 120.
The intermediate-compression-process is the second process of the direct-power cycle, which is to compress said flow of initial-boost air with an adjustable compression capacity to supply a controlled flow of intermediate-boost air to the cooling-tank 130, wherein said adjustable compression capacity is controlled with the compressor-transmission 125.
The engine control unit will detect the air-pressure in the cooling-tank 130 with a pressure sensor; if the detected air-pressure is lower than a preset value in the ECU, the gear ratio of the compressor-transmission 125 will be shifted to a higher gear ratio to raise the compress capacity of the intermediate-compressor 120, thereby maintaining a preset optimum pressure in the cooling-tank 130; if the detected air-pressure is higher than a preset value in the ECU, the gear ratio of the compressor-transmission 125 will be shifted to a lower ratio to reduce the compression capacity of the intermediate-compressor 120, or the compressor-transmission 125 may disengage with a clutch for disconnecting the coupling gear from the crankshaft of the combustion chamber to temporally stop the operation of the intermediate-compressor 120, thereby maintaining a preset optimum pressure in the cooling-tank 130.
The main purpose of the compressor-transmission 125 is to provide an adjustable compression capacity of the intermediate-compressor 120, which will compensate for the unstable pressure boost from the compressor 112 of the turbocharger (the operational range of the turbocharger is relatively limited in comparison to the intermediate-compressor 120).
The air-pressure of the cooling-tank 130 is maintained at a pressure between 5 bar and 20 bar depending on the tank volume and material strength of the cooling-tank; in this embodiment, the air-pressure of the cooling-tank can be assumed at a constant pressure of about 10 bar in medium power output operation and high power output operation.
The cooling-process is the third process of the direct-power-cycle, which is the process to cool down the intermediate-boost air in the cooling-tank 130, wherein the cooling-tank 130 consists of cooling-circulation pipelines or cooling-fins (air-cooling); the cooling-tank may include a refrigerant type cooling-circulation-pipelines to achieve the best control of the temperature of the intermediate-boost air (this is most preferable for use in the heavy duty engine applications); the temperature of the intermediate-boost air should be between 40 degree Celsius and 120 degree Celsius.
The servo-intake-process is the fourth process of the direct-power-cycle, which is the process to inject a flow of intermediate-boost air from the cooling-tank 130 into the first combustion chamber 132 and the second combustion chamber 134 at their designated crankshaft reference angle; as shown in
The process chart of high power output operation as shown in
The total duration of actuation of the servo-intake-valve is adjusted in the range of 5-60 degree of crankshaft rotation according to the instruction signals from the engine control unit, and the possible range of the servo-intake-process is from 240 degree to 350 degree of crankshaft reference angle.
The final-compression-process is the fifth process of the direct-power-cycle, which is the process to compress the intermediate-boost air in the combustion chambers 132 and 134, wherein the maximum compression pressure during this process will vary according to the engine power output; as in the process chart of low power output operation (
The ratio of the compression pressure at the end of the final-compression-process to the air-pressure in the cooling-tank is also referred as the actual-pressure-ratio of the final-compression-process for the ease of referencing. As shown in
The fuel can be supplied with two different methods; the first method is to install a low pressure fuel injector or a carburetor in the distributor-manifold, which can reduce the overall cost of the engine; the second method is to install a GDI injector (gasoline direction injection injector) in each combustion chamber. In addition, the natural gas or propane can also be easily adapted to the present invention with a propane converter to substitute the abovementioned carburetor in the distributor-manifold, whereas, the GDI injector is also possible to inject natural gas.
The fuel is supplied into the combustion chamber during the servo-intake-process or the final-compression-process with the abovementioned fuel-supplying means, and a spark plug will ignite the air-fuel mixture between 35 degree BTDC (before top dead centre) and 40 degree ATDC (after top dead centre) to initiate the combustion-process; the first embodiment will employ an ignition timing at 360 degree (0 degree) of crankshaft reference angle for the demonstration purpose in all the process charts of
The combustion-process is the sixth process of the direct-power-cycle, wherein an air-fuel mixture is combusting in the combustion chambers 132 and 134 after the completion of the final-compression-process; as shown in
The turbine-exhaust-process is the seventh process of the direct-power-cycle, wherein the combustion medium of the combustion chamber is charging into the turbine of the turbocharger in order to drive the compressor of the turbocharger for commencing the initial-compression-process; the exhaust-valve can also be actuated with a variable open-time scheme according to the engine power output, thereby preventing excessive combustion medium to remain in the combustion chamber prior to the next servo-intake-process; as shown in
The possible range of the turbine-exhaust-process is from 105 degree to 300 degree of crankshaft reference angle, and the duration of actuation of the exhaust valve should be at least 90 degree of crankshaft rotation.
The cooling-tank 130 can be employed with an air-cooling system or a refrigerant-cooling system; when used in a vehicle applications, the refrigeration circulation of the air-conditioning can be integrated with the cooling-circulation of the cooling-tank to reduce the overall vehicle size.
The direct-power-cycle engine may further include an air-assistance system, wherein the major modification is the actuation system of the servo-intake-valve and the exhaust-valve, such that, during a brake process, the servo-intake-valve and the exhaust-valve are disabled, the compressor-transmission of the intermediate-compressor will be set to high gear ratio, thereby increasing the revolution speed and the compression-capacity of the intermediate-compressor to recover the brake energy as a compressed air in the cooling tank.
A catalytic converter can be equipped in the exhaust gas passage between the combustion chamber and the turbine of the turbocharger, so that the thermo energy released in the catalytic converter can be recovered with the turbocharger.
Referring to
Referring to
The actuation-system of the servo-intake-valve of the direct-power-cycle engine can be a hydraulic actuation system, a mechanical variable-valve-timing system, or an electrical servo-valve system.
The intermediate-compressor of the direct-power-cycle engine can a screw type compressor, a scroll type compressor, a rotary-vane type compressor, or a piston type compressor; wherein the scroll type compressor, the rotary type compressor, and the screw type compressor are the most preferable for the highly efficient compression output and the low vibration characteristics.
The fuel supplying means of the direct-power-cycle engine can a carburetor, a direction injection nozzle, a GDI injector, a fuel-pump, or a propane converter; wherein the fuel can gasoline, methanol, natural gas, bio-fuel, propane, or a mixture of abovementioned fuel types that can be ignited with the spark ignition method.
The cooling-tank of the direct-power-cycle engine can operate with a refrigerant-circulation system, an air-circulation system, or a water-circulation system to perform the cooling-process of the direct-power-cycle.
The physical compression ratio of the combustion chamber of the direct-power-cycle engine ranges from 8:1 to 40:1, whereas the actual-pressure-ratio of the final-compression-process refers to the ratio of the compression pressure at the end of the final-compression-process to the air-pressure in the cooling-tank; the actual-pressure-ratio can range from 70% to 400%, for example with a direct-power-cycle engine operating with a constant pressure of 10 bar in the cooling-tank, the compression pressure at the end of the final-compression-process is then ranged from 7 bar to 28 bar according to the requested power output, wherein a higher actual-pressure-ratio of the final-compression-process will result in a higher power output of the direct-power-cycle engine.
The air passage between the compressor of the turbine (for performing the initial-compression-process) and the intermediate-compressor can further include an additional intercooler for cooling the initial-boost air from the compressor of the turbocharger in heavy duty engine applications or power generation applications.
The transmission means (compressor-transmission) of the intermediate-compressor is a continuously variable transmission, a mechanical gear transmission, or a hydraulic transmission.
It should be understood that there are more than one best mode in the present invention, as the direct-power-cycle engine can be constructed in many further developed forms by combining or rearranging the basic engine components mentioned in the present invention, and these alternations are still within the scope of the present invention.