Patent Application
20090178642
1. Field of the Invention
The present invention relates to a heat energy recycling device, particularly to a heat energy recycling device for an engine and a two-stroke engine using the same.
2. Description of the Related Art
The internal combustion engine has been a matured technology including many branches, wherein two-stroke engines and four-stroke engines are the most widely used. Four-stroke engines are more stable, oil-saving and environment-friendly than two-stroke engines. However, due to the complicated structure, the volume efficiency of a four-stroke engine is only half that of a two-stroke engine. The cost of parts and mechanical design and the oil consumption of a four-stroke engine are thus increased. In practical application, the energy efficiency of the internal combustion engine is only 20-30%, and more than 70% of energy is dissipated into the atmosphere in form of heat. Because automobiles accelerate and brake frequently, dynamic energy is converted into heat, which further lowers the efficiency of energy. Thus, more fuel oil is burned, and more carbon dioxide and hydrocarbon is released, which aggravates the greenhouse effect of the earth and further increases the demand for fuel oil. Under the anxiety of petroleum supply, the price of fuel oil has risen 300% in recent few years.
Many current automobile researches are directed to develop hybrid vehicles, which are propelled by an internal combustion engine and an electric motor powered by batteries or fuel cells, to overcome the abovementioned problems. However, such a solution has a high cost and many difficulties hindering the popularization thereof.
Two-stroke engines have the advantages of lightweight and small size. However, traditional two-stroke engines also have the disadvantage of lower fuel efficiency because fuel gas mixed with exhausted gas and emit into the exhaust pipe. Besides, one combustion cycle per each two strokes results in high thermal load and greater cooling loss consequently. Furthermore, high cylinder temperature and heat-dissipation difficulty results in high temperature, and the compression ratio is thus hard to increase because knocking is apt to occur at a high compression ratio. In a two-stroke engine, exhausted gas was expelled by intake air out of the cylinder. When the load is low, the amount of intake air is small. Thus, a great amount of high-temperature residual gas is not expelled but remains inside the cylinder to mix with new fuel air, which is apt to cause a high-temperature spontaneous combustion under a high compression ratio. The abovementioned low-load knocking is a characteristic of two-stroke engines and usually hinders the promotion of the compression ratio.
Therefore, the present invention proposes a heat energy recycling device for an engine and a two-stroke engine using the same, which can decrease fuel consumption and increase the efficiency of an internal combustion engine, to overcome the conventional problems.
The primary objective of the present invention is to provide a heat energy recycling device for an engine and a two-stroke engine using the same, wherein the high-pressure and high-temperature water heated by the recycled heat energy from the stroke of the explosive combustion of fuel, whereby the fuel efficiency of an engine is promoted.
Another objective of the present invention is to provide a heat energy recycling device for an engine and a two-stroke engine using the same, which can realize a low-fuel consumption and high-compression ratio two-stroke engine.
Further objective of the present invention is to provide a heat energy recycling device for an engine and a two-stroke engine using the same, which can decrease emission and reduce environmental pollution.
To achieve the abovementioned objectives, the present invention proposes a heat energy recycling device for an engine, which comprises: a condenser; an exhaust device having one end connecting with an exhaust outlet of the engine and the other end connecting with the condenser; a water tank store water and recycling the condensed water from the condenser and providing injection water; a high-pressure water pump connecting with the water tank; a high-pressure injection water conduit having one end connecting with the water pump that pressurizes the water inside the high-pressure injection water conduit; and a high-pressure water injector connecting with the other end of the high-pressure injection water conduit and injecting water into a cylinder of the engine to implement a water dynamic stroke.
The present invention also proposes a two-stroke engine having a heat energy recycling device, which comprises: a two-stroke engine and a heat energy recycling device. The two-stroke engine further comprises at least one cylinder, and the cylinder includes at least one exhaust outlet and at least one fuel injector. The heat energy recycling device for the engine comprises: a condenser; an exhaust device having one end connecting with the exhaust outlet of the engine and the other end connecting with the condenser; a water tank store water and recycling the condensed water from the condenser and providing injection water; a high-pressure water pump connecting with the water tank; a high-pressure injection water conduit having one end connecting with the water pump that pressurizes the water inside the high-pressure injection water conduit; and a high-pressure water injector arranged inside the cylinder, connecting with the other end of the high-pressure injection water conduit and injecting water to the cylinder of the engine to implement a water dynamic stroke.
Below, the preferred embodiments will be described in detail in cooperation with the attached drawings to make easily understood the characteristics and efficacies of the present invention.
Refer to
The exhausted gas arriving at the exhaust device 14 and the exhaust outlet 18 of the engine 16 has a temperature as high as 500-800° C. Thus, the high-pressure injection water conduit 24 is wound around the perimeter of the exhaust device 14 or is wound inside the exhaust device 14 to heat the water inside the high-pressure injection water conduit 24 to a temperature over 450° C.
The heat energy recycling device 10 of the present invention further comprises a temperature sensor 30 to detect the temperature of the cylinder 17. The detected temperature is provided for the control computer 28 as a reference.
The exhausted gas generated by fuel combustion and the exhaust vapor of a water dynamic stroke contains water and carbon dioxide. The water vapor will condense and become liquid water at a temperature below 100° C. The condenser 12 is to recycle water and provide the recycled water for the water dynamic stroke. Thereby, the frequency of refilling water into the water tank 20 or the amount of the water refilled into the water tank 20 can be reduced.
The engine 16 shown in
Refer to from
Next, the piston 32 moves from the bottom dead center toward the top dead center. At the same time, the control computer 28 detects whether the engine 16 has enough heat energy to perform a water dynamic stroke. If the engine 16 has enough heat energy, the water dynamic stroke shown in from
The present invention uses the heat energy of the engine 16 to heat the water injected by the high-pressure water injector 26. Therefore, a thermally insulating material (not shown in the drawings) may be used to envelop the engine 16 and reduce heat emission from the engine 16.
Below, embodiments are used to verify the efficacies of the heat energy recycling device of the present invention.
Suppose the atmospheric temperature is 25° C. (298°K in the absolute temperature), the atmospheric pressure 1 Bar, and the weight of a liter of air roughly 1 gram.
The following constants will be used in the description of the embodiments: the heat capacity ratio r is 1.4, the specific heat capacity of air 0.241 Cal/(g×°K), the specific heat capacity of water vapor about 0.49 Cal/(g×°K), 1 liter of air about 0.0448 mole, and 1 gram of water about 0.0555 mole.
The following equations will be used in the description of the embodiments:
The ideal gas equation: PV=nRT, wherein P is the pressure, V the volume, and n the number of moles, R the universal gas constant, and T the absolute temperature.
The compression-temperature equation: Tc=Ta×Rc(r−1), wherein Tc is the temperature after compression, Ta the initial temperature, and Rc the compression ratio.
The compression-pressure equation: Pc=Pa×Rcr, wherein Pc is the pressure after compression, Pa the initial pressure, and Rc the compression ratio.
Suppose the compression ratio of an engine is 10.
When the volume is compressed from 1 liter to 0.1 liter, the temperature after compression is Tc=(273+25)×10(1.4−1)=748.54°K (475.54° C.), and Delta T=475.54−25=450.54, and the pressure after compression is Pc=1×101.4=25.11 Bar.
After the abovementioned compression, 0.9 gram of hot water having a temperature of 748.54°K (475.54° C.) is injected into a cylinder. As the saturation temperature of water at pressure of 25.11 Bar is much lower than 748°K, the water vaporizes because by its own heat energy, and absorbs the heat energy of the high-temperature air inside the cylinder.
Because of the addition of water, the heat capacity ratio r is about 1.35. The resultant pressure is equivalent to the pressure resulting from that 0.9 times of air is added into 0.1 liter of air. In other words, the compression ratio is 1.9. Thus, the resultant pressure is Pc=25.11×1.91.35=60 Bar.
The vaporization of water results in the 60 Bar pressure. Meanwhile, the temperature also gradually decreases until the pressure and the saturation temperature of water reach a balance. In such a case, most of water will vaporize.
The work done by the engine is W=P×delta V. When the gas inside the cylinder expands from 0.1 to 1 liter, the total work done by the engine is
wherein Pp=the pressure after the addition of heat, and
Po=the pressure before the addition of heat.
It should be noted that 60 Bar is much greater than 25.11 Bar generated by compressing air.
With a rough calculation, the total work done by the engine in a cycle is about a dynamic energy of 860 joules.
Without the factor of cylinder temperature, the temperature of the water vapor will decrease to under 373°K (100° C.) in the moment that the piston downward movement and the water vapor expansion. In practice, when the water vapor inside the cylinder expands, the temperature of the water vapor will be lower than the saturation temperature. Thus, the water vapor begins to condense, and the pressure also begins to decrease, which hinders doing a work. In the fuel combustion stroke, about 30% of heat energy is absorbed by the cylinder, piston, and the devices contacting the high-temperature gas. If the heat energy is not dissipated via the radiator, the temperature of the cylinder, etc., will rise to over 1000° C. in a very short time. In considering the need of engine operation, the temperature of the cylinder, etc., should be controlled to around 100- 200° C. A general solution is to arrange water channels over the cylinder, and the radiator can thus dissipate the heat to the atmosphere. However, such a solution cannot effectively decrease the temperature of the cylinder. The heat on the internal surface of the cylinder is transferred to the atmosphere via the path of the cylinder wall, water and then the radiator. However, the heat convection is not uniform. In other words, some regions have too high a temperature, and some other regions have too low a temperature. Thus, a part of compressed fuel gas contacting a high-temperature region has a spontaneous combustion. The explosion of the ignited fuel gas will impact the spontaneous-combustion gas, which generates a knocking and hinders promoting the compression ratio. The piston is particularly hard to cool down and has a high temperature, which further raises the difficulty of promoting the compression ratio.
The present invention does not use the water channels and radiator to dissipate heat. In the present invention, heat is conducted from the cylinder and piston to the vapor having a temperature lower than that of the cylinder and piston to cool down the temperature of the cylinder and piston. In the expansion stage, vapor absorbs heat from the cylinder and piston to maintain the gaseous state and maintain the stability of the internal temperature of the cylinder. Therefore, the present invention can promote the compression ratio and increase the fuel-efficiency.
In the present invention, the computer determines when to stop fuel supply and start a water dynamic stroke. When to start a water dynamic stroke relies on the temperature of the engine, the load, the rotation speed, the fuel throttling state, and the atmospheric temperature. Thus, the application of the present invention is not limited by the mechanical structure but has a great flexibility.
A vehicle under a cruise control or at an idle state requires less dynamic energy. Increasing the proportion of the water dynamic stroke at this time can effectively recycle heat energy and greatly reduce fuel consumption. Besides, as after water dynamic stroke, hot residual gas no longer remain, increasing the proportion of the water dynamic stroke at a state of low load is helpful to eliminating the low-load knocking, which is apt to occur in a high compression two-stroke engine.
Further, the present invention can obviously decrease the internal temperature of an engine, particularly the temperature of the piston, and thus can reduce the knocking and favor realizing a high compression ratio two-stroke engine.
The preferred embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Any equivalent modification or variation according to the shapes, structures, characteristics or spirit of the present invention is to be also included within the scope of the present invention.
