A natural gas engine exhaust heat and LNG cold energy combined utilization system

Abstract

The application aims to provide a natural gas engine exhaust heat and LNG cold energy combined utilization system, wherein the fuel of the natural gas engine is generally stored in an LNG tank in liquid state, and needs to be heated before entering the natural gas engine for combustion, and in this process, the cold energy is wasted. In addition, the turbocharger outlet temperature of the natural gas engine can reach 700 DEG C, and the potential heat energy in the exhaust gas of the natural gas engine cannot be fully utilized, and in this process, there is still room for heat energy utilization. In order to solve the problem of energy waste, the application simultaneously utilizes the temperature difference power generation device and the attached system of the two kinds of energy to realize the comprehensive utilization of the two kinds of energy; the electrically controlled three-way valve installed on the exhaust pipe and the LNG inlet pipe is used to match the operating conditions of the natural gas engine; and the temperature uniformity of the hot end and the cold end of the temperature difference power generation device is realized through the backheating type pipeline arrangement and the special double helix structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a natural gas engine, in particular to a waste heat and cold energy utilization system of the natural gas engine. BACKGROUND

[0002] The fuel of the natural gas engine is generally stored in the LNG tank in liquid state, and needs to be heated before entering the natural gas engine for combustion, and in this process, the cold energy is wasted.

[0003] The exhaust gas of the natural gas engine is generally used in the exhaust gas turbocharger to pressurize the fresh air, but the outlet temperature can still reach 700℃, which shows that the turbocharger cannot fully utilize the potential heat energy in the exhaust gas of the natural gas engine, and there is still room for heat energy utilization in this process.

[0004] The principle of the thermoelectric power generation technology is that the diffusion speed of the electron is proportional to the temperature, and when the temperature in the metal is not uniform, the free electrons at the high temperature end have more kinetic energy than the free electrons at the low temperature end. When the temperature is not uniform, the free electrons diffuse from the high temperature end to the low temperature end and accumulate at the low temperature end, thereby forming an electric field in the conductor metal, and an electric potential difference is generated at both ends of the metal rod. At this time, if an external load such as a storage battery is connected, an electric current loop is formed. As long as the cold source and the hot source that form the potential difference continuously maintain the temperature difference, the thermoelectric generator can continuously work. When other conditions are given, within a certain range, the greater the temperature difference between the cold end and the hot end, the higher the power generation efficiency, and for the same size temperature difference, within a certain range, the lower the temperature zone, the higher the power generation efficiency. The thermoelectric power generation device has the advantages of simple structure, long service life, no noise, no moving parts, etc., and has received more and more attention and has been applied in many fields.

[0005] For the traditional cold energy or heat energy utilization thermoelectric power generation device, the working medium of the heat source and the cold source flows in from one direction of the thermoelectric power generation sheet and flows out from the other direction, which will cause uneven heat conduction of the thermoelectric power generation sheet, and then affect the balance of the electric potential difference, and reduce the output voltage stability and efficiency of the thermoelectric power generation device. SUMMARY

[0006] The purpose of the present application is to provide a natural gas engine exhaust gas heat energy and LNG cold energy combined utilization system which can improve the overall energy efficiency of the natural gas engine and further improve the economy.

[0007] The purpose of the present application is achieved as follows:

[0008] The application discloses a natural gas engine exhaust heat energy and LNG cold energy combined utilization system, which is characterized by comprising a natural gas engine, a thermoelectric power generation device, an air inlet mixer, an exhaust mixer, an LNG mixer, an LNG storage tank, an air inlet pipe and an exhaust pipe of the natural gas engine being connected with the air inlet mixer and the exhaust mixer respectively, the exhaust mixer being connected with a turbine of a turbocharger through a first electrically-controlled three-way valve, the air inlet mixer being connected with a compressor of the turbocharger, the air inlet mixer being connected with the LNG mixer through a second electrically-controlled three-way valve, the LNG mixer being connected with the LNG storage tank, the thermoelectric power generation device comprising a cold end and a hot end, thermoelectric power generation sheets being arranged between the cold end and the hot end, the cold end being provided with a first cold end inlet, a second cold end inlet, a first cold end outlet and a second cold end outlet respectively, the hot end being provided with a first hot end inlet, a second hot end inlet, a first hot end outlet and a second hot end outlet respectively, the first cold end inlet and the second cold end inlet being connected with the first electrically-controlled three-way valve through a first three-way valve, the first hot end outlet and the second hot end outlet being connected with the exhaust mixer through a second three-way valve, the first hot end inlet and the second hot end inlet being connected with the second electrically-controlled three-way valve through a third three-way valve, and the first cold end outlet and the second cold end outlet being connected with the LNG mixer through a fourth three-way valve.

[0009] The application can further comprise:

[0010] 1. The thermoelectric power generation device is connected with a storage battery.

[0011] 2. The thermoelectric power generation sheets of the thermoelectric power generation device are circular, the hot end and the cold end are pipeline structures for circulating working medium, and the structures are central-symmetrical double helix structures; for a single hot end or cold end, two working medium inlets are located at different starting points and ending points of the double helix structures, one is located at the center and enters the thermoelectric power generation sheet, and the other is located at the maximum diameter of the helix and tangentially enters the helix; the working medium outlets are opposite to the working medium inlets, one is located at the center and flows out away from the thermoelectric power generation sheet, and the other is located at the maximum diameter of the helix and tangentially flows out.

[0012] 3. Heat-conducting materials are filled in the gaps between the hot end and the thermoelectric power generation sheets and the gaps between the cold end and the thermoelectric power generation sheets respectively, and heat-insulating materials are coated on the surfaces of the pipelines of the hot end and the cold end which are not adjacent to the thermoelectric power generation sheets.

[0013] The application has the following advantages:

[0014] 1. The natural gas engine LNG cold energy and exhaust heat energy are combined and utilized, the energy utilization efficiency and economy are improved, and the advantage that the larger the temperature difference of the thermoelectric power generation device is, the higher the efficiency is can be fully utilized.

[0015] 2. The central-symmetrical double helix structure can unify the temperatures of the cold end and the hot end of the thermoelectric power generation sheet, and the efficiency and stability of the thermoelectric power generation sheet are improved.

[0016] 3. The working medium of the thermoelectric generator device adopts the "regenerative" mode of the intake method, which can more fully utilize the waste heat energy and LNG cold energy, and the electric control three-way valve can control the flow, which can ensure that the energy utilization system will not affect the working needs of the natural gas engine. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a structural schematic diagram of the present application;

[0018] Figure 2 The figure is an axonometric view of the center-symmetrical double helix structure of the thermoelectric generator device. DETAILED DESCRIPTION

[0019] The present application will be described in more detail below with examples combined with the drawings:

[0020] Combined Figures 1-2 , the present application is a natural gas engine waste heat energy and LNG cold energy combined utilization system, which comprises a natural gas engine 1, an LNG storage tank 7, a buffer tank 10, an LNG mixer 9, a waste gas mixer 5, a thermoelectric generator device 4, a turbocharger 8, and an electric control system 2. The exhaust gas of the natural gas engine 1 is introduced into the waste gas mixer 5 through a pipeline, mixed with the waste gas from the hot end outlet 17 of the thermoelectric generator device, and then the mixed waste gas is introduced into the hot end inlet 18 of the thermoelectric generator device and the turbocharger 8 under the control of the electric control three-way valve 6. The LNG in the LNG storage tank 7 is introduced into the LNG mixer 9 through a pipeline, mixed with the LNG from the cold end outlet 23 of the thermoelectric generator device, and then the mixed LNG is introduced into the cold end inlet 22 of the thermoelectric generator device and the vaporizer 13 under the control of the electric control three-way valve 11. The vaporizer 13 and the electric control three-way valve 11 are connected by a pipeline to a buffer tank 10.

[0021] The mixed waste gas introduced into the hot end 19 of the thermoelectric generator device is evenly divided into two paths through a three-way valve 16, introduced into the thermoelectric generator device 4 from the two inlets 18 of the hot end, and converged into the waste gas mixer 5 from the two outlets 17 of the hot end through a three-way valve 16; the LNG introduced into the cold end 21 of the thermoelectric generator device is evenly divided into two paths through a three-way valve 16, introduced into the thermoelectric generator device from the two inlets 22 of the cold end, and converged into the LNG mixer 9 from the two outlets 23 of the cold end through a three-way valve 16.

[0022] The external load of the thermoelectric generator device 4 is a storage battery 3, which stores electrical energy when the thermoelectric generator device 4 is working, or is used to power other equipment, or is used to power the electric control system.

[0023] A natural gas concentration sensor 14 and a pressure sensor 15 are arranged at the outlet of the natural gas engine intake mixer 12 to monitor the natural gas concentration and pressure of the natural gas engine intake mixer 12, and to control the proportion of the exhaust gas or LNG flowing into the hot end 19 or the cold end 21 of the thermoelectric generator according to the needs of the natural gas engine 1, respectively.

[0024] The thermoelectric generator sheet 20 of the thermoelectric generator is circular, and the hot end 19 and the cold end 21 are respectively located on the front and back surfaces of the thermoelectric generator sheet 20 and are a pipe structure for flowing the working medium, which is a double helix structure with central symmetry, as shown in Figure 2 For a single hot end or cold end, the two working medium inlets are respectively located at different starting points and ending points of the double helix structure, one is located at the center of the circle and faces the thermoelectric generator sheet, and the other is located at the maximum diameter of the helix and is tangent to the helix line. The working medium outlets are just opposite to the inlets, one is located at the center of the circle and flows out away from the thermoelectric generator sheet, and the other is located at the maximum diameter of the helix and flows out tangent to the helix line.

[0025] The gap between the hot end 19 and the thermoelectric generator sheet 20 and the gap between the cold end 21 and the thermoelectric generator sheet 20 are respectively filled with a heat-conducting material, and the surfaces of the pipes of the hot end 19 and the cold end 21 that are not adjacent to the thermoelectric generator sheet 20 are respectively coated with a heat-insulating material.

Claims

1. A system for the combined utilization of exhaust heat energy from a natural gas engine and cold energy from LNG, characterized in that: The system includes a natural gas engine, a thermoelectric generator, an intake mixer, an exhaust mixer, an LNG mixer, and an LNG storage tank. The intake and exhaust pipes of the natural gas engine are connected to the intake and exhaust mixers, respectively. The exhaust mixer is connected to the turbine of a turbocharger via a first electrically controlled three-way valve. The intake mixer is connected to the compressor of the turbocharger. The intake mixer is connected to the LNG mixer via a second electrically controlled three-way valve. The LNG mixer is connected to the LNG storage tank. The thermoelectric generator includes a cold end and a hot end, with a thermoelectric generator plate installed between them. The thermoelectric generator plate is circular. The hot and cold ends are pipe structures for flowing working fluid, and their structure is a centrally symmetrical double helix structure. For a single hot or cold end, the two working fluid inlets are located at different starting and ending points of the double helix structure, one at the center and... One inlet is directly opposite the thermoelectric generator, while the other is located at the point of maximum spiral diameter and tangential to the spiral line. The working fluid outlets are opposite to the working fluid inlets; one is located at the center of the circle, flowing out away from the thermoelectric generator, and the other is located at the point of maximum spiral diameter and tangential to the spiral line. The cold end is equipped with a first cold end inlet, a second cold end inlet, a first cold end outlet, and a second cold end outlet. The hot end is equipped with a first hot end inlet, a second hot end inlet, a first hot end outlet, and a second hot end outlet. The first cold end inlet and the second cold end inlet are connected to a first electrically controlled three-way valve via a first three-way valve. The first hot end outlet and the second hot end outlet are connected to the exhaust gas mixer via a second three-way valve. The first hot end inlet and the second hot end inlet are connected to a second electrically controlled three-way valve via a third three-way valve. The first cold end outlet and the second cold end outlet are connected to the LNG mixer via a fourth three-way valve.

2. The system for combined utilization of natural gas engine exhaust heat energy and LNG cold energy according to claim 1, characterized in that: The thermoelectric generator is connected to a storage battery.

3. A system for combined utilization of exhaust gas heat energy and LNG cold energy from a natural gas engine according to claim 1, characterized in that: in Thermally conductive materials are filled in the gaps between the hot end and the thermoelectric generator and between the cold end and the thermoelectric generator. Thermal insulation materials are applied to the surfaces of the pipes at the hot and cold ends that are not adjacent to the thermoelectric generator.

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