High EGR rate system of single-cylinder supercharged gasoline engineTechnical Field
The invention relates to an engine test system, in particular to a high EGR rate system of a single-cylinder supercharged gasoline engine.
Background
Under the general aim of carbon neutralization, the development of efficient gasoline engines is regarded as a key technical direction for realizing energy conservation and emission reduction. The main technical means for realizing the gasoline engine with high thermal efficiency comprise high compression ratio, exhaust gas turbocharging, EGR, lean burn and the like. At present, gasoline engine knocking is the bottleneck of further improving the efficiency of the supercharged gasoline engine, and the EGR technology is one of effective measures for inhibiting the gasoline engine knocking at present. Because the load of the high-efficiency area of the gasoline engine is often higher, the pressure of an intake manifold is higher, and further increase of the EGR rate of the gasoline engine is limited. In the early stage of development of a gasoline engine with high thermal efficiency, principle prototype development is often required to be carried out on a single cylinder engine. Because the single-cylinder engine is always low in displacement and low in exhaust energy, an exhaust turbocharger for the single-cylinder engine is lacked in the industry at present; on a supercharged single-cylinder engine, high heat efficiency of the engine can be obtained by ensuring that enough air input in the cylinder maintains high load (supercharging pressure ratio is greater than 2) and a large amount of combustion exhaust gas (EGR rate is greater than 30%) is kept to inhibit knocking. However, there is a lack of implementation systems.
CN109252988A discloses 'a gasoline single cylinder engine EGR realization device and a use method thereof'; the exhaust pressure of the gasoline single cylinder engine is controlled by the exhaust back pressure regulating valve to simulate different EGR backflow modes of the multi-cylinder engine, the EGR backflow amount is controlled by the EGR valve to control the EGR rate, the EGR cooling water regulating valve is used for regulating the EGR backflow temperature, and therefore the single cylinder engine simulates the EGR implementation mode of the multi-cylinder engine.
CN212003378U discloses "dispose high EGR rate single cylinder engine exhaust gas recirculation system of filter equipment", including cylinder unit, back pressure valve, leading filter, EGR cooler, screw compressor, oil and gas separator, EGR rate governing valve, EGR second grade cooler and EGR check valve, wherein: compressed air is introduced into the cylinder unit, and one path of exhaust gas generated after the compressed air is combusted is exhausted from an exhaust main pipe through a backpressure valve; and the other path of the EGR gas passes through an EGR switch valve, sequentially passes through a pre-filter, an EGR cooler, a screw compressor, an oil-gas separator, an EGR rate regulating valve, an EGR secondary cooler and an EGR check valve and then enters the cylinder unit to form a circulation loop. The high-density/low-temperature combustion method can effectively realize a high-density/low-temperature combustion strategy by adopting a high EGR rate, and realize low emission and high efficiency of the marine diesel engine.
The technical solutions disclosed in the two patent documents mentioned above are, of course, a useful attempt in the technical field.
Disclosure of Invention
The invention aims to provide a high EGR rate system of a single-cylinder supercharged gasoline engine, which can meet the requirement of experimental development of the single-cylinder supercharged gasoline engine, and can keep enough air input in a cylinder to maintain high load (pressure ratio > 2) and a large amount of combustion exhaust gas (EGR rate > 30%) to inhibit knocking.
The invention relates to a high EGR rate system of a single-cylinder supercharged gasoline engine, which comprises a single-cylinder gasoline engine, an air inlet pipeline, an exhaust pipeline and an exhaust gas circulating pipeline connected between the air inlet pipeline and the exhaust pipeline, and is characterized in that: the air inlet loop comprises an air filter, a mixing valve, an air compressor, an intercooler and a throttle valve, wherein the first end of the mixing valve is communicated with the outlet of the air filter; the exhaust pipeline comprises a waste gas pressure stabilizing cavity connected and communicated with an exhaust port of the single-cylinder gasoline engine and an exhaust back pressure valve arranged on an exhaust pipeline of the waste gas pressure stabilizing cavity and connected and communicated with the exhaust port.
Furthermore, one end of the waste gas circulating pipeline is communicated with a pipeline between the waste gas pressure stabilizing cavity and the exhaust back pressure valve, an exhaust filter screen, an EGR cooler and an EGR valve are sequentially arranged in the waste gas circulating pipeline from right to left, and the EGR valve is communicated with a third end of the mixing valve.
Furthermore, the air inlet loop also comprises a bypass valve communicated with the fourth end of the mixing valve and the air outlet end of the air compressor.
Further, the air compressor is a two-stage centrifugal air compressor.
The invention has the beneficial effects that:
fresh air required by the single-cylinder gasoline engine enters from the air filter; waste gas and fresh air are mixed after the mixing valve, the mixing valve adopts a Venturi tube structure, the flow of the waste gas entering the air inlet pipeline can be assisted to be improved, and the achievement of high EGR rate is ensured;
after the fresh air and the waste gas are mixed, the air pressure and the density of the air entering the single-cylinder gasoline engine are increased through the air compressor, the temperature of the air is reduced through the intercooler, and the load of the single-cylinder gasoline engine is controlled by the throttle valve; when the single-cylinder gasoline engine does not need to operate under high load, the air compressor stops working, and the bypass valve is opened, so that the single-cylinder gasoline engine can stably operate under the working condition of low load.
The pressure of the exhaust gas discharged by the single-cylinder gasoline engine is stabilized in the exhaust gas pressure stabilizing cavity, so that the pressure stability of the discharged exhaust gas is ensured; the exhaust backpressure is improved through the exhaust backpressure valve, so that enough waste gas can enter the air inlet end through the waste gas circulating pipeline;
because the exhaust filter screen is arranged on the exhaust gas circulating pipeline to filter impurities in the exhaust gas, and the EGR cooler is arranged to reduce the temperature of the exhaust gas; an EGR valve is provided to control the flow of exhaust gas into the inlet line, thereby ensuring the desired EGR rate.
Drawings
Fig. 1 is a schematic structural view of the present invention.
In the figure (technical signature):
10-single cylinder gasoline engine, 11-air filter, 12-mixing valve, 13-air compressor, 14-intercooler, 15-throttle valve, 16-bypass valve;
21-exhaust pressure stabilizing cavity, 22-exhaust back pressure valve;
31-exhaust filter screen, 32-EGR intercooler, 33-EGR valve.
Detailed Description
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.
Referring to fig. 1, the high EGR rate system of the single cylinder supercharged gasoline engine comprises a single cylinder gasoline engine 10, an air inlet pipeline, an exhaust pipeline and an exhaust gas circulation pipeline connected between the air inlet pipeline and the exhaust pipeline, and is characterized in that: the air inlet loop comprises an air filter 11, a mixing valve 12, an air compressor 13, an intercooler 14 and a throttle valve 15, wherein the first end of the mixing valve is communicated with the outlet of the air filter, the air compressor 13 is communicated with the second end of the mixing valve, the air inlet end of the air compressor is communicated with the air outlet end of the air compressor, the throttle valve is communicated with the intercooler, and the throttle valve is arranged at the air inlet of the single-cylinder gasoline engine 10; fresh air and waste gas are mixed in a mixing valve, and a Venturi tube structure is adopted to assist in increasing the flow of the waste gas entering an air inlet pipeline so as to ensure the achievement of high EGR rate; after the mixed gas is compressed by the air compressor to improve the gas pressure and density, the gas temperature is reduced by the intercooler, and the load of the single-cylinder gasoline engine is controlled by the throttle valve, so that the load of the single-cylinder gasoline engine is improved.
The exhaust pipeline comprises an exhaust gaspressure stabilizing cavity 21 communicated with an exhaust port of the singlecylinder gasoline engine 10 and an exhaust back pressure valve 22 arranged on an exhaust pipeline of the exhaust gas pressure stabilizing cavity and communicated with the exhaust port; the waste gas pressure stabilizing cavity enables waste gas to be stabilized in pressure so as to ensure the pressure of the discharged waste gas to be stable; the exhaust backpressure valve enables the exhaust gas to lift exhaust backpressure so as to ensure that the exhaust gas can enter the air inlet pipeline through the exhaust gas circulation pipeline;
one end of the exhaust gas circulating pipeline is communicated with a pipeline between the exhaust gaspressure stabilizing cavity 21 and the exhaust back pressure valve 22, anexhaust filter screen 31, anEGR cooler 32 and an EGR valve 33 are sequentially arranged in the exhaust gas circulating pipeline from right to left, and the EGR valve is communicated with the third end of the mixingvalve 12. After impurities in the exhaust gas are filtered by an exhaust filter screen in the exhaust gas circulation pipeline, the temperature of the exhaust gas is reduced by an EGR cooler, and the flow of the exhaust gas entering an air inlet pipeline is controlled by an EGR valve so as to ensure the required EGR rate
EGR rate can be measured by CO from the intake manifold and exhaust plenum of a single cylinder gasoline engine2The concentration is calculated, and the calculation formula is as follows:
EGR rate-CO at the intake manifold of the singlecylinder gasoline engine 102CO at concentration/exhaust plenum 212And (4) concentration.
The inlet circuit also includes abypass valve 16 in communication with the fourth end of the mixingvalve 12 and the outlet end of theair compressor 13. When the single-cylinder gasoline engine does not need to operate under high load, the air compressor stops working, and the bypass valve is opened to ensure that the single-cylinder gasoline engine can stably operate under the working condition of low load.
Theair compressor 13 is a two-stage centrifugal air compressor.