CN104074634A - Two-way gas supply system and method for natural gas engine - Google Patents

Abstract

The invention discloses a dual-channel gas supply system and method for a natural gas engine, comprising an electric control system ECU, a natural gas engine, and a gas supply system for supplying mixed gas to the natural gas engine, and the gas supply system includes: a main mixed gas supply system and the auxiliary mixed gas supply system; the flows of the main mixed gas supply system and the auxiliary mixed gas supply system are respectively controlled by the electric control system ECU; the beneficial effect of the present invention is to adopt a two-way gas supply system that improves the responsiveness of the natural gas engine, and the natural gas engine When the load suddenly increases, the auxiliary mixed gas supply system supplies an additional part of the mixed gas to the engine, thereby overcoming the problems of slow response of the traditional intake manifold injection natural gas engine, the speed drops and the torque drops when the load suddenly increases, and improves the performance of the natural gas engine. The power and reliability improve the operability of natural gas engine powered machinery.

Description

A dual-channel gas supply system and method for a natural gas engine

technical field

The invention relates to the technical field of natural gas engines, in particular to an engine dual-channel gas supply system and method for improving the responsiveness of natural gas engines.

Background technique

Natural gas is a clean fuel. In addition to being collected from natural gas fields and associated gas fields of oil fields, it can also be produced from kerogen shale or biomass energy. It has the advantages of wide sources and low price, and is an ideal alternative energy source for internal combustion engines. At present, governments around the world, including China, attach great importance to the development of natural gas engines, and machinery powered by natural gas engines is playing an increasingly important role in the development of the national economy.

The spark-ignition natural gas engine with single-point mixing in the intake manifold is currently the largest natural gas engine in stock. The air source of the vehicle engine and marine engine is a pressurized air source, so the single-point mixing method after the supercharger is generally used in the supercharged vehicle engine. The advantage of the single-point hybrid natural gas engine is that the natural gas/air mixture is relatively uniform, the propagation speed of the flame in all directions is relatively uniform during the combustion process, and there will be no local over-rich areas and areas with excessive heat loads inside the combustion chamber.

The disadvantage of this natural gas engine is that the adjustment of the injection quantity of natural gas is determined by the flow rate of the supercharged air, and the supercharging capacity of the supercharger is limited by the maximum available energy in the exhaust gas. When the engine load suddenly increases or the throttle opening suddenly increases rapidly, due to the influence of supercharger responsiveness and the responsiveness of intake air in the intake and exhaust system, the engine responds poorly, the speed decreases, and the torque rises slowly. And other issues. As a result, problems such as low operational sensitivity and unstable work occur in powered vehicles or ships configured with such natural gas engines.

Contents of the invention

The purpose of the present invention is to solve the above problems, and propose a dual-channel gas supply system and method for a natural gas engine. The system and method overcome the slow response of the traditional intake manifold injection natural gas engine, and the decrease in speed and torque when the load suddenly increases. The problem of improving the operability of the power machinery equipped with natural gas engine.

In order to achieve the above object, the present invention adopts the following technical solutions:

A two-way gas supply system for a natural gas engine, comprising an electronic control system ECU, a natural gas engine, and a gas supply system for supplying mixed gas to the natural gas engine, characterized in that the gas supply system includes: a main mixed gas supply system and an auxiliary Mixed gas supply system; the flows of the main mixed gas supply system and the auxiliary mixed gas supply system are respectively controlled by the electronic control system ECU;

The main mixed gas supply system includes: a natural gas storage device, a pressure reducer, a voltage stabilizer, a mechanical heat exchanger, an electronically controlled injector and a mixer connected in sequence through a natural gas pipeline; a supercharger and an intercooler are connected through an air pipe After the road is connected, it is connected to the mixer;

The natural gas enters the mixer through the pressure reducer, the voltage stabilizer, the mechanical heat exchanger, and the electronically controlled injector in sequence; the external air enters the mixer through the engine supercharger and the intercooler in sequence to mix with the natural gas;

The auxiliary mixed gas supply system includes: the compressed air storage device and the auxiliary flow control valve are connected to the mixer through the auxiliary air pipeline; the compressed air enters the mixer through the auxiliary flow control valve to assist in increasing the air flow;

Also includes:

The mixer is connected with the natural gas engine through the electronic throttle, and the electronically controlled injector and the electronic throttle are respectively connected with the electronic control system ECU.

A natural gas flow meter is arranged on the pipeline connecting the mechanical heat exchanger and the electronic control injector, and the natural gas flow meter is connected to the electronic control system ECU.

An air flow meter is arranged on the air pipeline connecting the intercooler and the mixer, and the air flow meter is connected to the electronic control system ECU.

An auxiliary air flowmeter is arranged on the auxiliary air pipeline connecting the auxiliary flow control valve and the mixer, and the auxiliary flow control valve and the auxiliary air flowmeter are respectively connected with the electric control system ECU.

An air cut-off valve is arranged at the outlet of the compressed air storage device.

The exhaust gas of the natural gas engine is discharged through the catalytic post-processor, and an exhaust gas oxygen sensor is arranged at the outlet of the catalytic post-processor, and the exhaust gas oxygen sensor is connected with the electronic control system ECU.

A method for a two-way gas supply system for a natural gas engine, comprising:

When the engine is running stably, the main mixed gas supply system provides the mixed gas for the engine; the electronic control system ECU calculates the injection quantity according to the air flow, engine operating parameters and the pre-calibrated MAP map, and controls the natural gas quantity injected by the electronically controlled injector;

When the engine load changes and the speed fluctuation value exceeds the set threshold compared with the original stable running engine speed, the main mixed gas supply system and the auxiliary mixed gas supply system jointly provide mixed gas for the engine; the electronic control system ECU collects engine Changes in speed, control the increase of the opening of the electronic throttle, and open the auxiliary air flow control valve, by collecting the flow of auxiliary air and the change of engine speed, real-time control of the mixed gas flow of the auxiliary mixed gas supply system;

After the engine speed stabilizes, the auxiliary mixer supply system stops working, and the main mixed gas supply system continues to provide mixed gas to the engine.

The electronic control system ECU simultaneously controls the electronic throttle of the main mixture supply system and the auxiliary air flow control valve of the auxiliary mixer supply system, and controls the total natural gas injection volume and air flow according to the operating conditions of the engine.

The beneficial effects of the present invention are:

The invention adopts a two-way gas supply system that improves the response of natural gas engines. When the load of the natural gas engine suddenly increases, the auxiliary mixed gas supply system supplies a part of the mixed gas to the engine, thereby overcoming the slow response of the traditional intake manifold injection natural gas engine. The problems of speed reduction and torque drop during sudden acceleration have improved the power and reliability of the natural gas engine, and improved the operability of the power machinery equipped with the natural gas engine.

Description of drawings

Fig. 1 is the working schematic diagram of the gas supply system of natural gas engine in the prior art;

Fig. 2 is the working schematic diagram of the two-way fuel gas supply system of the natural gas engine of the present invention;

Fig. 3 is a flow chart of the method of the dual-channel gas supply system for a natural gas engine of the present invention.

Among them, 201. Natural gas cylinder, 202. Electronic control system ECU, 203. Exhaust oxygen sensor, 204. Catalytic post-processor, 205. Natural gas engine, 206. Supercharger, 207. Intercooler, 208. Compressed air tank , 209 Air Shutoff Valve, 210. Auxiliary Air Line, 211. Air Line, 212. Auxiliary Air Flow Control Valve, 213. Auxiliary Air Flow Meter, 214. Air Flow Meter, 215. Electronic Throttle, 216. Mixer , 217. Electronically controlled injector, 218. Natural gas flowmeter, 219. Mechanical heat exchanger, 220. Regulator, 221. Natural gas pipeline, 222. Natural gas pressure reducer, 223. Natural gas shut-off valve.

Detailed ways:

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

FIG. 1 is a schematic diagram of a gas supply system for a natural gas engine in the prior art. The natural gas engine gas supply system may include a natural gas cylinder 201, an electronic control system ECU202, an exhaust gas oxygen sensor 203, a catalytic post-processor 204, a natural gas engine 205, a supercharger 206, an intercooler 207, an air pipeline 211, and an air flow rate Meter 214, electronic throttle valve 215, mixer 216, electronically controlled injector 217, natural gas flow meter 218, mechanical heat exchanger 219, voltage regulator 220, natural gas pipeline 221, natural gas pressure reducer 222, natural gas cut-off valve 223.

First, the supply process of natural gas is described according to FIG. 1 . The natural gas shut-off valve 223 is opened during engine operation, and the high-pressure natural gas stored in the natural gas cylinder 201 reaches the design pressure after being decompressed by the natural gas pressure reducer 222 , and flows into the voltage stabilizer 220 from the natural gas pipeline 221 , to stabilize the natural gas pressure, keep the pressure stable in the working process, and then enter the mechanical heat exchanger 219 to roughly adjust the temperature of the natural gas, and then flow into the electronic control injector 217, the electronic control system ECU202 according to the operating conditions of the engine and the air flow The air flow rate measured by meter 214 is used to calculate the amount of natural gas injected. The injected natural gas is mixed with air in the mixer 216, passes through the electronic throttle valve 215, and flows into the natural gas engine 205 to burn and perform work to provide power for the vehicle. After the exhaust gas burned by the natural gas engine 205 enters Further processing is carried out in the processing system 204 and discharged to the atmosphere. The air supply process is that the mixed gas enters the exhaust pipe after the natural gas engine 205 burns and performs work. The exhaust gas has a certain amount of available energy. The compressor at 206 does work on the air, and the pressure and temperature of the air increase. After being cooled by the intercooler 207, the pressurized air enters the mixer 216 through the air pipeline 211 and mixes with the injected natural gas.

The invention patent describes the response process of the natural gas engine by taking the load sudden increase as an example. The natural gas engine is a premixed combustion, and the adjustment process of its power and speed belongs to quantity regulation. During the air intake process, the electronic control unit ECU202 of the natural gas engine calculates the The required basic injection quantity of natural gas is obtained, and the basic injection quantity is corrected according to parameters such as intake air temperature to calculate the actual injection quantity, and control the electronically controlled injector 217 to inject natural gas into the mixer. When the load suddenly increases, the speed of the natural gas engine 205 decreases. According to the feedback, the electronic control system ECU202 should increase the injection amount of natural gas to improve the engine's ability to work externally, so that the speed returns to a given speed.

According to the natural gas engine gas supply system of this prior art, the injection amount calculated by the electronic control system ECU202 is controlled by the air flow and MAP, and the MAP has been calibrated in advance, and the air flow is affected by the opening degree of the electronic throttle valve 215 and the increase of the supercharger 206. pressure control. After the electronic control system ECU collects the feedback information, the increase of the air flow is affected by the responsiveness of the supercharger 206 and the responsiveness of the opening of the electronic throttle valve 215, among which the electronic throttle valve 215 is directly controlled by the electronic control system ECU and responds quickly , the supercharging capability of the supercharger 206 is affected by intake air, combustion, and exhaust, and the response is relatively slow. In addition, after the air is pressurized, it needs to flow through a long pipeline to reach the front section of the mixer 216 . As a result, it takes a long time for the electronic control system ECU to receive the feedback information to adjust the injection quantity of natural gas, and the dynamic response of the engine is relatively slow.

The two-way fuel gas supply system of the natural gas engine of the present invention is shown in Figure 2. The gas supply system of the natural gas engine adopts the mode of coupling work of the main mixed gas supply system and the auxiliary mixed gas supply system. It is mixed with air and supplied to the natural gas engine 205. The auxiliary mixed gas supply system compensates a certain flow of air and natural gas to improve the response of the engine when the load suddenly increases, so that the engine speed is stable and the response is sensitive.

The main mixture supply system mixes natural gas and air and supplies them to the engine when the engine is running stably. When the engine is running stably, after being supercharged by the supercharger 206, the air is cooled in the intercooler 207, and then enters the mixer 216 through the air pipeline 211 to mix with natural gas, and the air flow meter 214 installed in the air pipeline 211 measures the air The electronic control system ECU202 calculates the amount of natural gas injection according to parameters such as the air flow rate and engine speed, and injects the natural gas into the mixer 216 through the electronically controlled injector 217 to mix with the air. When the load of the natural gas engine 205 suddenly increases, the electronic control system ECU202 collects changes in the engine speed, and after calculation, outputs control signals to the electronic throttle valve 215 and the auxiliary air flow control valve 212 of the engine to increase the opening of the electronic throttle valve 215, The auxiliary air flow control valve 212 is opened, a part of auxiliary air enters the mixer 216 through the auxiliary air pipeline 210, and the auxiliary air flow meter 213 collects the auxiliary air flow as a feedback signal to control the subsequent flow of the auxiliary air. The amount of natural gas injection is calculated from the air, and the injection enters the mixer 216 to mix with the air and then enters the natural gas engine 205. After the engine speed stabilizes, the auxiliary mixed gas supply system stops working, and the main mixed gas supply system provides mixed gas for the natural gas engine 205.

The electronic control system ECU202 simultaneously controls the electronic throttle valve 215 of the main mixed gas supply system and the auxiliary air flow control valve 212 of the auxiliary mixed gas supply system to control the total natural gas injection volume and air flow according to the operating conditions of the natural gas engine 205 to achieve The purpose of improving the responsiveness of the natural gas engine 205 .

The auxiliary air mixture supply system does not depend on the supercharging degree and responsiveness of the supercharger 206 of the engine. The opening degree and air flow of the auxiliary air flow control valve 212 are controlled by the electronic control system ECU 202 to supply additional air and air to the natural gas engine 205. natural gas.

The auxiliary mixed gas supply system includes a compressed air tank 208, the compressed air is stored in the compressed air tank 208, and enters the mixer 216 after passing through the auxiliary air pipeline 210 and the auxiliary air flow control valve 212; An air flow meter 214 is provided between the valve 212 and the mixer 216 .

The amount of natural gas supplied by the main gas mixture supply system is determined by the electronic control system ECU202 according to operating parameters such as engine speed and torque parameters and the pre-calibrated MAP map; The law of change of 215 and the rate of change of engine speed control the amount of additional air and natural gas supplied.

In addition, the present invention provides a control method for operating the two-way gas supply system of the natural gas engine, as shown in FIG. 3 .

In step S301, if the engine is running stably, the electronic control system ECU202 controls the opening of the electronic throttle valve 215 at a stable position, collects the engine speed, air flow, etc., calculates the natural gas flow according to the air-fuel ratio calibrated by MAP, and injects it into the mixture Device 216 to make the engine run stably.

In step S302, when the load of the natural gas engine changes, the electronic control system ECU judges whether to start the auxiliary gas supply system according to the fluctuation of the speed and the preset threshold value. If the load changes slowly, the main mixture supply system will adjust the mixture gas supply.

In step S303, if the speed fluctuation threshold exceeds the preset value, the auxiliary gas supply system is activated, the main mixed gas supply system and the auxiliary gas supply system work simultaneously, and additional natural gas and air are supplied before the supercharger 206 responds, Improves engine responsiveness.

In step S304, after the natural gas enters a stable operation state, the auxiliary gas supply system stops working and enters a waiting state.

In addition, the present control strategy is only described with an example of a sudden load increase. When the throttle opening changes suddenly and greatly, the response of the natural gas engine can also be improved by using the control strategy of the present invention.

It should be noted that the present invention has been described above with the example of a gas supply system for a natural gas engine. However, the present invention is not limited thereto, but can be applied to other gas engines that exist or appear in the future.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (9)

1. a natural gas engine two-way gas supply system, comprise electric control system ECU, natural gas engine and for the gas supply system to natural gas engine supply mixed gas, it is characterized in that, described gas supply system comprises: main mixture supply system and auxiliary mixed gas supply system; The flow of described main mixture supply system and auxiliary mixed gas supply system is respectively by electric control system ECU control;

Described main mixture supply system comprises: natural gas storage device, decompressor, voltage stabilizer, mechanical thermal exchanger, electrically controlled injector and mixer connect successively by gas pipeline; Access mixer after pressurized machine is connected by air pipe line with intercooler;

Rock gas enters mixer through decompressor, voltage stabilizer, mechanical thermal exchanger, electrically controlled injector successively; Ambient air enters mixer and mixes with rock gas through engine supercharger, intercooler successively;

Described auxiliary mixed gas supply system comprises: access mixer after pressurized air storage device is connected by auxiliary-air line with auxiliary flow control valve; Pressurized air enters the auxiliary air mass flow that increases of mixer through auxiliary flow control valve.

2. a kind of natural gas engine two-way gas supply system as claimed in claim 1, is characterized in that, also comprises:

Described mixer is connected with natural gas engine through electronic throttle, and described electrically controlled injector is connected with electric control system ECU respectively with electronic throttle.

3. a kind of natural gas engine two-way gas supply system as claimed in claim 1, is characterized in that, on the pipeline that described mechanical thermal exchanger is connected with electrically controlled injector, natural gas flowmeter is set, described natural gas flowmeter is connected with electric control system ECU.

4. a kind of natural gas engine two-way gas supply system as claimed in claim 1, is characterized in that, on the air pipe line that described intercooler is connected with mixer, Air flow meter is set, described Air flow meter is connected with electric control system ECU.

5. a kind of natural gas engine two-way gas supply system as claimed in claim 1, it is characterized in that, auxiliary air flow meter is set on the auxiliary-air line that described auxiliary flow control valve is connected with mixer, and score is not connected with electric control system ECU described auxiliary flow control valve with auxiliary air flow.

6. a kind of natural gas engine two-way gas supply system as claimed in claim 1, is characterized in that, the outlet port of described pressurized air storage device arranges air cutoff valve.

7. a kind of natural gas engine two-way gas supply system as claimed in claim 1, it is characterized in that, the Exhaust Gas of described natural gas engine is discharged through catalysis preprocessor, outlet port at described catalysis preprocessor arranges exhaust gas oxygen sensor, and described exhaust gas oxygen sensor is connected with electric control system ECU.

8. a method for natural gas engine two-way gas supply system as claimed in claim 1, is characterized in that, comprising:

When motor stable operation, provide mixed gas by main mixture supply system for motor; Electric control system ECU calculates emitted dose according to the MAP figure of air mass flow, engine running parameter and demarcation in advance, controls the amount of natural gas of electrically controlled injector ejection;

Engine load change and engine speed during with original stable operation compared with the value of the fluctuation of speed while exceeding setting threshold, by main mixture supply system and auxiliary mixed gas supply system jointly for motor provides mixed gas; Electric control system ECU gathers the variation of engine speed, controlling electronic throttle aperture increases, and open auxiliary air flow control valve, by gathering the flow of auxiliary air and the variation of engine speed, control in real time the mixed gas flow of auxiliary mixed gas supply system;

After engine speed is stable, auxiliary mixer supply system quits work, and main mixture supply system continues as motor mixed gas is provided.

9. the method for a kind of natural gas engine two-way gas supply system as claimed in claim 8, it is characterized in that, electric control system ECU is controlled the electronic throttle of main mixture supply system and the auxiliary air flow control valve of auxiliary mixer supply system simultaneously, natural gas injection amount and the air mass flow total according to the Operation Conditions control of motor.