Synchronous automatic measurement device and method for air-fuel ratio of compressed natural gas engine

Abstract

The invention discloses a synchronous automatic measurement device and a synchronous automatic measurement method for an air-fuel ratio of a compressed natural gas engine. An air flow meter, an air throttle position sensor, an air inlet pressure sensor and an air inlet temperature sensor are sequentially arranged on an air inlet pipe; two ends of an inlet valve displacement sensor are connected with an inlet valve and a cylinder cover respectively, and two ends of an exhaust valve displacement sensor are connected with an exhaust valve and the cylinder cover respectively; a three-way catalytic converter and a wideband oxygen sensor are arranged on an exhaust pipe; a revolution speed sensor is arranged at the shaft end of a crank-link mechanism; and an electric control unit is connected with the air flow meter, the air throttle position sensor, the air inlet pressure sensor, the air inlet temperature sensor, the inlet valve displacement sensor, the exhaust valve displacement sensor, the revolution speed sensor, the wideband oxygen sensor, a spark plug and an injector respectively. According to the device and the method, opening signals of the inlet valve and the exhaust valve of the engine are used as triggering signals for synchronous data acquisition, and synchronous automatic measurement of the air-fuel ratio of the compressed natural gas engine is realized.

Description

Technical field [0001] The invention relates to a device and a method for synchronously measuring the air-fuel ratio of a compressed natural gas engine. It is suitable for the air-fuel ratio measurement of various vehicle compressed natural gas engines. Background technique [0002] Compressed Natural Gas (CNG) as a vehicle fuel has good economy and low emission pollutants. At present, CNG vehicles generally use three-way catalytic conversion technology. According to the working characteristics of the three-way catalytic converter, when the air-fuel ratio of the CNG engine mixture is near the theoretical air-fuel ratio 17, HC, CO and NO can be used. X The purification rate of the three harmful gases has reached the highest. When the engine is in a stable working condition, the electronic control system can accurately control the air-fuel ratio near the theoretical air-fuel ratio by detecting the intake air volume and adopting the oxygen sensor closed-loop control. However, when...

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Problems solved by technology

[0003] When the CNG engine is in a transitional condition, the signals output by sensors such as throttle position, speed, intake pressure, and intake flow at a certain moment only indicate the operating parameters of the engine at that moment, and these operating parameters will change at the next moment. Therefore, there must be a large error in controlling the air-fuel ratio by detecting the intake air flow rate; in addition, using the oxygen sensor signal feedback to control the air-fuel ratio cannot meet the real-time requirements when the engine is in transition, because the signal of the oxygen sensor indicates the concentration of the combusted mixture. And the air-fuel ratio of the next working cycle has changed

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