Development Of PIV Test Bench On Diesel/Natural Gas Dual Fuel Engine

Diesel/natural gas dual-fuel engine has low THC emission,low thermal efficiency at low load,and easy to knock at high load,so there is still a gap from its successful application.The flow field in the cylinder of the internal combustion engine directly affects the quality of the combustion process.Therefore,the effective measurement of the flow field in the diesel/natural gas dual-fuel engine cylinder has important reference value,which is used to analyze the combustion condition of the engine and improve the combustion and emission performance of the engine.In order to achieve experimental measurements of the in-cylinder flow field of a diesel/natural gas dual fuel engine,a flow field test platform for diesel/natural gas dual fuel engine,based on an existing optical engine,and which air intake system was modified and matched with the corresponding PIV flow field measurement system and the self-designed tracer particle generator,was initially established.A series of tests were carried out on the performance of the designed tracer particle generator,and the performance of the three tracer particles used was also compared.First,the air intake system of the existing optical engine was modified,and the natural gas supply and injection parts were added to transform the existing optical engine into a diesel/natural gas dual-fuel optical engine.Then,a tracer particle generator was developed for the diesel/gas dual fuel engine PIV test platform to provide the required tracer particles for PIV flow field measurements.Finally,using olive oil,silicone oil and alumina powder as tracer particles respectively,the tracer particle generator designed in this study was used to conduct a series of PIV flow field measurements on a simple flow platform with constant flow rate,whose flow rate is controllable.Using the relative error of PIV measurement speed as an analytical indicator,the following conclusions were obtained:1.From the two-dimensional flow field vector photographed by the PIV measurement system,it can be seen that no matter which material of olive oil,silicone oil or alumina powder is used as the tracer particle,as the flow velocity of the flow field gradually increases,the two-dimensional flow field vector has a good progressive evolution process,which can meet the requirements of analyzing the flow field flow.2.Regardless of which of olive oil,silicone oil,and alumina powder is used as the tracer particle,a similar conclusion can be drawn from the overall law of PIV measurement effect: with the mixing of labeled air containing tracer particles and pure air,the relative error of PIV measurement speed decreases gradually.And as the proportion of marked air flow in the total flow field increases,the relative error of PIV measurement speed generally decreases first and then increases.Only when the proportion of marked air flow in the total field flow is appropriate,that is the tracer particle concentration is appropriate,the relative error of the PIV measurement speed can be minimized.And as the flow velocity of the measured flow field increases,the influence of the mixing time of the marked air and the pure air on the relative error of the PIV measurement speed becomes smaller and smaller.3.When the three substances of olive oil,silicone oil and alumina powder are respectively used as tracer particles,through the comparative analysis of the relative error of PIV measurement speed,silicone oil is more suitable as tracer particles for this study,whether based on the point of all measurement data or the point of the optimal measurement data.