Research On NO_x Emission Test For Diesel Engine Based On Tunable Diode Laser Absorption Spectroscopy

In recent years,the problems of atmospheric environment have become the focus of social concern.Marine diesel engine emissions is the main source of air pollution gas.In order to reduce emissions,external reducing emission measures have been applied,but it is difficult to meet the new standard.In order to fundamentally solve this problem,we need to research from the source of the pollutant generation---the process of diesel engine combustion.The components of diesel engine emissions contains a lot of combustion information,which can reflect cylinder combustion characteristics.The duration of diesel engine combustion process is short,so it has a higher demand for the dynamic response characteristics of the test method.The current test methods are mostly sampling analysis whose dynamic response characteristic is bad,and can not obtain components information of diesel engine real-time emissions.Therefore,it is necessary to develop a test method for real-time measuring the components of diesel engine emission.This paper bases on the tunable diode laser absorption spectroscopy(TDLAS),and the feasibility of real-time measuring the components of diesel engine emission is researched.First,the characteristics of gas detection methods and their applications in testing the diesel engine emission are analyzed.An on-line measuring device has been put forward to carry out diesel engine emission measurement based on TDLAS technology.Aiming at the characteristics of the diesel engine emission,carry out theoretical analysis and numerical simulation work.Influence rule of temperature and pressure parameters on molecular spectral parameters is specially analyzed.Combining with the fluctuant characteristics of environmental parameters,a quantitative correcting algorithm is given.Second,an optical test platform based on TDLAS technology is designed and built.Choosing NO as the target gas and matching a known concentration mixed gas in the laboratory.Carry out steady-state concentration test experimental research by direct test method and harmonic test method.In the experiment,research on the influence of the flow and concentration change conditions for the test.And the test results are consistent with the true value.Meanwhile,in order to avoid the influence generated by the signal light loss which the unknown concentration particulate matter of diesel engine emission causes,put forward a measurement method of the normalized 2f signal by the 1 f signal.At last,the on-line test experiment based on TDLAS technology test system is studied on TBD620 diesel engine platform.The dynamic response speed of the system can reach to the order of millisecond.Comparing with the AVL Emission Analyzer,the accuracy can reach more than 95%.Subsequently,the NOx emission characteristics are researched on D4114B diesel engine platform.The law of the NOx emission is obtained.Through the research of this paper,the feasibility of TDLAS test system in the measurement of diesel engine emission can be proved.Real-time online emission measurement of diesel engine can be realized with the high dynamic response and test precision of the system.