Research On Measurement Technology Of Diesel Engine Emission Temperature And Water Vapor Concentration Based On TDLAS Technology

As a kind of power machinery,diesel engine has always played an extremely important role in the field of ship propulsion.It has a series of advantages such as rapid start-up,high stability,good economy and strong reliability.The shipbuilding industry has developed rapidly this year,and along with these developments is the issue of pollution from ship emissions.Worldwide,the pollutants produced during the operation of marine power plants are an extremely important component of atmospheric pollution.In order to improve the air pollution problem,the country has repeatedly proposed new emission regulations,and traditional test methods are also difficult to meet the new requirements.Especially for the emission monitoring of ship power plants,how to achieve high accuracy and high accuracy for the operation of ship power plants The real-time online measurement of dynamic response has become an urgent problem to be solved.In this paper,Tunable Diode Laser Absorption Spectroscopy(TDLAS)is used to test the emissions of marine diesel engines.This technology can achieve fast,non-contact and high-precision real-time online measurement of marine diesel engine emissions.First,the TDLAS technology is briefly introduced,and the measurement methods and principles of the TDLAS technology are analyzed according to the spectral absorption theory and Beer-Lambert law.Then we use Simulink software for simulation analysis,select H2O as the target gas,establish a temperature measurement model and a concentration measurement model,respectively change the gas concentration,measurement temperature,pressure,optical path and other factors,analyze and study the influence of various environmental factors on the measurement results.And the principle of selecting gas absorption molecular line pairs is explained and verified.When the experiment is carried out on a diesel engine,changes in the operating conditions of the diesel engine will cause changes in various environmental factors such as temperature and pressure.Through simulation analysis,it has successfully paved the way for the experimentIn the follow-up,a measurement experiment in a steady-state environment was first carried out.The absorption gas chamber was used as the absorption environment for testing.The obtained results were compared with the measurement results of the sensor.The relative error of temperature measurement is about 3%,and the relative error of concentration is about 9%,which verifies the feasibility of the technology in the emission test of marine power plant.After that,the diesel engine emission test bench was built independently.The experimental system of exhaust temperature and H2O concentration was designed on the YC6K420LN-C31 dual-fuel marine engine.The test was carried out under different operating conditions of the diesel engine,using direct measurement and wavelength modulation method.The exhaust gas temperature is measured,and the relative error between the measurement result of the direct measurement method and the temperature sensor is between 4%and 5%,and the relative error of the wavelength modulation method is about 3%,and the latter’s measurement accuracy is significantly higher than the direct measurement method.Compare the advantages and disadvantages of the two methods through the measurement results to provide a reference for the measurement in the project.Then,the emission test of the diesel engine under variable operating conditions was carried out.The H2O concentration values of the diesel engine at different speeds and different powers were studied respectively.According to the measurement results,the combustion characteristics and emission characteristics of the diesel engine were obtained.Analysis of the cause of changes in the measured H2O concentration under conditions such as oil and intake air.Through the research work carried out this time,it is verified that the marine diesel engine emission test based on TDLAS technology can meet the requirements of high accuracy,good real-time performance,fast response speed,etc.It can provide strong support for fault diagnosis,intelligent control,optimized combustion and improved performance of marine diesel engines.