In-Motion Initial Alignment Method for LDV-Aided SINS Based on Adaptive Unscented Quaternion H-infinite Filter

With the advantages of high velocity measurement accuracy and fast dynamic response, the laser Doppler velocimeter (LDV) is expected to replace the odometer (OD) to be combined with a strapdown inertial navigation system (SINS) to form a higher precision integrated navigation system. Since LDV has higher velocity measurement accuracy and data update frequency than OD and Doppler velocity log, LDV is used for the first time to aid SINS in in-motion alignment in this paper. Considering that some approximation used in the alignment model, the uncertainty noise of the sensors during the motion process and the unknown noise parameters during the filter process, an adaptive unscented quaternion H-infinite estimator (AUSQUHE) is proposed in this paper. The proposed AUSQUHE method has high robustness since it combines the advantages of unscented quaternion estimator and H-infinite filter. And the adaptive threshold of H-infinite filter and the adaptive measurement noise covariance matrix are introduced to make the filter adapt to the environment change and accelerate the convergence of errors. The performance of the proposed method is verified by a vehicle field test with normal LDV signal and a vehicle test with LDV signal disturbed by the noise. The results show that the proposed method has higher alignment accuracy, faster convergence speed and stronger robustness than four other compared methods.

EXPERIMENTAL STUDY OF THE INLET FLOW IN A NON-PREMIXED COMBUSTION CHAMBER

The evaluation, validation and development of the models used in computation fluid dynamics requires the availability of experimental data for which the boundary conditions, especially the conditions of the inlet flow, are well defined. Laser diagnostics techniques provide experimental data used in computational fluid dynamics and are a powerful tool for measurements of the mean properties and fluctuations of the turbulent flow because they are non-intrusive methods, with high repetition rate and high spatial and temporal resolution. Therefore, in the present work an experimental study of the inlet flow (inert and combusting flows) in a non-premixed combustion chamber is presented. The velocity measurements were carried out using a laser Doppler velocimeter at the entrance region of the combustion chamber. An asymmetry on the mean flow and an increase on the total velocity fluctuations with the increase of the equivalence ratio was observed. The major effect on the increase of the equivalence ratio was a presence of a coherent movement on large scales associated to the flame brush dynamics.

Shock Measurements Based on Pendulum Excitation and Laser Doppler Velocimetry: Primary Calibration by SI-Traceable Distance Measurements

A new method is described to provide a primary calibration of shock measurements produced by a shock measurement system consisting of pendulum excitation and laser Doppler velocimetry. The method uses the laser Doppler velocimeter to determine the total distance traveled by a rigid block that slides along a Teflon (fluorocarbon) channel after being struck by a pendulum head, and the resulting distance is compared to the distance measured by an SI-traceable length measurement. The instantaneous velocity of the block is measured by the velocimeter and is used to calculate the displacement of the block by integrating the velocity data. The result is compared to the displacement measured using calibrated rulers and calipers. The method was applied to an independently calibrated commercial velocimeter for impact accelerations ranging from 2000 to 30,000 m/s2. The results of the independent mechanical-displacement measurements agreed with those from the commercial velocimeter to within ±0.3 %, with better agreement above accelerations of order 10,000 m/s2 to within ±0.1 %. A conservative, upper-bound, uncertainty analysis included the effects of noise and other random errors, as well as type B estimates for systematic errors from occasional momentary demodulation failures (dropouts), use of a different number of rulers before and after shock distance measurement, and the relative frequency response of the velocimeter.

Laser Research of the Fuel Atomization Process of Internal Combustion Engines

The paper presents test methods (mechanical, electrical and optical) for the fuel spray research in combustion engines. Optical methods, imaging and non-imaging can be used in laboratory and engine tests. Imaging methods include flash photography and holography. Their use is limited to testing droplet dimensions larger than 5 µm. Imaging methods have an advantage over non-imaging ones because they allow the droplet to be seen at the point and time where its measurement is required. Non-imaging methods can be divided into two groups: the first, which counts and measures, individual droplets one at a time, and the second, which measures a large number of droplets simultaneously. Exemplary results of research of droplet size distribution in fuel sprays are shown. In tests of atomized fuel spray, in conditions reflecting the conditions of the internal combustion engine, the size of droplets, their distribution in the spray and the velocity of individual droplets are presented. To determine the quality of the fuel spray, two substitute diameters Sauter (D32) and Herdan (D43) were selected, the first of which refers to heat transfer and the second to combustion processes. Laser research equipment including Particle Image Velocimetry laser equipment (PIV), Laser Doppler Velocimeter (LDV) and Phase Doppler Particle Analyzer (PDPA) were applied for testing fuel spray distribution for two kind of fuel. The atomization process from the point of view of combustion and ignition processes, as well as emission levels, is characterized by the best substitute diameter D43, which value is close to the median volume. The most harmful droplets of fuel in the spray are large droplets. Even a few such droplets significantly change the combustion process and emission of toxic exhaust components, mainly NOx.