Zongjie Hu

High performance of LiMnPO4/C prepared by hydrothermal reaction

Abstract LiMnPO4/C samples were prepared by hydrothermal reaction, and also by solid state reaction for the comparison. The samples characterised by X-ray diffraction, scanning electron microscope, particle size distribution and Roman spectra. The influence of solution pH and calcination temperature on the particle size of LiMnPO4 sample was studied. Results showed that the sample synthesised at the optimal conditions of pH=6·0 and 680°C had the biggest lattice of LiMnPO4 crystal and the narrowest particle size distribution. Compared with solid state reaction, the hydrothermal reaction produced a better carbon coating to form LiMnPO4/C composite. Electrochemical property was tested by charge–discharge and cyclic voltammetry. As a result, the capacity of the optimal sample is 108 mAh g–1 and the capacity retention is 70% after 30 cycles. The Electrochemical performance of LiMnPO4/C prepared by hydrothermal reaction is better than that produced by solid state reaction.

In-cycle combustion feedback control for abnormal combustion based on digital ion current signal:

For better stability of ion current employed for in-cycle combustion diagnosis and feedback control, this research develops a digital post-processing unit for in-cylinder ion current signals. Based on the processed digital ion current signal, abnormal combustion in gasoline direct injection engine is successfully detected, and the in-cycle remedy feedback control is achieved as well. Both re-ignition and re-injection are utilized for misfiring remedy, and only re-injection is employed for knocking inhibition. The accuracy of misfiring diagnosis is achieved no less than 94%, and the re-injection combined with re-ignition operation is shown to be feasible for misfiring remedy as well. The accuracy of knocking diagnosis is around 85% (knocking rate = 20%). The re-injection under the pre-knocking condition is shown to be effective for knocking inhibition.

Simulation and experimental study on ion current under GDI-HCCI combustion mode

For a gasoline HCCI engine, the major challenge comes from the ignition and combustion control. Therefore, a feedback signal is necessary to detect combustion state and to realise closed-loop control of combustion process, and ionisation technology was studied for the purpose. The simulation results indicated that the 3D-CFD model could accurately predict in-cylinder pressure, heat release rate, ion profile, ion distribution and its generation mechanism. The experimental results showed that the fuel injection rate in NVO was of more significance to the HCCI combustion phase and the ion current, and HCCI combustion phase can be controlled by the fuel transmutation. In the wake of the excess air coefficient reducing, the amplitudes of the cylinder pressure and ion current were increased, and the phases were advanced. Under high load condition, the reduction of the throttle percentage caused increase in the fluctuation of the IMEP coefficient but weakness in the middle load.

The Influence of Diesel Nozzle Structure on Internal Flow Characteristics

Based on X-ray CT scan technology in Shanghai Synchrotron Radiation Facility (SSRF), the inner structure of a side jet single-hole nozzle was obtained and its parameters around the inlet circle were measured. Further researches were carried out with the flow rate test bench about the influences of structure parameters symmetry on the internal flow characteristics and cavitation. Results showed that: the size deviation of inlet diameter, outlet diameter and nozzle length around the inlet circle are relatively small, while the inlet rounding radius is obviously distributed unevenly. Because of that, the cavitation had already showed up when the injection pressure was 40 MPa and the critical cavitation number equalled to 1.032, which should not take place according to the traditional theory. Thus, when relative studies are carried out, it is important for researches to take fully consideration of the size deviation of nozzle structure parameters, especially for the inlet rounding radius, to achieve more reliable conclusions.

Spray characteristics of ethanol-gasoline blends from an asymmetric multi-hole injector of DISI engines

Ethanol is an attracted alternative fuel, while ethanol-gasoline blends can be a way for substituting some part of gasoline. To apply ethanol or ethanol-gasoline blends to DISI engines, the spray characteristics of various blends of the ethanol and gasoline (25%, 50%, 75% and 100% ethanol) as well as pure gasoline were investigated by means of high-speed shadow photography technique, employing a multi-hole DISI engine injector with asymmetrical nozzle-hole arrangement. A comparative analysis of fuel concentrations of ethanol-gasoline blends and pure gasoline was also presented. The results show that the spray developing patterns were slightly changed with increasing ethanol fraction in gasoline. Under low ambient pressure condition, the spray tip penetration decreased and the spray angle increased with increasing ethanol fraction in gasoline. Under the elevated ambient pressure condition, the spray tip penetration increased and the spray cone angle decreased with the more ethanol fraction in gasoline, meanwhile the spray angles of all test fuels tended to stay constant in the fully developed stage.