Fully active electrohydraulic control of a quarter-car test rig is considered from both a modelling and experimental point of view. This paper develops a nonlinear active hydraulic design for the active suspension system, which improves the inherent trade-off between ride quality and suspension travel. The novelty is in the use of pole assessment controller to drive a nonlinear active suspension with a new insight into the model through consideration of a new term, friction forces. Therefore, this model has taken into account the dynamic inclination angle [Formula: see text] between linkage and actuator regardless of the fact that the designer made an only vertical motion (bounce mode) of the wheel and body units. The second contribution of this paper is that it investigated the control force generation, therefore, the nonlinear hydraulic actuator whose effective bandwidth depends on the magnitude of the suspension travel, which incorporates the dynamic equation of servovalve, is deeply researched. The nonlinear friction model is accurately established, which relies on the dynamics system analysis and the fact of slipping the body on lubricant supported bearings; this model will caption all the friction behaviours that have been observed experimentally. In addition, the hydraulic system is used to generate the system inputs as a road simulator. The controller smoothly shifts its focus between the conflicting objectives of ride comfort and rattle space utilisation, softening the suspension when suspension travel is small and stiffening it as it approaches the travel limits. Thus, the nonlinear design allows the closed-loop system to behave differently in different operating regions. The improvement achieved with our design is illustrated through comparative experiments and simulations. C++ compiler environment is used to simulate the physical system to be controlled. The results show good servo control and fast regulation of abrupt disturbances.
Exhaust gas recirculation (EGR) is one of the main techniques studied over the years to enable the use of oxyfuel combustion for carbon capture and storage (CCS). However, the use of recirculated streams with elevated carbon dioxide poses different challenges from the control of the flow rates and flue stream characteristics to the suppression of unwanted instabilities during the combustion process. Therefore, this study evaluates the use of various CO2 enriched methane blends and their response towards the formation of a great variety of structures that appear in swirling flows, which are the main mechanism for combustion control in current gas turbines systems. The study uses a 100kW acoustically excited swirlstabilised burner to investigate the flow field response. The results showed improved thermal efficiency of the system with high swirl and forcing while the blend of CO2 with methane balanced the heat release fluctuation with a corresponding reduction in the acoustic amplitudes of the system for a smooth running, suggesting that certain CO2 concentrations in the fuel can provide more stable flames at a certain carbon dioxide concentration.
Increasing interest in alternative fuels for gas turbines has motivated research in gaseous fuels other than natural gas. Methane enriched with hydrogen or diluted with carbon dioxide are of considerable interest. The latter seems quite relevant for development of technologies such as oxyfuel combustion for carbon capture and storage in order to control temperatures in the combustion chamber. Thus, this paper presents an experimental study on the combustion of methanecarbon dioxide mixtures at atmospheric conditions. Gas mixtures have been examined by using different levels of premixing with different injection strategies with and without swirl and with and without central injection. A 20 kW burner has been used to investigate the flame stability and emissions performance by using these blends to examine the effect of CO2 addition. The burner configuration consisted of a centre body with an annular, premixed gas/air jet introduced through five, 60° swirl vanes. A TESTO 350XL gas analyzer was used to obtain NOx and CO emission trends to characterize all the injection regimes whilst using different fuel blends. CH chemiluminescence diagnostics was also used and correlated to the levels of emissions produced during the trials. The resulting images were analysed using Photron FASTCAM PFV ver 2.4.1.1 software and MATLAB R2015a. CO2 dilution decreased flame stability and operability range. The introduction of CO2 reduces temperatures in the combustion zone thus causing a reduction in emissions of nitrous oxides across all equivalence ratios. CO emissions also decreased with a limited (15%) CO2 addition. In terms of injection regimes, the outer purely premixed injection regime has lower NOx and CO, as expected. CH chemiluminescence distribution indicated that pure methane with central injection produced high fluctuation in CH production. The use of central premixed injection produces the most chaotic CH production case, possibly as a consequence of production of radicals in the central recirculation zone.
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