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In this paper, an experimental and numerical study on the flow evolution and energy extraction performance of a flapping-airfoil power generator is conducted, and wide ranges of motion parameters are considered. PIV (Particle image velocimetry) method is used for flow visualization around the flapping airfoil, and numerical simulations predicting the flow field and power generation process are also conducted and compared with the test results. It is found that the computed flow field basically agrees well with the experimental results, and the power generation ability of the power generator is validated. At a fixed plunging amplitude H0, both the decreasing reduced frequency k at a fixed pitching amplitude θ0, and the increasing θ0 at a fixed k lead to larger sizes of flow separation. For the flapping motion studied, both plunging contribution and pitching contribution play important roles in the energy extraction, which is very different from the traditionally imposed flapping profile. Besides, at a fixed k, the increasing H0 induces a slight increase in pitching contribution, and the increasing θ0 is beneficial to power generation enhancement. Moreover, the increasing H0 induces a notable increase in output power at relatively low k, while it has little effect on efficiency enhancement.

In this paper, an experimental and numerical study on the flow evolution and energy extraction performance of a flapping-airfoil power generator is conducted, and wide ranges of motion parameters are considered. PIV (Particle image velocimetry) method is used for flow visualization around the flapping airfoil, and numerical simulations predicting the flow field and power generation process are also conducted and compared with the test results. It is found that the computed flow field basically agrees well with the experimental results, and the power generation ability of the power generator is validated. At a fixed plunging amplitude H0, both the decreasing reduced frequency k at a fixed pitching amplitude θ0, and the increasing θ0 at a fixed k lead to larger sizes of flow separation. For the flapping motion studied, both plunging contribution and pitching contribution play important roles in the energy extraction, which is very different from the traditionally imposed flapping profile. Besides, at a fixed k, the increasing H0 induces a slight increase in pitching contribution, and the increasing θ0 is beneficial to power generation enhancement. Moreover, the increasing H0 induces a notable increase in output power at relatively low k, while it has little effect on efficiency enhancement.

Abstract With the widespread application of pulse turbochargers in internal combustion engines, steady or quasi-steady turbine models are no longer qualified for on-engine turbine performance prediction. Pulsatile flow condition caused by the reciprocating nature of the engine results in strong unsteadiness across the turbocharger turbine, which makes the turbine performance departing from that under steady or quasi-steady conditions. Modelling turbocharger turbine through a one-dimensional (1D) method is an important approach to simulate the unsteady performance of the turbine. In this paper, a 1D performance model of turbocharger turbines is presented. The model solves the turbine volute flow with 1D viscous equations, with volute curvature and circumferentially continuously flow exiting at volute outlet considered. The circumferential flow non-uniformity at volute outlet is preserved. The turbine rotor is modeled with multiple meanline models. The model was used to simulate the performance of a mixed-flow turbine and validated by the experimental data. Results show that the performance predictions are in good agreement with the experimental data. Flow parameters at internal points of the turbine predicted by the 1D model were compared with three-dimensional unsteady simulation results and reasonable agreement was observed, which demonstrates the ability of the 1D model in capturing the pulse propagation.

Abstract With the widespread application of pulse turbochargers in internal combustion engines, steady or quasi-steady turbine models are no longer qualified for on-engine turbine performance prediction. Pulsatile flow condition caused by the reciprocating nature of the engine results in strong unsteadiness across the turbocharger turbine, which makes the turbine performance departing from that under steady or quasi-steady conditions. Modelling turbocharger turbine through a one-dimensional (1D) method is an important approach to simulate the unsteady performance of the turbine. In this paper, a 1D performance model of turbocharger turbines is presented. The model solves the turbine volute flow with 1D viscous equations, with volute curvature and circumferentially continuously flow exiting at volute outlet considered. The circumferential flow non-uniformity at volute outlet is preserved. The turbine rotor is modeled with multiple meanline models. The model was used to simulate the performance of a mixed-flow turbine and validated by the experimental data. Results show that the performance predictions are in good agreement with the experimental data. Flow parameters at internal points of the turbine predicted by the 1D model were compared with three-dimensional unsteady simulation results and reasonable agreement was observed, which demonstrates the ability of the 1D model in capturing the pulse propagation.

Abstract Based on the design concept of a fourth-generation smart pipe network system, this paper innovatively proposes a new TOTS (Two-supply/One-return, triple pipe structure) arrangement method for district heating systems. Moreover, to accurately predict the heat loss due to the pipeline operation of the multi-pipe system, based on the multipole calculation method, a new heat loss theoretical analytical model for the TOTS was created; additionally, a corresponding three-dimensional numerical simulation model was established, which was analyzed and numerically solved. The results showed that in comparison with thermal loss data measured by Danfoss et al., the above analytical and numerical models have a high accuracy, and the deviation is within 2%. Additionally, through calculations, it was found that the distance between the heating pipes is an important factor that affects the total heat loss from the new multi-control heating system and the actual heat exchange between pipes.

Abstract Based on the design concept of a fourth-generation smart pipe network system, this paper innovatively proposes a new TOTS (Two-supply/One-return, triple pipe structure) arrangement method for district heating systems. Moreover, to accurately predict the heat loss due to the pipeline operation of the multi-pipe system, based on the multipole calculation method, a new heat loss theoretical analytical model for the TOTS was created; additionally, a corresponding three-dimensional numerical simulation model was established, which was analyzed and numerically solved. The results showed that in comparison with thermal loss data measured by Danfoss et al., the above analytical and numerical models have a high accuracy, and the deviation is within 2%. Additionally, through calculations, it was found that the distance between the heating pipes is an important factor that affects the total heat loss from the new multi-control heating system and the actual heat exchange between pipes.