Feasibility of Boosting Low-Energy-Quality Steam by Using Wave Rotor

Owing to the difficult utilization of the low-pressure level in the process industry, the low-energy-quality steam is often condensed to recover the demineralized water or just discharged directly, causing a huge waste of thermal energy. A novel technology of enhancing the steam’s energy quality by using the wave rotor based on the principle of moving shockwave compression is proposed. The supercharging ability of 3-port wave rotor is studied by meaning of 1-dimension unsteady theory and computational fluid dynamic. A practical thermodynamic flowsheet of boosting the low-pressure steam driven by high-pressure steam is also proposed and analysed in detail. As an example, to boost the saturated steam of pressure 1.0 MPa to 1.953 MPa, a three-stage wave rotor solution is proposed and is verified its feasibility. The high supercharging ratio and entrainment ratio of the wave rotor are much higher than the traditional steam ejector shows the feasibility of enhancing energy-quality of low-pressure steam.

Performance analysis of wave rotor based on response surface optimization method

An optimized wave rotor refrigerator (WRR) that can convert part of the expansion work into shaft work to improve the refrigeration performance is obtained by optimization method. Bézier curve is used to establish a two-dimensional simplified model, and response surface method and NLPQL optimization algorithm are used to search for the optimal wave rotor structure. The results show that the optimized wave rotor shape is rear back bending. Compared with original rotor, the isentropic expansion efficiency of the optimized rotor is higher under different pressure ratios and relative velocity, and changes more gently under different pressure ratios. Moreover, the expansion power of the optimized rotor is mainly converted into shaft powder, while the pressure energy and thermal energy increase at the hot end is relatively small. The pressure fluctuations on the inlet and outlet sides of the optimized rotor are smoother, and the compression waves that are constantly reflected during the low-temperature exhaust stage have a smaller intensity, which helps to improve the performance of WRR. The optimized rotor can significantly reduce the entropy production in the refrigeration process, especially the entropy production by velocity gradients. When the pressure ratio is 2.0 and relative velocity is 23 m/s, the isentropic expansion efficiency increases from 56.8% of the original rotor to 62.08% of the optimized rotor.

Numerical optimisation of a micro-wave rotor turbine using a quasi-two-dimensional CFD model and a hybrid algorithm

Wave rotors are unsteady flow machines that exchange energy through pressure waves. This has the potential for enhancing efficiency over a wide spectrum of applications, ranging from gas turbine topping cycles to pressure-gain combustors. This paper introduces an aerodynamic shape optimisation of a power generating non-axial micro-wave rotor turbine and seeks to enhance the shaft power output while preserving the wave rotor’s capacity to function as a pressure-exchanging device. The optimisation considers six parameters including rotor shape profile, wall thickness, and number of channels and is done using a hybrid genetic algorithm that couples an evolutionary algorithm with a surrogate model. The underlying numerical model is based on a transient, reduced-order, quasi-two dimensional computational fluid dynamics model at a fixed operating condition. The numerical results from the quasi-two-dimensional optimisation indicate that the best candidate design increases shaft power by a factor of 1.78 and imply a trade-off relationship between torque generation and pressure exchange capabilities. Further evaluation of the optimised design using three-dimensional computational fluid dynamics simulations confirms the increase in power output at the cost of increased entropy production. It is further disclosed that increased incidence losses during the initial opening of the channel to the high-pressure inlet duct compromise the shock strength of the primary shock wave and account for the decrease in pressure ratio. Finally, the numerical trends are validated using experimental data.

Investigation of the Shock Wave Formation and Intensity in Wave Rotor

Actual formation and intensity of shock wave generated during gradual opening and closure between each port and passages of wave rotor are studied by means of experiment and computational fluid dynamics simulation. The results show that the intensity of shock wave increases with the distance from high-pressure inlet, and the reason for the variation tendency is the superposition of compression waves. By changing the rotational speed and the expansion ratio, the shock wave intensity can be adjusted, but the position where the intensity reaches maximum stays constant basically and keeps the distance near 300 mm from high-pressure inlet. Comparing with the one-dimensional simplification result, the actual intensity of shock wave is lower. The difference between the fact and simplification increases with the rotational speed and expansion ratio. The internal mechanism has been analyzed from the aspect of intake mass. Then, the maximum shock wave intensity is found approximately linear to the intake mass of each rotor passage in each cycle.

Performance Enhancement of Gas Turbine Engines Topped With Wave Rotors and Pulse Detonation Combustors

In the present research work, a novel method of integrating the conventional gas turbine engine with a Wave Rotor (WR) and a Pulse Detonation Combustor (PDC) is proposed to increase the specific work and thermal efficiency of the engine. Two gas turbine engine configurations, viz. (i) Baseline engine topped with a wave rotor and a steady flow combustor (BWRSFC), and (ii) Baseline engine topped with a wave rotor and a pulse detonation combustor (BWRPDC), have been analyzed with and without recuperative systems. In the case of BWRPDC, the principle of quasi-steady expansion of detonation products through a nozzle into the ejector to entrain and eject the bypassed compressed air along with detonation products exhausted from WR, and a steady expansion of remained detonation products of PDC through the WR to provide the required energy transfer to further compress and supply the un-bypassed compressed air to PDC, has been considered. The pressure of the ejected gases from the ejector will be 25% to 35% higher than the air pressure delivered by the compressor of baseline engine and can develop more specific work with enhanced thermal efficiency when expanded in the turbine. A computer code is developed in MATLAB to simulate the engine performance with and without recuperation / regeneration. For thermodynamic calculations, two un-recuperated micro-turbine engines called C-30 and C-60 made by Capstone Turbine Corporation are considered. C2H4/air is taken as the fuel-oxidizer. The variation in specific work, and thermal efficiency with wave rotor pressure ratio has been investigated for C-30 and C-60 engines. Further, a sensitivity analysis of the performance of BWRPDC with a change in the Entrainment Coefficient (EC) of ejector has also been made.