Resonators Clause Samples
Resonators. In a thermoacoustic system the function of the resonator is to determine the operating frequency, to store the acoustic energy to be amplified by the thermoacoustic engine and to transfer the output power of this engine to the acoustic load which could be either a heat pump or cooler as well as an alternator. Acoustic losses in the resonator can seriously affect system performance in particular at medium and low operating temperatures. Two different options were pursued with the aim to reduce the resonator losses compared to the useful acoustic power.
3.6.1 Traveling wave resonator An analysis is performed of acoustic loss in all possible implementations of acoustic resonance and feedback circuits like ½ and ¼ standing wave, traveling wave and hybrid configurations. Calculated values are compared with experimental data from literature. For some new configuration for which no data was available experiments are performed to validate the calculation results. Coupling efficiency is defined as the ratio between power available at the load and the (equivalent) source power. This coupling efficiency is calculated and ranked for all configurations emanating from operating conditions for engine and heat pump or cooler as agreed in work package 6. In this analysis it is found that, for the same operating conditions of engine and heat pump, acoustic losses in a mechanical resonator and in a traveling wave feedback loop are significant lower as compared with the commonly used standing wave type resonator with a torus or bypass type engine or heat pump. The mechanical resonator is studied in task 4.2. The traveling wave feedback loop is further investigated within this task. A small scale experiment at atmospheric pressure with a 4-stage thermoacoustic engine utilizing the traveling wave feedback circuitry is given in Figure 31. Figure 31 Small scale experiment of travelling wave feedback in a four stage thermoacoustic engine The experiment validated the traveling wave approach by showing indeed a very low onset temperature and a steep increase of acoustic loop power with temperature difference applied. In addition to the low loss the internal gas volume is found to be more than a factor of five less than the internal volume of the standing wave version for the same operating conditions yielding a more compact system. This is particularly important for low temperature systems. In addition, the combined loss analysis of continuous and oscillatory flow performed in...