Exergy Analysis of the Revolving Vane Compressed Air Engine

Abstract

Exergy analysis was applied to a revolving vane compressed air engine. The engine had a swept volume of 30 cm3. At the benchmark conditions, the suction pressure was 8 bar, the discharge pressure was 1 bar, and the operating speed was 3,000 rev·min−1. It was found that the engine had a second-law efficiency of 29.6% at the benchmark conditions. The contributors of exergy loss were friction (49%), throttling (38%), heat transfer (12%), and fluid mixing (1%). A parametric study was also conducted. The parameters to be examined were suction reservoir pressure (4 to 12 bar), operating speed (2,400 to 3,600 rev·min−1), and rotational cylinder inertia (0.94 to 2.81 g·mm2). The study found that a higher suction reservoir pressure initially increased the second-law efficiency but then plateaued at about 30%. With a higher operating speed and a higher cylinder inertia, second-law efficiency decreased. As compared to suction pressure and operating speed, cylinder inertia is the most practical and significant to be modified.

Analysis of a novel rotating disk cylinder engine concept for power generation

“…Results show that, for a constant inlet pressure, the isentropic efficiency decreases as the angular velocity of the main rotor increases. This result was also found by Subiantoro et al 27 Figure 5 shows the required pressure on a cylindrical piston of the main rotor to overcome the constant power load of 500 W at 500 rpm (see Table 1) if a single secondary rotor is considered. It should be noted that for a single secondary rotor, the pressure requirement is initially very high due to the initial small torque radius, L, as shown in Figure 4.…”

“…Results show that, for a constant inlet pressure, the isentropic efficiency decreases as the angular velocity of the main rotor increases. This result was also found by Subiantoro et al…”

“…37 Furthermore, the device can be applied as a compressor/expander unit in a heat pump. 38 According to Subiantoro et al, 27 leakage can be one of the main issues for rotary engines, while lubrication and sealing are listed as disadvantages according to Bao and Zhao. 12 Leakage is also a relevant issue for other volumetric expanders.…”

“…Other advantages include low speeds, the possibility of using liquids and wet vapours as working fluid, and low maintenance . According to Imran et al, vane expanders can be further classified into rotary vane expanders and revolving vane expanders, where the cylinder rotates with the rotor, reducing friction. According to Subiantoro et al, rotary engines are usually more compact and have better noise characteristics and fewer components in comparison with reciprocating engines.…”

“…Exergy analysis is often applied to determine the performance of a system, but it can also be applied in the form of entropy generation minimisation . Subiantoro et al applied exergy analysis to a revolving vane compressed air engine. The study found that the second‐law efficiency decreased with higher operating speed and higher cylinder inertia.…”