The dual-inlet liquid-spray-fuelled sudden-expansion combustors are frequently adopted in ramjet engines. The original combustors with swirlers in the inlet tubes frequently suffer from poor ignition, low flame stabilization and poor combustion performance due to insufficient sizes of recirculation zones in the head part of the combustor. There are only very small recirculation zones behind the swirlers. To improve the performance of the combustors, a new configuration is proposed by the authors, in which a small central tube instead of the original swirler is mounted in the inlet tube of the combustor with a tangential angle for creating swirling flows and enlarging the recirculation zones. So, it is expected to know the gas-droplet flow behavior after mounting the central tube. The turbulent swirling and recirculating gas-droplet flows in a dual-inlet sudden-expansion combustor are very complex. In the head part of the combustor there are recirculating flows. In the whole combustor there are swirling flows with a Rankine-vortex structure (solid-body rotation plus free vortex) of tangential velocity profiles. There should be obvious velocity slip between the gas and droplet phases due to the differences in inertia and centrifugal forces. The recirculating and swirling gas-particle flows were previously measured using LDV or PDPA［1～3］. In this paper the experimental studies on two-phase flows were carried out in a cold model of the combustor, and the motion of solid particles is used to simulate that of liquid droplets. The gas and particle (simulating the droplets) velocities were measured using a 2-D LDV system and the particle (simulating the droplet) concentration distribution is measured using a laser optic fiber system and a sampling probe. The purpose of this experimental study is not to simulate the real combustion regime, but to understand the features of the improved two-phase flow field using a central tube in the inlet tube and to provide the data for validation of numerical modeling.
展开▼
