RU2467791C1 - Cellular mixer - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: cellular mixer consists of two gas channels divided by corrugated surface, and mixing chamber. Said corrugated surface makes honeycombs at mixing chamber inlet. Said honeycombs feature different shape and length. Mixing chamber is shaped to, preferably, cylinder.

EFFECT: threefold decrease in mixing chamber length.

2 cl, 2 dwg

Description

The invention relates to aircraft engine manufacturing.

Known turbojet engines (patents: RU 2190772, IPC F02C 3/32, 1999; RU 2386829, IPC F02C 3/32, 2010; RU 2392475, IPC F02C 7/18, 2010) containing a gas ejector with mixing chamber. The disadvantage of the gas-dynamic scheme of the turbojet engine is the large elongation of the mixing chamber (length to height ratio), which negatively affects the mass of the engines. In addition, due to high gas temperatures (more than 2000 K), problems arise with ensuring the strength of the separation surface of the gas ejector.

A known mixer formed by a set of cells (cells) and consisting of two gas channels and a mixing chamber, and the corrugated surface at the entrance to the mixing chamber forms a set of cells (patent JP 8-135504 A, IPC F02K, 1 / 48,99996).

Reducing the relative elongation of the mixing chamber while improving the cooling of the corrugated surface is achieved by the fact that the cells have different shapes and different lengths of the perimeter.

The essence of the invention lies in the fact that different shapes and different lengths of the perimeter of the cells affect the size (length) of the mixing chamber. It is known that the complete mixing of two jets in a cylindrical mixing chamber occurs in the area of 8 ÷ 12 calibers (G.A. Abramovich. Applied gas dynamics. M: Nauka, 1976, p. 560). Accordingly, the length of the mixing chamber will be the smaller, the smaller the caliber (thickness) of the mixed jets. The shape of the honeycomb allows you to deform the jet, reducing their thickness. Reducing the length of the perimeter of the cells (with the shape of the cells unchanged) also reduces the length of the mixing chamber. An increase in the contact surface area between the jets, which occurs when the length of the perimeter decreases (an increase in the number of cells is achieved) accelerates the mixture formation and, accordingly, the time required for mixing the jets decreases (in a shorter time the gas travels a shorter distance, which reduces the length of the mixing chamber). In addition, an increase in the contact surface reduces the heat load (heat flux per unit area) on the corrugated surface.

Figure 1 shows a diagram of a gas ejector.

Figure 2 shows a cross section of the entrance to the mixing chamber.

The gas ejector (figure 1) consists of two annular channels ("hot" and "cold" gas), separated by a corrugated surface, and a cylindrical mixing chamber, made in the form of a ring. The corrugated surface is deformed so that at the entrance to the mixing chamber 1 has points of contact (in the static position, technological gaps are allowed to compensate for thermal expansions).

As a result of these contacts, honeycombs are formed (figure 2). It is significant that the cells have different shapes and different perimeter lengths (Fig. 2, where the cells through which the "hot" gas passes are marked in dark color and the "cold" gas in light).

The cell mixer operates as follows.

The flows of "hot" and "cold" gas move along two channels having a common dividing surface. When the gas moves, the channel shapes change in such a way that the flows of “hot” and “cold” gases interpenetrate (mix), forming at the inlet a mixing chamber of a jet of various shapes having different perimeter lengths (Fig. 2), which, when the separation surface disappears, end up in direct contact. As a result, the gases are mixed.

Reducing the length of the mixing chamber in turbojet engines is achieved by reducing the length of the perimeter of the cells (by increasing their number) and changing the shape of the cells, which is selected experimentally.

For a turbojet engine (thrust of 150 kN) with an air flow rate of ~ 170 kg / s under start conditions, the number of cells is ~ 300 (the shape of the cells is shown in Fig. 2). In this case, the thickness (caliber) of two adjacent jets is ~ 0.05 m (the minimum size of the jets is limited by the resistance that the cells create). The required length of the mixing chamber in this case, based on the theory of similarity, is 0.4–0.6 m (10–12 gauges). For comparison, if you use a conventional flap mixer, the length of the mixing chamber will be 1.8 ÷ 2.5 m.

The use of a honeycomb mixer allows reducing the specific gravity of the turbojet engine by at least 3–5 percent (by reducing its longitudinal dimensions by 5–10 percent).

Claims (2)

1. A cell mixer, consisting of two gas channels separated by a corrugated surface, and a mixing chamber, and the corrugated surface at the inlet of the mixing chamber forms a honeycomb, characterized in that the cells have a different shape and different length of the perimeter. 2. The cell mixer according to claim 1, characterized in that the mixing chamber is cylindrical.

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