Low drag flameholder

Abstract

A flameholder formed of two streamlined bodies separated by a gap forming acer. The combustible fuel fed upstream of the flameholder fills the gap where it is ignited with the gap acting as a piloting zone continuously igniting the flowing mixture which is replenished.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention.

This invention pertains to flameholders for holding a piloting flame in a combustor.

2. Description of the Prior Art.

In the past, recirculation zones for flameholding have been created by the use of a bluff body. The bluff body has a separation and recirculation zone in its near wake. The bluff body is a high drag device and the size of the unconfined recirculation zone is dependent on local flow conditions and is inherently unsteady due to the nature of the vortex shedding.

The primary advantage of the invention is that the flameholding zone is provided by a shape that is low in drag. The drag is low because the gap is always filled, hence the mixture flow sees essentially an aerodynamically smooth configuration. Since the recirculation zone is constrained to be of a constant size, this flameholder will operate over a wide range of flow conditions.

SUMMARY OF THE INVENTION

An object of this invention is to create a stable recirculation zone to hold a piloting flame in a ramjet combustor.

The invention is a flameholder of a generally spheroidal configuration formed of two streamlined bodies separated by a gap-forming spacer. The combustible fuel which comes from upstream of the flameholder fills the gap where it is ignited. The gap acts as a piloting zone by continuously igniting the flowing fuel mixture which is replenished by a scavenging process.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE shows a side elevational view of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention comprises forward and rearward streamlined bodies of revolution 1 and 2, respectively, separated by spacer 3. This results in a generally spheroidal configuration of the invention with a gap between bodies 1 and 2. The flameholder is fastened to a combustor wall by one or more streamlined struts 4. Fuel flows through the strut via conduit 7, indicated by dashed lines, in the direction of the arrows. The fuel is introduced into the combustor through injector 6 in a direction opposite to the air flow.

The fuel mixes with the air in such a way that a combustible mixture results. This mixture is carried down stream and fills the gap or recirculation zone between bodies 1 and 2 where it is ignited. As the fuel-air mixture flows over the gap a scavenging process takes place at the boundary between the flowing mixture and the stagnant gases in the gap thus replenishing the mixture that is burned in the gap. The gap then acts as a piloting zone, continuously igniting the flowing mixture and at the same time being replenished by it.

Claims

What is claimed is:

1. A flameholder for use in a combustor comprising:

First and second streamline paraboloidal shaped bodies each having a vertex and an end surface portion;

cylindrical spacer having its diameter substantially smaller than the diameter of said end portions and positioned between said first and second bodies with the flat surface ends of said spacer in contact with the end surface of the first and second bodies to form a substantial gap therebetween;

a streamline strut attached to one of said bodies for holding said flameholder in spaced relationship to the wall of a combuster with the longitudinal axis of said flameholder parallel to air flow through the combustor; and

a fuel conduit extending through said strut and through the axis of at least one of said bodies to terminate at the vertex of said body on the upstream side of the air flow;

whereby flow of fuel through the conduit exits into the air stream at the vertex forming a combustible mixture that is carried over the surface of the upstream body to the gap area to replenish the mixture of gases within the gap establishing a stable recirculation zone at a piloting flame.