Low pressure turbine (LPT) blades must be carefully designed in order to perform well under demanding operating conditions. They require a very aggressive turning angle (Figure 1-1a) to provide maximum power during take-off and sufficient power for auxiliary systems during flight. At very high altitudes, the flight Reynolds number drops significantly, which can produce a laminar boundary layer along the surface of the blade. This laminar boundary layer is susceptible to separation, a condition that greatly diminishes the efficiency of the turbine (Figure 1-1b). For example, Sharma et al.1 reported an increase in blade loss coefficient of 300% as a result of the boundary layer separation.
Much research has been conducted in an effort to find a method of reducing the laminar boundary layer separation in LPTs. Lake et al.2 determined that a modification of the actual blade surface (for example, by adding dimples) successfully decreased the separation-induced losses. Volino3 experimented with 2D spanwise bars that act as boundary layer trips and thus prevent suction surface separation. However, passive methods of flow control such as these may inhibit proper turbine performance at design conditions and/or increase blade heat transfer. Active methods of flow control, although more difficult to implement, are preferred as they can be adapted in-flight according to the current flight conditions.
What is the purpose of this Guide?
This Guide is intended to be used for the administration of Federal award programs administered by the Office of Grants and Training (G&T) in conjunction with the provisions of the Office of Management and Budget (OMB) circulars and government wide common rules applicable to grants and cooperative agreements, program guidelines, application kits, special conditions, terms and conditions, G&T information bulletins, and DHS policy, regulations and statutes. Below is a
list of the most commonly used circulars with which grant recipients should become familiar.
This document is provided for the use of all recipients and their subrecipients of Federal award programs administered by G&T. This Guide is to serve as the primary reference for financial management and grants administration.
Virtual teams are “groups of geographically, organizationally and/or time dispersed workers brought together by information and telecommunication technologies to accomplish one or more organisational tasks” (Powell, Piccoli & Blake, 2004,), or as Grundy (2004) states working virtual means working together apart.
