초록 ▼

Measurements of net thrust of an aeroengine on a thrust balance in a test cell must be corrected to gross thrust and it is also advantageous to detect changes in the airflows into and through the test cell of a magnitude sufficient to alter significantly the thrust correction factor. The invention c

Measurements of net thrust of an aeroengine on a thrust balance in a test cell must be corrected to gross thrust and it is also advantageous to detect changes in the airflows into and through the test cell of a magnitude sufficient to alter significantly the thrust correction factor. The invention can accomplish both these objectives by obtaining measures of the static pressures p i and p e in planes i and e respectively of the test cell using pressure probes 29 and 31, and utilizing the measures of p i and p e (a) in a function of the form ##EQU##D=f(p i, p e ) where D is the thrust correction necessary to convert the net thrust reading on the thrust balance to gross thrust, and (b) to monitor variations of p i and p e with respect to the net thrust and detect such of these variations as are outside predetermined limits of variation, such detection indicating the occurence of changes in the characteristics of the airflows sufficient to alter significantly the value of D.

대표청구항 ▼

1. A method of correcting thrust measurements in an aeroengine test cell in respect of an aeroengine installed for testing therein, said aeroengine having an air-washed external surface with an upstream end and a downstream end with respect to airflow thereover, and said testing of said aeroengine i

1. A method of correcting thrust measurements in an aeroengine test cell in respect of an aeroengine installed for testing therein, said aeroengine having an air-washed external surface with an upstream end and a downstream end with respect to airflow thereover, and said testing of said aeroengine involving the correction of net thrust measurements X B to gross thrust measurements X by means of a thrust correction D representing the drag due to air-flows into said aeroengine, over said air-washed external surface of said aeroengine, and through said test cell, where X B =X-D, said test cell having; air inlet means for allowing air to enter said test cell to supply said aeroengine, exhaust means whereby efflux from said aeroengine plus air entrained into said efflux from within said test cell is exhausted from said test cell, and thrust balance means for measuring said net thrust X B of said aeroengine in said test cell: said method comprising; obtaining, during testing of said engine, a measure of static pressume p i at an "inlet" location i in said test cell, and a measure of static pressure p e at an "exit" location e in said test cell, said location i being downstream of said air inlet means and upstream of said aeroengine and said location e being spaced outwardly from, but in substantial registration with, said downstream end of said air-washed external surface of said aeroengine, and calculating the value of D by utilising said measures of p i and p e in a function of the form D=f(p i, p e ) 2. A method according to claim 1, wherein ##EQU##D=A i [Δp i (1+λ e )/(1+λ i )-(2A'-1)M e 2 /K e 2 ]