A detailed numerical simulation was carried out to investigate the 1+1/2 counter-rotating turbine performance with different openings of high-pressure guide vane and turbine expansion ratios.By analyzing the results

the variable high-pressure vane could effectively control the massflow of 1 1/2 counter-rotating turbine; when the high-pressure guide vane was opened

there was a peak turbine efficiency with the change of the expansion ratio

when the high-pressure guide vane was closed

the efficiency decreased steadily with the reduced expansion ratio

and the efficiency reduced more quickly than that when the high-pressure guide vane was opened; in the case of the lower expansion ratio

the efficiency improved with the increase of the opening of the high-pressure guide vane

and the improvement was more obvious with the decrease of expansion ratio

which is significantly different from the efficiency of conventional turbine that generally decreases in the variable guide vane; the results show that the opened high-pressure guide vane is favorable for the specific work ratio(SWR) of high-pressure turbine to that of low-pressure turbine remained within reasonable limits.