A theoretical model is developed for the effect of the operating parameters and the geometric parameters on the Kaplan turbine performance under design and off-design conditions. In the theoretical model, the incidence loss at the runner inlet that exists under off-design conditions for both positive and negative incidence angles is taken into account. The runner internal loss and the draft tube loss, which exist even under design conditions, are also taken into consideration through the use of simple and reasonable empirical expressions. The experimental works were carried out to validate the theoretical results. An optimization technique is adopted to obtain the operating parameters that achieve the best possible efficiency of a Kaplan turbine. A chart is deduced for detecting the suitable values of the operating parameters that achieve efficiency higher than 88% for different geometric parameters of the axial flow turbine, constant runner inlet blade angle. Comparisons of the obtained results with the present experimental and available published works show an acceptable agreement

Compressors have a limited stable operating range, due to occurrence of rotating stall and surge, so many techniques were introduced to increase its stability and more enhancements still are needed for optimum performance. Two different techniques for enhancing the compressor stability are investigated in the present work. The first technique makes use of splitters with different lengths located at various positions through the diffuser passages. In the second, radial grooves with different geometric parameters are manufactured through the compressor front casing matching with the diffuser passages and the vaneless regions. Influences of various geometric parameters on the stability of the compressor using the two techniques are studied. Enhancement in the flow and pressure coefficients at stall initiation of about 22.5 % and 4.4 % respectively, could be achieved by providing the compressor with diffuser splitters. Providing the compressor with radial grooves achieves an enhancement in the flow coefficient at stall initiation reaches to 45.5 %. The flow coefficient at stall initiation resulted from the use of the radial grooves technique is given in a form of streamlines in terms of the grooves width and depth. The grooves width and depth required for optimum flow stability could be predicted from these streamlines for similar compressors. The present experimental results show an acceptable agreement with those obtained by another author using similar compressor