In order to develop a tip clearance control system for an uncooled vaneless counter-rotating turbine, tip clearance variation of its high pressure rotor blade at off-design conditions is analyzed. Aero-thermal interaction simulation is performed to predict the temperature and deformation of the solid blade. At operating conditions with rotating speeds greater than 60% design value and expansion ratios greater than 85% design value, the blade tip clearance height at leading edge remains unchanged when the expansion ratio decreases, meanwhile that at trailing edge decreased obviously. However, the tip clearance height variations at the leading edge and trailing edge are almost the same in a conventional subsonic turbine at such conditions. The cause is that the flow in the high-pressure rotor is choked at these conditions. The choked flow results in that the fluid and solid blade temperatures upstream of the throat are not affected by the back pressure and only those downstream of the throat increases with the back pressure. Consequently, the blade height at leading edge keeps constant, and that at trailing edge varies because of thermal expansion. To avoid the rubbing of the blade and case, the blade height at trailing edge is diminished by 30%. As a result, the blade tip clearance height at low speed operating conditions increases in axial direction. Such a design leads to a stronger tip leakage flow. More flow losses might be generated. Therefore, a casing cooling method is proposed to control the blade tip clearance height at leading edge and trailing edge respectively. The deformations of the casing with different mass flow rate of cooling air at design and off-design conditions are calculated. It shows that the blade tip clearance heights at leading edge and at trailing edge of the rotor can be well controlled with appropriate amount of cooling air.

为了开发用于未冷却的无叶片反向旋转涡轮的叶尖间隙控制系统，分析了其非设计条件下其高压转子叶片的叶尖间隙变化。进行空气-热相互作用模拟以预测固体叶片的温度和变形。在转速大于设计值60％且扩展比大于85％设计值的工作条件下，当扩展比减小时，前缘的叶尖间隙高度保持不变，而后缘的叶尖间隙高度则明显减小。然而，在这样的条件下，在常规的亚音速涡轮中，前缘和后缘处的尖端间隙高度变化几乎相同。原因是在这些条件下高压转子中的气流被阻塞。阻塞的流动导致喉咙上游的流体和固体叶片温度不受背压的影响，只有喉咙下游的流体和固体叶片温度随背压而增加。因此，前缘的叶片高度保持恒定，后缘的叶片高度由于热膨胀而变化。为了避免刀片和外壳的摩擦，后缘的刀片高度将减少30％。结果，在低速操作条件下的叶片尖端间隙高度沿轴向方向增加。这样的设计导致更强的尖端泄漏流。可能会产生更多的流量损失。因此，提出了一种壳体冷却方法，以分别控制前缘和后缘的叶尖间隙高度。计算了在设计和非设计条件下，不同的冷却空气质量流量下的套管变形。结果表明，使用适量的冷却空气可以很好地控制转子前缘和后缘的叶尖间隙高度。