Numerical investigation of radial inflow in the impeller rear cavity with and without baffle

Abstract

In typical small engines, the cooling air for high pressure turbine (HPT) in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot components. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are carried out with axisymmetric and 3-D sector models for various inlet swirl ratio  0 (0-0.6), turbulent flow parameter  T (0.028-0.280) with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in reducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.impeller rear cavity, de-swirling device, baffle, Batchelor's Model, Vortex Model Citation:Liu G, Du Q, Liu J, et al. Numerical investigation of radial inflow in the impeller rear cavity with and without baffle.

Computational Investigation of Flow Control Methods in the Impeller Rear Cavity

“…The CFD results agree well with the experimental data. The effect of the baffle on the flow structure and pressure loss has been carried out in the author's previous research [15]. The results show that the biggest difference of flow characteristic in the cavity with and without baffle is that a big counterclockwise vortex exists in the stationary cavity composed of the stationary wall and the baffle surface.…”

“…The values of dimensionless parameters and boundary conditions for the numerical cases in the current paper are listed in Table 2. In recent years, many researchers such as Liu et al [15] find that for any impeller rear cavity, when β 0 and λ T are the same, the difference of C p , between the conditions with different combination of C w and Re φ , is ignorable. Therefore, the dimensionless flow parameters discussed in the current paper are β 0 and λ T .…”

“…Therefore, in the present paper, two methods, namely, baffle and swirl-controlled orifice, were proposed to regulate the pressure loss and distribution in the rotorstator cavity: (1) a baffle, shown in Figure 1(a), is installed between the rotating and stationary walls. More detailed introduction about baffle can be seen in the author's previous paper [15]. (2) Swirl-controlled orifice is shown in Figure 1(b).…”

Laboratory Measurements the Rise in Power Consumption Resulting from the Use of a Finned Rotating Disc at a Centrifugal Water Flow

“…The issues related to the distribution of pressure in the turbomachinery near-impeller space are thoroughly discussed in reference literature. In the case of pumps, the problem involves analysing axial thrust characteristics (Bhatia 2014;Dong and Chu 2016a, b;Gantar et al 2002;Golovin et al 1989;Godbole et al 2012;Hong et al 2013;Iino et al 1980;Jedral 2001;Kalinichenko and Suprun 2012;Karaskiewicz 2013;Kim and Palazzolo 2016;Lefor et al 2015;Lugova et al 2014;Matsui and Mugiyama 2009;Piesche 1989;Rohatgi and Reshotko 1974;Shimura et al 2012;Wang et al 2013;Wilk 2003bWilk , 2009Zhou et al 2013) or volume losses resulting from untight sealing (Ayad et al 2016;Bhatia 2014;Cao et al 2015;Gantar et al 2002;Kim and Palazzolo 2016;Lefor et al 2015;Liu et al 2016;Shimura et al 2012;Torabi and Nourbakhsh 2016;Wang et al 2016;Wilk and Wilk 2001). So far, experimental (Ayad et al 2016;Dong and Chu 2016b;Gantar et al 2002;Godbole et al 2012;Hong et al 2013;Iino et al 1980;Lefor et al 2015;Nemd...…”

“…So far, experimental (Ayad et al 2016;Dong and Chu 2016b;Gantar et al 2002;Godbole et al 2012;Hong et al 2013;Iino et al 1980;Lefor et al 2015;Nemdili and Hellmann 2007;Owen and Pincombe 1980;Piesche 1989;Wilk and Wilk 1996b;Wilk 2008;Zhou et al 2013) and computational (Ayad et al 2016;Cao et al 2015Cao et al , 2016Dong and Chu 2016b;Dykas and Wilk 2008;Golovin et al 1989;Hong et al 2013;Karaskiewicz 2013;Kim and Palazzolo 2016;Lefor et al 2015;Liu et al 2016;Matsui and Mugiyama 2009;Piesche 1989;Rohatgi and Reshotko 1974;Shimura et al 2012;Torabi and Nourbakhsh 2016;Watanabe et al 2016;Zhou et al 2013) tests have been carried out. Selected works are devoted to cases of the centripetal or centrifugal flow (Ayad et al 2016;Bhatia 2014;Cao et al 2015;Dong and Chu 2016a;Gantar et al 2002;Golovin et al 1989;Iino et al 1980;Karaskiewicz 2013;Lefor et al 2015;Liu et al 2016;…”