Multidisciplinary Assessment of the Control of the Propellers of a Pusher Geared Open Rotor—Part I: Zero-Dimensional Performance Model for Counter-Rotating Propellers

Abstract

Due to their high propulsive efficiency, counter-rotating open rotors (CRORs) have the potential to significantly reduce fuel consumption and emissions relative to conventional high bypass ratio turbofans. However, this novel engine architecture presents many design and operational challenges both at engine and aircraft level. The assessment of the impact of the main low-pressure preliminary design and control parameters of CRORs on mission fuel burn, certification noise, and emissions is necessary at preliminary design stages in order to identify optimum design regions. These assessments may also aid the development process when compromises need to be performed as a consequence of design, operational, or regulatory constraints. The required preliminary design simulation tools should ideally be 0D or 1D (for computational purposes) and should capture the impact of the independent variation of the main low-pressure system design and control variables, such as the number of blades, diameter and rotational speed of each propeller, the spacing between the propellers, and the torque ratio (TR) of the gearbox or the counter-rotating turbine (CRT), among others. From a performance point of view, counter-rotating propellers (CRPs) have historically been modeled as single propellers. Such a performance model does not provide the required flexibility for a detailed design and control study. Part I of this two-part publication presents a novel 0D performance model for CRPs allowing an independent definition of the design and operation of each of the propellers. It is based on the classical low-speed performance model for individual propellers, the interactions between them, and a compressibility correction which is applied to both propellers. The proposed model was verified with publicly available wind tunnel test data from NASA and was judged to be suitable for preliminary design studies of geared and direct drive open rotors. The model has to be further verified with high-speed wind tunnel test data of highly loaded propellers, which was not found in the public domain. In Part II, the novel CRP model is used to produce a performance model of a geared open rotor (GOR) engine with a 10% clipped propeller designed for a 160 PAX and 5700 NM aircraft. This engine model is first used to study the impact of the control of the propellers on the engine specific fuel consumption (SFC). Subsequently, it was integrated in a multidisciplinary simulation platform to study the impact of the control of the propellers on engine weight, certification noise, and NOx emission.

Gradient-like minimization methods for aeroengines diagnosis and control

“…PROOSIS V R is a well-known stateof-the-art tool for advanced simulation of gas turbine engine performances, 33 and provides the TURBO V R library, which includes a complete catalogue of gas turbine components that facilitates the modeling and simulation of virtually any sort of imaginable gas turbine cycle. 34 Both the PROOSIS V R simulation platform and the TURBO V R toolkit have been widely used and extensively validated in studies related to the performances of gas turbine cycles -ranging from the typical current civil turbofan configurations to the most innovative cycle arrangements or even counterrotating open-rotor configurations (see, for instance, Camilleri 35 and Bellocq et al, 36,37 among many others)-which makes the aforementioned tools very suitable for the intended purpose of this research. The complete diagram of the engine being considered for this study is depicted in Figure 1.…”

A Review of Novel and Non-Conventional Propulsion Integrations for Next-Generation Aircraft

“…In refs. [114,115], a multidisciplinary engine simulation The open rotor aims to extremize the UHBR concept, hence providing a further step forward in the improvement of propulsive efficiency (see Figure 21). Furthermore, the removal of the nacelle or fan casing may allow for friction drag and weight reductions, as a huge increase in turbofan size would require too large nacelle structures [112].…”

“…In refs. [114,115], a multidisciplinary engine simulation The envisaged increases in propulsive efficiency bring benefits to the overall engine efficiency (as reported in Equation ( 1)), hence significant reductions in specific fuel consumption and emissions may be expected; therefore, efforts have been put on research and development of the open rotor concept to have a comprehensive and in-depth understanding of its features. In refs.…”

“…In refs. [114,115], a multidisciplinary engine simulation platform has been used to evaluate the performance of a geared counter-rotating open rotor designed for a 160 passenger transport aircraft, flying 5700 nm at a cruise Mach of 0.75. Specific fuel consumption, engine weight, certification noise and NO x emissions have been considered as figures of merit; the references provide a wide frame for the potential performance of this technology, providing trends between rotor design and operations and the consid-ered performance metrics, highlighting the relevant impact of the control of the rotor's rotating speed.…”

Preliminary Design Framework for the Power Gearbox in a Contra-Rotating Open Rotor

“…In the absence of this information, the gear ratio mG can be expressed as a function of an engine-related parameter such as the torque ratio between the propellers (TR) as presented in Eq. (3).…”