scholarly journals Ultrashort Nacelles for Low Fan Pressure Ratio Propulsors

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Andreas Peters ◽  
Zoltán S. Spakovszky ◽  
Wesley K. Lord ◽  
Becky Rose
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Design Tool ◽  
Operating Conditions ◽  
Design Parameters ◽  
Flow Distortion ◽  
Flow Area ◽  
Propulsive Efficiency ◽  
Flow Acceleration ◽  
Fuel Burn

As the propulsor fan pressure ratio (FPR) is decreased for improved fuel burn, reduced emissions and noise, the fan diameter grows and innovative nacelle concepts with short inlets are required to reduce their weight and drag. This paper addresses the uncharted inlet and nacelle design space for low-FPR propulsors where fan and nacelle are more closely coupled than in current turbofan engines. The paper presents an integrated fan–nacelle design framework, combining a spline-based inlet design tool with a fast and reliable body-force-based approach for the fan rotor and stator blade rows to capture the inlet–fan and fan–exhaust interactions and flow distortion at the fan face. The new capability enables parametric studies of characteristic inlet and nacelle design parameters with a short turn-around time. The interaction of the rotor with a region of high streamwise Mach number at the fan face is identified as the key mechanism limiting the design of short inlets. The local increase in Mach number is due to flow acceleration along the inlet internal surface coupled with a reduction in effective flow area. For a candidate short-inlet design with length over diameter ratio L/D = 0.19, the streamwise Mach number at the fan face near the shroud increases by up to 0.16 at cruise and by up to 0.36 at off-design conditions relative to a long-inlet propulsor with L/D = 0.5. As a consequence, the rotor locally operates close to choke resulting in fan efficiency penalties of up to 1.6% at cruise and 3.9% at off-design. For inlets with L/D < 0.25, the benefit from reduced nacelle drag is offset by the reduction in fan efficiency, resulting in propulsive efficiency penalties. Based on a parametric inlet study, the recommended inlet L/D is suggested to be between 0.25 and 0.4. The performance of a candidate short inlet with L/D = 0.25 was assessed using full-annulus unsteady Reynolds-averaged Navier–Stokes (RANS) simulations at critical design and off-design operating conditions. The candidate design maintains the propulsive efficiency of the baseline case and fuel burn benefits are conjectured due to reductions in nacelle weight and drag compared to an aircraft powered by the baseline propulsor.

scholarly journals Ultra-Short Nacelles for Low Fan Pressure Ratio Propulsors

2014 ◽  
Author(s):  
Andreas Peters ◽  
Zoltán S. Spakovszky ◽  
Wesley K. Lord ◽  
Becky Rose
Keyword(s):  
Mach Number ◽  
Pressure Ratio ◽  
Design Tool ◽  
Operating Conditions ◽  
Design Parameters ◽  
Flow Distortion ◽  
Flow Area ◽  
Propulsive Efficiency ◽  
Flow Acceleration ◽  
Fuel Burn

As the propulsor fan pressure ratio (FPR) is decreased for improved fuel burn, reduced emissions and noise, the fan diameter grows and innovative nacelle concepts with short inlets are required to reduce their weight and drag. This paper addresses the uncharted inlet and nacelle design space for low-FPR propulsors where fan and nacelle are more closely coupled than in current turbofan engines. The paper presents an integrated fan-nacelle design framework, combining a spline-based inlet design tool with a fast and reliable body-force-based approach for the fan rotor and stator blade rows to capture the inlet-fan and fan-exhaust interactions and flow distortion at the fan face. The new capability enables parametric studies of characteristic inlet and nacelle design parameters with a short turn-around time. The interaction of the rotor with a region of high streamwise Mach number at the fan face is identified as the key mechanism limiting the design of short inlets. The local increase in Mach number is due to flow acceleration along the inlet internal surface coupled with a reduction in effective flow area. For a candidate short-inlet design with length over diameter ratio L/D = 0.19, the streamwise Mach number at the fan face near the shroud increases by up to 0.16 at cruise and by up to 0.36 at off-design conditions relative to a long-inlet propulsor with L/D = 0.5. As a consequence, the rotor locally operates close to choke resulting in fan efficiency penalties of up to 1.6 % at cruise and 3.9 % at off-design. For inlets with L/D < 0.25, the benefit from reduced nacelle drag is offset by the reduction in fan efficiency, resulting in propulsive efficiency penalties. Based on a parametric inlet study, the recommended inlet L/D is suggested to be between 0.25 and 0.4. The performance of a candidate short inlet with L/D = 0.25 was assessed using full-annulus unsteady RANS simulations at critical design and off-design operating conditions. The candidate design maintains the propulsive efficiency of the baseline case and fuel burn benefits are conjectured due to reductions in nacelle weight and drag compared to an aircraft powered by the baseline propulsor.

scholarly journals Influence of the main operating parameters on the DRPSA process design based on the equilibrium theory

Adsorption ◽  
2020 ◽  
Author(s):  
Ester Rossi ◽  
Giuseppe Storti ◽  
Renato Rota
Keyword(s):  
Pressure Swing Adsorption ◽  
Degrees Of Freedom ◽  
Pressure Ratio ◽  
Complete Separation ◽  
Operating Conditions ◽  
Equilibrium Theory ◽  
Design Parameters ◽  
Reflux Ratio ◽  
Gaseous Mixtures ◽  
Pressure Swing

Abstract Among the adsorption-based separation processes for gaseous mixtures, those exploiting pressure variations, so-called Pressure Swing Adsorption (PSA) processes, are the most popular. In this work, we focus on the specific PSA configuration known as Dual Reflux-Pressure Swing Adsorption (DR-PSA) given its ability to achieve sharp separations. In the case of binary mixtures, an analytical approach based on Equilibrium Theory has been proposed to identify the operating conditions for complete separation under the assumption of linear isotherms. This same approach is not available when the separation is not complete. Accordingly, in this work we study the features of non-complete separations by solving numerically a general DR-PSA model with parameter values suitable to approach equilibrium conditions (no mass transport resistances, no axial mixing, isothermal conditions and no pressure drop), thus reproducing the analytical solution when complete separations are examined. Even for non-complete separations, triangularly shaped regions at constant purity can be identified on a plane whose axes correspond to suitable design parameters. Moreover, we found a general indication on how to select the lateral feed injection position to limit the loss in product purities when complete separation is not established, whatever is the composition of the feeding mixture. Finally, a sensitivity analysis with respect to pressure ratio, light reflux ratio and heavy product flowrate is proposed in order to assess how to recover product purities according to the specific degrees of freedom of a DR-PSA apparatus.

Computational Fluid Dynamics Investigation of Brush Seal Leakage Performance Depending on Geometric Dimensions and Operating Conditions

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Yahya Dogu ◽  
Ahmet S. Bahar ◽  
Mustafa C. Sertçakan ◽  
Altuğ Pişkin ◽  
Ercan Arıcan ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Ratio ◽  
Plate Thickness ◽  
Operating Conditions ◽  
Design Parameters ◽  
Backing Plate ◽  
Brush Seal ◽  
Front Plate ◽  
Brush Seals

Brush seals require custom design and tailoring due to their behavior driven by flow dynamic, which has many interacting design parameters, as well as their location in challenging regions of turbomachinery. Therefore, brush seal technology has not reached a conventional level across the board standard. However, brush seal geometry generally has a somewhat consistent form. Since this consistent form does exist, knowledge of the leakage performance of brush seals depending on specific geometric dimensions and operating conditions is critical and predictable information in the design phase. However, even though there are common facts for some geometric dimensions available to designers, open literature has inadequate quantified information about the effect of brush seal geometric dimensions on leakage. This paper presents a detailed computational fluid dynamics (CFD) investigation quantifying the leakage values for some geometric variables of common brush seal forms functioning in some operating conditions. Analyzed parameters are grouped as follows: axial dimensions, radial dimensions, and operating conditions. The axial dimensions and their ranges are front plate thickness (z1 = 0.040–0.150 in.), distance between front plate and bristle pack (z2 = 0.010–0.050 in.), bristle pack thickness (z3 = 0.020–0.100 in.), and backing plate thickness (z4 = 0.040–0.150 in.). The radial dimensions are backing plate fence height (r1 = 0.020–0.100 in.), front plate fence height (r2 = 0.060–0.400 in.), and bristle free height (r3 = 0.300–0.500 in.). The operating conditions are chosen as clearance (r0 = 0.000–0.020 in.), pressure ratio (Rp = 1.5–3.5), and rotor speed (n = 0–40 krpm). CFD analysis was carried out by employing compressible turbulent flow in 2D axisymmetric coordinate system. The bristle pack was treated as a porous medium for which flow resistance coefficients were calibrated by using literature based test data. Selected dimensional and operational parameters for a common brush seal form were investigated, and their effects on leakage performance were quantified. CFD results show that, in terms of leakage, the dominant geometric dimensions were found to be the bristle pack thickness and the backing plate fence height. It is also clear that physical clearance dominates leakage performance, when compared to the effects of other geometric dimensions. The effects of other parameters on brush seal leakage were also analyzed in a comparative manner.

On a Model of a Pneumatically Actuated Mechanical System

1971 ◽  
Vol 93 (1) ◽  
pp. 211-220 ◽  
Author(s):  
M. Skreiner ◽  
P. Barkan
Keyword(s):  
Differential Equations ◽  
Mechanical System ◽  
Transient Flow ◽  
Pressure Ratio ◽  
Design Tool ◽  
Time Dependent ◽  
Pneumatic System ◽  
Design Parameters ◽  
Strong Nonlinearity ◽  
Linkage Mechanism

A model of a general mechanical system, comprising a pneumatic system coupled to a linkage mechanism, is developed. The dynamic system behavior is studied using the digital computer as a design tool to determine the effect on the performance of changing design parameters. Within practical limitations, models of this kind have been used to achieve optimum design. Novel methods are used to treat the two major components of the system. The pneumatic system is modeled using an equivalent flow area which is a function of the time-dependent pressure ratio. Differential equations used to solve for the transient flow in the reservoir/piping/piston system are derived here. The mechanism driven by the pneumatic system consists of multiple series chains of four-bar linkages. The first- and second-order kinematic ratios required in the dynamics are computed from new explicit expressions derived here. Frictional losses, impact, and flexibility of the mechanism are included in the dynamic model. The nonlinearity of the differential equations arises from: (a) the kinematics, (b) drag forces depending on velocity squared, (c) magnetic forces depending on time squared, and (d) the strong nonlinearity of the time-dependent pneumatic system. The system of equations is solved numerically to obtain the record of pressure, temperature, and leakage in the pneumatic system and the travel of the mechanisms versus time. Good agreement is obtained between the theoretical solution and actual tests.

scholarly journals Efficiency Scaling - Influence of Reynolds and Mach Number on Fan Performance

2021 ◽  
pp. 1-17
Author(s):  
Peter F. Pelz ◽  
Sebastian Saul ◽  
Johannes Brötz
Keyword(s):  
Mach Number ◽  
Standardized Test ◽  
Pressure Ratio ◽  
Reference Method ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Scaling Method ◽  
Scaled Model ◽  
Type Size ◽  
Shaft Power

Abstract The efficiency, pressure ratio and shaft power of a fan depends on type, size, working medium and operating condition. For acceptance tests, a dissimilarity in Reynolds number, Mach number, relative roughness and relative blade tip clearance of the scaled model and prototype is unavoidable. Hence, the efficiency differs between model and prototype. This difference is quantified by scaling methods. This paper presents a validated and physics based, i. e. reliable scaling method for the efficiency, pressure ratio and shaft power of axial and centrifugal fans operating at subsonic conditions. The method is validated using test results gained on standardized test rigs for different fan types, sizes and operating conditions. For all scenarios the presented scaling method provides a much reduced scaling uncertainty compared to the reference method described in ISO 13348.

Conceptual Fan Design for Boundary Layer Ingestion

2019 ◽  
Author(s):  
M. Mennicken ◽  
D. Schoenweitz ◽  
M. Schnoes ◽  
R. Schnell
Keyword(s):  
Boundary Layer ◽  
Mach Number ◽  
Design Methodology ◽  
Design Parameters ◽  
Calibration Data ◽  
Accurate Calculation ◽  
Data Set ◽  
Fuel Burn ◽  
Flow Phenomena ◽  
Inflow Conditions

Abstract Aircraft concepts using boundary layer ingestion (BLI) are promising future flight systems aiming at reduced mission fuel burn. In this scenario the fan operates at inhomogeneous inflow conditions around the circumference. The accurate calculation of the resulting flow phenomena using uRANS approaches is highly time-consuming and therefore not suitable for fan design at early stages of the design process. In this paper, we introduce a throughflow based design methodology for BLI. The methodology includes the detailed design of the annulus geometry, the design of rotor and stator blades as well as the performance assessment in the BLI scenario. The throughflow approach is extended and calibrated to cover major BLI flow physics. The calibration data set consists of 12 fans with different fan pressure ratios (FPR) and meridional Mach numbers. The new design methodology is applied to design three specific fans and the effect of radial FPR is investigated. All designs are verified using 3D CFD uRANS approaches and the results indicate that either ascending or constant radial FPR should be favored. In addition an exploration study is conducted using the design methodology. This study covers 72 fan stages in the parameter space tip speed and meridional Mach number. The results suggest that there is a favorable tuple of design parameters to design a distortion tolerant fan by trading tip speed and meridional Mach number. In the end the newly gained knowledge is transferred to the DLR UHBR fan in order to improve the tolerance to BLI.

A Conceptual Design Study of an Open Rotor Powered Regional Aircraft

2014 ◽  
Author(s):  
Linda Larsson ◽  
Anders Lundbladh ◽  
Tomas Grönstedt
Keyword(s):  
Mach Number ◽  
Aircraft Design ◽  
Design Parameters ◽  
Propulsive Efficiency ◽  
Turbofan Engine ◽  
Turbofan Engines ◽  
Wide Range ◽  
Open Rotor ◽  
The Difference ◽  
Engine Power

Today many of the routes between small to medium sized airports and large hubs are operated by regional aircraft, powered by turboprop or turbofan engines. In the future the open rotor engine might provide an alternative option. The open rotor would combine the possibility of high cruise speed with high propulsive efficiency. Also, since the open rotor essentially is a turboprop with the possibility to fly fast, there is a benefit of high specific range at low cruising speeds, thus giving it a wide range cruise operation. In this paper a regional aircraft for 70 passengers and 3000 km range is studied. The aircraft is evaluated with both a counter rotating open rotor and a turbofan engine. Aircraft design parameters such as wing area and sweep are varied together with engine parameters such as engine power and propeller disc loading. Results show that the open rotor aircraft has a 17.0 % higher specific range at the optimal cruise Mach number compared to the turbofan aircraft. For higher speeds, at Mach 0.78, the difference is reduced to 15.0 %. The long range cruise Mach number is around Mach 0.7 for the open rotor aircraft while for the turbofan aircraft it is slightly higher, around Mach 0.72.

A Comparison between Measured and Computed Flow Fields in a Transonic Compressor Rotor

1980 ◽  
Vol 102 (4) ◽  
pp. 883-889 ◽  
Author(s):  
P. W. McDonald ◽  
C. R. Bolt ◽  
R. J. Dunker ◽  
H. B. Weyer
Keyword(s):  
Mach Number ◽  
Total Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Computational Procedure ◽  
Operating Conditions ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Pressure Profiles

The flow field within the rotor of a transonic axial compressor has been computed and compared to measurements obtained with an advanced laser velocimeter. The compressor was designed for a total pressure ratio of 1.51 at a relative tip Mach number of 1.4. The comparisons are made at 100 percent design speed (20,260 RPM) with pressure ratios corresponding to peak efficiency, near surge, and wide open discharge operating conditions. The computational procedure iterates between a blade-to-blade calculation and an intrablade through flow calculation. Calculated Mach number contours, surface pressure distributions, and exit total pressure profiles are in agreement with the experimental data demonstrating the usefulness of quasi three-dimensional calculations in compressor design.

Preliminary Design Tool for Centrifugal Compressors

2021 ◽  
Author(s):  
Lily Baye-Wallace ◽  
Grant O. Musgrove
Keyword(s):  
Pressure Ratio ◽  
Operating Parameter ◽  
Ideal Gas ◽  
Design Tool ◽  
Design Parameters ◽  
Compressor Design ◽  
Previous Design ◽  
Inlet Conditions ◽  
Total Pressure Ratio ◽  
Design Experience

Abstract Commonly, compressor designs rely on previous machines that can be slightly modified to achieve new operating requirements. In some cases, however, a completely new design is needed because no previous designs are available for the specific operating range of interest. Without a previous design, it is difficult to make initial trade studies of an appropriate impeller diameter, speed, and number of compression stages. While new compressor designs are a common occurrence in applied research applications, conceptual design typically require a point-by-point process to balance the requirements with acceptable design parameters. This can be done manually or through automation to optimize for a specific operating parameter, such as efficiency. The authors are unaware of any tool available that bounds the range of design parameters for a centrifugal compressor stage without applying a point-by-point method. In this work, two common references for conceptual compressor design were cross-checked to develop an Excel-based tool to quickly determine the design space for a given set of compressor requirements. The tool relies on design experience presented by Aungier and Baljé as well as other experience drawn from available literature [1],[2]. The sheet functions from a series of assumptions based within the design experience and requires inputs regarding the desired power, fluid flow rate, and total-to-total pressure ratio, as well as inlet conditions. While the tool currently assumes an ideal gas, future revisions can include calls to REFPROP for a real gas.

On the Optimization of a Geared Fan Intercooled Core Engine Design

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Konstantinos G. Kyprianidis ◽  
Andrew M. Rolt
Keyword(s):  
Fuel Consumption ◽  
Design Space ◽  
Pressure Ratio ◽  
System Level ◽  
Design Parameters ◽  
Customer Requirements ◽  
Blade Height ◽  
Fuel Burn ◽  
Engine Design ◽  
Last Stage

Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption (SFC), as well as the reduction of engine nacelle drag and weight. One alternative design approach to improving SFC is to consider a geared fan combined with an increased overall pressure ratio (OPR) intercooled core performance cycle. Thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to further analyze the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption. The proposed design methodology is capable, with the utilized tool, of exploring the interaction of design criteria and providing critical design insight at engine–aircraft system level. Previous work by the authors focused on understanding the design space for this particular configuration with minimum SFC, engine weight, and mission fuel in mind. This was achieved by means of a parametric analysis, varying several engine design parameters—but only one at a time. The present work attempts to identify “globally” fuel burn optimal values for a set of engine design parameters by varying them all simultaneously. This permits the nonlinear interactions between the parameters to be accounted for. Special attention has been given to the fuel burn impact of the reduced high pressure compressor (HPC) efficiency levels associated with low last stage blade heights. Three fuel optimal designs are considered, based on different assumptions. The results indicate that it is preferable to trade OPR and pressure ratio split exponent, rather than specific thrust, as means of increasing blade height and hence reducing the associated fuel consumption penalties. It is interesting to note that even when considering the effect of HPC last stage blade height on efficiency there is still an equivalently good design at a reduced OPR. This provides evidence that the overall economic optimum could be for a lower OPR cycle. Customer requirements such as take-off distance and time to height play a very important role in determining a fuel optimal engine design. Tougher customer requirements result in bigger and heavier engines that burn more fuel. Higher OPR intercooled engine cycles clearly become more attractive in aircraft applications that require larger engine sizes.

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