Stagnation pressure effect on the supersonic minimum length nozzle design

2019 ◽  
Vol 123 (1265) ◽  
pp. 1013-1031
Author(s):  
T. Zebbiche
Keyword(s):  
High Temperature ◽  
State Equation ◽  
Calculation Model ◽  
Stagnation Pressure ◽  
Molecular Vibration ◽  
Minimum Length ◽  
Stagnation Temperature ◽  
Nozzle Design ◽  
Algebraic Equations ◽  
Axisymmetric Minimum Length Nozzle

ABSTRACTThe aim of this work is to develop a calculation model based on the method of characteristics making it possible to study the effect of the stagnation pressure of the combustion chamber on the 2D and axisymmetric minimum length nozzle design giving a uniform and parallel flow at the exit section. The model is based on the use of the real gas approach. The co-volume and the intermolecular interaction effect are taken into account by the use of the Berthelot state equation. The effect of molecular vibration is considered in our model to evaluate the behaviour of gas at a high temperature. In this case, the stagnation pressure and the stagnation temperature are important parameters in our model. The resolution of the algebraic equations is done by the finite difference corrector predictor algorithm. The validation of the results is controlled by the convergence of the critical section ratios calculated numerically as obtained by the theory. The mass and the thrust are evaluated to improve the efficiency of the nozzle. The comparison is made with the high temperature and perfect gas models. The application is made for air.

Stagnation pressure effect on Prandtl Meyer function for air

2016 ◽  
Vol 231 (2) ◽  
pp. 326-337 ◽  
Author(s):  
Merouane Salhi ◽  
Toufik Zebbiche ◽  
Abderrahmane Mehalem
Keyword(s):  
High Temperature ◽  
Pressure Effect ◽  
Molecular Size ◽  
State Equation ◽  
Stagnation Pressure ◽  
Intermolecular Force ◽  
Perfect Gas ◽  
Real Gas ◽  
New Form ◽  
Made In

When the stagnation pressure of a perfect gas increases, the specific heat and their ratio do not remain constant anymore and start to vary with this pressure. The gas does not stay perfect. Its state equation change and it becomes for a real gas. In this case, the effects of molecular size and intermolecular attraction forces intervene to correct the state equation, the thermodynamic parameters and the value of Prandtl Meyer function. The aim of this work is developing a new form of Prandtl Meyer function based on those assumptions; and determining the effect of stagnation pressure on this function. With the assumptions that Berthelot’s state equation accounts for molecular size and intermolecular force effects, expressions are developed for analysing the supersonic flow for thermally and calorically imperfect gas lower than the dissociation molecules threshold. The supersonic parameters depend directly on the stagnation parameters of the combustion chamber. The application is for air. A computation of error was made in this case to give a limit of the perfect gas and the high temperature models compared to the real gas model.

Performance improvement of supersonic nozzles design using a high-temperature model

2019 ◽  
Vol 233 (13) ◽  
pp. 4895-4910
Author(s):  
Walid Hamaidia ◽  
Toufik Zebbiche ◽  
Mohamed Sellam ◽  
Abderrazak Allali
Keyword(s):  
High Temperature ◽  
Minimum Length ◽  
Algebraic Equations ◽  
Thrust Coefficient ◽  
Supersonic Nozzles ◽  
Specific Heats ◽  
Numerical Resolution ◽  
Aerodynamic Performances ◽  
Exit Mach Number ◽  
Comparison Of The Results

The aim of this paper is to discuss the development of new contours of axisymmetric supersonic nozzles giving a uniform and parallel flow at the exit section, to improve the aerodynamic performances compared to the minimum length nozzle, by increasing the exit Mach number and the thrust coefficient, and by reduction of the nozzle's mass, while holding the same throat section between the two nozzles. The new nozzle is named the best performance nozzle. Its form contains a cylindrical central body and an external wall for the flow redress. The study is done at high temperature, lower than the dissociation threshold of the molecules. The variation of the specific heats with the temperature is considered. The design is made by the method of characteristics. The predictor-corrector algorithm is used to make the numerical resolution of the obtained nonlinear algebraic equations. The validation of results is made by the convergence of the numerical critical sections ratio with that given by the theory. The comparison of the results is made with the minimum length nozzle since it is currently used in the aerospace propulsion. The design depends on M E, T0, y body, y*, and the mesh generation. The application is done with air. A computational fluid dynamics verification for the under nozzle expressed regime has shown that a flow separation with the wall is observed because of the side-loads, which are reduced for this new nozzle compared to the minimum length nozzle.

A New Intermittent Aspirated Probe for the Measurement of Stagnation Quantities in High Temperature Gases

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Michela Massini ◽  
Robert J. Miller ◽  
Howard P. Hodson
Keyword(s):  
High Temperature ◽  
Mass Flow ◽  
Flow Rate ◽  
Stagnation Pressure ◽  
Stagnation Temperature ◽  
Measuring Device ◽  
Second Mode ◽  
Total Temperature ◽  
Flow Through ◽  
Temperature And Pressure

This paper presents the design, manufacture, and testing of a new probe for the measurement of temperature and pressure in engine environments. The probe consists of a choked nozzle located in the flow and a system downstream including a cooler, a flow measuring device, and a valve. It operates in two modes: In the first mode the valve is open, the probe is aspirated, and the nozzle is choked. The mass flow through the probe is measured using instrumentation placed downstream of the cooler, so that it does not have contact with the hot flow. In the second mode, the valve is closed, and the stagnation pressure is measured using the same instrumentation downstream the cooler. The total temperature is computed as a derived variable from the measurements of stagnation pressure and mass flow rate. There are a number of advantages of the probe over existing methods of temperature measurement. The measurement inaccuracy due to conduction and radiation errors and calibration drift found in thermocouples is significantly reduced; it can measure both stagnation temperature and pressure, halving the instrumentation costs; it has no wiring or transducer in the sensor head; the system can self-calibrate while located within an engine. This paper describes the design of a probe for use in engine environments. The probe prototype is tested up to 900 K and is shown to have an accuracy of ±6 K.

A Novel Technique for Measuring Stagnation Quantities and Gas Composition in High Temperature Flows

2010 ◽  
Author(s):  
Michela Massini ◽  
Robert J. Miller ◽  
Howard P. Hodson ◽  
Nick Collings
Keyword(s):  
High Temperature ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Stagnation Pressure ◽  
Temperature Measurements ◽  
Stagnation Temperature ◽  
Gas Composition ◽  
Reference Measurements

A new probe has been developed to measure the time averaged stagnation temperature, stagnation pressure and gas composition. This probe can be used in the high temperature regions of gas turbines, including downstream of the combustor and in the first stages of the high pressure turbines, as well as in other environments. The principal benefits of the new probe are that it overcomes the limitations of the standard methods that are used to measure temperature in high temperature environments and that it replaces three separate probes, for the three quantities mentioned above, with one single probe. A novel method of measuring temperature is used, which improves upon the accuracy of thermocouples and increases the temperature operating range. The probe consists of a choked nozzle placed in the hot flow at the point of interest. The working principle is based on the theory that for a choked nozzle, there is a fixed relationship between the stagnation quantities, the gas characteristics and the mass flow rate through the nozzle. The probe has an aspirated phase, where the gas composition and the mass flow rate are measured and a stagnated phase, where the stagnation pressure is measured. The stagnation temperature is determined from the above quantities. The operating principle has been proven valid through laboratory and rig tests. The probe has been successfully tested in a Rolls-Royce Viper engine up to 1000K and 2 bar and in a combustor rig up to 1800K and 4 bars. Measurements of stagnation temperature, stagnation pressure and gas compositions for these tests are presented in the paper and are compared with reference measurements. The accuracy of stagnation pressure and gas composition measurements is equal to the accuracy achievable with techniques that are commonly used in gas turbines. The estimated achievable accuracy of the aspirated probe in terms of temperature measurements is ±0.6%, i.e. ±10K at 1800K, which improves upon the accuracy of temperature measurements performed with standard thermocouples at the same temperatures, the uncertainty of which could be as high as ±2%.

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