Bell Nozzle Research Articles

Controlled flow regime transition in a dual bell nozzle by secondary radial injection

With the ever rising demands for cheaper payload delivery to orbit, dual bell nozzle with a potential theoretical performance gain of up to 10% can represents one of the major ways of advance to achieve the goal. The well-known transition unsteadiness in a dual-bell rocket nozzle represents one of the major concerns for the development of such altitude compensating type nozzle (ACN). The present study proposes and investigates the possibilities of secondary radial injection for flow regime transition control. Present experimental results demonstrate potential effects of secondary injection on transition and re-transition control even with a relatively low secondary injection mass flow rates. Doing so, the transition and retransition process were significantly delayed towards the ideal transition point. In addition, side loads have been found to be greatly decreased or even eliminated.

Experimental investigation of nozzle geometry effect on two-phase nozzle performance through trilateral flash cycle

This paper aims to elucidate the effect of the divergent geometry of a nozzle on its performance by experimentally estimating the force generated by high speed two-phase fluid leaving the nozzle exit. The experiments are carried out by using the nozzles with two diverging profiles of conical and bell and various divergent angles of 6°, 18° and 30° corresponding to the divergent lengths of 45 mm, 17 mm and 12 mm respectively. The nozzles are examined at inlet temperatures of 50 °C and 60 °C for Isopentane as working fluid. The experimental results are indicative of higher values for thrust force and consequently isentropic efficiency by increasing the inlet temperature from 50 °C to 60 °C for all examined nozzles. It is found through the experiments that the maximum efficiency is about 41% with inlet temperature of 60 °C for the bell shape nozzle with the corresponding divergent angle of 6°. Whereas, the 30° conical and bell nozzles have the least force and efficiency. The pressure measurements along the 6° conical and bell nozzles are indicative of a greater pressure drop after the nozzle throat for bell shape nozzle compared to conical nozzle. This paper presents empirical results that can be used in designing efficient nozzles.

Study of expansion ratio on dual bell nozzle of LOX-RP1 engine for replacing the existing bell nozzle to dual bell nozzle

Numerical study was conducted on the LOX-RP1 engine bell nozzle to replace the dual bell nozzle for determining the optimum expansion ratio and greater thrust at sea level. Here base nozzle is a conventional Rao’s TIC nozzle, where throat radius, exit radius, inflection angle and exit angles are 138mm, 826mm, 33° and 8° respectively. The total length of dual bell nozzle and existing bell nozzle are kept same. Numerical analyses were carried out in ANSYS FLUENT software on different dual bell nozzle geometry to evaluate the thrust and expansion ratio. Numerical analysis is performed by two dimensional, axi-symmetric, steady state, pressure based solver with SST k-ω turbulence model at different ambient pressures to recreate the patterns of flow in the nozzle at different nozzle pressure ratio (NPR) and expansion ratio. The profile has made by commercial software SOLID WORKSTM. Numerical simulations and flow separation locations are validated with the experimental data published earlier. It is observed that with area ratio 150 and inflection angle 15° the thrust has increased by 5.46% at sea level and around 10.5% in vacuum, where the increase in exit radius and mass is only 96 mm and 6 kg respectively.

Parametric Output of Penetration Length in De-Laval Nozzle using Computational Fluid Dynamics

A Contour shaped rocket nozzle, commonly known as Bell nozzle, is a more efficient form of a De-Laval nozzle useful for operation at different altitudes resulting in variable pressure ratio across the nozzle. Here the penetration length during the flow is calculated in a De-Laval nozzle using Computational fluid dynamics (CFD). The TOP nozzle] by G.V.R. Rao is modeled and simulated using CFD analysis by varying the divergent half angle of the bell nozzle. The geometry of different divergent angle of the bell nozzle is modeled using MATLAB code. The modeled geometry and mesh of the nozzle is simulated in ANSYS-FLUENT software. The simulation shows the variation in different flow parameter at different divergent half angles. The analysis so far for the same is done in a conical shaped rocket nozzle at the cost of varying the divergent length for changing the divergent half angle of the nozzle. This project simulates bell nozzle with constant divergent length. The simulation model is verified and validated using experimental and computational data at an NPR (Nozzle pressure ratio) of 1000. As the Rao Nozzle is used currently in rocket, missile, and satellite control systems worldwide. This research work to show how the penetration length effect the Mass-Weighted average Mach number in a particular designed bell nozzle with different divergent half angle. Based on the results obtained, the discussion is done about the parameters and the conclusion is given.

Computational and Experimental Testing of Aircraft Bell Nozzle: Technical Note

In order to gain the supersonic and hypersonic speed, the nozzle plays a major role in the aviation industry. Based on the nozzle design, the required mach number can be calculated. In this paper, the convergent divergent bell nozzle which is basically used for the supersonic flow is analysed and designed using CATIA Software. The mesh of the designed nozzle is carried out in ANSA and then analysed using CFD. Different nozzle designs are assessed through of CFD analysis to choose the best performing nozzle that can be manufactured for experiments. For the experimental test Raspberry Pi, pressure sensor and Python coding was developed to test bell nozzle pressure.

Computational Fluid Dynamics Model of Various Types of Rocket Engine Nozzles

The nozzle is an element of the rocket engine in which the potential energy of gases generated during combustion is converted into the kinetic energy of the gas flow. The design parameters of the nozzle have a decisive influence on the ballistic characteristics of the engine. Designing a nozzle assembly is therefore one of the most responsible stages in developing a rocket engine design. The paper presents the results of the simulation of three types of rocket propulsion nozzles. Calculations were made using CFD (Computational Fluid Dynamics) in ANSYS Fluent software. The analyzed types of nozzles differ in shape. The analysis referred to conical nozzle, a bell type nozzle with a conical supersonic part and a bell type nozzle. Calculation results are presented as pressure, velocity, turbulence kinetic energy and eddy viscosity distributions in the longitudinal section. The results show that the cone nozzle generates strong turbulence in the critical section, which negatively affects the flow of the working gas. In the case of a bell nozzle, the transformation of the wall caused the elimination of flow disturbances in the critical section, which reduced the probability of waves that can form before or after the trailing edge. The most sophisticated construction, the bell-type nozzle, allows for maximizing performance without adding extra weight. The bell type nozzle can be used as a starter and auxiliary engine nozzle due to its advantages.

Investigation of flow characteristics inside a dual bell nozzle with and without film cooling

In this study, we perform a two-dimensional axisymmetric simulation to assess the flow characteristics and understand the film cooling process in a dual bell nozzle. The secondary stream with low temperature is injected at three different axial locations on the nozzle wall, and the simulations are carried out to emphasize the impact of injection location (secondary flow) on film cooling of the dual bell nozzle. The cooling effect is demonstrated through the temperature and pressure distributions on the nozzle wall or, in-turn, the separation point movement. Downstream of the injection point, the Mach number and temperature profiles document the mixing of the main flow and secondary flow. The inflection region is observed to be the most promising location for the injection of the secondary flow. We have further investigated the effect of Mach number of the secondary stream. The current study demonstrates that one can control the separation point in a dual bell nozzle with the help of secondary injection (Mach number) so that an optimum amount of thrust can be achieved.

Performance evaluation of a second throat exhaust diffuser with a thrust optimized parabolic nozzle

Abstract In the present study, the experimental analysis of a second-throat exhaust diffuser (STED) performance has been conducted for the high altitude test of a parabolic bell-type nozzle. The diffuser starting performance has been explored considering two different approaches, namely the gradual and instantaneous increase of the nozzle chamber pressure. Also, the influence of pre-evacuating the internal regions of the system on the diffuser starting performance has been studied. Numerical simulations have been carried out to have more physical insight into some test results. It is demonstrated that the non-dimensional hysteresis range in STED starting performance with a bell-type nozzle is up to 4 times larger than that with a conical nozzle. The pre-evacuation of the internal area does not affect the diffuser minimum starting pressure. However, starting the diffuser with pre-evacuation takes 50 to 70 percent less time than without pre-evacuation. Also, it is illustrated that in spite of large differences in minimum starting pressure of STED with conical and bell-type nozzles, the STED breakdown pressure (minimum operating pressure) is independent of nozzle profile. Moreover, it is shown with experimental evidences and numerical analyses that the creation of restricted shock separation (RSS) inside the bell nozzle leads to some unexpected behaviors in STED starting and breakdown behaviors. Finally, it is demonstrated that the instantaneous increase in the nozzle chamber pressure with steeper slope and pre-evacuation of the internal regions can eliminate separation pattern transition from common free shock separation to unwanted RSS.

Characteristics Analysis of Dual Bell Nozzle using Computational Fluid Dynamics

Space exploration and space tourism have now become a raging competition among the developed nations. For this reason, different types of advanced rocket nozzles with prospective privileges are introduced. Altitude adaptive dual bell nozzle will soon replace the conventional nozzles for the first stage rocket launcher. Indeed, this nozzle has auto adaption capability based on altitude. The major feature of a dual bell nozzle is the two bell-shaped contours separated by an inflection point. This nozzle has left rooms for researchers to test different flight conditions and transition characteristics. In this paper, a dual bell nozzle contour has been developed in MATLAB and analysed for different thermodynamic parameters. ANSYS Fluent is used in analysing flow through the nozzle. Shadowgraph imaging technique is used for measuring density gradient and compared it with fluent results. The simulations were performed by using the k-epsilon turbulence model.

Study of Conical Aerospike Nozzles with Base-Bleed and Freestream Effects

Conical aerospike nozzles are advanced rocket nozzles suitable for altitude compensation. A spike nozzle has geometry that resembles a conventional bell nozzle turned inside out. Lack of a solid outer surface ensures the variation of gas expansion to match the prevailing atmospheric pressure at different altitudes. This study focuses on flow characteristics within conical aerospike nozzles with different levels of truncation and flow conditions. Full spike and truncated aerospike nozzles are numerically simulated using two-dimensional axisymmetric and full three-dimensional models. Reynolds-averaged Navier–Stokes equations are solved with the shear stress transport turbulence model. Computational results of 20, 40, and 60% truncated nozzles are studied in comparison. Base bleed is implemented at two different locations of the base in 20% aerospike nozzle. Base bleed is taken as 2% of the inlet mass flow. The freestream effect is applied to 40% aerospike nozzle for validation purpose and 20% aerospike nozzle with different base-bleed cases for evaluation. Comparison of results establishes that the introduction of base bleed assists in compensating performance loss due to truncation, with the location of bleeding playing a major role in performance improvement. Effects of freestream on the base pressure characteristics of the nozzle are also demonstrated in comparison to nozzles without freestream.

듀얼 벨 노즐의 설계 변수에 따른 천이 특성

듀얼 벨 노즐의 설계 변수에 따른 천이 특성

Parametric study of supersonic film cooling in dual bell nozzle for an experimental air–kerosene engine

Numerical analysis is performed on a dual bell nozzle designed for an experimental semi-cryogenic rocket engine application to predict the effect of film injection on nozzle flow characteristics and transitional behavior. Both start-up and high-altitude operation regimes are simulated to predict actual flight conditions of a dual bell nozzle. Coolant is injected at two locations and at different operating conditions to study the effect of various parameters on flow behavior. Changes in shock interaction and shock patterns during startup flow with and without the injection of coolant are analyzed. An empirical relation for conventional nozzles has been applied to determine the transition pressure ratio. Actual transition flow from base to extension nozzle is found to be different from the calculated transition pressure ratio and flow transition occurs early in case of secondary injection. A large reduction in wall temperature is observed with the film flowing along the nozzle wall and it does not have any adverse effect on flow transition. Instead of efficiency, a film cooling effectiveness for high temperature flow is used to understand the effect of coolant temperature on reduction of heat flux and mixing characteristics. Mass flow rate of coolant is seen to have significant effect on mixing and flow separation.

Ramjet Nozzle Analysis for Transport Aircraft Configuration for Sustained Hypersonic Flight

For the past several decades, research dealing with hypersonic flight regimes has been restricted mainly to military applications. Hypersonic transportation could be a possible and affordable solution to travel in the medium term and there is renewed interest from several private organisations for commercial exploitation in this direction. Various combined cycle propulsion configurations have been proposed and the present paper deals with implications for the nozzle component of a ramjet configuration as part of one such combined cycle propulsion configuration. An investigation was undertaken for a method of turbine-based propulsion which enables the hypersonic vehicle to take off under its own power and propel the aircraft under different mission profiles into ramjet operational Mach regimes. The present study details an optimal method of ramjet exhaust expansion to produce sufficient thrust to propel the vehicle into altitudes and Mach regimes where scramjet operation can be initiated. This aspect includes a Computational Fluid Dynamics (CFD)-based geometric study to determine the optimal configuration to provide the best thrust values. The CFD parametric analysis investigated three candidate nozzles and indicated that the dual bell nozzle design produced the highest thrust values when compared to other nozzle geometries. The altitude adaptation study also validated the effectiveness of the nozzle thrust at various altitudes without compromising its thrust-producing capabilities. Computational data were validated against published experimental data, which indicated that the computed values correlated well with the experimental data.

듀얼 벨 노즐과 E-D 노즐을 결합한 한국형발사체의 비추력 증가

듀얼 벨 노즐과 E-D 노즐을 결합한 한국형발사체의 비추력 증가

Experimental and Computational Exploration of Underexpanded Jets from Conical, Bell and Double Parabolic Nozzles

The flow structure of the jet emanating from supersonic nozzle with different profiles at underexpanded condition were investigated systematically. Experiments were carried out on conical, bell and double parabolic nozzle at Nozzle Pressure Ratios (NPR) of 4.5, 5 and 5.5. For the sake of comparison, the divergent length was the same for all the nozzles. Numerical simulations were also conducted in a two dimensional computational domain taking a density-based solver with RANS equations and SST k-ω turbulence model. The experimental and numerical results matched well all NPRs. The shock cell length, potential core length and supersonic core length at different NPRs were determined from experiments and compared to numerical predictions. These values are also compared to the predicted values based on the equations previously developed by researchers. It is observed that there is not much influence in nozzle profiles in the shock cell length, potential core length and supersonic core length.

Design of a double parabolic supersonic nozzle and performance evaluation by experimental and numerical methods

Purpose The purpose of this paper is to design a double parabolic nozzle and to compare the performance with conventional nozzle designs. Design/methodology/approach The throat diameter and divergent length for Conical, Bell and Double Parabolic nozzles were kept same for the sake of comparison. The double parabolic nozzle has been designed in such a way that the maximum slope of the divergent curve is taken as one-third of the Prandtl Meyer (PM) angle. The studies were carried out at Nozzle Pressure Ratio (NPR) of 5 and also at design conditions (NPR = 3.7). Experimental measurements were carried out for all the three nozzle configurations and the performance parameters compared. Numerical simulations were also carried out in a two-dimensional computational domain incorporating density-based solver with RANS equations and SST k-ω turbulence model. Findings The numerical predictions were found to be in reasonable agreement with the measured experimental values. An enhancement in thrust was observed for double parabolic nozzle when compared with that of conical and bell nozzles. Research limitations/implications Even though the present numerical simulations were capable of predicting shock cell parameters reasonably well, shock oscillations were not captured. Practical implications The double parabolic nozzle design has enormous practical importance as a small increase in thrust can result in a significant gain in pay load. Social implications The thrust developed by the double parabolic nozzle is seen to be on the higher side than that of conventional nozzles with better fuel economy. Originality/value The overall performance of the double parabolic nozzle is better than conical and bell nozzles for the same throat diameter and length.

Design and Optimization of Aerospike nozzle using CFD

New rocket designs are being adopted to increase the performance of the current satellite launch vehicles (SLVs). But, the aerospike (or plug) nozzle concept that has been under development since the 1950s is yet to be utilized on a launch platform. Due to its ability to adjust the environment by altering the outer jet boundary, the aerospike nozzle delivers better performance compared to present day bell nozzle. An aerospike nozzle is designed for 20 bar pressure ratio. In order to improve the performance of the aerospike nozzle for various conditions, optimization of the nozzle was carried out for some important design parameters and their performances were studied for cold flow conditions. Initially a model of an aerospike nozzle is created for certain parameters, then the optimization process is carried out for the nozzle (Truncated model & Base bleed model). Optimized model is designed by the software GAMBIT and the flow behaviour is analysed by the Computational Fluid Dynamics (CFD) software called FLUENT. Comparison also takes place between the full length and the optimized models.

팽창비가 고정된 듀얼 벨 노즐의 천이특성에 대한 수치해석 연구

듀얼 벨 노즐은 고도 보정 노즐의 일종으로 일반적인 벨 노즐의 탈설계점에서의 비추력 손실을 최소화할 수 있는 노즐이다. 본 논문에서는 팽창비가 고정된 듀얼 벨 노즐의 천이특성을 파악하기 위하여 전산수치해석을 수행하였다. 주요 설계변수로는 확장부 길이와 변곡각 크기를 선정하였다. 확장부 길이가 증가할수록 천이고도 및 천이지속시간은 증가하였고, 추력계수 감소폭은 감소하였다. 변곡각 크기가 증가할수록 천이고도 및 천이지속시간은 감소하였고, 추력계수 감소폭은 증가하였다. Dual bell nozzle is a type of altitude compensation nozzle, which is a nozzle that minimize the losses of the specific impulse at the off-design point of a typical bell nozzle. In this paper, numerical computations are performed to understand the transition characteristics of dual bell nozzles with fixed expansion ratios. The major design variables are the length of extension and the angle of inflection. As the length of the extension increased, the transition altitude and transition duration increased and the reduction of the thrust coefficient decreased. As the angle of inflection increased, the transition altitude and transition duration decreased and the reduction of the thrust coefficient increased.

Sea-level transitioning dual bell nozzles

A detailed study was conducted to evaluate the impact of sea-level transitioning dual bell nozzles on the payload mass delivered into geostationary transfer orbit by Ariane 5 ECA. For this purpose, a multitude of Vulcain 2 and Vulcain 2.1 nozzle extension contours were designed. The two variable parameters were the position of the wall inflection and the constant wall pressure of the nozzle extension. Accounting for the two variable parameters, an approved analytical method was applied to predict the impact of the dual bell nozzles on the payload mass.

한국형발사체를 기반으로 한 듀얼 벨 노즐의 전산수치해석 기초 결과

한국형발사체를 기반으로 한 듀얼 벨 노즐의 전산수치해석 기초 결과