Experimental Investigation on Combustion Characteristics of Hybrid Rocket Fuels with Multi-Angle Diverging Injector

Injection pattern of the oxidizer injected into the combustion chamber is a significant factor in evaluating the performance of a hybrid rocket. In the hybrid rocket combustion process, oxidizer flows over the solid fuel grain surface, leading to a turbulent diffusion boundary layer formation and the flame is established inside the boundary layer. The heat transfer from flame to the fuel surface leads to pyrolysis of the fuel. The heat fluxes, due to pyrolysis, block the heat transfer further to the fuel surface, thus reducing the fuel regression rate. An attempt has been made in this paper to design and study the effect of the multi-angle diverging injector on the enhancement of the fuel regression rate and combustion efficiency of the hybrid rocket. The designed injector was compared with a shower head injector i.e., axial injector. The fuels used were paraffin wax and polyvinyl chloride (PVC) with gaseous oxygen as oxidizer. The effect of formation of the re-circulation zone and flow velocity were studied numerically by a cold flow simulation using ANSYS-Fluent software. It has been observed that direct impingement of the multi-angle diverging injector produces velocity in three directions, leading to distortion of the boundary layer. An increase of 8% in the average fuel regression rate for PVC fuel grain and 36.14% for paraffin wax fuel grain was observed, as compared to the shower head injector for the same oxidizer mass flow rate. A combustion efficiency increase of 38% and 14% was also observed using multi-angle diverging injector for PVC and paraffin wax fuel grains, respectively. A reduction in sliver and uniform fuel consumption was also observed using the novel multi-angle diverging injector.

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Regression rate performance of paraffin wax and bees wax –Gox with varied grain configuration in a hybrid rocket motor

Aircraft Engineering and Aerospace Technology ◽

10.1108/aeat-02-2021-0051 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Saravanan G. ◽

Shanmugam S. ◽

Veerappan A.R.

Keyword(s):

Mass Flux ◽

Design Methodology ◽

Paraffin Wax ◽

Chamber Pressure ◽

Solid Fuels ◽

Hybrid Rocket ◽

Local Regression ◽

Gaseous Oxygen ◽

Regression Rate ◽

Content Type

Purpose This paper aims to determine the regression rate using wax fuels for three different grain configurations and find a suitable grain port design for hybrid rocket application. Design/methodology/approach The design methodology of this work includes different grain port designs and subsequent selection of solid fuels for a suitable hybrid rocket application. A square, a cylindrical and a five-point star grained were designed and prepared using paraffin and beeswax fuels. They were tested in a laboratory-scale rocket with gaseous oxygen to study the effectiveness of solid fuels on these grain structures. The regression rate by static fire testing of these wax fuels was analyzed. Findings Beeswax performance is better than that of paraffin wax fuel for all three designs, and the five-slotted star fuel port grain attained the best performance. Beeswax fuel attained an average regression rate ≈of 1.35 mm/s as a function of oxidizer mass flux Gox ≈ 111.8 kg/m2 s and for paraffin wax 1.199 mm/s at Gox ≈ 121 kg/m2 s with gaseous oxygen. The local regression rates of fuels increased in the range of 0.93–1.194 mm/s at oxidizer mass flux range of 98–131 kg/m2 s for cylindrical grain, 0.99–1.21 mm/s at oxidizer mass flux range of 96–129 kg/m2s for square grain and 1.12–1.35 mm/s at oxidizer mass flux range of 91–126 kg/m2 s for a star grain. A complete set of the regression rate formulas is obtained for all three-grain designs as a function of oxidizer flux rate. Research limitations/implications The experiment has been performed for a lower chamber pressure up to 10 bar. Originality/value Different grain configurations were designed according to the required dimension of the combustion chamber, injector and exhaust nozzle of the design of a lab-scale hybrid rocket, and input parameters were selected and analyzed.

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Small-scale Gaseous Oxygen Hybrid Rocket Testing Facility Upgrades for Regression Rate and Combustion Efficiency Studies

2018 Joint Propulsion Conference ◽

10.2514/6.2018-4439 ◽

2018 ◽

Cited By ~ 4

Author(s):

Flora S. Mechentel ◽

Brian J. Cantwell

Keyword(s):

Combustion Efficiency ◽

Small Scale ◽

Hybrid Rocket ◽

Gaseous Oxygen ◽

Regression Rate ◽

Testing Facility

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Modeling of gas–surface interface for paraffin-based hybrid rocket fuels in computational fluid dynamics simulations

Progress in Propulsion Physics – Volume 11 ◽

10.1051/eucass/201911003 ◽

2019 ◽

Cited By ~ 4

Author(s):

D. Bianchi ◽

F. Nasuti ◽

D. Delfini

Keyword(s):

Numerical Simulations ◽

Rocket Engine ◽

Combustion Process ◽

Operating Conditions ◽

Hybrid Rocket ◽

Gaseous Oxygen ◽

Regression Rate ◽

Surface Mass ◽

Layer Interface ◽

Inverse Power Law

Numerical simulations of the flowfield in a hybrid rocket engine are carried out with a multispecies chemically reacting Reynolds-averaged Navier–Stokes (RANS) solver which includes detailed gas–surface interaction (GSI) modeling based on surface mass and energy balances. The oxidizer is gaseous oxygen which is homogeneously fed into single-port cylindrical grains. The modeling of GSI already developed and validated for pyrolyzing fuels such as hydroxyl-terminated polybutadiene (HTPB), is extended to the case of liquefying fuels, such as paraffin wax. A simplified two-step global reaction mechanism is considered for the gas-phase chemistry to model the combustion process inside the chamber. Numerical simulations performed at different gas/melt-layer interface temperatures and oxygen mass fluxes show a considerable increase of fuel regression rate, in the range of 3 up to 5 times, for the liquefying fuel with respect to the pyrolyzing one. Results show that the regression rate enhancement is significant only when the gas/melt-layer interface of the liquefying fuel is close to the melting temperature. At increasing gas/melt-layer interface temperatures, the regression rate decreases following an inverse power law and gets close to that of a pyrolyzing fuel for the same operating conditions. Finally, regression rate behavior at varying oxygen mass flux of liquefying fuels is not substantially altered from that of pyrolyzing fuels as the oxidizer flux exponent remains rather constant.

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Study on Effect of Radiation Heat Transfer to Regression Rate of Wax Fuel Hybrid Rocket

2018 Joint Propulsion Conference ◽

10.2514/6.2018-4929 ◽

2018 ◽

Author(s):

Yuto Koinuma ◽

Ichiro Nakagawa

Keyword(s):

Heat Transfer ◽

Radiation Heat Transfer ◽

Hybrid Rocket ◽

Radiation Heat ◽

Regression Rate

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Modified Regression Rate Formula of PMMA Combustion by a Single Plane Impinging Jet

International Journal of Aerospace Engineering ◽

10.1155/2017/6485757 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9

Author(s):

Tsuneyoshi Matsuoka ◽

Kyohei Kamei ◽

Yuji Nakamura ◽

Harunori Nagata

Keyword(s):

Control Volume ◽

Rocket Motor ◽

Displacement Sensor ◽

Pure Oxygen ◽

Hybrid Rocket ◽

Single Plane ◽

Regression Rate ◽

Fuel Surface ◽

Hybrid Rocket Motor ◽

Quenching Distance

A modified regression rate formula for the uppermost stage of CAMUI-type hybrid rocket motor is proposed in this study. Assuming a quasi-steady, one-dimensional, an energy balance against a control volume near the fuel surface is considered. Accordingly, the regression rate formula which can calculate the local regression rate by the quenching distance between the flame and the regression surface is derived. An experimental setup which simulates the combustion phenomenon involved in the uppermost stage of a CAMUI-type hybrid rocket motor was constructed and the burning tests with various flow velocities and impinging distances were performed. A PMMA slab of 20 mm height, 60 mm width, and 20 mm thickness was chosen as a sample specimen and pure oxygen and O2/N2mixture (50/50 vol.%) were employed as the oxidizers. The time-averaged regression rate along the fuel surface was measured by a laser displacement sensor. The quenching distance during the combustion event was also identified from the observation. The comparison between the purely experimental and calculated values showed good agreement, although a large systematic error was expected due to the difficulty in accurately identifying the quenching distance.

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Effect of Bituminous Coal Properties on Heat Transfer Characteristic in the Boiler Furnaces

Heat Transfer, Volume 2 ◽

10.1115/imece2004-59182 ◽

2004 ◽

Cited By ~ 3

Author(s):

B. Chudnovsky ◽

A. Talanker

Keyword(s):

Heat Transfer ◽

Bituminous Coal ◽

Radiation Heat Transfer ◽

Combustion Process ◽

Heat Fluxes ◽

Al2o3 Content ◽

Molar Ratio ◽

Operational Experience ◽

Radiation Heat ◽

Transfer Properties

Over the past years experience has been gained in employing changing types of imported coal. Apart from the proximate analysis this led to development of evaluation criteria regarding the operation of coals. These are criteria numbers obtained from operational experience and criteria numbers used for the characterization of specific operational properties on the basis of special laboratory analyses. The study evaluates the effect of the characteristics of pulverized coal on the furnace fouling and radiation heat transfer. The aim of the study was to access whether fouling and radiation heat transfer could be predicted from coal characteristics. The paper presents the experimental results on the fouling propensity of fifteen coals tested in a 575 MW combustion engineering tangential firing boiler. The results showed that no coals produced a strong molten deposit. In order to rank the fouling propensity and radiation heat transfer properties numerically, we measured the profile of incident heat fluxes, defined furnace exit flue gas temperature and absorbed heat fluxes. The basic molar ratio correlates the fouling propensity. Besides that increasing of SiO2 and Al2O3 content in the ash strongly reduces water wall absorptivity factor. The present work is also concerned with the effect of different bituminous coal on their flame emissivity. Using the radiation properties of flue gases derived from the full scale experiments, we run computational fluid dynamics (CFD) on the combustion process. The known fouling and radiation heat transfer properties enable the prediction of the effect of coal quality on the performance of a specific boiler.

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Conceptual Regenerative Nozzle Cooling Design for a Hydroxyl-Terminated Polybutadiene and Oxygen Hybrid Rocket Engine

Volume 4: 22nd Design for Manufacturing and the Life Cycle Conference; 11th International Conference on Micro- and Nanosystems ◽

10.1115/detc2017-68396 ◽

2017 ◽

Author(s):

Luis R. Robles ◽

Johnny Ho ◽

Bao Nguyen ◽

Geoffrey Wagner ◽

Jeremy Surmi ◽

...

Keyword(s):

Combustion Chamber ◽

High Temperatures ◽

Cooling System ◽

Rocket Engine ◽

Combustion Efficiency ◽

Rocket Engines ◽

Hybrid Rocket ◽

Gaseous Oxygen ◽

Rocket Nozzle ◽

Regenerative Cycle

Regenerative rocket nozzle cooling technology is well developed for liquid fueled rocket engines, but the technology has yet to be widely applied to hybrid rockets. Liquid engines use fuel as coolant, and while the oxidizers typically used in hybrids are not as efficient at conducting heat, the increased renewability of a rocket using regenerative cycle should still make the technology attractive. Due to the high temperatures that permeate throughout a rocket nozzle, most nozzles are predisposed to ablation, supporting the need to implement a nozzle cooling system. This paper presents a proof-of-concept regenerative cooling system for a hybrid engine which uses hydroxyl-terminated polybutadiene (HTPB) as its solid fuel and gaseous oxygen (O2) as its oxidizer, whereby a portion of gaseous oxygen is injected directly into the combustion chamber and another portion is routed up through grooves on the exterior of a copper-chromium nozzle and, afterwards, injected into the combustion chamber. Using O2 as a coolant will significantly lower the temperature of the nozzle which will prevent ablation due to the high temperatures produced by the exhaust. Additional advantages are an increase in combustion efficiency due to the heated O2 being used for combustion and an increased overall efficiency from the regenerative cycle. A computational model is presented, and several experiments are performed using computational fluid dynamics (CFD).

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Effects of Jet Flow Pulsation on Diffusion Flame Performance

International Journal of Recent Technology and Engineering - 2 ◽

10.35940/ijrte.d5031.119420 ◽

2020 ◽

Vol 9 (4) ◽

pp. 444-451

Keyword(s):

Heat Transfer ◽

Heat Release ◽

Heat Transfer Rate ◽

Transfer Rate ◽

Turbulent Flame ◽

Flame Temperature ◽

Combustion Efficiency ◽

Heat Fluxes ◽

Pulsating Flow ◽

Flow Pulsation

The objective of the current research is the experimental investigation of the pulsating flow effects on the combustion performance in terms of the flame temperature distribution, the heat transfer rate, the combustion efficiency and the exhaust gas analysis. The flow pulsation provided through a rotary ball valve in accordance with a variable speed motor arrangement increased the flame temperature fluctuation and the magnitude of heat release. The flow pulsation provides a highly turbulent flame wherein the vortices are enlarged. Increasing Strouhal number [St] of the LPG fuel and air flow increases the time-averaged flame temperature of the pulsating flame up to a saturation level that is dictated by the heat transfer rate enhancement. The maximum average flame temperature is 1263oC at St= 0.041, r= 0 mm and 100 mm from the burner inlet. In addition, increasing the pulsating flow amplitude increases the convection and radiation heat fluxes from the pulsating flame. While increasing the pulsation decreases the exhaust UHC due to increasing the turbulent kinetic energy across the pulsating flame, the exhaust NOx slightly increases due to increasing the heat release rate and the flame temperatures. Pulsation thus enhances the combustion efficiency inside the industrial combustors

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Study of the Local Convective Heat Transfer Downstream a Backward Facing Step for Various Upstream Airflow Conditions and Enlargement Factors

Volume 1 ◽

10.1115/ht-fed2004-56307 ◽

2004 ◽

Author(s):

Didier Saury ◽

Souad Harmand

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Local Heat ◽

Uniform Flow ◽

Heat Fluxes ◽

Thick Wall ◽

Backward Facing Step ◽

Fully Developed Flow ◽

Maximum Heat ◽

Maximum Heat Flux

This paper presents an analyse of the heat transfer coefficient downstream a backward facing step with various upstream airflow conditions: uniform flow outside a laminar boundary layer, uniform flow outside a turbulent boundary layer, and a fully developed flow. The local heat fluxes are obtained from temperature determination by infrared thermography on an assumed thermally thick wall used as boundary conditions of a numerical model. In this article we mainly focus on the maximum heat flux point position determined experimentally and numerically, and also on the influence of the expansion ration on the value of the maximum Nusselt number.

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