# Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experimental Setup

_{0}up to 20 MPa, stagnation temperature T

_{0}up to 800 K, mass flow rate of working gas up to 5 kg/s, and test duration from 1 to 10 s. For conducting the test fires described below using LSM gasification in a GG, the MAF was modified by replacing its settling chamber, nozzle, and test section by a flow-through GG according to the direct-connect scheme (Figure 2) and installing a vacuum tank downstream of GG to remove gasification products. In test fires, GGs with hydrogen- or pyro-charge-assisted ignition were used.

#### 2.1. Gas Generator with Hydrogen-Assisted Ignition

_{1}. Downstream of the insert, a provision is made for a fire heater operating on combustion of hydrogen to increase the temperature of the incoming air up to ~1700 K for a short time (~0.5 s). The hydrogen–air mixture is ignited with a spark plug. The mass of hydrogen used for ignition was less than 2 g. The inner cavity of the fire heater is partly covered with a heat-insulating insert. Polypropylene (PP) was used as LSM as it is gasified without formation of liquid phase (condensate). As will be shown later in this article, the approach developed herein was based on gas dynamic relationships that are not generally applicable to the two-phase flows containing liquid or solid particles. A PP test sample was placed in the combustion chamber of the GG in the form of 16 blocks with a diameter of 80 mm and a length of 25 mm connected in series (Figure 4). Each block had 61 holes with a diameter of 4 mm.

_{2}= 20 mm was placed downstream of the combustion chamber in the GG. To measure the total pressure and temperature of the outgoing gas mixture, pressure sensor and thermocouples were installed upstream of the nozzle. The outgoing gas mixture was directed to the vacuum tank through a tube attached to the nozzle.

#### 2.2. Gas Generator with Pyro-Charge-Assisted Ignition

_{1}. A ring-shaped pyro-charge weighing 36 g was placed in the cavity around the channel. The charge can be activated at a given time when voltage is applied to initiator on a command from synchronization system. Upon ignition, charge burning increases the temperature of the passing air. If the calorific value of charge material is ~2.0 MJ/kg then about 72-kJ energy is released during charge combustion. During 0.1–0.15 s of charge combustion, 22.5 g of air enters the channel. With full use of the supplied heat, the air at the GG inlet must be heated to about 2400 K. However, the actual air temperature in the experiments reaches a value of 900–1100 K only, thus indicating large heat losses into the walls of the ignition device. Upstream of the PP sample, a provision was made for the ports for measuring the total pressure ${P}_{0\mathrm{in}}$ and the stagnation temperature ${T}_{0\mathrm{in}}$ of the incoming air flow.

#### 2.3. Measurements

## 3. Data Processing Procedure

#### 3.1. Mass Flow Rate at GG Inlet

^{1/2}for the air flow. The value of ${A}_{1}^{*}$ was selected to fit the ${P}_{0}\left(t\right)$ curve predicted by Equation (1) with the pressure drop in the storage vessel measured by a pressure sensor. After ${A}_{1}^{*}$ was determined, the air mass flow rate was calculated from the relationship:

^{1/2}, ${A}_{1}^{*}$ = 20.83 mm

^{2}, $B$ = 0.002554 1/s, and ${G}_{\mathrm{in}}\left(0\right)$ = 0.181 kg/s. At time $t$ = 0.8 s, the air supply valve is opened, and the pressure in the air storage vessel starts to decrease (Figure 6a). At time $t$ = 5.3 s, the valve is closed, and air supply is stopped. The dashed curve shows the approximation of the measured pressure curve according to Equation (1). On the one hand, this equation was used to determine the value of $B$, and then the function ${G}_{\mathrm{in}}\left(t\right)$ was determined according to Equation (2) (Figure 6b). Thereafter, the mean mass flow rate of air during test fire was calculated. According to estimates [26], this method allows determining the air mass flow rate with an error of less than 1.0%. On the other hand, the mean mass flow rate of air was calculated based on the difference in the mass of air in the storage vessel before and after test fire (taking the change in temperature into account) based on the measured values of initial and final pressure and test duration. The difference between the values of mean mass flow rates thus obtained does not exceed 0.1%.

#### 3.2. Mass Flow Rate at GG Outlet

^{1/2}. This variation leads to a change in the calculated mass flow rate of gas mixture by 30%. Noteworthy, when the pressure varies from 0.1 to 1.0 MPa, the value of ${\mu}_{2}$ changes by less than 3%. The present authors’ experience in processing experimental data shows that coefficient ${\mu}_{2}$ can be considered constant with a good accuracy (see below).

#### 3.3. Mass Flow Rate of Gasification Products

^{1/2}for pure air, see Figure 7) and use Equations (5) and (6) for determining the first approximation of ${G}_{\mathrm{pp}}\left(t\right)$, that is ${G}_{\mathrm{pp}}^{\prime}\left(t\right)$, and a value of $\phi $. This value of $\phi $ can be further considered as a correction factor for calculating the corrected mass flow rate of gasification products, ${G}_{\mathrm{pp}}^{\u2033}\left(t\right)$, using the relationship:

^{1/2}for this test case. The corresponding curves for ${G}_{\mathrm{out}}\left(t\right)$ and ${G}_{\mathrm{pp}}\left(t\right)$ are represented in Figure 8a,b. To avoid iterations, let us assume for ${\mu}_{2}$ a constant value of 0.0404 (kg·K/J)

^{1/2}corresponding to pure air. The curves ${G}_{\mathrm{out}}^{\prime}\left(t\right)$ and ${G}_{\mathrm{pp}}^{\prime}\left(t\right)$ obtained for such a value of ${\mu}_{2}$ are represented in Figure 8a,b. Accordingly, the time integral of the mass flow rate of gasification products along curve ${G}_{\mathrm{pp}}^{\prime}\left(t\right)$ in Figure 8b (i.e., the integral in the right-hand side of Equation (5)) exceeds the value of $({W}_{1}-{W}_{2})$ determined by sample weighing (shaded area in Figure 8a) by a factor of 1.62. Thus, coefficient $\phi $ in Equation (5) takes a value of 1/1.62 = 0.617. The corrected mass flow rate ${G}_{\mathrm{pp}}^{\u2033}\left(t\right)$ was then calculated from Equation (7) and represented by curve ${G}_{\mathrm{pp}}^{\u2033}\left(t\right)$ in Figure 8b. Now, one can see a fairly accurate agreement between curves ${G}_{\mathrm{pp}}^{\u2033}\left(t\right)$ and ${G}_{\mathrm{pp}}\left(t\right)$ in Figure 8b. The difference between these curves is represented by curve ${G}_{\mathrm{pp}}^{\u2033}\left(t\right)-{G}_{\mathrm{pp}}\left(t\right)$ in Figure 8b. The relative difference between ${G}_{\mathrm{pp}}^{\u2033}\left(t\right)$ and ${G}_{\mathrm{pp}}\left(t\right)$ is less than 8%.

## 4. Typical Test Fires

#### 4.1. Test Fires with Hydrogen-Assisted Ignition

#### 4.2. Test Fires with Pyro-Charge-Assisted Ignition

## 5. Results and Discussion

#### 5.1. Yield of Gasification Products with Hydrogen-Assisted Ignition

#### 5.2. Yield of Gasification Products with Pyro-Charge-Assisted Ignition

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Sutton, G.P.; Biblarz, O. Rocket Propulsion Elements, 9th ed.; Wiley: New York, NY, USA, 2017. [Google Scholar]
- Freesmeier, J.J.; Butler, P.B. Analysis of a Hybrid Dual-Combustion-Chamber Solid-Propellant Gas Generator. J. Propuls. Power
**1999**, 15, 552–561. [Google Scholar] [CrossRef] - Karabeyoglu, A.; Zilliac, G.; Cantwell, B.J.; DeZilwa, S.; Castellucci, P. Scale-up Tests of High Regression Rate Paraffin-Based Hybrid Rocket Fuels. J. Propuls. Power
**2004**, 20, 1037–1045. [Google Scholar] [CrossRef] - Galfetti, L.; Merotto, L.; Boiocchi, M.; Maggi, F.; DeLuca, L.T. Experimental Investigation of Paraffin-Based Fuels for Hybrid Rocket Propulsion. In Progress in Propulsion Physics; DeLuca, L., Bonnal, C., Haidn, O., Frolov, S., Eds.; EUCASS Advances in Aerospace Sciences Book Series; EDP Sciences–Torus Press: Les Ulis, France, 2013; Volume 4, pp. 59–74. [Google Scholar] [CrossRef][Green Version]
- Mazzetti, A.; Merotto, L.; Pinarello, G. Paraffin-Based Hybrid Rocket Engines Applications: A Review and a Market Perspective. Acta Astronaut.
**2016**, 126, 286–297. [Google Scholar] [CrossRef] - Wada, Y.; Kawabata, Y.; Kato, R.; Kato, N.; Hori, K. Observation of Combustion Behavior of Low Melting Temperature Fuel for a Hybrid Rocket Using Double Slab Motor. Int. J. Energetic Mater. Chem. Propuls.
**2016**, 15, 351–369. [Google Scholar] [CrossRef] - Lee, D.; Lee, C. Hybrid Gas Generator for a Staged Hybrid Rocket Engine. J. Propuls. Power
**2017**, 33, 204–212. [Google Scholar] [CrossRef] - Wang, L.; Wu, Z.; Chi, H.; Liu, C.; Tao, H.; Wang, Q. Numerical and Experimental Study on the Solid-Fuel Scramjet Combustor. J. Propuls. Power
**2015**, 31, 685–693. [Google Scholar] [CrossRef] - Zvegintsev, V.I.; Fedorychev, A.V.; Zhesterev, D.V.; Mishkin, I.R.; Frolov, S.M. Gasification of Low-Melting Hydrocarbon Materials in High-Temperature Gas Flow. Combust. Explos.
**2019**, 12, 108–116. [Google Scholar] [CrossRef] - Frolov, S.M.; Shamshin, I.O.; Kazachenko, M.V.; Aksenov, V.S.; Bilera, I.V.; Ivanov, V.S.; Zvegintsev, V.I. Polyethylene Pyrolysis Products: Their Detonability in Air and Applicability to Solid-Fuel Detonation Ramjets. Energies
**2021**, 14, 820. [Google Scholar] [CrossRef] - Schmitt, R.G.; Butler, P.B.; Freesmeier, J.J. Performance and CO Production of a Non-Azide Airbag Propellant in a Pre-Pressurized Gas Generator. Combust. Sci. Technol.
**1997**, 122, 305–330. [Google Scholar] [CrossRef] - Wu, W.T.; Hsieh, W.H.; Huang, C.H.; Wang, C.H. Theoretical Simulation of Combustion and Inflation Processes of Two-Stage Airbag Inflators. Combust. Sci. Technol.
**2005**, 177, 383–412. [Google Scholar] [CrossRef] - Cheng, C.; Zhang, X.; Wang, C.; Wang, L. Numerical Investigation on Cooling Performance of Filter in a Pyrotechnic Gas Generator. Def. Technol.
**2021**, 17, 343–351. [Google Scholar] [CrossRef] - Schmid, H.; Eisenreich, N.; Baier, A.; Neutz, J.; Schröter, D.; Weiser, V. Gas Generator Development for Fire Protection Purpose. Propellants Explos. Pyrotech.
**1999**, 24, 144–148. [Google Scholar] [CrossRef] - Mahinpey, N.; Gomez, A. Review of Gasification Fundamentals and New Findings: Reactors, Feedstock, and Kinetic Studies. Chem. Eng. Sci.
**2016**, 148, 14–31. [Google Scholar] [CrossRef] - Salaudeen, S.A.; Arku, P.; Dutta, A. Gasification of Plastic Solid Waste and Competitive Technologies. In Plastics to Energy; Al-Salem, S.M., Ed.; William Andrew Publishing: Norwich, NY, USA, 2019; pp. 269–293. [Google Scholar] [CrossRef]
- Salgansky, E.A.; Lutsenko, N.A. Effect of Solid Fuel Characteristics on Operating Conditions of Low-Temperature Gas Generator for High-Speed Flying Vehicle. Aerosp. Sci. Technol.
**2021**, 109, 106420. [Google Scholar] [CrossRef] - Rashkovskiy, S.A.; Yakush, S.E. Numerical Simulation of Low-Melting Temperature Solid Fuel Regression in Hybrid Rocket Engines. Acta Astronaut.
**2020**, 176, 710–716. [Google Scholar] [CrossRef] - DeLuca, L.T.; Galfetti, L.; Colombo, G.; Maggi, F.; Bandera, A.; Boiocchi, M.; Gariani, G.; Merotto, L.; Paravan, C.; Reina, A. Time-Resolved Burning of Solid Fuels for Hybrid Rocket Propulsion. In Progress in Propulsion Physics; DeLuca, L., Bonnal, C., Haidn, O., Frolov, S., Eds.; EUCASS Advances in Aerospace Sciences Book Series; EDP Sciences–Torus Press: Les Ulis, France, 2011; Volume 2, pp. 405–426. [Google Scholar] [CrossRef][Green Version]
- Shiplyuk, A.N.; Zvegintsev, V.I.; Frolov, S.M.; Vnuchkov, D.A.; Kiseleva, T.A.; Kislovsky, V.A.; Lukashevich, S.V.; Melnikov, A.Y.; Nalivaychenko, D.G. Gasification of Low-Melting Hydrocarbon Material in the Airflow Heated by Hydrogen Combustion. Int. J. Hydrogen Energy
**2020**, 45, 9098–9112. [Google Scholar] [CrossRef] - Shiplyuk, A.N.; Zvegintsev, V.I.; Frolov, S.M.; Vnuchkov, D.A.; Kislovsky, V.A.; Kiseleva, N.A.; Lukashevich, S.V.; Melnikov, A.Y.; Nalivaychenko, D.G. Gasification of Low-Melting Fuel in a High-Temperature Flow of Inert Gas. J. Propuls. Power
**2021**, 37, 20–28. [Google Scholar] [CrossRef] - Arkhipov, V.A.; Basalaev, S.A.; Kuznetsov, V.T.; Poryazov, V.A.; Fedorychev, A.V. Modeling of Ignition and Combustion of Boron-Containing Solid Propellants. Combust. Explos. Shock. Waves
**2021**, 57, 308–313. [Google Scholar] [CrossRef] - Zarko, V.; Perov, V.; Kiskin, A.; Nalivaichenko, D. Microwave Resonator Method for Measuring Transient Mass Gasification Rate of Condensed Systems. Acta Astronaut.
**2019**, 158, 272–276. [Google Scholar] [CrossRef] - Evans, B.N.; Favorito, A.; Kuo, K. Study of Solid Fuel Burning-Rate Enhancement Behavior in an X-ray Translucent Hybrid Rocket Motor. In AIAA Paper 2005-3909, Proceedings of the 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Tucson, Arizona, USA, 10–13 July 2005; The American Institute of Aeronautics and Astronautics: Reston, VA, USA, 2012. [Google Scholar] [CrossRef]
- Saito, Y.; Kamps, L.T.; Komizu, K.; Bianchi, D.; Nasuti, F.; Nagata, H. The accuracy of reconstruction techniques for determining hybrid rocket fuel regression rate. In AIAA Paper 2018-4923, AIAA Propulsion and Energy Forum, Proceedings of the Joint Propulsion Conference, Cincinnati, OH, USA, 9–11 July 2018; The American Institute of Aeronautics and Astronautics: Reston, VA, USA, 2018. [Google Scholar] [CrossRef]
- Zvegintsev, V.I. Short-Duration Gas-Dynamic Facilities. Part 1. Facilities for Scientific Research; Parallel Publ.: Novosibirsk, Russia, 2014; (In Russian). ISBN 978-5-98901-169-8. [Google Scholar]
- Trusov, B.G. Modeling of Chemical and Phase Equilibria at High Temperatures “Astra 4”; Bauman State Technical University Publ.: Moscow, Russia, 1991. [Google Scholar]

**Figure 6.**Example of determining the air mass flow rate G

_{in}(t) in one of test fires (test fire #4, see below): (

**a**) time history of pressure in the air storage vessel (solid curve) and its approximation (dashed curve) according to Equation (1), and (

**b**) time history of the air mass flow rate according to Equation (2).

**Figure 7.**Coefficient ${\mu}_{2}$ for calculating gas mass flow rate at GG outlet depending on the PP-to-air mass ratio at 1 MPa.

**Figure 8.**Calculated time histories of total gas mass flow rates (

**a**) and mass flow rate of gasification products (

**b**) for test fire #9.

**Figure 9.**Time histories of (

**a**) pressure and (

**b**) temperature at PP sample inlet and outlet in test fires #1 to #3.

**Figure 10.**Time histories of (

**a**) pressure and (

**b**) temperature at PP sample inlet and outlet in test fires #4 and #5.

**Figure 11.**Time histories of (

**a**) pressure and (

**b**) temperature at PP sample inlet and outlet in test fires #6 to #9.

**Figure 12.**Calculated mass flow rates G

_{in}(t), G

_{out}(t), and G

_{out}(t) − G

_{in}(t) in test fires #1 to #3.

**Figure 13.**Calculated mass flow rates G

_{in}(t), G

_{out}(t), and G

_{out}(t) − G

_{in}(t) in test fires #4 and #5.

**Figure 14.**Calculated mass flow rates G

_{in}(t), G

_{out}(t), and G

_{out}(t) − G

_{in}(t) in test fires #6 to #9.

Test Fire | 2 | 3 |
---|---|---|

Start of ignition, s | 1.53 | 1.53 |

End of ignition, s | 2.05 | 2.05 |

Air mass flow rate, g/s | 232.7 | 232.1 |

Mass of air, g | 121.0 | 120.7 |

Mass flow rate of gasification products, g/s | 120.8 | 106.9 |

Yield of gasification products, g | 62.8 | 55.6 |

Ratio of mass flow rates of air and gasification products | 1.93 | 2.17 |

Start of combustion, s | 2.05 | 2.05 |

End of combustion, s | 5.40 | 5.20 |

Air mass flow rate, g/s | 211.3 | 219.9 |

Mass of air, g | 708.0 | 692.8 |

Mass flow rate of gasification products, g/s | 82.1 | 72.2 |

Yield of gasification products, g | 274.9 | 227.4 |

Ratio of mass flow rates of air and gasification products | 2.58 | 3.05 |

Total during test fire: | ||

Air mass flow rate, g/s | 214.2 | 221.7 |

Mass of air, g | 829.0 | 813.5 |

Mass flow rate of gasification products, g/s | 87.2 | 77.1 |

Yield of gasification products, g | 337.6 | 283.0 |

Ratio of mass flow rates of air and gasification products | 2.46 | 2.87 |

Test Fire | 6 | 7 | 8 | 9 |
---|---|---|---|---|

Start of combustion, s | 1.30 | 1.25 | 1.33 | 1.32 |

End of combustion, s | 5.10 | 5.37 | 5.40 | 5.48 |

Air mass flow rate, g/s | 166.4 | 159.79 | 156.4 | 124.8 |

Mass of air, g | 632.4 | 658.0 | 636.4 | 519.3 |

Mass flow rate of gasification products, g/s | 71.2 | 67.0 | 65.0 | 43.0 |

Yield of gasification products, g | 270.7 | 276.2 | 264.7 | 179.0 |

Ratio of mass flow rates of air and gasification products | 2.34 | 2.38 | 2.40 | 2.90 |

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Vnuchkov, D.A.; Zvegintsev, V.I.; Nalivaichenko, D.G.; Frolov, S.M.
Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow. *Energies* **2022**, *15*, 5765.
https://doi.org/10.3390/en15165765

**AMA Style**

Vnuchkov DA, Zvegintsev VI, Nalivaichenko DG, Frolov SM.
Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow. *Energies*. 2022; 15(16):5765.
https://doi.org/10.3390/en15165765

**Chicago/Turabian Style**

Vnuchkov, Dmitry A., Valery I. Zvegintsev, Denis G. Nalivaichenko, and Sergey M. Frolov.
2022. "Measurement of Instantaneous Mass Flow Rate of Polypropylene Gasification Products in Airflow" *Energies* 15, no. 16: 5765.
https://doi.org/10.3390/en15165765